Monitoring the critically ill surgical patient RONALD L. HOLLIDAY,* MD; PETER J. DoRIs,t MD, M SC, FRC5[C]
Critically ill surgical patients account for approximately half the patients in an active multidisciplinary critical care unit. Hypovolemia and sepsis are common in such patients and affect a number of organ systems. Monitoring these systems provides therapeutically relevant information that may decrease morbidity and Improve patient survival. Circulatory hemodynamics may be assessed by direct measurement of the arterial blood pressure, central venous and pulmonary artery pressure monitoring and cardiac output determination; the data thus obtained are valuable in guiding fluid replacement in the hypovolemic individual. The respiratory status may be assessed by bedside spirometry and measurement of arterial blood gas tensions to gauge pulmonary function and the need for assisted ventilation. Renal dysfunction is common in such patients; careful analysis of both urine and blood may identify prerenal as opposed to renal and postrenal factors. Monitoring of the gastrointestinal tract, especially for hemorrhage, is important. Finally, careful attention to nutritional status and provision of adequate protein and energy intake by mouth or by vein is a vital component of the optimal care of these patients. Les patients de chirurgie dont l'etat est critique comptent pour environ Ia moitie des patients d'une unit6 multidisciplinaire de soins critiques. L'hypovolemie et Ia sepsie sont frequentes chez ces patients et affectent plusieurs systemes organiques. La surveillance de ces systemes procure une information pertinente au traitement qui est susceptible de diminuer Ia morbidite et d'ameliorer Ia survie du patient. Lhemodynamique circulatoire peut .tre evaluee par Ia mesure directe de Ia tension arterielle, Ia surveillance des pressions veineuse centrale et arterielle pulmonaire et Ia determination du debit cardiaque; les donnees ainsi obtenues sont utiles aux ajustements de Ia recharge liquidienne chez le sujet hypovolemique. L'etat respiratoire peut .tre verifie par spirometrie au chevet du malade et par Ia mesure des pressions gazeuses arterielles afin d'evaluer Ia fonction respiratoire et le besoin de ventilation assistee. Le dysfonctionnement renal est frequent chez ces patients; l'analyse minutieuse de l'urine et du sang peut identifier les facteurs prerenaux par opposition aux facteurs renaux et postrenaux. La surveillance du tractus gastrointestinal, specialement pour lapparition dune hemorragie digestive, est important. Finalement, une attention minutieuse portee a letat nutritionnel et a lassurance dun apport prot6inlque et energetique adequat par voie orale ou veineuse est une composante vitale des soins optimaux pour ces patients.
Critically ill surgical patients ac- cardiothoracic and major abdocount for approximately half of the minal operations, which involve patients in an active multidisci- fluid shifts and acid-base and plinary intensive care unit. Many metabolic derangements, necessitate surgical patients are admitted to intensive care. Finally, patients such a unit because of pre-existing with critical surgical illnesses that problems, such as cardiac or pul- involve multiple traumatic injuries, monary disease, that may be ag- peritonitis and burns are at risk of gravated by an operation. Certain multisystem failure and have comcomplicated procedures, such as plicated resuscitative needs that are best met in an intensive care From *the critical care/trauma unit, unit. Victoria Hospital and the department Intensive monitoring makes many of surgery, University of Western contributions to the care of these Ontario, London, and tihe department patients. First, it helps to minimize of surgery, Queen's University and the frequency of complications Hotel Dieu Hospital, Kingston, Ont. during and following an operation Reprint requests to: Dr. Ronald L. by uncovering correctable problems Holliday, Critical care/trauma unit, Victoria Hospital, 375 South St., early in their development, thereby London, Ont. N6A 4G5 facilitating their rapid resolution. *-For prescribing information see page 953
Second, it provides diagnostic insights into the complicated illnesses that may develop in such patients. Finally, it guides the administration of therapy. Elsewhere in this symposium Pietak and Teasdale address the problem of the high-risk patient undergoing surgical procedures and indicate what procedures are likely to require additional monitoring during anesthesia. Our paper aims to define the problems that develop in the critically ill surgical patient and to outline strategies for their assessment and therapy. Through problem-solving encounters with such patients the clinician develops a better understanding of the pathophysiology of shock as it relates to both hypovolemia and sepsis. Hypovolemia
The traumatized patient may experience hypovolemic shock; this occurs because of loss of whole blood, plasma or electrolyte-containing fluid. in the past 15 years much research has been undertaken to define the altered physiology in hypovolemic shock and its subsequent effects on basic cellular function. Shires and coworkers1'2 demonstrated a loss of "functional extracellular volume" in prolonged hemorrhagic shock, and further work has elucidated the nature of this loss. Hypovolemia, from whatever cause, leads to altered cell membrane function,3 with a loss of normal electrical activity. Subsequently a shift of intracellular and extracellular electrolytes occurs, so that sodium passes in and potassium passes out, with resultant cellular swelling.4'5 There is attendant alteration in the subcellular organelles, with mitochondrial swelling, and thereafter a loss of protein synthesis. The initial biochemical response is an increase in the sodium-potassium adenosine triphosphatase activity in an attempt to maintain cellular integrity.
CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
931
Eventually, however, the energy sources are dissipated, with increasing accumulation of inorganic phosphates. Intracellular breakdown of lysosomes occurs, and potent hydrolytic enzymes are released into the cell and ultimately into the organism as a whole to produce further damage.6'7 While most of these pathophysiologic changes in hypovolemic shock have been demonstrated in research animals, the observations have been extended to humans.8 It is obvious that if sufficient cellular changes occur there will eventually be organ failure. The critically ill human tolerates the failure of one organ system surprisingly well and that of two organ systems with some difficulty, but the failure of three organ systems nearly always proves fatal.
Peripheral vasodilation requires an tient has transcended traditional increased cardiac output to keep methods of assessment such as pace with the metabolic demands. blood pressure, pulse and temperThe increased vascular capacitance ature measurement. The increasing secondary to vasodilation necessi- sophistication of monitoring makes tates the administration of large personal contact with the patient volumes of fluid, which is best more difficult. However, frequent done with the aid of hemodynamic observation and physical contact monitoring so as to avoid cardio- between physician and patient repulmonary overload. Thus, the pa- main fundamental tenets in the care tient with septic shock presents of such individuals and must not more than a simple perfusion prob- be forgotten. Periodic inspection of lem, and treatment of the low blood wounds, incisions, drainage and pressure alone is inadequate. A catheter sites and monitoring lines hypodynamic phase of septic shock remains an integral part of daily exists, and its presence usually re- care. Despite these reservations, flects concomitant hypovolemia. monitoring of the hemodynamic Those caring for critically ill surgi- status of such individuals may be cal patients should be alert to the vital in providing optimal care." Arterial blood pressure: Blood possibility of latent sepsis. Prompt detection of otherwise unexplained pressure measurement by sphygmoalterations in urine output, respira- manometry can be inaccurate, tory rate, temperature, the senso- especially in the hypovolemic parium, cardiac rhythm and acid- tient.14 This has led to direct intrabase balance, and the appearance arterial monitoring via the radial, Sepsis of bruising, bleeding or leukocy- brachial, axillary, femoral, dorsalis Although sepsis may be the tosis can permit early diagnosis of pedis and superficial temporal reason for admission to an inten- sepsis and effective therapy. Dis- arteries. Either a percutaneous apsive care area, it is more often a seminated intravascular coagula- proach or surgical cutdown may be complication of another critical ill- tion commonly complicates septic used, and appropriate precautions ness. Sepsis is related in part to the shock and should be anticipated by should be taken to ensure an misuse of drugs such as antibiotics a search for coagulation abnormal- aseptic technique and avoidance of that allow a resistant organism to ities as well as split products of distal circulatory impairment. A flourish or a nosocomial infection fibrin degradation.11 functioning flush system is required to develop. Infection may also be to ensure patency. Since complicafacilitated by the presence of Monitoring organ system function tions from arterial lines may 15 tracheostomy tubes, drainage sites in critical surgical illness occur, the indications for such and monitoring devices such as monitoring must be carefully asAlthough hemodynamic assess- sessed. Intra-arterial monitoring intravenous and urinary tract catheters, which permit the entry of ment is an important component of provides not only accurate blood organisms. Many patients are at in- the sophisticated monitoring re- pressure measurement, but also creased risk because their underly- quired for the critically ill surgical access for arterial blood sampling. ing disease has led to anergy, with patient, monitoring of all major Central venous pressure: Moniserious reduction in the usual systems is necessary for optimal toring of the central venous preshost defence mechanisms. The care.12 The key to success rests with sure (CVP) was initiated in 1931 use of immunosuppressive, cortico- the team caring for the patient but was not popularized until the steroid or anticancer drugs also more than with the equipment. The late 1960s.'0 Today the Swanintensive care nurse is an indis- Ganz catheter is used with increaspredisposes to sepsis. pensable component of the team; ing frequency, but valuable informaThe past 10 years have witnessed important advances in the under- she must be knowledgeable, moti- tion can still be obtained with standing of septic shock.9'10 The vated and enthusiastic, and must proper CVP monitoring provided hyperdynamic phase of sepsis is remain "the compleat monitor". A there is no significant associated characterized by a high cardiac plan must be developed for se- cardiopulmonary disease. The CVP output, a wide pulse pressure and quential introduction of monitoring catheter is ideally inserted into the an inappropriately high urine out- that involves all systems vital for superior vena cava for measurement put. In all likelihood the problem life. It should include a routine for of the right ventricular filling presbegins with an endotoxin-immune dealing with the large volume of sure (RVFP). The RVFP, however, complex phenomenon that produces data generated in these circum- is not a measure of the blood volcellular damage. Subsequent changes stances; this permits sequential re- ume but, rather, varies directly with in capillary permeability occur view of the information and a trend it and with vascular tone as well as either because of this interaction or analysis of the monitored indices. reflecting right heart competence.17 secondary to the release of vasoAlthough the normal range of the active substances such as brady- Circulatory hemodynamics CVP is stated to be approximately kinin, serotonin and histamine. Monitoring the critically ill pa- 5 to 12 cm H20, it is serial 932 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
measurements rather than absolute values that are most helpful in directing patient care. Hence, the response of the CVP to a bolus fluid challenge in a patient with hypovolemia may provide useful information. However, pitfalls in interpretation occur in a number of situations that are common in critically ill patients - for example, increased intrathoracic pressure, alterations in right ventricular compliance, pulmonary embolism and increased pulmonary vascular resistance." In addition, when there is underlying disease of the left ventricle the CVP may be an unreliable guide to the adequacy of the central blood volume and cardiac performance; this is discussed in detail elsewhere in this symposium. Swan-Ganz balloon flotation catheter: The limitations of CVP measurement as a means of hemodynamic monitoring were among the stimuli that led to the development of the Swan-Ganz catheter. With this catheter various pressures, including right atrial, pulmonary artery and pulmonary capillary wedge, can be measured.19 Recent modifications permit simple and reproducible measurement of the cardiac output by the thermal dilution technique. A catheter placed in the pulmonary artery allows true mixed venous blood sampling and measurement of both venous oxygen tension and venous oxygen saturation at this site. Simultaneous sampling of arterial and mixed venous blood permits calculation of the arterialvenous oxygen difference; narrowing of this difference may indicate a high cardiac output and complicating sepsis, whereas a widened difference highlights a diminished cardiac output and indicates a need for efforts to augment it." With this kind of information one can make other calculations of oxygen transport and delivery, some of which are discussed later in this article and elsewhere in the symposium. The experience of one of us (R.L.H.) with the Swan-Ganz catheter constitutes 34 insertions in 120 general surgical patients admitted to a critical care unit in 1977. The indications for monitoring were multiple injuries requiring the administration of large volumes
of fluid, postoperative complications such as sepsis and hypotension, and preoperative observation in high-risk patients. Predictably the mortality in this group was high, reflecting the fact that invasive monitoring was reserved for the sickest patients. Pitfalls in hemodynamic monitoring have been previously discussed in this symposium, but it is worth emphasizing that the measurements must always be interpreted in the light of the clinical situation. In summary, valuable information concerning the hemodynamic status of the critically ill surgical patient may be obtained that will influence the choice of therapy and guide subsequent decisions. Respiratory status Respiratory problems are an important cause of disability and death in the critically ill surgical patient." It is therefore vital to assess the respiratory status preoperatively and ascertain which patients are at increased risk by reason of important underlying cardiopulmonary disease. Once identified, such patients should be followed with careful preoperative and perioperative respiratory assessment. This is especially true following abdominal and thoracic surgical procedures, during which significant alterations in respiratory function occur. These alterations include an increase in the ratio of dead space to tidal volume (Vd/Vt), a reduced functional residual capacity (FRC) and an attendant increase in ventilatory rate, with an accompanying increase in the overall work of breathing. Should progressive respiratory failure develop, it is mandatory to consider what correctable underlying factors exist, such as atelectasis, pneumothorax, latent sepsis, pulmonary edema and pulmonary emboli. The adult respiratory distress syndrome is known to occur in surgical patients, and the many etiologic factors in this syndrome are well detailed elsewhere." Respiratory monitoring should begin with a complete clinical examination, examination of the sputum by Gram-staining and culture when indicated, and chest roentgenography. Among the other
methods available for monitoring, analysis of blood gases remains one of the most important. This may be done with a sample of capillary blood in a patient with good perfusion, but direct arterial sampling is required in a patient with hypovolemia or vasoconstriction. The alveolar-arterial difference in oxygen tension (AaDol), as derived in the appendix, provides a useful gauge of respiratory function by evaluating the relation between the arterial tensions of oxygen and carbon dioxide, thereby giving more meaningful data than would either measurement alone. Alveolar ventilation can be accurately assessed from the carbon dioxide tension in the absence of metabolic alkalosis; if it rises above 55 mm Hg assisted ventilation should be considered. Likewise, if the AaDo2 exceeds 50 to 60 mm Hg while the patient is breathing room air, or 350 or 450 mm Hg while the patient is breathing 100% oxygen, ventilatory assistance may be required. The decision to begin assisted ventilation must always be made in the light of the clinical situation, with particular regard to the work of breathing and the patient's prior pulmonary status. Thus, mechanical ventilation may be desirable in some instances even though the aforementioned blood gas criteria are absent; conversely, despite the presence of these criteria assisted ventilation may prove unnecessary. Bedside spirometry may be useful in assessing the ventilatory and mechanical aspects of pulmonary function. Preoperatively a reduced forced expiratory volume during the first second of exhalation, a decreased maximum midexpiratory flow, an increased residual volume or an increased Vd/Vt may indicate important chronic obstructive lung disease. Compliance, which is expressed as the volume of air that can move in the lungs with each unit of pressure change, is another factor affecting ventilation. Diminished lung volume, reduced or absent pulmonary surfactant production and increased lung water content are all factors that may be operative in the adult respiratory distress syndrome and may contribute to reduced lung compliance. It is vital
CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
933
to assess the pulmonary compliance when a patient is undergoing mechanical ventilation; effective compliance (Ce.) can be estimated by assessing the relation between flow or tidal volume (TV) and the peak inflation pressure. Thus, C.fr = TV! peak inspiratory pressure If there is decreased compliance (that is, an increased resistance to flow) such that a greater peak inflation pressure is required for ventilation, one should be alert to the possibility of respiratory-induced pneumothorax or airway obstruction. Certain assumptions are involved in the calculation of many of the indices of respiratory function we have outlined. The influence of temperature, cardiac output and metabolic status should be considered. Hypothermia, alkalosis and a reduced erythrocyte 2,3-diphosphoglycerate content all decrease the availability of oxygen to the tissues by shifting the oxyhemoglobin dissociation curve up and to the left. Laboratory indices of pulmonary function are of greatest help if their trends are followed over time. Renal function
Oliguria (a urine output of less than 400 ml/24 h) is most commonly a secondary phenomenon of hypovolemia in the critically ill surgical patient. In addition to clinical manifestations, hypovolemia may be reflected in the quality of the urine produced; typically there is a reduced sodium concentration (less than 10 to 20 mmol/l) and an increased osmolarity. As well, the urine/plasma creatinine ratio is increased (to more than 20). By contrast, a direct renal cause for the oliguria would be expected to result in a higher urine sodium concentration (greater than 40 mmol/l), a reduced urine osmolarity and a lower urine/plasma creatinine ratio, as well as some abnormality in the urine sediment. Urinary tract obstruction must also be considered in the critically ill surgical patient, especially when there is anuria. Polyuria may complicate the recovery from acute oliguric renal failure, and careful attention to
water and electrolyte balance is required. In addition, the catabolic state of some critically ill surgical patients may result in a high osmotic load, with an attendant increase in urine output (so-called high output or nonoliguric renal failure.). This syndrome is characterized by the excretion of large volumes of iso-osmotic urine as well as by rising blood urea nitrogen (BUN) and serum creatinine concentrations. Sepsis may also be associated with polyuria that appears to be related to tubular dysfunction, with the excretion of urine of a high sodium concentration. A disproportionate rise in the BUN level over the serum creatinine level should alert the physician to a prerenal cause for azotemia, such as hypovolemia, upper gastrointestinal tract hemorrhage or excessive tissue breakdown. The surgical patient with hyponatremia, hemodilution and a high urine osmolarity relative to that of plasma should be suspected of having inappropriate secretion of antidiuretic hormone. In the critically ill surgical patient there may be a variety of causes for this, including drug administration, general anesthesia, positive-pressure ventilation, pneumonia and head trauma. First-line therapy should include water restriction and removal of any correctable cause. A detailed discussion of fluid and electrolyte disturbances as well as acid-base problems in the critically ill surgical patient is beyond the scope of this presentation. As previously noted, however, trauma may lead to capillary leakage, with progressive interstitial edema and a depleted intravascular volume, and subsequently an increase in the secretion of aldosterone and antidiuretic hormone. Electrolyte and acid-base disturbances must be interpreted in an integrated fashion, with a knowledge of whether they represent acute or pre-existing abnormalities and how an alteration of one will affect the others. Gastrointestinal function Alterations in the gastrointestinal system may be a serious associated problem for the critically ill surgical patient. Traditional methods of assessing the gastrointestinal tract include careful abdominal palpa-
934 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
tion and auscultation, measurement of abdominal girth, a search for gastrointestinal tract bleeding via a nasogastric tube and rectal examination, paracentesis and examination of the plain abdominal roentgenogram made with the patient either upright or in the decubitus position. Paralytic ileus is a common accompaniment of critical illness. It is usually gastric in origin unless there is associated peritonitis. Electrolyte disturbances, particularly hypokalemia, may either initiate the ileus or potentiate it and prolong recovery. A nasogastric tube is usually indicated for gastric decompression when ileus is present, and it may also be helpful in assessing the presence of upper gastrointestinal tract bleeding. Certain problems exist, however, with the introduction of a nasogastric tube, including continued gastroesophageal reflux, with associated esophagitis, nasopharyngeal and gastroesophageal erosions, and infection. The tube incites copious gastrointestinal secretion, and its continuing removal causes metabolic alkalosis and electrolyte imbalance. These complications are generally reversible with removal of the tube. Gastrointestinal tract bleeding, particularly from "stress ulceration", is an ever-present threat in the critically ill patient. The entire gastrointestinal tract is at risk, however, and monitoring of the gastric secretions and stool for the presence of blood may alert the physician to this problem. Appropriate early prophylactic measures include continual use of antacids to keep the gastric pH above 4. Administration of cimetidine as a bolus or as a continuous infusion has also been suggested. Recent work suggests that the gastric mucosa in critically ill humans may leak protein prior to erythrocytes, and this may offer another avenue for monitoring (D.P. Girvan and B. Taylor: personal communication, 1978). Liver dysfunction may also be present in a critically ill surgical patient, although it may be subclinical, with subtle alterations in serum bilirubin and liver enzyme concentrations appearing prior to overt clinical signs such as jaundice.24
Nutritional status There have been rapid strides in the understanding of nutrition in the surgical patient over the past 10 years. Identification of nutritional deficiency prior to major elective surgery is important since careful attention to its correction may improve the postoperative course and the chances for survival. There are a number of patterns of nutritional abnormalities in critically ill surgical patients, but excessive catabolism, with destruction of lean body mass (muscle protein), is the common denominator. This response, while initially protective by supplying additional substrate for metabolism, eventually becomes self-defeating because of excessive tissue breakdown; the subsequent muscle weakness may contribute to hypoventilation and difficulty in weaning the patient from the respirator. Diminished muscular activity in the legs may be incriminated in the frequent occurrence of venous thrombosis and pulmonary embolism. Precise monitoring of these nutritional changes is difficult since weight gain or loss in the critically ill may be an inadequate gauge owing to the rapid changes in fluid volume. Hypoalbuminemia is common and is particularly marked in the burn patient, but it may be a late manifestation of malnutrition. Nitrogen balance studies are difficult to perform and often give inaccurate results; perhaps measurement of the urea concentration in a 24-hour collection of urine is the best available bedside tool provided there is not coexistent renal failure. When a careful review of the premorbid nutritional status and body mass, basal metabolic rate and daily nutritional requirements is added to these estimations, a comprehensive plan for replacing needed protein and energy may be evolved. It is prudent to assume that every critically ill surgical patient is likely to become nutritionally depleted unless adequate energy, vitamins and protein are provided by mouth or by vein. If the oral route cannot be used, total parenteral nutrition may be advisable.25 The patient requiring such therapy is usually severely ill and likely to remain so for an extended period,
and has a gastrointestinal tract fistula with peritonitis, extensive bowel resection or inflammation, or both, severe continuing pancreatitis or extensive burns. There may be an initial "hypercatabolic phase", during which there are tremendous energy requirements that have been provoked by the stress of the operation and by inadequate peripheral perfusion or oxygenation, or both. After this stress has passed and homeostasis has been restored, the patient may enter a "stress catabolic phase", during which organ failure, persistent sepsis or slowly resolving organ dysfunction is present and the daily metabolic demands may exceed 13 x 1 0. kJ (roughly 3000 Cal). A final "starvation catabolic phase" indicates that organ failure has been reversed and sepsis eliminated; effective nutritional support during this phase may rapidly lead to a return to anabolism.'6 Total parenteral nutrition for such patients should never consist of glucose infusions alone, but rather should consist of solutions of glucose and fat supplemented with essential amino acids, vitamins and trace elements. The energy! nitrogen ratio may vary, depending on the catabolic phase judged to be present. Thus, this form of therapy requires careful monitoring and anticipation of complications, which may include local and systemic sepsis, especially fungal, hyperosmolar diuresis, electrolyte imbalance and hyperglycemia. Summary
An overview of the pathophysiological disturbances present in critically ill surgical patients has been presented. Adequate monitoring of such patients requires assessment of several organ systems to detect organ dysfunction and guide its correction. References 1. SHIRES T, BROWN FT, CANIZARO PC,
et al: Distributional changes in extracellular fluid during acute hemorrhagic shock. Surg Forum 11: 115, 1960 2. SHIRES T, CARRICO CJ, COLN D:
Role of the extracellular fluid in shock. mt Anesthesiol Gun 2: 435, 1964
3. SHIRES
GT,
CUNNINGHAM
JN,
BAKER CRF, et al: Alterations in cellular membrane function during hemorrhagic shock in primates. Ann Surg 176: 288, 1972 4. TRUNKEY
D, HOLCROFT J, CAR-
PENTER MA: Calcium flux during hemorrhagic shock in baboons. J Trauma 16: 633, 1976 5. HALJAMXE H: Effects of hemorrhagic shock and treatment with hypothermia in the potassium content and transport of single mammalian skeletal muscle cells. Acta Pliysiol Scand 78: 189, 1970 6. MELA LM, MILLER LD, NICHOLAS
GG: Influence of cellular acidosis and altered action concentrations on shock-induced mitochondrial damage. Surgery 72: 102, 1972 7. BELL ML, HERMAN AH, SMITH EE,
et al: Role of lysosomal instability in the development of refractory shock. Surgery 70: 341, 1971 8. CUNNINGHAM IN JR, CARTER NW, RECTOR FC JR, et al: Resting trans-
membrane potential difference of skeletal muscle in normal sllbjects and severely ill patients. J Clin Invest 50: 49, 1971 9. Wmisow AJ, LOEB HS, RAHIMTOOLA SH, et al: Hemodynamic studies and results of therapy in 50 patients with bacteremic shock. Am J Med 54: 421, 1973 10. WElL MH, NISHIJIMA H: Cardiac output, in bacterial shock. Am J Med
64: 920, 1978 11. RAPAPORT 5: Defibration syndromes, in Hematology, WILLIAMS WJ, BEUTLER E, ERSLER AJ, et al (eds), McGraw, New York, 1977, p 1454 12. GREENBERG AG, TESKIN GW: Monitoring in the recovery room and surgical intensive care unit, in
Monitoring in A nesthesia, SAIDMAN LG, SMITH NT (eds), Wiley, New
York, 1978, p 221 13. SWAN HJC: Role of hemodynamic monitoring in the management of the critically ill. Crit Care Med 3:
83, 1975 14. COHN JN: Blood pressure reassessment in shock. Mechanism of inaccuracy in auscultatory and palpatory methods. JAMA 199: 972,
1967 15. BEDFORD RF, WOLLMAN H: Complications of percutaneous radialartery cannulation: an objective prospective study in man. Anes-
thesiology 38: 228, 1973 16. KNOPP R, DAILEY RH: Central venous cannulation and pressure monitoring. JACEP 6: 358, 1977 17. GUYTON AC, JONE CE: Central venous pressure: physiological significance and clinical implications.
Am Heart J 86: 431, 1973 18. BRISMAN R, PARKS LC, BENSON DW: Pitfalls in the clinical use of central venous pressure. A rcli Surg
95: 902, 1967
CMA JOURNAL/OCTOBER 6, 1979/VOL 121
935
SEPTR. DS * now available in convenient, smaller-size tablet * broad-spectrum activity provides bactericidal coverage against all these respiratory pathogens: ii, influenzae, including many ampicillinresistant strains; 0. pneumoniae: Klebsiella: .tr.ptococcus . and viridans; .i.pAiyijcoccus aureus and albus * discourages development of resistance * achieves rapid, high blood levels; significant levels in lung tissue and sputum * well tolerated by most patients * Septra is also available in licorice-flavored suspension. well accepted by children
* Septra2 (Trimethoprim + Sulfamethoxazole) l9. Summary INDICATIUS: Indicated for the following infections when caused by susceptible organisms: UPPER AND LOWER RESPIRATORY TRACT INFECTIONS-particularly chronic bronchitis and acute and chronic of if is media. URINARY TRACT INFECTIONS-acute, recurrent and chronic. GENITAL TRACT INFECTIONS-uncomplicated gonococcal urethritis. GASTROINTESTINAL TRACT INFECTIONS. SKIN AND SOFT TISSUE INFECTIONS. SEPTRA is also indicated in the treatment of infants and children with a diagnosis of Pneumocysf is carinii pneumonitis, especially if they are immunosuppressed. SEPTRA is not indicated in infections caused by Pseudomonas, Mycoplasma or viruses. This drug has not yet been fully evaluated in streptococcal infections. CONTRAINOICATIONS: Patients with evidence of marked liver parenchymel damage, blond dyscrasias, known hypersensitivity to trimethoprim or sulfonamides, marked renal impairment where repeated serum assays cannot be carried out, premature or newborn babies during the first few weeks of life. For the time being SEPTRA is contrair'dicafed during pregnancy. ADVERSE REACTIONS: Most frequent: nausea; vomiting; gastric intolerance; and rash. Less frequent: diarrhea; constipation; flatulence; anorexia; pyrosis; gastritis; gastroenteritis; urticaria; headache; and liver changes (abnormal elevations in alkaline phosphatase and serum transaminase). Occasionally reported: glossitis; oliguria; hematuria; tremor; vertigo; alopecia; and elevated BUN, NPN, and serum creatinine. Hematological changes occurring particularly in the elderly, are mostly fransient and reversible (primarily, neutropenia and thrombocytopenia; less frequently, leukopenia, aplastic or hemolytic anemia, agranulocytosis, and bone marrow depression). PRECAUTIONS: As with other sulfonamide preparations, critical appraisal of benefit versus risk should be made in patients with liver damage, renal damage, urinary obstruction, blood dyscrasias, allergies or bronchial asthma. The possibility of a superinfection with a non-sensitive organism should be borne in mind. DOSAGE AND ADMINISTRATION: Adults and children over 12 years. Standard dosage: 2 Septra tablets or 1 Septra OS tablet twice daily. Minimum dosage and dosage for long-term treatment: 1 Septra tablet or Y2 Septra OS tablet twice daily. Maximum dosage: Overwhelming infections: 3 Septra tablets or 1/2 Septra OS tablets twice daily. Uncomplicated gonorrhea: 2 Septra tablets or 1 Septra OS tablet four times daily for 2 days. Pneumu.,ystis carinii pneumonitis: 20 mg/kg/day trimethoprim and kI0 mg/kg/day sulfamethoxazole in four divided doses for 14 days. Children 12 years and underi Young children should receive a dose according to biological age: Children under 2 years: 2.5 ml of suspension twice daily. Children 2 to 5 years: 2.5-5 ml of suspension twice daily. Children 6 to 12 years: 5-10 ml of suspension twice daily. tIn children this corresponds to an approximate dose of 6 mg trimethoprim/kg body weight/day, pIus 30 mg sulfamethoxazole/kg body weight/day, divided into two equal doses. DOSAGE FORMS SEPTRA OS TABLETS, each containing 160 mg trimethoprim and 800 mg sultamethoxazole, and coded WELLCOME 02C. Bottles of 50 and 250. SEPTRA TABLETS, each containing 80 mg trimethoprim and 400 mg sulfamethoxazole, and coded WEILCOME Y2B. Bottles 01100 and 500, and unit dose packs of 100. SEPTRA PEDIATRIC TABLETS, each containing 20 mg trimethoprim and 100 mg sulfamethoxazole, and ceded WELLCOME H4B. Bottles of 100. SEPTRA PEDIATRIC SUSPENSION, each teaspoonful (5 ml) containing 40mg trimethoprim and 200 mg sulfamethoxazole. Bottles of 100 and 400 ml. Product monegraph available on request. 2Trade Mark W-7013
.I i.llcome Medical Division BUrroUghS V.llcome Ltd.
19. PACE NL: A critique of flowdirected pulmonary arterial catheterization. Anesthesiology 47: 455, 1977 20. WILSON RF, GIBSON D: The use of arterial-central venous oxygen differences to calculate cardiac output and oxygen consumption in critically ill surgical patients. Surgery 84: 362, 1978 21. DOWNS JB: Respiratory failure. Part 1 - the adult. Curr Probi Anesth Grit Care Med 1: 4, 1978
23. ANDERSON RJ, LINAS SL, BERNS AS, et al: Nonoliguric acute renal failure. N Engi j Med 296: 1134, 1977
22. PONTOPPIDAN H, GEFFIN B, Low-
Surgical Patient: Medical, Surgical and Anesthetic Management, SIEGEL
ENSTEIN E: Acute respiratory failure in the adult (first of three parts). N Engi J Med 287: 690, 1972
24. CHAMPION HR, JONES RT, TRUMP
BF, et al: A clinicopathologic study of hepatic dysfunction following shock. Surg Gynecol Obste*. 142: 657, 1976 25. MOORE FD, BRENNAN ME: Intravenous feeding. N Engi J Med 287:
862, 1972 26. BORDER JR, LADUCA J, SEIBEL R: Nutritional support of the surgical
patient, in The Aged and High Risk
JH, CHODOFF PD (eds), Grune, New York, 1976, p 239
Appendix - Derivation of alveolar-arterial difference in oxygen tension AaDo2 = PAo2 - Pao2 = [(PB - PH2o)FIo2 - Paco?] - Pao, where AaDo2 = alveolar-arterial difference in oxygen tension PAo2 = alveolar oxygen tension Pao2 = arterial oxygen tension PH = barometric pressure PH2O = water vapour pressure F1o2 = fraction of inspired oxygen Paco2 = arterial carbon dioxide tension For example, with an F1o2 of 100% at sea level, a Pao2 of 350 mm Hg and a Pco2 of 40 mm Hg, AaDo2 = [(760 - 47)1.0 -- 40] - 350 = 323 Assuming a normal cardiac output, this may be simplified for a patient with previously normal pulmonary function at sea level breathing room air: AaDo2 = 145 - (Pao2 + Paco2) The normal range of the AaDo2 for a healthy young adult is 10 to 20 mm Hg.
continued from page 900 1978 DIRECTORY OF ON-GOING RESEARCH IN SMOKING AND HEALTH. Compiled by Informatics Inc., Rockville, Md. 433 Pp. US Department of Health, Education, and Welfare, Public Health Service, Office on Smoking and Health, Rockville, Maryland, 1979. Price not stated, paperbound DISORDERS OF STRESS AND THEIR MANAGEMENT BY YOGA. A Study of Neurohumoral Response. K.N. Udupa. 205 pp. IlIust. Banaras Hindu University, Varanasi, India, 1978. Price not stated, paperbound THE DOCTOR AND THE LAW. A Practical Handbook for the Canadian Physician. H.E. Emson. 235 pp. The Macmillan Company of Canada Limited, Toronto, 1979. $9.95, paperbound. ISBN 0-7705-1786-2 THE EFFECTS OF PSYCHOTHERAPY. Volume 1. Michael J. Lambert. 158 pp. Eden Press Inc., Montreal, 1979. $20. ISBN 0-443-02030-2 ENTEROSTOMAL THERAPY: DEVELOPING INSTITUTIONAL AND COMMUNITY PROGRAMS. Linda Gross and Zeila Bailey. 221 pp. IlIust. Nursing Resources, Inc., Wakefield, Massachu-
936 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
setts, 1979. Price not stated, paperbound. ISBN 0-913654-49-3 ENZYMES IN CARDIOLOGY. Diagnosis and Research. Edited by David J. Hearse and Joel de Leiris. 586 pp. Illust. John Wiley & Sons, New York, 1979. $70. ISBN 0-471-99724-2 FRONTIERS OF GASTROINTESTINAL RESEARCH. Vol. 5. Gastrointestinal Cancer: Advances in Diagnostic Techniques and Therapy. Selected Papers of the International Conference on Gastrointestinal Cancer, Tel Aviv, November 1977. Edited by P. Rosen, S. Eidelman and T. Gilat. 225 pp. IlIust. S. Karger AG, Basel, 1979. $57. ISBN 38055-2905-8 THE FRONTIERS OF SEX RESEARCH. Edited by Vein L. Bullough. 190 pp. Prometheus Books, Buffalo, New York, 1979. $16.95, clothbound; $6.95, paperbound. ISBN 0-87975-110-X, clothbound; ISBN 0-87975-113-4, paperbound GLAUCOMA UPDATE. International Glaucoma Symposium. Nara/Japan, May 7-11, 1978. Edited by G.K. Krieglstein and W. Leydhecker. 224 pp. IlIust. Springer-Verlag New York Inc., Secaucus, New Jersey, 1979. $29. ISBN 0-387-09350-8
Critically ill surgical patients account for approximately half the patients in an active multidisciplinary critical care unit. Hypovolemia and sepsis are common in such patients and affect a number of organ systems. Monitoring these systems provides therapeutically relevant information that may decrease morbidity and Improve patient survival. Circulatory hemodynamics may be assessed by direct measurement of the arterial blood pressure, central venous and pulmonary artery pressure monitoring and cardiac output determination; the data thus obtained are valuable in guiding fluid replacement in the hypovolemic individual. The respiratory status may be assessed by bedside spirometry and measurement of arterial blood gas tensions to gauge pulmonary function and the need for assisted ventilation. Renal dysfunction is common in such patients; careful analysis of both urine and blood may identify prerenal as opposed to renal and postrenal factors. Monitoring of the gastrointestinal tract, especially for hemorrhage, is important. Finally, careful attention to nutritional status and provision of adequate protein and energy intake by mouth or by vein is a vital component of the optimal care of these patients. Les patients de chirurgie dont l'etat est critique comptent pour environ Ia moitie des patients d'une unit6 multidisciplinaire de soins critiques. L'hypovolemie et Ia sepsie sont frequentes chez ces patients et affectent plusieurs systemes organiques. La surveillance de ces systemes procure une information pertinente au traitement qui est susceptible de diminuer Ia morbidite et d'ameliorer Ia survie du patient. Lhemodynamique circulatoire peut .tre evaluee par Ia mesure directe de Ia tension arterielle, Ia surveillance des pressions veineuse centrale et arterielle pulmonaire et Ia determination du debit cardiaque; les donnees ainsi obtenues sont utiles aux ajustements de Ia recharge liquidienne chez le sujet hypovolemique. L'etat respiratoire peut .tre verifie par spirometrie au chevet du malade et par Ia mesure des pressions gazeuses arterielles afin d'evaluer Ia fonction respiratoire et le besoin de ventilation assistee. Le dysfonctionnement renal est frequent chez ces patients; l'analyse minutieuse de l'urine et du sang peut identifier les facteurs prerenaux par opposition aux facteurs renaux et postrenaux. La surveillance du tractus gastrointestinal, specialement pour lapparition dune hemorragie digestive, est important. Finalement, une attention minutieuse portee a letat nutritionnel et a lassurance dun apport prot6inlque et energetique adequat par voie orale ou veineuse est une composante vitale des soins optimaux pour ces patients.
Critically ill surgical patients ac- cardiothoracic and major abdocount for approximately half of the minal operations, which involve patients in an active multidisci- fluid shifts and acid-base and plinary intensive care unit. Many metabolic derangements, necessitate surgical patients are admitted to intensive care. Finally, patients such a unit because of pre-existing with critical surgical illnesses that problems, such as cardiac or pul- involve multiple traumatic injuries, monary disease, that may be ag- peritonitis and burns are at risk of gravated by an operation. Certain multisystem failure and have comcomplicated procedures, such as plicated resuscitative needs that are best met in an intensive care From *the critical care/trauma unit, unit. Victoria Hospital and the department Intensive monitoring makes many of surgery, University of Western contributions to the care of these Ontario, London, and tihe department patients. First, it helps to minimize of surgery, Queen's University and the frequency of complications Hotel Dieu Hospital, Kingston, Ont. during and following an operation Reprint requests to: Dr. Ronald L. by uncovering correctable problems Holliday, Critical care/trauma unit, Victoria Hospital, 375 South St., early in their development, thereby London, Ont. N6A 4G5 facilitating their rapid resolution. *-For prescribing information see page 953
Second, it provides diagnostic insights into the complicated illnesses that may develop in such patients. Finally, it guides the administration of therapy. Elsewhere in this symposium Pietak and Teasdale address the problem of the high-risk patient undergoing surgical procedures and indicate what procedures are likely to require additional monitoring during anesthesia. Our paper aims to define the problems that develop in the critically ill surgical patient and to outline strategies for their assessment and therapy. Through problem-solving encounters with such patients the clinician develops a better understanding of the pathophysiology of shock as it relates to both hypovolemia and sepsis. Hypovolemia
The traumatized patient may experience hypovolemic shock; this occurs because of loss of whole blood, plasma or electrolyte-containing fluid. in the past 15 years much research has been undertaken to define the altered physiology in hypovolemic shock and its subsequent effects on basic cellular function. Shires and coworkers1'2 demonstrated a loss of "functional extracellular volume" in prolonged hemorrhagic shock, and further work has elucidated the nature of this loss. Hypovolemia, from whatever cause, leads to altered cell membrane function,3 with a loss of normal electrical activity. Subsequently a shift of intracellular and extracellular electrolytes occurs, so that sodium passes in and potassium passes out, with resultant cellular swelling.4'5 There is attendant alteration in the subcellular organelles, with mitochondrial swelling, and thereafter a loss of protein synthesis. The initial biochemical response is an increase in the sodium-potassium adenosine triphosphatase activity in an attempt to maintain cellular integrity.
CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
931
Eventually, however, the energy sources are dissipated, with increasing accumulation of inorganic phosphates. Intracellular breakdown of lysosomes occurs, and potent hydrolytic enzymes are released into the cell and ultimately into the organism as a whole to produce further damage.6'7 While most of these pathophysiologic changes in hypovolemic shock have been demonstrated in research animals, the observations have been extended to humans.8 It is obvious that if sufficient cellular changes occur there will eventually be organ failure. The critically ill human tolerates the failure of one organ system surprisingly well and that of two organ systems with some difficulty, but the failure of three organ systems nearly always proves fatal.
Peripheral vasodilation requires an tient has transcended traditional increased cardiac output to keep methods of assessment such as pace with the metabolic demands. blood pressure, pulse and temperThe increased vascular capacitance ature measurement. The increasing secondary to vasodilation necessi- sophistication of monitoring makes tates the administration of large personal contact with the patient volumes of fluid, which is best more difficult. However, frequent done with the aid of hemodynamic observation and physical contact monitoring so as to avoid cardio- between physician and patient repulmonary overload. Thus, the pa- main fundamental tenets in the care tient with septic shock presents of such individuals and must not more than a simple perfusion prob- be forgotten. Periodic inspection of lem, and treatment of the low blood wounds, incisions, drainage and pressure alone is inadequate. A catheter sites and monitoring lines hypodynamic phase of septic shock remains an integral part of daily exists, and its presence usually re- care. Despite these reservations, flects concomitant hypovolemia. monitoring of the hemodynamic Those caring for critically ill surgi- status of such individuals may be cal patients should be alert to the vital in providing optimal care." Arterial blood pressure: Blood possibility of latent sepsis. Prompt detection of otherwise unexplained pressure measurement by sphygmoalterations in urine output, respira- manometry can be inaccurate, tory rate, temperature, the senso- especially in the hypovolemic parium, cardiac rhythm and acid- tient.14 This has led to direct intrabase balance, and the appearance arterial monitoring via the radial, Sepsis of bruising, bleeding or leukocy- brachial, axillary, femoral, dorsalis Although sepsis may be the tosis can permit early diagnosis of pedis and superficial temporal reason for admission to an inten- sepsis and effective therapy. Dis- arteries. Either a percutaneous apsive care area, it is more often a seminated intravascular coagula- proach or surgical cutdown may be complication of another critical ill- tion commonly complicates septic used, and appropriate precautions ness. Sepsis is related in part to the shock and should be anticipated by should be taken to ensure an misuse of drugs such as antibiotics a search for coagulation abnormal- aseptic technique and avoidance of that allow a resistant organism to ities as well as split products of distal circulatory impairment. A flourish or a nosocomial infection fibrin degradation.11 functioning flush system is required to develop. Infection may also be to ensure patency. Since complicafacilitated by the presence of Monitoring organ system function tions from arterial lines may 15 tracheostomy tubes, drainage sites in critical surgical illness occur, the indications for such and monitoring devices such as monitoring must be carefully asAlthough hemodynamic assess- sessed. Intra-arterial monitoring intravenous and urinary tract catheters, which permit the entry of ment is an important component of provides not only accurate blood organisms. Many patients are at in- the sophisticated monitoring re- pressure measurement, but also creased risk because their underly- quired for the critically ill surgical access for arterial blood sampling. ing disease has led to anergy, with patient, monitoring of all major Central venous pressure: Moniserious reduction in the usual systems is necessary for optimal toring of the central venous preshost defence mechanisms. The care.12 The key to success rests with sure (CVP) was initiated in 1931 use of immunosuppressive, cortico- the team caring for the patient but was not popularized until the steroid or anticancer drugs also more than with the equipment. The late 1960s.'0 Today the Swanintensive care nurse is an indis- Ganz catheter is used with increaspredisposes to sepsis. pensable component of the team; ing frequency, but valuable informaThe past 10 years have witnessed important advances in the under- she must be knowledgeable, moti- tion can still be obtained with standing of septic shock.9'10 The vated and enthusiastic, and must proper CVP monitoring provided hyperdynamic phase of sepsis is remain "the compleat monitor". A there is no significant associated characterized by a high cardiac plan must be developed for se- cardiopulmonary disease. The CVP output, a wide pulse pressure and quential introduction of monitoring catheter is ideally inserted into the an inappropriately high urine out- that involves all systems vital for superior vena cava for measurement put. In all likelihood the problem life. It should include a routine for of the right ventricular filling presbegins with an endotoxin-immune dealing with the large volume of sure (RVFP). The RVFP, however, complex phenomenon that produces data generated in these circum- is not a measure of the blood volcellular damage. Subsequent changes stances; this permits sequential re- ume but, rather, varies directly with in capillary permeability occur view of the information and a trend it and with vascular tone as well as either because of this interaction or analysis of the monitored indices. reflecting right heart competence.17 secondary to the release of vasoAlthough the normal range of the active substances such as brady- Circulatory hemodynamics CVP is stated to be approximately kinin, serotonin and histamine. Monitoring the critically ill pa- 5 to 12 cm H20, it is serial 932 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
measurements rather than absolute values that are most helpful in directing patient care. Hence, the response of the CVP to a bolus fluid challenge in a patient with hypovolemia may provide useful information. However, pitfalls in interpretation occur in a number of situations that are common in critically ill patients - for example, increased intrathoracic pressure, alterations in right ventricular compliance, pulmonary embolism and increased pulmonary vascular resistance." In addition, when there is underlying disease of the left ventricle the CVP may be an unreliable guide to the adequacy of the central blood volume and cardiac performance; this is discussed in detail elsewhere in this symposium. Swan-Ganz balloon flotation catheter: The limitations of CVP measurement as a means of hemodynamic monitoring were among the stimuli that led to the development of the Swan-Ganz catheter. With this catheter various pressures, including right atrial, pulmonary artery and pulmonary capillary wedge, can be measured.19 Recent modifications permit simple and reproducible measurement of the cardiac output by the thermal dilution technique. A catheter placed in the pulmonary artery allows true mixed venous blood sampling and measurement of both venous oxygen tension and venous oxygen saturation at this site. Simultaneous sampling of arterial and mixed venous blood permits calculation of the arterialvenous oxygen difference; narrowing of this difference may indicate a high cardiac output and complicating sepsis, whereas a widened difference highlights a diminished cardiac output and indicates a need for efforts to augment it." With this kind of information one can make other calculations of oxygen transport and delivery, some of which are discussed later in this article and elsewhere in the symposium. The experience of one of us (R.L.H.) with the Swan-Ganz catheter constitutes 34 insertions in 120 general surgical patients admitted to a critical care unit in 1977. The indications for monitoring were multiple injuries requiring the administration of large volumes
of fluid, postoperative complications such as sepsis and hypotension, and preoperative observation in high-risk patients. Predictably the mortality in this group was high, reflecting the fact that invasive monitoring was reserved for the sickest patients. Pitfalls in hemodynamic monitoring have been previously discussed in this symposium, but it is worth emphasizing that the measurements must always be interpreted in the light of the clinical situation. In summary, valuable information concerning the hemodynamic status of the critically ill surgical patient may be obtained that will influence the choice of therapy and guide subsequent decisions. Respiratory status Respiratory problems are an important cause of disability and death in the critically ill surgical patient." It is therefore vital to assess the respiratory status preoperatively and ascertain which patients are at increased risk by reason of important underlying cardiopulmonary disease. Once identified, such patients should be followed with careful preoperative and perioperative respiratory assessment. This is especially true following abdominal and thoracic surgical procedures, during which significant alterations in respiratory function occur. These alterations include an increase in the ratio of dead space to tidal volume (Vd/Vt), a reduced functional residual capacity (FRC) and an attendant increase in ventilatory rate, with an accompanying increase in the overall work of breathing. Should progressive respiratory failure develop, it is mandatory to consider what correctable underlying factors exist, such as atelectasis, pneumothorax, latent sepsis, pulmonary edema and pulmonary emboli. The adult respiratory distress syndrome is known to occur in surgical patients, and the many etiologic factors in this syndrome are well detailed elsewhere." Respiratory monitoring should begin with a complete clinical examination, examination of the sputum by Gram-staining and culture when indicated, and chest roentgenography. Among the other
methods available for monitoring, analysis of blood gases remains one of the most important. This may be done with a sample of capillary blood in a patient with good perfusion, but direct arterial sampling is required in a patient with hypovolemia or vasoconstriction. The alveolar-arterial difference in oxygen tension (AaDol), as derived in the appendix, provides a useful gauge of respiratory function by evaluating the relation between the arterial tensions of oxygen and carbon dioxide, thereby giving more meaningful data than would either measurement alone. Alveolar ventilation can be accurately assessed from the carbon dioxide tension in the absence of metabolic alkalosis; if it rises above 55 mm Hg assisted ventilation should be considered. Likewise, if the AaDo2 exceeds 50 to 60 mm Hg while the patient is breathing room air, or 350 or 450 mm Hg while the patient is breathing 100% oxygen, ventilatory assistance may be required. The decision to begin assisted ventilation must always be made in the light of the clinical situation, with particular regard to the work of breathing and the patient's prior pulmonary status. Thus, mechanical ventilation may be desirable in some instances even though the aforementioned blood gas criteria are absent; conversely, despite the presence of these criteria assisted ventilation may prove unnecessary. Bedside spirometry may be useful in assessing the ventilatory and mechanical aspects of pulmonary function. Preoperatively a reduced forced expiratory volume during the first second of exhalation, a decreased maximum midexpiratory flow, an increased residual volume or an increased Vd/Vt may indicate important chronic obstructive lung disease. Compliance, which is expressed as the volume of air that can move in the lungs with each unit of pressure change, is another factor affecting ventilation. Diminished lung volume, reduced or absent pulmonary surfactant production and increased lung water content are all factors that may be operative in the adult respiratory distress syndrome and may contribute to reduced lung compliance. It is vital
CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
933
to assess the pulmonary compliance when a patient is undergoing mechanical ventilation; effective compliance (Ce.) can be estimated by assessing the relation between flow or tidal volume (TV) and the peak inflation pressure. Thus, C.fr = TV! peak inspiratory pressure If there is decreased compliance (that is, an increased resistance to flow) such that a greater peak inflation pressure is required for ventilation, one should be alert to the possibility of respiratory-induced pneumothorax or airway obstruction. Certain assumptions are involved in the calculation of many of the indices of respiratory function we have outlined. The influence of temperature, cardiac output and metabolic status should be considered. Hypothermia, alkalosis and a reduced erythrocyte 2,3-diphosphoglycerate content all decrease the availability of oxygen to the tissues by shifting the oxyhemoglobin dissociation curve up and to the left. Laboratory indices of pulmonary function are of greatest help if their trends are followed over time. Renal function
Oliguria (a urine output of less than 400 ml/24 h) is most commonly a secondary phenomenon of hypovolemia in the critically ill surgical patient. In addition to clinical manifestations, hypovolemia may be reflected in the quality of the urine produced; typically there is a reduced sodium concentration (less than 10 to 20 mmol/l) and an increased osmolarity. As well, the urine/plasma creatinine ratio is increased (to more than 20). By contrast, a direct renal cause for the oliguria would be expected to result in a higher urine sodium concentration (greater than 40 mmol/l), a reduced urine osmolarity and a lower urine/plasma creatinine ratio, as well as some abnormality in the urine sediment. Urinary tract obstruction must also be considered in the critically ill surgical patient, especially when there is anuria. Polyuria may complicate the recovery from acute oliguric renal failure, and careful attention to
water and electrolyte balance is required. In addition, the catabolic state of some critically ill surgical patients may result in a high osmotic load, with an attendant increase in urine output (so-called high output or nonoliguric renal failure.). This syndrome is characterized by the excretion of large volumes of iso-osmotic urine as well as by rising blood urea nitrogen (BUN) and serum creatinine concentrations. Sepsis may also be associated with polyuria that appears to be related to tubular dysfunction, with the excretion of urine of a high sodium concentration. A disproportionate rise in the BUN level over the serum creatinine level should alert the physician to a prerenal cause for azotemia, such as hypovolemia, upper gastrointestinal tract hemorrhage or excessive tissue breakdown. The surgical patient with hyponatremia, hemodilution and a high urine osmolarity relative to that of plasma should be suspected of having inappropriate secretion of antidiuretic hormone. In the critically ill surgical patient there may be a variety of causes for this, including drug administration, general anesthesia, positive-pressure ventilation, pneumonia and head trauma. First-line therapy should include water restriction and removal of any correctable cause. A detailed discussion of fluid and electrolyte disturbances as well as acid-base problems in the critically ill surgical patient is beyond the scope of this presentation. As previously noted, however, trauma may lead to capillary leakage, with progressive interstitial edema and a depleted intravascular volume, and subsequently an increase in the secretion of aldosterone and antidiuretic hormone. Electrolyte and acid-base disturbances must be interpreted in an integrated fashion, with a knowledge of whether they represent acute or pre-existing abnormalities and how an alteration of one will affect the others. Gastrointestinal function Alterations in the gastrointestinal system may be a serious associated problem for the critically ill surgical patient. Traditional methods of assessing the gastrointestinal tract include careful abdominal palpa-
934 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
tion and auscultation, measurement of abdominal girth, a search for gastrointestinal tract bleeding via a nasogastric tube and rectal examination, paracentesis and examination of the plain abdominal roentgenogram made with the patient either upright or in the decubitus position. Paralytic ileus is a common accompaniment of critical illness. It is usually gastric in origin unless there is associated peritonitis. Electrolyte disturbances, particularly hypokalemia, may either initiate the ileus or potentiate it and prolong recovery. A nasogastric tube is usually indicated for gastric decompression when ileus is present, and it may also be helpful in assessing the presence of upper gastrointestinal tract bleeding. Certain problems exist, however, with the introduction of a nasogastric tube, including continued gastroesophageal reflux, with associated esophagitis, nasopharyngeal and gastroesophageal erosions, and infection. The tube incites copious gastrointestinal secretion, and its continuing removal causes metabolic alkalosis and electrolyte imbalance. These complications are generally reversible with removal of the tube. Gastrointestinal tract bleeding, particularly from "stress ulceration", is an ever-present threat in the critically ill patient. The entire gastrointestinal tract is at risk, however, and monitoring of the gastric secretions and stool for the presence of blood may alert the physician to this problem. Appropriate early prophylactic measures include continual use of antacids to keep the gastric pH above 4. Administration of cimetidine as a bolus or as a continuous infusion has also been suggested. Recent work suggests that the gastric mucosa in critically ill humans may leak protein prior to erythrocytes, and this may offer another avenue for monitoring (D.P. Girvan and B. Taylor: personal communication, 1978). Liver dysfunction may also be present in a critically ill surgical patient, although it may be subclinical, with subtle alterations in serum bilirubin and liver enzyme concentrations appearing prior to overt clinical signs such as jaundice.24
Nutritional status There have been rapid strides in the understanding of nutrition in the surgical patient over the past 10 years. Identification of nutritional deficiency prior to major elective surgery is important since careful attention to its correction may improve the postoperative course and the chances for survival. There are a number of patterns of nutritional abnormalities in critically ill surgical patients, but excessive catabolism, with destruction of lean body mass (muscle protein), is the common denominator. This response, while initially protective by supplying additional substrate for metabolism, eventually becomes self-defeating because of excessive tissue breakdown; the subsequent muscle weakness may contribute to hypoventilation and difficulty in weaning the patient from the respirator. Diminished muscular activity in the legs may be incriminated in the frequent occurrence of venous thrombosis and pulmonary embolism. Precise monitoring of these nutritional changes is difficult since weight gain or loss in the critically ill may be an inadequate gauge owing to the rapid changes in fluid volume. Hypoalbuminemia is common and is particularly marked in the burn patient, but it may be a late manifestation of malnutrition. Nitrogen balance studies are difficult to perform and often give inaccurate results; perhaps measurement of the urea concentration in a 24-hour collection of urine is the best available bedside tool provided there is not coexistent renal failure. When a careful review of the premorbid nutritional status and body mass, basal metabolic rate and daily nutritional requirements is added to these estimations, a comprehensive plan for replacing needed protein and energy may be evolved. It is prudent to assume that every critically ill surgical patient is likely to become nutritionally depleted unless adequate energy, vitamins and protein are provided by mouth or by vein. If the oral route cannot be used, total parenteral nutrition may be advisable.25 The patient requiring such therapy is usually severely ill and likely to remain so for an extended period,
and has a gastrointestinal tract fistula with peritonitis, extensive bowel resection or inflammation, or both, severe continuing pancreatitis or extensive burns. There may be an initial "hypercatabolic phase", during which there are tremendous energy requirements that have been provoked by the stress of the operation and by inadequate peripheral perfusion or oxygenation, or both. After this stress has passed and homeostasis has been restored, the patient may enter a "stress catabolic phase", during which organ failure, persistent sepsis or slowly resolving organ dysfunction is present and the daily metabolic demands may exceed 13 x 1 0. kJ (roughly 3000 Cal). A final "starvation catabolic phase" indicates that organ failure has been reversed and sepsis eliminated; effective nutritional support during this phase may rapidly lead to a return to anabolism.'6 Total parenteral nutrition for such patients should never consist of glucose infusions alone, but rather should consist of solutions of glucose and fat supplemented with essential amino acids, vitamins and trace elements. The energy! nitrogen ratio may vary, depending on the catabolic phase judged to be present. Thus, this form of therapy requires careful monitoring and anticipation of complications, which may include local and systemic sepsis, especially fungal, hyperosmolar diuresis, electrolyte imbalance and hyperglycemia. Summary
An overview of the pathophysiological disturbances present in critically ill surgical patients has been presented. Adequate monitoring of such patients requires assessment of several organ systems to detect organ dysfunction and guide its correction. References 1. SHIRES T, BROWN FT, CANIZARO PC,
et al: Distributional changes in extracellular fluid during acute hemorrhagic shock. Surg Forum 11: 115, 1960 2. SHIRES T, CARRICO CJ, COLN D:
Role of the extracellular fluid in shock. mt Anesthesiol Gun 2: 435, 1964
3. SHIRES
GT,
CUNNINGHAM
JN,
BAKER CRF, et al: Alterations in cellular membrane function during hemorrhagic shock in primates. Ann Surg 176: 288, 1972 4. TRUNKEY
D, HOLCROFT J, CAR-
PENTER MA: Calcium flux during hemorrhagic shock in baboons. J Trauma 16: 633, 1976 5. HALJAMXE H: Effects of hemorrhagic shock and treatment with hypothermia in the potassium content and transport of single mammalian skeletal muscle cells. Acta Pliysiol Scand 78: 189, 1970 6. MELA LM, MILLER LD, NICHOLAS
GG: Influence of cellular acidosis and altered action concentrations on shock-induced mitochondrial damage. Surgery 72: 102, 1972 7. BELL ML, HERMAN AH, SMITH EE,
et al: Role of lysosomal instability in the development of refractory shock. Surgery 70: 341, 1971 8. CUNNINGHAM IN JR, CARTER NW, RECTOR FC JR, et al: Resting trans-
membrane potential difference of skeletal muscle in normal sllbjects and severely ill patients. J Clin Invest 50: 49, 1971 9. Wmisow AJ, LOEB HS, RAHIMTOOLA SH, et al: Hemodynamic studies and results of therapy in 50 patients with bacteremic shock. Am J Med 54: 421, 1973 10. WElL MH, NISHIJIMA H: Cardiac output, in bacterial shock. Am J Med
64: 920, 1978 11. RAPAPORT 5: Defibration syndromes, in Hematology, WILLIAMS WJ, BEUTLER E, ERSLER AJ, et al (eds), McGraw, New York, 1977, p 1454 12. GREENBERG AG, TESKIN GW: Monitoring in the recovery room and surgical intensive care unit, in
Monitoring in A nesthesia, SAIDMAN LG, SMITH NT (eds), Wiley, New
York, 1978, p 221 13. SWAN HJC: Role of hemodynamic monitoring in the management of the critically ill. Crit Care Med 3:
83, 1975 14. COHN JN: Blood pressure reassessment in shock. Mechanism of inaccuracy in auscultatory and palpatory methods. JAMA 199: 972,
1967 15. BEDFORD RF, WOLLMAN H: Complications of percutaneous radialartery cannulation: an objective prospective study in man. Anes-
thesiology 38: 228, 1973 16. KNOPP R, DAILEY RH: Central venous cannulation and pressure monitoring. JACEP 6: 358, 1977 17. GUYTON AC, JONE CE: Central venous pressure: physiological significance and clinical implications.
Am Heart J 86: 431, 1973 18. BRISMAN R, PARKS LC, BENSON DW: Pitfalls in the clinical use of central venous pressure. A rcli Surg
95: 902, 1967
CMA JOURNAL/OCTOBER 6, 1979/VOL 121
935
SEPTR. DS * now available in convenient, smaller-size tablet * broad-spectrum activity provides bactericidal coverage against all these respiratory pathogens: ii, influenzae, including many ampicillinresistant strains; 0. pneumoniae: Klebsiella: .tr.ptococcus . and viridans; .i.pAiyijcoccus aureus and albus * discourages development of resistance * achieves rapid, high blood levels; significant levels in lung tissue and sputum * well tolerated by most patients * Septra is also available in licorice-flavored suspension. well accepted by children
* Septra2 (Trimethoprim + Sulfamethoxazole) l9. Summary INDICATIUS: Indicated for the following infections when caused by susceptible organisms: UPPER AND LOWER RESPIRATORY TRACT INFECTIONS-particularly chronic bronchitis and acute and chronic of if is media. URINARY TRACT INFECTIONS-acute, recurrent and chronic. GENITAL TRACT INFECTIONS-uncomplicated gonococcal urethritis. GASTROINTESTINAL TRACT INFECTIONS. SKIN AND SOFT TISSUE INFECTIONS. SEPTRA is also indicated in the treatment of infants and children with a diagnosis of Pneumocysf is carinii pneumonitis, especially if they are immunosuppressed. SEPTRA is not indicated in infections caused by Pseudomonas, Mycoplasma or viruses. This drug has not yet been fully evaluated in streptococcal infections. CONTRAINOICATIONS: Patients with evidence of marked liver parenchymel damage, blond dyscrasias, known hypersensitivity to trimethoprim or sulfonamides, marked renal impairment where repeated serum assays cannot be carried out, premature or newborn babies during the first few weeks of life. For the time being SEPTRA is contrair'dicafed during pregnancy. ADVERSE REACTIONS: Most frequent: nausea; vomiting; gastric intolerance; and rash. Less frequent: diarrhea; constipation; flatulence; anorexia; pyrosis; gastritis; gastroenteritis; urticaria; headache; and liver changes (abnormal elevations in alkaline phosphatase and serum transaminase). Occasionally reported: glossitis; oliguria; hematuria; tremor; vertigo; alopecia; and elevated BUN, NPN, and serum creatinine. Hematological changes occurring particularly in the elderly, are mostly fransient and reversible (primarily, neutropenia and thrombocytopenia; less frequently, leukopenia, aplastic or hemolytic anemia, agranulocytosis, and bone marrow depression). PRECAUTIONS: As with other sulfonamide preparations, critical appraisal of benefit versus risk should be made in patients with liver damage, renal damage, urinary obstruction, blood dyscrasias, allergies or bronchial asthma. The possibility of a superinfection with a non-sensitive organism should be borne in mind. DOSAGE AND ADMINISTRATION: Adults and children over 12 years. Standard dosage: 2 Septra tablets or 1 Septra OS tablet twice daily. Minimum dosage and dosage for long-term treatment: 1 Septra tablet or Y2 Septra OS tablet twice daily. Maximum dosage: Overwhelming infections: 3 Septra tablets or 1/2 Septra OS tablets twice daily. Uncomplicated gonorrhea: 2 Septra tablets or 1 Septra OS tablet four times daily for 2 days. Pneumu.,ystis carinii pneumonitis: 20 mg/kg/day trimethoprim and kI0 mg/kg/day sulfamethoxazole in four divided doses for 14 days. Children 12 years and underi Young children should receive a dose according to biological age: Children under 2 years: 2.5 ml of suspension twice daily. Children 2 to 5 years: 2.5-5 ml of suspension twice daily. Children 6 to 12 years: 5-10 ml of suspension twice daily. tIn children this corresponds to an approximate dose of 6 mg trimethoprim/kg body weight/day, pIus 30 mg sulfamethoxazole/kg body weight/day, divided into two equal doses. DOSAGE FORMS SEPTRA OS TABLETS, each containing 160 mg trimethoprim and 800 mg sultamethoxazole, and coded WELLCOME 02C. Bottles of 50 and 250. SEPTRA TABLETS, each containing 80 mg trimethoprim and 400 mg sulfamethoxazole, and coded WEILCOME Y2B. Bottles 01100 and 500, and unit dose packs of 100. SEPTRA PEDIATRIC TABLETS, each containing 20 mg trimethoprim and 100 mg sulfamethoxazole, and ceded WELLCOME H4B. Bottles of 100. SEPTRA PEDIATRIC SUSPENSION, each teaspoonful (5 ml) containing 40mg trimethoprim and 200 mg sulfamethoxazole. Bottles of 100 and 400 ml. Product monegraph available on request. 2Trade Mark W-7013
.I i.llcome Medical Division BUrroUghS V.llcome Ltd.
19. PACE NL: A critique of flowdirected pulmonary arterial catheterization. Anesthesiology 47: 455, 1977 20. WILSON RF, GIBSON D: The use of arterial-central venous oxygen differences to calculate cardiac output and oxygen consumption in critically ill surgical patients. Surgery 84: 362, 1978 21. DOWNS JB: Respiratory failure. Part 1 - the adult. Curr Probi Anesth Grit Care Med 1: 4, 1978
23. ANDERSON RJ, LINAS SL, BERNS AS, et al: Nonoliguric acute renal failure. N Engi j Med 296: 1134, 1977
22. PONTOPPIDAN H, GEFFIN B, Low-
Surgical Patient: Medical, Surgical and Anesthetic Management, SIEGEL
ENSTEIN E: Acute respiratory failure in the adult (first of three parts). N Engi J Med 287: 690, 1972
24. CHAMPION HR, JONES RT, TRUMP
BF, et al: A clinicopathologic study of hepatic dysfunction following shock. Surg Gynecol Obste*. 142: 657, 1976 25. MOORE FD, BRENNAN ME: Intravenous feeding. N Engi J Med 287:
862, 1972 26. BORDER JR, LADUCA J, SEIBEL R: Nutritional support of the surgical
patient, in The Aged and High Risk
JH, CHODOFF PD (eds), Grune, New York, 1976, p 239
Appendix - Derivation of alveolar-arterial difference in oxygen tension AaDo2 = PAo2 - Pao2 = [(PB - PH2o)FIo2 - Paco?] - Pao, where AaDo2 = alveolar-arterial difference in oxygen tension PAo2 = alveolar oxygen tension Pao2 = arterial oxygen tension PH = barometric pressure PH2O = water vapour pressure F1o2 = fraction of inspired oxygen Paco2 = arterial carbon dioxide tension For example, with an F1o2 of 100% at sea level, a Pao2 of 350 mm Hg and a Pco2 of 40 mm Hg, AaDo2 = [(760 - 47)1.0 -- 40] - 350 = 323 Assuming a normal cardiac output, this may be simplified for a patient with previously normal pulmonary function at sea level breathing room air: AaDo2 = 145 - (Pao2 + Paco2) The normal range of the AaDo2 for a healthy young adult is 10 to 20 mm Hg.
continued from page 900 1978 DIRECTORY OF ON-GOING RESEARCH IN SMOKING AND HEALTH. Compiled by Informatics Inc., Rockville, Md. 433 Pp. US Department of Health, Education, and Welfare, Public Health Service, Office on Smoking and Health, Rockville, Maryland, 1979. Price not stated, paperbound DISORDERS OF STRESS AND THEIR MANAGEMENT BY YOGA. A Study of Neurohumoral Response. K.N. Udupa. 205 pp. IlIust. Banaras Hindu University, Varanasi, India, 1978. Price not stated, paperbound THE DOCTOR AND THE LAW. A Practical Handbook for the Canadian Physician. H.E. Emson. 235 pp. The Macmillan Company of Canada Limited, Toronto, 1979. $9.95, paperbound. ISBN 0-7705-1786-2 THE EFFECTS OF PSYCHOTHERAPY. Volume 1. Michael J. Lambert. 158 pp. Eden Press Inc., Montreal, 1979. $20. ISBN 0-443-02030-2 ENTEROSTOMAL THERAPY: DEVELOPING INSTITUTIONAL AND COMMUNITY PROGRAMS. Linda Gross and Zeila Bailey. 221 pp. IlIust. Nursing Resources, Inc., Wakefield, Massachu-
936 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
setts, 1979. Price not stated, paperbound. ISBN 0-913654-49-3 ENZYMES IN CARDIOLOGY. Diagnosis and Research. Edited by David J. Hearse and Joel de Leiris. 586 pp. Illust. John Wiley & Sons, New York, 1979. $70. ISBN 0-471-99724-2 FRONTIERS OF GASTROINTESTINAL RESEARCH. Vol. 5. Gastrointestinal Cancer: Advances in Diagnostic Techniques and Therapy. Selected Papers of the International Conference on Gastrointestinal Cancer, Tel Aviv, November 1977. Edited by P. Rosen, S. Eidelman and T. Gilat. 225 pp. IlIust. S. Karger AG, Basel, 1979. $57. ISBN 38055-2905-8 THE FRONTIERS OF SEX RESEARCH. Edited by Vein L. Bullough. 190 pp. Prometheus Books, Buffalo, New York, 1979. $16.95, clothbound; $6.95, paperbound. ISBN 0-87975-110-X, clothbound; ISBN 0-87975-113-4, paperbound GLAUCOMA UPDATE. International Glaucoma Symposium. Nara/Japan, May 7-11, 1978. Edited by G.K. Krieglstein and W. Leydhecker. 224 pp. IlIust. Springer-Verlag New York Inc., Secaucus, New Jersey, 1979. $29. ISBN 0-387-09350-8
