Subspecialty Clinics: Critical-Care Medicine Intubation of Critically III Patients
MICHAEL K. J. HEE, M.D., DAVIn J. PLEVAK, M.D., Department ofAnesthesiology; STEVE G. PETERS, M.D., Critical Care Service
Respiratory failure is one of the most common causes for admission to an intensive-care unit. Any patient with loss of central nervous system control of breathing, neuromuscular respiratory failure, or impairment of gas exchange may require tracheal intubation and mechanical ventilation. Tracheal intubation provides a conduit for ventilatory support, maintains the patency of an airway that has potential for obstruction, protects the airway from the contents of the stomach, and allows access to the trachea for pulmonary hygiene. Although the mechanics of intubation are easily learned, many factors must be considered in critically ill patients. Herein we summarize the principles of tracheal intubation in acutely ill patients.
The basic mechanics of tracheal intubation are easily described.'> The blade of the laryngoscope is inserted into the right side of the mouth; while the tongue is moved to the left side, the blade is advanced into the pharynx until the glottis is visualized. The endotracheal tube is then passed into the trachea. Tracheal intubation is an easy procedure when performed under controlled conditions in a healthy, paralyzed patient with normal airway anatomy. Tracheal intubation can be difficult, however, in critically ill patients, many of whom have hypoxia or hypercapnia (or both). Whether tracheal intubation is performed urgently or electively, the transition from the nonintubated to the intubated state is a delicate period during which numerous factors can compromise an already fragile patient. Successful intubation of critically ill patients is facilitated by a familiarity with the technical aspects and by a knowledge of strategies designed to prevent hypoxia and precipitous hemodynamic alterations and to minimize the risk of aspiration. Successful intubation is likely after careful preintubation planning. Address reprint requests to Dr. D. J, Plevak, Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, Mayo Clin Proc 67:569-576, 1992
PREPARATION FOR INTUBATION Assembling the necessary equipment and personnel is essential for a successful intubation. Preparation is facilitated by a careful assessment of the airway for ease of intubation. If difficulty is anticipated, specialized equipment can be ordered, and personnel with additional expertise can be summoned. If the situation is emergent, intubation can be initiated before extra help arrives. Personnel in general hospital wards and in some intensive-care units may be unfamiliar with the intubating equipment, drugs, and technique. Therefore, a person who has experience in the art of management of the airway should be present. At the Mayo Clinic, standardized intubation carts are located in the intensive-care units. An assortment of laryngoscope blades, airways, masks, and endotracheal tubes are included in these carts (Table 1). Most adult female patients will be able to accommodate a 7.5-mm internal diameter endotracheal tube, and most adult male patients will be able to accept an 8.0-mm endotracheal tube. In an emergency, an endotracheal tube that is 0.5 mm smaller than anticipated may be used to ensure accommodation. The tube can be changed later, when the situation is less critical. 569
570
INTUBAnON OF CRITICALLY ILL PATIENTS
Mayo Clin Proc, June 1992, Vol 67
muscle relaxant may increase the oral opening. Another factor that increases ease of visualization is the patient's ability to protrude the mandible beyond the upper incisors. Laryngoscope handle Once the laryngoscope has been placed in the patient's Blades Straight (Miller 2 or 3) mouth, the view of the glottis may be obscured by soft tissue Curved (Macintosh 3) structures. Mallampati and associates" developed a clinical Assorted endotracheal tubes indicator based on the size of the posterior aspect of the Syringe (12 ml) tongue relative to the size of the oral pharynx. With the paAssorted stylets tient seated and the tongue protruded maximally, the ability Viscous lidocaine Anesthetic spray to visualize the faucial pillars (the palatoglossal and palatoPhenylephrine spray pharyngeal arches), the uvula, and the soft palate allows one Magill's forceps to predict the ease of visualization of the glottis. When all Assorted airways (nasal and oral) three structures can be visualized (class I), a relatively easy Flowmeter with nipple adapter intubation can be anticipated. When the uvula is masked and Anesthesia bag and assorted masks Cricoid jet ventilation unit only the faucial pillars and the soft palate are visible (class II), Mallampati and colleagues" found intubation to be relatively difficult 35% ofthe time. Finally, when only the soft A reliable supply of oxygen connected to an anesthesia or palate could be visualized (class III), in most patients the self-inflating bag and a mask of proper size should be readily glottis could not be exposed by direct laryngoscopy. The size of the mandible can also provide clues of a available. A rigid-tip suction catheter (for example, Yankauer's) should be prepared, tested, and easily within difficult intubation. It can be assessed by measuring the reach. In addition, a free-flowing intravenous line that facili- distance from the hyoid bone to the mandibular symphysis. tates the rapid delivery of pharmacologic agents or intravas- When three fingers can be placed between the hyoid bone cular fluids should be present. Equipment that monitors the and the mandibular symphysis, the mandibular size is adepulse, blood pressure, and oxygen saturation should be used quate. If this area is less than two fingers, the mandible can be considered hypoplastic, and intubation may be difficult. frequently before, during, and after the procedure. Dental configuration can hinder visualization. In general, an edentulous patient is easier to intubate than is a patient ASSESSMENT OF THE AIRWAY Assessment of the airway should include the elicitation of with a full set of teeth because of the greater space for pertinent medical history and an examination of the follow- movement of the laryngoscope. Likewise, patients with ing: (I) mobility of the neck, (2) mobility of the mandible, protruding incisors are relatively difficult to intubate. Denti(3) size of the tongue, (4) size of the mandible, and (5) dental tion should be examined for overall condition before intubation. A tooth dislodged into the airway can complicate an condition and configuration. A mobile neck is essential for easy visualization of the already critical situation. The patient's history and overall condition may provide glottis. The sniffing position-that is, flexion of the lower aspect of the neck and extension of the head-is optimal for some clues about ease of intubation. Previous intubations oral intubation. This maneuver brings the oral, pharyngeal, may be points of reference. Certain conditions-for exand laryngeal axes into a straight line. If the patient is unable ample, rheumatoid arthritis, ankylosing spondylitis, or conto flex chin to chest, a difficult intubation can be anticipated. genital defects-that affect the mobility of the neck and the Extension of the neck occurs at the atlanto-occipital joint. structure of the head and neck can make intubation difficult. The distance between the occiput and the spinous process of C-I is important. This area can be assessed by measuring PREVENTION OF HYPOXIA from the thyroid cartilage to the mandibular symphysis while Tracheal intubation should not cause or exacerbate hypoxia. the patient's neck is extended. If this distance is less than the Because patients may be without supplemental oxygen and will frequently have apnea during intubation, the procedure width of four adult fingers, intubation may be difficultr' Mobility of the mandible is important because a success- should take less than 30 seconds. Oxygen can be adminisful oral intubation necessitates a sufficiently wide passage to tered into the patient's mouth or nose (or both) during intuaccommodate the laryngoscope blade. Therefore, patients bation by allowing oxygenation by convection. Whenever should be able to open their mouths at least three finger- possible, an oxygen saturation monitor should be used to breadths. Inability to open to this width may be related to warn of hypoxemia. The time available for intubation can be maximized by dysfunction of the temporomandibular joint or due to restriction by muscular structures. In some patients, use of a preoxygenation (denitrogenation), replacing the nitrogen in Table l.-Supplies That Should Be Readily Available for Tracheal Intubation
Mayo Clin Proc, June 1992, Vol 67
the patient's functional residual capacity with oxygen. During laryngoscopy, apneic oxygenation can occur from this reservoir. Preoxygenation can best be accomplished by ventilating with 100% oxygen delivered at a high flow rate. For effectiveness, a tight-fitting face mask is essential. The duration necessary for preoxygenation varies with the gas flow, the system used, the size of the functional residual capacity, and the patient's oxygen consumption, but it is generally 3112 minutes.'
INTUBATION OF CRITICALLY ILL PATIENTS
571
Thiopental sodium, a short-acting barbiturate, is the classic anesthetic induction agent. An induction dose of 4 mg/kg will result in apnea and loss of consciousness in 1 circulation time (approximately 40 seconds). Recovery of consciousness and resumption of spontaneous respirations usually occur within 10 minutes and are due to redistribution of the drug. Sedative effects may linger for hours because of a long elimination half-life. The advantages of thiopental are the favorable effects on cerebral protection, a decrease in intracranial pressure, and a rapid and reliable production of unconsciousness. DisadvanMINIMIZATION OF HEMODYNAMIC EFFECTS tages include cardiovascular depression, which can result in Intubation of the trachea and subsequent initiation of posi- hypotension in patients with hypovolemia or in debilitated tive-pressure ventilation can cause a wide array of hemody- patients, and the long half-life. In small doses, titrated namic derangements that are detrimental to critically ill pa- carefully, sedation is produced and respirations can be maintients. Both laryngoscopic manipulation of the airway and tained; however, the benzodiazepines are probably a better insertion of the endotracheal tube into the trachea can mas- choice than thiopental. Although sedation and amnesia may sively increase sympathetic outflow; this outcome progres- occur, thiopental is not an analgesic and therefore may prosively increases mean arterial blood pressure and heart rate duce hyperalgesia. Thiopental is primarily used to produce a above normal levels in an awake patient." Infants, children, state of unconsciousness whether the patient is breathing and young adults sometimes respond with a vasovagal reac- spontaneously or has apnea. Propofol (Diprivan; 2,6-diisopropylphenol), a relatively tion, which results in bradycardia and hypotension. Positivepressure ventilation in a debilitated patient with hy- new compound, is a milky emulsion that contains soybean povolemia can decrease venous return and cause hypoten- oil, egg lecithin, and glycerol. As with thiopental, an inducsion. In addition, intubation is an uncomfortable procedure tion dose of propofol produces loss of consciousness, which that can cause severe psychologic stress manifested by is regained during a time frame similar to that of thiopental. hemodynamic alterations. These responses can be attenu- The advantage of propofol over thiopental is the short metaated by (1) limiting the duration of laryngoscopy, (2) main- bolic half-life. Complete recovery occurs relatively quickly. taining an appropriate intravascular volume, and (3) using In small doses, states from sedation to unconsciousness may be produced while a quick recovery time is maintained. the available pharmacologic agents carefully. Pharmacologic agents used during intubation include Propofol causes cardiovascular depression, which can result sedatives, muscle relaxants, and local anesthetics. Barbitu- in hypotension in patients with hypovolemia or in debilitated rates, benzodiazepines, and narcotic agents are commonly patients. In addition, pain during injection occurs frequently used for sedation. When administered in small doses, all are if the dose of propofol is not preceded by an intravenous capable of sedation. In large doses, these drugs may result in injection of lidocaine. Ketamine hydrochloride (Ketalar) is a cyclohexylamine, unconsciousness and apnea. Thus, these agents should be administered by a practitioner who is familiar with the ef- a compound chemically related to phencyclidine. Ketamine fects and who is skilled in management of the airway. Seda- produces "dissociative anesthesia," the precise mechanism tion can be considered a continuum-ranging from an alert of which is unknown. After an induction dose of I to 2 mg/ patient to a sedated patient who has spontaneous respirations kg, consciousness is lost and regained in a time frame similar to a patient who has apnea and is unresponsive. As a patient to that with thiopental. When titrated in small doses, ketaprogresses along that continuum, certain advantages-in- mine produces sedation and intense analgesia and maintains creased relaxation, ease of intubation, and blunting of hemo- airway reflexes and respirations. Unlike thiopental and prodynamic responses to intubation-are gained; however, pofol, ketamine stimulates the cardiovascular system indiother advantages-spontaneous respiration- and airway re- rectly; this outcome increases blood pressure and heart rate. flexes-are lost, and sympathetic tone may be decreased. In In addition, ketamine is a powerful bronchodilating agent. some fragile patients, blood pressure and heart rate are main- The cardiovascular and respiratory effects ofketamine make tained by sympathetic tone, and overzealous use of agents it an attractive alternative when sedation or unconsciousness that can attenuate this sympathetic tone may alter hemody- is required in a hemodynamically compromised patient. namics undesirably. The pharmacologic features of com- Disadvantages include an increase in intracranial pressure, monly used agents are summarized in Table 2. (For detailed an increase in myocardial oxygen consumption, and, rarely, information, readers should consult specialized texts.P) hallucinations and dysphoria after a single induction dose.
572
Mayo CUn Proc, June 1992, Vol 67
INTUBATION OF CRITICALLY ILL PATIENTS
Table 2.-Doses and Associated Features of Pharmacologic Agents Commonly Used During Tracheal Intubation Dose*
Onset Immediate Immediate Immediate 3-5 min
Succinylcholine chloride
1-4 mglkg 2-2.5 mglkg 1-2 mglkg Titrate 0.5 mg at a time Titrate 25 ug at a time 1-2 mglkg
Atracurium besylate Vecuronium bromide
0.5 mglkg 0.1 mglkg
Agent Thiopental sodium Propofol Ketamine hydrochloride Midazolam hydrochloride Fentanyl citrate
Duration of action; metabolic half-life'[
Primary route of metabolism Hepatic Hepatic Hepatic Hepatic
Minutes
10 min; 8-12 h 8 min; 5-8 h 10 min; 2-4 h Dose-dependent; 2-4h Dose-dependent
Seconds
5 min
1-5 min 1-5 min
20-30 min; 20-25 min 25-40 min; 65-70 min
Serum pseudocholinesterase Hofmann elimination Hepatic
Hepatic
*Administered intravenously. tConsiderable patient variation exists.
Midazolam hydrochloride (Versed), a benzodiazepine, used alone or in combination with a narcotic agent is an excellent drug for sedation. The drug can be titrated to effect, 0.5 mg administered at a time. After an intravenously administered dose, the sedative effect occurs in 3 to 5 minutes. Advantages of midazolam include reliable sedation and anterograde amnesia. Disadvantages include respiratory and cardiovascular depression, especially if used in combination with other agents. Fentanyl citrate (Sublimaze) is a powerful narcotic analgesic; 100 ug of fentanyl is approximately equivalent to 10 mg of morphine. After a 100-fJ.g dose of fentanyl, the analgesic, sedative, and respiratory depressant effects are almost immediate, and maximal effects occur in several minutes. The duration of analgesia and sedation of a lOO-fJ.g dose is approximately 1 hour; however, the respiratory depressant effect may remain for a longer period. In small doses, titrated carefully, fentanyl produces sedation and can blunt some of the hemodynamic alterations associated with intubation. Like other narcotic agents, high doses of fentanyl will result in respiratory depression. Cardiovascular stability is maintained with fentanyl; however, hypotension may ensue because of the production of bradycardia and the blunting of sympathetic outflow. Fentanyl has an advantage over morphine in that it does notcause the release of histamine. Muscle relaxants can be useful adjuncts in selected patients; they add to the ease of visualization and limit the possible hemodynamic changes and hypoxemia that can be associated with intubation. These agents should not be used for intubation, however, unless a skilled practitioner is present. The two general classes of muscle relaxants are depolarizers and nondepolarizers. These agents can facilitate intubation by eliminating patient movement and muscle tension. Because they do not cause sedation, they should not be used in the absence of a sedative. Complete relaxation is unneces-
sary for intubation, and a fraction of the paralyzing dose will usually suffice. Succinylcholine chloride (Anectine) is a depolarizing muscle relaxant. After an intubating dose of 1 to 2 mg/kg, fasciculations occur within seconds, and then relaxation of the muscles ensues. Succinylcholine is currently the only muscle relaxant that produces rapid relaxation of the muscles followed by quick recovery; however, it has several side effects and contraindications, including hyperkalemia in patients with extensive bums, trauma, and various neurologic diseases. In addition, succinylcholine is a triggering agent for malignant hyperthermia. Atracurium besylate and vecuronium bromide are nondepolarizing muscle relaxants. After an intubating dose (0.5 mg/kg and 0.1 mg/kg, respectively), paralysis is achieved in 1 to 5 minutes. Atracurium is shorter acting than vecuronium and has the advantage of metabolism by Hofmann elimination, a nonbiologic process influenced by pH and temperature. Rapid injection of atracurium can result in hypotension attributed to release of histamine. In contrast, investigators believe that vecuronium is devoid of cardiovascular side effects. The use of these agents may be appropriate when delayed onset of action and prolonged paralysis are not a concern. Local anesthetics topically applied to the nasal mucosa or to the oropharynx and trachea (or to all three) can be used independently or as adjuncts to other pharmacologic agents to minimize hemodynamic alterations and to increase ease of intubation by improving patient comfort and decreasing patient movement. Topical application of an anesthetic agent to the mucous membranes can result in absorption of a considerable amount of the agent. Because the amount of local anesthetic delivered by spray varies, care should be exercised to minimize the dose. The maximal recommended dose of lidocaine is 4 mg/kg.
Mayo CUn Proc, June 1992, Vol 67
MINIMIZATION OF RISKS OF ASPIRATION Since the original description by Mendelson," aspiration of gastric contents has been a feared complication in management of the airway. The potential for aspiration should always be addressed and minimized in patients who require intubation. Patients are at risk for aspiration when (1) the level of consciousness is decreased to such an extent that airway reflexes are blunted or lost; (2) the protective gastroesophageal antireflux mechanisms are impaired, such as when a hiatal hernia or nasogastric tube is present; (3) gastric emptying is delayed or an ileus occurs; or (4) the stomach is full. The key maneuver in the management of patients thought to be at risk for aspiration is application of pressure on the cricoid cartilage with the thumb and index finger, as described by Sellick.'? By placing the other hand behind the patient's neck, greater stability is achieved. Because the cricoid cartilage is a circular cartilaginous ring, the esophagus is compressed between the cricoid cartilage and the vertebral body; this structural relationship occludes the esophagus, prevents passive regurgitation, and minimizes gastric distention from positive-pressure ventilation (Fig. 1). The maneuver is also effective in preventing passive regurgitation in the presence of a nasogastric tube I I and during ventilation with a mask. Pressure on the cricoid cartilage should be maintained until proper placement of the tracheal tube is confirmed. In conscious patients at risk for aspiration, only two intubation options exist: (1) the awake intubation and (2) the rapid sequence intubation. The awake intubation has the advantage of maintaining airway reflexes and spontaneous respirations. When a difficult intubation is anticipated, an awake intubation through the nasal or oral route is preferred over a rapid sequence intubation. The technique is safe, and with careful use of sedation and topically applied anesthetic agents, it is tolerable. Local anesthetic agents can be used to blunt the gag reflex of an awake patient. As long as the area beneath the vocal cords is not anesthetized, the cough reflex is preserved; this factor serves as a safeguard if any regurgitated material enters the trachea. For an awake nasal intubation, a vasoconstrictor (for example, phenylephrine spray) should be applied to the nasal mucosa before the tracheal tube is inserted, to decrease the risk of hemorrhage and to minimize the systemic uptake of local anesthetic agents. - The pharynx and nasal mucosa are topically anesthetized. With the patient breathing spontaneously, the endotracheal tube can then be passed blindly into the trachea. If the procedure is initially unsuccessful, a suction catheter can sometimes be inserted into the trachea first and used as a guide for the endotracheal tube. If intubation is still unsuccessful, the endotracheal tube can be visualized orally and can be manipulated with Magill's for-
INTUBATION OF CRITICALLY ILL PATIENTS
573
Fig. 1. Diagram showing Sellick maneuver-pressure on cricoid cartilage compresses esophagus and prevents passive regurgitation. (See text for further discussion.)
ceps. A fiberoptic laryngoscope or bronchoscope can be helpful when initial attempts at oral or nasal intubation fail. The alternative to the awake intubation in a patient deemed at risk for aspiration is the rapid sequence technique. It has the advantage of eliminating patient movement and thereby facilitating intubation. The rapid sequence technique should not be performed in a patient who is expected to be difficult to intubate, nor should it be performed by inexperienced personnel. The rapid sequence intubation consists of rapidly administering an induction dose of an anesthetic agent (for example, 4 mg/kg of thiopental) immediately followed by a paralyzing dose of succinylcholine (1 to 2 mg/kg). Pressure is applied to the cricoid cartilage by an assistant as the patient loses consciousness. Oxygen is administered to the patient's face until immediately before intubation, but the patient is not ventilated after unconsciousness occurs. After the fasciculations associated with succinylcholine subside, the endotracheal tube is introduced orally into the trachea; its
574
Mayo Clin Proc, June 1992, Vol 67
INTUBATION OF CRITICALLY ILL PATIENTS
Emergent intubation
Elective intubation
1
t
Oral intubation
Risk of aspiration?
I
Yes f-(
~> No t
t
Difficult intubation?
t
Difficult intubation?
'-------.-» Yes f-(
No
Advan;age of rapid sequence? --~> No
t
~
----J
1
Awake f - - No intubation
Yes
t
Rapid sequence
Contraindication to nasal intubation?
t
t
Attempt oral intubation f-
1
1
Failed?
Failed?
t
t
Induction agent + muscle relaxant
I
1
Advan;age of muscle relaxation? Yes
1
Yes~No
Oral or nasal intubation
t
Attempt blind nasal intubation
Oral or nasal intubation
Failed?
Failed?
1
t
t
t
Ventilate with pressure on cricoid cartilage (consider options)
Direct ~ visualization
1
t
Failed?
Cannot ventilate
t
f-(- - -
t
No
Transtracheal ventilation versus cricothyrotomy
1
Fiberoptic ' - - - - - - - t intubation (or other)
f--------J
Fig. 2. Algorithm for intubation of critically ill patients.
presence is confirmed by auscultation, first over the epigastrium to rule out esophageal intubation and then over the chest to verify tracheal intubation. Pressure can then be released, and ventilation can be initiated. The esophageal placement of an endotracheal tube must be recognized. Unfortunately, commonly used methods to detect esophageal placement are suboptimal. 12 Visualization of the endotracheal tube passing through the glottis is not always possible and does not ensure against dislodgment before ventilation. The presence of breath sounds, chest movement, tube misting, and negative epigastric sounds can be misleading. End-tidal carbon dioxide monitoring has been used reliably to confirm correct placement of the endotracheal tube. Because no single clinical detection method is foolproof, more than one should be used. If any doubts arise, the endotracheal tube should be replaced or end-tidal carbon dioxide monitoring should be used. After the induction agent and the muscle relaxant are administered in the rapid sequence intubation, the patient will be paralyzed and unconscious for approximately 10
minutes. If an oral intubation cannot be accomplished, the patient should be ventilated while pressure is maintained on the cricoid cartilage. If ventilation is possible, other methods of intubation can be explored-for example, fiberoptic intubation-while the induction agent and the succinylcholine are metabolized. If ventilation is impossible, transtracheal jet ventilation, emergent cricothyrotomy, or tracheostomy may be necessary. Regurgitation can occur even when proper measures are taken. If regurgitation occurs, the patient should be placed in a head-down position, with head (and body) turned to the side. Regurgitated material should be immediately suetioned from the mouth. If pressure is being applied to the cricoid cartilage when active emesis occurs, it should be released, and the aforementioned sequence performed. Intubation should be done as soon as possible. FORMULAnON OF A PLAN The algorithm illustrated in Figure 2 provides an outline for the practitioner preparing to intubate. Key decisions include
Mayo Clin Proc, June 1992, Vol 67
whether the situation is urgent or elective, whether the risk of aspiration is substantial, and whether any difficulty is anticipated during the procedure. An urgent situation-for example, a cardiac arrest-is perhaps the most straightforward. The patient is unconscious and has little muscle tone. Pharmacologic agents are unnecessary. Intubation should be performed expediently through the oral route. The semielective intubation presents a challenge because, typically, preexisting abnormalities of the airway or gas exchange exist. For intubation of critically ill patients, the anticipated difficulty of the procedure should be assessed, as well as the potential for aspiration. If the patient is at risk for aspiration, the choice is either an awake intubation or a rapid sequence intubation. If the intubation is potentially difficult, the awake technique is preferred. In a conscious patient without expected complications, an induction agent followed by a muscle relaxant is an appropriate alternative. Several options are available for patients who cannot be intubated by conventional means. After a failed intubation, a reasonable first step is to have an anesthesiologist assess the airway, and then the intubation should be reattempted. If one has the necessary skills, a fiberoptic laryngoscope or bronchoscope is a good first or second alternative in those patients who have a difficult airway or who are at risk for aspiration. 13 When a patient with apnea cannot be intubated by available means and cannot be adequately ventilated by mask, an emergent cricothyrotomy or tracheostomy can be lifesaving. Because few physicians have the technical expertise to perform a tracheostomy in an emergency, needle cricothyrotomy is a reasonable alternative. Needle cricothyrotomy is accomplished by percutaneously passing a 14-gauge catheter through the cricothyroid membrane into the trachea (Fig. 3). While advancing the 14-gauge intravenous catheter and aspirating into a fluid-filled syringe, the physician can identify the trachea by the aspiration of air. The catheter is passed off the needle into the trachea in a caudal direction. Then, if available, a transtracheal jet ventilation system or similar delivery device that uses a high-flow, high-pressure source can be attached." If these specialized devices are unavailable, a 3-mJ syringe with plunger removed can be attached to the transtracheal catheter, which is attached to a self-inflating or anesthesia bag by means of a 7.0-mm endotracheal tube connector. An alternative connection from transtracheal catheter to ventilation bag can be obtained by using an endotracheal tube with cuff inflated in a 12-ml syringe. IS Because of the resisting limitations of a 14-gauge catheter, ventilation with an anesthesia or self-inflating bag will be difficult; however, in an emergency, needle cricothyrotomy can be a life-sustaining measure until specialized equipment and personnel arrive.
INTUBATION OF CRITICALLY ILL PATIENTS
575
Fig. 3. Diagram illustrating needle cricothyrotomy, in which catheter is passed percutaneously through cricoid membrane into the trachea.
After tracheal intubation is accomplished, the timing of tracheostomy is controversial. Tracheostomy increases patient comfort and may prevent laryngeal injury that can result from prolonged translaryngeal intubation. Tracheostomy is commonly considered if the duration of intubation exceeds 21 days and if continued support is expected." Because the course of each patient is often unpredictable, daily assessment is needed. CONCLUSION In critically ill patients, the transition from the nonintubated state to the intubated state is a delicate period. Hypoxia is minimized by preoxygenation and by performing intubation as quickly as possible. The hemodynamic changes associated with intubation and positive-pressure ventilation can be attenuated by limiting the duration of laryngoscopy, carefully maintaining intravascular volume, and selecting appropriate pharmacologic agents. Aspiration is decreased by recognizing patients who are prone to aspiration and by
576
Mayo Clin Proc, June 1992,Vol 67
INTUBATION OF CRITICALLY ILL PATIENTS
using the available techniques to minimize this risk. The formulation of a plan with the aforementioned goals will allow the safe institution of a valuable mode of therapy for critically ill patients. REFERENCES 1. Finucane BT, Santora AH: Principles of Airway Management. Philadelphia, FA Davis Company, 1988 2. Dauphinee K: Orotracheal intubation. Emerg Med Clin North Am 6:699-713, November 1988 3. White A, Kander PL: Anatomical factors in difficult direct laryngoscopy. Br J Anaesth 47:468-473, 1975 4. Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B; Freiberger D, Liu PL: A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 32:429-434, 1985 5. Berthoud M, Read DH, Norman J: Pre-oxygenation-how long? Anaesthesia 38:96-102,1983 6. Stoelting RK: Circulatory changes during direct laryngoscopy and tracheal intubation: influence of duration of laryngoscopy with or without prior lidocaine. Anesthesiology 47:381-384, 1977 7. Gilman AG, Goodman LS, Gilman A (eds): Goodman and Gilman's The Pharmacological Basis of Therapeutics. Sixth edition. New York, Macmillan Publishing Company, 1980
8.
Barash PG, Cullen BF, Stoelting RK (eds): Clinical Anesthesia. Philadelphia, JB Lippincott Company, 1989 9. Mendelson CL: The aspiration of stomach contents into the lungs during obstetric anesthesia. Am J Obstet Gynecol 52:191-204,1946 10. Sellick BA: Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia. Lancet 2:404-406, 1961 11. Salem MR, Joseph NJ, Heyman HJ, Belani B, Paulissian R, Ferrara TP: Cricoid compression is effective in obliterating the esophageal lumen in the presence of a nasogastric tube. Anesthesiology 63:443-446, 1985 12. Birmingham PK, Cheney FW, Ward RJ: Esophageal intubation: a review of detection techniques. Anesth Analg 65:886-891, 1986 13. Ovassapian A, Krejcie TC, Yelich SJ, Dykes MHM: Awake fibreoptic intubation in the patient at high risk of aspiration. Br J Anaesth 62:13-16, 1989 14. Scuderi PE, McLeskey CH, Comer PB: Emergency percutaneous transtracheal ventilation during anesthesia using readily available equipment. Anesth Analg 61:867-870, 1982 15. Gildar JS: A simple system for transtracheal ventilation (letter to the editor). Anesthesiology 58: 106, 1983 16. Plummer AL, Gracey DR: Consensus conference on artificial airways in patients receiving mechanical ventilation. Chest 96: 178-180, 1989