Prehospital Bicarbonate Use in Cardiac Arrest: A 3-Year

Experience

TOM P. AUFDERHEIDE, MD, DANIEL R. MARTIN, MD, DAVID W. OLSON, MD, CHARLES APRAHAMIAN, MD,* JOSEPH W. WOO, GAIL E. HENDLEY, MD, KATHLEEN M. HARGARTEN, MD, BRUCE THOMPSON,

The American Heart Association no longer recommends the routine use of sodium bicarbonate in cardiac arrests. Reasons cited include the lack of documented effect on clinical outcome and potential adverse effects of metabolic alkalosis and hypernatremia. We reviewed 36 months of experience with 619 nontrauma adult, prehospital cardiac arrest patients to identify 273 successful resuscitations who had emergency department blood gases and electrolytes performed. Determination of complications associated with prehospital intravenous sodium bicarbonate and its impact on survival in resuscitated patients was undertaken. Fifty-eight patients did not receive sodium bicarbonate (NO HCOI group) and had short cardiopulmonary resuscitation (CPR) times (7.4 f 6.6 minutes). Two hundred fifteen patients did receive sodium bicarbonate (HCOB group) and had significantly longer CPR times (23.3 f 13.5 minutes, P < .OOl). Both groups demonstrated routine early chest compression and hyperventilation as evidenced by no significant difference in paramedic response time or rate of intubations. Initial emergency department blood gas results of both groups were not significantly different. No patients in the NO HCOI group had hypernatremia (sodium [Na]’ > 150), whereas four patients (2%) in the HCOI group were hypernatremic. Eight patients (14%) in the NO HC03 group and 37 patients (17%) in the HCO, group were alkalotic with pH values greater than 7.49 (P = NS). Six patients (10%) of the NO HCOI group and 24 patients (11%) of the HCO, group had a metabolic component to the alkalosis as defined by a positive base excess value (P = NS). Survival was examined in both groups following standardization for the presenting rhythm of ventricular fibrillation and CPR time intervals of 5 minutes. Survival did not differ significantly between the NO HCO, group and the HCO:, group during any CPR time interval. However, base changes were significantly improved in the 15 to 20 minute CPR time interval (P G .06). Because only resuscitated patients were evaluated in this study, no determination could be made regarding bicarbonate’s influence on survival following cardiac arrest. We describe the incidence of alkalosis, metabolic alkalosis, hypernatremia, and survival in patients receiving HCOI and not receiving HCOB who were successfully resuscitated from prehospital cardiac arrest. (Am J Emerg Med 1992;10:4-7. Copyright 1992 by W.B. Saunders Company)

From the Departments of Emergency Medicine and ‘Trauma Surgery, Medical College of Wisconsin, Milwaukee, WI; and the tDepartment of Emergency Medicine, Henry Ford Hospital, Detroit, MI. Manuscript received November 19, 1990; revision June 24, 1991. Presented at The Annual University Association for Emergency Medicine, Philadelphia, PA, May 19-21, 1987. Address reprint requests to Dr Aufderheide, Milwaukee County Medical Complex, Department of Emergency Medicine, 8700 W. Wisconsin Ave, Box 204, Milwaukee, WI 53226. Key Words: Cardiac arrest, sodium bicarbonate, blood gases, metabolic alkalosis, hypernatremia. Copyright 0 1992 by W.B. Saunders Company 0735-6757/92/1001-0002$5.00/O

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The American Heart Association (AHA) has emphasized the importance of hyperventilation to control metabolic acidosis resulting from cardiac arrest,’ and effective in 1986. has not recommended intravenous sodium bicarbonate for routine use following cardiac arrest.’ Reasons cited include the ability to maintain acid base balance in dogs by hyperventilation and chest compression alone,3 as well as potential adverse effects (metabolic alkalosis and hypernatremia) that could result from the use of sodium bicarbonate. Since no prospective clinical studies have been performed to support the AHA’s recommendations, we undertook this retrospective study to evaluate the prehospital use of intravenous sodium bicarbonate in cardiac arrest patients to determine the incidence of adverse metabolic effects of sodium bicarbonate. Data prior to 1985 was chosen for review, because the protocol in effect at that time allowed for liberal and early use of sodium bicarbonate in cardiac arrest. METHODOLOGY The Milwaukee County Emergency Medical Service (Milwaukee, WI) system is a tiered urban paramedic system that has been previously described in other publications.4.” In Milwaukee’s tiered response system, basic and advanced level emergency medical technicians are simultaneously dispatched to the scene. The first to arrive performs an assessment and, with the diagnosis of cardiac arrest, cardiopulmonary resuscitation (CPR) is provided. The paramedic squads initiate AHA guidelines regarding defibrillation, intubation, intravenous access, and administration of appropriate drugs. During the study period, the paramedic’s protocol called for sodium bicarbonate administration prior to base physician contact. Base physicians were encouraged to administer sodium bicarbonate approximately every 10 minutes until the return of spontaneous circulation. During a 36-month period ending December 31. 1984, the computerized records of the Milwaukee County Paramedic System were reviewed to identify those patients with nontraumatic, nonpoisoned adult (over 18 years) cardiac arrests who were seen and managed by paramedics using the AHA guidelines for resuscitation. Demographic and treatment information was obtained for each patient. Successfully resuscitated patients had blood work performed in the receiving emergency department, and data regarding blood gases and serum electrolytes were obtained and recorded. Paramedic response time, defined as the time of dispatch to arrival of paramedics at the scene, and CPR time, defined

AUFDERHEIDE

ET AL n PREHOSPITAL

BICARBONATE

USE IN CARDIAC

as the duration of CPR from the arrival time of the paramedics to development of an organized rhythm and palpable pulse, were noted. The CPR time does not include time prior to paramedic arrival. If the patient’s condition deteriorated in the field and CPR was again required, the additional time of CPR provision was added to the original CPR time. In effect, the total CPR time reflects nonperfusion time after the paramedics’ arrival at the scene. Successful resuscitations, defined as patients transported to hospital emergency departments with a perfusing rhythm, and saves, defined as those discharged alive from the hospital, were recorded. Base change was calculated using standard Advanced Cardiac Life Support guidelines.6 Alkalosis of any type is defined as a pH greater than 7.49. Metabolic alkalosis is defined as a pH greater than 7.49 and a calculated positive base excess value. Hypernatremia is defined as a serum sodium greater than 150. Data were analyzed by Student’s f-test, x2, Fisher exact test, or curvilinear analysis as deemed appropriate. P-values were considered significant if less than .05. RESULTS Six hundred nineteen consecutive nontrauma, nonpoisoned, adult, prehospital cardiac arrest patients were identified as having received resuscitative efforts in Milwaukee County from January 1, 1982 through December 3 1, 1984. Of the 619 patients, 350 were successfully resuscitated and 269 were not successfully resuscitated. Two hundred seventythree of the 350 successfully resuscitated patients had emergency department arterial blood gases and serum electrolytes performed. Fifty-eight patients were quickly resuscitated after paramedic arrival and because of short CPR times were determined by the attending base physician not to require intravenous sodium bicarbonate (NO HCO, group). Two hundred fifteen patients had longer CPR times and received sodium bicarbonate via the pre-1985 AHA protocol (HCO, group). Seventy-seven of the 350 successfully resusTABLE 1.

Successfully Resuscitated NO HC03 Versus HCO,

Parameter

Age Sex (M:F) Estimated time down (min) Response time (min) CPR time (min) Pco, % lntubated PNB rhythms: VF EMD Asystole VT

Patient

Characteristics:

NO HCO, (n = 58)

HCO, (n=215)

65? 2:l

672 2:l

12

0 pH > 7.49 and positive base change Na+ > 150 Abbreviation:

JOURNAL

OF EMERGENCY

NO HCO, (n = 58)

HCO, (n = 215)

P

8 (13.8%) 12 (20.7%)

37 (17.2%) 40 (18.6%)

NS NS

6 (10.3%) 0 (0%)

24 (11.2%) 4 (1.9%)

NS NS

In 1986, the AHA changed the guidelines for bicarbonate use in cardiac arrest patients based on concerns of hypernatremia, hyperosmolarity, metabolic alkalosis, and paradoxical worsening of tissue acidosis.* There was lack of evidence supporting improved clinical outcome with its use. In this study, no clinically significant increase in side effects including hypernatremia and metabolic alkalosis were observed in resuscitated patients given sodium bicarbonate. There was. however, evidence that resuscitated patients with long CPR times who were given bicarbonate therapy had less severe acidosis. Prognosis in the field has been related to initial presenting arrest rhythm (with the best prognosis occurring in patients presenting in coarse VF) and to the time required for the return of spontaneous circulation.“’ Therefore, survival in this study was examined after standardization for the presenting initial rhythm of VF in conjunction with CPR time. No significant difference in survival rate of resuscitated patients was found when comparing the NO HCO, group with the HCO, group. Studies investigating lactic acidosis emphasize the lack of benefit in dogs treated and not treated with sodium bicarbonate. 8,9 Although implications have been

o-5 5-10 10-15 15-20

10, Number

1 m January

1992

CPR Time (min) o-5 5-10 10-15 15-20

NO HCO,

HCO,

PH

Base Change

pH

7.41 7.39 7.39 7.35

- 3.95 -3.47 -6.29 -10.11

7.38 7.36 7.41 7.39

Base Change

-

3.67 3.52 4.33 4.45

P-Value NS NS .12 5.05

Na, sodium.

DISCUSSION

CPR Time (min)

m Volume

TABLE 5. pH and Base Change in Ventricular Fibrillation Patients With Similar Cardiopulmonary Resuscitation Time

and Hypernatremia

compared with the HCO, group in 5-minute intervals. Survival did not differ significantly between the NO HCO, group and the HC03 group during any CPR time interval. Within the same groups as those presented in Table 4, the pH and base changes were compared (Table 5). Although the base changes were not different in patients with CPR times of O-5 minutes, 5-10 minutes, or IO-15 minutes, the difference was statistically significant (x2) during the CPR time interval of 15-20 minutes. On average, sodium bicarbonate was administered 8.9 minutes following paramedic arrival. These data indicate that metabolic acidosis of lesser severity occurred in resuscitated patients receiving sodium bicarbonate within less than IO minutes after paramedic arrival, with accompanying CPR times greater than 15 minutes.

TABLE 4.

MEDICINE

Survival

(Ventricular

NO HCO, 15/l 9 14117 416 3/6

(79%) (82%) (67%) (50%)

Fibrillation

Only)

HCO, 4/5 13120 12/l 8 12/30

(80%) (65%) (67%) (40%)

P NS NS NS NS

made that alkali therapy may be deleterious,3 no clinical studies confirming this are available. It is generally agreed that severe metabolic acidosis has several cardiac disadvantages. Gerst et al reported that the VF threshold was decreased in dogs when metabolic acidosis was induced and increased during metabolic alkalosis.‘(’ These changes were not reversed with respiratory hyperventilation but could be normalized following sodium bicarbonate infusion. Redding and Pearson reported maximum defibrillation rates in dogs given combinations of epinephrine and sodium bicarbonate.” Our study showed a significantly less severe metabolic acidosis in resuscitated patients receiving sodium bicarbonate with CPR times of 15-20 minutes. Alkalosis is mentioned as a deleterious side effect of bicarbonate administration in the current AHA standards and guidelines.* Supraventricular arrhythmias (atria1 tachycardia, nodal tachycardias, atrioventricuiar or junctional dissociation with or without tachycardia) may develop as a consequence of profound alkalosis.‘* Ventricular arrhythmias are rare. ” A possible explanation for alkalosis-induced supraventricular arrhythmias is a coexisting fall in serum potassium levels.‘3-‘5 In this study the incidence of alkalosis and metabolic alkalosis in successfully resuscitated patients was not increased in the HCO, group. Animal studies indicate that increases in plasma osmolality greater than 350 mOsm are potentially fatal.“-” The precise incidence of bicarbonate-induced hypernatremia and its detrimental affects on resuscitation outcome remain unknown. In our study, there was no significant difference in average sodium levels in patients treated and not treated with intravenous sodium bicarbonate. The incidence of hypernatremia (sodium greater than 150) in patients receiving intravenous bicarbonate was low (1.9%). This study is limited in that prehospital data was retrospectively collected from a small sample size of 273 patients. A rigid protocol of sodium bicarbonate administration was not evaluated prospectively. In addition, laboratory data were collected from different emergency departments with no method of absolutely confirming that samples were arterial (eg, radial artery cutdown). Those patients who never had return of spontaneous circulation in the field did not have laboratory tests acquired, and could not be included in the evaluation. It should be emphasized that the patients included in this study represent only the subset of prehospital cardiac arrest victims who were resuscitated. For this reason, the influence of sodium bicarbonate on survival rate in all cardiac arrest patients (resuscitated and nonresuscitated) could not be determined.

AUFDERHEIDE

ET AL m PREHOSPITAL

BICARBONATE

USE IN CARDtAC ARREST

There was no evidence that sodium bicarbonate positively or negatively influenced survival in resuscitated patients. A factor which may serve to normalize acid base status is prolonged time from return of spontaneous circulation to the time laboratory data is obtained. In this study, the mean time from return of spontaneous circulation in the field to arterial blood gas sampling at the receiving emergency department was 39.5 minutes. This factor could have permitted time for pulmonary compensation of acid base alterations.7.21.22 The most appropriate manner to use sodium bicarbonate during cardiac arrest is unknown. In this retrospective study, the use of sodium bicarbonate within 10 minutes of paramedic arrival was not associated with any statistically significant increase in adverse effects, based on emergency department evaluation in patients with return of spontaneous circulation. CONCLUSION We describe the incidence of alkalosis, metabolic alkalosis, hypernatremia, and survival in patients receiving HCO, and not receiving HCO, who were successfully resuscitated from prehospital cardiac arrest. A prospective clinical study including both resuscitated and nonresuscitated patients (controlling the timing of blood sampling and the patient populations) is required to determine the optimal use of sodium bicarbonate during cardiac arrest. The authors gratefully acknowledge the time, effort, and assistance contributed toward the successful completion of this research endeavor by Dennis Birchall, MD and Cindi Marquette, MD.

REFERENCES 1. Standards and guidelines for CPR and ECC. JAMA 1980; 244:479-494 2. Standards and guidelines for CPR and ECC. JAMA 1986; 255:2933-2951 3. Bishop RL, Weisfeldt ML: Sodium bicarbonate administration during cardiac arrest. JAMA 1976;235:505-509 4. Stueven H, Troiano P, Thompson B, et al: Bystander/first responder CPR: Ten years’ experience in a paramedic system. Ann Emerg Med 1986;15:707-710

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5. Pionkowski RS, Thompson BM, Gruchow HW, et al: Resuscitation time in ventricular fibrillation-A prognostic indicator. Ann Emerg Med 1983;12:733-738 6. Textbook of Advanced Cardiac Life Support. American Heart Association, 1983, pp 135-140 7. Ornato JP, Gonzalez ER, Loyne MR, et al: Arterial pH in out of hospital cardiac arrest: Response time as a determinant of acidosis. Am J Emerg Med 1985;3:498-502 8. Stacpoole PW: Lactic acidosis: The case against bicarbonate therapy. Ann Intern Med 1986;105:276-279 9. Guerci AD, Chandra N, Johnson E, et al: Failure of sodium bicarbonate to improve resuscitation from ventricular fibrillation in dogs. Circulation 1986;74:75-79 (suppl IV) 10. Gerst PH, Fleming WH, Malm JR: A quantitative evaluation of the effects of acidosis and alkalosis upon the ventricular fibrillation threshold. Surgery 1966;59:1050-1060 11. Redding JS, Pearson JW: Resuscitation from ventricular fibrillation. JAMA 1968;203:93-98 12. Lawson NW, Butler GH, Ray CT: Alkalosis and cardiac arrhythmias. Cur Res 1973;52:951-964 15. Andersen MN, Suane H: Pattern of biochemical response to acute chanoes in Pco,. Ann Sura 1962;156:752-758 14. Hall KDyReese FH_ Serum potassium levels in hyperventilated dogs. Proc Sot Exp Biol Med 1962;111:251-252 15. Flemma RJ, Young WG Jr: The metabolic effects of mechanical ventilation and respiratory alkalosis in post-operative patients. Surgery 1964;56:36-43 16. Winkler AW, Elkinton JR, Hopper J Jr, et al: Experimental hypertonicity; alterations in the distribution of body water, and the cause of death. J Clin Invest 1944:23:103-109 17. Kravath RE, Aharon AS, Abal G, et al: Clinically significant physiologic changes from rapidly administered hyp&tonic solutions: Acute osmol ooisonina. Pediatrics 1970:46:267-275 18. Pool RR: Acite orally-induced hypernairemia in the rat: Pathomorphologic and pathophysiologic changes. Am J Vet Res 1970;31:2261-2274 19. Sotos JF, Dodge PR, Meara P, et al: Studies in experimental hypertonicity. I. Pathogenesis of the clinical syndrome, biochemical abnormalities and cause of death. Pediatrics 1960;26: 925-938 20. Mattar JA, Weil MH, Shubin H, et al: Cardiac arrest in the critically ill. II. Hyperosmolal states following cardiac arrest. Am J Med 1974;56:162-168 21. Fillmore SJ, Shapiro M, Kitlip T: Serial blood gas studies during cardiopulmonary resuscitation. Ann intern Med 1970;72: 465-469 22. von Planta M, Weil MH, Gazmuri RJ, et al: Myocardial acidosis associated with CO, production during cardiac arrest and resuscitation. Circulation 1989;80:684-692

Prehospital bicarbonate use in cardiac arrest: a 3-year experience.

The American Heart Association no longer recommends the routine use of sodium bicarbonate in cardiac arrests. Reasons cited include the lack of docume...
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