Comparison of sodium bicarbonate, Carbicarb, and THAM during cardiopulmonary resuscitation in dogs

Sodium Bicarbonate and Calcium Chloride for the Treatment of Hyperkalemia-Induced Cardiac Arrest: A Randomized, Blinded, Placebo-Controlled Animal Study

OBJECTIVES

Current international guidelines recommend administrating calcium chloride and sodium bicarbonate to patients with hyperkalemia-induced cardiac arrest, despite limited evidence. The aim of this study was to evaluate the efficacy of calcium chloride and sodium bicarbonate on return of spontaneous circulation (ROSC) in a pig model of hyperkalemia-induced cardiac arrest.

DESIGN

A randomized, blinded, placebo-controlled experimental pig study. Hyperkalemia was induced by continuous infusion of potassium chloride over 45 minutes followed by a bolus. After a no flow period of 7 minutes, pigs first received 2 minutes of basic cardiopulmonary resuscitation and subsequently advanced life support. The first intervention dose was administered after the fifth rhythm analysis, followed by a defibrillation attempt at the sixth rhythm analysis. A second dose of the intervention was administered after the seventh rhythm analysis if ROSC was not achieved. In case of successful resuscitation, pigs received intensive care for 1 hour before termination of the study.

SETTING

University hospital laboratory.

SUBJECTS

Fifty-four female Landrace/Yorkshire/Duroc pigs (38-42 kg).

INTERVENTIONS

The study used a 2 × 2 factorial design, with calcium chloride (0.1 mmol/kg) and sodium bicarbonate (1 mmol/kg) as the interventions.

MEASUREMENTS AND MAIN RESULTS

Fifty-two pigs were included in the study. Sodium bicarbonate significantly increased the number of animals achieving ROSC (24/26 [92%] vs. 13/26 [50%]; odds ratio [OR], 12.0; 95% CI, 2.3-61.5; p = 0.003) and reduced time to ROSC (hazard ratio [HR] 3.6; 95% CI, 1.8-7.5; p < 0.001). There was no effect of calcium chloride on the number of animals achieving ROSC (19/26 [73%] vs. 18/26 [69%]; OR, 1.2; 95% CI, 0.4-4.0; p = 0.76) or time to ROSC (HR, 1.5; 95% CI, 0.8-2.9; p = 0.23).

CONCLUSIONS

Administration of sodium bicarbonate significantly increased the number of animals achieving ROSC and decreased time to ROSC. There was no effect of calcium chloride on the number of animals achieving ROSC or time to ROSC.

Fluid Therapy During Cardiopulmonary Resuscitation

Cardiopulmonary arrest (CPA), the acute cessation of blood flow and ventilation, is fatal if left untreated. Cardiopulmonary resuscitation (CPR) is targeted at restoring oxygen delivery to tissues to mitigate ischemic injury and to provide energy substrate to the tissues in order to achieve return of spontaneous circulation (ROSC). In addition to basic life support (BLS), targeted at replacing the mechanical aspects of circulation and ventilation, adjunctive advanced life support (ALS) interventions, such as intravenous fluid therapy, can improve the likelihood of ROSC depending on the specific characteristics of the patient. In hypovolemic patients with CPA, intravenous fluid boluses to improve preload and cardiac output are likely beneficial, and the use of hypertonic saline may confer additional neuroprotective effects. However, in euvolemic patients, isotonic or hypertonic crystalloid boluses may be detrimental due to decreased tissue blood flow caused by compromised tissue perfusion pressures. Synthetic colloids have not been shown to be beneficial in patients in CPA, and given their documented potential for harm, they are not recommended. Patients with documented electrolyte abnormalities such as hypokalemia or hyperkalemia benefit from therapy targeted at those disturbances, and patients with CPA induced by lipid soluble toxins may benefit from intravenous lipid emulsion therapy. Patients with prolonged CPA that have developed significant acidemia may benefit from intravenous buffer therapy, but patients with acute CPA may be harmed by buffers. In general, ALS fluid therapies should be used only if specific indications are present in the individual patient.

Effects of sodium pyruvate on ameliorating metabolic acidosis

OBJECTIVE

To examine the effects of sodium pyruvate (SP) on metabolic acidosis.

METHODS

For the in vivo experiments, we evaluated effects of SP on an ammonium chloride (NH4Cl)-induced hyperchloremic acidosis rat model. SP was infused at overall doses of 2, 4, and 6 mmol·kg(- 1) for the SP1, SP2, and SP3 groups, respectively. Treatment with sodium bicarbonate (SB) was used as a positive control (2 mmol·kg(- 1)), and treatment with normal saline (NS) was used as a volume control (2 mL·kg(- 1)). Blood was sampled from the ophthalmic venous plexus for pH, blood gases, electrolytes, glucose, creatinine (Cr), and urea analysis after injection. For the in vitro experiment, propionate was applied to induce intracellular acidosis in human endothelial cells. Intracellular pH (pHi) was fluorimetrically measured after the addition of SP.

RESULTS

In the in vivo study, the pH of SP1 group showed no significant difference compared with that of the NS group. The SP2 and SP3 groups had a higher pH than the NS group (P < 0.01). The SP3 group had a higher pH than the SB group (P < 0.05) and SP1 group (P < 0.05). Moreover, SP treatment ameliorated the abnormality of calcium and decreased the blood potassium levels. The SP3 group had higher glucose levels than SP1 group (P < 0.05). No significant differences were observed between all the groups in the plasma Cr and urea levels. In the in vitro study, the pHi increased immediately after the addition of SP.

CONCLUSION

The data suggest that intravascular treatment with SP represents a novel therapeutic strategy to ameliorate metabolic acidosis.

Efficient Extra- and Intracellular Alkalinization Improves Cardiovascular Functions in Severe Lactic Acidosis Induced by Hemorrhagic Shock

Background:

Lactic acidosis is associated with cardiovascular failure. Buffering with sodium bicarbonate is proposed in severe lactic acidosis. Bicarbonate induces carbon dioxide generation and hypocalcemia, both cardiovascular depressant factors. The authors thus investigated the cardiovascular and metabolic effects of an adapted sodium bicarbonate therapy, including prevention of carbon dioxide increase with hyperventilation and ionized calcium decrease with calcium administration.

Methods:

Lactic acidosis was induced by hemorrhagic shock. Twenty animals were randomized into five groups: (1) standard resuscitation with blood retransfusion and norepinephrine (2) adapted sodium bicarbonate therapy (3) nonadapted sodium bicarbonate therapy (4) standard resuscitation plus calcium administration (5) hyperventilation. Evaluation was focused in vivo on extracellular pH, on intracellular pH estimated by P31 nuclear magnetic resonance and on myocardial contractility by conductance catheter. Aortic rings and mesenteric arteries were isolated and mounted in a myograph, after which arterial contractility was measured.

Results:

All animals in the hyperventilation group died prematurely and were not included in the statistical analysis. When compared with sham rats, shock induced extracellular (median, 7.13; interquartile range, [0.10] vs. 7.30 [0.01]; P = 0.0007) and intracellular acidosis (7.26 [0.18] vs. 7.05 [0.13]; P = 0.0001), hyperlactatemia (7.30 [0.01] vs. 7.13 [0.10]; P = 0.0008), depressed myocardial elastance (2.87 [1.31] vs. 0.5 [0.53] mmHg/μl; P = 0.0001), and vascular hyporesponsiveness to vasoconstrictors. Compared with nonadapted therapy, adapted bicarbonate therapy normalized extracellular pH (7.03 [0.12] vs. 7.36 [0.04]; P &lt; 0.05), increased intracellular pH to supraphysiological values, improved myocardial elastance (1.68 [0.41] vs. 0.72 [0.44] mmHg/μl; P &lt; 0.05), and improved aortic and mesenteric vasoreactivity.

Conclusions:

A therapeutic strategy based on alkalinization with sodium bicarbonate along with hyperventilation and calcium administration increases pH and improves cardiovascular function.

Sodium bicarbonate use in shock and cardiac arrest: attitudes of pediatric acute care physicians

OBJECTIVES

To evaluate the preferences and self-reported practices of pediatric acute care physicians with respect to sodium bicarbonate administration to infants and children in shock or cardiac arrest.

DESIGN

National survey study utilizing a self-administered questionnaire.

SETTING

Thirteen Canadian pediatric tertiary care centers.

SUBJECTS

Canadian pediatric critical care physicians, pediatric emergency physicians, and trainees in these subspecialties.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Survey items were evaluated based on Yes/No responses, frequency responses, and Likert scales. Overall response rate was 53% (151/284) with 49.0% (74/151) citing pediatric critical care as their primary practice. 82.0% of respondents (123/150) indicated they would administer sodium bicarbonate as part of ongoing resuscitation for septic shock, whereas 58.3% (88/151) would administer sodium bicarbonate in a cardiac arrest scenario (p=0.004). 47.3% (71/150) selected a pH threshold at or below which they would administer sodium bicarbonate (mean, 6.94±0.013; median, 7.00; range, 6.50-7.20; interquartile range, 6.90-7.00), whereas 20.5% (31/151) selected a base excess threshold (mean, -15.62±0.78; median, -16; range, -20 to -4; interquartile range, -20 to -14). Both pH and duration of resuscitation were strongly associated with the decision to administer sodium bicarbonate (p<0.0001). Respondents' perceptions regarding a colleague's likelihood of administering sodium bicarbonate to the same patient under the same circumstances reflect an acknowledgment of disparate practices with respect to sodium bicarbonate use. 53.0% (79/149) felt current American Heart Association guidelines help them in deciding whether to administer sodium bicarbonate to critically ill patients, and 84% would support a randomized trial.

CONCLUSION

Differences of opinion exist among pediatric acute care physicians with respect to the timing and appropriateness of sodium bicarbonate administration during resuscitation. Most indicated they would support moving forward with a clinical trial.

Slowing of Electrical Activity in Ventricular Fibrillation is Not Associated with Increased Defibrillation Energies in the Isolated Rabbit Heart

Prolonged out-of-hospital ventricular fibrillation (VF) arrests are associated with reduced ECG dominant frequency (DF) and diminished defibrillation success. Partial reversal of ischemia increases ECG DF and improves defibrillation outcome. We have investigated the metabolic components of ischemia responsible for the decline in ECG DF and defibrillation success. Isolated Langendorff-perfused rabbit hearts were loaded with the voltage-sensitive dye RH237. Using a photodiode array, epicardial membrane potentials were recorded at 252 sites (15 mm × 15 mm) on the anterior surface of the left and right ventricles. Simultaneously, a global ECG was recorded. VF was induced by burst pacing, and after 60s, perfusion was either reduced to 6 ml/min or the perfusate composition changed to impose hypoxia (95% N(2)/5% CO(2)), pH 6.7 (80% O(2)/20% CO(2)), or hyperkalemia (8 mM). Using fast Fourier transform, power spectra were created from the optical signals and the global ECG. The optical power spectra were summated to give a global power spectrum (pseudoECG). At 600 s the minimum defibrillation voltage (MDV) was determined by step-up protocol. During VF, the ECG and pseudoECG DF were reduced by low-flow ischemia (9.0 ± 1.0 Hz, p < 0.01, n = 5) and raised [K(+)](o) (12.2 ± 1.3 Hz, p < 0.05, n = 7) compared to control (19.2 ± 1.5 Hz, n = 20), but were unaffected by acidic pH(o) (16.7 ± 1.1 Hz, n = 11) and hypoxia (14.0 ± 1.2 Hz, n = 10). In contrast, the MDV was raised by acidic pH (156.1 ± 26.4 V, p < 0.001) and hypoxia (154.1 ± 22.1 V, p < 0.01) compared to control (65.6 ± 2.3 V), but comparable changes were not observed in low-flow ischemia (61.0 ± 0.5 V) or raised [K(+)](o) (56 ± 3 V). In summary, different metabolites are responsible for the reduction in DF and the increase in defibrillation energy during ischemic VF.

Vascular access and drug therapy in pediatric resuscitation

Using the evidence brought together through the 2005 International Liaison Committee on Resuscitation evidence evaluation process and the subsequent 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, the role for specific drug therapy in pediatric cardiac arrest is outlined. The drugs discussed include epinephrine, vasopressin, calcium, sodium bicarbonate, atropine, magnesium, and glucose. The literature addressing how best to deliver these drugs to the critically ill child is also presented, specifically looking at the use of intraosseous and endotracheal drug therapy.

Drug administration in animal studies of cardiac arrest does not reflect human clinical experience

INTRODUCTION

To date, there is no evidence showing a benefit from any advanced cardiac life support (ACLS) medication in out-of-hospital cardiac arrest (OOHCA), despite animal data to the contrary. One explanation may be a difference in the time to first drug administration. Our previous work has shown the mean time to first drug administration in clinical trials is 19.4min. We hypothesized that the average time to drug administration in large animal experiments occurs earlier than in OOHCA clinical trials.

METHODS

We conducted a literature review between 1990 and 2006 in MEDLINE using the following MeSH headings: swine, dogs, resuscitation, heart arrest, EMS, EMT, ambulance, ventricular fibrillation, drug therapy, epinephrine, vasopressin, amiodarone, lidocaine, magnesium, and sodium bicarbonate. We reviewed the abstracts of 331 studies and 197 full manuscripts. Exclusion criteria included: non-peer reviewed, all without primary animal data, and traumatic models. From these, we identified 119 papers that contained unique information on time to medication administration. The data are reported as mean, ranges, and 95% confidence intervals. Mean time to first drug administration in animal laboratory studies and clinical trials was compared with a t-test. Regression analysis was performed to determine if time to drug predicted ROSC.

RESULTS

Mean time to first drug administration in 2378 animals was 9.5min (range 3.0-28.0; 95% CI around mean 2.78, 16.22). This is less than the time reported in clinical trials (19.4min, p<0.001). Time to drug predicted ROSC (odds ratio 0.844; 95% CI 0.738, 0.966).

CONCLUSION

Shorter drug delivery time in animal models of cardiac arrest may be one reason for the failure of animal studies to translate successfully into the clinical arena.

Use of high-dose epinephrine and sodium bicarbonate during neonatal resuscitation: is there proven benefit?

For adults and pediatric age patients, high-dose intravenous epinephrine was recommended if standard-dose epinephrine failed to achieve return of spontaneous circulation. More recent trials suggest that high-dose epinephrine is not beneficial and may result in increased harm. There are no randomized clinical studies of high-dose versus standard-dose intravenous epinephrine in neonates. Routine use of high-dose epinephrine during neonatal resuscitation cannot be recommended. Although sodium bicarbonate has been used during neonatal resuscitation, the only randomized controlled trial of its use during brief neonatal resuscitation showed no benefit. Sodium bicarbonate infusion during neonatal cardiopulmonary resuscitation (CPR) has several known and potential side effects. The use of sodium bicarbonate infusion should be discouraged during brief CPR. Whether sodium bicarbonate is beneficial for infants who require prolonged CPR despite adequate ventilation is unknown.

Resuscitation and Emergency Management for Neonatal Foals

Early intervention can dramatically alter outcome in foals. Cardio-pulmonary cerebral resuscitation can be successful and clinically worthwhile when applied to foals that arrest as part of the birthing process. Readily available equipment and an ordered plan starting with addressing the respiratory system (airway and breathing) followed by the circulatory system (circulation and drugs) are the keys to success. Hypoglycemia is common in foals that are not nursing and in septic foals. Support of serum glucose can be an important emergency treatment. Respiratory support with oxygen therapy should be considered in all foals following resuscitation and dystocia. Other foals that are likely to benefit from oxygen are those that are dyspneic, cyanotic, meconium-stained after birth,or recumbent. Emergency therapies, applied correctly, are expected to result in decreased mortality and morbidity.

Comparison of sodium bicarbonate and carbicarb for the treatment of metabolic acidosis in newborn calves

Carbicarb (an equimolar mixture of sodium bicarbonate and sodium carbonate) was compared with sodium bicarbonate alone for the treatment of acidosis in newborn calves: 25 of 49 calves with a blood pH at birth of less than 7-2 and a base deficit of less than -3 mmol/litre were treated intravenously with sodium bicarbonate and 24 were treated with carbicarb. The doses were calculated on the basis of the base deficit in a blood sample taken 10 minutes after birth, and further blood samples were taken immediately after the treatment and 30 and 60 minutes after the treatment for the determination of acid-base status, blood gases and haematological and biochemical variables. Both treatments resulted in a significant increase in blood pH, but there was no difference between them. The mean (sd) blood pH before treatment was 7.09 (0.02) and after treatment it was 7.28 (0.01). There was no increase in the partial pressure of carbon dioxide after treatment with either sodium bicarbonate or carbicarb. Both treatments were associated with an increase in sodium concentration and decreases in the total erythrocyte count, haematocrit and haemoglobin concentration.

Improved resuscitation outcome in emergency medical systems with increased usage of sodium bicarbonate during cardiopulmonary resuscitation

BACKGROUND

The use of sodium bicarbonate (SB) in cardiopulmonary resuscitation (CPR) is controversial. This study analyzes the effects of SB use on CPR outcome in the Brain Resuscitation Clinical Trial III (BRCT III), which was a multicenter randomized trial comparing high-dose to standard-dose epinephrine during CPR. Sodium bicarbonate use in BRCT III was optional.

METHODS

The entire BRCT III database was reviewed. Analysis included only patients who arrested out of the hospital and whose time from collapse to initiation of ACLS was no longer than 30 min (total n = 2122 patients). Sodium bicarbonate use by the 16 participating study sites was analyzed. The study sites were divided according to their SB usage profile: 'low SB user' sites administered SB in less than 50% of CPRs and their first epinephrine to SB time exceeded 10 min; and 'high SB user' sites used SB in over 50% of CPRs and their first epinephrine to SB time was <10 min.

RESULTS

Sites' SB usage rates ranged between 3.1% and 98.2% of CPRs. Sodium bicarbonate usage rates correlated inversely with the sites' intervals from collapse (r = - 0.579 P = 0.018) from initiation of ACLS (r = - 0.685 P = 0.003) and from first epinephrine (r = - 0.611 P = 0.012) to SB administration. Mean ROSC rate in the 'high SB user' sites was 33.5% (CI = 30.0-37.0) compared to 25.7% (CI = 23.1-28.4) in the 'low SB user' sites. In the 'high SB user' sites, hospital discharge rate was 5.3% (CI = 3.6-7.0) compared to 3% (CI = 2.0-4.0) in the 'low SB user' sites, and 5.3% (CI = 3.6-7.0) had a favorable neurological outcome compared to 2.1% (CI = 1.2-3.0) in the 'low SB user' sites. Collapse to ACLS interval was 8.5 min (CI = 8.1-9.0) in the 'high SB user' sites compared to 10.2 min (CI = 9.8-10.6) in the 'low SB user' sites, and their ACLS to first epinephrine interval was 7.0 min (CI = 6.5-7.5) compared to 9.7 min (CI = 9.3-10.2). Multivariate regression analysis found that belonging to 'high SB user' sites independently increased the chances for ROSC (OR 1.36, CI 1.08-1.7) and for achieving a good neurological outcome (OR 2.18, CI 1.23-3.86).

CONCLUSIONS

Earlier and more frequent use of SB was associated with higher early resuscitability rates and with better long-term outcome. Sodium bicarbonate may be beneficial during CPR, and it should be subjected to a randomized clinical trial.

Treatment of metabolic acidosis

Metabolic acidosis is characterized by a decrease of the blood pH associated with a decrease in the bicarbonate concentration. This may be secondary to a decrease in the strong ion difference or to an increase in the weak acids concentration, mainly the inorganic phosphorus. From a conceptual point of view, two types of nontoxic metabolic acidosis must be differentiated: the mineral metabolic acidosis that reveals the presence of an excess of nonmetabolizable anions, and the organic metabolic acidosis that reveals an excess of metabolizable anions. Significance and consequences of these two types of acidosis are radically different. Mineral acidosis is not caused by a failure in the energy metabolic pathways, and its treatment is mainly symptomatic by correcting the blood pH (alkali therapy) or accelerating the elimination of excessive mineral anions (renal replacement therapy). On the other hand, organic acidosis gives evidence that a severe underlying metabolic distress is in process. No reliable argument exists to prove that this acidosis is harmful under these conditions in humans. Experimental data even show that hypoxic cells are able to survive only if the medium is kept acidic. The management of an acute organic metabolic acidosis is therefore primarily based on the cause of the acidosis, and no scientific argument exists to justify the correction of the acid-base imbalance in this context.

Pediatric cardiopulmonary-cerebral resuscitation: an overview and future directions

The evolving understanding of pathophysiologic events during and after pediatric cardiac arrest has not yet resulted in significantly improved outcome. Exciting breakthroughs in basic and applied science laboratories are, however, on the immediate horizon for study in specific subpopulations of cardiac arrest victims. Strategically focusing therapies to specific phases of cardiac arrest and resuscitation and evolving pathophysiologic events offers great promise that critical care interventions will lead the way to more successful cardiopulmonary and cerebral resuscitation in children.

Clinical use of sodium bicarbonate during cardiopulmonary resuscitation--is it used sensibly?

This study retrospectively analyzed the pattern of sodium bicarbonate (SB) use during cardiopulmonary resuscitation (CPR) in the Brain Resuscitation Clinical Trial III (BRCT III). BRCT III was a prospective clinical trial, which compared high-dose to standard-dose epinephrine during CPR. SB use was left optional in the study protocol. Records of 2915 patients were reviewed. Percentage, timing and dosage of SB administration were correlated with demographic and cardiac arrest variables and with times from collapse to Basic Life Support, to Advanced Cardiac Life Support (ACLS) and to the major interventions performed during CPR. SB was administered in 54.5% of the resuscitations. The rate of SB use decreased with increasing patient age-primarily reflecting shorter CPR attempts. Mean time intervals from arrest, from start of ACLS and from first epinephrine to administration of the first SB were 29+/-16, 19+/-13, and 10.8+/-11.1 min, respectively. No correlation was found between the rate of SB use and the pre-ACLS hypoxia times. On the other hand, a direct linear correlation was found between the rate of SB use and the duration of ACLS. We conclude that when SB was used, the time from initiation of ACLS to administration of its first dose was long and severe metabolic acidosis probably already existed at this point. Therefore, if SB is used, earlier administration may be considered. Contrary to physiological rationale, clinical decisions regarding SB use did not seem to take into consideration the duration of pre-ACLS hypoxia times. We suggest that guidelines for SB use during CPR should emphasize the importance of pre-ACLS hypoxia time in contributing to metabolic acidosis and should be more specific in defining the duration of "protracted CPR or long resuscitative efforts", the most frequent indication for SB administration.

Use of base in the treatment of severe acidemic states

Severe acidemia (blood pH < 7.1 to 7.2) suppresses myocardial contractility, predisposes to cardiac arrhythmias, causes venoconstriction, and can decrease total peripheral vascular resistance and blood pressure, reduce hepatic blood flow, and impair oxygen delivery. These alterations in organ function can contribute to increased morbidity and mortality. Although it seemed logical to administer sodium bicarbonate to attenuate acidemia and therefore lessen the impact on cardiac function, the routine use of bicarbonate in the treatment of the most common causes of severe acidemia, diabetic ketoacidosis, lactic acidosis, and cardiac arrest, has been an issue of great controversy. Studies of animals and patients with these disorders have reported conflicting data on the benefits of bicarbonate, showing both beneficial and detrimental effects. Alternative alkalinizing agents, tris-hydroxymethyl aminomethane and Carbicarb, have shown some promise in studies of animals and humans, and reevaluation of these buffers in the treatment of severe acidemic states seems warranted. The potential value of base therapy in the treatment of severe acidemia remains an important issue, and further studies are required to determine which patients should be administered base therapy and what base should be used.

Response to repeated equal doses of epinephrine during cardiopulmonary resuscitation in dogs

STUDY OBJECTIVE

Advanced cardiac life support (ACLS) guidelines recommend a 3- to 5-minute interval between repeated doses of epinephrine. This recommendation does not take into account the dose of epinephrine used, and only very limited data exist regarding the hemodynamic responses to repeated "high" doses of epinephrine. The objective of this study was to analyze the hemodynamic responses to repeated, equal, high doses of epinephrine administered during cardiopulmonary resuscitation (CPR) in a canine model of ventricular fibrillation (VF).

METHODS

This study used a secondary analysis of data collected in a prospective, randomized study, primarily designed to assess the effects of acid buffers in a canine model of cardiac arrest. VF was electrically induced. After 10 minutes, CPR was initiated, including ventilation with FIO(2)=1.0, external chest compressions, administration of epinephrine (0.1 mg/kg repeated every 5 minutes) and defibrillation. Animals were randomized to receive either NaHCO(3), Carbicarb, tromethamine (THAM), or NaCl. The hemodynamic variables were sampled from each experiment's paper chart at 1-minute intervals, and the responses to the first 4 doses of epinephrine were compared.

RESULTS

Thirty-six animals (9 in each buffer group) were included in this analysis. Systolic, diastolic, and coronary perfusion pressures increased steeply (by 100%, 130%, and 190%, respectively) only after the first epinephrine dose. These pressures peaked at 2 to 3 minutes and decreased only slightly and insignificantly during the rest of the 5-minute interval, until the next epinephrine dose. No further significant increases in arterial pressures were observed in response to the next 3 doses of epinephrine, administered 5 minutes apart.

CONCLUSION

The hemodynamic effects of high-dose epinephrine (0.1 mg/kg) during CPR appear to last longer than 5 minutes. Therefore, longer intervals between doses may be justified with high doses of epinephrine.