Use of pressors in the treatment of cardiac arrest

Important Changes in the ACLS 2000 Guidelines for the Management of Cardiac Arrest

This feature examines the impact of pharmacologic interventions on the treatment of the critically ill patient—an area of health care that has become increasingly complex. It will review recent advances (including evolving and controversial data) in drug therapy for adult ICU patients and assess these new modalities in terms of clinical, humanistic, and economic outcomes.

Vasopressin Associated With an Increase in Return of Spontaneous Circulation in Acidotic Cardiopulmonary Arrest Patients

Background: During respiratory and metabolic acidosis, the vasoconstrictive effects of epinephrine may be blunted, whereas the response to vasopressin remains unchanged. The impact of this effect during advanced cardiac life support (ACLS) remains unclear. Objective: Determine if vasopressin therapy in combination with epinephrine was associated with improved outcomes in patients with cardiac arrest compared to epinephrine alone. The primary outcome was difference in rate of return of spontaneous circulation (ROSC). Secondary outcomes included evaluation of rates of ROSC for patients with an initial pH <7.2 and by initial pulseless rhythm. Methods: Single-center, retrospective review conducted from July 2010 to July 2012. Patients ≥18 years of age with documented cardiac arrest requiring ACLS and vasopressor therapy were included. Results: A total of 101 patients met inclusion criteria. There was no difference in rate of ROSC (56% vs 60%, P = 0.68) or survival to hospital discharge (9% vs 5%, P = 0.46) between patients who received vasopressin in combination with epinephrine (n = 43) compared to epinephrine alone (n = 58). Subgroup analysis of ROSC in patients with an arterial pH of <7.2 (n = 35) showed an increased rate of ROSC (63% vs 37%, P = 0.01) in the vasopressin plus epinephrine group versus the epinephrine alone group, respectively. Subgroup analysis by initial cardiac rhythm showed no difference in rate of ROSC. Conclusions: Vasopressin in combination with epinephrine demonstrated improved ROSC in cardiac arrest patients with initial arterial pH <7.2 compared with epinephrine alone, without improving survival to hospital discharge.

Experimental cardiac arrest treatment with adrenaline, vasopressin, or placebo

BACKGROUND

The effect of vasoconstrictors in prolonged cardiopulmonary resuscitation (CPR) has not been fully clarified.

OBJECTIVES

To evaluate adrenaline and vasopressin pressure effect, and observe the return of spontaneous circulation (ROSC).

METHODS

A prospective, randomized, blinded, and placebo-controlled study. After seven minutes of untreated ventricular fibrillation, pigs received two minutes cycles of CPR. Defibrillation was attempted (4 J/kg) once at 9 minutes, and after every cycle if a shockable rhythm was present, after what CPR was immediately resumed. At 9 minutes and every five minutes intervals, 0.02 mg/kg (n = 12 pigs) adrenaline, or 0.4 U/kg (n = 12) vasopressin, or 0.2 mL/kg (n = 8) 0.9% saline solution was administered. CPR continued for 30 minutes or until the ROSC.

RESULTS

Coronary perfusion pressure increased to about 20 mmHg in the three groups. Following vasoconstrictors doses, pressure level reached 35 mmHg versus 15 mmHg with placebo (p < 0.001). Vasopressin effect remained at 15-20 mmHg after three doses versus zero with adrenaline or placebo. ROSC rate differed (p = 0.031) among adrenaline (10/12), vasopressin (6/12), and placebo (2/8). Time-to-ROSC did not differ (16 minutes), nor the number of doses previously received (one or two). There was no difference between vasoconstrictors, but against placebo, only adrenaline significantly increased the ROSC rate (p = 0.019).

CONCLUSION

The vasoconstrictors initial pressure effect was equivalent and vasopressin maintained a late effect at prolonged resuscitation. Nevertheless, when compared with placebo, only adrenaline significantly increased the ROSC rate.

Current pharmacological advances in the treatment of cardiac arrest

Cardiac arrest is defined as the sudden cessation of spontaneous ventilation and circulation. Within 15 seconds of cardiac arrest, the patient loses consciousness, electroencephalogram becomes flat after 30 seconds, pupils dilate fully after 60 seconds, and cerebral damage takes place within 90–300 seconds. It is essential to act immediately as irreversible damage can occur in a short time. Cardiopulmonary resuscitation (CPR) is an attempt to restore spontaneous circulation through a broad range of interventions which are early defibrillation, high-quality and uninterrupted chest compressions, advanced airway interventions, and pharmacological interventions. Drugs should be considered only after initial shocks have been delivered (when indicated) and chest compressions and ventilation have been started. During cardiopulmonary resuscitation, no specific drug therapy has been shown to improve survival to hospital discharge after cardiac arrest, and only few drugs have a proven benefit for short-term survival. This paper reviews current pharmacological treatment of cardiac arrest. There are three groups of drugs relevant to the management of cardiac arrest: vasopressors, antiarrhythmics, and other drugs such as sodium bicarbonate, calcium, magnesium, atropine, fibrinolytic drugs, and corticosteroids.

Update on cardiopulmonary resuscitation and emergency cardiovascular care guidelines

PURPOSE

The key changes included in the 2005 cardiopulmonary resuscitation (CPR) and emergency cardiac care (ECC) guidelines are reviewed. Advances since publication of the current guidelines are also discussed.

SUMMARY

The 2005 CPR and ECC guidelines include several key changes from the previous version published in 2000. The new guidelines place an increased emphasis on chest compressions and recommend a compression:ventilation (C:V) ratio of 30:2. Current knowledge on defibrillation has also been incorporated by recommending that Emergency Medical Service (EMS) rescuers give two minutes of CPR before defibrillation when the response interval is greater than four to five minutes and EMS responders did not witness the arrest. Another major change is the recommendation for a single shock to be administered followed immediately by CPR with no check of the cardiac rhythm until two minutes of CPR has been performed postdefibrillation. The 2005 guidelines recommend that an automated external defibrillator should be implemented in public locations where there is a relatively high likelihood of witnessed cardiac arrest. In addition, the most recent guidelines highlight the shift from primary-rhythm-based therapies and resuscitation to a focus on neurologic outcomes.

CONCLUSION

Several evidence-based changes were included in the 2005 CPR and ECC guidelines, including a C:V ratio of 30:2 and mitigation of hands-off time, early defibrillation, administration of a single shock versus a three-shock sequence, use of public-access defibrillators, and a shift from primary-rhythm-based therapies to a focus on neurologic outcomes.

Statistical analysis of joint short-term and long-term survival in resuscitation research

OBJECTIVE

To develop statistical tools that use combined initial survival data and post-resuscitation survival data to test the null hypothesis that true, population-wide outcomes following experimental CPR interventions are not different from control.

METHOD

A new test statistic, d(2), for evaluating Type 1 error is derived from a bivariate, two-dimensional analysis of categorical initial resuscitation and post-resuscitation survival data, which are statistically independent because they are obtained during non-overlapping periods of time. The d(2) test statistic, which is distributed as a chi-squared distribution, is derived from first principles and validated using Monte Carlo methods of computer simulation for thousands of clinical trials.

RESULTS

Under the null hypothesis, the normalized difference in the proportions of patients surviving the initial resuscitation period and the normalized difference in the proportions of such short-term survivors that also survive the post-resuscitation period are jointly distributed in a two-dimensional space as a bivariate standard normal distribution, against which observed intervention and control outcomes can be compared in a test of statistical significance. Typically this two-dimensional approach has greater statistical power to detect true differences, compared to conventional one-dimensional tests. Smaller group sizes (Ns) are usually required to reach statistical significance when both initial survival and post-resuscitation survival are considered together. Such two-dimensional analysis is easily extended to meta-analysis of multiple trials.

CONCLUSIONS

A straightforward, easy-to-use bivariate test for Type I errors in statistical inference can be done for resuscitation studies reporting both short-term and long-term survival data. Acceptance of such two-dimensional tests of the null hypothesis, as proposed by Hallstrom, can save time, money, effort, and disappointment in the difficult and sometimes frustrating field of resuscitation research.

Recent developments in the pharmacologic approach to pediatric critical care

PURPOSE OF REVIEW

There is new information supporting a resurgence of targeted use of older medications. These therapies include hydrocortisone and vasopressin. In addition to these older drugs, newer drugs, drotrecogin alpha (activated protein C) and activated factor VII concentrate (NovoSeven), have been used and may improve outcome in the treatment of critically ill patients. This review summarizes the recent experience of these agents in the adult and pediatric critically ill populations.

RECENT FINDINGS

Preliminary findings are encouraging in selected septic children and adults for human recombinant activated protein C and protein C concentrate. Plasma vasopressin levels in pediatric septic shock and their importance have not yet been adequately studied. Recent evidence supports physiologic replacement of corticosteroids in specific adult populations. Further investigations are warranted to establish the role of activated factor VIIa in the treatment of critically ill children.

SUMMARY

The limited experience of protein C manipulation in critically ill septic pediatric patients makes it difficult to define its role in their care. Although it has been associated with improved outcomes, its risk profile warrants judicious use. Further prospective pediatric clinical trials are needed to define the role of vasopressin in the treatment of pediatric shock and cardiac arrest. The role of corticosteroids in the treatment of septic shock in adults and children continues to be debated. Activated factor VIIa administration to adult and pediatric patients without primary bleeding disorders has been increasing. Further investigations are warranted to establish the role of activated factor VIIa in the treatment of critically ill children.

Vasopressors for cardiopulmonary resuscitation. Does pharmacological evidence support clinical practice?

Adrenaline (epinephrine) has been used for cardiopulmonary resuscitation (CPR) since 1896. The rationale behind its use is thought to be its alpha-adrenoceptor-mediated peripheral vasoconstriction, causing residual blood flow to be diverted to coronary and cerebral circulations. This protects these tissues from ischaemic damage and increases the likelihood of restoration of spontaneous circulation. Clinical trials have not demonstrated any benefit of adrenaline over placebo as an agent for resuscitation. Adrenaline has deleterious effects in the setting of resuscitation, predictable from its promiscuous pharmacological profile. This article discusses the relevant pharmacology of adrenaline in the context of CPR. Experimental and clinical evidences for the use of adrenaline and alternative vasopressor agents in resuscitation are given, and the properties of an ideal vasopressor are discussed.

Evolving role of vasopressin in the treatment of cardiac arrest

Sudden cardiac arrest is a major public heath problem, affecting more than 450,000 individuals annually. Response time and the initiation of cardiopulmonary resuscitation (CPR) remain the most important factors determining successful revival. During resuscitation, sympathomimetics are given to enhance cerebral and coronary perfusion pressures in an attempt to achieve restoration of spontaneous circulation. Epinephrine has been the preferred vasopressor since the inception of advanced cardiac life support, although the lack of definitive evidence regarding its effectiveness has created much controversy surrounding its use, including the optimum dosage. Vasopressin is an alternative vasopressor that, when given at high doses, causes vasoconstriction by directly stimulating smooth muscle V1 receptors. The 2000 American Heart Association (AHA) guidelines commented that vasopressin is a reasonable first-line vasopressor in patients with ventricular fibrillation or pulseless ventricular tachycardia. Since release of those guidelines, additional human studies support an expanded role for vasopressin, whereas other studies cast doubt regarding its efficacy compared with epinephrine. The AHA recently released revised guidelines for CPR and emergency cardiovascular care. The consensus was that vasopressors should remain a part of pulseless sudden cardiac arrest management, with epinephrine 1 mg every 3-5 minutes being the recommended adrenergic of choice. In these revised guidelines, the role of vasopressin expanded beyond previous recommendations, despite the recommendation being downgraded to class indeterminate. The guidelines comment that one dose of vasopressin 40 U may replace the first or second dose of epinephrine in all pulseless sudden cardiac arrest scenarios, including asystole and pulseless electrical activity. A consistent theme with all vasopressors in sudden cardiac arrest is that additional studies are necessary to clearly document greater efficacy compared with no treatment. Further evaluation is warranted to better assess the role of vasopressin in asystolic sudden cardiac arrest, as well as its use with epinephrine, and to determine its optimal timing of administration and potential synergistic effects.

Vasopressin in Cardiac Arrest

Objective:

To review the efficacy and safety of vasopressin in cardiac arrest.

Data Sources:

MEDLINE, EMBASE, and PubMed were searched (all to June 2005) for full-text English-language publications describing trials in humans. Search terms were vasopressin, epinephrine, adrenaline, heart arrest, cardiac arrest, and clinical trial.

Study Selection and Data Extraction:

Prospective, randomized, controlled trials that evaluated efficacy or safety endpoints of vasopressin in the management of cardiac arrest were included. Efficacy outcomes included return of spontaneous circulation, successful resuscitation, survival to hospital admission, 2hour survival, and survival to hospital discharge. Safety outcomes were as defined by each trial.

Data Synthesis:

Three prospective trials were identified and included in this review. Vasopressin does not appear to offer any therapeutic advantage compared with epinephrine in the treatment of both in-hospital and out-of-hospital cardiac arrest, regardless of the presenting arrest rhythm. Although there is a suggestion that vasopressin may be effective in treatment of asystole, the evidence for this arises from a subgroup analysis that should be viewed as hypothesis generating. There are limited data describing the safety of vasopressin in cardiac arrest.

CONCLUSIONS:

The current evidence for the use of vasopressin in cardiac arrest is indeterminate. Given the similarly equivocal evidence of efficacy for epinephrine, either drug could be considered the first-line agent in cardiac arrest. Placebo-controlled studies with appropriate statistical power are warranted to evaluate meaningful clinical outcomes, such as survival to hospital discharge. Further evaluation of the role of vasopressin in asystolic cardiac arrest and its use in combination with epinephrine is also justified.

Epinephrine and vasopressin during cardiopulmonary resuscitation

Epinephrine (adrenaline) and vasopressin have been by far the most commonly studied vasopressors in experimental cardiac arrest. Despite animal experimental studies suggesting improved outcomes in experimental cardiac arrest, clinical trials of pressor agents have failed to show clear cut benefit from either vasopressin or epinephrine, although few, if any, trials compared pressor agents to a placebo. The action of vasopressors in the heart, particularly beta1-adrenergic stimulation, is associated with adverse cardiac effects including post-resuscitation myocardial dysfunction, worsening ventricular arrhythmias, and increasing myocardial oxygen consumption. Alpha2-adrenergic agonists, in experimental studies, show great promise in improving outcomes in experimental cardiac arrest, but have not been studied in humans. The combination of epinephrine and vasopressin may be effective, but has been incompletely studied. Clinical trials of vasopressor agents, which minimize direct myocardial effects are needed.

Advanced life support drugs: do they really work?

Basic life support and rapid defibrillation for ventricular fibrillation or pulseless ventricular tachycardia are the only two interventions that have been shown unequivocally to improve survival after cardiac arrest. Several drugs are advocated to treat cardiac arrest, but despite very encouraging animal data, no drug has been reliably proven to increase survival to hospital discharge after cardiac arrest. This review focuses on recent experimental and clinical data concerning the use of vasopressin, amiodarone, magnesium, and fibrinolytics during advanced life support (ALS). Animal data indicate that, in comparison with epinephrine (adrenaline), vasopressin produces better vital organ blood flow during cardiopulmonary resuscitation (CPR). These apparent advantages have yet to be converted into improved survival in large-scale trials of cardiac arrest in humans. Data from two prospective, randomized trials suggest that amiodarone may improve short-term survival after out-of-hospital ventricular fibrillation cardiac arrest. On the basis of anecdotal data, magnesium is recommended therapy for torsades de pointes and for shock-resistant ventricular fibrillation associated with hypomagnesemia. In the past, CPR has been a contraindication to giving fibrinolytics, but several studies have demonstrated the relative safety of fibrinolysis during and after CPR. Fibrinolytics are likely to be beneficial when cardiac arrest is associated with plaque rupture and fresh coronary thrombus or massive pulmonary embolism. Fibrinolysis may also improve cerebral microcirculatory perfusion once a spontaneous circulation has been restored. A planned, prospective, randomized trial may help to define the role of fibrinolysis during out-of-hospital CPR.