Pharmacologic controversies in CPR

Recent advances in emergency life support

With additional international input, recent changes in emergency life support are reflected in updated guidelines for Advanced Cardiac Life Support (ACLS) from the American Heart Association and new technology in the arena of vascular access and emergency airway management. These changes will expand nurses' ability to provide advanced levels of care, even in the prehospital situation, and represent a more rigorous evidence-based approach than ever before. As early morbidity and mortality in emergency situations are frequently associated with complications associated with airway management and vascular access, recent development in these areas are reviewed along with evolution in ACLS guidelines.

Recent progress in advanced cardiac life support

The revised guidelines for advanced cardiac life support (ACLS) from the American Heart Association are anticipated in the fall of 2000. Although dramatic changes in the approach to adult basic and ACLS are not anticipated, several controversies and new drugs on the horizon may radically change our approach to emergent cardiac resuscitation. This article features some of the evolving thinking on the emergent treatment of the adult with ventricular fibrillation or ventricular tachycardia, the critical rhythms seen in most cases of acute cardiac distress. Approaches to airway therapy drug administration and new agents also are described.

Do advanced cardiac life support drugs increase resuscitation rates from in-hospital cardiac arrest? The OTAC Study Group

STUDY OBJECTIVE

The benefit of Advanced Cardiac Life Support (ACLS) medications during cardiac resuscitation is uncertain. The objective of this study was to determine whether the use of these medications increased resuscitation from in-hospital cardiac arrest.

METHODS

A prospective cohort of patients undergoing cardiac arrest in 1 of 5 academic hospitals was studied. Patient and arrest factors related to resuscitation outcome were recorded. We determined the association of the administration of ACLS drugs (epinephrine, atropine, bicarbonate, calcium, lidocaine, and bretylium) with survival at 1 hour after resuscitation.

RESULTS

Seven hundred seventy-three patients underwent cardiac resuscitation, with 269 (34. 8%) surviving for 1 hour. Use of epinephrine, atropine, bicarbonate, calcium, and lidocaine was associated with a decreased chance of successful resuscitation (P <.001 for all except lidocaine, P <.01). While controlling for significant patient factors (age, gender, and previous cardiac or respiratory disease) and arrest factors (initial cardiac rhythm, and cause of arrest), multivariate logistic regression demonstrated a significant association between unsuccessful resuscitation and the use of epinephrine (odds ratio . 08 [95% confidence interval .04-.14]), atropine (.24 [.17-.35]), bicarbonate (.31 [.21-.44]), calcium (.32 [.18-.55]), and lidocaine (.48 [.33-.71]). Drug effects did not improve when patients were grouped by their initial cardiac rhythm. Cox proportional hazards models that controlled for significant confounders demonstrated that survivors were significantly less likely to receive epinephrine (P <. 001) or atropine (P <.001) throughout the arrest.

CONCLUSION

We found no association between standard ACLS medications and improved resuscitation from in-hospital cardiac arrest. Randomized clinical trials are needed to determine whether other therapies can improve resuscitation from cardiac arrest when compared with the presently used ACLS drugs.

Intravenous amiodarone for ventricular arrhythmias: overview and clinical use

Numerous pharmacological agents with varying cellular electrophysiological effects are available to treat cardiac arrhythmias. Amiodarone is predominantly a Vaughan Williams Class III agent, but also possesses electrophysiological characteristics of the other three Vaughan Williams classes (Class I and IV and minor Class II effects). Amiodarone's primary mechanism is to prolong the cardiac action potential and repolarization time leading to an increased refractory period and reduced membrane excitability. The efficacy and tolerability of intravenous (IV) amiodarone for acute treatment of recurrent and refractory ventricular tachycardia and ventricular fibrillation has been demonstrated in clinical trials. The ARREST trial, a randomized trial comparing IV amiodarone to placebo, found a significant improvement in the proportion of patients surviving to the emergency department following out-of-hospital cardiac arrest in amiodarone-treated patients. Intravenous amiodarone is an effective anti-arrhythmic agent for the acute treatment of life-threatening ventricular arrhythmias and represents an important treatment option for emergency anti-arrhythmic therapy for patients suffering from cardiac arrest.

Endotracheal drug delivery followed by a 90-degree torso tilt in a swine model of cardiac arrest

OBJECTIVES

Prehospital providers are often unable to obtain intravenous (i.v.) access in cardiac arrest victims. While several drugs can be administered via the endotracheal (ET) route, serum drug levels are lower than those obtained with the i.v. route. The authors hypothesized that a 90-degree torso tilt after ET drug administration would increase drug levels.

METHODS

A randomized, prospective, unblinded laboratory trial was conducted. Twenty-three mixed-breed domestic swine (20-25 kg) were sedated, anesthetized, instrumented, shocked into cardiac arrest, and randomized into three groups. Lidocaine was administered either i.v. (1.5 mg/kg), traditional ET (4.5 mg/kg), or ET followed by a 5-second 90-degree upright torso tilt (4.5 mg/kg). While standard CPR was performed, lidocaine levels were obtained at 0.5, 1, 2, 3, 4, and 5 minutes after administration. Repeated-measures ANOVA was used for data analysis (alpha = 0.05).

RESULTS

Experimental ET compared with traditional ET administration produced significantly higher levels at all time points except 0.5 minutes. Comparing experimental ET with i.v. administration yielded significantly higher levels for the i.v. route at 0.5 and 1 minute and for the experimental ET route at 4 and 5 minutes. i.v. lidocaine administration resulted in significantly higher levels at 0.5, 1, and 2 minutes when compared with traditional ET administration.

CONCLUSIONS

Endotracheal instillation of lidocaine followed by a 90-degree torso tilt resulted in better drug absorption, as evidenced by higher serum lidocaine levels, than did traditional recumbent ET delivery at all but the earliest time point and produced more sustained lidocaine levels than i.v. administration at 4 and 5 minutes. ET drug delivery followed by a 5-second 90-degree torso tilt and the mechanisms for this enhanced absorption warrant further investigation.

Current concepts in cardiopulmonary resuscitation

The "chain of survival" is important in the resuscitation of a patient who has had a cardiac arrest. The provision of Basic Life Support (BLS) and Advanced Cardiac Life Support (ACLS) is essential in this "chain of survival." Both BLS and ACLS have undergone several revisions since their initial inception. This article reviews (1) the current established and investigational issues of cardiopulmonary resuscitation, (2) the incidence and outcomes of anesthesia-related cardiac arrest, (3) the use of cardiopulmonary bypass in resuscitation, and (4) cerebral protection during and after resuscitation.