The Effect of the Preshock Pause on Coronary Perfusion Pressure Decay and Rescue Shock Outcome in Porcine Ventricular Fibrillation

Cardiopulmonary Resuscitation: The Importance of the Basics

Cardiac arrest is the loss of organized cardiac activity. Unfortunately, survival to hospital discharge is poor, despite recent scientific advances. The goals of cardiopulmonary resuscitation (CPR) are to restore circulation and identify and correct an underlying etiology. High-quality compressions remain the foundation of CPR, optimizing coronary and cerebral perfusion pressure. High-quality compressions must be performed at the appropriate rate and depth. Interruptions in compressions are detrimental to management. Mechanical compression devices are not associated with improved outcomes but can assist in several situations.

Chest compression pauses during defibrillation attempts

PURPOSE OF REVIEW

This article summarizes current knowledge of the causes and consequences of interruption of chest compressions during cardiopulmonary resuscitation.

RECENT FINDINGS

Pauses in chest compressions occur during analysis of the heart rhythm, delivery of ventilation, interventions such as intubation, and gaining intravenous access, but pauses may also be unprompted. Pauses related to defibrillation are because of preshock pauses for rhythm analysis and charging, and postshock pauses to evaluate the outcome of the shock. Prolonged pauses, mainly preshock pauses (>10 s) are associated with decreased survival to discharge in retrospective analyses. Measures to reduce preshock and postshock pauses include resuming chest compressions during defibrillator charging, continued chest compression during defibrillation by mechanical chest compression devices or during manual chest compression with sufficiently insulating gloves for the rescuer, and eliminating postshock rhythm and pulse checks. New filtering techniques may allow rhythm analysis during chest compressions.

SUMMARY

It is important to avoid any unnecessary pause in chest compressions before and after a defibrillation shock. Pauses should be kept to an absolute minimum, preferably to less than 10 s.

Blinded Evaluation of Combination Drug Therapy for Prolonged Ventricular Fibrillation Using a Swine Model of Sudden Cardiac Arrest

Despite experimental evidence supporting the use of resuscitation drugs in the treatment of sudden cardiac arrest (CA), there are no good human clinical data to support the decades-old practice of giving these medications during out-of-hospital CA resuscitation. We hypothesized that the lack of efficacy in clinical practice in ventricular fibrillation (VF) is the failure-based manner in which resuscitation drugs have historically been administered (one at a time interspersed with chest compressions and a defibrillation attempt, giving the next only if the previous one was ineffective). The aim of this study was to determine if giving and circulating a combination of commonly available, historically used resuscitation drugs together, prior to the first defibrillation attempt after prolonged VF, might improve short-term outcomes compared with the failure-based serial drug approach used in the past. We used a well-established swine model of sudden prolonged untreated VF. Animals were randomized to receive epinephrine (0.01 mg/kg), vasopressin (0.5 U/kg), amiodarone (4 mg/kg), and sodium bicarbonate (1.0 mEq/kg) in series (SERIES group [n = 53]) or a combination of epinephrine (0.01 mg/kg), vasopressin (0.5 U/kg), amiodarone (4 mg/kg), sodium bicarbonate (1.0 mEq/kg), and metoprolol (0.2 mg/kg) (COCKTAIL group) delivered in rapid succession at the beginning of the attempted resuscitation (n = 27). Data were analyzed descriptively. Baseline characteristics and chemistries between the two groups were the same. Termination of VF was statistically similar in the two groups: 88.7% (47/53) versus 85.2% (23/27) p = 0.66, with an adjusted relative risk ratio (RRR) of 0.94 (0.37, 1.15). However, ROSC was higher in the SERIES group (56.6% [30/53] versus 22.2% [6/27], adjusted RRR = 2.83; [1.16, 3.84] p = 0.029) as was 20-minute survival (52.8% [28/53] versus 18.5% [5/27], adjusted RRR = 3.15 [1.14, 4.54] p = 0.032). The combination of drugs studied, at these dosages, inexplicably worsened short-term outcomes after prolonged untreated VF.

Cardiac Arrest Resuscitation

Cardiac arrest is a dynamic disease that tests the multitasking and leadership abilities of emergency physicians. Providers must simultaneously manage the logistics of resuscitation while searching for the cause of cardiac arrest. The astute clinician will also realize that he or she is orchestrating only one portion of a larger series of events, each of which directly affects patient outcomes. Resuscitation science is rapidly evolving, and emergency providers must be familiar with the latest evidence and controversies surrounding resuscitative techniques. This article reviews evidence, discusses controversies, and offers strategies to provide quality cardiac arrest resuscitation.

Fully automatic rhythm analysis during chest compression pauses

AIM

Chest compression artefacts impede a reliable rhythm analysis during cardiopulmonary resuscitation (CPR). These artefacts are not present during ventilations in 30:2 CPR. The aim of this study is to prove that a fully automatic method for rhythm analysis during ventilation pauses in 30:2 CPR is reliable an accurate.

METHODS

For this study 1414min of 30:2 CPR from 135 out-of-hospital cardiac arrest cases were analysed. The data contained 1942 pauses in compressions longer than 3.5s. An automatic pause detector identified the pauses using the transthoracic impedance, and a shock advice algorithm (SAA) diagnosed the rhythm during the detected pauses. The SAA analysed 3-s of the ECG during each pause for an accurate shock/no-shock decision.

RESULTS

The sensitivity and PPV of the pause detector were 93.5% and 97.3%, respectively. The sensitivity and specificity of the SAA in the detected pauses were 93.8% (90% low CI, 90.0%) and 95.9% (90% low CI, 94.7%), respectively. Using the method, shocks would have been advanced in 97% of occasions. For patients in nonshockable rhythms, rhythm reassessment pauses would be avoided in 95.2% (95% CI, 91.6-98.8) of occasions, thus increasing the overall chest compression fraction (CCF).

CONCLUSION

An automatic method could be used to safely analyse the rhythm during ventilation pauses. This would contribute to an early detection of refibrillation, and to increase CCF in patients with nonshockable rhythms.

Outcomes by rescue shock number during the metabolic phase of porcine ventricular fibrillation resuscitation

BACKGROUND

Optimal resuscitation duration before the first rescue shock (RS) to maximize the probability of success after prolonged ventricular fibrillation (VF) cardiac arrest remains unknown. The purpose of this study was to determine the occurrence of return of spontaneous circulation (ROSC) and survival by RS attempt after 12 minutes of untreated VF.

METHODS

This was a secondary analysis of prospectively collected data from an institutional animal care and use committee-approved protocol. Fifty-three swine (30-35 kg) were instrumented under anesthesia. Ventricular fibrillation was electrically induced. After 12 minutes of untreated VF, cardiopulmonary resuscitation (CPR) was initiated (and continued as necessary (prn)) and a standard dose of epinephrine (0.01 mg/kg) was given (and repeated every 3 (q3) minutes prn). The first RS was delivered after 3 minutes of CPR (and q3 minutes thereafter prn). Each failed RS was followed (in series) by vasopressin (0.57 mg/kg), amiodarone (4.3 mg/kg), and sodium bicarbonate (1 mEq/kg) prn. Resuscitation continued until ROSC or 20-minute elapsed time. The primary outcomes were ROSC and 20-minute survival. Data were analyzed using descriptive statistics.

RESULTS

After 3 minutes of resuscitation, 1 animal (1.9% [95% confidence interval {CI, 0.3-10.0]) achieved ROSC on RS1 and survived. After 6 minutes of resuscitation, 17 animals (32.1% [95% CI, 21.1-45.5]) achieved ROSC on RS2 and 15 (28.3% [95% CI, 18.0-41.6]) survived. Twelve additional animals had ROSC and survival with continued resuscitation. In 23 animals, ROSC was never achieved and efforts were terminated per protocol.

CONCLUSION

Our data suggest that during the metabolic phase of VF, 3 minutes of CPR and 1 standard dose of epinephrine may be insufficient to achieve ROSC on the first RS attempt. A longer duration of CPR and/or additional vasopressors may increase the likelihood of successful defibrillation.

Perishock pause: an independent predictor of survival from out-of-hospital shockable cardiac arrest

BACKGROUND

Perishock pauses are pauses in chest compressions before and after defibrillatory shock. We examined the relationship between perishock pauses and survival to hospital discharge.

METHODS AND RESULTS

We included out-of-hospital cardiac arrest patients in the Resuscitation Outcomes Consortium Epistry-Cardiac Arrest who suffered arrest between December 2005 and June 2007, presented with a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia), and had cardiopulmonary resuscitation process data for at least 1 shock (n=815). We used multivariable logistic regression to determine the association between survival and perishock pauses. In an analysis adjusted for Utstein predictors of survival, the odds of survival were significantly lower for patients with preshock pause ≥20 seconds (odds ratio, 0.47; 95% confidence interval, 0.27 to 0.82) and perishock pause ≥40 seconds (odds ratio, 0.54; 95% confidence interval, 0.31 to 0.97) compared with patients with preshock pause <10 seconds and perishock pause <20 seconds. Postshock pause was not independently associated with a significant change in the odds of survival. Log-linear modeling depicted a decrease in survival to hospital discharge of 18% and 14% for every 5-second increase in both preshock and perishock pause interval (up to 40 and 50 seconds, respectively), with no significant association noted with changes in the postshock pause interval.

CONCLUSIONS

In patients with cardiac arrest presenting in a shockable rhythm, longer perishock and preshock pauses were independently associated with a decrease in survival to hospital discharge. The impact of preshock pause on survival suggests that refinement of automatic defibrillator software and paramedic education to minimize preshock pause delays may have a significant impact on survival.