Hands-on defibrillation has the potential to improve the quality of cardiopulmonary resuscitation and is safe for rescuers-a preclinical study

Abstract

Background: Recently, it has been demonstrated that rescuers could safely provide a low, static downward force in direct contact with patients during elective cardioversion. The purpose of our experimental study was to investigate whether shock delivery during uninterrupted chest compressions may have an impact on cardiopulmonary resuscitation (CPR) quality and can be safely performed in a realistic animal model of CPR.

Methods and results: Twenty anesthetized swine were subjected to 7 minutes of ventricular fibrillation followed by CPR according to the 2010 American Heart Association Guidelines. Pregelled self-adhesive defibrillation electrodes were attached onto the torso in the ventrodorsal direction and connected to a biphasic defibrillator. Animals were randomized either to (1) hands-on defibrillation, where rescuers wore 2 pairs of polyethylene gloves and shocks were delivered during ongoing chest compressions, or (2) hands-off defibrillation, where hands were taken off during defibrillation. CPR was successful in 9 out of 10 animals in the hands-on group (versus 8 out of 10 animals in the hands-off group; not significant). In the hands-on group, chest compressions were interrupted for 0.8% [0.6%; 1.4%] of the total CPR time (versus 8.2% [4.2%; 9.0%]; P=0.0003), and coronary perfusion pressure was earlier restored to its pre-interruption level (P=0.0205). Also, rescuers neither sensed any kind of electric stimulus nor did Holter ECG reveal any serious cardiac arrhythmia.

Conclusions: Hands-on defibrillation may improve CPR quality and could be safely performed during uninterrupted chest compressions in our standardized porcine model.

Keywords: cardiac arrest; cardiopulmonary resuscitation; chest compression; defibrillation; resuscitation.

Figure 1.

Experimental setup. One defibrillation electrode was attached on the right half of the anterior thorax and a second electrode in a posterolateral position on the left thorax. Both electrodes were connected to a biphasic defibrillator. The cross indicates placement of rescuer's hands.

Figure 2.

Experimental timeline. Animals were prepared and fibrillated under general anesthesia. After 7 minutes of cardiac arrest, all animals received CPR starting with 2 minutes of basic life support (BLS) and subsequent advanced life support (ALS) with alternating administration of epinephrine and vasopressin. After 4 minutes of CPR, all animals were defibrillated every 2 minutes.

Figure 3.

Illustration of CPR efficacy measures. After every interruption of chest compressions (CCs), several compressions are needed to restore coronary perfusion pressure (CorPP) back to its preinterruption level. For our efficacy end points, we measured both (A) the interval of the interruption (no flow time and (B) the duration of the restoration of CorPP (restoration time).

Figure 4.

Each drop in these survival curves indicates return of spontaneous circulation (ROSC). Survival analysis did not reveal significant differences between groups in the duration of cardiopulmonary resuscitation (log-rank test, P=0.7021). In prolonged resuscitation swine tend to benefit from hands-on technique.

Figure 5.

Results of CPR efficacy measures. No flow time as the sum of all chest compression (CC) interruption intervals related to total cardiopulmonary resuscitation (CPR) time (A) and restoration ratio of coronary perfusion pressure (CorPP) as the ratio of cumulative restoration time of CorPP to total CPR time (B) for each swine that received >1 shock (hands-on group n=7, hands-off group n=8; we excluded from further analysis 3 animals in the hands-on group and 2 animals in the hands-off group that received only 1 shock). Scatter plots with medians are shown.

Figure 6.

Blood lactate distribution over time. To show the efficacy of removal of lactate sequestered in tissue into central circulation, we determined lactate level at baseline, 5 minutes after initiation of cardiopulmonary resuscitation (CPR), and 5, 30, 60, 120, and 240 minutes after return of spontaneous circulation (ROSC). Peak of lactate appeared much earlier in the hands-on group, suggesting a more intensive reperfusion shortly after ROSC. Error bars show interquartile range.