Study questions 2005 ACLS guideline change

One of the changes recommended in the 2005 ACLS guidelines (GL 2005) over the 2000 guidelines (GL 2000) was that after a defibrillation shock CPR be resumed immediately without pause for a pulse and rhythm check. The rationale was two fold: 1) After a successful shock there is typically a period of several seconds of PEA, marked bradycardia or asystole before spontaneous circulation resumes and 2) the shock may be unsuccessful, in which case immediate resumption of CPR will more effectively replete myocardial ATP stores thus increasing the likelihood of success of the next shock.

Now there is a disturbing report of a possible downside to the guideline changes: resumption of compressions may shorten the time to recurrent VF:

Of 361 patients, 136 met the inclusion criteria: 68 were randomly assigned to GL2000 and 68 to GL2005. Rescuers resumed CPR 30 (21-to-39) and 8 (7-to-9) seconds, respectively, after the first shock that successfully terminated VF (P less than 0.001); VF recurred after 40 (21-to-76) and 21 (10-to-80) seconds, respectively (P=0.001). The time interval between start of CPR and VF recurrence was 6 (0-to-67) and 8 (3-to-61) seconds, respectively (P=0.88). The hazard ratio for VF recurrence in the first 2 seconds of CPR was 15.5 (95% confidence interval, 5.63 to 57.7) compared with before CPR resumption. After more than 8 seconds of CPR, the hazard of VF recurrence was similar to before CPR resumption.

Conclusions— Early CPR resumption after defibrillation causes early VF recurrence.

We don't know what this ultimately means in terms of outcomes. The advantages of the more aggressive CPR strategy in GL2005 may outweigh an increased risk of earlier recurrent VF.