C OMBINATION P HARMACOTHERAPY WITH D ELAYED C OUNTERSHOCK VS S TANDARD A DVANCED C ARDIAC L IFE S UPPORT A FTER P ROLONGED V ENTRICULAR F IBRILLATION

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Abstract
To test the hypothesis that combination pharmacotherapy with delayed countershock would produce higher rates of return of spontaneous circulation (ROSC) and one-hour survival when compared with standard Advanced Cardiac Life Support (ACLS) therapy. A prospective, block-randomized, blinded, laboratory experiment was conducted in an established swine model of prolonged ventricular fibrillation (VF). Fifty-six female domestic swine were anesthetized, instrumented, and shocked into VF with a bipolar pacing catheter. The VF was untreated for 8 minutes, then basic CPR was done mechanically for 1 minute. At 9 minutes of VF, the animals were randomized to treatment with one of seven therapies: group 1, combination pharmacotherapy with epinephrine (0.20 mg/kg), lidocaine (1.0 mg/kg), bretylium (5.0 mg/kg), propranolol (1.0 mg), and U-74389G (3.0 mg/kg); group 2, epinephrine (0.20 mg/kg); group 3, lidocaine (1.0 mg/kg) and bretylium (5.0 mg/kg); group 4, propranolol (1.0 mg); group 5, U-74389G (3.0 mg/kg); group 6, normal saline solution (volume equal to that for group 1); and group 7, standard ACLS (first countershock at 9 minutes of VF). Initial countershocks for groups 1-6 were given after 11 minutes of VF. Data were analyzed with two-tailed Fisher's exact test, with alpha set at 0.05. Return of spontaneous circulation occurred in group 1 = 8/8 (100%); group 2 = 7/8 (88%); group 3 = 3/8 (38%); group 4 = 3/8 (38%); group 5 = 5/8 (63%); group 6 = 4/8 (50%); and group 7 = 3/8 (38%). One-hour survival occurred in group 1 = 8/8 (100%); group 2 = 5/8 (63%); group 3 = 2/8 (25%); group 4 = 2/8 (25%); group 5 = 3/8 (38%); group 6 = 2/8 (25%); and group 7 = 1/8 (13%). Combination pharmacotherapy with delayed countershock (group 1) produced significantly higher rates of ROSC (p = 0.03) and one-hour survival (p = 0.001) when compared with standard ACLS in this porcine model of prolonged VF.