Lipid emulsion is superior to vasopressin in a rodent model of resuscitation from toxin-induced cardiac arrest

Objectives: Lipid emulsion infusion is an emerging antidotal therapy for toxin-induced cardiac arrest. To compare the efficacy of resuscitation from bupivacaine-induced asystole using lipid emulsion infusion vs. vasopressin, alone and with epinephrine. Design: Prospective, randomized, animal study. Setting: University research laboratory. Subjects. Adult, male Sprague-Dawley rats. Interventions: Instrumented rats were given an intravenous bolus of 20 mg/kg bupivacaine to induce asystole (zero time). Rats (n = 6 for all groups) were ventilated with 100% oxygen, given chest compressions, and randomized to receive 30% lipid emulsion (L, 5 mL/kg bolus then 1.0 mL/kg/min infusion) and vasopressin 0.4 U/kg bolus alone (V) or combined with epinephrine, 30 mu g/kg (V + E); boluses (L, V, or V + E) were repeated at 2.5 and 5 minutes for a rate-pressure product (RPP) less than 20% baseline. Measurements and Main Results: The arterial blood pressure and electrocardiogram were measured continuously for 10 minutes when blood was drawn for arterial blood gas analysis, lactate content, and central venous oxygen saturation (ScvpO2). Hemodynamic parameters of the L group at 10 minutes (30,615 +/- 4782 mm Hg/min; 151 +/- 19.1 mm Hg; 197 +/- 8.6 min(-1); RPP, systolic blood pressure and heart rate, respectively) exceeded those of the V group (5395 +/- 1310 mm Hg/min; 85.8 +/- 12 mm Hg; 61 +/- 10.8 min(-1)) and the V + E group (11,183 +/- 1857 mm Hg/min(-1); 75.5 +/- 12.9 min(-1), RPP and heart rate, respectively; systolic blood pressure was not different). Metrics indicated better tissue perfusion in the L group (7.24 +/- 0.02; 83% +/- 3.5%; 2.2 +/- 0.36 mmol/L; pH, ScvpO2 lactate, respectively) than V (7.13 +/- 0.02; 29.9% +/- 4.4%; 7.5 +/- 0.6 mmol/L) and V + E groups (7.07 +/- 0.03; 26.2% +/- 8.9%; 7.7 +/- 1 mmol/L). Wet-to-dry lung ratios in V (8.3 +/- 0.6) and V + E (8.7 +/- 0.2) were greater than that in the L group (6.2 +/- 05) (mean +/- SEM; P < 0.05 for all shown results). Conclusions. Lipid emulsion in this rat model provides superior hemodynamic and metabolic recovery from bupivacaine-induced cardiac arrest than do vasopressors. Systolic pressure was not a useful metric in the vasopressor groups. Vasopressin was associated with adverse outcomes. (Crit Care Med 2009; 37:993-999)