Unexpected 100% survival following 60% blood loss using small-volume 7.5% NaCl with adenocaine and Mg(2+) in the rat model of extreme hemorrhagic shock.

Hemorrhage is responsible for up to 40% of trauma mortality, and of these deaths, 33% to 56% occur during the prehospital period. In an effort to translate the cardioprotective effects of Adenocaine (adenosine, lidocaine) and Mg (ALM) from cardiac surgery to resuscitation science, we examined the early resuscitative effects of 7.5% NaCl with ALM in the rat model of 60% blood loss. Male Sprague-Dawley rats (250-350 g, n = 40) were anesthetized and randomly assigned to one of five groups: (a) untreated, (b) 7.5% NaCl, (c) 7.5% NaCl/6% dextran 70, (d) 7.5% NaCl/Mg, and (e) 7.5% NaCl/ALM. Blood withdrawal occurred over ∼50 min (MAP 30-35 mmHg), and rats were left in shock for 30 min. Total shock time was ∼80 min; 0.3-mL bolus was injected intravenously over 10 s, and hemodynamics monitored for 60 min (phase 1). Shed blood was reinfused and function monitored for a further 60 min (phase 2). Lead II electrocardiogram, arterial pressures, mean arterial pressure (MAP), pulse pressure (PP), heart rate (HR), and rate-pressure product were monitored. Mortality was as follows: untreated (100%), 7.5% NaCl (75%), 7.5% NaCl/6% dextran 70 (87.5%), 7.5% NaCl/Mg (62.5%), and 7.5% NaCl/ALM (0%). Deaths occurred at different times depending on treatment group and paralleled differences in the total number of ventricular arrhythmias with the highest number in untreated animals (49 ± 17) and lowest in 7.5% NaCl/ALM rats (2 ± 1.8) (P < 0.05). At the end of phase 1, MAP of 7.5% NaCl/ALM-treated animals increased from 29 to 40 mmHg (P < 0.05). At the end of phase 2, MAP, PP, HR, and rate-pressure product in the ALM group were 75%, 193%, 96%, and 83% of their preshock values. Small-volume (∼1 mL/kg) i.v. bolus of 7.5% NaCl/ALM led to 100% survival following 60% blood loss with higher MAP than any group, an 89% to 96% reduction in the total number of arrhythmias, and a stable HR.