Early adrenaline administration does not improve circulatory recovery during resuscitation from severe asphyxia in newborn piglets.

Aim Of The Study: To investigate the effects of early intravenous adrenaline administration on circulatory recovery, cerebral reoxygenation, and plasma catecholamine concentrations, after severe asphyxia-induced bradycardia and hypotension.

Methods: One-day-old piglets were left in apnoea until heart rate and mean arterial pressure were less than 50 min(-1) and 25 mmHg, respectively. They randomly received adrenaline, 10 μgkg(-1) (n=16) or placebo (n=15) and were resuscitated with air ventilation and, when needed, closed-chest cardiac massage (CCCM). Eight not asphyxiated animals served as time controls.

Results: CCCM was required in 13 piglets given adrenaline and in 13 given placebo. Time to return of spontaneous circulation was: 72 (66-85)s vs. 77 (64-178)s [median (quartile range)] (p=0.35). Time until cerebral regional oxygen saturation (CrSO(2)) had increased to 30% was 86 (79-152)s vs. 126 (88-309)s (p=0.30). The two groups did not differ significantly in CrSO(2), heart rate, arterial pressure, right common carotid artery blood flow, or number of survivors: 13 vs. 11 animals. Plasma concentration of adrenaline, 2.5 min after resuming ventilation, was 498 (268-868)nmoll(-1) vs. 114 (80-306)nmoll(-1) (p=0.01). Corresponding noradrenaline concentrations were 1799 (1058-4182)nmoll(-1)vs. 1385 (696-3118)nmoll(-1) (ns). In the time controls, the concentrations were 0.4 (0.2-0.6)nmoll(-1) of adrenaline and 1.8 (1.3-2.4)nmoll(-1) of noradrenaline.

Conclusion: The high endogenous catecholamine levels, especially those of noradrenaline, may explain why early administered adrenaline did not significantly improve resuscitation outcome.