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 50min(-1) and 25mmHg, respectively. They randomly received adrenaline, 10 μg kg(-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 (CrS(O2)) 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 CrS(O2), heart rate, arterial pressure, right common carotid artery blood flow, or number of survivors: 13 and 11 animals. Plasma concentration of adrenaline, 2.5min after resuming ventilation, was 498 (268-868) nmol l(-1)vs. 114 (80-306) nmol l(-1) (p=0.01). Corresponding noradrenaline concentrations were 1799 (1058-4182) nmol l(-1)vs. 1385 (696-3118) nmol l(-1) (ns). In the time controls, the concentrations were 0.4 (0.2-0.6) nmol l(-1) of adrenaline and 1.8 (1.3-2.4) nmol l(-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.