Background Therapeutic hypothermia reduces neurological damage and improves survival in neonatal encephalopathy. Despite treatment, however, 50% infants have adverse outcomes. Clinical trials are investigating lower cooling temperatures as tailoring cooling may be beneficial.

Objective To assess systemic effects of cooling to 35, 33 and 30°C in a piglet model of perinatal asphyxia.

Design/methods 28 male piglets, <24 h, underwent hypoxia-ischaemia and randomized (groups n=7), with intervention from 2 to 26 h to (i) normothermia; (ii) hypothermia (35°C); (iii) hypothermia (33.5°C); intravenous) hypothermia (30°C). Heart rate (HR), mean arterial blood pressure (MABP) and rectal temperature (Trec) were recorded continuously; blood chemistry every 6 h.

Results Five animals in the 30°C group died before 48 h due to cardiac arrest, no piglets died prematurely in other groups. During cooling, HR was similar at 30°C versus 35 and 33.5°C and MABP did not differ between groups. However, inotrope and volume replacement were higher at 30°C versus all other groups (p<0.001). Blood pH was lower at 12 and 24 h (p<0.001) at 30°C versus all other groups (figure 1A). Blood glucose, lactate and BE were abnormal at 24 h (all p< 0.05) at 30°C versus all other groups (figures 1B–D).

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Abstract 8B.2 Figure 1

Mean (SD) saline bolus and inotrope infusions over 48 h in the four groups. *p<0.001.

Conclusions Cooling to 30°C required extensive cardiovascular support and led to significant metabolic derangement and more cardiac arrests. Despite similar MABP in all groups, systemic effects at 30°C were considerable and may be deleterious to the brain.