Induced brain hypothermia in asphyxiated human newborn infants: a retrospective chart analysis of physiological and adverse effects

Objective: To assess the physiological effects and adverse side-effects of induced hypothermia in asphyxiated newborn infants as a base for future con trolled, randomized trials. Design: Retrospective chart analysis with historical controls. Setting: Tertiary neonatal intensive care unit of the University of Cape To wn, South Africa. Patients: Twenty-one asphyxiated newborns treated with induced hypothermia between September 1997 and February 1998 were compared to 15 asphyxiated ne wborn infants admitted during March to August 1997. The two groups of infan ts did not differ in patient characteristics or severity of asphyxia (compa rison group vs hypothermia group: Apgar at 5 min 5.3 +/- 3.1 vs 5.2 +/- 2.3 ; base deficit 15.6 +/- 6.3 vs 11.5 +/- 7.2 and Thompson neurological score 10.1 +/- 4.0 Vs 9.1 +/- 3.6). Interventions: Hypothermia was induced by placing a cap formed from coolpac ks, at a temperature of about 10 degrees C, around the head of asphyxiated newborn infants to maintain the nasopharyngeal temperature between 34 and 3 5 degrees C. Hypothermia was maintained for 3 days. Measurements and results: In the comparison group 4/15 infants died and in the hypothermia group 4/21 died. Hypothermia was induced at a median of 6.0 h (range 45 min to 53 h) post-partum, maintained for an average of 80 h (m edian 77.5 h, range 22 to 185 h) and resulted in an average nasopharyngeal temperature of 34.6 +/- 0.5 degrees C. Hypothermia reduced abdominal skin t emperature from 36.3 +/- 0.5 degrees C to 35.1 +/- 0.35 degrees C (p = 0.00 01), heart rate from 139 +/- 21 to 121 +/- 13 beats/min (p < 0.0001) and re spiratory rate from 67 +/- 11 to 56 +/- 9 breaths/min (p = 0.005). Neither episodes of bradycardia nor dysrhythmias, apnea, clinical signs of bleeding diathesis in the hypothermia group nor differences in the frequency of hyp oglycaemia and urinary output, blood in urine or tracheal secretion between the two groups were observed. In the survivors the neurological score, ass essed at day 2 and day 5, fell from 10.9 +/- 3.5 to 8.1 +/- 4.5 in the hypo thermia group and rose from 8.1 +/- 2.5 to 9.0 +/- 3.1 in the comparison gr oup (p = 0.003). Conclusions: Adverse effects of mild hypothermia induced for 3 days in asph yxiated newborns were significantly less than expected from previous report s on neonates with accidental hypothermia.