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 controlled, randomized trials.¶Design: Retrospective chart analysis with historical controls.¶Setting: Tertiary neonatal intensive care unit of the University of Cape Town, South Africa.¶Patients: Twenty-one asphyxiated newborns treated with induced hypothermia between September 1997 and February 1998 were compared to 15 asphyxiated newborn infants admitted during March to August 1997. The two groups of infants did not differ in patient characteristics or severity of asphyxia (comparison 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 coolpacks, at a temperature of about 10 °C, around the head of asphyxiated newborn infants to maintain the nasopharyngeal temperature between 34 and 35 °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 (median 77.5 h, range 22 to 185 h) and resulted in an average nasopharyngeal temperature of 34.6 ± 0.5 °C. Hypothermia reduced abdominal skin temperature from 36.3 ± 0.5 °C to 35.1 ± 0.35 °C (p = 0.0001), heart rate from 139 ± 21 to 121 ± 13 beats/min (p < 0.0001) and respiratory 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 hypoglycaemia and urinary output, blood in urine or tracheal secretion between the two groups were observed. In the survivors the neurological score, assessed at day 2 and day 5, fell from 10.9 ± 3.5 to 8.1 ± 4.5 in the hypothermia group and rose from 8.1 ± 2.5 to 9.0 ± 3.1 in the comparison group (p = 0.003).¶Conclusions: Adverse effects of mild hypothermia induced for 3 days in asphyxiated newborns were significantly less than expected from previous reports on neonates with accidental hypothermia.