Heart rate response to therapeutic hypothermia in infants with hypoxic-ischaemic encephalopathy.

AIM OF THE STUDY: Neonatal encephalopathy (NE) of hypoxic-ischaemic origin may cause death or life-long disability which is reduced by therapeutic hypothermia (TH). Our objective was to assess HR response in infants undergoing TH after perinatal asphyxia.

METHODS

We performed a retrospective case series, from a single-centre tertiary care NICU. We included ninety-two infants with NE of likely hypoxic-ischaemic origin, moderate or severe, treated with TH (n=60) or normothermia (n=32) who had 18 month outcome data and at least 12 HR recordings the first 24h after birth (1998-2010) Bristol, UK. Poor outcome was defined as death or severe disability. Data are reported as medians and 95% confidence intervals (CI).

RESULTS

TH to 33.5°C decreased HR by 30bpm to 92bpm (95% CI: 88, 96) 12h after birth in infants with NE and good outcome as compared to infants treated at normothermia 118bpm (95% CI: 110, 130). Despite constant low rectal temperature, HR increased gradually during cooling from 36 to 72h to 97bpm (89, 106) approaching the normothermia group, 117bpm (96, 133). During TH, infants with poor outcome had higher HR at 12h after birth (112bpm, 95% CI: 92, 115) as compared to infants with good outcome (p=0.004). Inotropic support increased HR by 17bpm in infants with good outcome and by 22bpm in infants with poor outcome.

CONCLUSIONS

In NE, TH decreases HR the first day of life. HR remained lower during TH, but increased during the last day of TH. Infants with poor outcome have higher HR.