Immediate Hypothermia Reduces Cardiac Troponin I After Hypoxic-Ischemic Encephalopathy in Newborn Pigs

Abstract

Neonatal hypoxic-ischemic encephalopathy (HIE) is a clinically defined neurological condition after lack of oxygen and often associated with cardiac dysfunction in term infants. Therapeutic hypothermia (HT) after birth is neuroprotective in infants with HIE. However, it is not known whether HT is also cardioprotective. Four newborn pigs were used in the pilot study and a further 18 newborn pigs [randomly assigned to 72 h normothermia (NT) or 24 h HT followed by 48 h NT] were subjected to global HIE insults. Serum cTnI was measured before and post the HIE insult. Blood pressure, inotropic support, blood gases, and heart rate (HR) were recorded throughout. Cardiac pathology was assessed from histological sections. Cooling reduced serum cTnI levels significantly in HT pigs by 6 h (NT, 1.36 ± 0.67; HT, 0.34 ± 0.23 ng/mL; p = 0.0009). After rewarming, from 24 to 30 h postinsult, HR and cTnI increased in the HT group; from HR[24 h] = 117 ± 22 to HR[30 h] = 218 ± 32 beats/min (p = 0.0002) and from cTnI[24 h] = 0.23 ± 0.12 to cTnI[30 h] = 0.65 ± 0.53 ng/mL, (p = 0.05). There were fewer ischemic lesions on cardiac examination (37%) in the HT group compared with the NT group (70%). HT (24 h) pigs did not have the postinsult cTnI increase seen in NT-treated pigs. There was a trend that HT improved cardiac pathology in this 3-d survival model.