Delayed hypothermia as selective head cooling or whole body cooling does not protect brain or body in newborn pig subjected to hypoxia-ischemia

Abstract

The neuroprotective efficacy of hypothermia (HT) after hypoxia-ischemia (HI) falls dramatically the longer the delay in initiating HT. Knowledge is scarce regarding protective or adverse effects of HT in organs beyond the brain. In addition, the relative effectiveness of selective head cooling (SHC) and whole body cooling (WBC) has not been studied. We aimed to examine whether 24 h HT, initiated 3 h after global HI is brain- and/or organ-protective using pathology, neurology, and biochemical markers. Fifty, ≤1-d-old pigs were subjected to global HI causing permanent brain injury. Animals were randomized to normothermia (NT), (Trectal) 39.0°C, SHCTrectal 34.5°C, or WBCTrectal 34.5°C for 24 h, all followed by 48 h NT. There was no difference in injury to the brain or organs between groups. There was no gender difference in brain injury but females had significantly more organs injured [2.3 (± 1.3) [mean ± SD] vs. 1.4 ± (1.0)]. The postinsult decline in lactate was temperature independent. However, HT animals normalized their plasma-calcium, magnesium, and potassium significantly faster than NT. Delayed SHC or WBC, initiated 3 h after HI, does not reduce pathology in the brain nor in organs. Delayed HT improves postinsult recovery of plasma-calcium, magnesium, and potassium. There were no differences in adverse effects across groups. Copyright © 2008 International Pediatric Research Foundation, Inc.