Neonatal Ischemic Neuroprotection by Modest Hypothermia Is Associated With Attenuated Brain Acidosis

Abstract

Background and Purpose A 2.9°C reduction in the intraischemic rectal temperature of neonatal piglets is associated with less brain damage compared with animals with normothermic rectal temperatures. This investigation studied one potential mechanism for this observation: better maintenance of energy stores and less brain acidosis secondary to reduced metabolic activity associated with modest hypothermia. Methods 31P MR spectroscopy was used to study piglets before, during, and after 15 minutes of partial brain ischemia with intraischemic rectal temperatures of either 38.3±0.4°C (n=10, normothermic) or 35.4±0.5°C (n=10, hypothermic). Animals were followed up for up to 72 hours after ischemia and were evaluated clinically and by brain histology. Results Values for pHi remained 0.15 to 0.20 pH units greater in modestly hypothermic than in normothermic piglets during ischemia and the initial 30 minutes after ischemia (P=.049, group effect). Phosphocreatine, β-ATP, and inorganic phosphorus were similar between...