Posthypoxic cooling of neonatal rats provides protection against brain injury

Abstract

Aim - To determine whether moderate hypothermia, applied after a hypoxic-ischaemic insult in neonatal rats, reduces cerebral damage. Method - Unilateral hypoxic-ischaemic brain damage was induced in 7 day old rats by left carotid ligation, followed by 120 minutes of normothermic exposure to 8% O2, followed by random selection to three hours of hypothermia (rectal temperature, mean (SD), 32.5 (0.4)°C) or normothermia (38.3 (0.4)°C). One hundred and one animals were used for brain temperature or blood chemistry studies and 24 for survival studies (7 days) with neuropathology, including cell counting as outcome measures. Results - Thirty sections from each brain were histologically examined with respect to distribution and pattern of damage and given a score from 0 to 4. Animals treated with hypothermia had significantly less damage than normothermic animals (score 0.5 (0.3) vs 1.8 (0.5)). Conclusions - Posthypoxic hypothermia reduces brain damage in awake, unrestrained 7 day old rats.