Posthypoxic cooling of neonatal rats provides protection against brain injury.

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) degrees C) or normothermia (38.3 (0.4) degrees 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.