Topical ice slurry prevents brain rewarming during deep hypothermic circulatory arrest in newborn sheep

Objectives: To measure the effect of ice slurry topical cooling on brain surface temperature during deep hypothermic circulatory arrest. Design: This was a prospective, controlled experiment. Setting: Animal laboratory at a university hospital Participants: Five Control lambs, five treatment (ice slurry) lambs. Interventions: Animals were studied in two groups: the study group had topical cooling of the head With ice slurry started immediately before circulatory arrest and continued throughout the period of circulatory arrest; control group lambs received no supplemental topical cooling. Measurements and Main Results: Brain surface temperature, scalp, nasopharyngeal, and rectal temperatures Were measured at 5-minute intervals during 45 minutes of circulatory arrest. Lambs receiving topical cooling of the head with ice slurry had a statistically significant decrease in brain surface temperature of 2.2 ± 1.2°C during circulatory arrest, whereas brain surface temperature increased 1.2 ± 0.3°C, in control lambs. Equilibration of temperature between the scalp and brain in Control lambs produced rewarming of the brain surface. Conclusions: Topical cooling of the head with ice slurry in newborn lambs lowers brain surface temperature during deep hypothermic circulatory arrest. Surrogate temperature monitoring locations such as nasopharyngeal and rectal temperatures varied significantly and do not accurately reflect changes in brain surface temperature.