Abstract 1202 Poster Session II, Sunday, 5/2 (poster 59)

Many issues regarding hypothermia and its systemic effects when used as neuroprotective therapy remain unclear. In this study we tested brain and systemic temperature dynamics during total body cooling (TBC n=4) and selective head cooling (SHC n=4) in newborn piglets. Methods: Under anesthesia, a burr-hole was made and a 22 gauge, 2.5 cm needle probe with five built-in temperature sensors was inserted into the parietal lobe with the tip near the thalamus. A dual-sensor probe was inserted into the kidney with the tip-sensor at the medulla and the proximal sensor in the cortex. Sensors were placed in the rectum, blood, oro-pharynx, and in the wall of the ileum. Temperature data were continuously recorded at 45-second intervals using a computerized device during 4 experimental periods: baseline (30 min); bilateral carotid occlusion with ∼10% oxygen breathing (HI 20 min), 60 min cooling using ice-cold blankets; and 60 min re-warming. Results: Time-averaged mean (SD) temperatures (in C) in TBC & SHC groups are shown. (Table) A 2-4° C temperature gradient remained between the deeper and superficial regions in both the kidney and brain during all periods in both groups (data not shown). 2) With TBC, the brain, and all the organs studied cooled far more (and were slower to re-warm) than with SHC; 3) With TBC, the ileum cooled the most-it was cooler than blood and brain; with SHC the ileum remained warmer than the blood. Conclusions: 1)Temperature changes in the brain and other organs may depend upon local blood flow, metabolic rates and their responses to hypothermia; 2) The methods of cooling and re-warming influence organ temperature dynamics. 3) Like the brain during selective head-cooling, surface cooling cools organs directly underneath. 4) The functional significance of these temperature changes need to be studied.

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