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Introduction: Continuous Regional Brain Perfusion (CRBP) is been used through periods of deep hypothermic circulatory arrest (DHCA) to minimize ischemic brain injury. However, optimal CRBP flows have not been determined. Visible Light Spectroscopy (VLS) is a reliable method for continuous determination of capillary saturations (SgvO₂). We used VLS in order to follow deep and superficial brain SgvO₂ through cardiopulmonary bypass (CPB), CRBP and DHCA.
Methods: VLS probes were inserted into the superficial and deep brain of neonatal (3.9-4.5kg) piglets targeting the caudate and thalamic nuclei The piglets were subject to CPB and were cooled to rectal temperature of 18°C using pH stat. CRBP was initiated through the innominate artery at 18°C, and pump flows were adjusted to 40, 30, 20, and 10cc/kg/min for 10 min intervals. Subsequently, DHCA was initiated and maintained for 30 minutes. CRBP was re-established and flows were increased stepwise. Continuous SgvO₂ values were recorded. Cerebral flow (CF, cc/kg/min) was measured using a carotid flow probe.
Results: Cerebral SgvO₂ were maintained at pump flows of 20-40 cc/kg/min and cerebral flows of 14-24cc/kg/min. Pump flows of 10 cc/kg/min and cerebral flows of 5-10cc/kg/min were inadequate in maintaining brain SgvO₂%. Table number 1 displays SgvO₂ and cerebral flows during CPB, CRBP and DHCA.