Regional cerebral blood flow and glucose utilization during hypothermia in newborn dogs

To ascertain the effect of profound hypothermia on brain function and metabolism, newborn dogs were subjected to surface cooling during which regional cerebral blood flow (rCBF) and glucose utilization (rCGU) were measured with iodo-[14C]-antipyrine and 2-deoxy-[14C]-glucose, respectively. Puppies were anesthetized with nitrous oxide, paralyzed, and their lungs artificially ventilated to maintain arterial normoxia (PaO2 greater than 60 mmHg) and normal acid-base balance (PaCO2 = 35-41 mmHg; pHa = 7.34-7.42). When rectal temperature was decreased from 37 to 20 degrees C, mean arterial blood pressure (MABP) decreased from 75 to 47 mmHg (P less than 0.001) and heart rate from 238 to 64 beats/min (P less than 0.001). Arterial PCO2 was reduced from 38 to 31 mmHg (P less than 0.001) (corrected to 37 degrees C), whereas pHa was unchanged from control (7.40). The electroencephalogram slowed progressively and became isoelectric at 22-25 degrees C. During normothermia (n = 6) blood flow to 16 component structures of brain varied from 17 (occipital white matter) to 65 (medulla) ml.100 g-1.min-1, whereas during hypothermia (n = 6) blood flow was lower in all regions (P less than 0.001) at remarkably uniform levels 8.3-10.3 ml.100 g-1.min-1). Thus, the greatest reductions (range, 16-48% of control) in CBF occurred in those structures with the highest intrinsic flows during normothermia and were proportionately less in low flow structures. Regional CGU also decreased in all brain regions analyzed (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)