CEREBRAL BLOOD-FLOW AND EXCHANGE OF OXYGEN, GLUCOSE, KETONE-BODIES, LACTATE, PYRUVATE AND AMINO-ACIDS IN INFANTS

Cerebral blood flow (CBF) and cerebral A-V[aterio-venous]-differences of O2 and circulating substrates were measured in normocapnic infants during general anesthesia before elective surgery to study possible age-dependent variations. CBF was determined by a minor modification of the Kety-Schmidt technique from desaturation curves of N2O in arterial and cerebral venous blood (N2O analyzed by gas chromatography on 15 .mu.l blood samples) after reduction of inhaled N2O from 75 to 50%. The reproducibility was .+-. 4.6%. Lactate, pyruvate and O2 were determined in whole blood and amino acids in plasma by ion-exchange chromatography. Reliable A-V-differences of glucose, acetoacetate and D-.beta.-hydroxybutyrate were calculated from plasma values and hematocrits. Mean values from 12 infants (age 11 days-12 mo.) were CBF 69 ml/100 g.cntdot.min-1, cerebral uptake (in .mu.moles/100 g.cntdot.min-1): oxygen 104, glucose 27, acetoacetate 0.9, D-.beta.-hydroxybutyrate 2.3; cerebral release: lactate 2.4 and pyruvate 0.8. Significant uptake of amino acids was found only for histidine 0.95 and arginine 0.7. Significant correlations between arterial concentration and cerebral exchange were found for ornithine, arginine, phenylalanine, aspartic acid, serine, glutamine and acetoacetate. CBF and substrate exchange were unrelated to age within the group. Infants had higher mean CBF and greater uptake of ketone bodies than reported in adults.