SPINAL-ANESTHESIA IN NEWBORNS - TOTAL AND FREE BUPIVACAINE PLASMA-CONCENTRATION

This study was designed to measure total and free bupivacaine (B) afte r spinal anaesthesia in newborns and to evaluate a possible influence of adrenaline on B absorption. Twenty-two newborns were randomly alloc ated to receive either plain B (group 1) or adrenaline added to B (gro up 2) for spinal anaesthesia. A single blood sample was collected ten min after spinal injection. Total B concentration was found 0.31 +/- 0 .17 mu g . ml(-1) in group 1 and 0.25 +/- 0.09 mu g . ml(-1) in group 2. Bound B concentration was 0.27 +/- 0.17 mu g . ml(-1) in group 1 an d 0.22 +/- 0.09 mu g . ml(-1) in group 2. No difference was found betw een the two groups for these parameters. Albumin but not alpha 1-acid- glyco-protein correlated to age and weight, bound B correlated to alph a 1-acid-glyco-protein but not to albumin. Despite the low plasma conc entration of binding proteins in newborns, spinal anaesthesia with B d oes not result in a high level of free drug. Adrenaline does not have any pharmacological advantage in these patients.