Serum concentrations and urinary excretion of lidocaine and its two desethylated metabolites after spinal anaesthesia using lidocaine or lidocaine with phenylephrine

Abstract

In 13 patients undergoing transurethral prostatic resection under spinal anaesthesia with heavy lidocaine or with heavy lidocaine plus phenylephrine hydrochloride, the serum concentrations of lidocaine, monoethylglycinexylidide and glycinexylidide and their renal excretion were measured with a HPLC method. Seven patients were given lidocaine alone 1.25 mg/kg and six lidocaine 1.25 mg/kg mixed with phenylephrine hydrochloride 3 mg. There was no significant difference between the two groups either in the serum levels of lidocaine or in the renal excretion rate of lidocaine and its metabolites. This finding gives support to the opinion that phenylephrine in low doses has no prolonging effect on spinal anaesthesia performed with heavy lidocaine.