Blood concentrations of tetracaine and its metabolite following spinal anesthesia.

Blood concentrations of tetracaine and its metabolite, p-butylaminobenzoic acid, were measured after spinal anesthesia with tetracaine which had been administered to patients under going orthopedic surgery. Tetracaine, an ester anesthetic, was given to 10 patients, the dose was 8-14mg, and blood samples were collected 1, 2 and 6h after the injection of tetracaine. We used gas chromatography/mass spectrometry for purposes of analysis. Tetracaine was not detected in any blood sample, but the metabolite was detected in each sample with the mean concentrations of 126.5, 97.9 and 43.3ng/ml at 1, 2 and 6h, respectively. This data will be useful in determination of the cause of death after spinal anesthesia with tetracaine.