Organ transplantation from
brain death patients started in Japan in 1997. However it is difficult to diagnose
brain death in patients treated with
barbiturate therapy. In this study, the influence of long continuous administration of
barbiturate on diagnosis of
brain death was investigated by measuring plasma concentration of
barbiturate. In 15 patients treated with
barbiturate therapy, plasma concentrations of
thiamylal were measured by liquid chromatographic apparatus every day until it's level decreased below 0.1 microgram/ml after cessation of continuous administration. At the same time, plasma
thiamylal levels were checked on the day when burst-suppression (b-s) pattern had disappeared in 9 cases, light reflex of pupil appeared in 7 cases and spontaneous respiration had been detected by trigger lamp in 11 cases. The plasma concentrations of
thiamylal on the day when b-s pattern had disappeared differed clearly among the cases in the range of 8.8 to 37.9 micrograms/ml. Those cases in which light reflex of the pupil had been recognized were also different in the range of 17.8 to 57.8 micrograms/ml. The cases in which spontaneous respiration had been detected were in the range of 4.4 to 23.0 micrograms/ml. These concentrations varied about 4, 3 and 5 times among the cases examined. The intervals between cessation of continuous administration of
thiamylal and the decrease of plasma concentration to below 0.1 microgram/ml also varied from 2 to 14 days from case to case. The minimum concentration of
thiamylal on the day when b-s pattern had disappeared, light reflex of the pupil had been recognized and spontaneous respiration had been detected was 8.8, 17.8 and 4.4 micrograms/ml respectively. These results suggest that diagnosis of
brain death in patients treated with
barbiturate therapy is able to be made when the plasma
thiamylal level is below 4.4 micrograms/ml.