We suggest it pulmonary uptake during the bolus infusion of propofol affects the time at loss of consciousness

National Defence Medical College anesthesiology classroom

Marimo Kira,D.D.S., Isao Fukuda,M.D., Yoshihiko Aramaki,M.D.,Tomiei Kazama,M.D.,Ph.D.

Background:

It is known that there are some individual variations the dosage at loss of consciousness.

Some reports reviewed that various kinds of factors influenced these individual variations. We hypothesize that pulmonary uptake during the bolus infusion of propofol affects the time at loss of consciousness.

Materials and methods:

Thirty patients were included in the study. American Society of Anesthesiologist (ASA) physical status I-II, aged 25-50 years, who were scheduled for gynecological surgery in National Defense Medical College Hospital. All patients were not premedicated. After routine monitors were applied, cardiac index, circulating blood volume, and effective liver blood flow were measured using the DDG analyzer ^TM before the bolus infusion of propofol. Propofol (1mg / kg ) was injected at 1800mg / kg / h.

Afterwards, arterial blood samples were taken every five seconds from beginning of infusion for 120 seconds. The time at loss of consciousness was recorded when the patients were not asleep with the predetermined propofol dose, they were induced with additional propofol. Anesthesia was maintained with propofol infusion and epidural block. At the end of surgery, propofol infusion rate was decreased gradually and arterial blood propofol concentrations at emergence were measured.Thirty

Results:

Eleven patients of 30 patients (Group S) were asleep with 1 mg/kg of propofol. The other with out.(Group N). There were no significant differences, age, body mass index, cardiac index before propofol administration, circulatory dynamics and effective liver blood between the groups. Though the peak blood concentration of propofol did not have the significant difference between both groups, the peak effect-site concentration in Group S was significantly higher than that in Group N. The AUC of 1st circulation of Group S was larger than that of Group N.

Conclusions:

It is suggested that pulmonary uptake during the bolus infusion of propofol affects the loss of consciousness,　in the first circulation without liver metabolism .