AWAKENING PROPOFOL CONCENTRATION WITH AND WITHOUT BLOOD-EFFECT SITE EQUILIBRATION AFTER SHORT-TERM AND LONG-TERM ADMINISTRATION OF PROPOFOLAND FENTANYL ANESTHESIA
T. Kazama et al., AWAKENING PROPOFOL CONCENTRATION WITH AND WITHOUT BLOOD-EFFECT SITE EQUILIBRATION AFTER SHORT-TERM AND LONG-TERM ADMINISTRATION OF PROPOFOLAND FENTANYL ANESTHESIA, Anesthesiology, 88(4), 1998, pp. 928-934
Background: The propofol awakening concentration can vary. However, th
e effect site awakening propofol concentration will be a fixed value.
The purpose of this study was to determine the awakening propofol conc
entrations obtained from infusion Schede using abrupt discontinuation
of propofol (half-maximal effective concentration [EC50]) or a descend
ing decrease in concentration to allow blood-effect site equilibration
(EC(50)eq). Methods: Patients undergoing short-term (group 1) and lon
g-term (group 2) elective surgery were anesthetized with computer-assi
sted continuous infusion of propofol and fentanyl with both groups rec
eiving the same propofol (3 mu g/ml) and fentanyl (1 ng/ml) concentrat
ions 20-30 min before the end of surgery until the end. Then both grou
ps were further divided into two subgroups: subgroup A abrupt disconti
nuation, and subgroup B descending concentrations of propofol (15-min
duration per concentration). In the A subgroups, the response to verba
l command was evaluated every 30 s. In the B subgroups, the blood prop
ofol concentrations just permitting and just preventing response to co
mmand were averaged individually. The EC50 and EC(50)eq values were de
termined by probit analysis. Results: The EC50 of group 1A was 1 mu g/
ml which was significantly less than the 1.6 mu g/ml of group 2A (P <
0.05). The awakening time of group 1A was 5.2 +/- 1.8 min, which was s
ignificantly shorter than the 9.3 +/- 3.5 min of group 2A (means +/- S
D). The EC(50)eq of both groups 1B and 2B was 2.2 mu g/ml. Conclusions
: The EC(50)eq was independent of propofol infusion length, compared w
ith the EC50. Thus the potential for hysteresis during emergence from
propofol anesthesia was confirmed.