Inter-patient variability upon induction with sevoflurane estimated by the time to reach predefined end-points of depth of anaesthesia.
OBJECTIVE
A difficult issue in anaesthesia is its titration for an individual patient to avoid over- and underdosage. Common practice is to use an initial dose and increase it subsequently if the defined end-point is not reached. This assumes that the end-point is reached after a similar interval of time in all patients given a similar dose. In order to test this hypothesis we measured the time to reach end-points such as loss of consciousness (LOC), a bispectral index (BIS) value of 60, the minimal BIS and the minimal mean arterial pressure (MAP) values.


METHODS
Thirty patients aged 18-60 yr scheduled for general surgery were included in this observational study. After preoxygenation, induction was performed with 6% inspired concentration of sevoflurane in 6 Lmin-1 oxygen using the SiBI connector and the tidal volume technique. Remifentanil was administered when the BIS value was 60 and tracheal intubation was performed 4 min later.


RESULTS
Time (median, minimum-maximum) to LOC, a BIS value of 60, the minimal BIS and MAP values were, respectively, 75 (45-135), 120 (75-270), 300 (120-720) and 450 (120-1200) seconds. The time to the minimal BIS value was significantly (P < 0.05) shorter than the time to reach the minimal MAP value.


CONCLUSIONS
These results demonstrate large inter-patient variability for the time necessary to reach defined end-points of depth of anaesthesia when a similar dose of anaesthetic is given. Measuring the time to reach a predefined BIS value would allow application of nociceptive stimuli only at adequate levels of hypnosis and would facilitate titration.
Lambert
P
P
Centre Hospitalier Universitaire de Nancy, Department of Anaesthesia and Intensive Care, Hôpital Brabois,Vandoeuvre-les-Nancy, France.
Junke
E
E
Fuchs-Buder
T
T
Meistelman
C
C
Longrois
D
D
D000293:Adolescent; D000328:Adult; D000769:Anesthesia, Inhalation / Q000379:methods; D004569:Electroencephalography; D023381:Endpoint Determination / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage*; D008875:Middle Aged; D011237:Predictive Value of Tests; D000077149:Sevoflurane; D013997:Time Factors
D008738:Methyl Ethers; D000077149:Sevoflurane