The Relationship Between Bispectral Index And Targeted Propofol Concentration Is Biphasic In Major Burns Patients

The Relationship Between Bispectral Index And Targeted Propofol Concentration Is Biphasic In Major Burns Patients.

TaeHyung Han. Department of Anesthesiology and Pain Medicine, Hangang Sacred Heart Hospital, Hallym University, College of Medicine. Seoul, Korea

Background:

This study was conducted to assess changes in bispectral index (BIS) caused by increasing target propofol effect-site concentration during target-controlled infusion (TCI) in major burns.

Methods:

Eighteen patients, ASA physical status 2 or 3, aged from 20 to 55 year old, weight 50 - 70 kg, with major burns, scheduled for elective early escharectomy less than a week after injury were recruited. A further 18 ASA physical status class 1 or 2, non-burns, age, sex and weight matched adult patients, scheduled for elective surgery under general anesthesia, were recruited as controls. During anesthesia induction, target propofol effect site concentrations were increased by increments of 0.5 μg mL-1 up to 4.5 μg mL-1. The BIS responses to each target concentration using TCI were compared in both groups. Results. In the burns group, significantly greater BIS values relating to increasing propofol TCI were noted at deeper anesthesia when compared with controls; at ³ 3.5 μg mL-1, mean BIS remained at a plateau of about 50. Burns patients had higher cardiac indices and lower hemoglobin and albumin concentrations than controls.

Conclusions:

In major burns, numerous other variables such as BIS algorithm, TCI performance and altered propofol pharmacokinetics and pharmacodynamics determine the final biphasic BIS responses. The importance of individually tailored approach with careful anesthetic titration based upon the patient’s clinical condition and responses cannot be overemphasized.

Fig 1. The changes of bispectral index as a function of targeted effect site concentrations of propofol. At over 3.5 mg·mL^-1, mean BIS remains increased in the burns patients. Data are expressed as mean ± SD. ^*P < 0.05 when compared to controls. P values are derived from repeated measures of ANOVA with Bonferroni correction.