Download Bispectral Index ( BIS )Monitoring in Patients Undergoing Abstract

Bispectral Index ( BIS )Monitoring in Patients Undergoing
Abstract code: 1316
Authors: N. Hemmati; A. Zokaei, M. Niazi, R. Parsapoor
Address: Kermanshah Medical University
Background: Bispectral index (BIS) is a monitor of anesthetic depth wherein complex EEG
patterns are reduced to simple numbers in the range of 100 to 0. BIS decreases with increase
in depth of anesthesia and adequate anesthesia levels are supposedly achieved with BIS levels
of 40–60. The clinical usefulness of BIS, particularly during cardiac surgery is controversial
and inadequately addressed.
Methods: This study aims to study, in patients(CABG) the influence of deep anesthesia (BIS
40 range 35–45) on haemodynamics, oxygenation, use of additional vasodilators, time to
extubation, adequacy of anesthesia (awareness) and costs of the whole procedure. These are
compared with similar observations during normal levels of anesthesia (BIS 50, range 4055).Fourthy patients undergoing first time elective CABG with cardiopulmonary bypass
(CPB) were randomized into 2 groups. In group BIS 40 (20 patient) higher levels of
midazolam, sufentanil and pancuronium were chosen for induction and sufentanil infusion
was kept at1.5–2 μg/ Kg/h to achieve the target levels of 35-45. In comparison, lower doses
of all drugs including sufentanil infusion of 0.5–1.5 μg/ Kg/h was used in the BIS-50 (20
patient), group to achieve a target BIS of 45-55. In both groups, additional sufentanil,
midazolam and propofol were used as reserve medication. Haemodynamic parameters
studied were, heart rate (HR), mean arterial pressure (MAP),central venous pressures(CVP),
cardiac output (CO) with NICO and mixed venous oxygen saturation (SVO2). Derived
parameters were calculated using standard formulae. Arterial and mixed venous blood
analysis was used to calculate the indices of oxygen delivery and consumption.BIS was
measured at the frontal lobe of the dominant hemisphere and electrodes were replaced
whenever electrode impedence increased. Data were recorded at 6 different time points,
during
awake state, under steady state anesthesia, after sternotomy, during and after CPB and at the
end of surgery. Severe haemodynamic variations were managed by fluids, dobutamine,
norepinephrine, epinephrine,and nitroglycerin. All patients were ventilated postoperatively
till stability was achieved and time to extubation was documented. A standardized
questionnaire was used on the third postoperative day to measure explicit intraoperative
recall. Total cost of the anaesthetic drugs and BIS electrodes used was calculated.
Results: The results of the study showed no significant difference between the 2 groups with
regard to haemodynamics, SVO2, indices of oxygen delivery and consumption, need for
dobutamine or nitroglycerin, levels of patient satisfaction and time to extubation. No sign of
intraoperative memory was seen in either group. The BIS 50 group received significantly
lesser anesthetic drugs , which saved significant money.
Conclusions: Replacement of BIS electrodes with ECG electrodes for the same quality of
monitoring has been
recommended to reduce the cost. The authors in this study conclude, that varying the depth of
anesthesia with the help of BIS in CABG patients did not influence most of the parameters
studied. BIS guided reduction of anaesthetic medication is possible without explicit
intraoperative recall, but the overall cost of BIS monitoring overrides the reduced drug
costs.Authors recommended the use of BIS monitoring for deep hypothermia and total
cardiac arrest during and after cardiac surgery to manage cerebral complications .