Closed-loop isoflurane administration with bispectral index in open heart surgery: randomized controlled trial with manual control.
OBJECTIVE
Improved anesthetic agent delivery system (IAADS), a modification of closed-loop anesthesia delivery system (CLADS), is designed to deliver inhalational anesthetics and propofol through closed-loop control with bispectral index (BIS) as target. We compared the performance of IAADS with the manual control isoflurane administration during cardiac surgery.


METHODS
Forty patients of ASA (American Society of Anesthesiologists) physical status class II-III, undergoing elective cardiac surgery with cardiopulmonary bypass (CPB) in a tertiary care hospital in India were randomized to receive isoflurane through a closed-loop system (IAADS group) or through a Tech 7 vaporizer adjusted manually (manual group) to achieve a target BIS of 50. Patients were induced with a propofol infusion and isoflurane was started after intubation. During CPB, patients received propofol; isoflurane was restarted after separation from CPB. The efficacy of IAADS in controlling depth of anesthesia and hemodynamic variations was compared with that of manual control.


RESULTS
IAADS was able to maintain BIS within ± 10 of target for significantly longer period (84.6 ± 7.2% in IAADS group vs. 75.9 ± 11.2 in manual group, p < 0.01). Both overall performance, as assessed by global score (p < 0.01), and precision, as judged by median absolute performance error (MDAPE) (p < 0.04), were significantly better in the IAADS group. The IAADS group required significantly less propofol for induction (1.3 ± 0.4 mg/kg in IAADS vs. 1.6 ± 0.5 mg/kg in manual, p < 0.05) and less isoflurane during maintenance of anesthesia (3.3 ± 0.8 ml/h vs. 3.4 ± 0.9 ml/h, p < 0.01).


CONCLUSIONS
The present study proves the feasibility and efficacy of inhalation anesthetic administration through closed-loop control. This is the first system that has been developed to control intravenous and inhalational anesthetic agents in a closed-loop model using BIS.
Department of Anesthesia and Intensive Care, Postgraduate Institute of Medical Education and Research, Chandigarh, India. sethu_madhav@sify.com
J Sethu
JS
Madhavan
G D
GD
Puri
Preethy J
PJ
Mathew
D000328:Adult; D000368:Aged; D000764:Anesthesia, Closed-Circuit; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D006348:Cardiac Surgical Procedures; D003362:Cost-Benefit Analysis; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged
D018685:Anesthetics, Inhalation; D007530:Isoflurane