ABSTRACT
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). CONCLUSION: 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.
