Closed-loop isoflurane administration with bispectral index in open heart surgery: Randomized controlled trial with manual control

Apparatus for closed-loop isoflurane administration. (A) Fresh gas flow from the machine; (B) inspiratory limb valve; (C) inspiratory limb; (D) expiratory limb; (E) injection point for liquid isoflurane injection into the circuit; (F) expiratory limb value; (G) adjustable pressure relief valve; (H) anesthesia ventilator with ascending bellows; (I) canister; (J) infusion pump with liquid isoflurane, driven by personal computer; (K) monitor that collects vital signs, BIS and end-tidal anesthetic agent concentration; (L) personal computer.

Broad algorithm for isoflurane administration. CV = circuit volume; DOA = duration of anesthesia; FRC = functional residual capacity; HT = height; IAA = inhalational anesthetic uptake; PB = present BIS; PC = present concentration; ROTCA = rapidity of target concentration achievement; TB = target BIS; TC = target concentration; WT = weight.

Bispectral index (BIS) at various time points during the procedure. AXC = aortic cross clamp; CPB = cardiopulmonary bypass; max ETI = maximum BIS within 1 min after endotracheal intubation; max skin = maximum BIS during skin closure; max stern = maximum BIS during sternal closure; min induction = minimum BIS within 3 min of induction.