Procedure
nausea and vomiting, normocapnia, postoperative pain, tetanic
MUSCLE RELAXATION
On arrival at the operating room, an intravenous cannula was inserted in the forearm vein of the patient, and standard anesthesia monitoring (noninvasive blood pressure, electrocardiogram, and oxygen saturation) were established and anesthesia depth was monitored using Bispectral Index (BIS, Medtronic, Minneapolis, MN, USA). Anesthesia was induced with sufentanil (0.5 µg/kg) and etomidate (0.2–0.3 mg/kg), cisatracurium (0.15–0.2 mg/kg). Anaesthesia was maintained by a continuous inhalation of 1% sevoflurane and infusion of propofol (3–4 mg/kg/h) and remifentanil (0.5-1.0 µg/kg/min); the infusion speed was adjusted to maintain the BIS between 40 and 60. Cisatracurium was added as required to facilitate the completion of the surgery. After tracheal intubation, ventilation was controlled to maintain arterial oxygen saturation at 96% or higher and normocapnia. Body temperature was maintained at 36.0 °C or higher. Sevoflurane was stopped about 1 h before the end of the surgery and the flow of fresh gas was increased to ensure no residual of inhalational anesthetics at the end of the surgery. Ondansetron 4 mg was administered intravenously 0.5 h before the end of the surgery to prevent nausea and vomiting. An additional 10–15 µg of sufentanil was administered at the end of surgery for postoperative pain management.Neuromuscular function was evaluated by TOF-Watch SX acceleration muscle relaxation monitor (Organon, Dublin, Ireland). After the skin had been cleaned carefully, two surface skin electrodes were attached over the ulnar nerve proximal to the wrist at a distance of 3–6 cm. After immobilising the forearm, the acceleration transducer was fixed firmly to the volar side of the distal phalanx of the thumb on a small elastic hand adapter (TOF-Watch Handadapter; Schering-Plough, Swords, Ireland). The monitoring was initiated after induction, but before cisatracurium administration. The device was calibrated automatically after a 50-Hz tetanic stimulation for 5 s and a stable baseline (< 5% change in TOF ratio) was recorded. Normalized TOF values were calculated and recorded according to baseline TOF values. TOF stimulus was applied every 60 s until a TOF ratio greater than or equal to 0.9. When a TOF ratio of 0.2 was reached two times consecutively, a pre-determined dose of neostigmine provided by Sine Jinzhu Pharmaceutical company (Shanghai, China) was administered according to the patient group (NS, 20 µg/kg, 40 µg/kg or 50 µg/kg), accompanied by glycopyrrolate in an 1:5 ratio. The time from the administration of neostigmine to a TOF ratio of 0.9 was recorded. The proportion of patients with TOF value ≥ 0.9 10 min after neostigmine administration; the incidence of nausea and vomiting in patients on postoperative day 1-day 3; the proportion of patients with Mini-Mental State Examination (MMSE) score decrease ≥ 3 points on postoperative day 3; and PACU stay time after neostigmine administration were followed up.