In the early stage of the research, this research was limited by the application permission of research drugs and instruments, and the research will have to be interrupted, which is extremely regrettable.

This study was designed to compare propofol intravenous anesthesia to sevoflurane inhalation anesthesia on the quality of recovery after surgery for anal fistula in obese patients. Propofol-based total intravenous anesthesia (TIVA) and sevoflurane inhalation anesthesia are the two main anesthesia techniques. Obesity influences not only anesthetics metabolic but also physical function of patients, so it is meaningful to study which anesthesia technique is better for the recovery of obese patients after surgery.

This study was approved by Ethical Committee of ShuGuang Hospital affiliated to Shanghai University of Traditional Chinese Medicine. Patients were given informed consent before enrolling the study, whereafter, they were randomized into two groups, propofol-based total intravenous anesthesia (Group PRO) and sevoflurane inhalation anesthesia (Group SEVO). After entering the routine, blood pressure, pulse oxygen saturation, and ECG were monitored by multifunctional anesthesia monitor and anesthesia depth was monitored by brain electrical bispectral index (BIS). Intravenous access (20-gauge catheter) was established and an infusion of lactated Ringer's solution began in the operating room. Patients were positioned as left or right lateral decubitus position according to surgery. Patients inhaled oxygen before anesthetic induction using a face mask. Intravenous penehyclidine hydrochloride 0.5mg, granisetron 3mg, and midazolam 2mg were given as premedication.

In Group PRO, anesthesia was induced by sufentanil citrate 0.2ug/kg and propofol in TCI effect compartment concentration 4-6ug/kg, until the patient loses consciousness, then laryngeal mask airway was inserted. Anesthesia was then maintained with propofol in TCI 3-4ug/kg, if the patient showed body movement, TCI was raised by 0.5 ug/kg every time, until the anesthesia depth was satisfied (no body movement, BIS40-60).

In Group SEVO, anesthesia was induced by sufentanil citrate 0.2ug/kg and sevoflurane. Firstly, mask was fixed with four head band, keeping it sealed. The method of vital capacity was used, taking deep breaths until the patient loses consciousness (call patients not to answer, the eyelash reflex disappeared, BIS40-60): close valve of APL to zero, empty the breathing bag, block the respiratory circuit, prime the circuit with 8% sevoflurane in O2 at 8 L/min until the inspired-limb drug concentration measured upon 6%. Then, laryngeal mask airway was inserted. Anesthesia was then maintained with sevoflurane, adjusting the oxygen flow rate to 2L/min and sevoflurane vaporizer concentration 1.5-2%, if the patient showed body movement and other narcotic lighter sign, sevoflurane vaporizer concentration was raised by 0.5% every time, until the anesthesia depth was satisfied (no body movement, BIS40-60).

The propofol and sevoflurane were closed at the end of surgery.

Quality of recovery was assessed using QoR-40 scale in day 1 and day 2 after surgery. Postoperative pain intensity was assessed using visual analogue scale in day 1 and day 2 after surgery. Surgical and waking time was recorded before leaving post-anesthesia care unit. Adverse events (circulation or respiratory depression, postoperative nausea and vomiting, recovery agitation) were recorded perioperatively.

Inclusion Criteria:

1. Patients undergoing selective surgery for anal fistula,
2. aged 18-60 years,
3. body mass index >30kg/m2,
4. patient who required general anesthesia and signed informed consent,
5. ASA I - II.

Exclusion Criteria:

1. patients refused to participate in the test,
2. patients with severe cardiac, pulmonary, liver and renal dysfunction,
3. patients with severe central nervous system diseases or severe mental diseases,
4. patients with a history of alcoholism,
5. allergy to related anesthetics,
6. pregnant or lactating women,
7. participated in the other trials in the past month,
8. taking any sedative, opioid, or sleep aid drugs,
9. patients with other special conditions not suitable for this study, ____________________________________________.