Background: The Royal College of Anesthesiologists of Thailand (RCAT) contributed to a multicenter study, the Perioperative and Anesthetic Adverse Events in Thailand study (PAAd Thai) in 22 hospitals across Thailand. In the past two decades, the number of obese patients increased at an alarming rate.

Objective: To investigate natural history of anesthesia or surgical related complications, contributing factor and corrective strategies in patients whose body mass index (BMI) was equal or higher than 35 kg/m².

Materials and Methods: The present study was prospective descriptive study. After being approved by each Institutional Ethical Committee, written informed consents were waived. Each hospital was asked to anonymously report incidence of anesthesia related adverse events. Two thousand two hundred six incidence reports were provided. Patient with a BMI equal or over 35 kg/m² that underwent surgery were selected from the incident reports. Data were discussed and analyzed by three senior anesthesiologists for contributing factors, clinical courses, factors minimizing incident, and suggested corrective strategies.

Results: Fifty-eight cases (2.63%) from the 2,206 reports of the PAAd Thai Study met the inclusion definition and were reviewed. Seventy-eight incidents occurred from 3,028 critical incidents reports (2.57%), one-third was male and the rest were female. The average age was 39.96±6.72 year and BMI was 39.8±5.1 kg/m². The highest incidence occurred in patients with BMI 35 to 39.9 kg/m² (65.52%). Half was classified as the ASA physical status 3. The adverse events were found more frequent in elective surgery (40 incidents or 68.96%) than emergency surgery. General surgery such as laparotomy had higher incidence compared to other surgical specialties. Oxygen desaturation was the most common incident (51.7%). Severe arrhythmia, difficult intubation, and cardiac arrest in 24 hours post-operatively were found in the same frequency (12.1%). Contributing factors from the present report were inadequate preanesthetic evaluation and preparation, inexperience, inappropriate decision, and urgency. Having experiences, more vigilance, and experienced assistant or effective supervision were factors for minimizing outcomes.

Conclusion: Improvement of supervision, additional training, and clinical practice guidelines were suggested for corrective strategies.

Keywords: Obesity, Overweighted, Desaturation, Arrhythmia, Difficult intubation, Reintubation, Cardiac arrest