Postoperative Nausea, Vomiting and Pain After Bariatric Surgery - a National Registry Study

BACKGROUND Bariatric surgery is common in Sweden with 4,000-5,000 procedures per year. Data on each operation are recorded in the Swedish Perioperative Register (SPOR), covering more than 90% of all surgical procedures in Sweden with automatic data transfer from hospital IT systems, and in the Scandinavian Obesity Surgery Registry (SOReg), with a coverage of approximately 98% of bariatric surgery. Postoperative nausea and vomiting (PONV) and pain are frequent after bariatric surgery. Evidence-based guidelines exist, but 25-40% of surgical patients still experience PONV, and up to 50% may experience severe postoperative pain. Risk factors are validated at a general level but not specifically for bariatric surgery.

OBJECTIVES

• To describe the risk of early PONV and pain in the post-anaesthesia care unit (PACU) after primary bariatric surgery.
• To identify factors associated with early PONV and pain.
• To test the hypotheses that total intravenous anaesthesia (compared with inhalational anaesthesia) and the addition of a regional block are associated with lower risk of PONV or pain in the PACU; that poorer preoperative health-related quality of life (RAND-36) is associated with higher risk of PONV, pain and severe pain; and that PONV or pain in the PACU is associated with higher risk of postoperative complications up to one year after surgery. Separate hypothesis tests are performed for PONV and pain.

DESIGN Exploratory observational cohort study based on registry data. Patients aged 18 years or older with a primary bariatric procedure registered in SOReg during 2018-2027 are identified. Records are linked to SPOR by Uppsala Clinical Research Center (UCR) using personal identity number and date of surgery (+/- 3 days). If several SPOR records fall within the interval, each is included as a separate row with an index variable linking to the SOReg operation. Each individual is assigned a unique serial number and the dataset delivered to the research group contains pseudonymised data only. Data extractions are made at most once per year from 2025; the first analyses cover 2018-2023.

VARIABLES From SOReg: preoperative data (patient characteristics, comorbidity, laboratory values, preoperative work-up, RAND-36), operative data (procedure type, technique, intraoperative complications) and postoperative follow-up up to one year (complications, hospital care, reoperation). From SPOR: patient characteristics, process data, operative data (diagnosis, procedure, anaesthesia type, times, deviations), postoperative data (pain, nausea/vomiting, deviations, level of care) and date of death.

STATISTICAL ANALYSIS Descriptive statistics with univariable and multivariable analysis of associations. Candidate variables include sex, age, comorbidity, preoperative pain, anaesthesia type, procedure type, surgical technique and length of stay. The expected sample is approximately 70% of all bariatric operations in Sweden, about 3,000 patients per year; the main reason for exclusion is expected to be missing PACU registration of pain and/or nausea at some hospitals. As the study includes more than half of the target population, no formal power calculation is performed.

DATA PROTECTION Only pseudonymised data are handled. Data are stored at Umeå University with access restricted to the study researchers, in accordance with current legislation.

Inclusion criteria

• Age 18 years or older
• Primary bariatric surgery registered in SOReg during 2018-2027

Exclusion criteria

• Revision bariatric surgery
• If more than one bariatric operation is registered for the same patient, only the primary operation is included