An observational study in Postoperative Nausea and Vomiting, Postoperative Pain and Obesity, Morbid, sponsored by Umeå University. Recruiting at 2 sites in Sweden. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-01.
Sponsored by Umeå University · Observational
Around 4,000-5,000 bariatric (weight-loss) operations are performed in Sweden every year. Nausea, vomiting and pain are common immediately after these operations, cause considerable suffering and increase the intensity and length of hospital care. Bariatric surgery is one of the procedures with the highest risk of postoperative nausea and vomiting (PONV): about one third of patients experience PONV already in the recovery unit, and registry data indicate that around 40% report severe pain at the same stage.
This study links two national quality registries - the Swedish Perioperative Register (SPOR) and the Scandinavian Obesity Surgery Registry (SOReg) - to describe how often adult patients experience nausea, vomiting and pain in the post-anaesthesia care unit after primary bariatric surgery, and to identify patient, anaesthetic and surgical factors associated with these outcomes. The study tests whether total intravenous anaesthesia, the addition of a regional nerve block, and preoperative health-related quality of life are associated with PONV and pain, and whether early PONV or pain is associated with complications, unplanned hospital care or reoperation up to one year after surgery. The results are intended to show how well current evidence on preventing PONV and pain is applied in everyday practice and where care can be improved.
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
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.
638 studies on the registry are indexed under Postoperative Nausea and Vomiting; 110 are open to participants now.
This study's planned enrollment of 30,000 is above the median of 208 across 93 observational studies indexed under Postoperative Nausea and Vomiting.
Browse Postoperative Nausea and Vomiting studies →Umeå University is the lead sponsor of 272 studies on the registry; 60 are open to participants now.
Counted across the registry records on this site, refreshed daily.
All adult patients registered in the Scandinavian Obesity Surgery Registry (SOReg) with a primary bariatric procedure during 2018-2027 and a matching operation record in the Swedish Perioperative Register (SPOR).
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Exclusion Criteria:
Patients aged 18 years or older with a primary bariatric procedure registered in the Scandinavian Obesity Surgery Registry (SOReg) 2018-2027 and a matching operation record in the Swedish Perioperative Register (SPOR).
Incidence of postoperative nausea and/or vomiting in the post-anaesthesia care unit
Number of operations with registered nausea and/or vomiting in the PACU divided by the total number of operations. Source: SPOR variable "Illamående postoperativt" (postoperative nausea).
Time frame: During the stay in the post-anaesthesia care unit (approximately 0-4 hours after surgery)
Pain intensity in the post-anaesthesia care unit, numerical rating scale (NRS) 0-10
Median NRS score (0 = no pain, 10 = worst imaginable pain). Source: SPOR variables "Smärta inom 1 tim efter ankomst UVA" (pain within 1 hour of PACU arrival) and "Smärta postoperativt, högsta" (highest postoperative pain).
Time frame: During the stay in the post-anaesthesia care unit (approximately 0-4 hours after surgery)
Incidence of severe pain in the post-anaesthesia care unit
Number of operations with NRS \>= 7 divided by the total number of operations.
Time frame: During the stay in the post-anaesthesia care unit (approximately 0-4 hours after surgery)
Proportion of patients with postoperative complications, unplanned hospital care or reoperation - 6 weeks
Complications (including Clavien-Dindo grade), unplanned hospital care and reoperation as registered in SOReg at the 6-week follow-up.
Time frame: Up to 6 weeks after surgery
Proportion of patients with postoperative complications, unplanned hospital care or reoperation - 1 year
Complications (including Clavien-Dindo grade), unplanned hospital care and reoperation as registered in SOReg at the 1-year follow-up.
Time frame: Up to 1 year after surgery
Plan to share: No
Started Oct 2025 (actual). Primary completion is estimated for Dec 2027, 26 months after the start.
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