Postoperative complications after abdominal surgery can lead to prolonged recovery, intensive care admission, and death. The P-POSSUM score is a commonly used surgical risk prediction tool, but its performance may vary between hospitals and patient populations. Frailty, especially in older patients, may also affect postoperative outcomes and may improve risk prediction when added to existing scoring systems.

This ambispective observational cohort study evaluates the prognostic value of the P-POSSUM score, with additional assessment of frailty and routine perioperative clinical data, for predicting postoperative complications and treatment outcomes in adult patients undergoing abdominal surgery at Bach Mai Hospital. The study includes retrospective data from January 2025 and prospective data collection through May 2026. No intervention is assigned by the investigators. All patients receive routine perioperative care according to clinical practice.

The study will assess the predictive performance of P-POSSUM for postoperative complications and mortality, and will explore whether adding frailty-related variables improves risk prediction.

Postoperative complications remain an important cause of morbidity, prolonged hospital stay, intensive care use, and mortality after abdominal surgery. Risk prediction before and after surgery may help clinicians identify high-risk patients, guide perioperative planning, and improve postoperative monitoring. The Portsmouth Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity, known as P-POSSUM, combines physiological and operative variables to estimate the risk of postoperative morbidity and mortality. However, the performance of P-POSSUM may differ across populations, surgical settings, and healthcare systems.

Frailty is increasingly recognized as an important predictor of adverse postoperative outcomes, particularly in older surgical patients. Frailty reflects reduced physiological reserve and increased vulnerability to acute stressors such as emergency surgery, infection, bleeding, and postoperative critical illness. In this study, frailty will be assessed using routinely available clinical information. For retrospective data, frailty-related status will be evaluated using available medical records and a modified frailty index when sufficient data are available. For prospectively enrolled patients, frailty will be assessed based on baseline functional status before the acute surgical illness, using a standardized clinical frailty assessment when feasible.

This study is designed as an ambispective observational cohort study conducted at the Center for Anesthesia and Surgical Intensive Care, Bach Mai Hospital, Vietnam. The study includes retrospective data from patients undergoing abdominal surgery from January 2025 and prospective data collection through May 2026. Eligible adult patients undergoing abdominal surgery will be included according to predefined selection criteria. The investigators will not assign any intervention or modify treatment decisions. Perioperative management, surgical care, anesthesia, postoperative monitoring, and intensive care treatment will be provided according to routine clinical practice.

For each eligible patient, demographic characteristics, comorbidities, physiological variables, operative severity variables, frailty-related variables, perioperative laboratory results, anesthesia and surgical information, postoperative complications, and treatment outcomes will be collected. The P-POSSUM score will be calculated using the predefined physiological and operative scoring components. Study outcomes will be obtained from hospital medical records, anesthesia records, surgical records, intensive care charts, laboratory data, and discharge documentation.

The primary objective is to evaluate the prognostic performance of P-POSSUM for postoperative complications after abdominal surgery. Secondary objectives include evaluating the performance of P-POSSUM for postoperative mortality and other treatment outcomes, assessing calibration and discrimination of the score, and exploring whether the addition of frailty-related variables and routinely available perioperative data improves risk prediction compared with P-POSSUM alone.

Inclusion Criteria:

Patients aged 60 years or older. Patients undergoing abdominal surgery at Bach Mai Hospital. Patients managed perioperatively or postoperatively by the Center for Anesthesia and Surgical Intensive Care.

Patients with available perioperative clinical data required to calculate the P-POSSUM score.

Patients with available baseline clinical, comorbidity, or functional status information for frailty assessment.

Patients with available postoperative outcome data for assessment of complications, mortality, or treatment outcomes.

Exclusion Criteria:

Patients younger than 60 years. Patients not undergoing abdominal surgery. Patients undergoing minor procedures without operative severity data required for P-POSSUM calculation.

Patients with missing key physiological or operative variables required to calculate the P-POSSUM score.

Patients with insufficient baseline information for frailty assessment. Patients with insufficient postoperative follow-up data for outcome assessment.

Older adult patients aged 60 years or older undergoing abdominal surgery at Bach Mai Hospital. The study population includes patients identified from retrospective hospital records from January 2025 and prospectively collected data through May 2026. P-POSSUM variables, frailty-related variables, routine perioperative clinical data, postoperative complications, and treatment outcomes will be collected for prognostic evaluation.

De-identified individual participant data underlying the main published results may be shared upon reasonable request. Shared data may include baseline demographic and clinical characteristics, P-POSSUM physiological and operative variables, frailty-related variables, routine perioperative data, postoperative complications, mortality, length of stay, and other treatment outcomes used in the final analysis. No directly identifiable participant information will be shared.

De-identified individual participant data and supporting documents will be available after publication of the main study results. There is no predetermined end date for data availability; requests will be considered according to institutional policies, ethics requirements, and data sharing agreements.

Data may be shared with qualified researchers for systematic reviews, meta-analyses, external validation, or scientifically valid secondary analyses. Access will require submission of a research proposal, approval by an ethics committee when applicable, and a signed data sharing agreement with the study custodian or sponsor. Requests should be sent to the study contact. Shared data will be de-identified and limited to variables necessary for the approved analysis.