Colombian Surgical Outcomes Study - COLSOS

The general objective of this research is to describe the in-hospital postoperative mortality of patients who have had surgical procedures in Colombian institutions.

We also aim to characterize the sociodemographic and clinical variables of the patients that underwent a surgical procedure in Colombia, determine the secondary postoperative clinical outcomes associated with surgical procedures in Colombia and illustrate the installed surgical capacity and infrastructure of the participating health centres.

The study will be carried out throughout Colombia. The largest number possible of institutions in which surgeries are performed will be included. We expect to have at least 2 or 3 institutions per region. We currently have 65 confirmed participating institutions and have conducted a preliminary interaction with 257 institutions throughout the territory. The list of participating centres and researchers will be continuously updated, and the final version of the list will be attached to the final report.

A sample size estimate of 1353 patients was made to establish the lower limit needed to achieve significance in our primary objective. The estimate was made with the postoperative mortality rate in Colombia obtained in the study by Hanna et al. of 0.74% (13), an alpha value of 0.05, an accuracy of 0.5%, and a design effect of 1.2. Also, due to the nature of the study, it is not possible to randomize. Nevertheless, convenience sampling is considered, as we aim to include all the patients possible.

A descriptive analysis of the data will be performed. The continuous variables will be assessed whit normality tests (Shapiro Wilk or Kolmogorov Smirnov). If the variables have a normal distribution, they will be expressed as mean (measure of central tendency) and as standard deviation (measure of dispersion). Contrariwise, if the variables have a non-normal distribution, they will be expressed as median (measure of central tendency) and as interquartile range (measure of dispersion).

The continuous data with normal distribution will be studied with parametric tests according to the number of comparators: we will use the student t-test or ANOVA if a comparison of more than two groups is required. For continuous data with non-normal distribution, non-parametric tests will be used: if two groups are compared, we will use the Mann Whitney test, and between three groups, the Kruskal Wallis test. The P-value shall be considered statistically significant < 0,05. Categorical variables shall be presented with absolute frequencies and proportions. Categorical data will be compared between two groups using the Chi-square test or fisher's test at convenience to obtain data after collection.

Logistic regression will be carried out multilevel by individual, city or municipality, department, and country. It will evaluate the association between risk factors and primary outcomes and adjust for differences in confounding factors. A multivariate logistic model will be created for specific mortality comparisons that include all potential risk factors associated with in-hospital mortality. The possible risk factors variables with a variance inflation factor more significant than two were excluded to avoid collinearity.

Four strategies are proposed to attract interested researchers and institutions to participate in this study. Because of the support of the Colombian Surgical Association through the official mail of the organization, a generalized invitation will be sent to all clinics and hospitals with surgical processes, throughout the country, with general information of the research study to attract interest from these institutions. Additionally, the journal and website of the Colombian Surgical Association in both the journal and on the website of the society of general surgery the registration will be published so students, interns, doctors, residents, and specialists interested in participating. Finally, voice-to-voice communication and mass dissemination through ColombianSurg Collaborative social networks (Instagram, Twitter, Facebook, and Official Website) cannot be ruled out.

Coordination with institutions and departments: A hierarchical management organization was set up to generate specific and personalized attention to each region and institution (Figure 3). In addition, researchers will be able to communicate with the ColombianSurg Collaborative team and vice versa through different platforms that will be put at their services, such as instant messaging groups, email, and official Websites.