Post-operative Glycaemic Control Using an Insulin Infusion is Associated with Reduced Surgical Site Infections in Colorectal Surgery

Abstract

Background

The incidence of surgical site infection (SSI) in colorectal surgery (CRS) is higher than other forms of general surgery. Post-operative hyperglycaemia causes increased SSI in CRS. Post-operative hyperglycaemia control in cardiac surgery reduces SSI. The aim was to evaluate using a cohort comparison the effect of post-operative glycaemic control using an insulin infusion on SSI in CRS.

Methods

Collection of data for the ACS-NSQIP was commenced in 2015. The CRS unit added post-operative glycaemic control to the SSI bundle in late 2016. The intervention was an insulin infusion to titrate blood glucose between 135 and 180 mg/Dl (7.5 and 10 mmol/l). The effect of glycaemic control on SSI was assessed comparing ACS-NSQIP raw data prior and after the intervention was commenced.

Results

The NSQIP data from July 2015 to June 2016 revealed the incidence of SSI were 25%. From January 2017 to December 2017, there was a significant reduction in SSI to 6.1% (OR = 517 Cl = 1.92–16.08, p < 0.001). The incidence of organ/space SSI fell significantly from 13% to 1.0% (OR = 11.35, Cl = 1.62–488.7, p < 0.001). There was non-significant reduction in superficial SSI from 11 to 4.0% (OR = 2.93, Cl = 0.68–13.03, p = 0.06). There was no significant difference in other factors associated with SSI in CRS.

Conclusion

Post-operative glycaemic control in CRS reduces the rate of SSI. Post-operative glycaemic control should be included in SSI bundles for CRS and may be of benefit in other surgical specialties.

Appendix

STROBE checklist of items that should be included in reports of observational studies

Criteria	Item No.	Recommendation	Page no.	Comments
Title and abstract	1	(a) Indicate the study’s design with a commonly used term in the title or the abstract	2	Added “Using a cohort comparison”
		(b) Provide in the abstract an informative and balanced summary of what was done and what was found	2	Provided
Introduction
Background/rationale	2	Explain the scientific background and rationale for the investigation being reported	3 & 4	Brief background of the effect of hyperglycaemia causing SSI, the effect of glycaemic control in other surgeries and the use of NSQIP data to examine the hypothesis.
Objectives	3	State-specific objectives, including any prespecified hypotheses	4
Methods
Study design	4	Present key elements of study design early in the paper	5	Clearly stated in the first paragraph
Setting	5	Describe the setting, locations and relevant dates, including periods of recruitment, exposure, follow-up and data collection	5 & 6
Participants	6	(a) Cohort study—Give the eligibility criteria, and the sources and methods of selection of participants. Describe methods of follow-up Case–control study—Give the eligibility criteria, and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls Cross-sectional study—Give the eligibility criteria, and the sources and methods of selection of participants	5, 9 & 10	Provided in the methods and discussed in the discussion section.
		(b) Cohort study—For matched studies, give matching criteria and number of exposed and unexposed Case–control study—For matched studies, give matching criteria and the number of controls per case		This is not a matched study. This has been discussed in the discussion section
Variables	7	Clearly define all outcomes, exposures, predictors, potential confounders and effect modifiers. Give diagnostic criteria, if applicable	7 & 8 Table 3	Confounders discussed in the discussion section
Data sources/measurement	8*	For each variable of interest, give sources of data and details of methods of assessment (measurement). Describe comparability of assessment methods if there is more than one group	5	Used NSQIP data and references provided for the definitions of this data.
Bias	9	Describe any efforts to address potential sources of bias	11 & 12	Bias was discussed in several paragraphs in the discussion section.
Study size	10	Explain how the study size was arrived at	5 & 6. 10	Numbers were dependant on the NSQIP data collected which is explained in the methods and results. Also discussed in the discussion section
Quantitative variables	11	Explain how quantitative variables were handled in the analyses. If applicable, describe which groupings were chosen and why	7 & Table 3	The reasons are explained in the results and discussion section
Statistical methods	12	(a) Describe all statistical methods, including those used to control for confounding	6
		(b) Describe any methods used to examine subgroups and interactions		Not applicable due to small numbers. Discussed in the discussion section.
		(c) Explain how missing data were addressed	7& 11	The only missing data was the ASA classification. This was explained, acknowledged and discussed.
		(d) Cohort study—If applicable, explain how loss to follow-up was addressed Case–control study—If applicable, explain how matching of cases and controls was addressed Cross-sectional study—If applicable, describe analytical methods taking account of sampling strategy		The NSQIP data are a 30-day follow-up and follow-up was complete for all patients.
		(e) Describe any sensitivity analyses	Not relevant
Results
Participants	13*	(a) Report numbers of individuals at each stage of study—e.g., numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed	7
		(b) Give reasons for non-participation at each stage		Non-participation in data collection was explained.
		(c) Consider use of a flow diagram		Considered but would not add to the understanding of the information.
Descriptive data	14*	(a) Give characteristics of study participants (e.g., demographic, clinical, social) and information on exposures and potential confounders	7, Table 3	The only missing data was the ASA classification. This was explained, acknowledged and discussed.
		(b) Indicate number of participants with missing data for each variable of interest	7, Table 3
		(c) Cohort study—Summarise follow-up time (e.g., average and total amount)		Defined as 30 days in the methods and references to NSQIP
Outcome data	15*	Cohort study—Report numbers of outcome events or summary measures over time	7, Tables 2, 3, 4 and 5
		Case–control study—Report numbers in each exposure category, or summary measures of exposure
		Cross-sectional study—Report numbers of outcome events or summary measures
Main results	16	(a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (e.g., 95% confidence interval). Make clear which confounders were adjusted for and why they were included		No unadjusted estimates were sued.
		(b) Report category boundaries when continuous variables were categorised	7, Tables 2 & 3	Reported
		(c) If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period		Not relevant to this study
Other analyses	17	Report other analyses done—e.g., analyses of subgroups and interactions and sensitivity analyses		Subgroup analyses were not possible due to small numbers. This is acknowledged in the discussion section, Pages 10 & 11
Discussion
Key results	18	Summarise key results with reference to study objectives	9
Limitations	19	Discuss limitations of the study, considering sources of potential bias or imprecision. Discuss both direction and magnitude of any potential bias	10, 11 & 12	Potential bias and limitations discussed were Page 10: Type 2 error for wound SSI, obesity as a confounder. Page 11: Stress-induced hyperglycaemia, NSQIP case selection bias and rectal surgery Page 12: Emergency surgery and ASA scores.
Interpretation	20	Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies and other relevant evidence	9 & 14
Generalisability	21	Discuss the generalisability (external validity) of the study results	9 & 14
Other information
Funding	22	Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based		There was no funding provided. This is acknowledged on the title page.