Incidence of venous thromboembolism following colorectal surgery

Lewis-Lloyd, Christopher A. (2023) Incidence of venous thromboembolism following colorectal surgery. PhD thesis, University of Nottingham.

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Colectomy is the second most common major abdominal operation globally with colorectal cancer (CRC) being the most common indication. Venous thromboembolism (VTE), comprising deep vein thrombosis and pulmonary embolism, is a potentially fatal yet preventable postoperative complication of which colectomy has one of the highest risks of any abdominal operation. However, perioperative care over the last two decades has changed with an increase in minimally invasive surgery and focus on VTE prevention. This has led to the introduction of international guidance advocating pharmacological VTE prophylaxis for a minimum of inpatient stay or 7-days following benign colectomy that extends to 4-weeks for those with CRC. Therefore, the aim of this thesis was to quantify changes in incidence rates of VTE following colectomy in relation to international changes in perioperative care and so help guide future improvements in VTE prevention.

The first study in this thesis (Chapter 2) is a systematic review and meta-analysis on the incidence and variation of VTE following CRC resection. Following guidelines on meta-analysis reporting, Medline and Embase databases were searched from database inception to August 2019 including 3 other registered medical databases. Only patients aged ≥ 18 years-olds post CRC resection were included and selected studies comprised randomised controlled trials and population-based database/registry cohorts. Of 6,441 studies 18 were available for meta-analysis reporting on 539,390 patients. Pooled 30- and 90-day incidence rates of VTE following resection were 195 (95% CI 148–256, I2 99.1%) and 91 (95% CI 56–146, I2 99.2%) per 1,000 person-years respectively. When separated by United Nations Geoscheme Areas differences in the incidence of postoperative VTE were observed with 30- and 90-days pooled rates per 1,000 person-years of 284 (95% CI 238–339) and 121 (95% CI 82–179) in the Americas and 71 (95% CI 60–84) and 57 (95% CI 47–69) in Europe.

Chapters 3 and 4 are national cohort studies of colectomy patients between 2000 and 2019 using using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data.

Chapter 3 examines the changes in VTE rates over time from 2000 to 2019 following colorectal resection by admission type, surgical indication and operative technique. Reporting absolute incidence rates (IR) and adjusted incidence rate ratios (aIRR) using Poisson regression for the per year change in VTE risk within 30-days following colectomy. Of 183,791 colectomy patients, 1,337 (0.73%) developed 30-day postoperative VTE. Overall, VTE rates reduced over the 20-year study period following elective (relative risk reduction 31.25%, 95% CI 5.69%–49.88%) but not emergency surgery. Similarly, yearly changes in VTE risk reduced following minimally invasive resections (elective benign: aIRR 0.93, 95% CI 0.90–0.97, elective malignant: aIRR 0.94, 95%CI 0.91–0.98 and emergency benign: aIRR 0.96, 95% CI 0.92–1.00), but not following open resections. There was a per year VTE risk increase following open emergency malignant resections (aIRR 1.02, 95% CI 1.00–1.04).

Chapter 4 examines in detail the duration and magnitude of post-discharge VTE during the period 2010 to 2019. Stratified by admission type and surgical indication, IRs per 1,000 person-years and aIRRs for post-discharge VTE were calculated for the first 4-weeks following resection and post-discharge VTE IRs for each postoperative week to 12-weeks post-op. Of 104,744 patients, 663 (0.63%) developed post-discharge VTE within 12-weeks after colectomy. Post-discharge VTE IRs for the first 4-weeks post-operation were low following elective resections (benign (20.66, 95% CI 13.73–31.08) and malignant (28.95, 95% CI 23.09–36.31)) and higher following emergency resections (benign (47.31, 95% CI 34.43–65.02) and malignant (107.18, 95% CI 78.62–146.12)). Compared to elective malignant resections, there was no difference in post-discharge VTE risk within the first 4-weeks following elective benign colectomy (aIRR 0.92, 95% CI 0.56–1.50). However, post-discharge VTE risks within 4-weeks following emergency resections were significantly greater for benign (aIRR 1.89, 95% CI 1.22–2.93) and malignant (aIRR 3.13, 95% CI 2.06–4.76) indications compared to elective malignant colectomy.

The final study (Chapter 5) in this thesis comprises two service evaluations examining the compliance of extended or 7-day postoperative VTE prophylaxis prescription on discharge following CRC resection, pre and post an educational intervention for junior doctors, and abdominal surgery respectively at a tertiary care centre within England. Following CRC resection, of 80 pre- and 41 post-intervention patients eligible for inclusion there was an 11.43% absolute increase in VTE prophylaxis prescription compliance from 81.25% to 92.68% yet this was not significant (P = 0.0944). Overall, VTE risk assessment did not have a significant impact on extended VTE prophylaxis prescription at discharge. However, patients were significantly less likely to receive extended VTE prophylaxis prescription on discharge if extended VTE prophylaxis instruction was not accurately recorded in the postoperative note (Risk difference -26.75%, 95% CI -44.03%–-9.48%, P = 0.0269). Of 97 eligible benign abdominal surgery patients for 7-days postoperative VTE prophylaxis, none were prescribed appropriate continuing VTE prophylaxis at discharge or specifically had 7-days postoperative VTE prophylaxis recorded in the postoperative plan.

This thesis provides new evidence regarding the incidence of VTE following colectomy and how this has changed with advancements in perioperative care within Colorectal surgery over the last 20 years. It highlights the incidence of VTE following CRC resection is high and remains so more than 1-month after surgery with clear disparities between global regions. It demonstrates VTE risk has reduced following minimally invasive surgery in the elective setting, but this reduction is not temporally related to international guidance with further efforts needed to implement advances in surgical care within emergency and/or open surgery to reduce VTE risk. In terms of post-discharge VTE, it shows rates are low in line with current VTE guidance following elective colectomies. However, emergency benign resections that currently do not receive extended VTE prophylaxis have an approximately 2-fold greater post-discharge VTE compared to elective malignant resections, suggesting emergency benign colectomy patients, particularly those undergoing inflammatory bowel disease resection, may benefit from extended VTE prophylaxis. Emergency malignant colectomies have the greatest risk of post-discharge VTE despite receiving extended VTE prophylaxis, indicating further perioperative measures are needed to reduce the post-discharge VTE risk in this group. It shows that current compliance with extended VTE prophylaxis prescription at discharge for CRC resectional patients is high yet requires further improvements to reach national targets. Although this is not the case for the minimum 7-days postoperative VTE prophylaxis following benign abdominal operations. This suggests further educational initiatives and performance markers, such as the measurement of detailed documentation of VTE prophylaxis duration within postoperative records, are needed to improve appropriate post-discharge VTE prophylaxis prescription following malignant and benign operations.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Humes, David J.
Crooks, Colin J.
Keywords: Colorectal Surgery, Venous Thromboembolism, Epidemiology
Subjects: W Medicine and related subjects (NLM Classification) > WG Cardiocascular system
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Medicine
Item ID: 72293
Depositing User: Lewis-Lloyd, Christopher
Date Deposited: 31 Jul 2023 04:40
Last Modified: 31 Jul 2023 04:40

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