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Fearon et al. Metab Target Organ Damage 2022;2:13 https://dx.doi.org/10.20517/mtod.2022.12 Page 7 of 13

which may occur in hyperglycaemia, leading to increased insulin resistance and an overall worse
cardiometabolic status due to hepatic inflammation and endoplasmic reticulum stress. Both mechanisms
are important in the interplay of NAFLD and DM and the differences in the management approaches. The
third mechanism is adipose tissue dysfunction leading to increased free fatty acids and dysfunction in
adipokine and cytokine release leading to increased hepatic inflammation . Both the metabolic and
[26]
anthropometrical improvements associated with a VLED are beneficial for any subsequent intra-abdominal
operation, particularly where liver retraction is undertaken.

Griffin et al. provide observational and qualitative data on their dietitian-led VLED model of care for non-
bariatric elective surgery, most of which was gynaecological surgery. There was high acceptance and
satisfaction from participants and surgeons. There was a mean of 7.3% weight loss (P < 0.001), and although
HbA1c levels trended down, it was not significant. Interestingly nearly 20% of participants were excluded
due to non-engagement in the program. The reasons were not specified; however, this is likely to be a
typical finding in any VLED program and leads to consideration of inpatient programs that may be more
attractive or more accessible for those who find it challenging to engage . Ruggenenti et al. randomised
[27]
people with overweight/obesity and T2DM to either a 25% calorie restriction (CR) or standard diet. There
was a significant improvement in the glomerular filtration rate at six months compared to a regular diet.
The CR group also demonstrated improved HbA1c, blood glucose, and insulin sensitivity (measured by
[28]
glucose disposal rate) .
Despite several studies showing the feasibility and benefit of a VLED, it is not commonly used
preoperatively. This is likely due to a lack of awareness from the surgical teams and under-resourcing of the
dietetic and endocrinology teams, who promote and support the intervention. However, with education and
clear instructions, most people can carry out a VLED for a very short period. A collaborative,
interdisciplinary approach for those undergoing surgery may allow identification of T2DM and, if present,
facilitate access to resources to manage the disease with a focus on preoperatively and longer-term
integrated care.

Pharmacotherapy
Currently, pharmacotherapy is the mainstay in the management of T2DM. An overview of available
pharmacotherapy is provided in Figure 1. Variation in preoperative management is still evident; however,
several recent high-quality studies contribute to the evidence base for instigating certain oral
hypoglycaemics preoperatively. A feasibility randomised controlled trial (RCT) from the OCTOPuS study
group included people with DM and an HbA1c > 53 mml/mol (or ≥ 64 mmol/mol in those more than 75
years old) who were due to undergo coronary artery bypass grafting (CABG). Several preoperative
interventions were implemented, including pharmacotherapy. The emphasis was on initiating a sodium-
glucose cotransporter-2 (SGLT-2) inhibitor or a glucagon-like peptide 1 (GLP1) receptor agonist, which has
cardiovascular benefits. The median HbA1c was 10 mmol lower than that before the intervention .
[29]
Insulin remains the primary treatment for T1DM, and either as monotherapy or part of combination
therapy for T2DM, oral or injectable non-insulin therapies have been unable to achieve glycemic control.
The CPOC guidelines outline the dosage adjustments for each type and formulation of insulin in the
preoperative period .
[14]

Obesity is a risk factor for T2DM, and there is an overlap in pharmacotherapy to optimise both diseases
preoperatively. In particular, GLP1 receptor agonists and SGLT-2 inhibitors have good efficacy, proven
cardiovascular benefits, and an acceptable safety profile . Houlden et al. showed that preoperative
[30]