FRCA Notes

Diabetes Mellitus

Resources

  • Diabetes mellitus is a group of multisystem disorders characterised by hyperglycaemia, due to abnormalities of insulin secretion, insulin resistance or both
    • 7% of the UK population and 10.5% of the global population has diabetes
    • 10 - 30% of the inpatient population has diabetes
    • Patients with diabetes account for 17% of all operative procedures, and diabetics are more likely to undergo surgery than non-diabetics
    • Diabetics is the second most common perioperative comorbidity
    • Diabetes is associated with an increased perioperative mortality

  • The predominant anaesthetic concerns are with:
    • The effects of long-term complications of diabetes
    • The peri-operative management of diabetic medications including insulin
    • The peri-operative control of blood glucose

Types 1 & 2

  • Type 1 - absolute insulin deficiency due to autoimmune pancreatic destruction, typically diagnosed at a young age and requires insulin therapy

  • Type 2 - insulin resistance and relative deficiency, with both genetic and environmental components that often coalesces with metabolic syndrome

Type 3, 4 and others

  • Type 3 diabetes
    • 3a - Monogenetic defects of β-cell function or insulin action e.g. MODY, neonatal diabetes

    • 3b - Disease of the exocrine pancreas
      • As part of other inherited disease states e.g. cystic fibrosis, haemochromatosis
      • Following trauma, pancreatitis, infection, malignancy
      • Post-pancreatectomy

    • 3c - Endocrinopathies

    • 3d - Drug-induced diabetes
      • Thiazide diuretics
      • Glucocorticoids
      • β-blockers
      • Post-organ transplant

  • Type 4 - Gestational diabetes i.e. glucose intolerance during pregnancy

  • Late-onset autoimmune diabetes in adults (LADA)

  • Based on measurement of elevated plasma glucose, including HbA1c
  • May be accompanied by symptoms of hyperglycaemia: polydipsia, polyuria, fatigue, weight loss
  1. Clinical symptoms of hyperglycaemia + random plasma glucose >11.1mmol/L, or
  2. Fasting (8hrs) plasma glucose >7.8mmol/L, or
  3. Oral glucose tolerance test; 2hrs post-75g glucose load plasma glucose of >11.1mmol/
  4. HbA1c >48mmol/mol

Pre-diabetes

  • Some patients may be in 'pre-diabetic' states e.g.:
    • Impaired fasting glucose - fasting plasma glucose of 5.6 - 6.9mmol/L
    • Impaired glucose tolerance - 2hr post-75g glucose load plasma glucose of 7.8 - 11.1mmol/L

  • Patients are at risk of developing diabetes, HTN and CV complications
  • They should receive lifestyle and dietary advice to reduce progression to diabetes, as well as ongoing monitoring

  • These complications may be seen in surgical patients with dysglycaemia who aren't necessarily diabetic, and are seen across a range of surgical specialties (BJA, 2022)
Complications of perioperative dysglycaemia
↑ surgical site infection (2x)
Nosocomial systemic infection e.g. UTI (3x) or LRTI (2.5x)
AKI (2x)
Acute coronary syndromes (2x)
Acute cerebrovascular events
Pressure injuries and delayed wound healing
↑ length of stay (hyper- or hypo-glycaemia)
Higher mortality (hyper- or hypo-glycaemia)


Acute

  • Hyperglycaemia
  • DKA
  • HHS
  • Hypoglycaemia, typically iatrogenic from excess insulin administration

Chronic - macrovascular

Chronic - microvascular

  • Nephropathy
    • Microalbuminuria
    • Glomerulosclerosis
    • Chronic kidney disease

  • Neuropathy (peripheral or autonomic)
  • Retinopathy
  • Stiff joint syndrome
    • Results from glycosylation of collagen at the TMJ and atlanto-occipital joint
    • Higher incidence of difficult intubation

  • General increased risk of infection

Autonomic dysfunction

  • Occurs in both Type 1 (40%) and Type 2 (20%) diabetes
  • Features include:
    • Postural hypotension
    • No variation in heart rate during respiratory cycle
    • No blood pressure overshoot in phase 4 of the Valsalva manoeuvre
    • GORD due to impaired LOS tone
    • Delayed gastric emptying (early satiety, nausea, vomiting)
    • Sexual dysfunction e.g. erectile dysfunction, retrograde ejaculation
    • Incomplete bladder emptying

Perioperative management of the diabetic patient


History and examination

  • History of diabetes including control and HbA1c
  • If HbA1c >69mmol/mol consider delaying elective surgery until optimised
  • Frequency of acute complications
  • Presence and degree of chronic/systemic complications
  • Usual management - themselves, nurse, GP, endocrinologist
  • Drug history

  • Check for presence of common coalescing comorbidities such as cardiovascular disease

Investigations

  • Non-invasive and postural blood pressure
  • BMI
  • Resting ECG
  • Consider TTE if concerns over cardiovascular dysfunction

  • Bloods
    • FBC
    • Capillary blood sugar and ketones
    • HbA1c (within last three months)
    • U&E to check for nephropathy
    • ± liver function and clotting

    • Measure CBG on arrival to pre-assessment area
    • Measure CBG prior to induction of anaesthesia

  • Early involvement of diabetes team if concerns/complexity

Drug management - oral agents

  • Omit SGLT2 inhibitors on day before surgery (although of note ESC guidelines say omit for 72hrs)
  • More recent guidance on GLP-1 receptor agonists suggests witholding these drugs if they are used for weight management
  • First on list to minimise duration fasted (ideally <12hrs) and therefore reduce risk of hypoglycaemic
Drug class Morning surgery Afternoon surgery
Acarbose Omit if not eating Give AM dose if eating
Meglitinides Omit if not eating Give AM dose if eating
Metformin OD or BD dosing: take as normal
TDS dosing: omit lunchtime dose		 OD or BD dosing: take as normal
TDS dosing: omit lunchtime dose
Sulphonylureas Omit morning dose
If BD dosing: take PM dose if eating		 Omit on day of surgery
Pioglitazone Take as normal Take as normal
DPP4 inhibitors Take as normal Take as normal
GLP-1 receptor agonists Take as normal Take as normal
SGLT-2 inhibitors Omit Omit

Drug management - insulins

Insulin regimen Morning surgery Afternoon surgery
Once daily long acting (ON)
(E.g. Glargine, Levemir, Insulatard, Humulin I)		 Give as normal and check blood glucose Give as normal and check blood glucose
Once daily long acting (OM)
(E.g. Glargine, Levemir, Insulatard, Humulin I)		 Reduce by 20% Reduce by 20%
Twice daily pre-mixed
(e.g. Novomix 30, Humulin M3, Humalog 25/50)		 Give half usual morning dose
Give normal evening dose		 Give half usual morning dose
Give normal evening dose
Twice daily separate short- and intermediate-acting insluins Calculate total dose of both morning insulins
Give half of the total dose as an intermediate-acting insulin		 Calculate total dose of both morning insulins
Give half of the total dose as an intermediate-acting insulin
Multiple injections (e.g. TDS) Morning dose either omitted (short-acting insulin) or halved (pre-mixed)
Omit lunchtime dose
Take normal evening dose
Manage long-acting insulin as above		 Take normal morning dose
Omit lunchtime dose
Take normal evening dose
Give long-acting insulin as normal
Continuous subcutaneous insulin infusions Aim CBG 6 - 10mmol/L
Maintain or reduce (10 - 20%) basal rate
Omit bolus doses associated with meal times
Consider pre-operative test of basal regimen

Variable rate insulin infusions

  • No one size fits all model and an individualised approach should be taken
  • Consider VRII if:
    • Missing more than one meal (T1DM or T2DM)
    • T1DM who have not received background insulin
    • Diabetic patient requiring emergency surgery
    • Those who are on an SGLT-2 inhibitor but didn't omit it pre-operatively
    • Suboptimal diabetes management as defined as an HbA1c >69mmol/mol
    • Persistent perioperative hyperglycaemia (>12mmol/l) in the context of acute decompensation

  • Fluids to run alongside:
    • Ideally 0.45% NaCl + 5% dextrose ± 0.15 - 0.3% KCl to meet fluid, electrolyte and dextrose susbtrate requirements
    • 0.18% NaCl + 4% dextrose ± 0.15 - 0.3% KCl may be used instead, but daily sodium monitoring and wariness of hyponatraemia is required
  • Do not stop substrate infusion

  • Short acting, Intermediate and Pre-mixed Insulins should be discontinued and replaced by a long-acting basal insulin at a dose of 0.2 units per kilogram
  • Continue to administer long-acting basal insulin but at 80% of the usual dose
  • Measure capillary blood glucose hourly

  • General aims are to:
    • Avoid hypoglycaemia or hyperglycaemia by maintaining blood glucose 6-12mmol/L
    • Prevent ketoacidosis
    • Prevent hypokalaemia associated with insulin infusions
    • Measure glucose levels frequently to prevent the above

  • Better glycaemic control improves perioperative morbidity and mortality
  • The surgical stress response:
    • Stimulates gluconeogenesis
    • Impairs peripheral glucose uptake (actions of cortisol, glucagon, catecholamines and growth hormone)
    • This may require an escalation of usual insulin therapies

Glucose monitoring

  • Aim glucose 6 - 12mmol/L
  • Measure CBG
    • Every 30mins during LSCS
    • Every 30mins if on VRII
    • Every 1hr during other operations

Glycaemic management

  • If CBG >12mmol/L and insulin has been admitted, check capillary ketones; if >3mmol/L then treat as DKA

  • If CBG >12mmol/L but no DKA, give subcutaneous, rapid - acting insulin e.g. Novorapid
    • In T1DM give units adequate to restore normal BM with knowledge 1IU will drop CBG by 3mmol/L
    • In T2DM give 0.1 IU/kg
    • Check CBG hourly
    • Repeat dose after 2hrs if necessary
    • If no response → VRII

  • If CBG <6mmol/L give 10g glucose e.g. 50ml 20% dextrose

  • If CBG <4mmol/L give 20g glucose e.g. 100ml 20% dextrose

Anaesthetic technique

  • Utilise anaesthetic strategies to promote early return to usual diet and diabetes management
  • This may include regional anaesthesia, but also multi-modal analgesia and anti-emesis
  • Some suggestion magnesium may reduce post-operative glucose levels, although the effect is modest and requires a 24hr infusion

Dexamethasone

  • May be given is the benefit of avoiding PONV outweighs risk of hyperglycaemia
  • Requires glucose monitoring for 4hrs post-administration

  • PADDAG Trial (2021)
    • A single dose of dexamethasone (4 - 8mg) did not significantly affect maximal blood glucose in the 24hrs after surgery
    • Other trials demonstrated higher doses (>8mg) were associated with a significant increase in blood glucose vs. 4mg doses, although the difference was only 1mmol/L

  • PADDI Trial (2021)
    • 8mg IV dexamethasone did not increase frequency of surgical site infections

Airway considerations

  • Anticipate more difficult airway if stiff joint syndrome present

  • Higher risk of aspiration if autonomic dysfunction and gastroparesis
    • Gastric emptying is lower in diabetic patients vs. controls, but this mayn't necessarily cause an ↑ gastric residual volume nor higher incidence of aspiration (BJA, 2021)
    • Incidence of full stomach may be as high as 50% in patients undergoing emergency surgery and DM is an independent risk factor for this
    • Pre-medicate with antacids/prokinetics
    • Consider lower threshold for RSI technique
    • Avoid excessive opioids pre-operatively as may further exacerbate delayed gastric emptying

Other considerations

  • Ensure adequate antibiotic prophylaxis
  • Avoid nephrotoxic drugs in those with diabetic nephropathy
  • Avoid anticholinergic drugs in patients with autonomic bladder dysfunction

  • Surgical stress response may cause a rise in blood glucose
  • Measure blood glucose in recovery
  • Measure blood ketone level daily if was on an SGLT-2 inhibitor pre-operatively

  • Consider higher care areas for close monitoring of blood glucose levels ± VRII
  • Encourage DrEaMing approach
  • Aim to return patient to self-management of normal anti-diabetic regimen ASAP
  • Liaise with diabetic team about returning to normal diet and insulin regimes if concerns of complexities