Diabetes Mellitus

This covers general considerations and perioperative management of diabetes. The diabetic crises are covered such as DKA, HHS, and euglycaemic DKA are covered at Diabetic Ketoacidosis, Hyperosmolar Hyperglycaemic State, and Euglycaemic Diabetic Ketoacidosis respectively.

Epidemiology and Risk Factors

Highly prevalent in first world countries:

  • 6-7% of population, and rising Up to 30% of inpatients.

Pathophysiology

Aetiology

Clinical Manifestations

History

Examination

Diagnostic Approach and DDx

Investigations

Management

Anaesthetic Considerations

Diabetes is included in multiple scoring systems, and is an obvious risk factor for perioperative morbidity and mortality. Key outcomes include:

  • Mortality
    50% ↑.
  • Respiratory complications
    2.4-fold ↑.
  • AKI
  • Infection
    • Surgical site infections
    • UTI
  • Hyper- and hypo-glycaemia
  • Medication errors
  • Acute diabetic metabolic states
    • HHS
    • DKA

Perioperative risk is further ↑ in:

  • Smokers
  • Long duration of diabetes
  • Poor glycaemic control
  • Obesity
  • HTN
  • ↑ lipids

Key Considerations:

  • C
    • Cardiac risk assessment
      ↑ Risk of CAD and silent ischaemia.
  • D
    • Perioperative BSL
      Surgery and anaesthesia precipitate a neuroendocrine stress response and counterregulatory hormone release
      • Leads to insulin resistance, ↓ peripheral glucose utilisation, ↑ lipolysis and protein catabolism
      • Significant attention must be given to perioperative management of blood glucose and hypoglycaemics
    • Insulin dependency
      More important than aetiology.
    • Diabetic therapies
      Agents, dose, and timing.
    • Presence of diabetic complications
      • Microvascular
        • Autonomic neuropathy
          ↑ peri-induction instability of cardiovascular parameters.
      • Macrovascular
    • Baseline glucose control
      Average, range, frequency of monitoring, and HbA1c.
      • An HbA1c should be performed if not done in the last 3 months
        Elevated HbA1c is predictive of postoperative adverse events.
        • Recommended to cancel elective surgery if HbA1c >8.5%
          However, no evidence suggesting that reducing it improves outcome
    • Hypoglycaemic episodes
      Frequency, timing, symptoms, severity.
    • Goals of management
      • Avoid hypo/hyperglycaemia
        Aim BSL 6-10mmol/L.
      • Prevent DKA/HHS
      • Maintain euvolaemia
      • Aim surgery as first on a morning list
        Minimises disruption to fasting.

Perioperative Management

General Principles:

  • Place patient first on an AM list
  • Withhold PO hypoglycaemics
    Varies depending on size of operation and drug.
  • Adjust insulin dosing
    Depends on timing of list.

Perioperative Oral Hypoglycaemic Management

Class Generic Name Recommendation Rationale
Biguanide Metformin Withhold 24 hours pre-major surgery ↑ risk of lactic acidosis and tissue hypoxia if elimination impaired by renal hypoperfusion; can proceed with minor surgery if the patient has taken it
Sulphonylurea Gliclazide, Glipizide, Glimepiride Withhold day of surgery ↑ risk of hypoglycaemia
Glitazones Rosiglitazone, Pioglitazone Withhold day of surgery
GLP-1 agonists Exanatide Withhold day of surgery
DPP-4 inhibitors Sitagliptin Withhold day of surgery Alter GI motility
SGLT-2 inhibitors Dapagliflozin, canagliflozin, empagliflozin Withhold for 3 days prior. Measures ketones, if >0.6-1 then measure pH and BE and delay surgery. If acidotic and unwell, then treat as euglycaemic DKA and refer to endocrinology. Euglycaemic DKA

Perioperative Insulin Management

Management of insulin depends on:

  • The type of insulin
  • The timing of the procedure
  • Whether the patient is taking bowel preparation
Type of Insulin Trade Names Day PRIOR to procedure Morning of procedure; for an AM list Morning of procedure; for a PM list
Short Acting
  • Novorapid
  • Humalog
  • Actrapid
  • Usual doses
  • Half usual dose during bowel preparation
  • Withhold
  • Give sliding scale
  • Half usual dose with early morning breakfast
Intermediate Acting
  • Protaphane
  • Humulin NPH
  • Give 2/3rds of usual dose
  • Half usual dose during bowel preparation
  • Withhold
  • Give sliding scale
  • Half usual dose with early morning breakfast
Long Acting/Basal
  • Lantus
  • Levemir
  • Give 2/3rds of usual dose
  • Half usual dose during bowel preparation
  • Give 2/3rds of usual dose
  • Give 2/3rds of usual dose
Pre-mixed
  • Novomix 30
  • Humalog Mix 25/Humalog Mix 50
  • Mixtard 30/70
  • Give normal dose with dinner
  • Half usual dose during bowel preparation
  • Withhold
  • Give sliding scale
  • Half usual dose with early morning breakfast
  • Give sliding scale

Perioperative Hypoglycaemia Management

  • Check BSL Q2H whilst fasting
  • Target BSL is ~7.5mmol/L, unless this is below the patients ‘hypo’ point

If BSL is:

  • ⩽4 mmol/L
    • Give glucose
      IV preferable to maintain fasting status.
    • Notify anaesthetist
    • Recheck BSL every 15 minutes
  • ≥10 mmol/L and the patient is fasting

Glucose options:

  • Parenteral
    • 50-100mL of 10-20% dextrose
    • 1mg IM glucagon
  • Enteral
    • Buccal sugar
    • 150-200mL juice
    • 90-120mL lucozade

Perioperative Management of Continuous Subcutaneous Insulin Infusion Pumps

  • Target a BSL of 6-10mmol/L
  • Give 5% dextrose (as for sliding scale insulin) whilst fasting
  • If BSL:
    • <4 mmol/L
      Withhold insulin, consider giving additional glucose.
    • ≥4 mmol/L
      Continue insulin infusion.
    • ≥10 mmol/L
      Administer additional short-acting insulin (as for sliding scale insulin).

Sliding Scales

Sliding scales should be based on the total daily insulin dose:

BSL (mmol/L) < 20 units/day
10-11.9 1 unit
12-15 2 units

Complications

  • ↑ Perioperative risk
  • C
    • Macrovascular disease
      • IHD
      • CVD
      • PVD
    • Microvascular disease
      Development related to both magnitude and duration of hyperglycaemia.
      • Retinopathy
        • Background retinopathy
          Small haemorrhages with lipid deposition at their margins.
        • Proliferative retinopathy
          Angiogenesis of retinal vessels into vitreous, which can lead to vitreous haemorrhage and retinal detachment.
      • Nephropathy
        Microalbuminuria, leading to proteinuria and then nephropathy.
      • Neuropathy
        • Sensory
          • Most common
          • Paraesthesias, neuropathic pain, or simple numbness
        • Focal
        • Autonomic
          Manifestation may occur in most organ symptoms.
          • Resting tachycardia
          • Silent ischaemia
          • Orthostatic hypotension
          • Loss of HR variability
          • Anhidrosis and failure of vasoconstriction
            Poor heat regulation.
          • Bladder dysfunction
          • Erectile dysfunction
          • Gastroparesis
          • Constipation/diarrhoea
  • E
    • DKA
    • HHS
  • F
    • AKI
  • I
    • Generally immunosuppressed
      Glycated neutrophils.

DKA is covered in detail under Diabetic Ketoacidosis.

HHS is covered in detail under Hyperosmolar Hyperglycaemic State.

Obstetric Complications

Complication rate ↑ in women with pre-existing diabetes, rather than gestational diabetes mellitus (GDM)

Maternal diabetes:

  • Results in complications for both:
    • Mother
      • ↑ insulin resistance
        ↑ over course of pregnancy.
      • Superimposed pre-eclampsia
      • Diabetic ketoacidosis
        Major factor ↑ perinatal morbidity and mortality.
    • Foetus
      • Placental insufficiency
        • Uteroplacental blood flow is reduced 35-45%
          Additional impairment if blood glucose control is poor.
        • Reduced oxygen transport on HbA1c
      • Foetal macrosomia
        • Shoulder dystocia
      • ↑ foetal acidosis at delivery
      • Structural defects
        • Cardiac
        • Spina bifida
        • Limb
        • Renal agenesis

Management considerations:

  • Prepartum
    • Oral glucose tolerance test
      Required for diagnosis.
    • Screen for end-organ involvement
    • Provide instructions for fasting BSL management
  • Intrapartum
    • No contraindications to regional analgesia or anaesthesia
      Note:
      • Epidural reduces foetal metabolic acidosis
      • Greater haemodynamic disturbance with spinal
        Likely due to higher sympathectomy.
    • Q30 minutely BSL if under GA section
  • Post-partum
    • Reduce insulin dose after delivery in women with pre-exiting DM
    • Cease insulin and OHGs after delivery in women with GDM

Prognosis

References

  1. The Royal Women’s Hospital. Diabetes: Perioperative Glycaemic Control (Non-Obstetric). Policy and Procedure Manual. 2013.
  2. Fowler MJ. Microvascular and Macrovascular Complications of Diabetes. Clinical Diabetes. 2008;26(2):77-82. doi:10.2337/diaclin.26.2.77
  3. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.