Precautions for patients with diabetes undergoing surgery

Introduction¹

• There is a rising incidence and prevalence of diabetes mellitus. About 50% of people with diabetes mellitus are unaware of their condition. Approximately 25% of all patients with diabetes undergoing surgery are undiagnosed on admission to hospital.

• Patients with diabetes have a higher risk of cardiovascular disease. Patients with diabetes have a higher perioperative risk. They are more likely because of their disease to require surgery and those undergoing surgery are likely to be less well controlled and to have complications from their diabetes.

• Surgeons and anaesthetists operating on patients with diabetes should be familiar with the risks attached to having diabetes, and to the particular risks of the particular surgery and of anaesthesia in patients with diabetes.

Risks and complications of diabetes mellitus

Patients with diabetes mellitus are at risk of the complications of the disease. It is worth considering these in outline when considering how best to care for patients with diabetes undergoing surgery. See also the separate Diabetes Mellitus article.

Perioperative risks and complications of diabetes mellitus

It is important in assessing risk of complications in patients with diabetes undergoing surgery to consider the specific type of surgery and anaesthetic technique. There is evidence for higher risk in those with diabetes undergoing surgery and, when such evidence is lacking, it may in part be testament to the relative safety of modern surgery and anaesthesia.

However, the following risks and observations are worth considering in patients with diabetes undergoing surgery:

• Myocardial infarction postoperatively (may be silent, has a greater mortality). There is an increased risk of postoperative acute myocardial infarction for people with diabetes.² The myocardial infarction may be silent (no obvious symptoms) and has a greater overall mortality for people with diabetes.

• Patients with diabetes mellitus undergoing percutaneous coronary intervention (PCI) are at increased risk for adverse outcomes.³ It is not clear how this compares with surgery.

• Cardiac arrest as a consequence of autonomic neuropathy.

• Patients with diabetes and chronic kidney disease (diabetic nephropathy) have a worse outcome (complications and mortality) even accounting for the increased risk of associated conditions (hypertension, peripheral arterial disease).^{4 5}

• Stroke. This is consistent with the generally increased risk in diabetes mellitus, although again the surgical procedure and other risk factors for stroke (for example, smoking, anaesthetic technique) are important.⁶

• Problems with lower limb ischaemia. This is consistent with high incidence of peripheral arterial disease.⁷

• Heel pressure sores, particularly with peripheral neuropathy.

• Increased risk of postoperative wound infection.⁸

• Other infections such as chest and urinary infections are more common in those with diabetes. Tuberculosis can occur particularly in elderly patients with diabetes.

• Disruption and worsening of control of diabetes (for example, from the stress of surgery, lack of oral intake, postoperative vomiting, etc).

• Poor perioperative control of diabetes is associated with unfavourable outcomes in, for example, infra-inguinal bypass surgery.⁹

• Poor intraoperative blood glucose control is associated with worse outcome after cardiac surgery in patients with diabetes.^{10 11}

• Diabetes mellitus is a risk factor for prolonged intensive care after cardiac surgery.¹²

Recommendations for primary care teams¹³

Primary care referrals requesting surgical consultations for people with diabetes should include:

• Type of diabetes.

• Main diabetes care provider (primary or secondary care).

• Date of last diabetes review.

• HbA1c levels within three months prior to referral.

• List of all current medications (dose/route) and medical devices used (pumps, flash monitor, continuous glucose monitoring).

• Body mass index (BMI) with date of measurement if available.

• Latest blood pressure reading with date of measurement.

• Estimated glomerular filtration rate (eGFR) with date of measurement.

• Presence and management of comorbidities and diabetes complications.

Primary care teams should:

• Aim to optimise glycaemic management, aiming for an HbA1c of less than 69 mmol/mol (8.5%) before referral if safe and practical.

• Consider referral for diabetes specialist support if the HbA1c is greater than 69 mmol/mol (8.5%).

• Optimise diabetes related comorbidities and any other comorbidities impacting on general health and well-being.

• Discuss likely impact of surgery on the person's social situation.

• Advise people with diabetes on the importance of general improvements in health, including exercise, weight management, importance of good nutrition, smoking cessation, reduction in alcohol, and psychological preparation and well-being.

Pre-operative care

A careful pre-operative assessment should be done and may help improve outcome:¹⁴

• To establish the history of the patient's diabetes and the state of their control of the diabetes.

• To look for complications of diabetes mellitus.

• To establish the safest method of anaesthesia and surgery.

It is apparent from a review of the risks of surgery associated with diabetes mellitus that the assessment and reduction of risk require an individual assessment of the particular patient and the surgery being undertaken.

History and examination

• Assessment of control should be made (records of HbA1c, etc).

• Cardiovascular disease:
  

  • Evidence of angina, intermittent claudication should be sought.

  • Examine for peripheral arterial disease.

  • Examine for postural hypotension (systolic fall of >30 mm Hg on standing).

• Neurological disease:
  

  • Symptoms of numbness, pain, paraesthesia, leg ulcers, transient ischaemic attacks, etc.

  • Postural hypotension gives a late indication of autonomic neuropathy.

  • An assessment of heart rate variability (HRV) during deep breathing is a much better way of detecting autonomic neuropathy earlier.¹⁵

• Renal disease:
  

  • Symptoms of polyuria may reflect glycosuria or chronic kidney disease.

  • Anaemia and hypertension should be detected as possible associated conditions.

• Skin, feet and general examination:
  

  • The skin should be examined for sepsis.

  • Pressure areas (heels, buttocks, etc) should be examined for sores.

Pre-operative investigation

Should include:

• Blood glucose (serial readings) and HbA1c (more relevant for long-term control). Blood glucose control must be optimised before surgery if possible.

• FBC.

• ECG (with Valsalva manoeuvre) to assess for ischaemic and other cardiovascular disease.

• U&Es (assess for renal complications) and estimated glomerular filtration rate (eGFR).

• Urine analysis. Ketones (poor control), protein (possible renal complications) and bacteriology (for infection).

• CXR. This may be indicated to screen for pulmonary infection, including tuberculosis.

Choice of anaesthetic

• Local or general anaesthesia can be used.

• Local anaesthesia:
  

  • Reduces the stress response.

  • Hypoglycaemia readily detectable with the patient awake.

  • Postoperative nausea reduced.

  • Easy postoperative control of diabetes.

  
  There are disadvantages of regional blocks with cardiovascular disease and some neurological conditions.

• General anaesthesia. Consideration should be given to:
  

  • The presence of cardiovascular and renal disease.

  • Prevention of intraoperative hypoglycaemia.

  • Autonomic neuropathy (it can mask hypoglycaemia and may exacerbate respiratory depression with opioids).

  • Avoidance of hypotension (increased risk of spinal cord infarction).

  • Protection of pressure areas.¹⁶

Perioperative management of diabetes

Guidance on perioperative management for people with diabetes is included in the Centre for Perioperative Care guidance, 'Guideline for Perioperative Care for People with Diabetes Mellitus Undergoing Elective and Emergency Surgery'.¹³

Emergency situations

In general, emergency or non-elective cases must have blood glucose controlled with insulin, glucose and potassium infusions as above, with special attention being given to rehydration before surgery.

Pitfalls

• Diabetic ketoacidosis. This can present as abdominal pain and vomiting, with the vomiting usually preceding the pain (unlike in the acute abdomen when pain usually precedes vomiting). If diabetic ketoacidosis does not respond to treatment, it should be remembered that the acute abdomen may have triggered diabetic ketoacidosis.

• Anaesthesia and surgery in diabetic ketoacidosis are hazardous but occasionally required (eg, for perforated diverticular abscess). For example, there is a risk of cerebral oedema (resulting from swings in serum osmolarity) and the effects of acidosis on ventilation can cause problems.

• Hyperosmolar non-ketotic diabetic coma. These patients rarely require surgery but if required, it is high-risk. Heparinisation is usually required.

• Lactic acidosis should be suspected when there is acidosis but no ketosis. It can be caused by the effects of biguanides but occurs also in septicaemia, pancreatitis, liver failure and chronic kidney disease.