oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
- Diabetes mellitus affects 230 million people worldwide.
- 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 certain diseases (for example, they are 4 times more likely to have 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.
- Cardiovascular disease. The high risk of large vessel coronary artery disease in patients with diabetes is well recognised with data from the Framingham study showing a risk in men and women between 2.4 and 5.1 times greater. Diabetes is the most common cause of myocardial infarction in people under the age of 30 years.
- Peripheral artery disease is under-recognised as it is often asymptomatic. It is present in 25-30% of those with diabetes and is an important marker for systemic atherosclerosis (70% of such patients die from coronary heart disease, 5-10% from stroke).
- Renal disease. Diabetic nephropathy develops in close to 40% of patients with type 1 diabetes, and between 5% and 40% of patients with type 2 diabetes.
- Diabetic retinopathy occurs in up to 20% of patients with diabetes.
- Neurological disease is common:
- Skin disease is more common.
- Susceptibility to infection is increased.
- Hypoglycaemia can occur.
- Diabetic ketoacidosis can occur with trauma and surgical complications.
Perioperative risks and complications of diabetes mellitus
Interestingly, the risk of complications after coronary artery stenting may not be increased in diabetes. In another study of complications after renal transplantation there was no difference between recipients with diabetes and those without diabetes and it seems that there are other greater risk factors for poor outcome (including age of donor and recipient, time awaiting transplantation, etc). This perhaps illustrates that 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). However, again it is not straightforward. In one study of cardiovascular complications in patients with diabetes undergoing major vascular surgery, after controlling for specific comorbid conditions, the only independent association was between patients with insulin treatment and the risk of cardiovascular complications. Similarly, despite worse demographic and clinical characteristics, patients with diabetes having coronary artery surgery had a low mortality and morbidity (comparable with control patients). Although diabetes may not be a risk factor for adverse outcome following coronary artery surgery, the long-term survival in patients with diabetes remains significantly inferior compared with patients without diabetes. However, other studies show a clear increase in risk of perioperative cardiac events in those with diabetes - for example, after renal transplant carotid endarterectomy and vascular surgery.
- Patients with diabetes mellitus undergoing percutaneous coronary intervention (PCI) are at increased risk for adverse outcomes. It is not clear how this compares with surgery.
- Cardiac arrest as a consequence of autonomic neuropathy.
- Chronic renal failure patients (diabetic nephropathy) have a worse outcome (complications and mortality) even accounting for the increased risk of associated conditions (hypertension, peripheral vascular disease).
- 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.
- Problems with lower limb ischaemia. This is consistent with high incidence of peripheral vascular disease.
- Heel pressure sores, particularly with peripheral neuropathy.
- Postoperative wound infection.
- 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.
- Poor intraoperative blood glucose control is associated with worse outcome after cardiac surgery in patients with diabetes.
- Diabetes mellitus is a risk factor for prolonged intensive care after cardiac surgery and prolonged length of hospital stay after surgery.
Pre-operative assessment of the patient with diabetes
- 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 vascular 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.
- Renal disease:
- Symptoms of polyuria may reflect glycosuria or renal failure.
- 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.
- Blood glucose (serial readings) and HbA1c (more relevant for long-term control). Blood glucose should be maintained at 4-10 mmol/L and it is very important to avoid hypoglycaemia. If blood sugar cannot be maintained below 13 mmol/L, surgery should be deferred (risk of ketoacidosis or hyperosmolar state.
- ECG (with Valsalva manoeuvre) to assess for ischaemic and other cardiovascular disease.
- U&Es (assess for renal complications) and estimated glomerular filtration rate (eGFR), if available.
- 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.
- General anaesthesia. Consideration should be given to:
- The presence of cardiovascular and renal disease.
- Prevention of intra-operative 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.
Type 1 diabetes mellitus
It is usually best to admit patients 2-3 days before elective surgery, particularly if outpatient adjustments are difficult. There are different recommended routines but it is important that ward staff and those responsible for postoperative care have clear instructions. Complicated regimens can cause confusion amongst staff.
- Ensure good pre-operative control usually with short-acting insulin (or a mixture of short- and intermediate-acting insulin) twice daily. Extra short-acting insulin can be added if necessary.
- Monitor blood glucose throughout the day.
- On the day of surgery starve from midnight and do not give the first dose of insulin.
- Operation should be as early as possible (ie put the patient with diabetes first on the list).
- Check glucose and electrolytes early on the day of surgery (defer if glucose >13 mmol/L or if there is significant electrolyte disturbance).
- Start intravenous (IV) infusions of dextrose (500 mls 10% dextrose plus 10 units soluble insulin plus 10 mol KCl at 125 mls per hour). Check blood glucose and electrolytes at the end of the operation or at 1- to 2-hourly intervals.
- Monitor blood glucose during surgery at least every 30 minutes. Continue this as long as blood glucose is between 5-10 mmol/L. Reduce insulin to 5 units if less than 5 mmol/L and increase to 15 units if blood glucose is 10-20 mmol/L (new infusion needed of course).
- After surgery, check glucose every 2 hours and electrolytes every 6-12 hours, adjusting infusions as necessary.
- Continue infusions but, when eating normally, restart subcutaneous insulin (as before surgery).
Type 2 diabetes mellitus
- Pre-operatively, control should be assessed.
- Patients controlled by diet alone do not usually need any special measures, providing control on diet is adequate.
- It is better to use short-acting drugs (for example, glipizide).
- Remember that the hypoglycaemic effect of sulphonylureas is enhanced by some drugs (for example, aspirin, sulphonamides, anticoagulants).
- Metformin should be discontinued 48 hours prior to and subsequent to surgery in order to reduce the risk of lactic acidosis.
- If control is inadequate, insulin may be needed.
- Insulin can be required in the postoperative phase temporarily.
- On the day of surgery keep 'nil by mouth' as usual and omit short-acting sulphonylurea.
- Monitor blood glucose as for type 1 diabetes above. If blood glucose is >13 mmol/L, use insulin to control (small doses of soluble insulin).
- For major surgery or where there is prolonged postoperative starvation, use glucose and insulin infusions as set out above.
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.
- 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 is hazardous but is 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, and hepatic and renal failure.
Further reading & references
- Basic guidelines - insulin adjustment for multiple daily injections/basal bolus regimen, Diabetes healthnet UK (March 2006)
- Diabetes guidelines; NICE
- Antibiotic prophylaxis in surgery, SIGN Guidelines (Apr 2014)
- International Federation for Diabetes
- Guidelines in Clinical Anaesthesia, Blackwell Scientific Publications 1985
- Kannel WB; Lipids, diabetes, and coronary heart disease: insights from the Framingham Study. Am Heart J. 1985 Nov;110(5):1100-7.
- Diehm C, Lawall H; Diabetes, heart surgery and the peripheral arteries. Clin Res Cardiol. 2006 Jan;95(Supplement 1):i63-i69.
- Lanzer P, Weser R, Prettin C; Carotid-artery stenting in a high-risk patient population--single centre, single operator results. Clin Res Cardiol. 2006 Jan;95(1):4-12.
- Bittar J, Cepeda P, de la Fuente J, et al; Renal transplantation in diabetic patients. Transplant Proc. 2006 Apr;38(3):895-8.
- Gaston RS, Deierhoi MH, Young CJ, et al; "High-risk" renal transplantation: evolving definitions at a single center. Clin Transpl. 2004;:121-6.
- Axelrod DA, Upchurch GR Jr, DeMonner S, et al; Perioperative cardiovascular risk stratification of patients with diabetes who undergo elective major vascular surgery. J Vasc Surg. 2002 May;35(5):894-901.
- Antunes PE, de Oliveira JF, Antunes MJ; Coronary surgery in patients with diabetes mellitus: a risk-adjusted study on early outcome. Eur J Cardiothorac Surg. 2008 Jun 6;.
- Filsoufi F, Rahmanian PB, Castillo JG, et al; Diabetes is not a risk factor for hospital mortality following contemporary coronary artery bypass grafting. Interact Cardiovasc Thorac Surg. 2007 Dec;6(6):753-8. Epub 2007 Sep 27.
- Mohammadi S, Dagenais F, Mathieu P, et al; Long-term impact of diabetes and its comorbidities in patients undergoing isolated primary coronary artery bypass graft surgery. Circulation. 2007 Sep 11;116(11 Suppl):I220-5.
- Humar A, Kerr SR, Ramcharan T, et al; Peri-operative cardiac morbidity in kidney transplant recipients: incidence and risk factors. Clin Transplant. 2001 Jun;15(3):154-8.
- Aziz I, Lewis RJ, Baker JD, et al; Cardiac morbidity and mortality following carotid endarterectomy: the importance of diabetes and multiple Eagle risk factors. Ann Vasc Surg. 2001 Mar;15(2):243-6. Epub 2001 Mar 1.
- Schluter M, Reimers B, Castriota F, et al; Impact of diabetes, patient age, and gender on the 30-day incidence of stroke and death in patients undergoing carotid artery stenting with embolus protection: a post-hoc subanalysis of a prospective multicenter registry. J Endovasc Ther. 2007 Jun;14(3):271-8.
- Roghi A, Palmieri B, Crivellaro W, et al; Relationship of unrecognised myocardial infarction, diabetes mellitus and type of surgery to postoperative cardiac outcomes in vascular surgery. Eur J Vasc Endovasc Surg. 2001 Jan;21(1):9-16.
- Weber FD, Schneider H, Wiemer M, et al; Sirolimus eluting stent (Cyphertrade mark) in patients with diabetes mellitus: results from the German Cypher Stent Registry. Clin Res Cardiol. 2008 Feb;97(2):105-9. Epub 2007 Dec 6.
- De Servi S, Guastoni C, Mariani M, et al; Chronic renal failure in acute coronary syndromes. G Ital Cardiol (Rome). 2006 Apr;7(4 Suppl 1):30S-35S.
- Sigala F, Georgopoulos S, Langer S, et al; Outcome of infrainguinal revascularization for critical limb ischemia in diabetics with end stage renal disease. Vasa. 2006 Feb;35(1):15-20.
- Rockman CB, Saltzberg SS, Maldonado TS, et al; The safety of carotid endarterectomy in diabetic patients: clinical predictors of adverse outcome. J Vasc Surg. 2005 Nov;42(5):878-83.
- Arabshahi KS, Koohpayezade J; Investigation of risk factors for surgical wound infection among teaching hospitals in Tehran. Int Wound J. 2006 Mar;3(1):59-62.
- Malmstedt J, Wahlberg E, Jorneskog G, et al; Influence of perioperative blood glucose levels on outcome after infrainguinal bypass surgery in patients with diabetes. Br J Surg. 2006 Jun 16.
- Ouattara A, Lecomte P, Le Manach Y, et al; Poor intraoperative blood glucose control is associated with a worsened hospital outcome after cardiac surgery in diabetic patients. Anesthesiology. 2005 Oct;103(4):687-94.
- Gandhi GY, Nuttall GA, Abel MD, et al; Intraoperative hyperglycemia and perioperative outcomes in cardiac surgery patients. Mayo Clin Proc. 2005 Jul;80(7):862-6.
- Ghotkar SV, Grayson AD, Fabri BM, et al; Preoperative calculation of risk for prolonged intensive care unit stay following coronary artery bypass grafting. J Cardiothorac Surg. 2006 May 31;1(1):14.
- Schmiesing CA, Brodsky JB; The preoperative anesthesia evaluation. Thorac Surg Clin. 2005 May;15(2):305-15.
- Huang CJ, Kuok CH, Kuo TB, et al; Pre-operative measurement of heart rate variability predicts hypotension during general anesthesia. Acta Anaesthesiol Scand. 2006 May;50(5):542-8.
- Tamai D, Awad AA, Chaudhry HJ, et al; Optimizing the medical management of diabetic patients undergoing surgery. Conn Med. 2006 Nov-Dec;70(10):621-30.
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Dr Richard Draper
Dr Richard Draper