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Mimi Huizinga, M.D.
02-03-2011
Trinidad and Tobago Information Author: Sean S. Perot, MRCPI
- Major lower limb amputation in people with diabetes is one of the commonest operations performed in Trinidad and Tobago. Pre-operative assessment by both the anaesthetist and physician well in advance of elective surgery.
- History includes hyperglycaemic symptoms (eg,polyuria/polydipsia),current treatment of diabetes and glucose monitoring.
- Symptoms and treatment of chronic microvascular or macrovascular complications and treatment of other chronic medical conditions.
- Nondiabetic medications that may affect blood glucose levels (eg, corticosteroids)
- Tobacco and alcohol consumption.
- Physical examination should include: Blood pressure (including orthostatic measurements), airway examination; cardiac examination.
- Investigations: Hb A1c & RBS, FBG, creatinine, electrolytes. ECG
- On the day of surgery, our practice is for patients on oral regimens to discontinue medications.
- Discontinue metformin preoperatively because of the risk of developing lactic acidosis.
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Short-acting insulin may be administered subcutaneously as a sliding scale or as a continuous infusion, depending on the type and duration of surgery.
- Patients should be monitored during the surgery to assess for hyperglycemia and hypoglycemia.
- Postoperative: continue sliding scale insulin but if using sliding scale insulin R only. Note that target control is often not achieved. Consider IV insulin infusion in critically ill patients.
- Restart previous diabetic medication or twice daily insulin (N & R) as soon as the patient is able to eat.
- Targets: Fasting: 90-126 mg/dL, Random: <200 mg/dL
- Perioperative care of people with diabetes involves pre-operative assessment and modification of usual anti-diabetic medications, intra-operative and post-operative management.
- Patients with diabetes have an estimated 50% lifetime risk of undergoing surgery.
- Patients with diabetes at increased risk of complications due to the complexity of care, increased risk of infections, and possible asymptomatic coronary artery disease (CAD).
- Diabetes - Assessment includes current medications; baseline glycemic control (blood glucose ranges, A1C level within last 3 months); history of diabetic ketoacidosis; long-term complications (retinopathy, nephropathy, neuropathy); history of hypoglycemia (awareness, frequency, severity).
- If diabetic control is poor, consider postponing elective surgery.
- Medication needs will change in the peri-operative and post-operative period; pre-operative time is a good time to plan for these changes.
- Cardio - Thorough history and physical and EKG. If symptoms of CAD are present, consider cardiac stress test prior to elective surgery.
- Pulmonary - With obesity, consider obstructive sleep apnea (OSA). Treatment of OSA for a minimum of 2 weeks is needed to decrease risk associated with obstructive sleep apnea. If OSA is diagnosed, may require extubation to CPAP. Other pulmonary considerations include chronic obstructive pulmonary disease and asthma.
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Nephropathy - Document GFR and stage of chronic kidney disease if present, as this may affect dosage of medications.
- Hypertension - Consider medications prior to surgery. Do not hold beta-blockers prior to surgery but do stop other antihypertensives the morning of surgery.
- Anti-platelet therapy - Hold aspirin for 7 days prior to surgery. The management of long term antithrombotic therapy depends on the patients risk of thromboembolism and the type of surgery to be performed. The American College of Chest Physicians recommends that patients at high risk of thromboembolism (e.g., mechanical heart valve) should be bridged from coumadin to heparin, however, those with low risk may stop antithrombotic therapy for 5 days before surgery. If the INR in those who stopped antithrombotic therapy remains elevated, oral vitamin K should be used to normalize INR. Antithrombotic therapy should resume 12-24 hours after surgery.
- Some evidence suggests that better baseline glycemic control is associated with a reduction in post-operative infections.
- The ADA recommends that fasting blood glucose <140 and random blood glucose <180 for hospitalized patients.
- Patients with T2DM on diet alone usually do not require therapy before surgery, but fast acting insulin by sliding scale according to blood glucose may be used to treat hyperglycemia before and during surgery.
- T2DM patients on oral agents should continue their normal therapy until the morning of surgery when medications are held. Most will not require additional therapy, but may be given sliding scale insulin if needed
- Insulin requiring patients can continue their subcutaneous insulin, usually reducing long-acting insulin by one half the evening pre-operatively to prevent hypoglycemia. The morning of surgery, hold short-acting insulin and administer one half to two thirds of basal insulin. People with type 1 diabetes must receive basal insulin to prevent ketoacidosis. Fast-acting insulin may be given to control hyperglycemia during surgery. Administer IV fluids containing 5% dextrose at 75-125cc/hour (3.75-6.25 grams of glucose per hour) to avoid catabolic effects of starvation and avoid hypoglycemia. Alternatively, insulin may be given by continuous IV infusion intra-operatively.
- Potassium may be added (10-20 mEg/L) in patients with normal renal function and normal pre-operative serum potassium.
- Longer, complex operations require more intensive management, often with a glucose-insulin-potassium infusion.
- Tight glycemic control (80-110 mg/dL) in ICU and cardiac surgery patients has become a controversial issue, one center reporting positive results while a recent multicenter trial found worse outcome with tight glycemic control.
- Immediately post-operatively, blood glucose monitoring should occur at least four times a day (before meals and at bedtime). More frequent monitoring is needed if the patient is on an insulin infusion.
- Once patients are eating well, restart oral agents. However, hold metformin until confident of normal renal and hepatic function and lack of congestive heart failure. Also, avoid thiazolidinediones in patients with congestive heart failure or impaired liver function; avoid sulfonylureas with severe renal impairment. Restart sulfonylureas at reduced dosage if patient is consuming fewer calories, to prevent hypoglycemia.
- Follow general principles of hospital management, especially for patients on insulin at baseline.
- Surgery and general anesthesia are associated with a neuroendocrine response that can lead to hyperglycemia and ketosis.
- First goal is to maintain fluid/electrolyte balance and prevent marked hyperglycemia, ketoacidosis, nonketotic hyperosmolar state and hypoglycemia.
- Second goal is to promote wound healing and minimize the post-operative catabolism by reasonably glycemic control.
- Immediate metabolic status (glycemia, ketosis) as well as established complications of diabetes increase surgical risk.
- Elective surgery allows for a more thorough pre-operative evaluation and management than urgent surgery.
- With emergency surgery, manage hyperglycemia with IV or subcutaneous fast-acting insulin, and hypoglycemia with 5% or 10% IV dextrose infusions. Be aware of stopping/reversing anticoagulation; stopping metformin; taking previously-administered long-acting insulin into account.
- With elective surgery, evaluate as above, and prepare patient as well as possible for surgery.
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