University of Toronto - Faculty of Medicine

 

Author
The revision of this chapter was prepared by Jacqueline James, MD, MEd, FRCPC

Surgery and medical illness are stressful events that will result in metabolic disturbances due to the influence of the key stress hormones: catecholamines, cortisol and glucagon. Patients with diabetes with underlying chronic complications are at higher risk for postoperative complications. Medications used in anesthesia or for pain control may modify the individual's ability to communicate symptoms of hyperglycemia or hypoglycemia and therefore patients need to be monitored closely in the perioperative period. Growing evidence suggests excellent glycemic control may improve outcomes in surgical patients and in the post-myocardial infarction period.

Many patients are admitted to hospital have preexisting diabetes which predisposes them to complications requiring admission such as cardiovascular disease, renal disease, infection and lower extremity wounds. Poor metabolic control in these patients may prolong hospital stay and increase morbidity. In Ontario, Canada diabetes in reported in 1/3 patients admitted with AMI/stroke, 40% those with CHF, 2/3 all non-traumatic amputations

 

• Prevention of hyperglycemia with its associated fluid and electrolyte losses.
• Prevention of diabetic ketoacidosis.
• Avoidance of significant hypoglycemia.
• Excellent glycemic control to reduce morbidity and mortality

 

• An appropriate medical and laboratory assessment should be performed.
• With adequate planning, the majority of diabetic patients undergoing elective surgery can be assessed in a pre-admission unit and admitted to hospital on the same day of surgery.
• Document whether the individual has type 1 or type 2 diabetes. Those with type 1 diabetes are at risk of diabetic ketoacidosis if deprived of insulin during hospitalization.
• Document usual glycemic control by history and objectively by A1C. If there is severe metabolic compromise, elective surgical procedures may need to be postponed until adequate glycemic control is obtained.
• The history should focus on symptoms suggestive of coronary artery disease, congestive heart failure, renal disease, gastroparesis or previous perioperative problems related to diabetes.
• A detailed preoperative cardiac assessment may be required depending on the cardiac history and the complexity of the surgical procedure.
• The physical examination should focus on blood pressure, volume status, evidence of significant cardiac disease or pre-existing neurologic complications of diabetes.
• Document usual regimen for the treatment of diabetes.
• Determine degree of hypoglycemic unawareness if present. Individuals with severe hypoglycemic unawareness will require modification of insulin regimens in hospital to prevent severe hypoglycemia.
• For major surgical procedures, routine lab investigations should include EKG, electrolytes, creatinine, urinalysis and AIC.
• In the presence of diabetic ketoacidosis, elective procedures should be postponed until the DKA resolves and glycemic control is regained.

 

• Prior to surgical procedures, patients should perform capillary glucose monitoring frequently at home and efforts should be made to modify medications or insulin to optimize glycemic control prior to surgery.
• On the day of surgery, glucose should be monitored at least every 2 hours starting in the morning and at least one hour prior to and immediately after surgery.
• During major procedures, blood glucose levels should be checked every 2 hours.
• In those with type 1 diabetes, urine ketones should be checked if glucose levels are greater than 15 mmol/L for a prolonged period of time, or if there is marked hyperglycemia.

 

• Irrespective of previous diabetes treatment regimen (i.e. diet, oral agents or insulin), all patients with diabetes undergoing major surgical procedures requiring postoperative intensive care should be treated with continuous intravenous insulin infusion .
• The insulin infusion should be initiated preoperatively (same day of surgery), continued intraoperatively and postoperatively for as long as the patient is requiring intensive care.
• Patients undergoing CABG should be maintained at 5.5-11.0 mmol/L intraoperatively.
• Previously advocated postoperative targets of extremely tight glycemic control (4.4 -6.1 mmol/L) were based on the Leuven protocol which showed a reduction in morbidity and mortality in patients treated to these targets. However, these results have been called into question by the results of NICE-SUGAR trial which suggested that extremely tight glycemic control may be deleterious. In this multicentre study severe hypoglycemia was excessive and morality rates higher in those treated with intensive therapy compared with those treated conventionally, aiming for glucose levels < 10mmol/L. Therefore, it is our recommendation, that post-op ventilated surgical patients be targeted in 7.0- 10.0 mmol/L range.
• Concomitant source of glucose (oral or parenteral) should be present while patient is receiving continuous insulin infusion.
• In order to achieve excellent glycemic control in this setting, the institution involved must develop a protocol which takes into account safety, resources and appropriate education for health care personnel involved in the care of these patients.
• Once the patient has been transferred out of the intensive care setting, glucose targets should be reevaluated and likely raised to ensure patient safety.

 

• For all other patients having major surgical procedures post-op glucose should be maintained 5.0-11.0 mmol/L based on consensus.
• Aim to replace basal insulin requirements i.e. non meal related insulin since the individual is usually kept NPO prior to operative procedures.
• The stress of surgery and counter-regulatory hormones may cause hyperglycemia and therefore higher than usual basal doses may required.
• If the surgical procedure is minor and/or local anesthetic is used, subcutaneous insulin may be used.
• If the surgical procedure is major and/or general anesthetic is used, or the individual is expected to remain NPO for a prolonged period of time, then an intravenous insulin infusion should be used.
• If the individual is in poor glycemic control, an intravenous insulin infusion should be used.
• Some glucose is generally also administered along with insulin to avoid hypoglycemia.

Patients on conventional insulin regimen of intermediate acting insulin and regular or rapid insulin in the morning:

• Patients should be advised to omit their usual am insulin.
• Those who have a tendency to hypoglycemia in the morning should be advised to take an adequate snack the night prior to the procedure.
• On arrival to hospital on the morning of surgery, give 1/2 to 1/3 of their total morning dose of insulin as intermediate acting insulin subcutaneously and an intravenous of 5% dextrose in water at 50-100 cc/hour.
• Lower rates of dextrose infusion will be required for patients with a history of heart or renal failure.
• If the individual is hyperglycemic on arrival to hospital, the IV solution should be modified to 2/3 and 1/3 or normal saline depending on the degree of hyperglycemia.
• If the individual is hypoglycemic on arrival to hospital, an IV bolus of glucose can be given to correct the hypoglycemia prior to surgery.
• Postoperatively, the blood glucose should be checked and regular or rapid insulin given subcutaneously to correct hyperglycemia or in preparation for a meal.
• The patient can usually resume their usual insulin dose in the evening post-op.

Patients on intensive insulin regimens with regular, rapid and no (or small doses) of intermediate acting insulin in the morning:

• Give a dose of intermediate acting insulin equivalent to their rapid acting or regular insulin subcutaneously and an intravenous of 5% dextrose in water at 50-100 cc/hour.
• Postoperatively, the blood glucose should be checked and regular or rapid insulin administered to correct hyperglycemia or in preparation for a meal.

Patients on Subcutaneous Insulin Pumps

• The usual basal rate can be continued and an IV of 5% dextrose in water run to keep the vein open.
• Regular or rapid insulin can be bolused post-op to correct hyperglycemia or in preparation for a meal.

• Intravenous infusions of insulin provide the most reliable and flexible way of delivering insulin
• Intravenous regular insulin takes immediate effect and has a short half life of 5-7 minutes.

Patients on Conventional or Intensive Insulin Regimens

• Calculate basal requirements as 40-50% of total daily insulin dose.
• Divide this basal dose by 24 and run the drip at this number of units per hour to start if the glucose level is well controlled.
• For example, a person normally requiring approximately 50 units of insulin per day would be started on an insulin infusion of 1 unit/hour (50 ÷ 2 = 25, 25 ÷ 24 ≈ 1 unit/hour).
• Run the insulin drip at a concentration of 1 unit of regular insulin in 10 cc D5W by infusion pump. This concentration should be modified if volume overload is a concern, however it provides reliable delivery of insulin.
• Piggy back the insulin drip onto the maintenance I.V. This will allow separate control of the insulin infusion from the maintenance I.V. solution.
• Provide maintenance IV of 5% Dextrose in water, 2/3 1/3, or normal saline at 50-125 cc/hour depending on volume and electrolyte requirements.
• Patients should have blood glucose levels checked frequently (every 1-2 hours) depending on the stability of the glucose levels and the clinical scenario.
• The dose of insulin should be modified to achieve goals of glycemic control set for that individual.
• Tight glycemic control can be achieved by frequent adjustment of insulin dosages which can be directed by dosing regimen scales and frequent review of the scales set.
• The insulin drip should be continued until the patient has resumed normal oral intake.
• There should be a period of overlap of 2-3 hours between the first subcutaneous insulin dose and the insulin drip to allow the subcutaneous insulin to take effect.

Patients on Subcutaneous Insulin Pumps

• Should be managed with intravenous insulin as above starting on the morning of surgery.
• Pumps should be disconnected once the intravenous insulin is started and until the individual is able to adequately take over control of pump administration post-op.

Minor Procedures

• Oral agents should be held on the day of surgery. Chlorpropamide should be held 48 hours prior.
• For those on sulfonylureas, I.V. D5W should be started on the morning of surgery at 50-100 cc/hour to avoid hypoglycemia.
• Oral agents should be resumed post-op.

Moderate Procedures

• Oral agents should be held the day of surgery. To be extra cautious, in procedures where there is a high risk of lactic acidosis, consider holding metformin the day before surgery. Metformin should be held until the patient is surgically stable.
• Insulin may be required to achieve adequate glycemic control in the perioperative period.
• If necessary, an insulin infusion with regular insulin as outlined above can be used.
• If the individual has never been on insulin, start with 0.5 - 1.0 unit per hour and adjust according to the glucose levels (see section 13.5A(ii)).

Minor Procedures

• For those taking bedtime insulin, hold oral agents in am and start IV D5W.
• For those taking am insulin, hold oral agents in am and give subcutaneous insulin according to guidelines for patients taking insulin (see Section 13.5A(i)).

Moderate Procedures

• For those taking bedtime insulin, hold oral agents in am and start insulin drip as necessary.
• For those taking am insulin, hold oral agents in am and start insulin in am according to above guidelines for insulin infusions (see Section 13.5A(ii)).

• If glycemic control was suboptimal prior to surgery, then oral agents should be introduced as necessary once the individual is eating a normal diabetic meal plan.
• Patients who are well controlled on diet therapy alone may become hyperglycemic and if poorly controlled should be managed with insulin until hyperglycemia resolves.

 

• Adequate I.V. glucose should be provided to prevent starvation ketosis when nothing is being taken by mouth.
• Adequate calories should be provided to counteract the resulting negative caloric and nitrogen balance once re-feeding has been established.

 

The DIGAMI (The Diabetes Mellitus Insulin Glucose Infusion in Acute Myocardial Infarction) study showed that intensive insulin therapy using an intravenous insulin infusion to maintain glucose level between 7.0 and 10.0 mmol/L for at least 24 hours in the post MI period, followed by multiple daily injections of subcutaneous insulin for at least 3 months resulted in an almost 30% reduction in long term mortality. In DIGAMI 2, patients were randomized to receive either usual care, iv insulin peri-MI and usual care, or iv insulin followed by multiple daily injections of insulin for 3 months. No differences in outcomes were seen with this trial but were similar to findings in the original DIGAMI study. Based on these two trials we recommend:

• Patients admitted to the coronary care unit with an acute myocardial infarction should have their glucose monitored and intravenous insulin initiated if the glucose level is >12.0 mmol/L in order to maintain glucose levels between 7.0 - 10.0 mmol/L for at least 24 hours.
• An intensive subcutaneous insulin regimen to maintain tight glycemic control to current guidelines for optimal glycemic control in adults using insulin or oral agents is then advised for a minimum of 3 months.
• In order to achieve tight glycemic control in this setting, the institution involved must develop a protocol which takes into account safety, resources and appropriate education for health care personnel involved in the care of these patients.
• Hypoglycemia must be avoided.
• When patients are discharged from hospital a plan for tight glycemic control should be put into place regardless of what pharmacological agent is chosen.
• Intensive management of glucose using subcutaneous insulin as an outpatient requires patient education and an interdisciplinary approach. Institutions which adopt this recommendation must be prepared to provide adequate outpatient follow-up for these patients.

 

Stroke

• Approximately 21% of patients admitted with acute ischemic stroke have previously diagnosed diabetes
• Undiagnosed diabetes may increase the overall prevalence to > 50%.
• Patients with diabetes who have higher blood glucose values in the days following a cerebral infarction are more likely to exhibit: infarct expansion, cerebral edema, worse short-term outcome.
• At present, there is no evidence that very tight glycemic control for patients suffering ischemic stroke is beneficial in terms of adverse outcomes, therefore we recommend a target of 5.0-11.0 mmol/L for patients with stroke.

Medical ICU

• Results of clinical trials are mixed regarding the benefit of very tight glycemic control. The Leuven protocol targeting glucose levels 4.4-6.1 showed morbidity benefit to those staying in ICU longer than 3 days.
• However the VISEP trial of patients with Sepsis and the NICE-SUGAR trials showed excessive hypoglycaemia, and lack of benefit of very tight control over conventional control for these patients.
• Based on conventional targets in these trials, we recommend targets of 7.0- 10.0 mmol/L.

General Medical Ward

• Based on consensus, we recommend maintaining glucose levels 5.0-11.0 mmol/L with IV, subcutaneous insulin, oral agents or a combination of oral agents with insulin.
• Use of "sliding scale" insulin therapy, although common, treats hyperglycemia after it has occurred. A proactive approach to management with the use of basal, bolus and correction insulin is preferred.
• The dose and regimen of insulin ordered must take into account the patient's usual insulin regimen and the degree of insulin resistance or sensitivity at present.
• Insulin regimens must take into account whether the patient is eating or not, or is receiving enteral/TPN feeds.
• Rapid- or short-acting insulin should be administered pre-meals.
• Basal insulin requirements should be considered in all patients requiring insulin.
• If patients have excellent self-management skills they may be actively involved in their inpatient management was able.

References

1. Hjortuup A, Sorensen C, Dyremose E, et al. Influence of Diabetes Mellitus on Operative Risk. Br J Surg 1985; 72:783-5.
2. Hux JE et al. Institute for Clinical Evaluative Sciences (ICES) Diabetes in Ontario Practice Atlas, 2003
3. Schade D. Surgery and Diabetes. Med Clin N. Am 1988;72:1531-43.
4. Hirsch IB, McGill JB. Role of insulin in management of surgical patients with diabetes mellitus. Diabetes Care 1990;13:980-91.
5. Hill Golden S, Peart-Vigilance C, Koa WH, Brancati FL. Perioperative glycemic control and the risk of infectious complications in a cohort of adults with diabetes. Diabetes Care 1999;22:1408-14.
6. Van den Berghe G, et al. Intensive insulin therapy in critically ill patients. NEJM 2001;345:1359-67.
7. Malmberg K, Ryden L, Efendic S et al. Randomized trial of insulin-glucose infusion followed by subcutaneous insulin treatment in diabetic patients with acute myocardial infarction (DIGAMI study): effects on mortality at 1 year. J Am Coll Cardiol 1995;26:57-65.
8. Malmberg K. Prospective randomised study of intensive insulin treatment on the long term survival after acute myocardial infarction in patients with diabetes mellitus. BMJ 1997;314:1512-5.
9. Malmberg K, et al. Intense metabolic control by means of insulin in patients with diabetes and acute myocardial infarction (DIGAMI 2). Euro Heart J. 2005;26:650-661
10. Zerr K, et al. Glucose control lowers the risk of would infection in diabetes after open heart operations. Ann Thoracic Surg 1997;63:356-61.
11. Lazar HL, et al. Tight glycemic control in diabetic coronary artery bypass graft patients improves perioperative outcomes and decreases recurrent ischemic events. Circulation 2004;109:1497-1502.
12. The NICE-SUGAR Study Investigators. Intensive verses conventional glucose control in critically ill patients.NEJM 2009;360:1283-1297.
13. Brunkhorst F, et al. Intensive insulin therapy and pentastarch resuscitation in severe sepsis. New Engl J Med. 2008;358:125-39.
14. van den Berghe G, et al. Intensive insulin therapy in the medical ICE. New Engl J Med. 2006;354:449-61
15. Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2008 clinical practice guidelines for the prevention and management of diabetes in Canada. Can J Diabetes 2008; 32 (suppl 1):S71-76.