© American Diabetes Association ®, Inc., 2002 Management of Diabetes Mellitus in Surgical Patients
In Brief Diabetes is associated with increased requirement for surgical procedures and increased postoperative morbidity and mortality. The stress response to surgery and the resultant hyperglycemia, osmotic diuresis, and hypoinsulinemia can lead to perioperative ketoacidosis or hyperosmolar syndrome. Hyperglycemia impairs leukocyte function and wound healing. The management goal is to optimize metabolic control through close monitoring, adequate fluid and caloric repletion, and judicious use of insulin.
Patients with diabetes undergo surgical procedures at a higher rate than do nondiabetic people.1,2 Major surgical operations require a period of fasting during which oral antidiabetic medications cannot be used. The stress of surgery itself results in metabolic perturbations that alter glucose homeostasis, and persistent hyperglycemia is a risk factor for endothelial dysfunction,3 postoperative sepsis,4 impaired wound healing,5,6 and cerebral ischemia.7 The stress response itself may precipitate diabetic crises (diabetic ketoacidosis [DKA], hyperglycemic hyperosmolar syndrome [HHS]) during surgery or postoperatively, with negative prognostic consequences.8,9 HHS is a well known postoperative complication following certain procedures, including cardiac bypass surgery, where it is associated with 42% mortality.9,10 Furthermore, gastrointestinal instability provoked by anesthesia, medications, and stress-related vagal overlay can lead to nausea, vomiting, and dehydration. This compounds the volume contraction that may already be present from the osmotic diuresis induced by hyperglycemia, thereby increasing the risk for ischemic events and acute renal failure. Subtle to gross deficits in key electrolytes (principally potassium, but also magnesium) may pose an arrhythmogenic risk, which often is superimposed on a milieu of endemic coronary artery disease in middle-aged or older people with diabetes. It is therefore imperative that careful attention be paid to the metabolic status of people with diabetes undergoing surgical procedures. Elective surgery in people with uncontrolled diabetes should preferably be scheduled after acceptable glycemic control has been achieved. Admission to the hospital 12 days before a scheduled surgery is advisable for such patients. Even emergency surgery should be delayed, whenever feasible, to allow stabilization of patients in diabetic crises. The actual treatment recommendations for a given patient should be individualized, based on diabetes classification, usual diabetes regimen, state of glycemic control, nature and extent of surgical procedure, and available expertise. Some general rules can be applied, however. Whenever possible, ketoacidosis, hyperosmolar state, and electrolyte derangements should be searched for and corrected preoperatively, and the surgery itself should be scheduled early in the day, to avoid protracted fasting.
Anesthesia and surgery cause a stereotypical metabolic stress response that could overwhelm homeostatic mechanisms in patients with pre-existing abnormalities of glucose metabolism. The invariant features of the metabolic stress response include release of the catabolic hormones epinephrine, norepinephrine, cortisol, glucagons, and growth hormone1116 and inhibition of insulin secretion and action.1719
Anti-Insulin Effects of Surgical Stress These anti-insulin effects of the metabolic stress response essentially reverse the physiological anabolic and anti-catabolic actions of insulin. The important anabolic actions of insulin that may be reversed or attenuated during the stress of surgery include: 1) stimulation of glucose uptake and glycogen storage, 2) stimulation of amino acid uptake and protein synthesis by skeletal muscle, 3) stimulation of fatty acid synthesis in the liver and storage in adipocytes, and 4) renal sodium reabsorption and intravascular volume preservation. The anti-catabolic effects of insulin include: 1) inhibition of hepatic glycogen breakdown, 2) inhibition of gluconeogenesis, 3) inhibition of lipolysis, 4) inhibition of fatty acid oxidation and ketone body formation, and 5) inhibition of proteolysis and amino acid oxidation. Thus, inhibition of insulin secretion and action shifts the perioperative milieu toward hypercatabolism through a variety of mechanisms.
Direct Catabolic Effects of Stress Hormones These effects predispose to severe hyperglycemia, which is further exacerbated by the stimulatory effect of epinephrine and norepinephrine on glucagon secretion. Other catabolic effects of catecholamines include stimulation of lipolysis and ketogenesis. Epinephrine increases adipocyte cAMP levels, leading to phosphorylation and activation of hormone-sensitive lipase. The activated hormone-sensitive lipase promotes lipolysis and release of free fatty acids into the circulation. Glucagon, whose levels are augmented by catecholamines, exerts catabolic effects similar to those of the catecholamines: stimulation of hepatic glucose production and ketogenesis and inhibition of insulin action in peripheral tissues. Growth hormone and glucocorticoids potentiate the catabolic effects of catecholamines and glucagon. Glucocorticoids increase hepatic glucose production21,22 and induce lipolysis and negative nitrogen balance by stimulating proteolysis. The products of lipolysis and proteolysis (e.g., free fatty acids, glycerol, alanine, glutamine) provide substrates for increased gluconeogenesis by the liver. Clearly, the combination of relative hypoinsulinemia, insulin resistance, and excessive catabolism from the action of counterregulatory hormones is a serious threat to glucose homeostasis in all patients with diabetes, particularly those whose preoperative metabolic control is less than perfect. The logical conclusion is that insulin therapy will be needed perioperatively in the majority of patients with diabetes undergoing surgery.
Operationally, all patients with type 1 diabetes undergoing minor or major surgery and patients with type 2 diabetes undergoing major surgery are considered appropriate candidates for intensive perioperative diabetes management. The management approach in these categories of patients always includes insulin therapy in combination with dextrose and potassium infusion. Major surgery is defined as one requiring general anesthesia of 1 h. Type 2 diabetic patients undergoing minor surgery are managed based on their usual diabetes regimen, their state of glycemic control, the nature and extent of the surgical procedure, and available expertise.
Patients Managed With Diet Alone
Patients Treated With Oral Antidiabetic Agents At a minimum, blood glucose should be monitored before and immediately after surgery in all patients. Those undergoing extensive procedures should have hourly glucose monitoring during and immediately following surgery. Bedside capillary blood glucose meters are adequate for these monitoring requirements. However, extremely high or low values should immediately be repeated before instituting remedial action, and a simultaneous blood specimen should be sent for laboratory corroboration.
For minor surgery, perioperative hyperglycemia (>200 mg/dl) can be managed with small subcutaneous doses (410 units) of short-acting insulin. Care must be taken to avoid hypoglycemia. After minor procedures, most usual antidiabetic medications can be restarted once patients start eating. Patients treated with metformin should withhold the drug for
Insulin-Treated Patients
Major surgery The preoperative evaluation should include a thorough physical examination (with particular focus on autonomic neuropathy and cardiac status), measurement of serum electrolytes and creatinine, and urine ketones. The presence of autonomic neuropathy mandates increased surveillance for hypotension, respiratory arrest, and hemodynamic instability during surgery.24 Gross metabolic and electrolyte abnormalities (e.g., hyponatremia, dyskalemia, acidosis) should be corrected before surgery.
Intravenous Insulin, Glucose, Potassium, and Fluids
It is not necessary to add albumin to the insulin infusion to prevent nonspecific adsorption of insulin to the infusion apparatus; flushing Adequate fluids must be administered to maintain intravascular volume. Fluid deficits from osmotic diuresis in poorly controlled diabetes can be considerable. The preferred fluids are normal saline and dextrose in water. Fluids containing lactate (i.e., Ringers lactate, Hartmanns solution) cause exacerbation of hyperglycemia.28
Insulin The combined GIK infusion is efficient, safe, and effective in many patients but does not permit selective adjustment of insulin delivery without changing the bag. The glucose component can be either 5 or 10% dextrose. The latter provides more calories. Regardless of whether separate or combined infusions are given, close monitoring is required to avoid catastrophe during these infusion regimens. A sample regimen for separate insulin infusion is indicated in Table 1. These recommendations must be interpreted flexibly, given the individual variability in insulin requirements and metabolic profiles. In the absence of strict evidence-based guidelines, the consensus approach is to avoid extremes of glycemia (aiming for 120180 mg/dl) and to tailor therapies to individual patients based on feedback from glucose monitoring.
The initial insulin infusion rate can be estimated as between one-half and three-fourths of the patients total daily insulin dose expressed as units/h. Regular insulin, 0.51 unit/h, is an appropriate starting dose for most type 1 diabetic patients. Patients treated with oral antidiabetic agents who require perioperative insulin infusion, as well as insulin-treated type 2 diabetic patients, can be given an initial infusion rate of 12 units/h. An infusion rate of 1 unit/h is obtained by mixing 25 units of regular insulin in 250 ml of normal saline (0.1 unit/ml) and infusing 10 ml/h. Alternatively, 50 units of regular insulin is made up to 50 ml with saline and given by syringe pump at 12 ml/h. Adjustments to the insulin infusion rate are made to maintain blood glucose between 120 and 180 mg/dl. (See Table 1.) The duration of insulin (and dextrose) infusions depends on the clinical status of the patient. The infusions should be continued postoperatively until oral intake is established, after which the usual diabetes treatment can be resumed. It is prudent to give the first subcutaneous dose of insulin 3060 min before disconnecting the intravenous line.
Glucose
The usual range of perioperative blood glucose that clinicians are comfortable with is
Potassium The infusion of insulin and glucose induces an intracellular translocation of potassium, resulting in a risk for hypokalemia. In patients with initially normal serum potassium, potassium chloride, 10 mEq, should be added routinely to each 500 ml of dextrose to maintain normokalemia if renal function is normal. Hyperkalemia (confirmed with repeat measurement and electrocardiogram) and renal insufficiency are contraindications to potassium infusion.
Emergency Surgery By definition, the time of occurrence of these emergencies cannot be predicted, and appropriate surgical care must not be unduly delayed. Nonetheless, particular care must be taken to exclude DKA and other conditions that are likely to be mistaken for surgical emergencies. Many patients with DKA and prominent abdominal symptoms have undergone needless surgical exploration for a nonexistent acute abdominal emergency.29 Functional syndromes due to diabetic autonomic neuropathy of the gastrointestinal tract (gastroparesis, gastroenteropathy, intractable or cyclical vomiting) may mimic anatomical surgical emergencies.30 Similarly, the rare diabetic pseudotabes syndrome, characterized by sharp neuropathic pain along thoracolumbar dermatomes, can be confused with visceral disorders. Patients with pseudotabes typically have pupillary and gait abnormalities from associated cranial and peripheral neuropathy. The initial evaluation of a diabetic patient with a suspected surgical emergency must, therefore, include a thorough medical history and physical examination directed at excluding the aforementioned diagnostic pitfalls. Unfortunately, many patients who require emergency surgery will have suboptimal glycemic control. However, this is not necessarily a contraindication to the timely performance of potentially life-saving surgery. An intravenous access should be secured and immediate blood specimens should be sent for glucose, electrolyte, and acid-base assessment. Gross derangements of volume and electrolytes (e.g. hypokalemia, hypernatremia) should be corrected. Surgery should be delayed, whenever feasible, in patients with DKA, so that the underlying acid-base disorder can be corrected or, at least, ameliorated. Patients with HHS are markedly dehydrated and should be restored quickly to good volume and improved metabolic status before surgery. Blood glucose should be monitored hourly at the bedside, and insulin, glucose, and potassium infusion should be administered, as appropriate, to maintain blood glucose in the 120180 mg/dl range. Serum potassium should be checked frequently (every 24 h), and potassium supplementation should be adjusted to ensure that the patient remains eukalemic throughout surgery and postoperatively.
Therapeutic surgery is a frequent requirement for diabetic patients and in the past has been associated with increased morbidity and mortality. Recent outcomes data are lacking, but it is likely that advances in surgical science, anesthesiology, and intensive care medicine, together with increased awareness and appropriate metabolic intervention, may have improved the perioperative fate of diabetic patients in recent times. Clinicians are encouraged to continue to give careful attention to metabolic control in surgical patients with diabetes.
Samuel Dagogo-Jack, MD, FRCP, is a professor of medicine in the Division of Endocrinology, Diabetes and Metabolism at the University of Tennessee College of Medicine in Memphis. K. George M.M. Alberti, DPhil, PRCP, is president of the Royal College of Physicians in London, U.K. He is a professor of medicine at the University of Newcastle upon Tyne in Newcastle, U.K. and a professor of metabolic medicine at the Imperial College of London.
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