Perioperative Management

Diabetes increases the requirements of surgery as well as perioperative morbidity and mortality. Careful preoperative evaluation and treatment of cardiac and renal diseases, intensive intraoperative and postoperative management are essential to optimize the best outcome. Stress hyperglycemia in response to surgery, osmotic diuresis and hypoinsulinemia can lead to life threatening complications like ketoacidosis or hyperglycemic hyperosmolar syndrome. Wound healing is impaired by hyperglycemia and chance of postoperative wound infection is more in diabetics. Therefore aseptic precautions must be taken. Adequate insulin, glucose, fluid and electrolytes should be provided for good metabolic control. Though some current study reveals that oral hypoglycemic agents can be used for the effective management of perioperative diabetes; the adverse effects of newly introduced agents need more clinical observations. Subcutaneous administration of insulin as in Sliding Scale may be a less preferable method, because of unreliable absorption and unpredictable blood glucose. Intravenous administration of rapid onset soluble (short acting) insulin as in Alberti (GIK) regimen, is safe and effective method controlling perioperative hyperglycemia. Patient with type 1 diabetes needs frequent monitoring of glucose, electrolytes and acid-base balance as chance of high hyperglycemia and ketoacidosis is more. In case of emergency surgery assessment for diabetic ketoacidosis (DKA) and meticulous management is essential. Postoperative pain and hyperglycemia should be treated carefully to avoid complications.


Introduction
The global incidence of diabetes mellitus is rising and the number of affected people is projected to exceed 300 million by the year 2025. 1 The prevalence of 2.8% in 2000 is estimated to be 4.4% in 2030. 2 Diabetes mellitus leads to many systemic diseases that require surgical treatment.It is observed that diabetic patients undergo surgical procedures at a higher rate than nondiabetic patients. 3,46][7][8][9] The risk of perioperative complication associated with diabetes mellitus is increased.The mortality rate in diabetic patients undergoing surgery is also increased. 10,11ong term control of blood glucose reduces the rate and severity of complications.But even short term glycemic control in hospitalized patients can significantly lower morbidity and mortality.Aim of this review is to aware physicians to control perioperative diabetes meticulously to reduce complications.

Glucose Physiology 12
Liver and pancreas play the major role in glucose metabolism.Glucose metabolism occurs to a laser extent in peripheral tissues.Liver uptakes glucose and stores as glycogen and performs gluconeogenesis as well as glycogenolysis.The catabolic hormones namely epinephrine, glucocoticoids and growth hormone raise blood glucose concentration and in response to the raised blood glucose level the pancreatic beta cell secretes insulin, which lowers blood glucose concentration. 12[15][16][17][18][19][20][21] Hyperglycemic patients are susceptible to develop infection as host defenses against infection is inhibited.Hyperglycemia also impairs wound healing through its harmful effects on collagen formation and decreases wound tensile strength.Healing at anastomotic site is severely impaired if blood glucose is not controlled.As the incidence of coronary artery disease is increased in diabetics, the risk of ischaemic heart disease, cerebrovascular infarction and renal ischaemia is increased.In patients with type 2 diabetes chance of hyperglycemic hyperosmolar non-ketotic states (HONKS) is more than that of diabetic ketoacidosis and hyperosmolar non ketotic coma (HONC) that may carry higher mortality.Hyperglycemia can also induce insulin resistance through glucose toxicity.

A. Preoperative evaluation 22
The status of the patient's diabetes and surgical risk factors are to be evaluated first.The method of anesthesia to be used, the characteristics of the procedure to be performed, and laboratory values are also important.In case of elective surgery, potential problems should be identified, treated, and stabilized before surgery.Assessment of metabolic control and any diabetes associated complications, including cardiovascular disease, autonomic neuropathy and nephropathy is the main target of preoperative evaluation.Silent myocardial ischemia occurs relatively often in patients with diabetes.So all diabetic patients should be evaluated at least by ECG but echocardiography and stress test are often justified if there is suspicion for cardiovascular disease.Patients with diabetic autonomic neuropathy may develop perioperative hypotension, so resting tachycardia, peripheral neuropathy and orthostatic hypotension should be sought.Serum creatinine and creatinine clearance rate (CCR) should be measured to exclude the possibility of diabetic nephropathy.[25][26][27][28][29] -Diabetic patients should be the first case in the morning to minimize the starvation period.

B. Anesthetic consideration
-Most stable analgesia and anesthesia should be provided to limit surgical stress induced hyperglycemia.
-Judicious analgesics should be used.
-Both regional and general anaesthesia may be given in diabetics.
-Regional anesthesia blunts the stress response to surgery.
-Spinal or epidural anesthesia modulates catecholamine secretion preventing hyperglycemia and ketoacidosis.This effect could continue in the postoperative period.
-Aseptic precautions and sterile techniques must be maintained both for anesthesia and surgery.
-In diabetic autonomic neuropathy, profound hypotension may occur.So regarding hemodynamic stability ideal anesthetics should be used.
-Ability of lipid metabolism is decreased in diabetic patient, so drugs in lipid imulsion (e.g.Propofol) should be used cautiously.Single dose of Propofol is almost safe, but prolonged infusions for sedation in intensive care may increase the risk of hyperlipidemia.
-May have difficult airway (stiff joint syndrome).So difficult intubation protocol should be exercised and a skilled anesthetist should handle the case.
-Severe hypoglycemia can delay recovery from general anesthesia as consciousness is impaired.
-Beta blocker drugs increase the blood glucose level in those who don't have diabetes but may worsen sugar control in those with diabetes and also blunt warning symptoms when hypoglycemia occurs.
-Patients suspected for gastroparesis should receive a prokinetic drug before administration of general anesthesia to decrease the incidence of gastric acid aspiration.
-Maintaining temperature is important as hypothermia can lead to peripheral insulin resistance.
-Ketoacidosis can develop during the periods of major stress in patients with type 1 diabetes.So these patients should be monitored by arterial blood gas analysis during and after major surgery and managed accordingly.

C. Control of blood glucose
As diabetic patients are more susceptible to develop numerous perioperative complications, close monitoring is imperative to control blood glucose and prevent hypoglycemia and very high hyperglycemia.Though some current studies suggested that oral hypoglycemic agents can be used for the effective management of perioperative diabetes; it is to be considered that the adverse effects of newly introduced agents need more clinical observations.Subcutaneous administration of insulin as in Sliding Scale may be a less preferable method, because of unreliable absorption and unpredictable blood glucose concentration.Intravenous administration of rapid onset soluble (short acting) insulin as in Glucose-insulinpotassium (GIK) systems (Alberti regimen), is safe and effective method controlling perioperative hyperglycemia. 30,31 should provide adequate insulin to the patient to counteract the catabolic process that develops in response to surgery.Glucose needs to be provided to meet the increased metabolic needs caused by surgical stress as well as the basal metabolic requirements.Major surgery and emergency surgery especially trauma or surgery related to infective process requires more concentration.Treatment regimen depends upon type of diabetes, usual treatment and extent of surgery.
Patients with type 2 diabetes on diet alone can be managed without insulin. 32Close observation including hourly glucose measurement is essential in operation theatre.If the blood glucose rises >8.0 mmol/L, Alberti (GIK) regimen should be considered.
If type 2 diabetic patient on oral hypoglycemic agent (OHA) comes for major surgery, it is better to stop OHA 48 hours before surgery and convert to short acting insulin. 23Alberti (GIK) regimen is relatively safe in this situation because they provide insulin and glucose in the same solution. 33Metformin needs not to be stopped, as risk of lactic acidosis is extremely low. 34Morning dose of metformin should be omitted.
In case of minor surgery OHA should be omitted on the day of surgery and close observation is needed.If blood glucose rises above 8.6mmol/L Alberti regimen should be adopted.In such cases continuous i.v.infusion of insulin is superior to intermittent subcutaneous bolus or intravenous boluses. 35tients with type 1 diabetes should stop taking long acting insulin at least 24 hours before surgery.Intermediate acting insulin may be continued until the evening before surgery. 36Every patient of type 1 diabetes undergoing surgery should be managed with insulin.The glucose-insulin infusion is the satisfactory method of avoiding harmful metabolic consequences of starvation and surgical stress.GIK infusion is a simple reliable way for controlling the blood glucose and it should be started in preoperative period.Blood glucose level should be measured frequently and accurately throughout the perioperative period.Glucose level should be kept between 6.6 to 9.9 mmol/L. 37 The Alberti GIK regimen for perioperative glycemic control: 38 A solution of 500 ml of 10% glucose containing 15 U of rapid onset soluble insulin with 10 mmol KCl is started at a rate of 100 ml/hr (i.e. 3 U/hr).Blood glucose is checked 2 hourly and insulin is adjusted according to results (Table I).

D. Glucose, insulin, fluid and electrolyte management
Glucose, insulin, potassium and fluids are the factors that need to be considered meticulously.
Sufficient glucose is to be given to prevent hypoglycemia.It is recommend that 5-10 gm of dextrose is given per hour (70 kg patient) in the form of 5% or 10% dextrose in aqua. 39,40An easy way is to give 0.1gm/kg/hr in adult patient and 0.3 gm/kg/hr in pediatric patients to prevent hypoglycemia.Normal saline (0.9% sodium chloride) may be needed to prevent hyponatremia for long term infusions.
The beta cells in the pancreas secret insulin in response to glucose concentrations.Even the most sophisticated artificial insulin delivery systems cannot replicate this response.During surgery alterations in blood flow makes the absorption of insulin more unpredictable.Soluble rapid onset insulin is used in perioperative infusions due to its short half life (5 min) and duration of action (<20 min).Usually 1 unit of regular insulin is required to reduce blood glucose level 25 to 30 mg/dl except in some cases like liver disease, obesity, severe infection and steroid therapy where insulin requirements are increased.Insulin can be given either with glucose solution or by a separate syringe pump. 41rum potassium levels should be measured at least before and after surgery.Several factors can influence serum potassium levels during surgery.Insulin stimulates the uptake of potassium into cells while dehydration and hyperglycemia can move potassium out of the cells and into the blood.Acidosis can result in hyperkalemia due to exchange of intracellular potassium for extracellular hydrogen ions.In diabetics with normal renal function and normal serum potassium levels, 10 to 15 mEq of potassium should be added per 500 ml of 10% glucose containing fluid. 38,42This should be adjusted according to plasma concentrations of potassium.
Any other fluids needed intraoperatively should be non-glucose containing like 0.9% sodium chloride solution.It is better to avoid Ringer's lactate solution, as lactate is gluconeogenic precursor and is rapidly metabolized resulting in higher blood glucose concentration.But the role of lactate to the acid-base disturbance is generally small. 43

E. Emergency surgery
Usually most of the diabetic patient who need emergency surgery will not be in good metabolic control at that time and may present with diabetic ketoacidosis (in type 1 diabetic patients) or hyperglycemic hyperosmolar syndrome (in type 2 diabetic patients). 37Except some life threatening surgical conditions (torrential and uncontrolled haemorrhage or acutely compromised airway) patients always require full stabilization before anesthesia and surgery. 37To optimize metabolic status surgery should be delayed for 4-6 hours, if possible. 41

F. Post operative management
No specific protocol is recommended for glycemic control in postoperative care unit or intensive care unit (ICU). 44Patient treated with GIK infusion intraoperatively, should be treated similarly in the postoperative period.Blood glucose level should be measured hourly and insulin dose should be adjusted according to a "glucose-feedback" formula.45The patient must start taking food as soon as possible.If the blood sugar is near normal or normal, preoperative drug regimen should be started.Analgesia should be maintained meticulously to reduce stress. 46

Summary
Though opinions differ regarding management, it is proved over recent years that proper preoperative evaluation, treatment of complications and good glycemic as well as metabolic control improve the outcome and reduce perioperative morbidity and mortality in diabetic patients.

Table I :
Perioperative glycemic controlContinue to adjust in 5-U steps as necessary.