Perioperative Management of Diabetic Patient

Introduction

Globally, as of 2010, an estimated 285 million people had diabetes, with type 2 making up about 90% of the cases. In 2013, according to International Diabetes Federation, an estimated 381 million people had diabetes. The increase incidence in developing countries follows the trend of urbanization and lifestyle changes, perhaps most importantly a “Western-style” diet. In April 2014, the National Institutes of Health (NIH) reported that the percentage of people with diabetes in the United States doubled since 1998.Thanks to Frederick Banting who, along with Charles Best, discovered insulin in 1922, which enabled us to manage diabetes periopratively.

Patients with diabetes are more likely to undergo surgery than are people without diabetes. Maintaining glycemic control in subjects with diabetes presents a challenging problem during the perioperative period. The higher morbidity and mortality relates in part to the heightened incidence of coronary heart disease, hypertension, renal insufficiency, and increased rates of postoperative complications. But advances in perioperative management have enabled diabetic patients to undergo complex surgery with increasing safety.

Pathophysiology of hyperglycemia during trauma and surgical stress

1. The stress of surgery and anesthesia results in increased secretion of counter regulatory hormones (catecholamines, cortisol, glucagon, and growth hormone) and excessive release of inflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-6 and interleukin-1.
2. The counter regulatory response results in a number of alterations in carbohydrate metabolism, including insulin resistance, increased hepatic glucose production, impaired peripheral glucose utilization, and relative insulin deficiency.
3. Increased counterregulatory hormones during stress also lead to enhanced lipolysis and increased free fatty acid (FFA) concentration.

Preoperative Evaluation-

Diabetes Mellitus is a condition which has multi-organ involvement.

The evaluation is oriented to identifying underlying cardiac, pulmonary and renal disease, electrolyte disturbances, presence of macrovascular and microvascular, neuropathic complications, as well as the assessment of antecedent glycemic control.

Cardiac functions

Hypertension and cardiovascular disease is inordinately common so assumes high priority. History of myocardial infarction, unstable angina, poor physical inability, cerebral vascular episodes should be taken. Even asymptomatic diabetic patients have an incidence of acute ischemic events. A low threshold for cardiac testing has been recommended in diabetics, especially those over 50 years of age, with obesity, physical inactivity, hypertension, albuminuria, dyslipidemia, and chronically elevated glucose (>200 mg/dL) and HbA1C levels (> 7%).The preoperative detection of CAD in diabetic patients is difficult. The standard baseline electrocardiogram has a value of only 25% for predicting cardiac events. Asymptomatic diabetic patients with multiple risk factors should be investigated by stress testing if they have a low-functional capacity or if they are to undergo major or vascular surgery. The positive predictive value of all stress tests is modest (20–30%); however, their negative predictive value is excellent (95–100%). Stress tests with dipyridamole-thallium scintigraphy and dobutamine echocardiography are dynamic investigations with better diagnostic accuracy.

Autonomic Functions-

Autonomic neuropathy is a major complication of diabetes, characterized by degeneration of afferent and efferent fibers of the sympathetic and parasympathetic nerves of the heart and peripheral vasculature.

The presence of resting tachycardia, postural hypotension and loss of respiratory heart rate variability should be sought during the examination. Cardiac autonomic neuropathy explains the occurrence of silent myocardial ischemia and the impaired cardiovascular response to exercise and stress and may predispose to cardiovascular complications and perioperative hypotension, specially post induction. Besides cardiac complications, autonomic neuropathy may increase the risk of perioperative complications by decreasing esophageal motility and causing gastroparesis that may lead to vomiting and aspiration of gastric content and by increasing the risk of urinary tract infection in the presence of neurogenic bladder.

Renal functions-

Renal failure is the most common major complication in the postoperative period and is associated with increased morbidity,mortality, Risk factors for postoperative renal dysfunction include advanced age, type 1 diabetes mellitus, preoperative hyperglycemia, a history of moderate to severe congestive heart failure, a previous coronary artery bypass graft, or preexisting renal disease (as manifested by an elevated serum creatinine level).This risk approximately doubles with one preoperative risk factor and quadruples with two risk factors.

Laboratory tests- (Specifically important in DM patients)

Hb A1c, Blood glucose (Fasting, Postmeal), Serum creatinine levels, serum electrolyte levels, ECG, ECHO, Stess tests, preop angiography &/or angiography where ever indicted.

Urine analysis to rule out infections, proteinuria and ketones as albuminuria is associated with greater risk of developing acute renal failure in post op period.

Approaches to Management

General Principles-

The patient’s diabetes care provider should be involved in the management of their patients’ diabetes peri-operatively.
Diabetes should be well controlled prior to elective surgery.
Avoid insulin deficiency, and anticipate increased insulin requirements.
Patients must be given clear written instructions concerning the management of their diabetes both pre- and post-operatively (including medication adjustments) prior to surgery.
Patients with diabetes should be on the morning list, preferably first on the list.
These guidelines may need to be individually modified depending on the patient’s circumstances

Targets for therapy-

• Postpone elective surgery if possible if glycaemic control is poor (HbA1c ≥ 9%).
• BGL should be kept between 5 – 10mmol/l (110-180mg/dL)during the peri-operative period
• For critically ill patients who require admission to the intensive care unit post-operatively, a “tighter” BGL target (eg 4.4-6.1 mmol/L) may not convey any greater benefit,so BGL between 5 – 10mmol/l (110-180mg/dL) is acceptable.
• Hypoglycaemia must be avoided.
• Marked hyperglycaemia should be prevented as it may lead to dehydration and electrolyte abnormalities,impair wound healing and predispose to infection or diabetic ketoacidosis in patient with type I DM

Perioperative management of patients with diabetes

I) Minor surgery in DM2 patients not treated with insulin

• Hold oral agents the day of surgery.
  Patients on Oral AHG Medication (without insulin)
  Major Surgery
  • Stop AHG medication on the day of surgery.
  • Restart AHG medication when patients are able to resume normal meals (except possibly Metformin).
  • Commence an I-G infusion if the BGL >10 mmol/L (180mg/dl); if surgery is prolonged and complicated; or if the patient is usually treated with more than one oral AHG agent.
  • Subcutaneous insulin may be required post-operatively
• Patients with “fair” metabolic control (fasting blood glucose <180 mg/dL)—cover with regular insulin or rapid-acting (lispro, aspart, glulisine) insulin as needed
• Patients with “poor” metabolic control (fasting blood glucose >180 mg/dL)—start continuous insulin infusion.
• Goals: avoid excessive hyperglycemia (blood glucose>180 mg/dL) and hypoglycemia (blood glucose <80 mg/dL) II) Minor surgery in DM1 and DM2 patients treated with insulin
• Hold oral agents (if treated with combination therapy) the day of surgery
• Patients in “fair” metabolic control (fasting blood glucose<180 mg/dL):
  – Give half of intermediate-acting insulin (NPH) the morning of the surgery
  – While NPO, infuse dextrose 5% saline plus KCl (10-20 mEq/L) at 100 mL/hour
  – Check blood glucose every 4 to 6 hours while NPO and supplement with short-acting insulin
  – Patient treated with basal (glargine) insulin should receive their usual basal insulin dose. Similarly, patients treated with continuous insulin infusion therapy (insulin pump) should receive their usual basal infusion rate
  – Restart preadmission insulin therapy once food intake is tolerated
• Patients in “poor’ control (fasting blood glucose> 180 mg/dL) – start continuous insulin infusion III) Major surgery in DM1 and DM2 patients treated with insulin
• Hold oral agents the day of surgery
• Start continuous insulin infusion prior to surgery and continue during perioperative period.
• Goals: Maintain blood glucose <180 mg/dL during surgery, and blood glucose between 80 to 120mg/dL during the perioperative period in the surgical intensive care unit. Start subcutaneous insulin two hours prior to discontinuation of insulin infusion. In non-ICU settings, avoid excessive hyperglycemia (blood glucose>180 mg/dL) and hypoglycemia (blood glucose < 80 mg/dL).

Supplemental sliding scale insulin

This is a practically useful tool to manage blood sugar peri-operatively

• Type of insulin: regular or rapid-acting insulin (lispro, aspart, glulisine) to be given before each meal and at bedtime.
• Each column represents the number of units of insulin to be added to scheduled insulin dose.
  – “Sensitive” column: elderly, cachectic, renal and liver failure, and patients with poor oral intake or NPO.
  – “Usual” column: for most patients who are expected to eat all or most of their meals.
  – “Insulin Resistant” column: for patients not controlled with “usual” column dose, or receiving glucocorticoids, obesity (BMI >30 kg/m2), or patients with diabetes receiving> 80 units/day of insulin.

Major Surgery management

IV infusion of insulin is the standard therapy for the perioperative management of diabetes, especially in type 1 diabetic patients and patients with type 2 diabetes undergoing major procedures.
Two main methods of insulin delivery have been used either combining insulin with glucose and potassium in the same bag (GIK regimen) or giving insulin separately with an infusion pump.

I) The GIK is initiated

at a rate of 100 mL/h in a solution of 500 mL of 10% dextrose, 10 mmol of potassium, and 15 U of insulin. Adjustments in the insulin dose are made in 5 U increments according to blood glucose measurements performed at least every 2 hours. Potassium is added to prevent hypokalemia and is monitored at 6-hour intervals. The combined GIK infusion is efficient, safe, and effective but does not permit selective adjustment of insulin delivery without changing the bag..

II)Continuous insulin infusion (CII) protocol

I) Initiating continuous insulin infusion (CII):

• Prepare solution: 1 unit (U) per 1 mL of 0.9% normal saline.
• Start continuous insulin infusion (CII) when blood glucose level >140 mg/dL (x 2). Patients with known diabetes treated with insulin can start CII when blood glucose ≥70 mg/dL.
• Initial rate: divide blood glucose level (mg/dL) by 100, then round to nearest 0.5 U

II) Insulin infusion rate change:

Blood Glucose (mg/dL) instructions:

III) Patient monitoring:

• Check capillary blood glucose every hour until it is within goal range for 2 hours, and then decrease to every 2 hours.
• Hourly monitoring may be indicated for critically ill patients even if they have stable blood glucose. If a patient is eating, hourly blood glucose monitoring is necessary for at least 3 hours after eating.
• Decrease insulin infusion rate by 50% if nutritional therapy (e.g. total parenteral nutrition or tube feeds) are discontinued or significantly reduced.

IV) Treatment of Hypoglycemia (BG <- 60 mg/dL)

• Turn off insulin infusion.
• Blood glucose level 40–60 mg/dL: give 12.5 g (25 mL) IV bolus of dextrose 50% solution. For blood glucose< 40 mg/dL, or if a patient is not awake, give 25 g (50 mL) IV bolus of dextrose 50% solution.
• Recheck BG every 20 minutes, repeat 25 mL of 50% dextrose IV if BG <60mg/dL.
• Restart infusion once BG is >80 mg/dL.

V) Notify the physician:

• For any blood glucose change greater than 100 mg/dL in one hour.
• For blood glucose <40 mg or>360 mg/dL.
• For hypoglycemia which has not resolved within 20 min of administering 50 mL of 50% dextrose.

Special Situations

1. BOWEL PREPARATION
   • The dose of insulin should be reduced during the period of bowel preparation.
   • Short-acting insulin and oral AHG medication should be withheld.
   • Clear fluids should contain glucose, and diet drinks are consumed if the BGL is elevated.
   • Patients with unstable diabetes should be admitted to hospital during the period of bowel preparation and an I-G infusion commenced
2. Cardiopulmonary bypass
   These situations presents considerable challenges to diabetes management because of stress of procedure and dextrose solutions used for priming the perfusion pumps.
3. Organ transplants is similarly challenging due to the use of immunosuppressant agents and glucocorticosteroids.
4. Neurosurgical procedures
   These are better managed by Continuous Insulin Infusion method.

Effect of Anaesthesia on glycemic response

The type of anesthesia may influence the hyperglycemic response during surgery. General anesthesia has been shown to result in higher blood glucose concentration than local and epidural analgesia. Circulating catecholamines, cortisol, and glucagon concentration are higher in patients undergoing general anesthesia. Volatile anesthetic agents inhibit insulin secretion and increase hepatic glucose production.

Epidural analgesia has a minimal effect on carbohydrate metabolism and levels of counter regulatory hormones are not significantly elevated.
The combination of regional and general anaesthesia techniques is best over general anaesthesia alone.
It should be noted that the reduced hyperglycemia associated with epidural analgesia is strictly limited to the operative period; afterwards, there is no difference in glycemic control.

Other Anaesthesia considerations-

• Avoid potentially nephrotoxic drugs, whenever microalbuminuria is evident.
• In presence of significant autonomic dysfunction, impaired response to physiologic stress is there, so spinal or extradural is avoided.
• Patient with abnormal prayer sign may have stiff joint syndrome; difficult intubation.
• Adequate glucose should be provided to prevent catabolism, starvation ketosis, and insulin-induced hypoglycemia. The physiologic amount of glucose required to prevent catabolism in the average nondiabetic adult is 120 g/d (or 5 g/h). With preoperative fasting, surgical stress, and ongoing insulin therapy, the caloric requirement in most diabetic patients averages 5 to 10 g/h of glucose. This can be given as 5% or 10% dextrose. An infusion rate of 100 mL/h with 5% dextrose delivers 5 g/h of glucose. If fluid restriction is necessary, the more concentrated 10% dextrose can be used. Fluids containing lactate (ie, Ringer lactate, Hartmann solution) cause exacerbation of hyperglycemia, so better avoided.

THE POSTOPERATIVE PERIOD

• Insulin-glucose infusions should be continued until the patients can resume an adequate diet.
• I-G infusions should ideally be stopped after breakfast, and a dose of subcutaneous insulin (or oral AHG) is given before breakfast.
• Hyperglycaemia detected post-operatively in patients not previously known to have diabetes should be managed as if diabetes was present, and the diagnosis of diabetes reconsidered once the patient has recovered from their surgery.
• Diabetes medication requirements may be increased (or occasionally decreased) in the post-operative period, and frequent BGL monitoring is therefore essential.
• Diabetes management expertise must be available for the post-operative management of glycaemic instability.

CONCLUSION

In conclusion, maintaining good glycaemic control during the peri-operative period results in improved outcomes following surgery. In order to keep blood glucose levels within the target range, diabetes medications often need to be altered immediately before and following surgical procedures. There may be great individual variation in the impact of surgery and the adjustments to therapy required, depending on the pre-existing diabetes status of the patient, the nature of the surgery and the presence of post-operative complications. Therefore, management of patients with diabetes in the peri-operative period is complex, and requires a close working relationship and effective communication between surgeons, physicians and anaesthetists.

References

1. An update on peri-operative management of Diabetes.
   Scott J.Jacober;James R Sowers:Arch Intern Med/Vol 159,Nov 1999
2. Perioperative glucose control in diabetic or nondiabetic patient.
   Dawn D Smiley,Guillermo E Umpierrez:Southern Medical association,2006
3. Endocrine, The Medicine Consult Handbook, 2011.
4. Peri-operative Diabetes management guidelines, Australian Diabetes
   Society 2012.
5. Clinical Anaesthesia, Paul Barash, 6th Edition.
6. Anaesthesia, Ronald Miller, 7th Edition.