DIABETES MELLITUS AND COMMON PROBLEMS DURING PREOPERATIVE / OPERATIVE AND POST OPERATIVE

DIABETES MELLITUS AND COMMON PROBLEMS DURING PREOPERATIVE / OPERATIVE AND POST OPERATIVE

            Approximate 50% of all diabetic patients will undergo surgery atleast once in their lifetime.  The presence of long term diabetes complications, including amputations, ulcer debridement and renal transplantation and cardiothoracic, peripheral vascular and ophthalmologic procedures. Pathophysiology; several factors that predispose patient with diabetes to metabolic decompensation include the patients insulin reserve, endocrine response to surgical stress, volume status and fasting status.

            During anesthesia and surgery, there is an increase in plasm concentration of contraregularoty harmones i.e., glucogon, catecholamine and cortisol and growth hormone.  Increase secretion of these hormones leads to a marked increased in hepatic glucose production, a decrease in insulin mediated glucose uptake, increased lipolysis and elevated levels of NEFA and decreased insulin secretion.

            In nondiabetic, elevation in blood glucose into range of 150-200 mg% associated with major surgery.  Perioperative complication in patients with diabetes include

Ø      Myocardial infarction

Ø      Cerebro Vascular Accident

Ø      Fluid and Electrolyte abnormalities

Ø      Hemodynamic abnormalities during anaesthesia

Ø      Impared healing

Ø      Infection of surgical wounds

            Depending on surgical procedures and its duration, life support measures and instrumentation the type of anesthesia and anesthetic agent used, cardiac output and peripheral vascular resistance will temporarily change.  This lead to BP and HR Changes.

            Autonomic neuropathy can cause severe hypotension during the induction of anaesthesia, and its presence should be evaluated before any procedures involving spinal / General Anesthesia.

            Intravascular and Extravascular fluid status will influence the sudden shifts in volume status and electrolytic changes experienced during the acute stress associated with surgery.

            Hyperglycemia, whether chronic / acute is almost always associated with intravascular fluid depletion.

            Diabetic nephropathy, with or without proteinuria makes fluid and electrolyte management difficult and use of I.V. fluids, vasopressors, vasodilaters and diuretics must be carefully planned.

            Chronic hyperglycemia associated with delayed; wound healing as a consequence of inadequate collagen repair and remodeling.  Impaired leukocyte chemotaxis and defective immune defence mechanism infection at surgical sites common with underlying poor nutrition.

Evaluation of patient with diabetes before surgery

1. Metabolic control

            Chronic hyperglycemia frequently associated with dehydration can be accompanied by electrolyte abnormalities, NA and K loss, and by intravascular volume depletion with subsequent hemodynamic imbalance.  Admission to hospital to optimize metabolic control 12-16 hrs before elective procedures.

            In patient with severe metabolic derangement (DKA and HONK) who need urgent surgical intervention 6-8 hrs of intensive treatment usually improves general condition of the patient increased protein and calorie intake improve collagen formation and healing.

            Specific nutritional needs addressed in COPD or CRF.

2. Cardiovascular status

            Long standing diabetes is often accompanied by arterial hypertension and dyslipidemia, increasing risk of atherosclerosis, leading to ischemia, myocardial infarction, cerebrovascular accidents during perioperative period.

            Recent cardiovascular history, physical examination and electrocardiographic findings generally provide sufficient information to determine risk.  Patient receiving b-blockers may develop hypoglycemia without warning symptoms should be monitored accordingly.  Diabetic patients have increased thrombotic risk.  Antithrombitic therapy with LMWH, antiembolic graduated pressure stockings and ambulation should be considered.

            The use of vasopressors for the treatment of severe hypotension associated with sepsis or extreme intravascular volume loss has been associated with remarkable peripheral vasoconstriction.  Patients with poor peripheral pulses and who require high doses of vasopressor during the course of a critical illness are at risk of gangrene of the digits.

3. Neurological status

            Disordered GI motility may increase the risk of aspiration.  General anesthesis may cause nausea and vomiting.  Bladder dysfunction may lead to urinary retention and subsequent obstructive uropathy and fluid over load.

            Therefore if a patient has evidence of either gastrointestinal dysmotility or bladder dysfunction with the use of antiemetic and narcotic analgesic agents, careful monitoring of fluid intake and urinary output should be addressed before and after surgery. The anesthetist should be alerted to the presence of orthostatic blood pressure changes associated with advanced neuropathy to predict possible hemodynamic changes during anesthetic induction.

4. Renal Function

            Measurement of BUN, serum creatinine, serum electrolyte and proteinuria should be performed before surgery. Azotemic patient may have problems with fluid and management and monitoring CVP (PAWP) should be necessary. Hyperkalemia with or without hyponatremia is often seen in patient with mild to moderate renal insufficiency and hyperkalemia can precipitate an acute cardiac arrthmia.

            This metabolic finding often results from diabetic autonomic neuropathy and hyporeninmic hypoaldosteronism. Hypokalemia may be present, insulin and glucose infusion therapy may aggravate this condition. Proteinuria with resultant hypoalbuminemia, can cause extravasations fluid to the interstitial space, therefore potentiating problems with intravascular volume, cardiac output and alveolar oxygen exchange, depending on severity of proteinuria, combination of diuretics, fluid restriction, hemodialysis will be necessary for stabilization of intravascular volume status.

Metabolic Management and Monitoring

1. Insulin and glucose administration during surgery. Use of insulin and glucose infusion is recommended for all patients of diabetes undergoing general anaesthesia regardless of planned duration of the surgical procedure. The protocol includes intravenous administration of short acting insulin (regular human insulin) and 5-10% glucose solution. Because subcutaneous administration of insulin is associated with unpredictable absorption and variable plasma insulin levels used in patient undergoing minor procedures.  Protocol with IV insulin, the glucose and insulin contained in the same infusion mixture. The advantage of this approach is that if the glucose infusion is accidentally disconnected or obstructed then so is the insulin infusion, avoiding risk of hypoglycemia. The disadvantage is that no flexibility is allowed for changes in delivery rate of either insulin or glucose infusion.  Another approach is to administer insulin and glucose in separate bags that through same vein, i.e. “piggy bag”, insulin infusion on to glucose infusion. This allows independent adjustment to each infusion according to the levels of hourly capillary blood glucose measurement. With this protocol, a blood glucose level in the range of 100-125mg/dl is easily maintained during entire peri operative period. Insulin solution bag using regular insulin to a concentration of 1 u/cc.

Representative protocol for insulin glucose infusion for perioperative periods

Blood Glucose	Insulin Infusion	5% D Infusion (ml/hr)
<71mg/dl	0.5 u/hr	150 ml/hr
71-100mg/dl	1 u/hr	125 ml/hr
101-150mg/dl	2 u/hr	100 ml/hr
151-200mg/dl	3 u/hr	50 ml/hr
201-250mg/dl	4 u/hr	0
251-300mg/dl	6 u/hr	0
³ 300mg/dl	10 u/hr	0

            Electrolyte solutions are administered as needed into the glucose infusion or with a separate infusion. In patient with azotemia or other problems with fluid management or those receiving large amount of other solutions, 10% dextrose can be substituted for 5% dextrose solution (i.e. 100gm of 50% dextrose to 1000ml 5% dextrose). Patient with severe fluid management problems eg those with congestive heart failure or ESRD may not tolerate the amount of fluids administered with either 5% dextrose or 10% dextrose infusion. Thus, to provide adequate carbohydrate supply, 50% dextrose must be administered through a central venous line.

In perioperative patient at risk of volume over load

Blood Glucose	Insulin Infusion	5% D Infusion (ml/hr)
<71mg/dl	0.5 u/hr	25 ml/hr
71-100mg/dl	1 u/hr	20 ml/hr
101-150mg/dl	2 u/hr	15 ml/hr
151-200mg/dl	3 u/hr	10 ml/hr
201-250mg/dl	4 u/hr	0
251-300mg/dl	6 u/hr	0
³ 300mg/dl	10 u/hr	0

            Patient undergoing CABG surgery and cardio pulmonary bypass often require higher doses of insulin to achieve glycemic control during preoperative period. Intensive glycemic control using intravenous insulin and dextrose solution during the perioperative period and subacute phase of myocardial infarction improve cardiovascular morbidity and mortality as well as general post operative outcome in diabetic patient.

            The treatment goals should approach blood glucose levels of 100-125mg/dl. Capillary blood glucose measurements taken in the operating and recovery rooms with bedside glucose monitoring devices are adequate for perioperative management. Hourly measurements are necessary to keep the blood glucose level between 100-125mg/dl to ensure safety should the glucose infusion invertly be discontinued. Patient is on nil by mouth. The management of stable diabetic patient undergoing minor procedures (endoscopy, surgery under LA) involves withhold morning dose of insulin/oral agent if the patient is going to be fasting and measuring capillary blood glucose every 2-4hrs.

            In Type I diabetic patient, taking either 1/3 or ½ of the intermediate acting insulin usually taken in the morning is a potential alternative. Also, supplemental subcutaneous  short acting insulin can be administered following a variable insulin schedule, and patients usual insulin dosage or oral agent can be resumed after surgery when the patient can eat.

Day of minor surgical procedure (if break fast allowed)

1. Give normal morning dose of insulin/oral agent.
2. Measure blood glucose level before and after procedure.
3. Give supplemental 4 units of human actrapid, subcutaneously if blood glucose >250mg/dl.
4. Give usual afternoon insulin or OHA.

Blood Glucose	Short / Fast acting insulin (u)
<151mg/dl	0 unit
151-200mg/dl	2 units
201-250mg/dl	3 units
251-300mg/dl	5 units
³ 300mg/dl	6 units

Post Operative Metabolic Management

            In critically ill patient who have undergone emergency surgery, the glucose and insulin infusion should be continuous until the metabolic condition is stable and the patient is able to tolerate oral feeding. The insulin and glucose infusion should not be stopped until 1-2hrs after administration of subcutaneous insulin. In these patient, the use of multiple subcutaneous injections of short acting before meals and intermediate or long acting basal insulin at bed time is recommended during the first 24-48 hrs after the insulin and glucose infusion are stopped and before the patient usual insulin regime is resumed.

            Post operative diabetes management when patient tolerate solid food.

1. Measure capillary blood glucose before meals, at 10pm and 3am.
2.  Provide three meals and three snacks (20-30 kcal/kg/day)
3. Administer intermediate/long acting basal insulin 10-20 u subcutaneous at 10pm.

Blood Glucose	Short or fast acting insulin (units)
	Before breakfast	Before Lunch	Before Dinner	10.00pm
<71mg/dl	3	2	2	0
71-100mg/dl	4	3	3	0
101-150mg/dl	6	4	4	0
151-200mg/dl	8	6	6	0
201-250mg/dl	10	8	8	1
251-300mg/dl	12	10	10	2
³ 300mg/dl	14	12	12	3

            Depending on the type of procedure, some patients will require continuous enteral nutrition. In these cases, we recommend multiple short acting insulin injection every 4-6 hrs. Because the patient is receiving fluid continuously, the risk of hypoglycemia is low.

            The use of TPN is occasionally required in post operative period. Initially insulin should be given as a continuous infusion separate from the TPN solution. Once a stable dose of insulin is ascertained (with in 12-24 hrs) the total amount of insulin required over 24 hrs can be added to the TPN bag, with frequency of the capillary  blood glucose measurement can be reduce to every 2-4 hrs. The doses of insulin needed during TPN can be high and more often >100 units in 24 hrs, depending on patients metabolic status and insulin sensitivity.

            With IV insulin infusion, severe hypokalemia and hypophosphatemia can occur.

2. Post Operative Cardio Vascular Evaluation

            Several posts operative ECG are recommended for older diabetic patient with long standing Type I diabetes, patient with known heart disease. Post operative MI may be silent and has a high mortality. IV fluids and wedge pressure monitoring after surgery might be necessary in some patients with cardiomyopathy.

            When ambulation of patient begins, attention must be paid to possibility of orthostatic hypotension. Evaluation of mental and neurological status will help to assess changes associated with possible embolism of unstable carotids. Early ambulation should be encouraged, depending on the type of surgical procedure. If ambulation is not allowed, antithombotic measures should be instituted soon after surgery.

3. Post Operative Renal Evaluation

            Careful monitoring of BUN and Serum creatinine level will help to detect acute kidney failure that may occur, especially after procedures with iodinated contrast material.

            Patient on metformin should be advised to withhold morning before receiving intravenous contrast and resume metformin 48 hrs after the test is performed if renal function has not worsened.

4. Post Operative Infection

            Wound infections are common among diabetic patients with poor metabolic control. Impaired granulocyte function due to hyperglycemia may predispose the patient to bacterial infections. Poor circulation due to macroangiography or micro can contribute to post operative infection. Tight metabolic control during perioperative period can decreased the risk of post operative infection and improve post operative outcome.

            For, wound infection, antibiotic coverage must include coverage for anaerobic bacteria, gram negative entero bacteria and staphyllococcus aureus. Early surgical debridement and drainage is performed. Cultures should be obtained during drainage procedures and before antibiotic therapy is started (if severe infection not responding to antibiotics, suspect candida species or other fungal infection) other source of infection

            IV catheter insertion sites

            Pressure and decubitus ulcers

            Nasopharynx (due to nasotracheal / orotracheal tubes for ventilatory support)

            Nasogastric tube for feeding purposes

            Urinary catheterization

            Source of infection to be identified by blood and urine culture sensitivity, chest X-ray, replacement of IV catheter, culture of catheter tips recommended periodic evaluation to be performed (A1c lipid profile, microalbuminuria evalution, foot examination, neurological examination, opthalmological examination) and updated routine vaccination  (tetanus, pneumonia, influenza)

Note:

            Glycemic metabolic and nutritional factor and cardiovascular, neurological and renal function should be evaluated and optimized if possible before surgery cardiovascular hemodynamic and intravascular status should be carefully monitored during and after surgery, and normoglycemia should be achieved and maintained during surgery and recovery.

REFERENCE:

            Therapy for Diabetes Mellitus and Related Disorder ADA