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Surgical problems encountered in diabetes
Of the many surgical problems related to diabetes mellitus the important are CABG, limb
amputation, eye surgery (cataract operation), carbuncle, non healing foot lesion, urological surgery, renal transplantation, cholecystitis, cholelithiasis, and gangrenous foot. 20% of all patients admitted in surgical wards have diabetes mellitus.-In a survey in 1991,18% of 28,000 patients in surgical wards in Bombay Hospital had diabetes mellitus.
Metabolic response to surgery in diabetes mellitus
Surgery is a stressful condition, more so for diabetics as a result of which there is
increased secretion of ACTH, GH, vasopressin, sympathetic activity, glucagon, cortisol, angiotensin II and aldosterone. Hyperglycaemia secondary to these counter regulatory hormones occurs due to changes in peripheral resistance,hepatic glueogenolysis, hepatic glycogenolysis and lipolysis, Patients of IDDM may lapse into diabetic ketoacidosis (DKA) and hyperglycaemia while there may be milder metabolic changes in NIDDM. In the obese NIDDM there is increased risk of thrornboembolism, orthostatic pneumonia, cardiac and anaesthetic complications.
Diabetes mellitus can modify the outcome of surgery in the form of increased pre and post operative morbidity and infections, higher incidence of delayed wound healing. Also there is higher incidence of unstable hyperglycaemia and hypoglycaemia.
Principles of management of diabetes mellitus during surgery
The operations should be scheduled early in the day. All diabetics requiring insulin should
be switched over to regular insulin.
In cases of IDDM IV insulin and glucose is needed during surgery and in NIDDM insulin is
needed only for major surgery otherwise they are only observed and biguanides and sulphonyl urea has to be stopped. The blood glucose has to be monitored frequently. Problem in CABG: Large volume of fluids are given containing glucose and lactose and adrenergic agents used worsen the diabetic state. Surgical stress, hypothermia all contribute to the insulin resistance. The insulin requirement in CABG is as stated below:
a) Pre-operative 1.5 units/hour
b) After skin incision 3.0 units/hour
c) During bypass 5.0 units/hour
d) Immediate post op. 8.3 units/hour
e) 4 hour post op. 12.3 units/hour
Problems in renal transplantation in diabetics
Large volume of glucose given along with corticosteroids alter the blood sugar level and
hence special precautions are to be taken.
Diabetic complications causing confusion in surgical wards
Patients of DKA may present with abdominal pain along with leucocytosis which may be
confused with acute abdomen. Diabetic autonomic neuropathy can cause gastric paresis and aspiration and also urinary retention necessitating catherterization and cardiac autonomic neuropathy can cause cardiac arrhythmias and cardiac arrest.
Assessment of pre operative risk in a diabetic patient going for surgery
In the cardiovascular system, assessment should be done to rule out coronary artery
disease, hypertension, myocardial infarction, dyspnoea. As far as the nervous system is concerned the problems of cardiac arrhythmias, sudden hypotension, susceptibility to bed sore, autonomic dysfunction and unrecognized hypoglycaemia has to be kept in mind. For the kidney the change in renal functions, volume overload, electrolyte disturbance and changing insulin pharmaco kinetics has to be kept in mind. For the lungs-pneumonias and tuberculosis deserve special attention.
Guidelines for pre-operative management of diabetes mellitus
All diabetics except NIDDM undergoing minor surgery should be admitted 2 to 3 days
before surgery and CVS, pulmonary, renal, neurological and autonomic systems should be assessed. Oral hypoglycaemic agents should be discontinued and the patient should be stabilised on regular insulin thrice a day so that euglycaemia is obtained with blood sugar remaining below 140mgm% Tight metabolic control should be avoided to reduce chances of unrecognised severe hypoglycaemia. The surgery should be scheduled in the morning to avoid unnecessary anxiety and starvation. The post operative complications can be dealt easily.
NIDDM patients undergoing minor surgery should be admitted the previous day and OHA
discontinued on the day of surgery and the patient followed closely till after operation.
Insulin regime during surgery for IDDM and NIDDM taking insulin
Glucose insulin potassium' infusion (GIK regime) is given wherein 10-20 units of insulin
along with lOmeq. of KCI in 500 c.c.of 10% Dextrose is given with the rate of infusion kept at 100 ml/hour. If 5% Dextrose is used then 5 meq. of KCI and 10 units of insulin are used.
In the GIK regime 0.2 to 0.4 units of insulin per gram of glucose is administered. But in
special circumstances the dose may be adjusted as given below:
|
Insulin unit/gm of glucose
|
| Normal weight |
0.2 - 0.4 |
-do- |
| Obesity |
0.4 |
-do- |
| Liver disease |
0.4 - 0.6 |
-do- |
| Steroid therapy |
0.4 - 0.4 |
-do- |
| Gram-ve sepsis |
0.5 - 0.7 |
-do- |
| Cardiopulmonary bypass |
0.9 -1.2 |
-do- |
Ringer lactate should be avoided because of lactic acidosis and it is also glycogenic
precursor.
There are certain precautions to be taken during GIK regime. Other IV fluids or
medications should not be infused through the GIK lines. The rate of infusion must be ensured and in the elderly the rate should be reduced to 500 c.c. every 6-8 hours. One should always be in the lookout for dilutional hyponatremia which may occur.
Management during surgery of those diabetic patients who are euglycaemic on diet
therapy alone - also requires mention. Here also surgery should be planned in the morning. Glucose containing IV fluids should not be infused and blood glucose should be monitored frequently. If blood glucose goes beyond 200 mgm% then insulin is .to be started. Anti diabetic tablets should be started on the first jost-operative meal.
Time of stopping insulin and return to original therapy
In case of minor surgery the patient can return to previous regimen with first post-
operative meal but with close monitoring. In the case of major surgery once oral feeding commences, soluble insulin is to be administered subcutaneously three times a day before each meal. After 2-3 days the patient is stabilised on previous regimen.
Factors modifying insulin dosage during post-operative period
The insulin dose is to be decreased during fasting, vomiting, jaralytic ileus, coma, surgery
of adrenal and pituitary, after aspiration of abscess and post-partum period of gestational diabetes mellitus. The insulin dosage is to be increased by 20% in presence of infections.
Factors to be considered during surgery in a diabetic
The important factors to be considered are the age of the patient, whether he is NTDDM
or IDDM, whether the diabetes is complicated or uncomplicated, whether on diet or oral antidiabetics or insulin, whether it is a minor or major surgery, duration of surgery, whether it is an emergency surgery, the type of anaesthesia and anaesthetic agents used and the vascular status. Surgery can be done in a ketoacidotic patient if it is a life saving surgery but only after correction of ketoacidosis,
Effect of anaesthetic agents on blood glucose
1% halothane, 5 mgm phenoperidine, cyclopropane, ether, ethyl chloride, chloroform also
increase blood glucose whereas pentothal sodium, nitrous oxide, tubocurarine have no effect on blood glucose.
IV fluid in the post operative state
Body requires 50 gms. of glucose 8 hourly for energy and to avoid ketosis, 1000 c.c. of 5% or 500 c.c. of 10% Dextrose.
Monitoring blood glucose and urine testing
Urine sugar estimation is erratic. Moreover there may be retention, decreased output and
also the problem of renal threshold may appear. Also with IV glucose urine test is not dependable. Hence blood sugar estimation has to be done with dextrostix or glucometer. Also blood should not be drawn from the same limb in which the IV fluid is running-this might give false high reading.
In the sliding scale fixed dose of insulin is given according to urine sugar at specified period. The problem is that we correct the blood sugar when it has already gone up but we are not preventing its rise.
Route and type of insulin to be used during surgery
As far as the route of insulin to be given is concerned, during surgery and post operative
days when the patient is not taking orally and when the blood pressure is on the lower side the IV route is preferred, once a patient starts taking oral feed we can start the subcutaneous route.
The type of insulin to be given in diabetics undergoing surgery should always be short
acting and not long acting and purified insulin should be used. Intermittent therapy with conventional therapy leads to insulin antibodies and later causes insulin resistance.
Goals of therapy
The therapy should be aimed to minimise fluid and electrolyte loss, prevent ketosis, avoid
hypoglycaemia and avoid wound sepsis and delayed healing.
Some special situations
If a diabetic after surgery does not come out of anaesthesia then hypoglycaemia should
be suspected. If a diabetic after surgery keeps persistent tachycardia then also we must suspect hypoglycaemia. If a diabetic after surgery has hypotension with left ventricular failure then a silent myocardial infarct should be suspected.
REFERENCES
1. Stephen Podolsky-Surgery in diabetic pattents in clinical diabetes-Modern
Management, Appleton Century Crops New York. Pager 509-536-1980
2. M.M.S. Ahuja- Diabetes and Surgery in Practice of Diabetes Mellitus. Vikas
Publishing House Pvt. Ltd., New Delhi-1883 Page 206-214.
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