Praparing diabetic patient for surgery

PREPARING DIABETIC PATIENT FOR SURGERY
PRE_OP ASSESSMENT
A comprehensive history and physical examination is imporatnt. Since estimates suggest that one third of diabetic patients are unaware of their disease, it may be prudent to screen all patients undergoing intermediate or major surgery by checking glycosylated hemoglobin (HbA1c).
The history should include the following:
Suggestive symptoms (eg, polyuria/polydipsia, blurred vision)
Eating patterns, nutritional status, exercise history, and weight history
Current treatment of diabetes, including medication regimen, diet, and glucose monitoring results
Frequency, severity, and etiology of acute complications (ie, ketoacidosis, hypoglycemia)
Prior or current infections (eg, skin, foot, dental, genitourinary)
Symptoms and treatment of chronic eye; kidney; nerve; genitourinary, bladder, and gastrointestinal function; heart; peripheral vascular; foot; and cerebrovascular complications
Nondiabetic medications that may affect blood glucose levels (eg, corticosteroids)
Risk factors for atherosclerosis, such as smoking, hypertension, obesity, dyslipidemia, and family history
History and treatment of other conditions, including endocrine and eating disorders
Family history of DM, endocrine disorders
Lifestyle, cultural, psychosocial, and economic factors that might influence DM management
Tobacco, alcohol, and/or controlled substance use
The physical examination includes assessment for orthostatic hypotension as a potential sign of autonomic neuropathy. A fundoscopic examination may give insight into the patient's risk of developing postoperative blindness, especially following prolonged spinal surgery in the prone position and cardiac surgery requiring cardiopulmonary bypass.
Type 1 DM is associated with a “stiff joint” syndrome, which poses a significant risk during airway management at the time of general anesthesia. Affecting the temporomandibular, atlantooccipital, and other cervical spine joints, these patients also tend to have short stature and waxy skin, related to chronic hyperglycemia and nonenzymatic glycosylation of collagen and its deposition in joints. A positive “prayer sign” can be elicited on examination with the patient unable to approximate the palmar surfaces of the phalangeal joints while pressing their hands together; this represents cervical spine immobility and the potential for a difficult endotracheal intubation.
Further airway evaluation should include assessment of thyroid gland size, as patients with type 1 DM have a 15% association of other autoimmune diseases, such as Hashimoto thyroiditis and Graves disease.
Finally, the degree of preoperative neurological dysfunction is important to document, especially prior to regional anesthesia or peripheral nerve blocks, to assess the degree of subsequent nerve injury.
The laboratory evaluation should include the following:
Hemoglobin A1C, serum glucose
Fasting lipid profile (total cholesterol, HDL cholesterol, triglycerides, LDL cholesterol)
Liver function tests (if abnormal, further evaluation for fatty liver or hepatitis)
Urinalysis (ketones, protein, sediment), microalbuminuria
Serum creatinine and estimated glomerular filtration rate
Serum electrolytes
Electrocardiogram
GENERAL PRE_OP MANAGEMENT
On the day of surgery, patients on oral regimens should be advised to discontinue these medications. Secretagogues (eg, sulfonylureas, meglitinides) have the potential to cause hypoglycemia. In addition, sulfonylureas have been associated with interfering with ischemic myocardial preconditioning and may theoretically increase risk of perioperative myocardial ischemia and infarction. Patients taking metformin should be advised to discontinue this drug because of the risk of developing lactic acidosis. For these patients, short-acting insulin may be administered subcutaneously as a sliding scale or as a continuous infusion, if needed, to maintain optimal glucose control, depending on the extent of surgery.
Patients who are insulin-dependent (type 1) should be advised to reduce their bedtime dose of insulin the night prior to surgery to prevent hypoglycemia, while nil by mouth. Maintenance insulin may be continued, based on history of glucose concentrations and the discretion of the advising clinician. Patients may be advised to consult their anesthesiologist and diabetes-managing practitioner for individualized recommendations regarding their situation. Additionally, patients should be monitored periodically preoperatively to assess for hyperglycemia and hypoglycemia.

DURING SURGERY
All patients undergoing surgery, under general anesthesia, require changing over to insulin from OHA and to regular insulin from intermediate acting insulin. Surgery should be scheduled in the morning. Omit BBF insulin. Do fasting blood sugar and put patient on GIK (Glucose-Insulin-Potassium) regimen according to blood sugar level at least one hour before starting surgery. The GIK regimen should continue at least one hour after the patient has taken the first postoperative meal and patient is shifted to pre-surgery thrice a day insulin regimen14.
During surgery do blood sugar at 1/2 hourly or one hourly interval as per the status of patient. Because of surgical stress, insulin requirements are more with intra-abdominal or thoracic surgery. CABG puts maximum surgical stress. The stress caused by laparotomy is much more than the stress caused by even whole body skin grafting.
Glucose-Insulin-Potassium (GIK) Regimen

Blood / Plasma Glucose mg.%
Fluid100 ml/hr.
InsulinU/100 ml
InsulinU/500 ml
KClmeq/100ml
< 100
10% Dextrose
1
5
2
100-200
10% Dextrose
2
10
2
200-300
10% Dextrose
3
15
2
300-400
10% Dextrose
4
20
2
>400
N / Saline
4
20
2
GOALS OF GLYCEMIC CONTROL
The goals for glycemic control are tailored to each patient based on a number of factors, such as nature of surgery, severity of underlying illness, modality used to achieve glycemic control, patient age, and sensitivity to insulin. Numerous clinical trials have involved various patient populations and examined the implications of perioperative hyperglycemia. Based on data derived from these studies, the American Diabetes Association has made recommendations for managing blood glucose levels in hospitalized patients with DM (see Table 1).
Table 1. American Diabetes Association Recommendations for Target Inpatient Blood Glucose Concentrations
Patient Population
Blood Glucose Target
Rationale
General medical/surgical
Fasting: 90-126 mg/dL Random: <180 mg/dL
Better outcomes, lower infection rates
Cardiac surgery
<150 mg/dL
Reduced mortality, reduced risk of sternal wound infections
Critically ill
80-110 mg/dL
Reduced mortality, morbidity (SICU); reduced morbidity; length of stay (MICU)
Acute neurological disorders
<110 mg/dL
Increased mortality if admission blood glucose >110 mg/dL
Prior to elective surgery, it is ideal for patients to have their HbA1c value at less than 6%. More stringent goals may further reduce complications; however, this is at the cost of increased risk of hypoglycemia. Less intensive glycemic control may be indicated in patients with severe or frequent episodes of hypoglycemia. Special populations, such as pregnant and elderly patients with DM, may require additional considerations. In addition, a plan for hypoglycemia should be delineated for individual patients.
Methods of Achieving Glycemic Control
Certain patients taking oral agents prior to surgery may be able to restart their previous regimen postoperatively; however, appropriateness of oral agents needs to be reassessed because of potential complications (see Table 2). Intravenous insulin is the most flexible and readily titratable agent, with few, if any, contraindications, making it an ideal agent for perioperative use.
Table 2. Considerations for Oral Agents
Class of Oral Agent
Example
Considerations
Secretagogues (eg, sulfonylureas, meglitinides)
Glyburide, glimepiride
Hypoglycemia, prolonged action, difficult to titrate
Biguanides
Metformin
Risk of lactic acidosis, use cautiously in renal or hepatic insufficiency, CHF
Thiazolidinediones
Rosiglitazone
Increased intravascular volume (CHF), slow onset of effect, difficult to titrate
The length, type of surgery, and degree of glycemic dysregulation will dictate the degree of supplemental intravenous insulin therapy. Patients with type 1 diabetes should have elective surgeries scheduled as the first case of the day to minimally disrupt their DM regimen. Depending on the length and extent of surgery, patients are often advised to administer half of their daily dose of long-acting insulin and to arrive at the preoperative admitting area early enough to have an intravenous infusion of dextrose instituted and their serum glucose monitored until the time of surgery. Perioperative methods for achieving tight glycemic control (80-110 mg/dL) are as follows:
Establish separate intravenous access for a “piggyback” infusion of regular insulin (50-100 U per 50-100 mL 0.9 saline, respectively). The infusion rate can be determined by using the formula: insulin (U/h) = serum glucose (mg/dL)/150. Intravenous glucose solution should be administered concomitantly to avoid hypoglycemia. Typically, a 5% dextrose solution is started when serum glucose levels are less than 150 mg/dL. Intra-arterial catheter placement is recommended to be able to sample glucose concentrations every 1-2 hours intraoperatively and postoperatively until a regimen of subcutaneous insulin or oral hypoglycemic agent is reinstituted. A second intravenous catheter is used for intravascular volume replacement with an isotonic saline solution.
. Use a computer-based system and set controls for intravenous insulin to achieve desired blood glucose level.
An example of such a system is the Glucommander®, presented at the 2003 Diabetes Technology meeting in San Francisco, CA; it is a novel method of attaining optimal glucose control by programming an intravenous infusion of insulin to respond to the measured serum glucose concentration. Initial parameters and baseline glucose value are entered. The program then recommends an insulin infusion rate and intervals to check subsequent glucose levels; this process may be repeated indefinitely. The amount of insulin recommended is based on a simple equation: insulin per hour = multiplier x (blood glucose – 60). Blood glucose concentrations are monitored as frequently as every 20 minutes up to a maximum interval specified in the initial orders. Typically, the monitoring interval is every hour, increasing when glucoses stabilize in the target range and decreasing if sugars are low or falling rapidly. The Glucommander® has been the successfully implemented in the critically ill as well as noncritically ill patient populations. However, intraoperative use has yet to be recommended..