Anesthetic Management of Diabetic Patients

Many of the operations diabetic patients face are a direct result of their disease. Skin ulcers, amputations and abscesses are amongst the commonest. Successful management of the diabetic patient depends as much, if not more, on the proper management of the chronic complications of the disease as on acute glycemic management.

Preoperative Anesthetic Management

A thorough preoperative search must be done for end-organ complications of diabetes mellitus. In addition to a thorough history and physical, a recent ECG, blood urea nitrogen, potassium, creatinine, glucose, and urinalysis are essential.

Anesthetic consideration of symptoms of secondary involvement of other organs: Diabetes causes disease in many organ systems, the severity of which may be related to how long the disease has been present and how well it has been controlled.

  • Heart disease: diabetics are more prone to hypertension, ischemic heart disease, cerebrovascular disease and silent myocardial infarction. Damage to the nerves controlling the heart and blood vessels (autonomic neuropathy) may result in sudden tachycardia, bradycardia or a tendency to postural hypotension. Diabetic autonomic neuropathy may limit the heart's ability to compensate for intravascular volume changes and may predispose patients to cardiovascular instability (eg, post induction hypotension) and even sudden cardiac death, the incidence of which may be increased by the concomitant use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. A history of shortness of breath, palpitations, ankle swelling, tiredness and chest pain should therefore be sought. A routine ECG and stress testing should be done.
  • Renal disease: kidney damage may already be present, often indicated by the presence of protein (albumin) in the urine. Renal infections are common and should be treated aggressively with antibiotics. The diabetic is at risk of acute renal failure postoperatively. Blood electrolyte measurement (if possible) may reveal a raised urea and creatinine. If the potassium is high (> 5 mEql/l) then specific measures should be taken to lower it before surgery.
  • Gastrointestinal problems: the nerves to the gut wall and sphincters can be damaged. Delayed gastric emptying and increased reflux of acid make them more prone to regurgitation and at risk of aspiration on induction of anesthesia. A history should be sought of heartburn and acid reflux when lying flat; if present they should have a rapid sequence induction with cricoid pressure, even for elective procedures. Ranitidine 150mg or cimetidine 400mg plus metoclopramide 10mg orally 2 hours preoperatively to reduce the volume of stomach acid.
  • Airway: Glycosylation of collagen in the cervical and temporo-mandibular joints can cause difficulty in intubation (Fig5.1).

Fig.5.1 Diabetic hand

To test if a patient is at risk, ask them to bring their hands together, as if praying, and simultaneously hyperextend to 90 degrees at the wrist joint. If the little fingers do not oppose, anticipate difficulty in intubation.

  • Eye disease: cataracts are common, as is an abnormal growth of blood vessels inside the eye (retinopathy). The anesthetist should try to prevent sudden rises in blood pressure that might rupture them, further damaging the eyesight. Ensure an adequate depth of anesthesia, especially at induction.
  • Infection: diabetics are prone to getting infections that can upset their sugar control. If possible, delay surgery until these are treated. Wound infections are common. Great care should be paid to aseptic techniques when any procedure is undertaken
  • Hydration - Glucose in the urine (glycosuria) causes a diuresis which makes the patient dehydrated and even more susceptible to hypotension. Check for dehydration and start an intravenous infusion.
  • Miscellaneous: diabetes may be caused or worsened by treatment with corticosteroids, thiazide diuretics and the contraceptive pill. Thyroid disease, obesity, pregnancy and even stress can affect diabetic control.

Plan Ahead for Blood Glucose Control Perioperatively

The primary goal of intraoperative blood sugar management is to avoid hypoglycemia. Unacceptably loose blood sugar control (> 180 mg/dL) also carries risk. Hyperglycemia has been associated with hyperosmolarity (dehydration), infection, and poor wound healing. There are several perioperative management regimens for diabetic patients.

Alternative Regimen 1: In the most common, the patient receives a fraction usually half of the total morning insulin dose in the form of intermediate-acting insulin. To decrease the risk of hypoglycemia, insulin is administered after intravenous access has been established and the morning blood glucose level is checked. For example, a patient who normally takes 30 U of NPH (neutral protamine Hagedorn; intermediate-acting) insulin and 10 U of regular or Lispro (short-acting) insulin or insulin analogue each morning and whose blood sugar is at least 150 mg/dL would receive 15 U (half of 30, half the normal morning dose) of NPH subcutaneously or intramuscularly before surgery along with an infusion of 5% dextrose solution (1.5 mL/kg/h). Absorption of subcutaneous or intramuscular insulin depends on tissue blood flow

Dedication of a small-gauge intravenous line for the dextrose infusion prevents interference with other intraoperative fluids and drugs. Supplemental dextrose can be administered if the patient becomes hypoglycemic (< 100 mg/dL). However, intraoperative hyperglycemia (> 150-180 mg/dL) is treated with intravenous regular insulin according to a sliding scale. One unit of regular insulin given to an adult usually lowers plasma glucose by 25-30 mg/dL.

Alternative Regimen 2

Steps to select appropriate management regime

  1. Decide on the type of surgery

    • Minor - patients expected to eat and drink within 4 hours of operation (Table5.3)
    • Major - all other patients (Table5.4)

  1. Then, is the patient insulin or non-insulin dependent?
  2. Finally:

    • Are they -poorly controlled: delay surgery and change to soluble insulin three times daily but if surgery urgent, use Major surgery regime
    • Well controlled: use the appropriate regime from the Major or minor

General Measures for all diabetics: Measure random sugar preoperatively - 4 hourly for IDDM & 8 hourly for NIDDM

  • Test urine 8 hourly for ketone and sugar
  • Place first on operating list
  • Aim for a blood glucose of 6 - 10mmol/l(120-140mg/dl)

If the patient is taking an oral hypoglycemic agent preoperatively instead of insulin, the drug can be continued until the day of surgery, but sulfonylureas and metformin should not be used for 24-48 h before surgery because of their long half-lives. They can be started postoperatively when the patient is taking drugs per os. Metformin is restarted if renal and hepatic functions remain adequate. Because of the long duration of action, a glucose infusion is begun and blood sugars are monitored as though intermediate-acting insulin had been given.

Table5.3 Management During Minor Surgery

Non insulin Dependent Diabetics
Note 1mmol/l = 18mg/dl		 Preoperatively - random blood sugar
On admission - < 10 mmol/l Normal medication until day of op
> 10 mmol/l Follow as for MAJOR SURGERY
Day of operation
Omit oral hypoglycemic Blood glucose- 1 hour preop and at least once during op (hourly if op > 1 hour long) postop - 2 hourly until eating then 8 hourly Postoperatively Restart oral hypoglycemics with first meal
Insulin dependent
Diabetics
This regime only suitable for patients whose random sugar is < 10 mmol/l on admission, will only miss one meal preoperatively & are first on the list for very minor surgery eg cystoscopy		 Preoperatively: Normal medication
Day of operation: No breakfast, no insulin, place first on list. Blood glucose- 1 hour preoperatively and at least once during op (hourly if op > 1 hour long) postoperatively - 2 hourly until eating then 4 hourly Postoperatively: Restart normal subcutaneous insulin regime with first meal


Table 5.4 Management for Major Surgery

  • All insulin dependent and non-insulin dependent who are poorly controlled (blood glucose >10mmol/l) (many NIDDM become insulin dependent during major surgery and will need managing as such. Regular glucose measurements will detect this).
  • Normal medication until day of operation

Day of operation

  • Omit oral hypoglycaemics and normal subcutaneous (S/C) insulin Blood glucose - check blood sugar(and potassium) 1 hour preop then 2 hourly from start of infusion at least once during operation (hourly if op > 1 hour long) at least once in recovery area 2 hourly post operatively

Regime 1 - no infusion pump available. Start intravenous infusion of 5 or10 % dextrose (500 ml bags) over 4 - 6 hours and add Insulin and Potassium. Chloride (KCl) to each 500 ml bag as below. Change bag according to blood sugar level readings:


Blood glucose
(mmol/l)		 Soluble insulin(units)
to be added to bag		 Blood potassium
(mmol/l)		 KCl(mmol)
(to be added to bag)
4 No insulin
4 - 6 5 < 3 20
6-10 10 3-5 10
10-20 15 >5 None
>20 20

If blood potassium level not available, add 10 mmol KCl

Postoperatively

Non-insulin dependent

  • Stop infusion and restart oral hypoglycaemics when eating and drinking

Insulin dependent

  • Stop infusion when eating and drinking
  • Calculate the total daily dose (units) of insulin the patient was taking preoperatively
  • Give this as S/C Soluble insulin (Actrapid), divided into 3 - 4 doses in 24 hours
  • This may need to be adjusted up or down until blood sugar levels stable.
  • Once stable restart normal regime

Remember that the patient may need additional fluids depending on surgery, blood loss etc.

Last modified: Sunday, 20 November 2016, 3:43 PM