DIABETES MELLITUS

General Peri-operative Management Goals

Assess the Type of diabetes and the duration of the disease

1. Insulin Dependent Diabetes Mellitus or Type I diabetes. The classic description is early onset of diabetes with exogenous insulin needed to prevent keto-acidosis formation. It is thought to be due to an autoimmune disorder causing a destruction of the pancreatic islet cells.
2. Non Insulin Dependent Diabetes Mellitus or Type II diabetes. The classic description is an older onset of diabetes in an overweight patient, they do not tend towards keto-acidosis because of a residual endogenous insulin production. Good blood glucose control may require exogenous insulin.
3. Disease associated
   1. Pancreatic
      • Chronic pancreatitis
      • Pancreatic carcinoma
      • Pancreatectomy
      • Infiltration of pancreatic tissue eg. haemochromatosis.
   2. Hormonal excess
      • Cortisol
      • Growth Hormone
   3. Drugs
      • Thiazides Diuretics
4. Gestational A-F treated as IDDM for anaesthesia

1. Ischaemic Heart Disease - Often silent ischaemia
2. Impaired ventricular function
3. Hypertension and associated treatment

History to determine effort tolerance, clinical examination for cardiac failure and an electrocardiogram in all patients. Echocardiography can help in assessing an ejection fraction in borderline cases

Renal

1. Renal dysfunction - Protinuria is an early manifestation but quantitative measurement will not alter anaesthetic mangement. Dialysis should optimally be done the day before surgery.
2. Urinary infection

Urea and electrolyte determination.
Dipstix urinalysis for proteinuria

Gastrointestinal
Gastroparesis - History of eary satiety and reflux

Nervous System

1. Cardiac Autonomic Neuropathy
2. Counter-regulatory response to hypoglycaemia 
3. Peripheral glove and stocking neuropathy with an increased susceptibility to iatrogenic nerve injuries

History of postural dizziness, post gustatory sweating, noctural diarrhoea and impotence. Careful documentation of peripheral sensation.

Small Joint Disease

Clinical assessment of neck extension, examination of the small joints of the hand and a good evaluation of the ease of intubation.

Ophthalmology
Cataracts, glaucoma and retinopathy will decrease visual acuity and increase the unpleasantness of the perio-operative period. Increase the amount of explanation and reassurance to the patient.

Evidence of overt infectious disease
A chest X ray is often warrented to search for occult tuberculosis.
Take careful note of the central nervous system and the head and neck.

Metabolic Control
Hypoglycaemia
The diabetic patient is at an increased risk for peri-operative hypoglycaemia.

1. They are often receiving exogenous insulin,
2. They are being starved, often for prolonged periods of time because of fears of delayed gastric emptying
3. Their counter-regulatory mechanisms may be defective because of an autonomic dysfunction.
   

Hyperglycaemia
Glucagon, cortisol and adrenaline secretion as part of the neuroendocrine response to trauma will increase in proportion to the magnitude of the stress. During major catabolic insults are associated with a severe hyperglycaemia which can cause
Osmotic diuresis, making volume status difficult to determine and risking profound dehydration and organ hypoperfusion
Hyperosmolality with hyperviscocity, thrombogenesis and cerebral oedema

Keto-acidosis
Any patient who is in a severe catabolic state and has an insulin deficiency (absolute or relative) can decompensate into keto-acidosis

Electrolyte abnormalities
Anticipate imbalances in potassium, magnesium and phosphate

Protein catabolism and impaired polymorphonuclear phagocytic function
Proteolysis and decreased amino acid transport retards wound healing. Loss of phagocytic function increases the risks of post-operative infection.

Specific Peri-Operative Management
Choice of Anaesthetic
Surgical requirements and the patients physiological status dictate the primary anaesthetic. Regional anaesthesia has the advantages of attenuating the neuroendocrine response to surgery and having an awake responsive patients who can report symptoms promptly. A thorough neurlogical examination is mandatory to document the degree of peripheral neuropathy present.

Fluid Replacement
Ringer's Lactate has 28mmol/L of the gluconeogenic substrate lactate present and blood will have various amounts depending on the degree of storage. Massive infusion of Ringer's and blood will complicate blood glucose control.

Diabetic Keto-acidosis
Diabetics with infections will all have some degree of dehydration, hyperglycaemia, acidosis and hypovolaemia present. Medical management of these patients is not possible without removal of the infection. When aggressive resuscitation with fluid, insulin and potasium has made some improvement of the metabolic condition, anaesthesia can be started. With the removal of the source of infection the fluid, insulin and potasium requirements are often markedly decreased, so these patients must have close post-operative monitoring as well.

Glucose / Insulin / Potasium Infusion
There are numerous different regimens recommended for diabetes, the pricinpals are all the same and the actual implementation will depend on the facilities available

Infuse Insulin.

1. All patients who are maintained on insulin must receive it in some form during surgery.
2. Start the insulin infusion at 0.1 Units per 100g of dextrose.
3. Increase the dose of insulin according to the blood glucose level
   • Make up a solution of dextrose and insulin in small aliquots to allow hourly adjustment to the amount of insulin required
   • A separate insulin infusion run by an infusion pump can be started
     

Infuse Glucose at 0.1g/kg/hr.

1. Run a 10% glucose solution at 1ml/kg/hr.
   • Utilise a buratrol to ration the fluid and to allow for hourly insulin additions
   • Utilise a flow restricting device or an infusion pump

Infuse Potasium along with the glucose and insulin

1. Utilise a set amount of potasium that you only change is the value becomes severly deranged
2. Add potasium on an hourly basis determined by the plasma potasium level

Summary of Management