Management of Diabetes in Surgery

Diabetes

Diabetes is a metabolic disorder resulting from insulin deficiency or intolerance

Associated with acute and long term systemic problems

Diagnosed by a random plasma glucose >11.1mmol/l and a fasting glucose>7.0mmol/l (WHO criteria)

The two most common forms of diabetes are Insulin Dependant Diabetes Mellitus (Type 1) and Non Insulin Dependant Diabetes Mellitus (Type 2)

Type 1 Diabetes Mellitus

Polygenic disorder thought to be of auto immune aetiology

Results in destruction of β cells in the Islets of Langerhans in the Pancreas, with subsequent insulin deficiency

Young onset 0.4% prevalence Endogenous insulin is required to maintain plasma

glucose levels to within physiological levels

Type 2 Diabetes Mellitus

Hypoglycaemia resulting from reduced insulin secretion and peripheral insulin resistance

Some genetic concordance Older onset, associated with central obesity Depending on severity, may be controlled

with:– diet and exercise to lose weight– oral hypoglycaemics– insulin

Diabetes and Surgery Surgery is a form of physical trauma It results in catabolism, increased metabolic rate, increased

fat and protein breakdown, glucose intolerance and starvation.

In a diabetic patient, the pre existing metabolic disturbances are exacerbated by surgery

The type of diabetes, amount of insulin dose, diet or oral hypoglycaemic agents must be considered as this will change the overall management plan

The risk of significant end-organ damage increases with the duration of diabetes, although the quality of glucose control is more important than the absolute time

Factors Adversely Affecting Diabetic Control Perioperatively Anxiety Starvation Anaesthetic drugs Infection Metabolic response to trauma Diseases underlying need for surgery Other drugs e.g. steroids

Metabolic Responses to Surgery Hormonal

– Secretion of stress hormones

• Cortisol

• Catecholamines

• Glucagon

• Growth Hormone

• Cytokines

– Relative decrease in insulin secretion

– Peripheral insulin resistance

Metabolic– Increased

gluconeogenesis and glycogenolysis

– Hyperglycaemia– Lipolysis– Protein breakdown

Metabolic Response to Surgery and Diabetes

Hypoglycaemia– May develop perioperatively due to the residual effects of

preoperative long acting oral hypoglycaemic agents or insulin.

– Exacerbated by preoperative fast or insufficient glucose administration

– Counter-regulatory mechanisms may be defective because of autonomic dysfunction

– Can lead to irreversible neurological deficits

– Dangerous in anaesthetised or neuropathic patient as the warning signs may be absent

Management

– Give i.v dextrose and monitor glucose levels

Metabolic Response to Surgery and Diabetes

Hyperglycaemia– Glucagon, cortisol and adrenaline secretion as part of the neuroendocrine

response to trauma, combined with iatrogenic insulin deficiency or glucose overadministration may result in hyperglycaemia

– Causes osmotic diuresis, making volume status difficult to determine and risking profound dehydration and organ hypoperfusion, and increased risk of UTI

– osmotic diuresis, delayed wound healing, exacerbation of brain, spinal cord and renal damage by ischaemia

– Results in hyperosmolality with hyperviscocity, thrombogenesis and cerebral oedema

Management

– Frequently measure blood glucose and administer insulin

Metabolic Response to Surgery and Diabetes Ketoacidosis

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

– Most common in type 1 patients

– Increased risk postoperatively, often precipitated by the stress response, infection, MI, failure to continue insulin therapy.

– characterised by hyperglycaemia, hyperosmolarity, dehydration (may lead to shock and hypotension) and excess ketone body production resulting in an anion gap metabolic acidosis.

Metabolic Response to Surgery and Diabetes Management

– restore intravascular volume

– eliminate ketonaemia

– control blood glucose

– replace electrolytes

– monitor glucose and ketone levels

Mortality from DKA –5-10%

Electrolyte abnormalities

– Anticipate imbalances in potassium, magnesium and phosphate

Underlying Cardiac Complications of Diabetes and Surgery Cardiovascular problems frequently present in long standing

diabetics

– Ischaemic Heart Disease - Often silent ischaemia

– Coronary artery disease

– Hypertension

Diabetic patients must be considered as being at high risk of MI

Silent MI in autonomic neuropathy as Cardiac Autonomic Neuropathy may abolish the hearts response to stress

Induction of anaesthesia and tracheal intubation can lead to a

reduction in cardiac output

Underlying Cardiac Complications of Diabetes and Surgery

Management– Most cardiac and antihypertensive drugs should

be continued throughout the perioperative period except, aspirin, diuretics and anticoagulants

– 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

Underlying Renal Complications of Diabetes and Surgery Renal

– Renal dysfunction

• Intrinsic renal disease including glomerulosclerosis and renal papillary necrosis enhance the risk of acute renal failure perioperatively

• Proteinuria is an early manifestation

• Dialysis should optimally be done the day before surgery.

– Urinary infection

– Management

• Urea and electrolyte determination.

• Dipstix urinalysis for proteinuria

Underlying Nervous System Complications of Diabetes and Surgery Nervous System

– Counter-regulatory response to hypoglycaemia

– Peripheral glove and stocking neuropathy with an increased susceptibility to iatrogenic nerve injuries

– Cardiac Autonomic Neuropathy Management

– History of postural dizziness, post gustatory sweating, nocturnal diarrhoea and impotence.

– Careful documentation of peripheral sensation

Underlying Orthopaedic Complications of Diabetes and Surgery Small Joint Disease

Non-enzymatic glycosylation causing abnormal cross-linking of collagen may lead to joint rigidity

At the atlanto-occipital joint, it may result in difficult intubation

The small joints of the fingers and hands are also affected

– failure to approximate the palmar surfaces of the interphalangeal joints are indicators of a difficult laryngoscopy (positive prayer sign)

Management

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

Underlying Immune Complications of Diabetes and Surgery Immune and infectious risk

– Diabetics are susceptible to infection and have delayed wound healing

– Hyperglycaemia

• facilitates proliferation of bacteria and fungi

• depresses the immune system management

– Proteolysis and decreased amino acid transport retards wound healing.

– Loss of phagocytic function increases the risks of post-operative infection

Management

– Need very strict sterile techniques and need to assess risk/benefit ratio for procedures e.g catheterisation

Underlying Gastrointestinal and Opthamological Complications of Diabetes and Surgery Gastrointestinal

– Gastroparesis

Management

– History of early satiety and reflux

– H2 blocker and metoclopramide

Ophthalmology

– Cataracts, glaucoma and retinopathy decrease visual acuity and increase the unpleasantness of the perioperative period

Management

– Increase the amount of explanation and reassurance to the patient.

Principles of Managing Diabetics During Surgery

Management of preoperative insulin therapy depends on baseline blood glucose, level of diabetic control, severity of illness and the proposed surgical procedure

However, aims for all diabetic patients are:

– No excess mortality

– No increase in post-op complications

– Normal wound healing

– No increase in duration of hospitalisation

– No hypoglycaemia, hyperglycaemia or ketoacidosis

Pre-operative Assessment This is the most important step in the management of the

diabetic patient Involves a thorough history and physical examination Review prior anaesthetic records to determine whether

there were any difficulties with intubation or anaesthetics Lab investigations

– blood glucose - K+

– BUN - creatinine

– ketones - proteinuria

– HbA1c (to assess how well controlled diabetes is)

Pre-Operative Management Admit as early as possible prior to surgery Avoid long-acting glucose lowering agents

– chlorpropamide –glibenclamide– ultralente insulins

Avoid metformin Closely monitor blood glucose levels

– 2 hourly for Type 1

– 4 hourly for type 2 Test urine every 8 hours for ketones Place first on morning operating list if possible Aim for a blood glucose of 5-10mmol/L

Surgical Management of Insulin Dependant Diabetes Mellitus Aim to keep blood glucose 5 to10mmol/L Pre operative

– NBM for 6 hrs prior to surgery (4 hrs for clear fluids)– Anti aspiration prophylaxis– Initiate glucose/ potassium/ insulin regime after commencing NBM (check

K+ as well)• 500ml 10% glucose solution with 20mmol K+ at 1ml.kg-1.hr-1 connected

to Y piece with insulin syringe

• Make up insulin syringe as 50 units insulin in 50 ml saline in a 50 ml syringe pump and run through Y piece with 10% glucose at between 1 to 5 u hr-1 (1 – 5 ml).

• Base on existing insulin regime

• Use sliding scale e.g. 1 u hr-1 if BG between 5 to 10

– Hourly capillary glucose is measured until operation

Surgical Management of Insulin Dependant Diabetes Mellitus Intra-operative

– Hourly glucose monitoring• keep between 5-10 mmol/L

– Two hourly potassium monitoring• keep between 3.5-4.5 mmol/L

– Anaesthesia determined by patient physiology and surgical requirements

– Set up additional IV for resuscitation fluids

Surgical Management of Insulin Dependant Diabetes Mellitus Post-operative

– Continue Glucose/Potassium/Insulin regime until patient can take orally

– Oral medication with first meal– Allow for pain resulting in increased insulin

requirements

Surgical Management of Non Insulin Dependant Diabetes Mellitus Treat as insulin dependant if:

– poorly controlled (blood glucose >10 mmo/L) – major surgery

Pre-operative– Biguanides must be stopped 48 hours before hand for fear

of lactic acidosis

NBM for 12 hours prior to operation

Start i.v maintenance fluid

– 0.18% NaCl with glucose 4%

Hourly capillary glucose is measured until operation

Surgical Management of Non Insulin Dependant Diabetes Mellitus

Hourly glucose monitoring– Aim to keep within 5-10mmol/L– if blood glucose >10 mmol/L, switch to

treating as insulin dependant Post-operative

– Restart oral hypoglycaemics with first meal

Other Considerations with Anaesthesia in Diabetic Patients Usual intra-operative monitoring

– record BP and pulse every 5 minutes

– watch skin colour and temp

• suspect hypoglycaemia if patient is cold and sweaty

– give IV glucose

No contraindications to standard anaesthetic induction or inhalational agents

If the patient is dehydrated then hypotension will occur and i.v. fluids will be needed

Conclusion

The diabetic patient presents numerous challenges to management during surgery

Awareness of the complications should enable tight metabolic control

Correct management of the diabetic patient during surgery reduces morbidity and length of admission, as well as resulting in better wound healing