Rationale

Diabetes is associated with an increased need for surgical procedures and invasive investigations and higher morbidity than non-diabetics. Anaesthesia and surgery are associated with a complex metabolic and neuroendocrine response that involves the release of counter-regulatory hormones and glucagon leading to insulin resistance, gluconeogenesis, hyperglycaemia and neutrophil dysfunction, which impairs wound healing. This response also occurs in people without diabetes but is more pronounced and difficult to manage in people with diabetes. Advances in diabetes management, surgical techniques, anaesthetic medicines and intensive care medicine have significantly improved surgical outcomes for people with diabetes.

Introduction

People with diabetes undergo surgery for similar reasons to those without diabetes; however, because of the long-term complications of diabetes they are more likely to require:

Cardiac procedures:
Angioplasty or stents
Bypass surgery
Ulcer debridement, amputations (toes, feet)
Eye surgery such as cataract removal, repair retinal detachment, vitrectory
Carpal tunnel decompression.

Surgery induces a stress response that results in endocrine, metabolic and long-term effects that have implications for the management of people with diabetes undergoing surgery, see Table 9.1. Stress induces hyperglycaemia, which causes osmotic diuresis, increased hepatic glucose output, lipolysis and insulin resistance. Unless controlled, surgical stress increases the risk of DKA, HONK, and lactic acidosis (see Chapter 7), infection, impaired wound healing, and cerebral ischaemia. The risk of HONK is high in procedures such as cardiac bypass surgery and has a high mortality rate (Dagogo-Jack & Alberti 2002).

Table 9.1 Hormonal, metabolic, and long-term effects of surgery.

Hormonal	Metabolic	Long-term effects if optimal blood glucose control achieved
↑Secretion of^a epinephrine, norepinephrine, ACTH, cortisol and growth hormone	Catabolic state and ↑ metabolic rate Hyperglycaemia Insulin resistance	Loss of lean body mass – impaired wound healing, ↓ resistance to infection Loss of adipose tissue
↓secretion of insulin due to impaired beta cell responsiveness	↓Glucose utilisation and glycogen storage	Deficiency of essential amino acids, vitamins, minerals, and essential fatty acids
Insulin resistance	↑Gluconeogenesis	Surgical complications
	↑ Protein catabolism and reduced amino acid and protein synthesis in skeletal muscle
	↑Lipolysis and formation of ketone bodies
	↓Storage of fatty acids in the liver
	Osmotic diuresis with electrolyte loss and compromised circulating volume
	↑Risk of cerebrovascular accident, myocardial arrhythmias infarction electrolyte disorders
	↑Blood pressure and heart rate
	↓Peristalsis

^a Norepinephrine is mostly augmented during surgery and epinephrine postoperatively. Stress stimulates glucagon secretion from the pancreatic alpha cells and together with growth hormone and cortisol, potentiates the effects of norepinephrine and epinephrine. Cortisol increases gluconeogenesis.

In addition, anaesthesia and surgical stress, as well as medicines, induce gastrointestinal instability that can compound gastric autonomic neuropathy and lead to nausea, vomiting and predispose the individual to dehydration and exacerbates fluid loss via osmotic diuresis and blood loss during surgery. As a result, electrolyte changes particularly in potassium and magnesium, increase the risk of cardiac arrhythmias, ischaemic events, and acute renal failure (Dagogo-Jack & Alberti 2002). The risk is particularly high in those with chronic hyperglycaemia, existing diabetes complications, older people, and those who are obese. All of which are associated with increased risk of postoperative complications (Dickersen 2004).

Obesity is associated with functional risks in addition to the metabolic consequences of surgery that need to be considered when positioning the patient. The respiratory system is affected and functional residual capacity and expiratory reserve volume may be reduced possibly due to excess weight on the chest wall and/or displacement of the diaphragm. Severe obesity can lead to hypoventilation and obstructive sleep apnoea. These factors predispose the individual to aspiration pneumonia. Various cardiac changes increase the risk of heart failure and inadequate tissue oxygenation. In addition, the risk of pressure ulcers is increased due to the weight, and activity level is often compromised increasing the risk of venous stasis and emboli.

The need for nutritional support may be overlooked in obese individuals and protein deprivation can develop because protein and carbohydrate are used as the main energy sources during surgery rather than fat. In addition, energy expenditure is higher due to the increase in lean body mass, which impacts on wound healing (Mirtallo 2008).

Different types of surgery present specific risks as do the age of the person, with the very young and older people being particularly at risk. These effects are summarised in Table 9.1. These factors must be controlled in order to prevent DKA and HONK, promote healing and reduce the risk of infection postoperatively. Hyperglycaemia inhibits white cell function and increases coagulability (Kirschner 1993).

Surgery is often performed as a day procedure often without appropriate consideration of the effects of surgical and the related psychological stress on metabolic control. A multidisciplinary approach to planning is important.

The magnitude of the metabolic/hormonal response depends on the severity and duration of the surgical procedure, metabolic control before, during, and after surgery, and the presence of complications such as sepsis, acidosis, hypotension, and hypovolaemia (Marks et al. 1998). Metabolic disturbances can be present in euglycaemic states (De & Child 2001).

Aims of management

(1) To identify underlying problems that could compromise surgery and recovery.

(2) To achieve normal metabolism by supplying sufficient insulin to counterbalance the increase in stress hormones during fasting, surgery, and postoperatively (blood glucose between 5 and 7 mmol/L) and avoid the need for prolonged fasting.

(3) To achieve this with regimens that minimise the possibility of errors.

(4) To supply adequate carbohydrate to prevent catabolism, hypoglycaemia, and ketosis.

(5) To ensure that the patient undergoes surgery in the best possible physical condition.

(6) To prevent:

hypoglycaemia, children <5 years are prone to hypoglycaemia during anaesthesia and surgery (Kirschner 1993)
hyperglycaemia predisposing the patient to dehydration, electrolyte imbalance, ketoacidosis, and hyperosmolar states
complications of surgery
electrolyte imbalance
worsening of pre-existing diabetic complications
infection.

(7) To avoid undue psychological stress.

Preoperative nursing care

Good preoperative nursing care is important for both major and minor procedures. Preadmission clinics have an important role in identifying and managing preventable surgical risks. Sometimes people need to be admitted 2–3 days before major surgery to stabilise blood glucose levels and manage complications, see Table 9.2. Because many procedures only require a day admission, careful explanation about what is required and written instructions about medication adjustment/withdrawal are vital.

The individual’s blood glucose profile needs to be reviewed and their diabetes regimen may need to be adjusted prior to surgery to achieve good control. Erratic control could indicate the presence of infection that should be treated prior to surgery. If possible, schedule for a morning procedure to avoid the need for prolonged fasting and counter-regulatory hormone release that leads to hyperglycaemia.

Nursing actions

(1) Confirm time of operation.

(2) Explain procedure and postoperative care to the patient and/or family members if appropriate for example a child. Those patients controlled OHAs may require insulin during surgery and immediately post-operatively. They should be aware of this possibility. Insulin during the operative period does not mean that diet- or tablet- controlled patients will remain on insulin when they recover from the procedure. People controlled by diet and exercise with good metabolic control may not require an IV insulin infusion for minor procedures but 1–2 hourly blood glucose monitoring is necessary. If control is suboptimal, and for procedures longer than 1 hour, an IV insulin/dextrose infusion is advisable (Dagogo-Jack & Alberti 2002). It should be noted that suboptimal control is common in diet-treated individuals.

(3) Ensure all documentation is completed:

consent form
medication chart
monitoring guidelines
chest X-ray and other X-rays, scans, MRI (magnetic resonance imaging)
ECG.

(4) Sulphonylureas are usually ceased 24 hours preoperatively and metformin and chlorpropamide 36 hours preoperatively. Check medical orders. Metformin should be withdrawn 3 days before surgery because any deterioration in renal function predisposes the patient to lactic acidosis (Gill 1997), see Chapter 7. However, some experts recommend continuing OHA up until surgery to counteract surgical stress (French 2000) depending on the extent of the surgery, diabetes type, and usual blood glucose control. Insulin therapy must be initiated before the procedure in people with Type 1 diabetes.

Table 9.2 Common diabetic complications that can affect surgery and postoperative recovery. Many of these conditions may be documented in the person’s medical record and they may undergo regular complication assessment but health status can change rapidly especially older people. Therefore, the current complication status should be assessed prior to surgery. Hyperglycaemia must be controlled.

Complication	Possible consequences	Preoperative evaluation
Cardiovascular	Hypertension Ischaemic heart disease Cardiomyopathy Myocardial infarction, which can be ‘silent’ and in the presence of autonomic neuropathy cause sudden tachycardia, bradycardia, and/or postural hypotension Cerebrovascular disease. Increased resting heart rate is associated with increased risk of death in older people. Daytime sleepiness is associated with 4.5-fold increased risk of stroke and other vascular events.	Careful history and examination ECG Manage existing conditions such as heart failure Assess for silent cardiac disease autonomic neuropathy, indicators include; Shortness of breath, palpitations, ankle oedema, tiredness, and atypical chest pain. Assess resting heart rate. Ask about daytime sleepiness or assess formally, for example, using the Epworth Sleepiness Scale (ESS).
Neuropathy
Autonomic	Cardiac as above Inability to maintain body temperature during anaesthesia	Lying and standing blood pressure (abnormal if decrease >30 mmHg)
Peripheral	Pressure areas on feet and ulceration Foot infection Falls post operatively	Heart rate response on deep breathing (abnormal if increase >10 beats/min). Foot assessment, assess for active and occult infection and signs of neuropathy.
Renal	Nephropathy, which may affect medication excretion. Urinary tract infection (UTI), which may be silent and predispose to sepsis Acute renal failure and the need for dialysis. UTI if catheterisation is needed. Obese people and smokers are prone to chest infections Obesity may be associated with reduced respiratory reserve and displacement of the diaphragm	Urine culture to detect UTI, which should be treated with the relevant antibiotics Microalbuminuria and creatinine clearance, eGFR Blood electrolytes, correct potassium >5 mmol/L before surgery. Counsel to stop smoking Chest physiotherapy Chest X-ray
Respiratory	Reduced tissue oxygenation.	Blood gases
Airway	Soft tissue, ligament, and joint thickening that might involve the neck making it difficult to extend the neck and intubate and predispose the individual to neck injury and post operative pain	Nebulised oxygen pre and postoperatively if indicated See test for musculoskeletal disease (see page 265) Take extra care of the neck
Gastrointestinal	Autonomic neuropathy leading to gastric stasis delayed gastric emptying, gastric reflux, regurgitation and aspiration on anaesthesia induction Ileus May need to modify nutritional support if required postoperatively and given enterally.	Assess history of heartburn or reflux and whether the person sleeps in an upright position A H2 antagonist and metclopramide might be indicated preoperatively Erratic food absorption can affect blood glucose levels
Eyes	Cataracts, glaucoma, and retinopathy can be exacerbated by sudden rise in blood pressure	Assess retinopathy stage.
Neutrophil dysfunction	Increased risk of infection Inability to mount an appropriate response to infection	Check for possible foci of infection: including feet, teeth, and gums, UTI, Ensure optimal blood glucose control Optimise vascular function.
Polypharmacy	Risk of medicine interactions with anaesthetic agents and postoperative medicines Risk of lactic acidosis with metformin Some medicines increase the risk of hyperglycaemia some hypoglycaemia	Medicine review Ask about complementary medicines Give the person clear, concise written instructions about how to manage their medicines preoperatively and postoperatively on discharge
Musculoskeletal	Difficulties with intubation and tube placement. Falls risk	Assess, for example, prayer sign, Dupuytren’s contracture, trigger finger Foot abnormality including Charcot’s foot
Obesity	Increased systemic vascular resistance leading to reduced tissue oxygenation and increased risk of lactic acidosis in people on metformin especially if renal function is compromised and those with surgical wound infections. Sleep apnoea and associated daytime sleepiness with associated risk of cardiovascular events. Difficulty intubating the person Assumption that the person is well nourished when in fact nutritional deficiencies especially protein are common. High prevalence of hypertriglyceridaemia Cardiovascular and respiratory effects, which affect postoperative nutrition support if it is required. Non-alcoholic fatty liver Risk of pressure ulcers	Assess nutritional status Assess cardiovascular and respiratory status. Ask about daytime sleepiness or assesss formally, for example, using the ESS. Skin condition

(5) Encourage patients who smoke to stop.

(6) Assess:

metabolic status: blood glucose control, ketones in blood and urine, hydration status, nutritional status, presence of anaemia, diabetic symptoms
educational level and understanding of diabetes
family support available postoperatively
any known allergies or medicine reactions, which should include asking about complementary therapies, particularly herbal medicines, because some herbs predispose the person to haemorrhage and/or interact with anaesthetic agents and should be stopped at least 7 days prior to surgery (see Chapter 19)
presence of diabetic complications and other comorbidities, for example, renal, hepatic, cardiac disease (ECG for people >50 years to detect the risk of silent infarction is performed in some units), presence of neuropathy. Patients with autonomic neuropathy pose special problems during anesthesia: gastroparesis delays gastric emptying and the stomach can be full despite fasting and increases the possibility of regurgitation and inhalation of vomitus; or the vasoconstrictive response to reduced cardiac output may be absent and they may not recognise hypoglycaemia
current medication regimen
presence of infection, check feet and be aware of silent infection such as UTI.
self-care potential and available home support.

Note: Complications should be managed before the operation where possible, see Table 9.2.

Major procedures

Major surgery refers to procedures requiring anaesthesia and lasting longer than 1 hour (Dagogo-Jack & Alberti 2002).

Day of the operation

Premedication and routine preparation for the scheduled operative procedure should be performed according to the treatment sheet and standard protocols.

Where insulin is required, for example, Type 1 diabetes, major surgery, and poor control, an IV insulin infusion is the preferred method of delivering the insulin. The insulin dose should be balanced with adequate calories to prevent starvation ketosis, for example, saline/dextrose delivered at a rate that matches the insulin dose (Alberti & Gill 1997), see Chapter 5. Fluid replacement should be adequate to maintain intravascular volume; normal saline/dextrose in water is the preferred solution for this purpose. Preoperative hyperglycaemia especially if polyuria is present can cause significant fluid deficits and intracellular dehydration. Clinical signs of dehydration are:

Thirst and a dry mouth: water loss <5% of body weight.
Capillary refill >2 seconds (normal <2 seconds), reduced skin turgor, sunken eyes, reduced urine output, orthostatic hypotension, fainting on standing, low CVP/JVP: water loss 5–10% of body weight.
Unconscious or shock: water loss >10% of body weight (French 2000).

Morning procedure

(1) Ensure oral medications were ceased.

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