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Fluid andnutrition management 15

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Prescribing uids forthe surgical patient

The majority of patients require fluid replacement for only a brief period postoperatively until they resume a normal diet. Some require resuscitation preoperatively, and others require replacement of specific losses such as those from a fistula. In severely ill patients, and those with impaired gastrointestinal function, long

- term nutritional support is necessary.

Preoperative uid management

Patients awaiting elective surgery can continue clear fluids up to 2 hours before surgery, unless they have a disorder affecting their gastric emptying (e.g. carcinoma of head of pancreas; diabetes mellitus). Preoperative carbohydrate drinks, 2–3 hours before surgery, have been shown to reduce preoperative anxiety and postoperative nausea and vomiting and are now routine adjuncts to preoperative care in elective surgery.

Intravenous uid management

Assessment offluid requirements

Assessment of fluid requirements involves history and examination.

History

• Sensation of thirst: implies at least 2% volume depleted

•

Fluid balance: what were the previous fluid intake

and losses?

• Abnormal losses and their nature, e.g. nasogastric output

Examination

• Pulse– Is there a tachycardia?

• Jugular venous pressure – Is the pressure wave visible, and if so, how high is it raised?

• Capillary refill– should be less than 2 seconds.

•

Skin turgor.

• Blood pressure– Is there a postural fall?

•

Is there evidence of fluid overload? Pulmonary

oedema or peripheral oedema.

• Weight, useful to monitor losses. Minimum of twice a week.

• Urine output– hourly monitoring in early postoperative or shocked patients; daily outputs in maintained patients. Daily collections are often not accurate, hence daily weights may be preferred.

Special investigations

• Full blood count – a high haemoglobin may represent haemoconcentration.

•

Urea, creatinine and electrolytes – important to

ensure the correct electrolyte replacement to cover losses; raised urea may represent either renal impairment (creatinine also raised), dehydration or blood in the gut.

• Urinary sodium – useful in the presence of high volume gastrointestinal losses. Reduced urinary sodium excretion (<30 mmol/L) suggests total body sodium depletion. These measures are not reliable in the presence of renal impairment or diuretic usage.

Serum chloride – useful in patients receiving a lot

• of normal saline to avoid hyperchloraemia. If present, saline needs to be switched to an alternative fluid with less chloride.

• Drain fluid electrolytes – where there are persistently high fluid losses, for example, from high fistulas, it may help to measure the electrolyte content to better judge the replacement fluid needs.

Resuscitation

Thirst, dry mucous membranes, loss of skin turgor, tachycardia and postural hypotension, together with a low jugular venous pressure, suggest a loss of between 5% and 15% of total body water. Fluid losses of under 5% body water are difficult to detect clinically; over 15%, there is marked circulatory collapse.

Fluid replacement in adults should comprise a crystalloid with a high sodium content (130–154mmol/L, e.g. Hartmann’s or 0.9% saline; Table3.2), with a bolus of 500mL over less than 15minutes. Human albumin 4–5% solution may be considered for fluid resuscitation only in patients with severe sepsis. Following a fluid challenge, the patient should be reassessed– did the pulse fall and the jugular venous pressure (JVP) rise, and did the hourly urine output increase?

As an example, consider a 70kg man presenting with a perforated peptic ulcer. On examination, he is noted to have dry mucous membranes, a tachycardia and slight postural fall in arterial blood pressure. If the loss is estimated at 10% of the total body water, itself 60% of the body weight, the volume deficit is 10% × 60% of 70kg, or 10% of 42L = 4.2L. This loss is largely isotonic (gastric juices and the peritoneal inflammatory response), hence infusion of a balanced crystalloid solution (e.g. Hartmann’s solution) is appropriate. A general rule of thumb is to replace half of the estimated loss quickly and then reassess before replacement of the rest.

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Routine maintenance fluids

Table 3.1 shows the normal daily fluid losses. Replacement of this lost fluid in a typical adult is achieved by the administration of:

• 25– 30mL/kg/day of water

•

1mmol/kg/day potassium, sodium and chloride

•

50–100 g/day glucose to limit starvation ketosis–

N.B.: this does not meet nutritional needs.

dextrose only contains 50g/L dextrose.

5%

Special considerations

• Obese patients: adjust the intravenous (IV) fluid prescription to their ideal body weight.

Renal failure: adjust the volume to urine output

• plus insensible and special losses with care when prescribing potassium as this is not excreted in renal failure.

• Cardiac failure and the elderly and frail: these patients are prone to accumulate fluid in the lungs.

•

Malnourished– see later. These patients are at risk

of refeeding syndrome.

A typical prescription would be 25–30 mL/kg/day

0.18% saline in 4% dextrose with 1mmol/kg potassium.

Therefore, for a 70kg man, this may comprise 3L of 4% dextrose/0.18% saline (31 mmol NaCl per litre), with 20 mmol potassium added to each 1 L bag (Table3.2).

Excessive amounts of hypotonic crystalloid may cause hyponatraemia, particularly in children and the elderly. An alternative regimen involves the use of Hartmann’s solution (Table3.2). Adjustments to the fluid regimen should be based on regular clinical examination, measurement of losses (e.g. urine output), daily weights (to assess fluid changes) and regular blood samples for electrolyte determination. For example, if the patient is anuric, 1 L/day of 5%dextrose without potassium may suffice.

Replacement ofspecial losses

Special losses include nasogastric aspirates, losses from fistulas, diarrhoea and stomas, and covert losses such as occur with an ileus (Figure3.1). Loss of plasma in burns is considered elsewhere (Chapter 10). All fluid losses should be measured carefully when possible, and this volume added to the normal daily requirements. The composition of these special losses varies, but as a rough guide, replacement of excessive gastric fluid loss with an equal volume of normal

Table3.2 Electrolyte content ofintravenous fluids

Intravenous infusion

Osmolarity 275–295 308 283 278 295 290 300

pH 7.35–7.45 4.5-

(mmol/L) 135–145 154 31 131 140 145 150

K+ (mmol/L) 3.5–5 5 5

Ca2+ (mmol/L) 2.2–2.6 2

Mg2+ (mmol/L) 0.8–1.2 1.5

Cl– (mmol/L) 95–105 154 31 111 98 145 150

Glucose (mmol/L)

Lactate (mmol/L) 1.0–2.0 29

–

(mmol/L) 23–27

HCO

Acetate (mmol/L) 27

Gluconate (mmol/L)

Note: Dextrose is the D- isomer of glucose, the only isomer that can be metabolized. Dextrose/saline combinations come in varying mixtures, including 4% dextrose, 0.18% saline, so the mixture must be specified clearly.

Human plasma

3.5–5.5 222 (40g)

0.9% saline

4% dextrose*

0.18% saline Hartmann’s

7.0 4.5 5.0–7.0 6.5–8.0

PlasmaLyte 148

4% gelatine

5% albumin

Fluid andnutrition management 17

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saline with extra potassium supplements should suffice; similarly, losses from diarrhoea, ileostomy, small bowel fistulas and ileus should be replaced with Hartmann’s solution. Biochemical analysis of the electrolyte content of fistula drainage may be useful.

Nutrition

The catabolic response tosurgery

Surgery elicits a stress and inflammatory response, which causes catabolism of glycogen, fat and protein. The stress response is proportional to the magnitude of surgical trauma and is necessary to achieve healing and recovery, but without sufficient nutritional reserve or support, poor outcomes are more likely. Measures to reduce the stress of surgery, such as enhanced recovery programs, have been shown to minimize catabolism, improve recovery and reduce complications of surgery.

Malnutrition andmalnutrition risk

Many patients are well nourished and recover good dietary intake quickly after surgery and, therefore, do not require nutritional support. Some patients are malnourished prior to surgery or at risk of becoming malnourished following surgery.

Malnutrition is a state in which a deficiency of nutrients, such as energy, protein, vitamins and minerals, causes adverse effects on body composition, function or clinical outcome. Malnutrition lowers resistance to infections, impairs wound healing, delays functional recovery and increases postoperative mortality.

Risk factors formalnutrition

Patients at risk of malnutrition include those with health conditions that affect appetite, nutrient absorption and metabolism, such as Crohn’s disease, gastrointestinal cancer, end cystic fibrosis. Dysphagia, social isolation, low income and older age are also risk factors for malnutrition. Surgery itself is a risk factor for malnutrition, particularly major or complicated surgery.

- stage liver disease and

Universal Screening Tool (MUST should be screened on admission to hospital and screening repeated weekly. Patients at risk of malnutrition must commence a nutrition treatment plan, which should include referral to a dietitian for those at high risk.

). All patients

Diagnosing malnutrition

Tools to diagnose malnutrition, such as the Subjective Global Assessment (SGA trition risk has been identified. Malnutrition may be less obvious in patients living with obesity but equally important to identify and treat as for patients with a lower body mass index (BMI).

Malnutrition can be diagnosed based on a combination of phenotypic and aetiologic criteria, for example:

• Weight loss of >5% within past 6months, or >10%

beyond 6months.

BMI < 20kg/m

•

<22kg/m

• Reduced muscle mass based on body composition

methods, including imaging, physical examination, or anthropometric measures such as mid muscle circumference (MAMC). Functional assessment, such as handgrip strength, can support assessment as loss of muscle mass is often preceded or accompanied by reduced muscle function.

Reduced food intake or absorption.

•

• Disease burden and inflammation.

aged 70 years or older.

), can be used when malnu-

in those under 70 years of age or

- arm

Sarcopenia, cachexia andfrailty

Sarcopenia, cachexia, frailty and malnutrition are overlapping syndromes that can present in the same surgical patient and are associated with worse postoperative outcomes. The definitions of these syndromes are debated and evolving.

• Sarcopenia has been defined as low muscle mass

and function.

• Cachexia is a metabolic syndrome occurring with

underlying illness and characterized by loss of muscle with or without loss of fat.

Screening formalnutrition

Identifying patients at risk ofmalnutrition

There are validated screening tools to identify patients at risk of malnutrition, such as the Malnutrition

http://www.bapen.org.uk/screening- and- must/

must- calculator

Described in the Journal of Parenteral and Enteral

Nutrition, 1987;11:8- 13.

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• Frailty is characterized by loss of functional and cognitive reserves that increases vulnerability to adverse health outcomes.

Prehabilitation

Prehabilitation is the process of enhancing an individual’s capacity to withstand surgery. It has a multimodal approach, including medical optimization, exercise, nutrition support, and stress and anxiety reduction prior to surgery. Benefits include reduced length of stay and postoperative pain with fewer postoperative complications. Prehabilitation may be included as part of the Enhanced Recovery After Surgery (ERAS) service (see below). Prehabilitation nutrition support may include dietary counselling, treatment of malnutrition, weight management and improved glycaemic control. There may be a standardized period of oral nutritional supplement drinks and carbohydrate loading.

Enhanced recovery after surgery (ERAS)

Enhanced recovery programs aim to optimize pre- , intra- and postoperative care to improve recovery and shorten length of hospital stay for surgical patients. ERAS protocols include multimodal, evidence processes that modify the physiological and psychological responses to major surgery. The key include:

•

Preoperative counselling.

• Preoperative and early postoperative nutrition.

• Avoidance of prolonged fasting.

• Carbohydrate loading up to 2 hours preoperatively.

• Standardized anaesthetic and analgesic regimens (avoiding opiates where possible).

• Avoidance of surgical drains and tubes when possible.

• Avoidance of salt and water overload.

• Early, goal- orientated mobilization.

In addition, urinary catheters and nasogastric tubes

(if used) are removed as soon as possible after surgery.

- based

principles

Postoperative nutrition

Early postoperative nutrition should be part of routine care. If the gastrointestinal tract is functioning satisfactorily, oral intake is the preferred route for

nutritional support and can often be started as early as the first postoperative day. Early nutrition in abdominal surgery has been shown to enhance gastrointestinal function, reduce the risk of postoperative ileus and shorten length of stay, with no increased risk of postoperative complications.

Nutrition support is indicated for patients with malnutrition and those at risk of malnutrition. Artificial nutrition support should be initiated without delay for patients who are likely to be unable to eat for five days or who are anticipated to meet less than 50% of their nutritional requirements for seven days, for example, due to complications or prolonged intensive care unit (ICU) stay.

Nutrition support may be through a combination of food, oral nutritional supplements, fine bore nasogastric or nasojejunal tube, gastrostomy, jejunostomy or parenteral nutrition (PN), depending on the individual patient’s need. The oral and/or enteral route is the preferred method of nutrition. Post- pyloric feeding may be indicated in the presence of delayed gastric emptying. Feeding tubes such as gastrostomies and jejunostomies may be indicated if long feeding is anticipated. Local policies for feeding, including feeding routes, may exist for certain patient groups such as patients undergoing surgery for head and neck cancer.

Energy and protein requirements are calculated on an individual basis, depending on the patient’s gender, age, weight, BMI, weight changes, and stress and activity factors. Enteral feeding is usually started continuously over 20–24 hours and may be progressively weaned to support increasing oral intake of food. Formula is chosen based on individual patient requirements from a range, including standard whole protein formulas, with and without fibre, low volume, low electrolyte, high protein, elemental, high mediumchain triglycerides, and milk or lactose- free. Additional energy, protein and fibre boluses can be provided to help meet nutritional requirements.

- term tube

Parenteral nutrition

PN is administered, with guidance from the intestinal failure team, when nutrition cannot be provided through the gastrointestinal tract, for example, with gastrointestinal obstruction, high- output fistula, prolonged ileus or malabsorption. Combinations of enteral and parenteral nutrition should be considered, when possible, to help maintain gut integrity.

PN is usually administered via a catheter in a

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central vein because of the high osmolarity of the solutions used; there is a high risk of phlebitis in smaller veins with lower blood flow. Usual timing is continuous infusion over 24 hours, with cyclical PN (e.g. 12

- to 16- hour infusion) used more often for patients requiring long protein:fat:carbohydrate calorie ratio approximates to 20:30:50%, but the glucose:fat calorie ratio may be increased, for example, due to hyperlipidemia and fatty liver, which is sometimes accompanied by cholestasis. Commercially available ‘ready tion mixtures are commonly used with trace elements and vitamins added. Non known as ‘scratch’ or ‘tailored’ bags, can be made to exact specifications for amount of carbohydrate, fat, protein and electrolytes but vary according to physical and chemical stability, which is assessed by the PN pharmacist. PN is continued in the postoperative period until gastrointestinal function returns. Occasionally, parenteral feeding may be necessary on a long term or even lifelong PN at home.

- term basis, and some patients require long-

- term PN. Commonly, the

- made’ nutri-

- standard formulations,

Complications of PN

Complications of PN include:

•

Sepsis: use of dedicated lines inserted using aseptic

techniques, aseptic non- touch techniques when changing bags, and appropriate preparation and storage of feeds contribute to reducing rates of infection.

• Thrombosis: may occur on any indwelling venous

catheter and in patients requiring long- term PN; this is a major cause of morbidity. If ongoing parenteral feeding access is required, anticoagulation should be lifelong after a first episode of thrombotic venous occlusion. Consideration should be given to anticoagulation for all patients fed parenterally if at risk.

• Hyponatraemia.

• Hyperglycaemia is common and nearly always

requires insulin if the glucose infusion rate is to be maintained. If the calorie intake is not crucial, it may be possible to change the feed to one with lower glucose content.

Fluid andnutrition management 19

•

Liver damage: fatty liver. Encouraging enteral

intake, reducing the lipid load, ensuring maximum carbohydrate oxidation is not exceeded and giving cyclical PN may help correct liver function or prevent further dysfunction.

Refeeding syndrome

Refeeding syndrome is a range of life- threatening clinical and biochemical abnormalities that arise in response to nutrition delivery, including cardiac failure, pulmonary oedema, dysrhythmias, acute circulatory fluid overload or depletion, electrolyte derangement and hyperglycaemia. Refeeding syndrome develops because of the biochemical shift from starvation metabolism to fed metabolism. During refeeding there is a switch in metabolism from fat to carbohydrate with consequent insulin release, stimulated by the glucose load. Insulin release stimulates the sodium potassium ATPase pump (which requires magnesium as a cofactor). This drives potassium into the cells and sodium out. Carbohydrate load and insulin release stimulate phosphate shifts into the cells. Phosphate depletion is associated with increased urinary magnesium excretion. These phenomena lead to low extracellular phosphate, magnesium and potassium concentrations.

Enteral and parenteral feeding are more likely to precipitate refeeding syndrome. Risk factors include low BMI; little or no nutritional intake for 5 or more days; weight loss; low potassium, phosphate or magnesium prior to feeding; a history of alcohol excess; and a drug history, including insulin, chemotherapy, antacids or diuretics. Refeeding syndrome is managed through gradual introduction of nutrition; monitoring and replacement of electrolytes; vitamin supplementation; and monitoring fluid balance, pulse rate and clinical status.

Nutrition: Amultidisciplinary approach

Good nutritional care of the surgical patient requires a multidisciplinary approach. Referral to a dietitian is essential for patients with malnutrition or requiring nutrition support.

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Preoperative assessment

Hemantha Alawattegama

Learning objectives

✓ To be aware of the principles of preoperative assessment. ✓ To be able to identify and manage likely complicating factors prior to

surgery.

The pathway for patients from surgical consult to leaving hospital after their operation has changed significantly over time. The perioperative service now is a multi-

disciplinary team (MDT) of surgery, anaesthesia, medicine (involving elderly care specialists and other medical specialties, as needed), pharmacy, specialist nurses and allied healthcare professionals, including physiotherapists and dieticians, with the emphasis on shared decisionputs the patient at the centre of decision- making, who, with the clinicians, agrees on the optimal management based on evidence and the individual’s wishes and values. The norm for centres is to provide a formalized route of pre- assessment with a nurse- led and doctorsupported service. The surgeon’s role in this is imperative, as early identification, referral and intervention can significantly improve outcomes for patients. This involves taking a careful history, ensuring repeated assessment of patients while on a waiting list (for deterioration in health), reassessing the indication for surgery on the day of surgery admission and facilitating the patient to be as fit as possible for the procedure.

Fitness for a procedure needs to be balanced against urgency – the approach to a patient with an acute aortic rupture will be significantly different to an elective liver resection. Nevertheless, a careful assessment of the patient and identification of premorbid

making (SDM). This

conditions provides the best and safest care, allowing focused improvement of pre- existing conditions (when possible), planning of the surgical procedure and the postoperative pathway the patient will follow.

As part of the preoperative programme, Surgery Sch ools are group sessions to inform patients of what to expect when they come to hospital for their procedure. This is an excellent way of managing patient expectations, alleviating anxieties, informing health changes/adaptation and familiarizing with the environment they will be entering. It also allows patients to prepare for their admission and start beneficial lifestyle changes. These are run as face-

to- face group sessions and/or as online sessions.

All patients should complete a self- assessment screening, as a form of clinical triage, as soon as listed for a procedure, which will highlight those who require a greater ina multi- disciplinary pathway. This is aided by early referral to the Preoperative Assessment Service for patients who are thought to be high risk. All patients should undergo a nurse- led preoperative process with subsequent medical input, as required.

The surgical assessment process can be considered in terms of factors specific to the patient and to the operation.

depth assessment and referral to

Ellis and Calne’s Lecture Notes in General Surgery, Fourteenth Edition. Edited by Christopher Watson and Justin Davies. © 2023 John Wiley & Sons Ltd. Published 2023 by John Wiley & Sons Ltd. Companion website: www.wiley.com/go/Watson/GeneralSurgery14

Patient assessment

In assessing a patient’s fitness for surgery, it is worth going through the clerking process with this in mind.

Preoperative assessment 21

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History ofpresenting complaint

An emergency presentation may warrant an emergency procedure, so the assessment aims to identify factors that may be a problem during or following surgery. Some problems may be readily identifiable and treated in advance; for example, a history of vomiting or intestinal obstruction would indicate that fluid replacement is necessary, and this can be done swiftly prior to surgery.

In contrast an elective operation, given sufficient time from listing to surgery, can permit much greater levels of optimization in readiness for the procedure.

Past medical history

• Diabetes – whether controlled by insulin, oral

hypoglycaemics or diet, diabetes may be complicated by gastroparesis (gastric stasis), with a risk of aspiration on induction of anaesthesia despite a preoperative fast.

•

Respiratory disease – what is the nature of the

chest problem, and is the breathing as good as it can be or is the patient in the middle of an acute exacerbation? Does the patient have symptoms of sleep apnoea, and do they use continuous positive airways pressure (CPAP) at home? This may affect where the postoperative care can be delivered.

Cardiac disease – does the patient have angina,

•

and is this stable or unstable? Is there a history of a myocardial infarction, and what was the treatment? What is their exercise tolerance?

• Rheumatoid arthritis– may be associated with an

unstable cervical spine, so a cervical spine X- ray is indicated.

•

Sickle cell disease– homozygotes for haemoglobin

S are prone to sickle crises under general anaesthetic and postoperatively if they become hypoxic and/or dehydrated– liaison with the local sickle cell service is advisable. Current national guidelines no longer require a routine screening test for patients, but a family history must be sought.

Perioperative care ofthe elderly

Increasingly, we are faced with an ageing population and pre- existing cognitive impairment, Alzheimer’s and other neurological conditions (e.g. Parkinson’s disease) that increase the risk of delirium in the postoperative period. It is, therefore, vital that patients are screened to assess their cognitive function and

potential for the postoperative confusional state. Many

centres now run specific multi- disciplinary preoperative clinics for assessment of patients at risk, allowing planning for their care, which includes stratification of drugs, appropriate anaesthetic technique and appropriate postoperative environment.

Abrupt cessation of medication for Parkinson’s disease in the perioperative period can result in a rapid deterioration in function. The Parkinson’s disease specialist nurse should be informed of the admission allowing planning of the inpatient stay.

Frailty

Frailty is related to the ageing process by which multiple body systems lose their in- built reserves. Frail patients are vulnerable to adverse health outcomes, and understanding the challenges and modifying their perioperative course can result in significant improvements in outcomes. To assist this, there are several screening assessment tools developed that can be used, for example, the Clinical Frailty Scale. Referral to the perioperative MDT is essential for patients at risk.

Past surgical history

• Nature of previous operations – what has been

done before? What is the current anatomy? What problems were encountered last time? Ensure a copy of the previous operation note(s) is available.

• Complications of previous surgery, for example,

deep vein thrombosis, methicillin- resistant Staphylococcus aureus (MRSA) wound infection or wound dehiscence.

Past anaesthetic history

• Difficult intubation – usually recorded in the pre-

vious anaesthetic note, but the patient may also have been warned of previous problems.

•

Aspiration during anaesthesia – may suggest

delayed gastric emptying (e.g. due to diabetes), suggesting that a prolonged fast and airway protection (cricoid pressure) are indicated prior to induction.

• Suxamethonium apnoea – deficiency of pseudo-

cholinesterase resulting in sustained paralysis following the ‘short- acting’ muscle relaxant suxamethonium (Scoline). It is usually inherited

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(autosomal dominant), therefore there may be a family history.

Malignant hyperpyrexia – a rapid excessive rise in

• temperature following exposure to anaesthetic drugs due to an uncontrolled increase in skeletal muscle oxidative metabolism and associated with muscular contractions and rigidity, sometimes progressing to rhabdomyolysis; it carries a high mortality (at least 10%). Most of the cases are due to a mutation in the ryanodine receptor on the sarcoplasmic reticulum, and susceptibility is inherited in an autosomal dominant pattern, so a family history should be sought.

Social history

• Smoking – ideally, patients should stop smoking before any general anaesthetic to improve their respiratory function and reduce their thrombogenic potential.

• Alcohol – a history suggestive of dependency should be sought, and management of the perioperative period instituted using chlordiazepoxide to avoid acute alcohol withdrawal syndrome.

Substance abuse – in particular, a history of intra-

• venous drug usage should be sought, and appropriate precautions taken.

Medication

Most medications should be continued on admission. Drugs acting on the cardiovascular system should usually be continued and given on the day of surgery. The following are examples of drugs that should give cause for concern and prompt discussion with and between the surgeon and anaesthetist.

•

Oral anticoagulants (e.g. warfarin, dabigatran,

apixaban, rivaroxaban) – this is a balance between the risk of a thromboembolic event and perioperative bleeding. Due to the latter, when possible, these should be stopped before surgery. The indication for anticoagulation is important: a brief period without anticoagulation for atrial fibrillation is reasonable but not for mitral valve prosthesis. If continued anticoagulation is required, then convert to a low molecular weight heparin (LMWH) or unfractionated heparin (UFH) infusion (bridging therapy). Further discussion with cardiology and haematology specialists is essential where doubt exists.

Aspirin and clopidogrel cause increased bleeding

• by irreversibly blocking platelet activity and, therefore, need to be stopped 7–10days prior to surgery to reverse their effect.

– The risk of bleeding with aspirin (with the

exception of highnial and medullary canal surgery) is minimal, and the general guideline is to continue throughout the admission. Aspirin precludes neither the use of neuraxial blockade nor the timing of removal of neuraxial catheters in the postoperative period.

– Clopidogrel, a P2Y

ily in patients who have had a previous cerebrovascular incident, recent acute coronary syndrome or recent percutaneous coronary (or systemic) vascular intervention. Cessation of the drug will depend on the acuity of these events, the risk of an embolic or thrombotic event and the risk of surgical bleeding. Bridging therapy will allow some cover, but LMWH and UFH are not antiplatelet agents. If there is any doubt, a cardiology consultation is recommended.

– The combination of aspirin and clopidogrel is a

particular risk and is found primarily in patients within one year of percutaneous coronary intervention (PCI). After the initial year has passed, patients usually continue aspirin alone. The safety of discontinuing these should be discussed with the responsible cardiologist.

•

Oestrogen- containing oral contraceptive pill is

associated with an increased risk of deep vein thrombosis and pulmonary embolism; consideration should be given to stopping it at least 4weeks before surgery. The patient should be counselled on appropriate alternative contraception since an early pregnancy risks the teratogenic effects of some of the drugs used in the perioperative period. Progesterone only contraceptives have no additional thromboembolic risk.

• Steroids – all glucocorticoid- dependent patients are at risk of adrenal crisis as a consequence of surgical stress or illness, and if left untreated, this can be fatal. Patients in this group fall into three categories:

– Primary adrenal insufficiency – diseases of

the adrenal gland (failure of the hormoneproducing gland)

– Secondary adrenal insufficiency – deficient

adrenocorticotropin hormone secretion by the

risk cases such as intracra-

inhibitor, is used primar-

pituitary gland or deficient corticotropin-

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releasing hormone secretion by the hypothalamus (failure of the regulatory centres)

– Tertiary adrenal insufficiency– chronic admin-

istration of steroids (≥5mg/day for >1month) for other disease processes (This is by far the largest group of steroid-

All these patients require additional steroid

• support in addition to their background dosage. Hydrocortisone 100 mg by intravenous injection should be given at induction of anaesthesia in adult patients with adrenal insufficiency from any cause, followed by ongoing hydrocortisone replacement, until the patient can take double their usual oral glucocorticoid dose by mouth. This is then tapered back to their normal dose, depending on the complexity of surgery and gut function.

• Immunosuppression – patients are more prone to postoperative infection, and absorption of immunosuppression may be disturbed. Consideration for changing the medications during the perioperative period needs to be discussed with the supervising specialist team.

Diuretics– both thiazide and loop diuretics cause

• hypokalaemia. It is important to measure the serum potassium in such patients and restore it to the normal range prior to surgery.

• Monoamine oxidase inhibitors are not widely used nowadays but do have important side effects such as hypotension when combined with general anaesthesia.

receiving patients.)

Allergies

It is important to determine clearly the nature of any allergy before condemning a potentially useful drug to the list of allergies. For example, diarrhoea following erythromycin usually reflects its action on the motilin receptor rather than a true allergy, but a skin rash does suggest an allergy such that its use should be avoided. In particular, consider allergies to the following:

•

Anaesthetic agents.

•

Antimicrobial drugs. Skin preparation substances, for example, iodine

• and chlorhexidine.

•

Wound dressings, for example, sticking plaster.

•

Latex, present in operating gloves and urinary

catheters, for example. Such patients should be operated on with non- latex gloves, and silastic catheters should be used if necessary

Preoperative assessment 23

Management of pre- existing medical conditions

Diabetes

The aim should always be to minimize alteration of the patient’s normal medication pattern for diabetes, minimize the fasting period and maintain normoglycaemia (6–10 mmol/L). The following should be checked in a diabetic patient:

•

HbA1c (<69mmol/mol for elective cases).

• Urea and electrolytes.

•

Electrocardiogram (ECG) prior to surgery.

Variableused nowadays to control patients’ diabetes but may still be needed in emergency surgery, poorly controlled diabetes or where a prolonged postoperative period of ‘nil by mouth’ is anticipated.

an operating list and miss just one meal. Patients with diettive treatment, except glucose monitoring. With oral medications, the general rule is that those medications prone to causing hypoglycaemia (meglitinides and sulphonylurea) are omitted on the day of surgery (one dose), while most of the other preparations (e.g. metformin and pioglitazone) can be taken. The oral dose is recommenced once normal diet resumes.

cation of their treatment, depending on whether they are on a short- or long- acting insulin (or both).

Respiratory disease

Asthma

The degree of respiratory compromise can be readily assessed with a peak flowmeter. Many asthmatic patients will revert to reasonable peak flows between exacerbations, and in the quiescent phases, this may not be indicative of the degree of potential bronchospasm. Documentation of triggers and potential medications to avoid (e.g. non- steroidal anti- inflammatory drugs) and how well controlled the asthma is at present will inform the management.

sions for exacerbation of asthma, previous episodes

dose insulin infusions are less commonly

When possible, diabetic patients should be first on

controlled diabetes require no special preopera-

Patients on insulin require a more in- depth modifi-

Other points of history are previous hospital admis-

24 Preoperative assessment

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of ventilation for exacerbation (an indicator of severity) and the need for oral steroids to control symptoms – this may require steroid supplementation in the intra and postoperative period (see later). If time allows, modification of therapy with the addition of a short course of corticosteroids may be indicated– this should be discussed with the patient’s respiratory team.

Obstructive pulmonary disease

This is often more of a problem, since there is less reversibility and, even at the patient’s best, respiratory reserve might be poor. Consider whether regional anaesthesia is possible, and if not, whether the patient will require postoperative ventilation on an intensive care unit; consider whether the addition of epidural or spinal analgesia would allow better postoperative respiratory function by controlling pain and avoiding opiates. Optimization of therapy, cessation of smoking and physiotherapy both pre- and postoperatively have shown benefit.

Cardiac disease

Angina is not a contraindication to general anaesthesia provided it is stable. An indication of the severity of angina can be gauged by the frequency with which the patient uses glyceryl trinitrate (GTN) preparations for acute attacks, exercise tolerance and co- morbidities (e.g. diabetes). Scrutiny of the patient’s cardiac history will guide further preoperative referral and investigations.

Coronary artery revascularization (surgery or stent)

Patients who have had successful coronary artery bypass graft (CABG) or stents for ischaemic heart disease should have better cardiac function than they had prior to this. If CABG surgery or stenting was done some time previously, ascertain whether the patient’s symptoms have changed, particularly whether there is any recurrence of angina or breathlessness, suggesting that the graft(s) or stent may have thrombosed or the disease progressed.

Routine ECG may detect abnormalities at rest. To rule out significant cardiac disease, consider stressing the heart, such as with an exercise ECG, stress echocardiogram or radionuclide myocardial perfusion scan.

Local anaesthesia should be considered in all patients with a history of cardiac or respiratory disease.