Anaesthetic Pre-Operative Assessment

Introduction

Performing pre-operative assessments is one of the less glamorous — but genuinely important — duties of the junior doctor. This is probably because it does not carry the same sense of immediacy as responding to a cardiac arrest, nor does it engender the same tedium as completing seemingly endless administrative forms. However, when called upon to do it, it is frequently not done as well as it should be. This is because, as medical students, we are often taught the theory behind pre-operative assessment without being given a clear structure for how to perform one efficiently in practice.

As we all acknowledge, putting someone to sleep is a significant undertaking, and the whole point of the pre-operative assessment is to recognise and quantify that risk, and to reduce it as far as possible. The all-important question is: "Is this person as well as they can be?" If not, why not — and what can be done to optimise their condition before theatre?

This article aims to provide that clear structure. It is written primarily for FY1 and FY2 doctors performing ward pre-operative clerking, but the principles apply equally to any clinician involved in the surgical pathway. For further clinical resources, see consultant-surgeon.co.uk.

ASA Physical Status Classification

The American Society of Anesthesiologists (ASA) Physical Status Classification is the universally used system for grading a patient's pre-operative fitness. Although it is not the sole determinant of operative risk (the nature and urgency of the procedure must be weighed against it), it provides a standard language for communicating risk between clinicians. The junior doctor would not be expected to independently assign an ASA grade, but understanding the system is essential — it will regularly appear on anaesthetic charts, in operation notes, and in discussions with your consultant.

The suffix "E" is added to any grade for emergency surgery (e.g., ASA III-E). Emergency surgery substantially increases perioperative risk beyond the grade implied by the physical status alone.

History

Active Problems

Anaesthetic drugs exert a profound effect on the cardiovascular and respiratory systems, as does surgery itself. Therefore, the history must begin with a systematic enquiry into symptoms arising from these two systems:

• Chest pain (character, radiation, precipitants — is there active angina or unstable cardiac disease?)
• Breathlessness (at rest, on exertion — quantify exercise tolerance in metres or flights of stairs)
• Orthopnoea and paroxysmal nocturnal dyspnoea (PND) — suggest left ventricular failure
• Ankle swelling — suggests right heart failure or venous disease
• Palpitations — may indicate an arrhythmia requiring pre-operative assessment
• Cough and sputum production — note volume, colour, and consistency
• Wheeze — suggests reactive airway disease
• Recurrent chest infections

When any of these symptoms are present, they must be quantified and related to the patient's functional capacity and everyday life. This serves two purposes: it helps establish or confirm a diagnosis, and it identifies patients whose condition may need to be optimised before theatre. For example, a patient presenting for elective surgery who has a productive cough every winter, breathlessness on walking 100 metres, and regularly coughs up white sputum may have undiagnosed or sub-optimally managed COPD. It may fall to the junior doctor to identify this, order appropriate investigations, and initiate referrals — ensuring the patient arrives at theatre as well as they can be.

Past Medical History

Widen the net beyond cardiorespiratory systems to include all conditions that may affect anaesthesia or surgery. The following conditions should be asked about specifically and directly — they are commonly underreported when patients are simply asked "have you had any previous medical problems?"

Cardiovascular

• Angina and coronary artery disease — ask about recent episodes, stress tests, angiograms, stents (note: antiplatelet therapy implications)
• Previous myocardial infarction — when, and was it managed with stent or bypass grafting?
• Hypertension — how well controlled? Current medications?
• Congestive cardiac failure — which ventricle, current functional status?
• Valvular heart disease — stenosis or regurgitation? Any history of endocarditis? Antibiotic prophylaxis required?
• Arrhythmias — AF, SVT, heart block. Does the patient have a pacemaker or implantable cardioverter-defibrillator (ICD)?
• Peripheral vascular disease

Respiratory

• Asthma — how frequent are attacks? What are the triggers? What reliever and preventer medications? Any previous hospital admissions or ITU admissions for asthma?
• COPD — severity (mild, moderate, severe, very severe based on FEV₁). Home nebulisers or oxygen?
• Upper respiratory tract infection (URTI) — a current URTI significantly increases the risk of laryngospasm and bronchospasm during induction; elective surgery should be postponed for at least 2–4 weeks after recovery from a URTI, particularly in children.
• Obstructive sleep apnoea (OSA) — important risk factor for post-operative respiratory complications and difficult airway management. Does the patient use CPAP?
• Fibrotic lung disease, pulmonary malignancy

Gastrointestinal

• Gastro-oesophageal reflux disease (GORD) — increases the risk of pulmonary aspiration under anaesthesia. A rapid sequence induction (RSI) technique may be used to protect the airway.
• Liver disease — cirrhosis affects drug metabolism, coagulation (reduced clotting factor synthesis), and albumin levels.
• Peptic ulcer disease, inflammatory bowel disease

Renal

• Chronic kidney disease — affects drug clearance and dosing. Pre-operative eGFR is essential for major procedures.
• Patients on haemodialysis — timing of surgery relative to dialysis is important.

Neurological

• Stroke and TIA — recent events significantly increase perioperative cardiac and cerebrovascular risk.
• Epilepsy — ensure anti-epileptic medications are continued perioperatively.
• Spinal disease — relevant to positioning on the operating table and to the feasibility of regional anaesthesia (spinal/epidural).

Endocrine and Metabolic

• Diabetes — type and treatment method? There will be a local protocol for diabetic medication perioperatively (first-on-list, withhold oral hypoglycaemics, insulin sliding scale if necessary). Poorly controlled diabetes (HbA1c >69 mmol/mol / >8.5%) significantly increases the risk of wound infection and other complications; elective surgery should be deferred until glycaemic control is improved.
• Thyroid disease — uncontrolled hyperthyroidism can cause a thyroid storm perioperatively; hypothyroidism impairs drug metabolism and cardiovascular reserve.
• Adrenal disease — patients on long-term corticosteroids (equivalent to prednisolone ≥5 mg/day for more than 3 months) may have suppressed hypothalamic-pituitary-adrenal (HPA) axis function and will require perioperative steroid supplementation ("steroid cover") to prevent an Addisonian crisis. This is a frequently missed and potentially life-threatening omission.

Musculoskeletal

• Rheumatoid arthritis — this is a critically important finding. Rheumatoid arthritis can affect the atlanto-axial joint (the joint between C1 and C2 vertebrae), causing C-spine instability. Intubation involves extension of the neck, and in a patient with atlanto-axial subluxation this manoeuvre can cause spinal cord compression. Any patient with rheumatoid arthritis should have cervical spine X-rays (flexion and extension views) reviewed prior to a general anaesthetic. If there is any evidence of C-spine instability, further CT or MRI imaging — and potentially neurosurgical stabilisation — may be required. The atlantoaxial distance on a lateral cervical X-ray should be no more than 3 mm in adults. Always discuss with a senior.
• Ankylosing spondylitis — similarly causes spinal rigidity, which can make intubation and positioning difficult.
• Osteoarthritis — relevant to positioning on the operating table and the feasibility of spinal anaesthesia (L3/4 or L4/5 approach).

Other

• Pregnancy — a significant anaesthetic risk factor. Increases aspiration risk (delayed gastric emptying, raised intra-abdominal pressure), increases the risk of aortocaval compression in the supine position, and restricts the use of certain medications. Any woman of reproductive age should have a pregnancy test prior to elective surgery.
• Obesity (BMI >30) — associated with difficult airway management, increased aspiration risk, respiratory compromise, and DVT risk.

Previous Anaesthetic History

This section is often neglected but is of critical importance. Ask specifically:

• Has the patient been under general anaesthesia before? If so, when and for what procedure?
• Was there any difficulty with the anaesthetic — particularly with intubation or maintaining the airway? A history of "difficult intubation" must be clearly documented and communicated to the anaesthetist.
• Any awareness under anaesthesia? (Rare, but a recognised complication.)
• Any post-operative nausea and vomiting (PONV) — can guide choice of anaesthetic technique.
• Any adverse reactions to anaesthetic drugs?

Drug History

Most medications can be continued until the day of surgery, but several require specific attention:

• Anticoagulants — warfarin, direct oral anticoagulants (DOACs: apixaban, rivaroxaban, edoxaban, dabigatran), heparin. Timing of discontinuation depends on the procedure's bleeding risk and the patient's thrombotic risk. Local anticoagulation protocols should be followed; haematology input is often required for bridging decisions.
• Antiplatelet agents — aspirin, clopidogrel. Stopping clopidogrel in a patient with a recent coronary stent can precipitate in-stent thrombosis; this must be discussed with cardiology before discontinuation.
• Oral contraceptive pill and hormone replacement therapy (HRT) — increase DVT risk; the combined OCP is typically stopped 4 weeks before major surgery.
• Diabetic medications — oral hypoglycaemics (particularly metformin — risk of lactic acidosis if renal function deteriorates perioperatively) and insulin should be managed per local protocol.
• Steroids — as above; steroid cover must be planned. Patients should not be nil by mouth for their oral steroids without a parenteral equivalent being prescribed.
• MAOIs (monoamine oxidase inhibitors) — interact dangerously with pethidine (can cause serotonin syndrome) and with sympathomimetic drugs used during anaesthesia. Traditionally, MAOIs were stopped 2 weeks before surgery, but current guidance from the Royal College of Psychiatrists suggests that abrupt cessation carries its own risks and that management should be discussed with the patient's psychiatrist and the anaesthetist.
• Certain antibiotics — enzyme-inhibiting drugs such as metronidazole and some antifungals can affect the metabolism of anaesthetic agents.
• ACE inhibitors and angiotensin receptor blockers (ARBs) — associated with profound hypotension at induction; many anaesthetists prefer these to be withheld on the morning of surgery (check local policy).
• Always ask about herbal remedies and over-the-counter medications, as these are frequently omitted from drug histories.

Allergies

Document all allergies clearly, including the nature of the reaction (true anaphylaxis versus intolerance). Relevant allergies in the anaesthetic context include:

• Latex — relatively common; latex-free theatre environment should be arranged.
• Penicillin and other antibiotics — relevant to prophylactic antibiotic selection.
• Suxamethonium — suxamethonium apnoea (see family history section).
• NSAIDs — may limit post-operative analgesia options.
• Chlorhexidine — used widely in surgical preparation and IV equipment.

Family History

Ask specifically about reactions to anaesthetic agents in first-degree relatives — these are not spontaneously volunteered and can be life-saving to identify:

• Malignant hyperthermia (MH) — a rare, life-threatening pharmacogenetic disorder triggered by volatile anaesthetic agents (e.g., halothane, sevoflurane, desflurane) and by suxamethonium. It causes uncontrolled skeletal muscle metabolism, resulting in rapidly rising temperature, severe metabolic acidosis, hyperkalaemia, rhabdomyolysis, and cardiovascular collapse. It is inherited as an autosomal dominant trait (mutations in RYR1 or CACNA1S genes). Mortality without treatment is extremely high. Treatment is with dantrolene (a muscle relaxant that inhibits sarcoplasmic reticulum calcium release). A positive family history mandates a TIVA (total intravenous anaesthesia) technique avoiding all volatile agents and suxamethonium, and pre-operative referral to an MH unit for testing.
• Pseudocholinesterase deficiency (suxamethonium apnoea) — suxamethonium (a depolarising neuromuscular blocking agent commonly used for rapid sequence induction) is normally broken down within minutes by plasma pseudocholinesterase. In patients with reduced or abnormal pseudocholinesterase activity (inherited or acquired), paralysis is prolonged — the patient cannot breathe spontaneously at the end of surgery and may require prolonged ventilation on ITU. The family may describe a relative who "couldn't breathe for a long time" after an operation. Inherited as an autosomal recessive trait.

Social History

Enquire about:

• Smoking — document pack-year history. Active smokers have increased rates of postoperative pulmonary complications, impaired wound healing, and cardiovascular risk. Even 8 weeks of smoking cessation before surgery improves outcomes. Strongly advise cessation.
• Alcohol — document units per week. Heavy alcohol use causes hepatic dysfunction, coagulopathy, poor nutritional status, and altered drug metabolism. Acute alcohol withdrawal perioperatively can be life-threatening.
• Recreational drugs — cocaine increases cardiovascular risk perioperatively; chronic opioid use significantly complicates post-operative analgesia.
• Social circumstances — relevant to discharge planning, particularly for day-case surgery (needs a responsible adult escort).

Fasting Status

The patient must be appropriately fasted before anaesthesia to minimise the risk of pulmonary aspiration. Current guidelines (Association of Anaesthetists, 2021) for elective surgery in healthy adults are:

• Clear fluids (water, black tea or coffee without milk) — up to 2 hours before anaesthesia.
• Breast milk — up to 4 hours before anaesthesia (in infants).
• Solid food, non-human milk, formula — 6 hours before anaesthesia.

Chewing gum and sweets should be stopped at the same time as solid food. These are the minimum fasting times; in practice, patients are often fasted longer due to theatre list timing. Prolonged, unnecessary fasting (more than 6 hours for fluids) is harmful and should be minimised through good ward coordination.

Examination

Airway Assessment

Airway assessment is the most anaesthetically specific component of the examination and must not be omitted. A predicted difficult airway requires advance planning by the anaesthetist (videolaryngoscope, fibreoptic bronchoscope, or awake intubation technique). Several bedside tests are used:

Mallampati Classification (I–IV)

The patient sits upright with their mouth open maximally and tongue protruded, without phonating. The examiner assesses the oropharyngeal view:

• Class I — entire uvula, soft palate, fauces, and anterior and posterior tonsillar pillars visible. Predicts easy intubation.
• Class II — uvula visible but tonsillar pillars hidden by the tongue. Reasonable laryngoscopic view expected.
• Class III — only the soft palate and base of the uvula visible; tonsillar pillars and uvula tip obscured. Likely difficult laryngoscopy.
• Class IV — only the soft palate visible; the uvula cannot be seen at all. Predicts a very difficult or failed intubation.

Mallampati Class III and IV indicate a potentially difficult airway and must be clearly documented and communicated to the anaesthetist in advance.

Other Airway Assessment Parameters

• Mouth opening (inter-incisor distance) — less than 3 cm (two fingerwidths) suggests a restricted mouth opening that will impede laryngoscopy.
• Thyromental distance — the distance from the mentum (chin) to the thyroid notch with the neck fully extended. Less than 6 cm (three fingerwidths) predicts a difficult intubation (anterior larynx).
• Neck extension — assess the range of neck extension; reduced extension (e.g., due to cervical spondylosis, rheumatoid arthritis, or ankylosing spondylitis) impairs the laryngoscopic view.
• Dentition — note missing or loose teeth (dentures should be removed before anaesthesia), protruding upper incisors (can impede laryngoscopy), and any crowns or veneers (at risk of damage).
• Neck — obesity, short neck, large collar size (particularly in males with OSA), goitre, neck radiotherapy, or previous neck surgery can all contribute to difficult airway management.
• Previous difficult intubation history — any documentation in old anaesthetic records must be retrieved and reviewed. Some patients carry a "Difficult Airway Alert" card.

Systems Examination

A thorough examination of all relevant systems should follow, to corroborate the history and detect any incidental findings:

• Cardiovascular — heart rate and rhythm, blood pressure (both arms if aortic disease is suspected), peripheral pulses, heart sounds (listen for murmurs — particularly aortic stenosis, which significantly increases operative risk), and signs of heart failure (elevated JVP, bibasal crackles, peripheral oedema).
• Respiratory — respiratory rate, oxygen saturation, chest expansion, percussion, and auscultation (wheeze, crackles, reduced breath sounds).
• Abdomen — as relevant to the surgical procedure.
• Neurological — baseline neurological status, particularly if regional anaesthesia is planned.
• Peripheral access — assess venous access; alert the anaesthetist if access is likely to be difficult.
• Local skin infections — infection at or near the site of a proposed regional anaesthetic block (spinal, epidural, peripheral nerve block) is a contraindication to regional anaesthesia at that site.

Investigations

Investigations should be ordered based on the clinical findings from the history and examination, and in accordance with local pre-operative assessment protocols. Not all investigations are required for all patients — ordering unnecessary tests wastes resources, causes anxiety, and generates incidental findings that may delay surgery. The NICE guideline NG45 (2016, updated 2023) provides evidence-based guidance on pre-operative test ordering based on the grade of surgery and the patient's ASA status.

Urine

• Urine dipstick — a cheap and rapid test to detect undiagnosed or poorly controlled diabetes (glycosuria) and urinary tract infection (nitrites, leucocytes). A urinary beta-hCG should also be considered in women of reproductive age.

Blood Tests

• Full blood count (FBC) — indicated in all patients suspected or known to be anaemic, those on anticoagulants, and those undergoing major surgery. Significant anaemia (Hb <100 g/L) may require pre-operative optimisation (iron therapy, erythropoietin, or cross-match and transfusion).
• Group and save / cross-match — for any procedure with a significant risk of haemorrhage, as per local protocols.
• Coagulation screen (INR, APTT) — in patients on anticoagulants, those with suspected coagulopathy, or those undergoing procedures with high bleeding risk.
• Sickle cell test — in patients from at-risk ethnic groups (Afro-Caribbean, Mediterranean, Middle Eastern) who have not been previously tested. Sickling crises can be precipitated by hypoxia, dehydration, hypothermia, and acidosis — all of which may occur perioperatively.
• Urea and electrolytes (U&E) / renal function — indicated before major operations; identifies pre-existing renal impairment, which affects drug dosing. Also important as a baseline because surgery and anaesthesia can themselves cause perioperative AKI.
• Liver function tests (LFTs) — in patients with suspected or known liver disease, and in those with significant alcohol history.
• Blood glucose and HbA1c — in diabetic patients. An HbA1c >69 mmol/mol (>8.5%) indicates poor glycaemic control; elective surgery may be deferred.

Electrocardiogram (ECG)

An ECG should be obtained in any patient with cardiovascular risk factors, including age over 50, known cardiac disease, hypertension, diabetes, or symptoms suggestive of cardiac pathology. It provides a baseline and may reveal unexpected findings (silent MI, arrhythmia, bundle branch block, QT prolongation) that require further investigation or change anaesthetic management. Further cardiac investigations — exercise ECG, stress echocardiography, and formal transthoracic echocardiography — may be required; these should be ordered in consultation with a senior or the anaesthetist, as their interpretation lies beyond the role of the junior doctor ordering them.

Chest X-Ray

A chest X-ray is not routinely indicated for all patients. It should be requested when there is clinical suspicion of cardiac or pulmonary pathology (new murmur, unexplained breathlessness, clinical features of heart failure, suspected malignancy) or in patients with known significant cardiorespiratory disease whose last imaging is old or whose condition may have changed.

Cervical Spine X-Ray

Mandatory in all patients with rheumatoid arthritis and ankylosing spondylitis, as detailed above. Flexion and extension lateral views are required to assess atlantoaxial stability.

Lung Function Tests (Spirometry)

Spirometry is useful in patients with restrictive or obstructive lung defects to quantify severity and guide perioperative planning. For patients undergoing thoracic surgery, more detailed lung function testing (including transfer factor, TLCO) may be required to determine whether the patient can tolerate the planned resection.

Consent for Anaesthesia

Informed consent for anaesthesia is obtained by the anaesthetist, but the junior doctor performing the pre-operative assessment should be familiar with the key elements discussed. In line with the Supreme Court ruling in Montgomery v Lanarkshire Health Board (2015), consent is valid only when the patient has been given all information that a reasonable patient in their position would want to know, including material risks — regardless of the probability of those risks occurring.

Key anaesthetic risks that are routinely discussed include:

• Common risks (1 in 10 – 1 in 100): post-operative nausea and vomiting (PONV), sore throat (from endotracheal tube or laryngeal mask airway), temporary dental damage, bruising at cannula sites, headache after spinal anaesthesia.
• Less common risks (1 in 1,000 – 1 in 10,000): awareness under anaesthesia, peripheral nerve injury (from positioning or regional techniques), aspiration pneumonitis.
• Rare risks (<1 in 10,000): anaphylaxis, malignant hyperthermia, serious cardiac events, stroke, death attributable to anaesthesia.
• Epidural-specific risks: post-dural puncture headache (1–3%), failure of block, nerve damage (rare), epidural haematoma or abscess (very rare, <1 in 150,000).

Bringing It All Together

The pre-operative assessment is complete when you have documented a thorough history (systematic, covering all relevant systems), an airway assessment, a full systems examination, the results of appropriate investigations, and a clear summary of the patient's optimisation needs and outstanding issues. Communicate clearly with the anaesthetic team — if there are concerns about fitness for anaesthesia, discuss the patient with a senior before the day of surgery, not on the day.

Always keep the core question in mind: Is this patient as well as they can be? If not, what needs to be done?