Preoperative assessment and perioperative care

• Perioperative care is the whole pathway around an operation: assessment and optimisation beforehand, the procedure itself, and early recovery afterwards. The core principles are the same whether the operation is minor day-case surgery or major cancer surgery.
• Risk is stratified with the ASA physical status grade and a validated cardiac risk score, most commonly the Revised Cardiac Risk Index, together with a realistic measure of functional capacity such as metabolic equivalents or the Duke Activity Status Index.
• The modifiable risks are the ones that change outcomes: iron-deficiency anaemia, poorly controlled diabetes, smoking and alcohol, malnutrition, and anticoagulant or steroid medicines that need a planned pause or supplement.
• Fasting rules have moved away from "nil by mouth from midnight"; clear fluids are allowed up to 2 hours before anaesthesia in many guidelines, and enhanced recovery programmes build on that.
• Antibiotic prophylaxis works only when it is timed well: within 60 minutes before incision for most drugs, with repeat doses for long operations or major blood loss, and stopped once the skin is closed. ^{[6] [7]}
• Consent is an ongoing conversation about risk, benefit and alternatives, not a signature on the morning of surgery; and the WHO surgical safety checklist (19 items, three pauses) is completed for every procedure.

By the end of this page you should be able to:

1. Assign an ASA grade and interpret an RCRI score, and explain how surgical risk is graded.
2. Choose a realistic measure of functional capacity and say when a patient needs further cardiac testing before surgery.
3. Optimise anaemia, diabetes, anticoagulation and chronic glucocorticoid therapy before an operation.
4. State the fasting, antibiotic and venous thromboembolism prophylaxis rules you would apply.
5. Explain what an enhanced recovery programme contains and why.
6. Describe valid consent, the three pauses of the WHO surgical safety checklist, and the safety system they support.

An operation is only one day in the patient's illness. Perioperative care is everything around it: the first assessment and risk scoring, the weeks of optimisation that make a frail patient fitter, the morning of surgery, the anaesthetic and the procedure, and the days of recovery afterwards. Done well, it makes surgery safer and shorter; done badly, it produces complications that were visible weeks earlier.

This page is written for a medical student. It follows the current international guidelines: the 2024 American College of Cardiology/American Heart Association (ACC/AHA) perioperative cardiovascular guideline, the 2022 European Society of Cardiology/European Society of Anaesthesiology and Intensive Care (ESC/ESAIC) cardiovascular assessment guideline for non-cardiac surgery, NICE guideline NG180 (2020) on perioperative care in adults, and the World Health Organization guidance on safe surgery and surgical safety checklists. Where the major guidelines differ, both positions are given.

The American Society of Anesthesiologists (ASA) physical status classification is the simplest and most widely used summary of a patient's overall condition before anaesthesia.^[4] It is subjective and has inter-observer variability, but it is quick, needs no test, and predicts morbidity and mortality better than many complex scores in everyday practice. The grade is assigned by the anaesthetist before surgery. An emergency operation adds the suffix "E" (for example, ASA III E).

Two points worth learning now. First, age alone does not raise the grade, although many clinicians still behave as if it does; functional reserve is what matters. Second, a higher grade is not a reason to refuse surgery - it is a reason to optimise and to plan the level of postoperative monitoring.

Cardiac complications - myocardial infarction, heart failure, arrhythmia, cardiac death - are the commonest cause of serious perioperative harm after non-cardiac surgery. Both ACC/AHA and ESC/ESAIC therefore treat cardiac risk assessment as the centre of preoperative evaluation.

The Revised Cardiac Risk Index (RCRI, often called the Lee index) is a six-item score derived from a large prospective study of non-cardiac surgery.^[5] One point is given for each of six factors:

The score translates into an approximate 30-day risk of a major cardiac event:

A patient with a score of 0 or 1 is low risk; 2 is intermediate; 3 or more is high. Cardiac risk is only one dimension - it must be read alongside the surgical risk of the procedure itself and the patient's fitness.

Both guidelines grade the surgical procedure by its 30-day risk of a major adverse cardiac event. The terms are now close to aligned between them.

NICE uses a similar but older division of procedures: "high-risk surgery" is defined as surgery with a risk of mortality greater than 5%; "major or complex surgery" includes total abdominal hysterectomy, colonic resection, total joint replacement, lung operations, thyroidectomy, radical neck dissection and lumbar discectomy; "intermediate surgery" includes primary repair of an inguinal hernia, varicose vein excision, tonsillectomy and knee arthroscopy.^[1]

The urgency of the operation is graded separately, because it decides how much optimisation is possible: emergent (threat to life or limb, under 2 hours, minimal optimisation); urgent (2 to 24 hours, limited); time-sensitive (weeks to 3 months, moderate); and elective (can be delayed, full optimisation).^{[4] [3]}

A static risk score cannot capture the most important question: can this patient walk up two flights of stairs without stopping? Functional capacity, measured in metabolic equivalents (METs), is a strong predictor of perioperative events. A capacity of 4 METs or more is generally regarded as adequate; patients who cannot climb two flights of stairs have roughly double the perioperative cardiovascular event rate (9.6% versus 5.2% in one study).^[3]

Self-reported METs are a good screening tool but are notoriously unreliable - patients and clinicians both overestimate. A structured 12-item questionnaire, the Duke Activity Status Index (DASI), is more accurate and correlates with peak oxygen uptake. A DASI score below 34 is associated with increased mortality and myocardial infarction after surgery, and folding the DASI into the RCRI improves its predictive power (area under the curve from 0.63 to about 0.70).^[3][5] Routine exercise testing is not needed for everyone: both ACC/AHA and ESC agree that routine stress testing is not indicated in unselected patients, and that testing should be used only when the result would change management.^[3]

Brain natriuretic peptide (BNP) and N-terminal pro-BNP are released by the stressed ventricle and predict perioperative cardiac events well. Thresholds used in studies include an NT-proBNP of 300 pg per mL in patients under 75 years and 450 pg per mL in those 75 or older.^[5] A 12-lead ECG may be useful when there is known coronary artery disease, structural heart disease, arrhythmia or new symptoms - essential if surgery is elevated risk, optional in asymptomatic patients. Echocardiography, coronary CT and stress imaging are reserved for specific situations such as new or decompensated heart failure, valvular disease, or high-risk patients with poor or unknown functional capacity when the result would change the plan.^[3]

The message of the last two decades of trials is consistent, and both guidelines agree on it. Invasive angiography is not performed routinely for preoperative risk assessment; coronary revascularisation is done for the usual non-operative indications, such as acute coronary syndrome or significant left main disease, not simply to make surgery safer - routine revascularisation before non-cardiac surgery did not reduce perioperative events in the CARP trial.^[3] When a patient has had a percutaneous coronary intervention, the timing of surgery matters: at least 14 days after balloon angioplasty, 30 days or more after a bare-metal stent, and at least 12 months (or 3 months when the surgery is time-sensitive) after a drug-eluting stent placed for an acute coronary syndrome, or 6 months (3 months if time-sensitive) after one placed for chronic coronary disease.^[3]

RCRI is not the only perioperative risk tool. The ACS National Surgical Quality Improvement Program (NSQIP) risk calculator and frailty assessment (for example, the Clinical Frailty Scale) predict wider outcomes including pulmonary, renal and delirium complications, and are particularly useful in older patients. The important non-medical risks - frailty, dementia, falls - are often more predictive of outcome than the cardiac score.

Risk scoring is only useful if it leads to action. Optimisation is the work of the weeks before an operation.

Diabetes increases wound infection, length of stay and cardiac events. The safest message from the evidence is that chasing tight control causes hypoglycaemia and harm. NICE advises that glucose-lowering medicines are not used to achieve tight blood glucose control (4 to 6 mmol per litre) for people having surgery who have type 2 diabetes or no diabetes.^[1] Patients with type 1 diabetes follow the inpatient diabetes pathways (basal-bolus insulin with glucose checks), and individual plans are needed for insulin pump users. People with diabetes who are fasting should be early in the operating list where possible, and ambulatory surgery units should have a clear written protocol for insulin and oral agents on the day.

Non-diabetic acute stress can push glucose up; the glucose target in most Enhanced Recovery and ITU protocols for major surgery is roughly below 10 mmol per L, with insulin used when needed. Give all doses and adjustments against the local protocol.

Preoperative anaemia is common and doubles or triples the chance of receiving a blood transfusion and of a worse outcome. NICE recommends preoperative nutritional screening and treatment of iron-deficiency anaemia before surgery.^[1] For iron-deficiency anaemia, follow the national blood transfusion guidance on iron; oral iron is the usual starting point, and an alternate-day oral regimen is worth considering when daily iron causes gastrointestinal side effects.^[1] Parenteral (intravenous) iron is used when oral iron is not tolerated or there is not time to correct it, but the threshold, timing and choice of product are set by local protocol. Investigate the cause of the anaemia as well as correcting it - a low ferritin with a normal full blood count is still worth treating if surgery is approaching.

Perioperative planning for anticoagulants balances thrombosis against bleeding. There is no single consensus: regional anaesthesia societies are more conservative than surgical and cardiology guidance, because neuraxial and deep-plexus haematoma have catastrophic consequences.^[8]

After a recent coronary stent, the balance favours continuing dual antiplatelet therapy unless the bleeding risk of the operation is prohibitive; in that case, cardiology and surgery plan the pause together.

Any patient taking glucocorticoids for more than about a month may have a suppressed hypothalamic-pituitary-adrenal axis, and surgery can precipitate an adrenal crisis. The evidence supports much lower perioperative replacement than used to be given.

• Low dose, under 5 mg prednisone equivalent a day, for any length of time: low risk of clinically significant adrenal insufficiency. Continue the usual dose, give the daily dose on the morning of surgery, and watch for symptoms of insufficiency (hypotension, hyponatraemia, nausea, weakness).^[8]
• Taken for less than 4 weeks: the axis recovers within about a week; no specific action is needed beyond monitoring.^[8]
• 5 mg or more prednisone equivalent a day for over a month: variable suppression, do not stop abruptly before surgery. Continue the daily dose and give a short course of intravenous hydrocortisone, 25 to 100 mg a day, scaled to the surgical stress, until oral intake is reliable.^[8]
• Patients who have been tapered below 5 mg a day but previously took higher doses for weeks to months still warrant a short course of parenteral steroid cover when they cannot take oral medication.
• Covers are for the first day or two; maximal HPA axis activation occurs within the first 24 hours and has returned toward baseline by about 7 days, even after major surgery.^{[7] [8][8] [8]}

Equivalence tables: 5 mg prednisone is roughly equivalent to 5 mg prednisolone, 4 mg methylprednisolone, 0.375 to 0.75 mg dexamethasone, or 20 mg hydrocortisone.

Smoking and alcohol excess raise wound problems, infection and cardiac events; stopping smoking and reducing alcohol are standard preoperative advice, and should be discussed with every patient having major surgery.^[1] Preoperative nutritional screening is offered before intermediate, major or complex surgery.^[1] Prehabilitation (exercise, nutrition, anxiety management in the weeks before surgery) is increasingly used before major cancer and abdominal surgery and is delivered by a multidisciplinary team. Low-resource settings rely on the same measures without the frills: identify the ones at highest risk, correct what can be corrected in the time available, and escalate to a better-equipped centre when needed.

The old instruction "nil by mouth from midnight" has been abandoned. Prolonged fasting dehydrates, causes insulin resistance, and increases postoperative nausea. NICE advises that people having surgery, including dental surgery, may drink clear fluids until 2 hours before the operation, and reminds patients that clear fluids are water, fruit juice without pulp, coffee or tea without milk, and ice lollies.^[1] Clear fluids before surgery reduce headache, nausea and vomiting afterwards. Separate limits for solid food and milk follow the local anaesthetic and surgical fasting policy.

Carbohydrate drinks are considered before surgery for people having abdominal major or complex surgery. Patients with type 1 diabetes are managed case by case.

Antibiotic prophylaxis prevents surgical site infection only when the tissue concentration is adequate at the time of incision.

• Administer the antibiotic within 60 minutes before incision for most drugs, and 60 to 120 minutes before incision for vancomycin and fluoroquinolones, to allow tissue distribution.^[7]
• Choose the drug from the local guideline (procedure and local resistance patterns) and give it intravenously in most cases.
• Repeat the dose for procedures longer than two antibiotic half-lives or when blood loss exceeds 1,500 mL.^[7]
• Do not give further doses after skin closure, even if drains are left in place, for clean or potentially contaminated surgery.^[7]
• Keep preoperative blood glucose below 200 mg per dL, using insulin when needed; this is an underused non-antibiotic measure.^[7]
• Treat asymptomatic bacteriuria only when the procedure breaches the urinary tract mucosa.

Surgical patients are at high risk of deep vein thrombosis and pulmonary embolism. NICE recommends following the separate guideline on venous thromboembolism in people over 16, which covers both assessment and reduction of risk for people having surgery.^[1]

In practice that means: assess risk for every patient on admission for surgery (patient factors and procedure factors), combine mechanical methods (graduated compression stockings, intermittent pneumatic compression) with pharmacological prophylaxis (usually low-molecular-weight heparin or a direct oral anticoagulant) for patients at increased risk, start pharmacological prophylaxis as soon as haemostasis allows and continue until the patient is mobile, and give extended prophylaxis (up to several weeks) after major orthopaedic and abdominal cancer surgery according to the procedure-specific schedule. The exact agent, dose and duration come from the local VTE guideline.

An enhanced recovery programme (often called ERAS) is a standardised multidisciplinary pathway. NICE recommends offering an enhanced recovery programme to people having elective major or complex surgery, and that it include preoperative, intraoperative and postoperative components.^[1]

Typical components include: preoperative counselling and shared expectations; medical optimisation; nutritional screening and support; no routine bowel preparation; carbohydrate drinks up to 2 hours before surgery; minimisation of opioids and avoidance of long-acting sedation; maintenance of normothermia; goal-directed fluid therapy; early mobilisation; early oral feeding and drinking; optimised analgesia (multimodal, often including local and regional techniques); and the WHO surgical safety checklist. The evidence for these elements as a package is strongest in colorectal surgery, but the principles are now applied across most major specialties. Early mobilisation and feeding are the two components with the most visible effect on length of stay.

Consent is a process, not a form signed on the morning of surgery. NICE asks teams to follow shared decision-making guidance: discuss the person's risks and surgical options, include family or carers when appropriate, make information accessible, and take the patient's values and preferences into account.^[1] Risk should be personalised ("for someone of your age and condition") rather than read from a population figure.

Pain management and analgesia options are discussed before surgery, with a plan made for the expected level of pain, comorbidities and the person's preferences.^[1] For a high-risk operation, consent should cover the possibility of intensive care, transfusion, stoma formation and non-operative alternatives, and these conversations belong to the preoperative assessment clinic, not the anaesthetic room.

The WHO surgical safety checklist is a 19-item checklist used before every surgical procedure, including dental procedures. NICE requires it to be completed for each operation, and teams are encouraged to add locally relevant steps and to follow the WHO implementation manual when doing so.^[1][2]

It forces three brief team pauses:

1. Sign-in (before anaesthesia): identity, site and procedure; consent; site marked; anaesthesia safety check; pulse oximeter on.
2. Time-out (before skin incision): all team members present; anticipated critical events (surgeon, anaesthetist, nurse); antibiotic prophylaxis given within the last 60 minutes; essential imaging displayed.
3. Sign-out (before the patient leaves the operating room): the name of the procedure recorded; counts of instruments, swabs and needles; specimen labelling; equipment problems; key concerns for recovery and management.

The checklist is a communication tool as much as a memory aid: its effect comes from the whole team stopping, talking, and catching a mismatched patient, site or swab before the error is final. It has been shown to reduce both morbidity and mortality in the settings where it has been introduced, and is now used by most surgical providers worldwide.^[2]

Where echocardiography, biomarkers or cardiology are not available, the same principles apply with cheaper tools: a good history and examination, ASA grading, RCRI from clinical factors alone, and a short walk to judge functional capacity. Preoperative ultrasound where available improves anaemia detection; intravenous iron and modern anticoagulants may be unaffordable, so oral iron, early surgery without bridging where thrombotic risk is not high, and mechanical VTE prophylaxis carry much of the load. Clear fluids until 2 hours before surgery costs nothing and helps everyone. ^[5]

• Perioperative care covers the whole pathway, not just the operation: assess, optimise, operate, recover.
• The ASA physical status grade summarises overall health in six classes (I to VI), with an "E" for emergency surgery; it is predictive but subjective, and high grade means optimise, not refuse.
• The Revised Cardiac Risk Index uses six clinical predictors and estimates 30-day cardiac risk roughly as 0.4% (0 points), 0.9% (1), 6.6% (2) and >11% (3 or more). ^[4]
• Functional capacity is a powerful predictor; 4 METs is adequate, and a DASI score below 34 flags higher risk. Self-reported METs overestimate; use DASI.
• Under ACC/AHA 2024 and ESC/ESAIC 2022 both, routine cardiac testing is not indicated; test only when the result changes management.
• Surgical risk (ACC/AHA 2024): under 1%, 1 to 5% and above 5% at 30 days. ^[3]
• Diabetes: do not chase tight glucose control (4 to 6 mmol per L) with glucose-lowering drugs in type 2 diabetes or in people without diabetes.
• Anaemia: treat iron deficiency before surgery, using oral iron (alternate-day dosing if side effects) and intravenous iron when needed.
• Anticoagulants: warfarin stopped about 5 days before surgery; DOACs 1 to 2 days before standard surgery; bridging reserved for selected high-risk patients.
• Steroids: patients taking 5 mg or more prednisone equivalent for over a month get continued daily dose plus 25 to 100 mg intravenous hydrocortisone a day scaled to stress; low-dose and short courses need monitoring only. ^[8]
• Fasting: clear fluids allowed until 2 hours before anaesthesia.
• Antibiotics: give within 60 minutes before incision, 60 to 120 minutes for vancomycin or fluoroquinolones; repeat for long cases or blood loss above 1,500 mL; stop after skin closure.
• Enhanced recovery: offer for elective major or complex surgery, with preoperative, intraoperative and postoperative components.
• Consent is a conversation about risks, benefits, alternatives and values, begun well before the day of surgery.
• The WHO surgical safety checklist has 19 items and three pauses (sign-in, time-out, sign-out) for every procedure. ^[2]

Consent and shared decision-making, enhanced recovery, VTE prophylaxis, perioperative cardiac risk, anaemia, type 1 and type 2 diabetes mellitus, thrombocytopaenia and bleeding disorders, adrenal insufficiency, surgical site infection, pain management.