Surgery: Surgical principles and perioperative care

🔪 Surgical principles and perioperative care. Good surgical outcomes depend as much on what happens before and after the operation as on the operation itself: assessing and optimising the patient, getting medicines right, preventing infection and clots, and spotting complications early. The other pages cover acute abdomen, hernias, upper GI and hepatobiliary, colorectal, breast and endocrine, vascular, urology, major trauma and burns, trauma and orthopaedics, and cardiothoracic, neurosurgery and plastic surgery.
Your four questions for every surgical patient: How urgent is the operation, and is the patient fit enough (and do they want it)? What can be optimised beforehand -medicines, anaemia, diabetes, frailty? What could go wrong during and after surgery, and how do we prevent it? Is this patient recovering as expected, or is a complication developing?

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Urgency of Surgery

NCEPOD category	Timing	Examples
Immediate	Within minutes -life, limb or organ saving	Ruptured AAA, major haemorrhage, airway compromise, compartment syndrome, testicular torsion
Urgent	Within hours	Perforated viscus, bowel obstruction with ischaemia, necrotising fasciitis, open fracture, hip fracture (within 36 hours)
Expedited	Within days -stable but needs early surgery	Cancer causing obstruction, unstable fractures, gallstone pancreatitis needing cholecystectomy on the same admission
Elective	Planned	Hernia repair, joint replacement, most cancer resections, cholecystectomy for biliary colic

• Emergency surgery carries much higher risk than elective surgery -less time to optimise, sicker patients, out-of-hours operating; emergency laparotomy has a 30-day mortality around 1 in 10 (higher in older people).
• Decide early with seniors -involve consultant surgeons and anaesthetists in high-risk cases; consider whether surgery is in the patient's interests (shared decision-making, ceilings of care).

Pre-operative Assessment and Risk

• History:
  • Cardiovascular -angina, heart failure, valve disease (aortic stenosis), arrhythmias, pacemakers or defibrillators, recent MI or stents.
  • Respiratory -COPD, asthma, obstructive sleep apnoea (STOP-BANG questions), smoking.
  • Other -diabetes, CKD, liver disease, stroke, epilepsy, bleeding disorders, reflux (aspiration), pregnancy.
  • Functional capacity -can they climb two flights of stairs without stopping (about 4 METs)? Poor exercise tolerance predicts complications.
  • Previous anaesthetics -problems such as difficult airway, nausea and vomiting, awareness, reactions; family history of anaesthetic problems (malignant hyperthermia, suxamethonium apnoea).
  • Drugs and allergies (including latex and chlorhexidine), alcohol, smoking, recreational drugs.
  • Frailty (Clinical Frailty Scale), cognition, social support, and the patient's wishes.
• Examination -airway (mouth opening, neck movement, teeth -dentures, crowns), heart murmurs, chest, BMI, sites for regional anaesthesia, peripheral veins.

ASA grade	Description
I	Healthy person
II	Mild systemic disease (e.g. controlled hypertension, well-controlled diabetes, smoker, mild obesity)
III	Severe systemic disease (e.g. poorly controlled diabetes, COPD, morbid obesity, stable angina, dialysis)
IV	Severe systemic disease that is a constant threat to life (e.g. recent MI, severe heart failure, sepsis)
V	Moribund -not expected to survive without the operation (e.g. ruptured AAA)
VI	Brain-dead organ donor

• Add "E" for emergency surgery.
• Risk tools -the NELA risk calculator (emergency laparotomy), P-POSSUM, the Surgical Outcome Risk Tool; cardiopulmonary exercise testing (CPET) for major elective surgery; frailty scores. Patients with high predicted risk (e.g. mortality 5% or more) should have consultant-led care and planned critical care admission.
• Cardiac risk -recent MI (ideally wait at least 3–6 months for elective surgery), unstable angina, decompensated heart failure, severe aortic stenosis (murmur -echo), new arrhythmias -optimise or delay elective surgery; recent coronary stents -discuss antiplatelets with cardiology.

Pre-operative Tests

• Test only when it changes management (NICE NG45) -routine tests in healthy people having minor surgery rarely help.
• Typical tests by situation:
  • FBC -major surgery, older people, expected blood loss, anaemia symptoms, CKD.
  • U&E -major surgery, CKD, diabetes, heart failure, drugs affecting kidneys (ACE inhibitors, diuretics).
  • Clotting -on anticoagulants, liver disease, bleeding history.
  • ECG -cardiovascular, renal or diabetic disease, older patients having major surgery.
  • HbA1c -people with diabetes (if not done in the last 3 months).
  • Pregnancy test -ask every woman who could be pregnant; offer a test with consent.
  • Sickle cell test -if family origin or history suggests risk and status is unknown.
  • Group and save or crossmatch -depending on the operation and expected blood loss.
  • Echocardiogram -murmurs, heart failure; lung function and blood gas in severe lung disease; MRSA screen per local policy.
• Pre-operative assessment clinics -run by nurses and anaesthetists; identify problems early, start optimisation, and plan admission and discharge.

Consent

• Valid consent needs a patient who has capacity, is properly informed, and agrees voluntarily (without pressure).
• What to discuss (Montgomery ruling 2015; GMC Decision Making and Consent 2020):
  • The diagnosis, what the operation involves, its expected benefits.
  • Material risks -any risk a reasonable person in the patient's position would want to know, or that this particular patient would want to know (common risks and serious rare ones).
  • Reasonable alternatives -including doing nothing.
  • Answer questions honestly; check understanding; give written information and time to decide where possible.
• Who takes consent -ideally the operating surgeon, or someone who can do the procedure or is trained to discuss it.
• Capacity (Mental Capacity Act 2005) -assume capacity; a person lacks capacity for a decision if, because of an impairment of the mind or brain, they can't understand, retain, weigh up the information, or communicate a decision. Capacity is decision-specific and can fluctuate.
• If the patient lacks capacity -act in their best interests (involve family, carers, an IMCA if no one else; check for a valid advance decision or lasting power of attorney for health); emergency life-saving treatment can be given without delay.
• Children -16- and 17-year-olds are presumed to have capacity; under-16s can consent if Gillick competent; parents can usually consent for younger children.
• Refusal -a competent adult can refuse any treatment, even if it leads to death (e.g. blood products for many Jehovah's Witnesses) -document carefully.
• Consent is a process, not a signature -re-confirm on the day of surgery; mark the site; document the discussion.

Fasting and Aspiration Risk

• Why fast -to reduce the risk of stomach contents being inhaled (pulmonary aspiration) during anaesthesia.
• Usual adult rules -no food for 6 hours; clear fluids up to 2 hours before (many UK units now allow sips of clear fluid until called to theatre -"sip til send"). Breast milk 4 hours and formula 6 hours for babies.
• Avoid prolonged fasting -dehydration, hypoglycaemia, discomfort, delirium in older people; carbohydrate drinks are used in enhanced recovery.
• Higher aspiration risk -emergency surgery (full stomach), bowel obstruction (NG tube), pregnancy, obesity, reflux and hiatus hernia, diabetes with gastroparesis, opioids, GLP-1 receptor agonists and tirzepatide (slowed stomach emptying -tell the anaesthetist; MHRA), reduced consciousness.
• Rapid sequence induction -used when aspiration risk is high: pre-oxygenation, rapid drugs, cricoid pressure (in some practice) and quick intubation.
• Take usual medicines with a sip of water unless told otherwise.

Medicines Before Surgery

• Anticoagulants:
  • Warfarin -stop 5 days before; check INR the day before (aim 1.5 or less; give oral vitamin K if higher); bridging LMWH only for high clot risk (e.g. mechanical mitral valve, VTE in the last 3 months); restart the evening of surgery or the next day if bleeding allows.
  • DOACs (apixaban, rivaroxaban, edoxaban) -usually stop 24 hours before low-bleeding-risk and 48 hours before high-bleeding-risk surgery (longer with poor kidney function, and for neuraxial anaesthesia); dabigatran needs longer with reduced kidney function; no bridging; restart 24–72 hours after depending on bleeding risk.
• Antiplatelets:
  • Aspirin -usually continued (except some neurosurgery, spinal, eye and urological procedures).
  • Clopidogrel and ticagrelor -stop about 5 days before; prasugrel about 7 days.
  • Never stop dual antiplatelet therapy after recent coronary stents without cardiology advice -stent thrombosis risk.
• Diabetes (CPOC guidance -see the Endocrine chapters):
  • SGLT2 inhibitors -omit the day before and the day of surgery (euglycaemic DKA).
  • Sulfonylureas -omit on the day of surgery (hypoglycaemia).
  • Metformin -usually continue (omit if three times daily at lunch, or with contrast or reduced eGFR, per local policy).
  • Long-acting insulin -reduce by about 20% the evening before and the morning of surgery; VRIII if more than one meal will be missed or glucose is poorly controlled.
  • Target glucose 6–12 mmol/L; HbA1c under 69 mmol/mol before elective surgery where possible.
• Steroids -never stop; give extra cover (e.g. IV hydrocortisone at induction) for patients on long-term steroids or with adrenal insufficiency.
• Cardiovascular drugs -continue beta-blockers and statins; often omit ACE inhibitors, ARBs and diuretics on the morning of surgery (low blood pressure, AKI) and restart when eating and drinking and euvolaemic.
• Hormones -the combined pill is usually stopped 4 weeks before major elective surgery or surgery involving immobilisation (VTE risk) -switch to a progestogen-only method; HRT can often continue with VTE prophylaxis (assess risk).
• Lithium -usually stopped 24 hours before major surgery and restarted when eating and drinking with normal U&E; MAO inhibitors -specialist advice (interactions with pethidine and vasopressors).
• Continue -antiseizure medicines, Parkinson's drugs (time-critical -use a rotigotine patch or NG route if nil by mouth), levothyroxine, inhalers, antipsychotics (usually), most antidepressants.
• Immunosuppressants and biologics -follow specialty guidance (biologics are often paused around surgery; methotrexate is usually continued).
• Herbal remedies (ginkgo, garlic, ginseng, St John's wort) -stop 1–2 weeks before (bleeding and interactions).

Optimising the Patient

• Anaemia -find and treat it before elective surgery (iron deficiency is common -IV iron works within weeks); reduces transfusion and complications (patient blood management).
• Smoking -stopping at any time helps (ideally 6–8 weeks before) -fewer wound, lung and heart complications.
• Alcohol -reduce harmful drinking; plan for withdrawal (chlordiazepoxide, thiamine).
• Diabetes -improve control; plan medicines and glucose monitoring.
• Blood pressure -very high blood pressure (e.g. 180/110 mmHg or more) may need control before elective surgery; don't delay for modest rises.
• Nutrition -screen with MUST; malnourished patients benefit from oral supplements or feeding before major surgery.
• Prehabilitation -exercise, nutrition and psychological support in the weeks before major surgery improve fitness and recovery.
• Frailty and older people -comprehensive geriatric assessment (perioperative medicine for older people -POPS services), medicines review, delirium risk, discharge planning.
• Heart and lungs -treat heart failure and arrhythmias; optimise COPD and asthma; CPAP for sleep apnoea.
• Infection -treat active infections (e.g. dental, urinary) before joint replacement; MRSA decolonisation.

The WHO Surgical Safety Checklist

• Used for every operation -reduces deaths and complications by improving teamwork and catching errors.
• Sign in (before anaesthesia) -patient identity, procedure, site marked, consent, allergies, airway or aspiration risk, expected blood loss, anaesthetic machine and drug checks.
• Time out (before the skin incision) -team introductions, confirmation of patient, procedure and site, antibiotic prophylaxis given within the last 60 minutes, VTE prophylaxis, critical events anticipated (surgeon, anaesthetist, nursing), imaging displayed, equipment and implants available.
• Sign out (before leaving theatre) -procedure recorded, instrument, swab and needle counts correct, specimens labelled, equipment problems, key concerns for recovery and post-operative care.
• Never events in surgery include wrong site surgery, retained foreign object after surgery, wrong implant or prosthesis, and misplaced nasogastric tubes -wholly preventable with proper checks.
• Team briefings and debriefs at the start and end of each list support safety.

Anaesthesia Basics

• General anaesthesia -three parts:
  • Unconsciousness -IV induction (propofol, thiopental, ketamine, etomidate) then maintenance with volatile gases (sevoflurane, desflurane) or a propofol infusion.
  • Pain relief -opioids (fentanyl, remifentanil, morphine), paracetamol, NSAIDs, local anaesthetic blocks.
  • Muscle relaxation when needed -neuromuscular blockers (rocuronium, atracurium; suxamethonium for rapid sequence); reversed with neostigmine or sugammadex.
• Airway -face mask, supraglottic airway (laryngeal mask) or endotracheal tube.
• Regional anaesthesia:
  • Spinal -local anaesthetic into the CSF (single shot) -lower body surgery (hip fracture, caesarean section, TURP); fast and dense block.
  • Epidural -catheter into the epidural space -continuous pain relief (labour, major abdominal and chest surgery).
  • Side effects -low blood pressure (sympathetic block), urinary retention, itch (opioids), headache after dural puncture; rare epidural haematoma or abscess (check clotting and anticoagulant timing; urgent MRI if new leg weakness).
  • Peripheral nerve blocks (e.g. femoral or fascia iliaca block for hip fracture) -good pain relief with fewer opioids.
• Sedation -for endoscopy and minor procedures (midazolam, opioids, propofol) -risk of respiratory depression; monitoring and reversal agents (naloxone, flumazenil) available.
• Common minor problems -sore throat, nausea and vomiting, dental damage, shivering, drowsiness; rare serious ones -awareness, aspiration, anaphylaxis, malignant hyperthermia, nerve injury from positioning, eye injury.

Local Anaesthetics and Toxicity

Drug	Approximate maximum dose	Notes
Lidocaine (plain)	3 mg/kg (maximum 200 mg)	Fast onset, short action; 1% = 10 mg/mL
Lidocaine with adrenaline	7 mg/kg (maximum 500 mg)	Adrenaline slows absorption and reduces bleeding
Bupivacaine / levobupivacaine	2 mg/kg (maximum 150 mg)	Slow onset, long action; more cardiotoxic
Prilocaine	6 mg/kg	IV regional anaesthesia (Bier's block); methaemoglobinaemia

• Convert percentage to mg -1% = 10 mg/mL; 0.5% = 5 mg/mL; 2% = 20 mg/mL. E.g. 20 mL of 1% lidocaine = 200 mg (the maximum plain dose for most adults).
• Local anaesthetic systemic toxicity (LAST) -from accidental IV injection or overdose:
  • Early -tingling around the mouth, metallic taste, tinnitus, light-headedness, agitation.
  • Late -confusion, seizures, coma, arrhythmias, cardiovascular collapse.
  • Treatment -stop injecting, call for help, airway and 100% oxygen, treat seizures (benzodiazepine), 20% lipid emulsion (1.5 mL/kg bolus then infusion), prolonged CPR if arrested (recovery can take over an hour).
• Prevent LAST -calculate the maximum dose for the patient's weight before starting, aspirate before injecting, inject slowly in small amounts, use ultrasound guidance for blocks.

Anaesthetic Emergencies

• Malignant hyperthermia:
  • An inherited (usually RYR1) muscle disorder triggered by volatile anaesthetics and suxamethonium.
  • Features -rising end-tidal CO2 (often first), tachycardia, muscle rigidity (jaw), rising temperature (later), high potassium, acidosis, arrhythmias, rhabdomyolysis.
  • Treatment -stop the triggers, hyperventilate with 100% oxygen, IV dantrolene, active cooling, treat high potassium and acidosis, ICU; refer patient and family to the UK malignant hyperthermia unit for testing.
• Suxamethonium apnoea -inherited or acquired lack of plasma cholinesterase → prolonged paralysis after suxamethonium; keep sedated and ventilated until it wears off; warn the family.
• Perioperative anaphylaxis -commonest triggers: antibiotics (e.g. teicoplanin, co-amoxiclav), neuromuscular blockers, chlorhexidine, patent blue dye; features may be just sudden hypotension or bronchospasm; IM or IV adrenaline per protocol, fluids, stop the trigger; mast cell tryptase at intervals; refer for allergy testing.
• Difficult airway -"can't intubate, can't oxygenate" -follow Difficult Airway Society guidance (front-of-neck access as last resort).
• Aspiration -bronchospasm, hypoxia, chest X-ray changes; suction, oxygen, supportive care (antibiotics only if infection develops).
• Bradycardia and hypotension under spinal anaesthesia -fluids, vasopressors (ephedrine, phenylephrine), atropine.

Wound Classes and Antibiotic Prophylaxis

Wound class	Definition and examples	Antibiotics
Clean	No hollow organ entered; no inflammation -hernia repair, thyroidectomy, breast surgery, joint replacement	None, unless a prosthesis or implant is inserted (e.g. joint replacement, mesh in some cases)
Clean-contaminated	A hollow organ (gut, airway, urinary tract) entered under controlled conditions -cholecystectomy, elective bowel resection	Single-dose prophylaxis
Contaminated	Spillage from the gut, open fresh trauma, acute non-purulent inflammation -appendicectomy for inflamed appendix	Prophylaxis (± a short treatment course)
Dirty	Pus, perforation, faecal contamination, old traumatic wounds	Treatment course

• Timing -give IV prophylaxis within 60 minutes before the incision (so tissue levels are high when the wound is open); a single dose is usually enough; repeat for long operations or major blood loss.
• Choice -per local guidelines (e.g. cefuroxime plus metronidazole, or co-amoxiclav, for bowel surgery; flucloxacillin or cefuroxime for orthopaedic implants; teicoplanin or vancomycin if MRSA-positive or penicillin-allergic).
• Preventing surgical site infection (NICE NG125) -shower before surgery; don't routinely remove hair (use clippers on the day, not razors); MRSA decolonisation where indicated; alcohol-based chlorhexidine skin preparation; keep the patient warm, well oxygenated and with controlled glucose; good surgical technique; appropriate dressings.

VTE Prophylaxis

• Assess every surgical patient for VTE and bleeding risk on admission and regularly after (NICE NG89).
• Mechanical prophylaxis -anti-embolism stockings (not in peripheral arterial disease, neuropathy, leg ulcers or skin grafts) or intermittent pneumatic compression; early mobilisation and hydration.
• Pharmacological prophylaxis -usually LMWH (e.g. enoxaparin 40 mg daily, adjusted for weight and kidney function), starting 6–12 hours after surgery (timing around neuraxial anaesthesia matters), continued until mobility returns (often at least 7 days for major surgery).
• Extended prophylaxis:
  • 28 days after major abdominal or pelvic cancer surgery.
  • Elective hip replacement -LMWH for 10 days then aspirin for 28 days, or LMWH for 28 days, or a DOAC (e.g. apixaban, rivaroxaban).
  • Elective knee replacement -aspirin for 14 days, or LMWH for 14 days, or a DOAC.
  • Fragility fractures (e.g. hip fracture) -LMWH for about a month.
• Lower limb immobilisation in plaster -consider LMWH if VTE risk outweighs bleeding risk.
• Patients already on anticoagulants -plan when to stop and restart (see Medicines Before Surgery).

Enhanced Recovery

• Enhanced recovery after surgery (ERAS) -a package of evidence-based steps that reduce the stress of surgery, speed recovery and shorten hospital stays.
• Before surgery -patient education and expectations, prehabilitation, optimising anaemia and nutrition, minimal fasting and carbohydrate drinks, avoiding routine bowel preparation (in many procedures), no long-acting sedative premedication.
• During surgery -minimally invasive surgery where possible, goal-directed fluid therapy (avoid overload), normothermia, regional anaesthesia, avoiding routine drains and NG tubes, PONV prophylaxis.
• After surgery -multimodal, opioid-sparing pain relief (paracetamol, NSAIDs if safe, regional techniques), early eating and drinking, early mobilisation (sitting out on day 0 or 1), early removal of catheters and lines, chewing gum (ileus), planned discharge criteria.
• Benefits -fewer complications (ileus, pneumonia, VTE), faster return of gut function, shorter stays, without higher readmission rates.

Post-operative Care and Pain Relief

• Recovery and the ward -regular observations (NEWS2 -act on rising scores), fluid balance, urine output, wound and drain checks, pain and nausea scores, glucose in diabetes, early mobilisation, VTE prophylaxis, review of medicines (restart usual drugs when safe).
• Pain relief -good analgesia allows deep breathing, coughing and walking (fewer chest infections and clots):
  • Regular paracetamol (reduce dose if under 50 kg, liver disease or malnourished).
  • NSAIDs if safe (avoid in AKI, CKD, GI bleeding risk, heart failure, some anastomoses -local policy).
  • Opioids -oral (e.g. oxycodone, morphine) or patient-controlled analgesia (PCA); watch for respiratory depression, sedation, nausea, constipation, confusion and urinary retention; reduce doses in older people and CKD; prescribe laxatives and antiemetics; naloxone available.
  • Regional techniques -epidurals, nerve blocks, wound catheters, spinal opioids.
  • Gabapentinoids -not routinely (sedation, respiratory depression with opioids).
• Epidural problems -low blood pressure (fluids, reduce rate), numb or weak legs (stop the infusion; if not improving within hours, consider epidural haematoma or abscess -urgent MRI), inadequate block, urinary retention.
• Restart usual medicines -especially time-critical ones (Parkinson's drugs, insulin, antiseizure medicines, steroids) and anticoagulants when bleeding risk allows.

Post-operative Fluids

• The "5 Rs" (NICE CG174) -Resuscitation, Routine maintenance, Replacement of losses, Redistribution (oedema, sepsis), Reassessment.
• Prefer oral fluids as soon as possible; stop IV fluids when no longer needed.
• Resuscitation -500 mL crystalloid (balanced, e.g. Hartmann's or Plasma-Lyte, or 0.9% saline) over less than 15 minutes, then reassess; if over 2 L is needed, get senior help (look for bleeding, sepsis, a leak).
• Routine maintenance (adults):
  • Water -25–30 mL/kg/day (less -20–25 mL/kg/day -in older, frail, heart failure or kidney failure patients; use ideal weight in obesity).
  • Potassium, sodium and chloride -about 1 mmol/kg/day each.
  • Glucose -50–100 g/day (to limit starvation ketosis).
  • Example (70 kg) -about 2 litres a day, e.g. 0.18% saline/4% glucose with potassium, or mixtures that meet the targets.
• Replace ongoing losses -vomiting, NG aspirates, high-output stomas, drains, fistulas -usually with electrolyte-containing fluids (with potassium).
• After surgery, the body retains water and salt (stress hormones -ADH and aldosterone) -so over-hydration and hyponatraemia are common, especially with too much 5% glucose or hypotonic fluids (and in children and older people); too much 0.9% saline causes oedema and hyperchloraemic acidosis.
• Monitor -fluid balance chart, daily weight where possible, U&E daily while on IV fluids, clinical hydration (pulse, BP, capillary refill, JVP, mucous membranes, urine output).

Post-operative Complications by Time

Timing	Complications to think of
Immediate (within 24 hours)	Primary and reactionary haemorrhage (slipped ligature as BP recovers), airway problems, low blood pressure, urinary retention, pain, PONV, MI and arrhythmias, anaesthetic complications, compartment syndrome (limbs), early graft or flap problems
Early (days 1–7)	Atelectasis (days 1–2), pneumonia, AKI, ileus, delirium, UTI, line infection, wound infection (days 5–7), anastomotic leak (typically days 5–7), new AF (often a sign of sepsis or a leak), pressure ulcers, C. difficile, hyponatraemia
Days 7–14	Wound dehiscence, DVT and PE (any time, peak around days 7–10), secondary haemorrhage (infection eroding a vessel), abscesses (pelvic, subphrenic)
Late (weeks to years)	Incisional hernia, adhesions (bowel obstruction), chronic pain, keloid or hypertrophic scars, stricture, recurrence of disease, psychological effects

• Atelectasis -small airways collapse after anaesthesia, pain and lying flat: low saturations, crackles at the bases, mild fever; prevent and treat with analgesia, deep breathing, incentive spirometry, physiotherapy, sitting up and mobilising.
• Anastomotic leak -after bowel joins: fever, tachycardia, worsening pain, prolonged ileus, peritonism, confusion, new AF, rising CRP (persistently high CRP after day 3 is a warning); CT with contrast; resuscitation, antibiotics and often return to theatre or radiological drainage.
• Post-operative MI -often painless (masked by analgesia) -hypotension, breathlessness, arrhythmia; check ECG and troponin.
• Haemorrhage -tachycardia, hypotension, falling Hb, swelling, drain output; resuscitate, correct clotting, return to theatre if needed.

Post-operative Fever

• Days 0–2 -usually the normal inflammatory response to surgery; also atelectasis, transfusion reactions, and rarely early necrotising wound infection (group A strep or clostridia -severe pain, rapid spread -urgent review); malignant hyperthermia (during or just after anaesthesia).
• Days 3–5 -pneumonia, UTI (especially with catheters), line and cannula infections.
• Days 5–7 -wound infection, anastomotic leak, intra-abdominal or pelvic abscess.
• After day 7 -DVT and PE, abscesses, C. difficile, drug fever, infected collections or prostheses.
• Memory aid -the "5 Ws" -Wind (lungs), Water (urine), Wound, Walking (VTE), Wonder drugs (drug reactions) -plus "What did we do?" (lines, the operation site, leaks).
• Assess -examine the chest, wound, lines, calves, abdomen and drains; cultures (blood, urine, sputum, wound); CXR; CT for suspected collections or leaks; don't give antibiotics "blind" without looking for the source.

Low Urine Output and AKI

• Oliguria -urine output under 0.5 mL/kg/hour (for 6 hours meets the AKI definition).
• Check the catheter first -blocked or kinked (flush it); if no catheter, check for urinary retention (bladder scan).
• Common causes after surgery:
  • Pre-renal -hypovolaemia (under-replacement, bleeding, third-space losses, high stoma output), sepsis, heart failure, low BP from epidurals or antihypertensives.
  • Renal -prolonged hypotension (ATN), nephrotoxic drugs (NSAIDs, gentamicin, contrast, ACE inhibitors), rhabdomyolysis (long operations, compartment syndrome, prolonged lying).
  • Post-renal -blocked catheter, retention, ureteric injury (after pelvic surgery).
  • Abdominal compartment syndrome -tense abdomen with rising airway pressures and falling urine output (measure bladder pressure).
• Management -assess fluid status; fluid challenge (e.g. 250–500 mL crystalloid) if dry, then reassess; stop nephrotoxins; U&E and potassium; urinalysis; ultrasound if obstruction is possible; look for sepsis or bleeding; senior review if not responding (see the AKI chapters).
• Don't give diuretics to make urine in a dry patient.

Wound Healing and Wound Complications

• Phases of healing -haemostasis (minutes), inflammation (days 1–4), proliferation (granulation tissue and new collagen -days 4–21), remodelling (up to 1–2 years; scar reaches about 80% of normal strength).
• Primary intention -wound edges closed (sutures, staples, glue); secondary intention -left open to heal by granulation (contaminated wounds, abscess cavities, pilonidal sinus); delayed primary closure -closed after a few days once clean.
• Factors that delay healing -local: infection, poor blood supply, tension, haematoma, foreign material, previous radiotherapy; systemic: age, diabetes, smoking, steroids and immunosuppressants, malnutrition (protein, vitamin C, zinc), obesity, anaemia, jaundice, chemotherapy, kidney failure.
• Surgical site infection -superficial (skin), deep (fascia and muscle) or organ/space (abscess) -redness, warmth, pain, discharge, fever; open and drain pus, swab, antibiotics if spreading cellulitis or systemic signs.
• Seroma and haematoma -fluid or blood collections; may need aspiration or drainage.
• Wound dehiscence ("burst abdomen"):
  • Usually around days 7–10 after laparotomy; warning sign -a gush of pink, serosanguinous fluid from the wound.
  • Risk factors -obesity, malnutrition, steroids, infection, raised abdominal pressure (coughing, ileus), emergency surgery, poor closure technique.
  • Management -reassure, analgesia, cover the bowel with warm saline-soaked sterile packs, nil by mouth, IV fluids, urgent return to theatre.
• Scars -hypertrophic (raised but within the wound, improves with time) versus keloid (extends beyond the wound; darker skin, earlobes, chest, shoulders; recurs after excision -steroid injections, pressure, silicone).
• Suture removal (typical) -face 5 days, scalp 7–10 days, limbs and trunk 10–14 days; longer over joints and in poor healers.

Delirium, Nausea and Ileus

• Post-operative delirium -common in older people (especially after hip fracture and emergency surgery): acute confusion, inattention, fluctuating course; may be hypoactive (quiet, drowsy -often missed).
  • Look for causes -pain, urinary retention, constipation, infection, hypoxia, dehydration, low sodium, low glucose, drugs (opioids, anticholinergics, benzodiazepines), alcohol withdrawal, missed medications (e.g. Parkinson's), sleep disruption, unfamiliar environment.
  • Prevent and manage -orientation, glasses and hearing aids, family involvement, sleep, mobilisation, hydration and nutrition, good pain control, avoid unnecessary catheters and moves; avoid sedatives where possible (use low-dose haloperidol only for severe distress or risk, not in Parkinson's or Lewy body dementia).
• Post-operative nausea and vomiting (PONV):
  • Risk factors (Apfel) -female, non-smoker, previous PONV or motion sickness, post-operative opioids.
  • Prevention -ondansetron, dexamethasone, cyclizine (combinations in high risk), regional techniques, minimise opioids, hydration.
• Post-operative ileus -temporary loss of gut movement after abdominal surgery (also from opioids, low potassium or magnesium, sepsis, retroperitoneal bleeding): distension, vomiting, no flatus, quiet abdomen; correct electrolytes, reduce opioids, NG tube if vomiting, mobilise; usually resolves in days.
• Ileus versus obstruction -mechanical obstruction (adhesions, hernia, internal herniation) causes colicky pain and tinkling bowel sounds and may need surgery; CT helps if ileus is prolonged; a prolonged ileus can be a sign of a leak or abscess.

Drains, Catheters and Nasogastric Tubes

• Surgical drains -remove fluid or blood or detect leaks; open (passive) or closed (suction); monitor volume and content (fresh blood -bleeding; bile, bowel content or pus -leak; chyle -milky); remove when output is low; not routinely used in many operations (ERAS).
• Urinary catheters -for urine output monitoring in major surgery and for retention; remove as early as possible (UTI risk); trial without catheter.
• Nasogastric (NG) tubes:
  • Uses -decompression in bowel obstruction or ileus (wide-bore Ryle's tube), or feeding (fine-bore tube).
  • Check position before every use -aspirate with pH 5.5 or below, or a chest X-ray interpreted by a competent person if no aspirate or pH is higher. Never use the "whoosh" test or water-in-a-glass bubbling.
  • Feeding through a misplaced tube (into the lung) is a never event.
• Chest drains -see the Respiratory Emergencies chapter; safe triangle; check for swinging and bubbling; don't clamp a bubbling drain.
• Central lines -aseptic care; remove when not needed; check position on X-ray after insertion (neck and chest lines).

Surgery in Special Groups

• Older and frail people -higher risk of delirium, falls, pressure ulcers, functional decline; comprehensive geriatric assessment, careful drug dosing, early mobilisation and discharge planning; discuss goals and ceilings of care.
• Diabetes -first on the list where possible, glucose monitoring, CPOC medicine plan, VRIII when appropriate; watch for DKA with SGLT2 inhibitors.
• On anticoagulants or antiplatelets -plan stopping and restarting; bridging only for high-risk patients.
• Long-term steroids or adrenal insufficiency -steroid cover; never omit.
• Obesity -airway, sleep apnoea, VTE, wound infection, positioning, drug dosing by appropriate weight.
• Pregnancy -avoid elective surgery; urgent surgery is safest in the second trimester; appendicitis is the commonest non-obstetric surgical emergency; left lateral tilt after 20 weeks (avoid aortocaval compression); VTE prophylaxis; obstetric input and fetal monitoring as advised; ask about and test for pregnancy before surgery in women who could be pregnant.
• Liver disease -high risk with cirrhosis (Child–Pugh and MELD scores), bleeding, encephalopathy, ascites, poor healing.
• CKD and dialysis -fluid and potassium management, dialysis timing, drug dosing, protect fistula arm.
• Parkinson's disease -time-critical medicines (rotigotine patch if nil by mouth); avoid metoclopramide and haloperidol.
• Sickle cell disease -haematology input, transfusion before major surgery in many, avoid hypoxia, dehydration, cold and acidosis.
• Patients who decline blood -plan early (iron, cell salvage, tranexamic acid, minimising blood tests); respect their decision.
• Implanted cardiac devices -check settings before surgery (diathermy can interfere); reprogramming may be needed.

Medicines Around Surgery at a Glance

Medicine	Usual plan (check local policy)
Warfarin	Stop 5 days before; INR 1.5 or less; bridge only if high clot risk
Apixaban, rivaroxaban, edoxaban	Stop 24 hours (low bleeding risk) or 48 hours (high) before; longer in CKD or neuraxial
Dabigatran	Stop 1–4 days before depending on kidney function and bleeding risk
Aspirin	Usually continue
Clopidogrel / ticagrelor / prasugrel	Stop about 5 / 5 / 7 days before; never stop DAPT after recent stents without cardiology
SGLT2 inhibitors	Omit the day before and the day of surgery
Sulfonylureas	Omit on the day of surgery
Metformin	Usually continue (omit lunchtime dose if three times daily; omit with contrast or low eGFR)
Long-acting insulin	Reduce by about 20%; VRIII if more than one missed meal
Steroids	Continue plus peri-operative cover
Beta-blockers, statins	Continue
ACE inhibitors, ARBs, diuretics	Often omit on the morning of surgery; restart when eating, drinking and stable
Combined pill	Stop 4 weeks before major or immobilising surgery
Lithium	Stop 24 hours before major surgery; restart with normal U&E
Parkinson's drugs, antiseizure drugs, levothyroxine, inhalers	Continue (time-critical where relevant)
GLP-1 agonists / tirzepatide	Tell the anaesthetist -aspiration risk
Herbal remedies	Stop 1–2 weeks before

Spot the Diagnosis

Clue	Diagnosis
Rising end-tidal CO2, jaw rigidity and tachycardia after sevoflurane	Malignant hyperthermia -dantrolene
Prolonged paralysis after suxamethonium; father had the same	Plasma cholinesterase deficiency
Perioral tingling then a seizure during a large laceration repair	Local anaesthetic toxicity -lipid emulsion
Sudden hypotension and bronchospasm after the antibiotic at induction	Perioperative anaphylaxis
Low saturations, fever 37.9 and basal crackles on day 1	Atelectasis
Hypotension and tachycardia 4 hours after thyroidectomy with neck swelling	Reactionary haemorrhage -airway emergency
Day 6 after colectomy: new AF, fever, rising CRP, abdominal pain	Anastomotic leak
Pink serous fluid from a laparotomy wound on day 8	Impending wound dehiscence
Severe wound pain and spreading dusky redness 24 hours after surgery	Early necrotising infection (group A strep or clostridia)
Sudden breathlessness and pleuritic pain on day 9 after hip replacement	PE
No urine for 4 hours, suprapubic fullness after spinal anaesthetic	Urinary retention
Drowsy, confused, sodium 124 after 3 days of IV 5% glucose	Iatrogenic hyponatraemia
Older woman quiet and drowsy on day 2, not eating, constipated	Hypoactive delirium -look for causes
Distended, quiet abdomen with vomiting on day 3 on high-dose morphine, K 3.1	Post-operative ileus
Leg numbness and weakness worsening 12 hours after epidural removal on LMWH	Epidural haematoma -urgent MRI
Raised scar extending beyond the wound on the shoulder	Keloid
Euglycaemic DKA after surgery in a patient who kept taking dapagliflozin	SGLT2 inhibitor not stopped
Hypoglycaemia on the morning of surgery after the usual gliclazide	Sulfonylurea should have been omitted
Collapse and low BP after surgery in a patient on long-term prednisolone	Adrenal crisis -hydrocortisone
NG tube aspirate pH 7.5 and no X-ray	Don't use the tube -position unconfirmed
Swab missing at the end of a laparotomy	Possible retained foreign object (never event) -recount, X-ray
ASA grade for well-controlled hypertension	ASA II
Inflamed non-perforated appendix -wound class	Contaminated
Faecal peritonitis -wound class	Dirty -treatment course

Exam-style Scenarios

1. A 72-year-old man with AF on apixaban 5 mg twice daily (creatinine clearance 55 mL/min) is listed for an elective total hip replacement under spinal anaesthesia. He also takes ramipril and gliclazide.
Answer: Peri-operative medicines plan.

• Apixaban -high bleeding risk with neuraxial anaesthesia: stop at least 48 hours before (last dose 3 days before surgery, per local policy); no bridging; restart full dose once haemostasis is secure (usually 48–72 hours), with prophylactic-dose cover in between as agreed.
• Ramipril -omit on the morning of surgery; restart when eating, drinking and stable. Gliclazide -omit on the day of surgery; monitor glucose.
• VTE prophylaxis, antibiotic prophylaxis within 60 minutes of incision, early mobilisation, delirium prevention.

2. A 64-year-old woman is on day 6 after an anterior resection for rectal cancer. She has new fast AF, a temperature of 38.4°C, increasing abdominal pain and her CRP has risen from 120 to 260.
Answer: Suspected anastomotic leak.

• Sepsis Six -oxygen, blood cultures, IV broad-spectrum antibiotics, fluids, lactate, urine output; rate control is secondary -treat the cause.
• Urgent CT abdomen and pelvis with contrast (including rectal contrast if appropriate); senior surgical review.
• Management depends on findings -radiological drainage of a small collection, or return to theatre (washout, defunctioning stoma or Hartmann's); critical care support.

3. A 78-year-old man is on day 8 after an emergency laparotomy. The nurse reports a large amount of pink fluid soaking his dressing, and now loops of bowel are visible in the wound.
Answer: Wound dehiscence (burst abdomen).

• Reassure; lie flat with knees slightly bent; cover the bowel with warm sterile saline-soaked packs; analgesia; nil by mouth; IV fluids.
• Urgent senior surgical review and return to theatre for closure (or temporary closure if contaminated).
• Look for underlying causes -infection, malnutrition, ileus, coughing, steroids; optimise nutrition.

4. A 60 kg woman is having a large scalp laceration repaired. 30 mL of 1% plain lidocaine has been injected. She complains of tingling lips and a metallic taste, then has a seizure.
Answer: Local anaesthetic systemic toxicity (300 mg = 5 mg/kg -over the 3 mg/kg maximum for plain lidocaine).

• Stop injecting; call for help; airway, 100% oxygen; benzodiazepine for the seizure; cardiac monitoring.
• 20% lipid emulsion -1.5 mL/kg IV bolus, then infusion; treat arrhythmias; prolonged CPR if cardiac arrest.
• Prevention next time -calculate the maximum dose first (plain lidocaine 3 mg/kg = 180 mg = 18 mL of 1%), use lidocaine with adrenaline, report the incident.

5. A 58-year-old man with type 2 diabetes is having a morning laparoscopic cholecystectomy as a day case. He takes metformin twice daily, gliclazide twice daily, dapagliflozin and insulin glargine at night. HbA1c is 62 mmol/mol.
Answer: CPOC peri-operative diabetes plan.

• Dapagliflozin -omit the day before and the day of surgery; gliclazide -omit the morning dose (and until eating normally).
• Metformin -usually take as normal (twice daily regimen); glargine -reduce the evening dose by about 20%.
• First on the list; capillary glucose on arrival and hourly; treat hypoglycaemia; VRIII only if he misses more than one meal or glucose is high; ketone checks if unwell (SGLT2 history).

Key Points

• NCEPOD: immediate, urgent, expedited, elective -emergency surgery carries much higher risk.
• ASA grades I–VI; poor exercise tolerance and frailty predict complications.
• Test only when it changes management; ask about and test for pregnancy.
• Consent must cover material risks and alternatives, including doing nothing (Montgomery); assess capacity for the specific decision.
• Fasting: 6 hours for food, clear fluids up to 2 hours (or "sip til send"); GLP-1 drugs raise aspiration risk.
• Warfarin stop 5 days; DOACs 24–48 hours; aspirin usually continues; never stop DAPT after recent stents without cardiology.
• Omit SGLT2 inhibitors the day before and day of surgery; omit sulfonylureas on the day; never omit steroids.
• WHO checklist: sign in, time out, sign out; never events are preventable.
• Lidocaine maximum 3 mg/kg plain, 7 mg/kg with adrenaline; 1% = 10 mg/mL; treat toxicity with lipid emulsion.
• Malignant hyperthermia -rising ETCO2, rigidity, hyperthermia -dantrolene.
• Antibiotic prophylaxis within 60 minutes before incision; clean surgery needs none unless an implant is used.
• VTE prophylaxis for all at risk; extended 28 days after major cancer surgery.
• Maintenance fluids: 25–30 mL/kg/day water, 1 mmol/kg/day Na, K and Cl, 50–100 g glucose.
• Too much 5% glucose causes hyponatraemia; too much saline causes hyperchloraemic acidosis.
• Post-op fever: early -inflammation/atelectasis; days 3–5 -chest, urine, lines; 5–7 -wound, leak, abscess; after 7 -VTE.
• New AF after bowel surgery -think anastomotic leak.
• Pink serous wound discharge around day 7–10 warns of dehiscence.
• Check the catheter first in oliguria; don't give diuretics to a dry patient.
• Confirm NG tube position by aspirate pH 5.5 or below, or X-ray.

Guidelines and Further Reading

• NICE NG45: Routine preoperative tests for elective surgery
• NICE NG180: Perioperative care in adults
• NICE NG125: Surgical site infections -prevention and treatment
• NICE NG89: Venous thromboembolism in over 16s -reducing the risk
• NICE CG174: Intravenous fluid therapy in adults in hospital
• Centre for Perioperative Care (CPOC): Guideline for perioperative care for people with diabetes; frailty guideline
• Association of Anaesthetists: Guidelines on peri-operative steroid management, local anaesthetic toxicity, malignant hyperthermia, and anaphylaxis
• GMC: Decision making and consent (2020)
• WHO Surgical Safety Checklist; NHS England Never Events framework
• NCEPOD classification of intervention; National Emergency Laparotomy Audit (NELA)
• BNF -for current doses