Surgery chapters
Preoperative optimisation, anaesthesia and pain relief, postoperative care, critical care and day-case surgery
How surgical patients are assessed and optimised before surgery, the essentials of general, local and regional anaesthesia, pain control, the common postoperative complications, levels of critical care, and who is suitable for day-case surgery.
- Preoperative assessment finds and optimises risk: ASA grade, exercise capacity (4 METs = two flights of stairs), heart, lungs, diabetes and drugs; fast 6 hours for solids, 2 hours for clear fluids.
- Suxamethonium is the fastest-acting relaxant but can cause hyperkalaemia and trigger malignant hyperthermia (treat with dantrolene); lidocaine's ceiling is 3 mg/kg plain, 7 mg/kg if adrenaline is added, and bupivacaine is the most cardiotoxic.
- Day surgery suits ASA 1–2 (stable 3) patients for operations up to about 2 hours, with a responsible adult at home for 24 hours.
On this page
Overview
Surgery is a planned injury. Major surgery raises oxygen demand by about 40%, and the stress response, clotting changes and fluid shifts last for days. Good perioperative care spots high-risk patients early, improves their fitness, gives safe anaesthesia and analgesia, catches complications quickly and sends patients home as soon as it is safe, often the same day.
Preoperative assessment and optimisation
History, examination and tests
- Ask about cardiac (angina, MI, failure, arrhythmia), respiratory (COPD, asthma, sleep apnoea), diabetes, liver and kidney disease, bleeding or clotting problems, previous anaesthetic problems (suxamethonium apnoea, malignant hyperthermia in family), drugs, allergies, smoking and alcohol.
- Airway assessment: modified Mallampati grades 1–4 (grade 1: soft palate, fauces, uvula and pillars seen; grade 4: only hard palate seen) predicts difficult intubation.
- Tests are chosen by patient and operation, not routinely: FBC (major surgery, elderly, anaemia), U&E (major surgery, over 65, renal disease, diuretics), ECG (older or cardiac patients), glucose and HbA1c, coagulation if on anticoagulants or liver disease, sickle test in at-risk ethnic groups, group and save or crossmatch if bleeding is expected.
Grading risk
| ASA grade | Description |
|---|---|
| 1 | Normal healthy patient |
| 2 | Mild systemic disease, no functional limit |
| 3 | Severe systemic disease with definite functional limit |
| 4 | Severe disease posing a constant threat to life |
| 5 | Moribund, not expected to survive without the operation |
| 6 | Brain-dead organ donor ("E" is added for emergency surgery) |
Other tools: POSSUM/P-POSSUM (predicts mortality and morbidity), revised cardiac risk index (Lee) (ischaemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, creatinine over 177 µmol/L, high-risk surgery), APACHE II in ICU.
Exercise capacity: 1 MET is resting oxygen use (3.5 mL/kg/min). 4 METs = climbing two flights of stairs. Patients who cannot reach 4 METs have higher cardiac risk; cardiopulmonary exercise testing can quantify this.
The typical high-risk patient is elderly, has ischaemic heart disease and/or COPD, and needs major or emergency surgery. High-risk patients make up most postoperative deaths, yet many never reach a critical care bed.
Optimising common conditions
| Problem | What to do |
|---|---|
| Recent MI / coronary stent | Delay elective surgery; keep dual antiplatelets for about 6 weeks after a bare-metal stent and 12 months after a drug-eluting stent; if surgery cannot wait, decide jointly with cardiology (usually continue aspirin) |
| Warfarin (AF) | Stop 5 days before, aim for INR ≤1.5; bridge with heparin only if thrombotic risk is high (mechanical valve, high CHA2DS2-VASc) |
| Mechanical valve | Stop warfarin 5 days before, start unfractionated heparin when INR < 1.5, stop it 2 hours before surgery; DOACs are not used for mechanical valves |
| DOACs (apixaban, rivaroxaban, dabigatran) | Stop usually 2–3 days before (longer if renal impairment) |
| Pacemaker / ICD | Check and reprogramme; bipolar diathermy preferred; monopolar current may be sensed as VF |
| COPD/asthma | Treat exacerbations first, continue inhalers, stop smoking, physiotherapy; severe disease: FEV1 under 30% predicted or PaCO2 over 6 kPa |
| Diabetes | HbA1c below about 69 mmol/mol for elective surgery; first on the list; check glucose 2-hourly; variable-rate insulin infusion for major surgery in insulin-treated patients |
| Long-term steroids | Give extra perioperative steroid cover to avoid Addisonian crisis |
| Anaemia | Find the cause and treat with iron before elective surgery |
| Malnutrition | BMI < 18.5; feed for at least 2 weeks before major surgery |
Fasting
| Intake | Stop before anaesthesia |
|---|---|
| Solids (food, milk-based drinks) | 6 hours |
| Breast milk (infants) | 4 hours |
| Clear fluids (water, isotonic drinks) | 2 hours |
Usual medicines are taken with sips of water. A carbohydrate drink up to 2 hours before surgery reduces thirst, anxiety and postoperative insulin resistance (part of enhanced recovery programmes). Patients with hiatus hernia, obesity, pregnancy or diabetes remain at aspiration risk; give an H2 blocker or PPI.
Anaesthesia
General anaesthesia
Triad: unconsciousness (amnesia), analgesia and muscle relaxation.
| Induction agent | Key features |
|---|---|
| Propofol | Commonest; smooth, rapid recovery, anti-emetic; used for infusion (TIVA) and day surgery; causes hypotension |
| Thiopentone | Rapid; lowers intracranial pressure; myocardial depression and hypotension |
| Etomidate | Most cardiovascularly stable; suppresses adrenal cortex |
| Ketamine | Keeps blood pressure and airway reflexes, strong analgesia; field and trauma use; emergence delirium |
Maintenance is with an infusion of propofol or a volatile agent (sevoflurane, isoflurane, desflurane). Nitrous oxide is used less because it causes nausea and expands gas spaces (bowel, middle ear, pneumothorax).
| Muscle relaxant | Notes |
|---|---|
| Suxamethonium (depolarising) | Fastest onset, shortest action; for rapid intubation. Side effects: muscle pains, hyperkalaemia (avoid after burns, crush, denervation from about day 2), prolonged apnoea (pseudocholinesterase deficiency), malignant hyperthermia, bradycardia |
| Rocuronium | Rapid onset; alternative for rapid sequence induction; reversed quickly by sugammadex |
| Atracurium | Broken down in plasma (Hofmann degradation), so safe in liver and renal failure; releases histamine |
| Vecuronium | Needs liver and kidney for clearance |
Rapid sequence induction (preoxygenation, induction agent plus fast relaxant, cricoid pressure, cuffed tube) is used when there is aspiration risk: full stomach, bowel obstruction, pregnancy, emergency surgery.
Minimum monitoring: ECG, blood pressure, pulse oximetry, inspired oxygen and end-tidal CO2; plus temperature, urine output and CVP for major cases.
Malignant hyperthermia
- Autosomal dominant defect of the muscle calcium release channel (ryanodine receptor, RYR1).
- Triggered by volatile agents and suxamethonium.
- Signs: rising end-tidal CO2 (earliest), tachycardia, muscle rigidity (masseter spasm), rapidly rising temperature, acidosis, hyperkalaemia, myoglobinuria.
- Treatment: stop the trigger, 100% oxygen, IV dantrolene, cool, treat potassium and acidosis. Family members need testing.
Local anaesthetics
They block sodium channels in nerve membranes; thin, unmyelinated fibres (pain, temperature, autonomic) are blocked first.
| Drug | Maximum dose | Notes |
|---|---|---|
| Lidocaine (lignocaine) | 3 mg/kg plain; 7 mg/kg if adrenaline added | Rapid onset, short acting |
| Bupivacaine | 2 mg/kg | Long acting; most cardiotoxic; never for IV regional (Bier's) block |
| Levobupivacaine / ropivacaine | 2 mg/kg / 3–4 mg/kg | Less cardiotoxic |
| Prilocaine | 6 mg/kg plain; 9 mg/kg if adrenaline added | Least toxic; drug of choice for Bier's block; causes methaemoglobinaemia |
1% solution = 1 g in 100 mL = 10 mg/mL; 2% = 20 mg/mL
10 mL of 2% lidocaine = 200 mg
Maximum plain dose for 70 kg = 3 × 70 = 210 mg → about 10.5 mL of 2% or 21 mL of 1%
- Adrenaline speeds onset, prolongs action and allows a higher dose, but avoid it in end-arteries (digits, penis) and in patients with heart disease or on MAOIs or tricyclics.
- Toxicity: perioral tingling, metallic taste, tinnitus, agitation → seizures → arrhythmia and cardiac arrest. Stop injecting, ABC, treat fits, and give IV lipid emulsion (20% Intralipid) for severe toxicity.
- LA works poorly in acidic, infected tissue (abscess): less drug is un-ionised to cross membranes. Esters cause allergy more often than amides.
Spinal versus epidural
| Feature | Spinal (intrathecal) | Epidural |
|---|---|---|
| Onset | Fast, dense block | Slower |
| Duration | Single shot, limited | Catheter: top-ups and infusions for days |
| Dose | Small | Large volume |
| Problems | Hypotension (sympathetic block, worse above T10), post-dural puncture headache (reduced with fine pencil-point needles), urinary retention | Hypotension, failed or patchy block, accidental intrathecal or IV injection, epidural haematoma or abscess |
Hypotension with a warm periphery in a patient on an epidural infusion is usually sympathetic block, not bleeding; but always exclude hypovolaemia.
Other blocks: TAP block (local anaesthetic between internal oblique and transversus abdominis, numbing the anterior abdominal wall), rectus sheath, interscalene (can block the phrenic nerve and cause Horner's), femoral and sciatic blocks. Ultrasound guidance improves success and safety.
Pain relief
- Multimodal analgesia: regular paracetamol + NSAID (if safe) + local or regional block, with opioids only for severe pain.
- WHO analgesic ladder (cancer pain): step 1 non-opioid; step 2 weak opioid (codeine, tramadol); step 3 strong opioid (morphine), with adjuvants at every step.
- Patient-controlled analgesia (PCA): small IV morphine boluses on demand with a lockout interval that stops a new dose before the last one has acted, preventing overdose. Only the patient presses the button.
- Opioid toxicity: drowsiness, slow breathing, pinpoint pupils → stop the opioid, oxygen, IV naloxone. Risk is higher in renal failure (metabolites accumulate).
- Thoracic epidural gives the best analgesia after laparotomy or thoracotomy and for multiple rib fractures, aiding coughing and early return of gut function.
Postoperative care
All patients recover in a staffed recovery unit (PACU) with monitored airway, breathing, circulation, pain, nausea and temperature.
Postoperative fever: think by timing
| Time after surgery | Common causes |
|---|---|
| First 48 hours | Inflammatory response to surgery, atelectasis, transfusion or drug reaction |
| Days 3–5 | Chest infection, urinary infection, IV cannula phlebitis |
| Days 5–7 | Wound infection, anastomotic leak, intra-abdominal collection |
| After the first week | DVT/PE, deep collections, drug fever |
About 40% of patients have a fever after major surgery, often with no infection found; but always look for a focus.
Main complications
- Respiratory: atelectasis (commonest, especially after upper abdominal surgery), pneumonia, aspiration, PE. Prevent with analgesia, physiotherapy, early mobilisation, stopping smoking.
- Cardiovascular: hypotension (hypovolaemia, bleeding, epidural, sepsis), hypertension, arrhythmia (correct K+ and Mg2+), MI (often silent), stroke. Cardiac causes lead deaths in the first 30 days after non-cardiac surgery.
- Renal: oliguria (under 0.5 mL/kg/h); usually pre-renal (hypovolaemia, hypotension); first check the catheter is not blocked; avoid nephrotoxins (NSAIDs, gentamicin). Urinary retention is common after hernia, anal and spinal surgery.
- Postoperative nausea and vomiting (PONV): risk factors (Apfel): female sex, non-smoker, previous PONV or motion sickness, postoperative opioids. Use combinations: ondansetron, dexamethasone, cyclizine, prochlorperazine.
- Bleeding:
- Primary: during surgery.
- Reactionary: within about 4–6 hours (slipped ligature, clot dislodged as BP rises).
- Secondary: usually 7–10 days, from infection eroding a vessel.
- DVT/PE: risk-assess every patient; stockings, calf pumps and LMWH; highest risk with hip/knee replacement and pelvic surgery.
- Wound dehiscence: in up to 3% of laparotomies, most often days 5–8; a serosanguinous ("pink") discharge is the warning sign. Risks: malnutrition, diabetes, obesity, jaundice, uraemia, sepsis, cancer, steroids, poor technique. Most need resuturing.
- Delirium: common in the elderly; look for hypoxia, sepsis, urinary retention, electrolyte upset (hyponatraemia), drugs, alcohol withdrawal and hypoglycaemia.
- Hypothermia (shivering, coagulopathy, infection) and pressure sores (sacrum, heels) are prevented by warming, padding and early mobilisation.
Critical care
| Level | Patient | Nursing |
|---|---|---|
| 0 | Ward care is enough | Ward |
| 1 | At risk of deterioration or recently stepped down; needs outreach input | Ward with extra support |
| 2 (high dependency) | Needs single organ support or detailed monitoring | About 1 nurse : 2 patients |
| 3 (intensive care) | Advanced respiratory support or support of two or more organs | About 1 nurse : 1 patient |
- Early warning scores (NEWS2) on the ward trigger review; a NEWS2 of 5 or more suggests high risk (e.g. sepsis). Critical care outreach teams bridge ward and ICU ("critical care without walls").
- qSOFA (respiratory rate ≥22, systolic BP ≤100 mmHg, altered mental state) flags possible sepsis outside ICU.
- ARDS (Berlin): acute onset, bilateral infiltrates not explained by heart failure, graded by PaO2/FiO2 on PEEP of at least 5 cmH2O: mild 200–300, moderate 100–200, severe < 100 mmHg. Ventilate with low tidal volumes (about 6 mL/kg ideal body weight) and plateau pressure ≤30 cmH2O; prone positioning in severe cases.
- Routine ICU care: VTE and stress ulcer prophylaxis, glucose control, early enteral feeding, limiting sedation.
Day-case surgery
Definition: admission, operation and discharge on the same working day (an overnight stay is a "23-hour stay").
| Selection area | Criteria |
|---|---|
| Medical | Judge physiological, not chronological, age; ASA 1–2, and stable ASA 3 after review; BMI under 40 is not by itself a bar |
| Social | Responsible adult carer for 24 hours; suitable home; telephone access; reasonable travel distance |
| Surgical | Operation up to about 2 hours; low risk of major bleeding; pain controllable with oral drugs; early eating and drinking expected |
Examples: hernia repair, laparoscopic cholecystectomy, haemorrhoidectomy, breast lump excision, arthroscopy.
Anaesthesia: propofol-based, short-acting agents, local infiltration and blocks; regular paracetamol and NSAIDs; avoid long-acting opioids (sedation and PONV); IV fluids and antiemetics.
Discharge criteria: stable vital signs for at least 1 hour; fully oriented; pain controlled with oral analgesics; minimal nausea; able to walk; drinking; minimal wound bleeding; passed urine (where relevant); adult escort home; written instructions and an emergency contact number. Patients must not drive or sign legal documents for 24 hours after general anaesthesia.
After laparoscopic surgery in a young fit patient, covert bleeding may be hidden by compensation; a rising pulse before discharge needs review. After tonsillectomy, watch for reactionary bleeding in the first 6 hours.
Expect: ASA grades, 4 METs, fasting times, stopping warfarin and antiplatelets, diabetes and steroid cover, induction agents (propofol for day cases, ketamine for trauma), suxamethonium side effects and malignant hyperthermia, atracurium in organ failure, local anaesthetic maximum doses, toxicity and Bier's block, spinal versus epidural complications, PCA lockout and opioid toxicity, causes of fever by day, PONV risk factors, timing of reactionary and secondary haemorrhage and wound dehiscence, levels of critical care and ARDS, and day surgery selection and discharge criteria.
Quick revision
- ASA 1 healthy → 5 moribund; under 4 METs = higher risk.
- Fasting: solids 6 h, breast milk 4 h, clear fluids 2 h.
- Warfarin off 5 days (INR ≤1.5); DES: wait 12 months for elective surgery.
- Suxamethonium: hyperkalaemia, apnoea, malignant hyperthermia (dantrolene).
- Lidocaine 3 mg/kg plain, 7 mg/kg if adrenaline added; bupivacaine 2 mg/kg, never in Bier's block; prilocaine for Bier's.
- Spinal: fast, hypotension, headache; epidural: catheter, slower, haematoma risk.
- Fever: day 1–2 atelectasis/inflammation; 3–5 chest/urine; 5–7 wound/leak; later DVT.
- Reactionary bleed 4–6 h; secondary bleed 7–10 days; dehiscence days 5–8.
- Level 2 = one organ supported; level 3 = ventilation or two or more organs.
- Day case: ASA 1–2, up to 2 h, adult carer 24 h.
Written by The House Job from standard references (Bailey & Love; Kumar and Clark's Clinical Medicine).
FAQ
Why is suxamethonium avoided a few days after a major burn?
Burned and denervated muscle grows extra acetylcholine receptors across its surface, so suxamethonium releases a large amount of potassium and can cause fatal hyperkalaemia.
Why must bupivacaine never be used for Bier's block?
It is the most cardiotoxic local anaesthetic; if the tourniquet fails, a large dose enters the circulation and can cause intractable ventricular arrhythmia and cardiac arrest.
What is the purpose of the lockout interval on a PCA pump?
It prevents a new dose being given before the previous one has had its full effect, so the patient cannot stack doses and overdose.
Who can go home after day-case surgery?
A patient with stable observations, controlled pain on oral drugs, little nausea, who can drink, walk and pass urine, and who has a responsible adult to escort them and stay for 24 hours.