78 PRE- AND POST-OPERATIVE OPTIMISATION
# 79 PRE- AND POST-OPERATIVE OPTIMISATION
The perioperative period — the hours and days surrounding an operation — is where most preventable surgical morbidity is made or avoided. Good surgeons don't just operate well; they identify risk, modify it where they can, and recognise complications early. This lesson covers the framework MRCS examiners expect you to know: how to assess and optimise a patient before surgery, how to deliver Enhanced Recovery After Surgery (ERAS) principles, and how to diagnose the predictable complications that arise hour-by-hour after the knife goes in.
Pre-operative assessment
The aim is to identify and modify risk before the patient reaches theatre. NICE NG45 frames pre-op investigation around two variables: the patient's ASA grade and the severity of the planned surgery (minor, intermediate, major, complex). No fishing for abnormalities — investigations are requested only when they will change management.
A focused history covers comorbidities, exercise tolerance (the single best bedside marker of cardiopulmonary reserve), previous anaesthetic problems, family history of anaesthetic complications (suxamethonium apnoea, malignant hyperthermia), medications, allergies and smoking/alcohol use. Examination targets airway (Mallampati), cardiovascular and respiratory systems.
ASA physical status classification
| Grade | Description | Example |
|---|---|---|
| I | Normal healthy patient | Fit non-smoker |
| II | Mild systemic disease, no functional limitation | Controlled hypertension, mild asthma, BMI 30–40, smoker |
| III | Severe systemic disease that limits activity but is not incapacitating | Poorly controlled diabetes, stable angina, COPD, BMI >40 |
| IV | Severe systemic disease that is a constant threat to life | Recent MI/stroke (<3 months), ongoing cardiac ischaemia, sepsis |
| V | Moribund patient not expected to survive 24 h without surgery | Ruptured AAA, massive trauma |
| VI | Brain-dead organ donor | — |
👩⚕️ Add an E for emergency surgery (e.g. ASA IIIE). ASA was designed as a descriptor, not a risk score — but examiners use it as shorthand for perioperative risk. Know the wording carefully: the discriminator between II and III is functional limitation.
Routine investigations (NICE NG45)
- Healthy ASA I + minor surgery (e.g. tonsillectomy, ingrowing toenail) ➡ no routine bloods
- ASA II/III ➡ FBC, U&E, ECG depending on age and surgery severity
- All major surgery ➡ FBC + U&E ± group and save
- Coagulation screen only if on anticoagulants, liver disease or known bleeding disorder
- HbA1c if diabetic and not checked in 3 months
- Sickle test in at-risk ethnicities if status unknown
Optimising specific systems
Cardiovascular
Most cardiac drugs are continued through the perioperative period because withdrawal causes rebound:
- Continue: β-blockers (rebound tachycardia and ischaemia if stopped), statins (plaque stabilisation), most antihypertensives
- Hold on morning of surgery: ACE inhibitors and ARBs (refractory intraoperative hypotension), diuretics
- Aspirin: continue for most surgery — particularly vascular and cardiac. Stop only if bleeding risk is catastrophic (intracranial, posterior eye)
- Clopidogrel: stop 7 days before unless drug-eluting stent in situ — discuss with cardiology
- DOACs (apixaban, rivaroxaban, dabigatran): stop 24–48 h before, longer if renal impairment or high-bleeding-risk surgery
- Warfarin: stop 5 days before; bridge with therapeutic LMWH if high thromboembolic risk (mechanical valve, recent VTE, AF with prior stroke). Aim INR <1.5 on day of surgery
Respiratory
Optimise asthma and COPD with inhalers, nebulisers and a short course of oral steroids if wheezy. Smoking cessation for at least 6–8 weeks reduces wound and pulmonary complications; even 24 h helps carboxyhaemoglobin levels. Chest physio and incentive spirometry pre-op reduce post-op atelectasis.
Diabetes
Poor glycaemic control predicts wound infection, anastomotic leak and mortality. HbA1c target <69 mmol/mol (8.5%) before elective surgery — defer if higher and the operation can wait.
- First on the morning list to minimise fasting
- Long-acting insulin (e.g. glargine) ➡ reduce dose by ~20% the evening before
- Omit short-acting insulin and oral hypoglycaemics on the day
- Metformin: hold if contrast or significant renal impairment (risk of lactic acidosis)
- Variable rate intravenous insulin infusion (VRIII / "sliding scale") if the patient will miss more than one meal or has poor control
Steroids
Chronic exogenous steroids suppress the HPA axis; the adrenals can't mount a stress response. Patients on >5 mg prednisolone daily for >3 weeks need stress-dose cover for moderate-to-major surgery: typically IV hydrocortisone 100 mg at induction, then 50 mg 8-hourly for 24–72 h, tapered back to maintenance.
Anaemia
Iron deficiency is the commonest cause and is correctable. If surgery is >6 weeks away, give oral ferrous sulfate. If <6 weeks, oral iron is poorly tolerated, or anaemia of chronic disease is suspected, give IV iron. Transfusion is reserved for symptomatic or very low Hb — restrictive thresholds (Hb 70 g/L) reduce mortality compared to liberal transfusion.
Fasting (RCoA "2 and 6" rule)
- 2 hours for clear fluids (water, black tea/coffee, clear cordial)
- 6 hours for solids and milk
- Prolonged fasting increases insulin resistance, dehydration and post-op nausea — hence ERAS encourages clear carbohydrate drinks up to 2 h pre-op.
VTE prophylaxis
All surgical inpatients need a VTE risk assessment within 14 h of admission.
- Mechanical: TED stockings, intermittent pneumatic compression (IPC). Used alone if bleeding risk is high or pharmacological prophylaxis contraindicated (recent intracranial haemorrhage, active major bleeding, platelets <75)
- Pharmacological: LMWH (enoxaparin 40 mg SC once daily). Reduce dose in renal failure (eGFR <30) — typically 20 mg OD or switch to unfractionated heparin
- Extended prophylaxis (28 days) after major pelvic/abdominal cancer surgery and hip/knee arthroplasty
WHO Surgical Safety Checklist
A 19-item checklist credited with reducing perioperative mortality by ~40% in trial settings. Three phases:
1. Sign-in — before induction: patient ID, site marked, allergies, airway risk, blood availability
2. Time-out — before skin incision: team introductions, confirm patient/procedure/site, antibiotic prophylaxis given, imaging displayed, anticipated critical events
3. Sign-out — before patient leaves theatre: procedure recorded, instrument/swab counts, specimens labelled, equipment problems, recovery plan
Enhanced Recovery After Surgery (ERAS)
ERAS is an evidence-based bundle designed to reduce the surgical stress response and accelerate return to baseline. The consistent trial benefit is shorter length of stay — morbidity and mortality benefits are smaller but real.
| Phase | Key elements |
|---|---|
| Pre-op | Patient education, optimisation of comorbidities, smoking/alcohol cessation, no prolonged fasting, carbohydrate loading 2 h pre-op, no routine bowel prep (except for left-sided/rectal cases), pre-op antiemetic |
| Intra-op | Minimally invasive technique, short-acting anaesthetics, regional/epidural analgesia, normothermia (warming devices), goal-directed fluid therapy (avoid excess), antibiotic prophylaxis within 60 min of incision |
| Post-op | Multimodal opioid-sparing analgesia, early removal of catheters and drains, early oral intake, early mobilisation (day 0–1), no routine NG tubes |
👩⚕️ Carbohydrate loading drinks (e.g. 800 ml the evening before, 400 ml 2 h before) reduce post-op insulin resistance and preserve nitrogen balance, blunting the catabolic stress response. Omit in diabetics on complex insulin regimens.
Surgical risk scoring
- ASA — quick global assessment of physical status
- POSSUM / P-POSSUM — Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity. Combines 12 physiological and 6 operative variables to predict 30-day morbidity and mortality. Used for audit and risk prediction, particularly emergency laparotomy (NELA)
- Charlson Comorbidity Index — long-term prognosis based on comorbidities
- APACHE II — ICU scoring system, not a perioperative tool
Post-operative complications by time
The classic exam framework. Memorise the time windows — examiners love a "day 5 fever" vignette.
| Timeframe | Complication |
|---|---|
| Immediate (<24 h) | Primary haemorrhage (intra-op bleeding continuing), reactionary haemorrhage (within 24 h, as BP normalises and clots dislodge), atelectasis, anaesthetic complications, urinary retention |
| Early (24–72 h) | Atelectasis progressing to chest infection, UTI (catheter), paralytic ileus, MI, secondary haemorrhage (5–10 days, classically infection-related vessel erosion) |
| Late (>72 h) | Wound infection (day 3–7), anastomotic leak (day 5–7), DVT/PE (day 7–10), pressure sores, incisional hernia (months) |
The 5 Ws of post-op pyrexia
| Day | "W" | Cause |
|---|---|---|
| 1–2 | Wind | Atelectasis ➡ commonest cause of POD1 fever |
| 3–5 | Water | UTI (catheter) |
| 5–7 | Wound | Surgical site infection / anastomotic leak |
| 7–10 | Walking | DVT/PE |
| Any | Wonder drugs | Drug fever, transfusion reaction |
Post-op hypoxia
A drop in SpO₂ is one of the commonest crash-call triggers. Think in three buckets:
- V/Q mismatch: atelectasis (commonest), pneumonia, PE, pulmonary oedema
- Hypoventilation: opioids, residual neuromuscular blockade, pain-limited splinting
- Shunt: consolidation, ARDS
Sit the patient up, give oxygen, treat the cause. Incentive spirometry and chest physio are key.
Post-op oliguria
Defined as urine output <0.5 ml/kg/h. Always work through the three categories:
- Pre-renal (commonest): hypovolaemia (under-resuscitation, ongoing bleeding, third-space losses), sepsis, cardiogenic. Treat with a fluid challenge (250–500 ml crystalloid)
- Renal: acute tubular necrosis from prolonged hypoperfusion, nephrotoxins (NSAIDs, gentamicin, contrast)
- Post-renal: blocked catheter (flush it first — the cheapest diagnostic test in surgery), urinary retention, ureteric injury
Post-op confusion (delirium)
Especially common in the elderly. Remember PINCH ME:
- Pain
- Infection (chest, urine, wound)
- Nutrition (refeeding, hypoglycaemia)
- Constipation
- Hydration (dehydration or overload, hyponatraemia)
- Medication (opioids, anticholinergics, benzodiazepine withdrawal)
- Environment (unfamiliar ward, sensory deprivation, sleep disruption)
Hypoxia and alcohol withdrawal are easy marks — always check the SpO₂ and the drinking history.
Refeeding syndrome
Covered in detail in Lesson 45. Quick recap: in the malnourished patient, reintroduction of carbohydrate triggers insulin release, driving phosphate, potassium and magnesium intracellularly. Severe hypophosphataemia causes cardiac and respiratory failure. Start feeding at 5–10 kcal/kg/day, replace electrolytes and supplement thiamine before any carbohydrate.
Stress response to surgery
Tissue injury triggers a neuroendocrine cascade: sympathetic activation, ACTH/cortisol release, catecholamines, ADH and aldosterone. Net result: catabolism (protein breakdown, lipolysis, gluconeogenesis), sodium and water retention, hyperglycaemia, and an acute-phase response. CRP rises within 6 h, peaks at ~48 h. Albumin and transferrin (negative acute-phase reactants) fall. ERAS, regional anaesthesia and minimally invasive surgery all attenuate this response.
Which blood test should you do for a 14-year-old undergoing elective tonsillectomy?
- ((FBC::Not routinely needed in a healthy child for minor surgery per NICE NG45.))
- ((Clotting::Only if bleeding history, anticoagulant use or liver disease.))
- ((U&E::Not needed in healthy ASA I without renal risk factors.))
- ((All of the above::Routine investigation panels are explicitly discouraged by NICE.))
- ((None of the above::☑️ ASA I + minor surgery + no bleeding history — no routine bloods required.))
👩⚕️ NICE NG45 stratifies by ASA and surgical severity; "shotgun" pre-op panels are wasteful and generate false positives.
A patient is scheduled for haemorrhoid surgery in 6 weeks. His haemoglobin is 9 g/dL. How should his anaemia be managed pre-operatively?
- ((Blood transfusion::Reserved for symptomatic or very low Hb; not first line for elective optimisation.))
- ((Plasma transfusion::Treats coagulopathy, not anaemia.))
- ((IV iron::Preferred if surgery is <6 weeks away or oral iron not tolerated.))
- ((Oral iron::☑️ Six weeks is enough time for oral ferrous sulfate to replenish stores.))
- ((Folic acid::Treats megaloblastic anaemia, not iron deficiency.))
👩⚕️ The "6-week rule" decides oral vs IV iron. Anaemia of chronic disease (ferritin 30–100, TSAT <20%) doesn't respond to oral iron — give IV.
A man on 15 mg daily prednisolone for asthma is scheduled for emergency surgery after bilateral tibia and fibula fractures. What is the most appropriate perioperative steroid plan?
- ((Continue normal dose only::Inadequate — suppressed HPA axis cannot mount a stress response.))
- ((Omit steroids on day of surgery::Risks acute adrenal crisis.))
- ((Reduce dose perioperatively::Wrong direction — stress demands more, not less.))
- ((Stress-dose IV hydrocortisone at induction, then 8-hourly for 24–72 h::☑️ Covers the cortisol surge a suppressed adrenal cannot produce.))
👩⚕️ Threshold for stress dosing: >5 mg prednisolone for >3 weeks undergoing moderate-to-major surgery.
A 21-year-old skier arrives in ED with a core temperature of 29°C after being trapped in snow. What is the most effective rewarming method?
- ((Electric blankets::External rewarming — adequate for mild hypothermia (32–35°C) only.))
- ((Increase room temperature::Passive external rewarming — too slow for severe hypothermia.))
- ((Warm intravesical fluid::Limited surface area; minimal core warming.))
- ((Warm rectal fluid::Same problem — small contact area.))
- ((Warmed intraperitoneal lavage::☑️ Active core rewarming for severe hypothermia (<30°C).))
👩⚕️ Mild (32–35°C) ➡ external. Severe (<30°C) or cardiovascular instability ➡ active core (peritoneal/thoracic lavage, heated humidified O₂, ECMO/bypass if arrest).
A 66-year-old diabetic on metformin is found to have a lactic acidosis pre-op. What is the most likely cause?
- ((Diabetic ketoacidosis::Would show ketones and a different anion gap profile.))
- ((Metformin-associated lactic acidosis::☑️ Particularly with renal impairment or contrast exposure.))
- ((Prolonged procedure::Surgery hasn't happened yet.))
- ((Prolonged vomiting::Causes hypochloraemic metabolic alkalosis.))
👩⚕️ Hold metformin around contrast studies and if eGFR is borderline; it's the classic SBA trap.
Which of the following is NOT part of an ERAS protocol?
- ((Oral carbohydrate drink 2 h pre-op::Core ERAS element — reduces post-op insulin resistance.))
- ((Pre-op anti-emetic::Part of multimodal nausea prophylaxis.))
- ((Epidural analgesia::Opioid-sparing regional technique encouraged by ERAS.))
- ((Pre-operative diazepam::☑️ Sedatives are avoided — they impair early mobilisation and oral intake.))
- ((Early mobilisation::Cornerstone of ERAS.))
What is the main benefit of pre-operative carbohydrate loading?
- ((Decreases post-operative insulin resistance and preserves nitrogen balance::☑️ Blunts the catabolic surgical stress response.))
- ((Better abdominal muscle function::Not the primary mechanism.))
- ((Better respiratory muscle function::Indirect at best.))
- ((Shorter hospital stay::A downstream outcome, not the mechanism.))
👩⚕️ Omit carbohydrate drinks in diabetics on complex insulin regimens.
What is the most consistently demonstrated benefit of ERAS in trials?
- ((Reduced length of hospital stay::☑️ The most reproducible ERAS outcome across surgical specialties.))
- ((Reduced mortality::Smaller signal, harder to demonstrate.))
- ((Reduced major complications::Some reduction but less consistent.))
- ((Reduced minor complications::Variable across studies.))
A patient is undergoing small bowel resection on an ERAS protocol. Which is best practice?
- ((Minimally invasive (laparoscopic) approach::☑️ Less trauma, less ileus, faster recovery.))
- ((Liberal opioid use::Opioids cause ileus and delay recovery — minimise.))
- ((Liberal IV fluids::Excess fluid causes gut wall oedema and prolongs ileus.))
- ((Routine nasogastric tube::Avoided unless specifically indicated.))
A patient had a sigmoid cancer resection. Which is best practice per ERAS?
- ((30-day follow-up::Standard care, not ERAS-specific.))
- ((Remove urinary catheter on day 1::☑️ Encourages mobilisation and reduces UTI risk.))
- ((Pre- and post-op opiates::ERAS uses multimodal opioid-sparing analgesia.))
- ((Pre-op mechanical bowel prep::Avoided in ERAS for most colonic surgery.))
A young man is very anxious pre-operatively and is tachycardic. What is the physiological mechanism?
- ((Noradrenaline from adrenal medulla::The medulla secretes predominantly adrenaline (~80%).))
- ((Adrenaline from sympathetic nerves::Sympathetic post-ganglionic fibres release noradrenaline.))
- ((Noradrenaline from sympathetic nerves::Contributes, but circulating tachycardia is mainly adrenal.))
- ((Increased circulating noradrenaline::Smaller contributor than adrenal adrenaline in acute stress.))
- ((Adrenaline from the adrenal medulla::☑️ Acute stress drives medullary catecholamine release — mainly adrenaline.))
Which is the most effective single measure to reduce surgical site infection in elective colorectal surgery?
- ((Immediate pre-op shaving::Increases SSI — clip if needed, don't shave.))
- ((Pre-op skin cleaning with antiseptic::Important but lesser effect than systemic antibiotics.))
- ((Theatre zoning::Minor contribution in modern theatres.))
- ((Pre-op antibiotic prophylaxis within 60 min of incision::☑️ Largest single SSI-reducing intervention in colorectal surgery.))
👩⚕️ Skin antisepsis (alcoholic chlorhexidine) and timely IV antibiotics are both tested. Read the stem — the question asks which is most effective.
A patient with intracranial injury and a closed femur fracture. Which marker will be most elevated at 24 h?
- ((Albumin::Falls — negative acute-phase reactant.))
- ((Transferrin::Falls — negative acute-phase reactant.))
- ((Red cells::No rapid rise; may fall with blood loss.))
- ((CRP::☑️ Rises within 6 h of tissue injury, peaks ~48 h.))
What is a systemic effect of the surgical stress response?
- ((Increased protein breakdown::☑️ Cortisol and catecholamines drive catabolism.))
- ((Increased protein synthesis::Opposite — net negative nitrogen balance.))
- ((Enhanced glycogen storage::Glycogenolysis predominates.))
- ((Reduced lipolysis::Lipolysis is increased to mobilise energy.))
Which scoring system is NOT routinely used in the perioperative period?
- ((ASA::Standard perioperative physical-status grade.))
- ((POSSUM::Surgical audit and 30-day morbidity/mortality prediction.))
- ((Charlson Comorbidity Index::Long-term prognosis based on comorbidities.))
- ((APACHE II::☑️ An ICU scoring system for critically ill patients — not a perioperative tool.))
A 36-year-old woman develops a fever within 24 h of cholecystectomy. Most likely cause?
- ((Atelectasis::☑️ Commonest cause of fever in the first 48 h, especially after upper abdominal surgery.))
- ((Wound infection::Typically presents day 3–7.))
- ((Anastomotic leak::Day 5–7; uncommon after cholecystectomy.))
- ((DVT/PE::Typically day 7–10.))
- ((UTI::More likely day 3–5, especially with a catheter.))
👩⚕️ The 5 Ws map fever to post-op day: Wind, Water, Wound, Walking, Wonder drugs.
A patient is 36 h post-laparotomy with urine output of 0.3 ml/kg/h. Catheter flushes freely. Next step?
- ((500 ml crystalloid fluid challenge::☑️ Pre-renal hypovolaemia is the commonest cause of post-op oliguria.))
- ((Start renal-dose dopamine::Not evidence-based; abandoned.))
- ((IV furosemide::Will worsen pre-renal AKI.))
- ((Urgent renal ultrasound::Reserved if obstruction suspected and catheter patent.))
An 82-year-old is confused on post-op day 2 after hip surgery. Which is NOT part of the standard delirium screen?
- ((Pain assessment::P in PINCH ME.))
- ((Septic screen — chest, urine, wound::I in PINCH ME.))
- ((Review of opioids and anticholinergics::M in PINCH ME.))
- ((Routine CT head as first-line investigation::☑️ Imaging only if focal signs or trauma — not part of the routine PINCH ME workup.))
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Revision summary
- ASA grades: I healthy, II mild systemic, III severe with functional limitation, IV constant threat to life, V moribund. Add E for emergency.
- NICE NG45: investigations driven by ASA + surgery severity. Healthy ASA I + minor op ➡ no routine bloods.
- Drugs perioperatively: continue β-blockers, statins, most antihypertensives. Hold ACEi/ARB and diuretics on the day. Stop DOACs 24–48 h, warfarin 5 days (bridge LMWH if high VTE risk).
- Steroids: stress dose if >5 mg prednisolone for >3 weeks + moderate-to-major surgery.
- Diabetes: HbA1c <69 mmol/mol; first on list; VRIII if prolonged NBM; hold metformin if contrast/renal risk.
- Anaemia: oral iron if >6 weeks to surgery, IV iron if <6 weeks.
- Fasting (2 and 6): 2 h clear fluids, 6 h solids/milk.
- VTE: LMWH (enoxaparin 40 mg OD; reduce in renal failure) + mechanical. Mechanical alone if bleeding risk.
- WHO checklist: sign-in, time-out, sign-out.
- ERAS = blunt the stress response. Carb load 2 h pre-op, regional/opioid-sparing analgesia, no NG, restrictive fluids, early catheter removal, early feeding, early mobilisation. Main proven benefit: shorter LOS.
- POSSUM/P-POSSUM: surgical audit risk score. APACHE is ICU.
- Post-op complications by time: <24 h primary/reactionary haemorrhage + atelectasis; 24–72 h chest infection, UTI, ileus; >72 h wound infection (D3–7), anastomotic leak (D5–7), DVT/PE (D7–10).
- 5 Ws of pyrexia: Wind, Water, Wound, Walking, Wonder drugs.
- PINCH ME for delirium: Pain, Infection, Nutrition, Constipation, Hydration, Medication, Environment.
- Stress response: catabolic; CRP rises in 6 h, peaks 48 h. Albumin/transferrin fall.