GC002 Is He Fit For Surgery - Pre-operative Assessment
Pre-operative assessment is a systematic evaluation of a patient's medical history, physical status, and risk factors to determine their fitness for surgery and optimize outcomes.
Pre-operative Assessment: "Is the Patient Fit for Surgery?"
The Big Idea: Before any surgery, you must answer one critical question: does this patient have enough physiological reserve to tolerate the combined stress of surgery and anaesthesia, and recover afterwards? Pre-operative assessment is the systematic process of estimating that reserve, identifying modifiable risk factors, optimizing the patient, planning perioperative care, and communicating uncertainty and options to the patient and the surgical team. “Fit” is not a binary label: the output is an individualized risk estimate and a shared plan.
Learning Objectives (from the lecture): [1]
- Describe some of the physiological stresses experienced by the perioperative patient
- Describe interactions between surgery and coexisting diseases in the perioperative patient
- Explain the purposes and describe the major elements of a preoperative anaesthetic assessment
1. Why Does the Patient Need to Be Fit? — Physiological Stresses of Surgery
This is the conceptual foundation of the lecture. Surgery is a controlled injury. The body must mount a physiological response to that injury — and that response demands energy and organ reserve.
The opening slide deliberately calls fitness a nebulous, task-specific term. General physical fitness includes body composition, flexibility and endurance, but “fit for surgery” means enough physiological reserve to meet the demands of this particular operation, anaesthetic and recovery pathway. A person may be independent in daily life yet lack reserve for a major vascular operation; another may be unable to climb stairs for musculoskeletal reasons while retaining good cardiorespiratory reserve. This is why the assessment cannot be reduced to age, appearance or one exercise question.
"Surgery can increase metabolic demands and/or reduce supply" [1]
| Stress Category | Mechanism | Why It Matters |
|---|---|---|
| Acute "sterile" inflammation (SIRS) | Tissue damage triggers cytokine release (IL-1, IL-6, TNF-α), complement activation, and neutrophil migration — identical to the inflammatory cascade in infection, but without bacteria | Even sterile surgery can produce a systemic inflammatory response; the bigger the surgery, the bigger the response |
| Metabolic and neuroendocrine disturbances | Fasting → depleted glycogen; stress hormones (cortisol, catecholamines, glucagon, GH) → catabolic state, hyperglycaemia, protein breakdown | The body shifts to catabolism; diabetics lose control; malnourished patients deteriorate |
| Intraoperative perturbances | Bleeding → hypovolaemia; haemodynamic instability from manipulation near great vessels; changes to respiratory mechanics (e.g. pneumoperitoneum, lateral positioning, one-lung ventilation) | These demand real-time compensation — the heart must increase output, lungs must maintain gas exchange |
| Post-operative demands | Wound healing (needs protein, calories, oxygen); pain (increases metabolic rate, tachycardia); potential infection | Recovery is metabolically expensive; if organs can't keep up, complications ensue |
"In general, the larger amount of tissue damage, the greater the metabolic response" [1]
| Factor | Example | Clinical Implication |
|---|---|---|
| Anatomical location | Heart and large blood vessels → gross haemodynamic disturbances; operations on the lung → impaired ventilation | Cardiac surgery has the highest perioperative risk; lung resection reduces respiratory reserve permanently |
| Type of tissues involved | Operations on infected tissue → post-operative sepsis | An abscess drainage has different risk than a clean hernia repair, even if the surgical wound size is similar |
| Extent of tissue damage | Laparoscopic cholecystectomy vs. open hepatectomy | MIS → less tissue trauma → less SIRS → faster recovery (this connects to ERAS / minimally invasive surgery lectures) |
First Principles
Think of fitness for surgery as a supply-demand equation. Surgery INCREASES demand (metabolic stress, wound healing, fighting infection). Anaesthesia may temporarily DECREASE supply (cardiac output ↓, ventilation ↓, drug metabolism altered). The patient must have enough reserve in their organs to bridge this gap. If their baseline organ function is already borderline, the perioperative period may tip them into organ failure.
The organ images in the lecture are best read as one connected reserve model rather than as isolated lists:
The operation determines the size of the insult; the patient’s cardiorespiratory, renal, hepatic, endocrine and haematological reserve determines how much of that insult can be absorbed. Pre-operative assessment looks for ways to reduce the insult, increase reserve, or provide more monitoring and postoperative support.
2. Anaesthesia — Both Ally and Threat
"Anaesthesia can actually alleviate stress — apart from several moments during induction and emergence (e.g. airway instrumentation)" [1]
This is an important nuance. General anaesthesia abolishes the pain response, blunts the neuroendocrine stress response (less catecholamine surge), and provides muscle relaxation for surgical access. Without anaesthesia, the stress of surgery would be far greater. However, the drugs used have their own physiological costs.
"Aspects of general anaesthetic can temporarily reduce the performance of different physiological functions. Depending on the patient's starting point for the relevant system, it could tip the patient over the edge into organ failure." [1]
This is the key concept: it's about the starting point. A patient with normal lungs can tolerate the respiratory depression of anaesthesia without issue. A patient with severe COPD (FEV1 30% predicted) may not be able to be weaned off the ventilator post-operatively.
"Best to get the patient into the best shape as possible — 'optimization'" [1]
3. How Anaesthesia Affects Each Organ System (and How Co-existing Disease Amplifies Risk)
Anaesthetic agents may adversely affect the respiratory system at every level: [1]
- Central control: ↓ response to CO₂ and hypoxia
- Airway: reduce protective reflexes; ↑ work of breathing (resistance from breathing circuit), retained secretions, bronchospasm
- Lung mechanics: ↓ lung volumes, ↑ work of breathing; residual paralysis
- Gas exchange: ↑ V/Q mismatch
Why each matters from first principles:
| Effect | Mechanism | Clinical Consequence |
|---|---|---|
| ↓ CO₂/hypoxia response | Opioids and many anaesthetic agents depress brainstem respiratory control → the ventilatory response to rising CO₂ or falling O₂ is blunted | Post-op hypoventilation, especially when respiratory disease, obesity, OSA, sedatives or residual neuromuscular block coexist. Avoid the misleading shortcut that COPD patients simply “rely on hypoxic drive” |
| Reduced protective reflexes | Laryngeal and cough reflexes suppressed → secretions and gastric contents not cleared | Aspiration risk, particularly during induction and emergence |
| ↓ Lung volumes | Supine position + abdominal contents pushing diaphragm cephalad + muscle relaxants → functional residual capacity (FRC) falls → small airways close → atelectasis | Atelectasis is a common mechanism contributing to postoperative hypoxaemia and pulmonary complications |
| ↑ V/Q mismatch | Atelectatic lung still perfused but not ventilated → shunt; paralysed diaphragm + position → ventilation redistributed | Hypoxaemia intra- and post-operatively |
| Residual paralysis | Incomplete reversal of neuromuscular blocking agents | Upper airway obstruction, aspiration, hypoventilation in recovery |
Pre-existing pulmonary diseases increase respiratory complications: [1]
- Intraoperative: coughing on induction, laryngospasm, bronchospasm, desaturation
- Post-operative: mucous retention pneumonia, respiratory failure
Anaesthetic drugs can affect cardiac performance through: [1]
- Vasodilation
- Venodilation
- Chronotropy (↓ heart rate)
- Inotropy (↓ contractility) → Potentially reduced cardiac output and tissue perfusion
Why this matters: Effects vary by drug, dose and physiological state, but propofol and volatile agents commonly reduce vascular tone and may depress contractility. A healthy circulation usually compensates; severe LV dysfunction or fixed outflow obstruction may not.
Surgical stress alters haemodynamics: [1]
- Increases metabolic demands (pain of surgery)
- Reduced tissue perfusion (reduced cardiac output ± reduced circulating volume from bleeding)
- May exacerbate myocardial ischaemia
Perioperative cardiac failure: [1]
- Inability of the heart to meet increased demand during surgery
- Increased metabolic demand
- May develop arrhythmias
- Fixed cardiac output states e.g. Aortic Stenosis
High Yield — Aortic Stenosis
Aortic stenosis is a "fixed cardiac output state" — the heart cannot increase output to meet demand because the valve obstruction limits flow. These patients are extremely high risk for perioperative hypotension and cardiac failure. They cannot compensate for the vasodilation caused by anaesthetic agents. This is a classic exam discriminator.
Hepatic Dysfunction in the perioperative period: [1]
- Reduced synthetic function → ↓ protein binding of drugs; impaired clotting
- Reduced metabolic function → ↓ drug metabolism and clearance; ↓ clearance of toxins → encephalopathy
- Circulatory disturbances → portal hypertension and ascites alter drug distribution
Why this matters from first principles:
- Many anaesthetic drugs are protein-bound (e.g. thiopental is ~85% albumin-bound). In hypoalbuminaemia, more free drug → exaggerated effect at lower doses → overdose risk.
- Coagulopathy (↓ clotting factors synthesized by liver) → bleeding risk during and after surgery.
- Altered volume of distribution (ascites = expanded extracellular fluid) → unpredictable drug pharmacokinetics. In advanced cirrhosis, total body sodium and water may be increased while splanchnic vasodilation leaves the effective arterial circulating volume low; “high circulating volume” is therefore an unsafe simplification.
- Hepatic encephalopathy can worsen post-operatively (from opioids, constipation, GI bleeding, infection).
Hepatic reserve assessment for hepatic resection (from supporting sources): Child-Pugh score, CT hepatic volumetry (≥30% FLR in normal liver, ≥40% in cirrhotic liver), ICG clearance (retention < 14% at 15 min for major hepatectomy) [5][6].
Renal dysfunction in the perioperative period: [1]
- Reduced drug excretion
- Electrolyte abnormalities
- Hypertension
- Severe anaemia
- Platelet dysfunction
Why this matters: Renally excreted drugs (e.g. morphine-6-glucuronide, certain antibiotics) accumulate → prolonged sedation, toxicity. Hyperkalaemia → arrhythmias under anaesthesia. Uraemic platelet dysfunction → bleeding. Anaemia → reduced oxygen-carrying capacity at a time when demand is increased.
Endocrine dysfunction in the perioperative period — Diabetes: [1]
- Associated CVS & renal problems
- Fasting and surgical stress upsets sugar control
- Diabetogenic hormones ↑ perioperatively (cortisol, glucagon, catecholamines, GH — all counter-regulatory to insulin)
- Both hyper and hypoglycaemia detrimental to CNS
Why fasting is particularly dangerous in diabetics: They take medications that lower blood sugar, but if they're fasting, there's no carbohydrate intake to balance the drug effect → hypoglycaemia. Conversely, the surgical stress hormones drive blood sugar up, and without their usual medications, they may become severely hyperglycaemic → hyperosmolar state, impaired wound healing, increased infection risk.
Anaesthesia and Co-Existing Diseases: [1]
- Diseased organs → adverse effects of anaesthetic drugs
- Systemic illness → altered pharmacokinetics and pharmacodynamics
- Drug interactions → between patient's medications and drugs administered
- Affects anaesthetic techniques → certain conditions contraindicate certain techniques
| Interaction | Example |
|---|---|
| Diseased organ → exaggerated drug effect | Cirrhotic liver → reduced metabolism of midazolam → prolonged sedation |
| Systemic illness → altered PK/PD | Renal failure → reduced clearance of morphine metabolites → respiratory depression |
| Drug interactions | Patient on MAO inhibitors → pethidine → serotonin syndrome (fatal) |
| Condition contraindicates technique | Patient on anticoagulants → neuraxial (spinal/epidural) anaesthesia contraindicated due to epidural haematoma risk |
Purpose of the pre-operative consultation: [1]
- Assessment of patient — Identification & optimization of co-morbidities
- Assessment of risk
- Plan anaesthetic & perioperative care → ? improvement in outcome
- Provide explanations & instructions to patients — what will happen? → Rapport & relieve anxiety
High Yield — Purposes of Pre-op Assessment
This is a commonly tested list. The four pillars are: (1) Assess the patient, (2) Stratify risk, (3) Plan the anaesthetic, (4) Counsel the patient. In exam answers, always mention optimization of reversible comorbidities — this is the actionable part that examiners reward.
Questions behind the questions: [1]
- What is the probability that the patient will survive the surgery?
- What is the probability that the patient will survive without complications?
- If complications occur, how bad will they be?
6. Pre-operative Assessment — The Elements
6.1 History
General history in the Preoperative Assessment: [1]
- Most parts could be performed by responsible medical officers
- Early identification can minimise delays or deferments to surgery
This means that as a junior doctor, YOU are expected to take the pre-op history. Don't wait for the anaesthetist to discover that the patient is on warfarin on the morning of surgery.
- Standard medical history: presenting complaint, HPC, PMH, drug history, allergy history, family history, social history (smoking, alcohol, occupation)
- Focus on systems that are most affected by surgery/anaesthesia: CVS, respiratory, hepatic, renal, endocrine
- Specifically ask about:
- Exercise tolerance (see METs below)
- Symptoms of undiagnosed cardiac/respiratory disease (chest pain, dyspnoea, orthopnoea, PND)
- Snoring, witnessed apnoeas, daytime somnolence and home CPAP/NIV use
- Frailty, falls, cognition/delirium risk, nutrition and ability to manage activities of daily living
- Bleeding or thrombosis history, recent infection, reflux/aspiration risk and pregnancy possibility where relevant
- Previous surgical/anaesthetic history
SHOULD ASCERTAIN A COMPLETE AND ACCURATE MEDICATION LIST OF ANY PATIENT SCHEDULED TO HAVE SURGERY!! [1]
This is in all-caps in the lecture for a reason. Medication errors around surgery are a major source of preventable harm.
Medication Lists: [1]
- Drugs that need to be stopped
- Drugs that should not be stopped (but may need different routes or suitable alternatives)
- Drugs that may need to be measured
- 'Recreational' drug use
- Oral contraceptives
Why oral contraceptives matter: Oestrogen-containing combined hormonal contraception increases VTE risk. For major elective surgery with likely prolonged immobilization, interruption may be considered well in advance, but this requires an individualized plan that also prevents unintended pregnancy; do not stop it reflexively for every procedure.
Why recreational drugs matter: Cocaine → recent use can cause perioperative hypertensive crisis, arrhythmias, coronary vasospasm. Chronic alcohol use → delirium tremens post-operatively, altered drug metabolism. Chronic opioid use → tolerance → higher analgesic requirements.
6.2 Medications That Must Be Stopped or Managed
Factors you need to alert your seniors or the anaesthesiologist: [1]
- Medications that need to be stopped or managed in consultation with specialists
- Implantable devices that need to be checked or functions altered
Anticoagulants: [1]
- "Traditional": e.g. Warfarin (approx. 3 to 4 days)
- "Novel" (NOACs): rivaroxaban (Xarelto), dabigatran (Pradaxa), apixaban (Eliquis), edoxaban (Lixiana)
Current-Practice Correction — Do Not Use One Stop Interval
The slide's “warfarin 3–4 days” is historical teaching, not a safe universal prescription. If warfarin interruption is required, current CHEST guidance uses an approximately 5-day interruption with an INR-based plan. For elective procedures, the usual CHEST starting point is 1–2 days off apixaban, rivaroxaban or edoxaban and 1–4 days off dabigatran; renal function, procedure bleeding risk, neuraxial/regional techniques and local protocols can require longer. Some minor procedures can proceed without interruption. [20]
| Question | What determines the plan? |
|---|---|
| Can the drug be continued? | Procedure/site bleeding risk, ability to secure haemostasis, and consequences of even a small bleed |
| If interrupted, for how long? | Drug/half-life, renal function (especially dabigatran), bleeding risk, and whether neuraxial anaesthesia is planned |
| Is bridging needed? | The indication and thromboembolic risk; bridging is not routine and CHEST recommends against it for AF and suggests against it for most interrupted VKA or DOAC pathways |
| When can it restart? | Adequate haemostasis and postoperative bleeding risk; the postoperative plan is as important as the stop date |
Antiplatelets: [1]
- ADP receptor inhibitors: Clopidogrel (Plavix)
Clopidogrel irreversibly inhibits the P2Y12 ADP receptor. If interruption is appropriate, many cardiac perioperative pathways use a 5-day interval, but recent PCI/stenting may make interruption dangerous. Confirm the indication, stent type/date, procedure urgency and bleeding risk with the perioperative/cardiology team rather than simply stopping it.
Aspirin is often continued for minor surgery but stopped for neurosurgery, spinal surgery, and operations with very high bleeding risk. The decision depends on balancing thrombotic vs. bleeding risk (often a cardiology/surgery joint decision).
Bridging Anticoagulation
Bridging means substituting a short-acting anticoagulant while a long-acting anticoagulant is interrupted. It increases bleeding and is not the default: current CHEST guidance recommends against bridging for AF, suggests against it for most mechanical-valve or VTE patients requiring VKA interruption, and suggests against bridging for DOAC interruption. A small group with exceptionally high thrombotic risk may still need an individualized specialist plan. [20]
Diabetic medications: [1]
- SGLT2 inhibitors ("...gliflozins"): Empagliflozin (Jardiance), Dapagliflozin (Farxiga)
- SHOULD BE STOPPED 48 hours before surgery
- Insulin: regimes will need to be modified depending on fasting requirements
Current-Practice Correction — SGLT2 Inhibitors
The lecture's 48-hour interval is outdated. Current ADA and 2024 AHA/ACC guidance recommends withholding SGLT2 inhibitors for 3–4 days before elective surgery: at least 3 days for canagliflozin, dapagliflozin and empagliflozin, and 4 days for ertugliflozin. In urgent surgery, proceed when needed but monitor for perioperative ketoacidosis, which may be euglycaemic. [19][22]
Why stop SGLT2 inhibitors? They cause euglycaemic diabetic ketoacidosis (euDKA) — a dangerous condition where the patient develops DKA with a normal or near-normal blood glucose. The mechanism: SGLT2 inhibitors cause glycosuria → lower blood glucose → lower insulin secretion → uninhibited lipolysis → ketogenesis. In the perioperative setting, fasting + surgical stress + SGLT2i = perfect storm for euDKA. Because the glucose is normal, it's easily missed. This is extremely high yield for exams.
Other diabetic medication adjustments (not explicitly in this lecture but commonly tested):
- Hold metformin and other oral glucose-lowering agents on the day of surgery under current ADA guidance; renal impairment, contrast and the local pathway may modify the plan. [22]
- Sulfonylureas are omitted on the day of surgery because fasting increases hypoglycaemia risk.
- Never omit basal insulin completely in type 1 diabetes. Continue an individualized reduced basal dose; use an IV insulin pathway when fasting is prolonged or control is unstable.
- GLP-1/GIP–GLP-1 receptor agonists now require an individualized aspiration-risk plan based on gastrointestinal symptoms, drug/dose phase, anaesthetic and procedure; a blanket “hold everyone” rule is no longer appropriate. [22]
| Drug Class | Action Before Surgery | Reason |
|---|---|---|
| ACE inhibitors / ARBs | Individualize | For selected patients taking them for hypertension before elevated-risk surgery, omission about 24 hours beforehand may limit hypotension; continuation is reasonable when used as HFrEF therapy. [19] |
| Beta-blockers | Continue | Abrupt withdrawal → rebound tachycardia, hypertension, may precipitate MI |
| Statins | Continue | Pleiotropic anti-inflammatory effects may be beneficial perioperatively |
| Corticosteroids (current/recent) | Continue; assess HPA-axis suppression and surgical stress | Stress-dose coverage is for known or possible adrenal insufficiency, not every patient who has ever received steroids. [23] |
| MAO inhibitors | Complex — discuss with anaesthetist | Interaction with pethidine (serotonin syndrome), indirect sympathomimetics |
| Oestrogen-containing contraception / HRT | Individualized plan for major surgery or prolonged immobility | Balance VTE risk, route/formulation, prophylaxis and unintended pregnancy or symptom recurrence |
| Lithium | Discuss early with anaesthesia/psychiatry; often withheld for major surgery | Narrow therapeutic index; renal excretion and toxicity are affected by fluid, sodium and renal changes; it can interact with neuromuscular blockers |
Devices: [1]
- Pacemakers and defibrillators → may require checking; certain functions may require disabling
- Prosthetic heart valves
- Deep brain stimulators
Why make an ICD/pacemaker plan? Monopolar electrosurgery can create electromagnetic interference that an ICD may misclassify as ventricular arrhythmia or that may inhibit pacing. The response is device- and procedure-specific: establish device type, indication, pacing dependence, last check, operative site and electrosurgery plan; decide whether programming or magnet application is required; provide external defibrillation/pacing capability when therapies are suspended; and ensure postoperative reactivation/checking. It is not correct to disable every device automatically. [19]
Prosthetic heart valves: Mechanical valves require lifelong vitamin-K-antagonist anticoagulation; many bioprosthetic-valve patients do not remain anticoagulated solely because of the valve. Interruption and bridging depend on valve type/location, other thrombotic risk factors and the procedure — do not assume every valve patient needs bridging. [20]
Anaesthetic History: [1]
- Any previous anaesthetic experiences
- Any known complications or difficulties:
- Difficult airway management
- Awareness (inadvertent recall of intraoperative events)
- Post-Operative Nausea and Vomiting (PONV)
- Delayed emergence from anaesthesia
- Genetic problems (rare): Pseudocholinesterase deficiency, Malignant Hyperthermia
- Nerve damage
| Complication | Why It Matters | What to Do |
|---|---|---|
| Difficult airway | If the patient has a known difficult airway, the anaesthetist must prepare alternative airway equipment, call for senior help, and potentially plan an awake fibreoptic intubation | Document clearly; alert anaesthetist early |
| Awareness | ~0.1–0.2% of GA patients have intraoperative recall; psychological trauma (PTSD) → use of BIS monitoring, appropriate anaesthetic depth | Previous awareness → anaesthetist will use additional monitoring |
| PONV | Some patients are highly susceptible (female, non-smoker, history of motion sickness, opioid use) → prophylactic antiemetics | Dexamethasone, ondansetron prophylaxis |
| Pseudocholinesterase deficiency | Suxamethonium normally hydrolyzed in < 5 min by pseudocholinesterase. Deficiency → prolonged paralysis (hours) → patient cannot breathe independently after surgery → needs ventilatory support [3] | Family history is important; prevalence ~1/2000 |
| Malignant Hyperthermia (MH) | Genetic defect in ryanodine receptor → uncontrolled intracellular Ca²⁺ release → muscle rigidity, massively ↑ metabolism, hyperthermia → fatal if untreated. Triggers: suxamethonium, all volatile agents EXCEPT nitrous oxide [3] | Family history; avoid triggers; have dantrolene available |
Ask about complications in biological relatives as well as in the patient: a person susceptible to malignant hyperthermia may previously have had an uneventful anaesthetic if triggering agents were not used or penetrance was incomplete. Also record allergies and the exact reaction, prior ICU admission, difficult IV access, dental injury, unexpected transfusion and prolonged postoperative ventilation.
Malignant Hyperthermia — Exam Classic
MH is triggered by suxamethonium and potent volatile inhalational anaesthetics; nitrous oxide is not a trigger. [1][3] Key early clues include an otherwise unexplained rise in ETCO₂, tachycardia, acidosis and rigidity; hyperthermia is often later. Stop triggering agents, hyperventilate with 100% oxygen, give dantrolene promptly, treat hyperkalaemia/acidosis and cool when hyperthermic. Always ask the patient and family history before GA. [27]
7. Physical Examination
Physical Examination: [1]
- Emphasize cardiorespiratory system
- Neurological examination when relevant:
- Those with history of CVA, neurological damage
- When contemplating regional anaesthesia
- Body parts relevant to the conduct of anaesthesia:
- Upper airway
- Spine
The airway exam is unique to pre-operative assessment and is critical. No single bedside sign reliably predicts difficulty, so combine history, examination, prior anaesthetic records and the planned rescue strategy.
Key components:
- Mallampati classification (I–IV): patient opens mouth and protrudes tongue; assess visibility of posterior pharyngeal structures. Class III–IV → potentially difficult intubation
- Thyromental distance ( < 6.5 cm suggests difficult laryngoscopy)
- Mouth opening ( < 3 finger-breadths is concerning)
- Neck mobility (limited extension → difficult alignment of oral, pharyngeal, and laryngeal axes)
- Dentition (loose teeth, prominent upper incisors → risk of dental damage)
- Obesity / short neck / receding mandible → predict difficulty
- CVS: Blood pressure, heart rate and rhythm, murmurs (especially aortic stenosis — fixed output state!), JVP, peripheral oedema, signs of heart failure
- Respiratory: Respiratory rate, oxygen saturation, auscultation for wheeze/crackles, chest wall movement, accessory muscle use
- Document baseline before regional anaesthesia (spinal/epidural) so that any new deficit post-operatively can be identified
- Document baseline before surgery near nerves (e.g. thyroidectomy → recurrent laryngeal nerve → vocal cord function) [4]
Investigations: [1]
- Should only be undertaken with purpose:
- Helps with or changes management
- Confirm diagnosis
- Assess severity
- Document baseline if it is expected to shift in the perioperative period
- "Routine" or "screening" investigations are NOT indicated for the most part
This is a paradigm shift from the old practice of ordering "routine pre-op bloods and CXR on everyone." Modern evidence shows that blanket screening does not improve outcomes and may cause harm (false positives → unnecessary further investigation → delay surgery → patient anxiety).
8.1 When Are Specific Investigations Indicated?
| Investigation | Indication (purpose-driven) |
|---|---|
| FBC | Expected blood loss; known anaemia; renal disease; haematological disease; major surgery |
| U&E (Renal function) | Renal disease; medications affecting electrolytes (diuretics, ACEi, digoxin); major surgery; DM |
| LFT | Known liver disease; alcohol use; jaundice |
| Coagulation (PT/APTT) | Anticoagulant therapy; liver disease; bleeding history; major surgery |
| Blood glucose | Diabetes; on steroids |
| Group & Save / Crossmatch | Expected blood loss; transfusion anticipated |
| ECG | Established cardiovascular disease or relevant symptoms; selected higher-risk patients/procedures. Age alone is not a universal trigger |
| CXR | Acute cardiorespiratory symptoms; known unstable cardiorespiratory disease; NOT for age or smoking alone in absence of symptoms [10] |
| Pulmonary function tests | Known respiratory disease being optimized; lung resection surgery (see ppoFEV1 below) |
| Echocardiography | Suspected valvular disease, heart failure, to assess LV function before major surgery |
| Stress testing / CCTA | Only in selected elevated-risk patients with poor/unknown functional capacity when the result would change management; not simply because METs are < 4 |
| CPET | Objective integrated cardiorespiratory assessment when it will refine risk or perioperative planning for selected major surgery |
CXR Is NOT Routine Pre-op
A past paper question asks which pre-operative patient should have a CXR indicated — the answer is the patient with acute heart failure, NOT "an old man undergoing cholecystectomy" or "a smoker" without acute symptoms. [10] "Routine" CXR for age or smoking history alone is not evidence-based.
NICE NG45 makes the practical point explicit: test selection depends on the grade of surgery, ASA physical status, comorbidities, medicines and whether a result is already available, rather than on a universal “pre-op panel.” It also recommends sensitively asking anyone of childbearing potential about pregnancy possibility and discussing testing when relevant. [24]
9. Risk Stratification
American Society of Anesthesiologists (ASA) Classification System — in use for over 60 years. Used to assess and communicate a patient's pre-anesthesia medical co-morbidities. When used with other factors (e.g. type of surgery, frailty, level of deconditioning), it can be helpful in predicting perioperative risks. [1]
| ASA Class | Definition | Examples |
|---|---|---|
| I | A normal healthy patient | Healthy, non-smoker, no or minimal alcohol |
| II | A patient with mild systemic disease | Well-controlled DM, mild asthma, social drinker, BMI 30–40, current smoker |
| III | A patient with severe systemic disease | Poorly controlled DM, COPD, morbid obesity (BMI ≥ 40), stable angina, moderate-severe renal impairment, pacemaker |
| IV | A patient with severe systemic disease that is a constant threat to life | Recent MI ( < 3 months), ongoing cardiac ischaemia, severe valve dysfunction, sepsis, DIC, ESRD not on regular dialysis |
| V | A moribund patient who is not expected to survive without the operation | Ruptured AAA, massive trauma, intracranial haemorrhage with mass effect |
| VI | A declared brain-dead patient whose organs are being removed for donor purposes | Organ donor |
| E suffix | Emergency: delaying treatment would significantly increase the threat to life or a body part | Added to I–V when the definition is met (e.g. ASA IIIE); there is no ASA VIE |
Current-Practice Correction — ASA Wording
The slide reproduces older wording: ASA III “not incapacitating,” ASA IV “incapacitating,” and ASA V “not expected to survive 24 hours with or without surgery.” The current ASA definitions above omit those qualifiers, define ASA V as not expected to survive without the operation, and include ASA VI. Final assignment is a clinical decision made by the anaesthesiologist on the day of anaesthesia care. [21]
High Yield — ASA Classification
Memorize this table. It appears in MCQs and SAQs. Key points: ASA is about comorbidities, not about the surgery. ASA alone does not determine fitness — it must be combined with surgical risk, functional capacity, and frailty assessment.
Metabolic equivalents (METs) are multiples of the basal metabolic rate, assumed to be 3.5 mL·kg⁻¹·min⁻¹. [1]
The lecture cites a 2001 study in which inability to climb 2 flights of stairs had a positive predictive value of 82% for postoperative pulmonary/cardiac complications or death within 30 days; it equates 2 flights with > 4 METs. [1]
| METs | Activity Examples | Clinical Significance |
|---|---|---|
| 1 | Eating, getting dressed, working at a desk | Baseline metabolic rate |
| 2 | Showering, walking down eight steps | |
| 3 | Walking on a flat surface for one or two blocks | Below the threshold for most surgery |
| 4 | Raking leaves, weeding, pushing a power mower, walking up 2 flights of stairs | Traditional threshold separating poor from acceptable functional capacity |
| 5 | Walking 4 mph, social dancing, washing a car | |
| 6 | Nine holes of golf carrying clubs, heavy carpentry, using a push mower | |
| 7 | Digging / spading soil, singles tennis, carrying 60 lb | Good reserve |
| 8 | Moving heavy furniture, jogging slowly, rapidly climbing stairs, carrying 20 lb upstairs | |
| 9 | Bicycling at a moderate pace, sawing wood, slow jumping rope | |
| 10 | Brisk swimming, bicycling uphill, walking briskly uphill, jogging 6 mph | Excellent reserve |
| 11 | Cross-country skiing, full-court basketball | |
| 12 | Running continuously at 8 mph |
The activity table is a useful visual memory aid, not a calibrated exercise test: pace, symptoms, terrain, musculoskeletal limitation and how recently the activity was performed all matter.
Current approach: Poor functional capacity is still commonly defined as < 4 METs, but the 2024 AHA/ACC algorithm also accepts a structured Duke Activity Status Index (DASI) score ≤34. A low-risk patient generally proceeds without further cardiac testing. In an elevated-risk patient with poor or unknown capacity, biomarkers and selective stress imaging/CCTA are considered only if the result would alter the decision or perioperative plan. [19]
Lecture Fact vs Current Practice
For a lecture-recall question, recognize the 2 flights / 4 METs association and the historical 82% PPV quoted on the slide. For clinical reasoning, do not turn it into “≥4 METs = fit for GA” or “< 4 METs = stress test/revascularize.” Combine structured capacity, calculated risk, procedure risk and whether testing can change management. [19]
ASA class and METs are descriptors, not complete perioperative risk estimates. Current NICE and AHA/ACC guidance recommends a validated tool appropriate to the outcome and population. [19][25]
| Tool | What it contributes | Limitation |
|---|---|---|
| RCRI | Simple estimate of perioperative cardiac risk using six clinical/surgical predictors | Cardiac outcomes only; discrimination varies by operation and population |
| ACS NSQIP Surgical Risk Calculator | Procedure-specific estimates for multiple 30-day outcomes | Requires detailed inputs; calibration depends on the underlying dataset |
| SORT / locally validated calculator | Mortality estimate using patient and operation variables | Availability and local validation vary |
Use the number to support shared decision-making, monitoring and disposition—not as an automatic “operate/do not operate” cutoff.
While the lecture focuses on patient factors, the type of surgery is equally important. Surgical risk is typically classified as:
| Risk Category | Examples | Estimated 30-day Cardiac Risk |
|---|---|---|
| Low risk | Endoscopy, superficial procedures, cataract, breast surgery | < 1% |
| Intermediate risk | Abdominal surgery, carotid endarterectomy, hip/knee replacement, head and neck surgery | 1–5% |
| High risk | Aortic and major vascular surgery, prolonged surgery with large fluid shifts/blood loss | > 5% |
"Risk assessment, NOT a prediction or guarantee" [1]
"…best estimate, based on available information, of the likelihood that the patient will be able to supply sufficient oxygen and nutrients to tissues in the perioperative period…" [1]
"Informs patient's decision making and perioperative management" [1]
"Should be made as a team between surgeons, anaesthesiologists and relevant specialists" [1]
Add the patient to that team. The estimate should be discussed in terms the patient can use: likely benefit, absolute risks where available, uncertainty, alternatives (including no surgery), what optimization can change, and the anticipated postoperative level of care.
10. Optimization of Comorbidities
Optimize patient as far as possible for elective patients. For emergency surgery… do the best you can with increased monitoring and post-operative care. [1]
This is a crucial distinction. Elective surgery gives you the luxury of time to optimize. Emergency surgery does not — but you still do what you can (even if it's 30 minutes of fluid resuscitation and antibiotics before a laparotomy for perforated viscus).
Indications for consulting other specialists: [1]
- Diagnosis and determining severity — "Is the chest pain of cardiac cause?"
- Optimization of the condition — "Are there reversible elements in the patient with COPD?"
- Management of the condition in the perioperative period — "Does the patient require bridging anticoagulation?"
Lung function should be optimized before general anaesthesia for elective surgery: [1]
- Stop smoking
- Treat infections
- Bronchodilators; steroids
Post-op care to reduce complications: [1]
- Supplemental oxygen
- Adequate pain relief (pain → splinting → poor ventilation → atelectasis → pneumonia)
- Post-op physiotherapy: pre-op patient education (teach incentive spirometry, deep breathing exercises BEFORE surgery so the patient knows what to do after)
- Consider post-op ventilator support (for very high-risk patients, plan elective ICU admission)
Supplemental oxygen should be prescribed and titrated to a target saturation, not given automatically without reassessment; some patients at risk of hypercapnic respiratory failure need a lower target. Pair good analgesia with early mobilization, upright positioning, secretion clearance and appropriate CPAP/NIV planning. “Physiotherapy” or incentive spirometry is not a substitute for this bundle.
Smoking cessation: Encourage cessation at any time—do not advise continued smoking because surgery is close. Longer abstinence generally gives more pulmonary and wound benefit, while even brief abstinence lowers carboxyhaemoglobin and removes ongoing smoke exposure.
Cardiovascular diseases: [1]
- Delineate cardiac risk
- Judicious investigations
- Optimize cardiac status: lifestyle changes, medications, valvular surgery, (revascularization)
- Appropriate post-op monitoring
- Effective post-operative pain relief
Key principles:
- Control hypertension (but don't delay surgery for mild-moderate HTN; severe HTN [SBP > 180 or DBP > 110] should be controlled)
- Optimize heart failure (diuretics, ACEi, beta-blockers)
- Continue beta-blockers and statins perioperatively
- For severe aortic stenosis → consider valve replacement/TAVI before elective non-cardiac surgery
- Revascularization is not a routine way to “make the patient fit.” The 2024 AHA/ACC guideline recommends it for ACS before elective non-cardiac surgery and considers it reasonable for haemodynamically significant left-main disease; routine revascularization for non-left-main CAD solely to reduce perioperative events is not recommended. [19]
Liver: [1]
- Treat coagulopathy
- Other supportive treatment
- Nutrition (many liver patients are malnourished → pre-op nutritional support)
- Adjust drug doses
Cirrhosis — Do Not Chase the INR
The slide's “treat coagulopathy” means identify and treat a clinically relevant bleeding problem or correctable deficiency; it does not mean routinely normalizing an elevated INR with plasma before surgery. Cirrhosis produces a fragile rebalanced haemostatic state, conventional INR does not capture the whole bleeding/thrombosis balance, and volume-heavy plasma can worsen portal pressure. Use the procedure, bleeding history, platelets/fibrinogen and local hepatology/haematology or viscoelastic-testing pathways to guide targeted treatment. [26]
Renal: [1]
- Consider prehydration (to protect against contrast nephropathy and perioperative AKI)
- Minimise nephrotoxins (NSAIDs, aminoglycosides, contrast dye — if needed, use with hydration)
Aim for euvolaemia and adequate perfusion, not indiscriminate “prehydration”: both hypovolaemia and fluid overload can cause harm. Check potassium/acid–base status when indicated, establish the dialysis schedule and access plan, adjust renally cleared drugs, avoid unnecessary nephrotoxins and monitor postoperative renal function in at-risk patients.
Diabetes: [1]
- Clear fasting instructions & treatment plan
- The slide says to omit oral hypoglycaemic drugs on the morning of surgery
- May require an insulin dextrose infusion (VRII / "sliding scale")
- Meticulous perioperative sugar control
- Frequent monitoring
Current framework: plan each drug rather than applying one rule. Hold SGLT2 inhibitors 3–4 days in advance; hold metformin and other oral agents on the day under the current ADA pathway; never omit all basal insulin in type 1 diabetes; individualize GLP-1/GIP–GLP-1 therapy; and monitor glucose at least every 2–4 hours while nil by mouth. The ADA 2026 perioperative target is 5.6–10.0 mmol/L (100–180 mg/dL) for most patients, individualized for procedure and hypoglycaemia risk. [22]
- Nutritional optimization (GC 185): Malnourished patients (albumin < 30, BMI < 18.5, unintentional weight loss > 10%) should receive pre-operative nutritional support (oral supplements, enteral feeding, or TPN if gut non-functional) for at least 7–14 days if surgery can be delayed [11]
- Anaemia correction (GC 155): Consider iron supplementation, EPO, or pre-operative transfusion if Hb critically low; patient blood management strategies to minimize need for transfusion [12]
- Frailty assessment (Frailty in Older Adults): Frailty is an independent predictor of post-operative complications, prolonged length of stay, and mortality — increasingly recognized as more important than age alone [13]
- Pre-operative vaccination: For splenectomy patients — pneumococcal, Haemophilus influenzae type B, meningococcal, and influenza vaccines, ideally 2 weeks before elective splenectomy [14]
Anaesthetic Plan: [1]
- Type of anaesthesia: General vs Regional or Combination
- Airway management
- Preparation: patient, staff, equipment and drugs & fluids
- Intraoperative management: Monitoring, positioning, fluid management
- Post-operative management: Analgesia, Disposition
| Component | Details |
|---|---|
| Type | GA (inhalational or TIVA); Regional (spinal, epidural, nerve block); Combination; Local + sedation |
| Airway | Facemask, LMA (supraglottic), endotracheal tube (ETT); plan for difficult airway |
| Preparation | Fasting status confirmed; IV access; consent; equipment check (AAGBI checklist); drugs drawn up; blood available if needed |
| Monitoring | Standard: ECG, SpO₂, NIBP, capnography, temperature. Extended: arterial line, CVP, cardiac output, BIS |
| Positioning | Supine, lateral, prone, lithotomy — each has specific risks (nerve injury, pressure sores, airway access) |
| Fluids | Maintenance, replacement, resuscitation — guided by clinical assessment and monitoring |
| Analgesia | Multimodal: paracetamol, NSAIDs (if no contraindication), opioids, regional techniques, local infiltration |
| Disposition | Recovery room → ward vs. HDU vs. ICU — determined by patient risk and surgery type |
From supporting lecture material [15], the decision to operate depends on three factors:
| Factor | Key Questions |
|---|---|
| Disease factor | Staging? Operable? Life-saving vs. functional vs. QOL surgery? Can it be managed conservatively? |
| Patient factor | Fit enough? Parameters that can be optimized? Does the patient want surgery? Social support? |
| Surgeon factor | Expertise available? |
Assessing fitness for surgery: [1] "Should be made as a team between surgeons, anaesthesiologists and relevant specialists"
Anaesthesiologists can then determine: [1]
- Estimate whether there is sufficient reserve for surgery:
- Meet increased metabolic demands from the stress of surgery and for healing
- As there may also be some compromise in cardiorespiratory function from anaesthesia
- Estimate the risk of exacerbating certain comorbidities:
- Ischaemic heart disease
- Respiratory failure
14. Exam Intelligence
| Paper | Question Type | Topic |
|---|---|---|
| 2021 Minicase Q10 [8] | SAQ | "State pre-operative management of this patient" (cholecystitis case) |
| 2019 Minicase Q10 [7] | SAQ | "Name two pre-operative management approaches and justify with reason" |
| 2022 Minicase Section 4 [9] | SAQ | Post-thyroidectomy complications (requires pre-op assessment knowledge: vocal cord function, calcium baseline) |
| 2020 MCQ Q70 [16] | MCQ | AAA management — involves assessment of fitness (age, comorbidities, functional status) |
| 2025 MCQ Q59 [17] | MCQ | Remifentanil would NOT be useful for post-op pain (ultra-short acting, offset too fast — connects to anaesthetic planning) |
| Trap | Correct Approach |
|---|---|
| "Routine pre-op investigations for everyone" | Investigations should be purpose-driven, not routine |
| Confusing ASA with surgical risk | ASA describes PATIENT comorbidities only; combine with surgical risk for overall assessment |
| Using older ASA III–V wording | Current ASA: III = severe systemic disease; IV = severe disease that is a constant threat to life; V = not expected to survive without the operation; include VI |
| Using the slide's old SGLT2 interval | Current guidance: stop 3–4 days before elective surgery; watch for euglycaemic DKA |
| Treating < 4 METs as an automatic stress-test indication | First calculate risk; test only selected elevated-risk patients when the result will change management |
| Revascularizing solely to “clear” surgery | Treat coronary disease for the same indications as outside the perioperative setting; routine non-left-main revascularization does not reduce perioperative events |
| Stopping beta-blockers pre-op | Continue — withdrawal is dangerous |
| Ordering CXR for "old age" or "smoking" | Only indicated for acute/unstable cardiorespiratory disease |
| Ignoring airway assessment | A "can't intubate, can't oxygenate" scenario is the most feared anaesthetic emergency |
| Not mentioning optimization in pre-op SAQ answers | Always state what you would optimize (e.g., "stop smoking, treat chest infection, optimize bronchodilators") |
"Pre-operative management" SAQ template:
- Assess — full history and examination including comorbidities, medications, functional capacity, airway
- Investigate — guided by clinical findings (blood tests, ECG, imaging as indicated)
- Optimize — make an individualized medication plan (antithrombotics, SGLT2i, other diabetes drugs, insulin), treat reversible conditions (infection, bronchospasm, anaemia, dehydration), and support nutrition/prehabilitation when appropriate
- Risk stratify — ASA class, structured functional capacity (DASI/METs), a validated calculator, surgery risk and frailty/risk modifiers
- Plan — anaesthetic plan (GA vs regional), monitoring level, post-op disposition (ward/HDU/ICU)
- Consent and counsel — explain procedure, risks, what to expect, fasting instructions
- Specific measures — e.g., for thyroidectomy: document vocal cord function, pre-op calcium; for splenectomy: vaccinations; for diabetic: insulin-dextrose infusion plan
High Yield Summary
- Core question: can the patient’s reserve meet the extra demand of surgery despite temporary reductions in cardiorespiratory performance from anaesthesia?
- Assess: comorbidities, full medication/device list, prior anaesthetic/family history, airway, cardiorespiratory examination, frailty and structured functional capacity.
- Investigate with purpose: a test should confirm/severity-stage disease, change management or establish a needed baseline; avoid a universal “pre-op panel.”
- Estimate risk: ASA I–VI (+E), DASI/METs, a validated calculator, procedure risk and risk modifiers. Risk is an estimate, not a certificate of “fitness.”
- Optimize and plan: treat reversible disease, make individualized antithrombotic/diabetes plans, plan anaesthesia, monitoring, analgesia and ward/HDU/ICU disposition.
- Current corrections: SGLT2 inhibitors 3–4 days; interrupted warfarin usually about 5 days with INR planning; bridging is not routine; poor capacity alone does not mandate stress testing; prophylactic coronary revascularization is not routine.
- Communicate: involve the patient in a team discussion of benefit, absolute risk where possible, uncertainty and alternatives.
Active Recall - Pre-operative Assessment
[1] Lecture slides: GC 002 - Is he fit for surgery - Pre-operative assessment.pdf (all pages) [2] Senior notes: Gen Clerk Anaes + Microbiology Summary.pdf (p2–3) [3] Senior notes: Maksim Surgery Notes.pdf (p285, perioperative issues section) [4] Senior notes: Ryan Ho Endocrine.pdf (p22, pre-op preparation for thyroidectomy) [5] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p489, hepatic resection perioperative assessment) [6] Senior notes: Ryan Ho GI.pdf (p267, pre-operative assessment of operability for liver) [7] Past papers: 2019 Fourth Summative Mini Case.pdf (p13, Case 2 Q10) [8] Past papers: 2021 Fourth Summative Minicase.pdf (p19, Case 2 Q10) [9] Past papers: 2022 Fourth Summative Minicase.pdf (p10–12, Case 2 Section 3–4) [10] Senior notes: Ryan Ho Radiology.pdf (p8, pre-operative CXR question) [11] Lecture slides: GC 185. Feed him up before surgery Surgical nutrition, Enteral and parenteral feeding.pdf [12] Lecture slides: GC 155. Is blood transfusion absolutely required in patient management nowadays.pdf [13] Frailty in Older Adults - Kim DH 2024 (NEJM).pdf [14] Senior notes: Block A - Splenomegaly_ common causes of splenomegaly; myeloproliferative diseases.pdf (p20) [15] Lecture slides: 2022 07 29 Surgery Surgical Principles (Dr IYH Wong).pdf (p26) [16] Past papers: 2020 Fourth Summative Assessment MCQ paper.pdf (p27, Q70) [17] Past papers: 2025 Fourth Summative MCQ.pdf (p23, Q59) [19] 2024 AHA/ACC Guideline for Perioperative Cardiovascular Management for Noncardiac Surgery (guideline hub and official slide set) [20] Douketis JD, Spyropoulos AC, et al. Perioperative Management of Antithrombotic Therapy: CHEST Clinical Practice Guideline. Chest. 2022;162:e207–e243. [21] American Society of Anesthesiologists. Statement on ASA Physical Status Classification System (current definitions; last amended 2020). [22] American Diabetes Association Professional Practice Committee. Diabetes Care in the Hospital: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S339–S355. [23] European Society of Endocrinology and Endocrine Society. Diagnosis and Therapy of Glucocorticoid-Induced Adrenal Insufficiency. 2024. [24] NICE. Routine preoperative tests for elective surgery (NG45). 2016, current online guidance. [25] NICE. Quality statement 2: Assessment of perioperative risk (QS216). 2026. [26] American Association for the Study of Liver Diseases. Peri-Procedural Management of Bleeding Risk in Cirrhosis. 2024. [27] Malignant Hyperthermia Association of the United States. Emergency Treatment for an Acute MH Event.
GC001 How Would You Anaesthetise Me - Pharmacology Of Anaesthetic Drugs
The pharmacology of anaesthetic drugs encompasses the mechanisms of action, pharmacokinetics, and pharmacodynamics of intravenous induction agents, inhalational anaesthetics, neuromuscular blocking agents, opioids, and local anaesthetics used to achieve the triad of unconsciousness, analgesia, and muscle relaxation during general anaesthesia.
GC004 The Pain Is Intolerable - Pain Control
Pain control is the systematic assessment and management of acute or chronic pain using pharmacological, interventional, and non-pharmacological strategies to reduce suffering and restore function.