Chapter 1
Preoperative Management

Safe anaesthesia requires meticulous preoperative assessment. Elective patients go through a dedicated preoperative assessment clinic run by a multidisciplinary team (nurses, doctors, pharmacists, technicians). Emergency patients must still undergo rigorous systematic review.

What happens at the clinic:

• Full medical history — concurrent diseases, previous anaesthetics, family history of anaesthetic problems
• Review of notes, previous admissions, current medications and investigation results
• History of reflux, smoking, alcohol and recreational drugs
• Complete medication list including dosages, recent changes and allergic reactions
• Focused examination of the cardiorespiratory system — detect new murmurs, ensure BP controlled
• Cervical spine assessment in patients with limited neck movement
• Dentition check — loose teeth, dentures, crowns, orthodontic appliances
• Airway assessment — done at the anaesthetist's preoperative visit

Functional capacity describes what a patient can physically do and reflects their functional reserve. It is especially important in patients with cardiac disease.

MET = Metabolic Equivalent of Task — 1 MET = 3.5 mL O₂/kg/min (resting oxygen consumption)

The Duke Activity Status Index provides a more detailed scoring system. Be careful — function may be limited by arthritis or neurological disease rather than cardiac disease. Look for specific cardiac symptoms: orthopnoea, paroxysmal nocturnal dyspnoea.

CPEX (Cardiopulmonary Exercise Testing): Identifies patients at high risk via anaerobic threshold (AT). AT <11 mL/kg/min → higher mortality (18%) after major surgery. AT <11 + IHD → very high mortality (42%).

Failure to achieve adequate oxygenation/ventilation is responsible for significant anaesthesia-related morbidity and mortality. Difficult intubation occurs in approximately 1 in 65 intubations. Despite careful assessment, 20% of difficult intubations are NOT predicted.

Factors associated with difficult MASK VENTILATION:

• Obesity
• Beard
• Edentulous (no teeth)
• Snoring history
• Age >55 years

Cormack & Lehane Grading (laryngoscopy view):

Modified Mallampati Classification (patient sits, mouth open, tongue protruded):

• Class 1: Faucial pillars, soft palate AND uvula visible
• Class 2: Faucial pillars and soft palate visible; uvula masked by tongue
• Class 3: Only soft palate visible
• Class 4: Soft palate NOT visible

Wilson Risk Factors (each scored 0–2, maximum 10 points):

• Obesity
• Restricted head and neck movement
• Restricted jaw movement
• Receding mandible
• Buck teeth (prominent incisors)

Score >2 predicts 75% of difficult intubations (but high false-positive rate).

Key distances to remember:

The ASA (American Society of Anesthesiologists) classification describes the preoperative physical state of a patient. Developed by Saklad in 1941. Used routinely for every patient in the UK. Does NOT account for age, smoking, obesity or pregnancy. Postscript 'E' indicates emergency surgery.

Starvation before surgery minimises gastric contents and reduces aspiration risk. Aspiration of solid food → asphyxiation. Aspiration of gastric acid → Mendelson's syndrome (pneumonitis).

• Milky drinks have high fat content → increased gastric transit time → not allowed at 2h
• Chewing gum significantly increases gastric fluid volume — NO gum on day of surgery
• Emergency surgery → treat as FULL STOMACH regardless of fasting

With more day surgery and late admissions, premedication is now less common. Main indication remains anxiety.

Purposes of premedication:

• Anxiolysis
• Smoother induction of anaesthesia
• Reduced IV induction agent requirement
• Possibly reduced risk of awareness

Types and indications:

• Benzodiazepine (e.g. midazolam) ± metoclopramide → anxiety
• H₂ antagonist (evening before + morning) + sodium citrate (immediately before induction) → aspiration prophylaxis in reflux patients
• EMLA cream (topical LA) over venous sites → children
• Anticholinergics (atropine, glycopyrrolate) → dry secretions, prevent bradycardia (e.g. squint surgery)
• IM opioids → now rarely prescribed as premedication

Hypertension occurs in 15% of the UK population. 97% is essential/primary. Stage 3 hypertension (≥180/110) associated with target organ damage.

• Blood pressure below 160/90 required for booking elective surgery (Hartle 2016)
• In preop clinic: BP below 180/110 acceptable
• Hypertension → exaggerated BP drop on induction due to ↓CO (↓HR + ↓SV)
• Antihypertensives should be CONTINUED on day of surgery
• β-Blockers: if stopped → ↑arrhythmias, ↑ischaemia perioperatively
• ACE inhibitors → risk of hypotension and hyperkalaemia

Ischaemic Heart Disease (IHD) — 12–20% of surgical patients have preoperative evidence of myocardial disease.

• Perioperative MI mortality: up to 70%
• Risk of perioperative MI with no prior MI history: 0.1–0.2%
• Risk of reinfarction with prior MI: 6–7% overall
• Unstable angina → cancel elective surgery, investigate and consider cardiac intervention

ACC/AHA Clinical Predictors of Perioperative Cardiac Risk:

Surgery-Specific Cardiac Risk:

URTI: Causes increased bronchial reactivity for 3–4 weeks after resolution. Unless surgery is urgent, postpone for 4 weeks.

Asthma (affects 10–20% of population):

• Atopic (early-onset, extrinsic) → allergen → IgE → Type 1 hypersensitivity
• Non-atopic (late-onset, intrinsic)
• Continue usual bronchodilators preoperatively; give inhaled β₂-agonist before theatre
• Sedatives CONTRAINDICATED during acute exacerbation
• Regular steroids → adrenocortical suppression → may need perioperative hydrocortisone
• Postpone elective surgery if recent exacerbation (may take weeks to normalise)

COPD (Chronic Obstructive Pulmonary Disease):

• Chronic bronchitis: daily productive cough for ≥3 months/year for ≥2 consecutive years
• "Blue bloaters" — chronic hypercapnia → lost CO₂ drive → hypoxic drive only → extremely difficult to wean post-op
• "Pink puffers" (emphysema) — exertional dyspnoea only, hyperinflated chest
• ABG indicated if severe dyspnoea on moderate exertion
• Postpone if green sputum (chest infection) — antibiotics + physiotherapy first

Pulmonary Function Tests:

Fluid assessment: Postural hypotension, tachycardia, hypotension → volume depletion. Raised JVP, peripheral oedema → overload. Oliguria = urine output <0.5 mL/kg/hour.

Maintenance fluid requirements: 40 mL/kg/day in adults.

Hyperkalaemia treatment:

• 10 mL of 10% calcium gluconate IV → immediately (temporarily) improves cardiac automaticity
• Insulin 20 units in 100 mL of 20% dextrose over 30–60 min → shifts K⁺ into cells
• Calcium resonium → slower, over several days

Diabetes mellitus is listed as an intermediate clinical predictor of perioperative cardiac risk (especially insulin-dependent). Blood glucose should be maintained between 6–10 mmol/L perioperatively.

• Fasting blood glucose >11.1 mmol/L indicates poor control
• HbA1c reflects glucose control over preceding 2–3 months
• Type 1 (IDDM): always requires insulin — never omit
• Type 2: oral hypoglycaemics may need adjustment; metformin may need to be held in certain cases (contrast, renal impairment)
• Autonomic neuropathy → silent MI, delayed gastric emptying (aspiration risk)
• Renal disease: check creatinine, eGFR
• Associated: cardiovascular disease, peripheral vascular disease, renal disease, retinopathy

A heavy smoker = ≥20 cigarettes/day. Up to 15% of haemoglobin in smokers combines with CO to form carboxyhaemoglobin, reducing O₂-carrying capacity.

Perioperative problems from smoking:

• Increased airway reactivity and bronchospasm
• Increased sputum production and retention
• Coughing and atelectasis → increased post-op chest infection risk
• Associated IHD and COPD

Benefits of stopping smoking:

• 12–24 hours: CO and nicotine effects significantly reduced
• 6–8 weeks: ciliary and immunological activity restored