Chronic Smoker for Emergency Strangulated Inguinal Hernia - Anaesthetic Implications & Management

PART A: ANAESTHETIC IMPLICATIONS OF CHRONIC SMOKING

1. Respiratory System

"Smoking increases airway irritability, decreases mucociliary transport, decreases FVC and FEF25% to 75%, and increases secretions, thereby increasing the incidence of postoperative pulmonary complications." - Barash's Clinical Anesthesia, 9e

2. Cardiovascular System

• Nicotine stimulates both sympathetic and parasympathetic ganglia via nicotinic receptors - net effect is sympathomimetic: tachycardia, hypertension, increased myocardial O2 demand
• Endothelial dysfunction and accelerated atherosclerosis
• Platelet adhesion and hypercoagulability - increased risk of perioperative MI (OR 1.77) and CVA (OR 1.55)
• Coronary artery disease - may be occult in young smokers
• Increased risk of perioperative arrhythmias

3. COHb and Oxygen Delivery - The Key Acute Implication

• COHb shifts the oxyhaemoglobin dissociation curve to the LEFT (Haldane effect) - impairing O2 unloading at tissues
• Heavy smokers may have COHb 10-15% at time of surgery
• Pulse oximetry cannot distinguish COHb from oxyHb - reads falsely high
• Even 48 hours of abstinence can significantly reduce COHb and begin restoring mucociliary function - but in an emergency, this is not possible

4. Pharmacological Implications

• Increased MAC for volatile anaesthetic agents (by ~10-15%) due to enzyme induction and altered receptor sensitivity
• CYP1A2 induction by polycyclic aromatic hydrocarbons in smoke - accelerated metabolism of many drugs
• Opioid resistance/tolerance - smokers often have higher pain scores and require more opioids postoperatively
• Nicotine-induced ADH secretion - risk of hyponatremia; avoid rapid IV fluid correction
• Altered pharmacokinetics of propofol, midazolam, theophylline, and other hepatically metabolised drugs

5. Wound Healing and Infection

• Reduced tissue oxygenation (COHb + vasoconstriction) impairs wound healing
• Increased risk of wound dehiscence (OR 2.07), hernia recurrence, necrosis (OR 3.6), surgical site infection (OR 1.18)
• These are particularly relevant in hernia repair

PART B: ANAESTHETIC MANAGEMENT - STRANGULATED INGUINAL HERNIA IN A CHRONIC SMOKER

Pre-Anaesthetic Assessment (Rapid - Emergency Setting)

• Pack-year history, presence of COPD/chronic bronchitis symptoms, dyspnoea on exertion
• Time of last meal (assume full stomach until proven otherwise)
• Duration of hernia strangulation (ischaemia time, bowel viability)
• Comorbidities: IHD, hypertension, COPD, diabetes

• Airway assessment (Mallampati, mouth opening, TMD, neck mobility)
• Signs of sepsis / peritonitis: fever, tachycardia, hypotension, abdominal rigidity
• Hydration status, signs of bowel obstruction

• ABG - to directly measure PaO2, PaCO2, and COHb (pulse oximetry is unreliable)
• ECG, CXR
• FBC, BMP/RFT, LFT, serum lactate (bowel ischaemia marker)
• Coagulation profile
• Crossmatch blood
• Spirometry if feasible (rarely practical in emergency)

• IV access - two large-bore cannulas
• IV fluids for resuscitation (Hartmann's or normal saline)
• Correct electrolyte imbalances (especially hypokalaemia from vomiting)
• Nasogastric tube - consider to decompress stomach (though doesn't eliminate aspiration risk)
• Pre-oxygenate with 100% O2 for minimum 3-5 minutes (longer in smokers to denitrogenate and flush CO)
• Pre-medicate: H2 blocker or PPI (ranitidine/omeprazole IV) + metoclopramide to reduce gastric acidity and volume
• Sodium citrate 0.3M 30mL oral (if time permits) - neutralise gastric acid
• Bronchodilator if wheeze present: nebulised salbutamol

Choice of Anaesthesia

• Uncertain duration (bowel resection may be needed)
• Peritonitis/sepsis may contraindicate spinal (hypotension in already compromised patient)
• Uncooperative or haemodynamically unstable patient
• Regional (spinal/epidural) may be considered in selected, haemodynamically stable cases

However, if the patient is relatively stable and the surgeon is confident it is a simple strangulation without peritonitis, spinal anaesthesia offers the advantage of avoiding RSI airway management and preserving airway reflexes.

Induction - RAPID SEQUENCE INDUCTION (RSI) - The Cornerstone

1. Preoxygenation: 100% O2 for 3-5 min via tight-fitting mask; aim EtO2 >90%. Critical in smokers due to reduced O2 reserve and COHb. Use high-flow O2 to help displace CO.
2. Patient positioning: Supine with slight head-up tilt (reduces aspiration risk)
3. Sellick manoeuvre (cricoid pressure): Applied by trained assistant before induction - 10N awake, increased to 30N at loss of consciousness; maintained until ETT cuff inflated and position confirmed. (Note: its efficacy is debated but widely practised)
4. Induction agent:
   • Propofol (1.5-2 mg/kg IV) - agent of choice in stable patient; reduces airway reactivity
   • If haemodynamically unstable: Ketamine (1-2 mg/kg) or Etomidate (0.3 mg/kg) - better cardiovascular profile
   • Avoid thiopentone if haemodynamically compromised
5. Neuromuscular blockade:
   • Succinylcholine 1.5 mg/kg IV - gold standard for RSI (fastest onset, ultra-short duration)
   • If succinylcholine contraindicated (K+ >5.5, burns, crush, neuromuscular disease): Rocuronium 1.2 mg/kg with sugammadex available for reversal
   • Do NOT ventilate between induction agent and intubation (avoids gastric insufflation)
6. Intubation: Rapid laryngoscopy; cuffed ETT; confirm position (capnography + bilateral air entry)
7. Have difficult airway trolley ready - smokers may have limited mouth opening (Reinke's oedema), distorted anatomy

Intraoperative Management

• Use heated humidified breathing circuit - reduces heat/moisture loss, helps with secretion management
• Anticipate increased secretions and airway reactivity - have suction ready, maintain adequate depth of anaesthesia before laryngoscopy/intubation
• Avoid light anaesthesia during intubation - smokers have hyperreactive airways - bronchospasm trigger
• Lidocaine 1.5 mg/kg IV 2-3 min before intubation can blunt airway response

• Use lung-protective ventilation: Tidal volume 6-8 mL/kg ideal body weight
• PEEP 5-8 cmH2O to prevent atelectasis
• Monitor peak and plateau airway pressures - smokers/COPD patients have elevated resistance; beware of auto-PEEP
• Maintain SpO2 >95% (but remember pulse oximetry overestimates in the presence of COHb - ABG is more reliable)
• If COPD: allow adequate expiratory time (I:E ratio 1:2.5 or 1:3)

• Start with FiO2 1.0 - helps displace CO from haemoglobin (reduces COHb half-life from 5-6 hours on air to ~60-90 minutes on 100% O2)

• Balanced GA: volatile agent (sevoflurane preferred - least airway irritation) + opioid + NMB
• Sevoflurane or desflurane; desflurane is more airway-irritant - avoid in reactive airway
• Use TIVA (propofol + remifentanil) as alternative in severe bronchospasm risk
• Opioids - fentanyl or morphine; anticipate higher requirements in chronic smokers (opioid tolerance)
• Continue NMB with atracurium or cisatracurium (good in sepsis, not organ-dependent)

• Standard (ECG, NIBP, SpO2, EtCO2, temperature)
• ABG monitoring - mandatory (COHb, acid-base, lactate for bowel ischaemia)
• Invasive arterial line if haemodynamically unstable or prolonged surgery
• CVP/urine output monitoring
• Neuromuscular monitoring (train-of-four)

• Goal-directed fluid therapy; avoid over-resuscitation (third-space losses in strangulated bowel)
• Monitor for sepsis-induced coagulopathy

• Deepen anaesthesia (propofol bolus or increase volatile)
• IV salbutamol or nebulised bronchodilator via circuit
• IV aminophylline (with caution)
• IV hydrocortisone 100-200 mg

Emergence and Extubation

• This is the most hazardous time in a full-stomach/respiratory-compromised patient
• Extubate only when fully awake, following commands, adequate tidal volumes, intact airway reflexes
• Position: left lateral or semi-upright at extubation (reduces aspiration risk)
• Reverse neuromuscular block with neostigmine + glycopyrrolate (or sugammadex if rocuronium used)
• Ensure SpO2 maintained, watch for laryngospasm (smokers with reactive airways)
• Have suction immediately ready
• Consider delayed extubation in theatre if any of: haemodynamic instability, bowel resection, prolonged surgery, high O2 requirements

Postoperative Care

• HDU/ICU admission if: bowel resection done, sepsis, haemodynamic instability, COPD exacerbation
• Continue supplemental oxygen - at minimum 2-4L via nasal prongs for 24-48h
• Incentive spirometry and chest physiotherapy - essential in smokers
• Multimodal analgesia: paracetamol + NSAIDs (if renal function adequate) + opioids; consider TAP block or wound infiltration to minimise opioid requirements
• Watch for postoperative pulmonary complications: atelectasis, pneumonia, respiratory failure
• DVT prophylaxis (smokers are hypercoagulable)
• Early mobilisation
• Nutritional support if malnourished

PART C: POSSIBLE VIVA QUESTIONS (With Answers)

Q1. Why is RSI mandatory in this patient?

Q2. What is the significance of carboxyhemoglobin (COHb) in a chronic smoker?

Q3. How does smoking affect the MAC of volatile agents?

Q4. Which induction agent would you prefer in this emergency patient and why?

• If haemodynamically stable: Propofol (1.5-2 mg/kg) - bronchodilatory, reduces airway reactivity, smooth induction
• If haemodynamically unstable/septic: Ketamine (1-2 mg/kg) - maintains blood pressure via sympathomimesis, bronchodilator, preserves airway reflexes somewhat; or Etomidate (0.3 mg/kg) - minimal cardiovascular depression (note: single dose concerns about adrenal suppression in critically ill)
• Thiopentone causes histamine release - relatively avoid in reactive airway smokers

Q5. What is the difference between succinylcholine and rocuronium for RSI? When would you prefer one over the other?

Q6. What are the perioperative respiratory concerns specific to a chronic smoker?

1. Elevated COHb - impaired O2 delivery
2. Airway hyperreactivity - bronchospasm risk on intubation/extubation
3. Excessive secretions - airway soiling, plugging, atelectasis
4. Impaired mucociliary clearance - postop pneumonia
5. Underlying COPD - V/Q mismatch, CO2 retention, high airway pressures
6. Reduced FRC - earlier desaturation during apnoea
7. Postoperative respiratory failure - risk 1.67 times higher than non-smokers

Q7. Should you use spinal anaesthesia in this case?

• Bowel resection may be needed - unpredictable duration
• Sepsis/haemodynamic instability - spinal vasodilation on an already compromised circulation is dangerous
• High thoracic level needed for adequate block (T4-T6) - risks hypotension, respiratory compromise in a smoker with pre-existing low reserve
• Therefore GA with RSI is usually preferred. Spinal may be considered in isolated, simple, haemodynamically stable cases in expert hands.

Q8. What is the Sellick manoeuvre and what are its limitations?

• Does not prevent active vomiting (can cause oesophageal rupture if pressure maintained)
• Effectiveness questioned by modern imaging studies (oesophagus lies laterally, not directly posterior to cricoid in all patients)
• May worsen laryngoscopic view
• Despite controversy, remains widely practiced as part of RSI

Q9. How would you manage intraoperative bronchospasm?

1. Check ETT position and cuff inflation (rule out endobronchial intubation)
2. Deepen anaesthesia (propofol bolus / increase volatile agent)
3. Suction secretions
4. Salbutamol via ETT (8-10 puffs of MDI via adaptor) or IV (250 mcg slow IV)
5. IV aminophylline 5 mg/kg over 20 min (if not already on theophylline)
6. IV hydrocortisone 100-200 mg
7. IV magnesium sulphate 1.2-2g over 20 min
8. Ketamine infusion (bronchodilator properties)
9. Adrenaline (IV or intratracheal) in life-threatening cases

Q10. What are the effects of COHb on pulse oximetry and how do you correct for it?

Q11. What is the ideal duration of smoking cessation before elective surgery?

• 48 hours: COHb normalises, nicotine effects diminish, mucociliary function begins to improve
• 2 weeks: Significant improvement in sputum production and airway reactivity
• 4-8 weeks: Reduction in postoperative pulmonary complication rates
• >8 weeks (2-3 months): Significant improvement in FVC, FEF25-75%, closing volume, ciliary function, and sputum production; mortality risk decreases
• Note: In an emergency, optimisation is impossible - focus on managing consequences intraoperatively

Q12. What is the concern about nicotine patches perioperatively?

Summary Table: Key Points for Viva