Key Facts

RSI is performed to secure the airway rapidly while minimising the risk of regurgitation and aspiration of gastric contents. It is one of the most critical skills in anaesthetic, emergency, and intensive care practice.

Epidemiology

Aspiration during anaesthesia occurs in approximately 1 in 3,000-10,000 anaesthetics. RSI is performed in approximately 10-20% of all general anaesthetics. Mortality from aspiration is approximately 5% when it occurs. RSI is the standard induction technique for all emergency surgery in unfasted patients.

Aetiology

Indications for RSI:

• Unfasted patient / emergency surgery
• Bowel obstruction, ileus
• Pregnancy (after 16 weeks)
• Severe GORD, hiatus hernia
• Reduced consciousness (GCS <8)
• Oesophageal pathology (achalasia, stricture)
• Diabetic gastroparesis
• Recent trauma with abdominal injury

Pathophysiology

Aspiration of gastric contents (Mendelson's syndrome) causes chemical pneumonitis from acid (pH <2.5, volume >25mL), leading to acute inflammation, surfactant destruction, and ARDS. Particulate aspiration can cause mechanical airway obstruction. RSI minimises the at-risk period between loss of airway reflexes and tracheal intubation with a cuffed ETT.

RSI Sequence

1. Preparation: Check equipment (ETCO2, suction, bougie, backup plan), preoxygenation
2. Pre-oxygenation: 3 minutes tidal breathing with tight-fitting mask and 100% O2
3. IV induction: Predetermined dose — propofol 2-3mg/kg (or thiopental/ketamine)
4. Neuromuscular blockade: Suxamethonium 1-1.5mg/kg or rocuronium 1.2mg/kg
5. Cricoid pressure: Applied by trained assistant at loss of consciousness (30N)
6. Intubation: After fasciculations cease (suxamethonium) or 60-90s (rocuronium)
7. Confirmation: ETCO2 trace — gold standard

Post-Intubation

• Inflate cuff, confirm ETT position (ETCO2, bilateral chest expansion, auscultation)
• Release cricoid pressure after cuff inflation and ETCO2 confirmed
• Secure ETT, commence anaesthesia

Red Flags

• Failed intubation after RSI — follow DAS failed intubation algorithm
• Aspiration visualised — suction, head-down tilt, continue intubation, bronchoscopy if particulate
• Desaturation during apnoea — consider modified RSI with gentle ventilation in future

Bedside

• ETCO2 (capnography): Mandatory — gold standard for confirming tracheal placement
• SpO2: Continuous monitoring
• Auscultation: Bilateral chest and epigastrium
• Pre-oxygenation assessment: EtO2 >0.87 (87%) confirms adequate denitrogenation

Bloods

• Plasma cholinesterase levels: If suxamethonium apnoea suspected (prolonged paralysis)
• Dibucaine number: Differentiates normal from atypical cholinesterase variants

Imaging

• CXR: If aspiration suspected — diffuse bilateral infiltrates
• CT chest: If severe aspiration with ARDS

Special Tests

• Bronchoscopy: If particulate aspiration suspected — therapeutic removal
• Cholinesterase phenotyping: For suxamethonium apnoea — family screening

Non-pharmacological

• Team briefing: Clear communication of roles (intubator, cricoid pressure, drug administrator)
• Equipment check: Laryngoscope, ETT (check cuff), bougie, suction, SGA as backup, eFONA kit
• Patient positioning: Head elevated 20-30°, ramped in obese patients
• Nil by mouth: 6 hours solids, 2 hours clear fluids where possible (emergency setting may preclude this)

Pharmacological

• Induction agents: Propofol 2-3mg/kg (most common), thiopental 3-5mg/kg (historical), ketamine 1-2mg/kg (haemodynamically unstable patients)
• Suxamethonium 1-1.5mg/kg: Fastest onset (45-60s), ultra-short duration (5-10 min); contraindicated in hyperkalaemia, burns >24h, denervation injuries, malignant hyperthermia susceptibility
• Rocuronium 1.2mg/kg: Alternative — onset 60-90s, longer duration but reversible with sugammadex 16mg/kg
• Opioid co-induction: Fentanyl 1-3mcg/kg or alfentanil 10-20mcg/kg — attenuates haemodynamic response to laryngoscopy
• Aspiration prophylaxis: Ranitidine 150mg PO or IV (when available), sodium citrate 30mL 0.3M PO (obstetrics)

Surgical/Interventional

• eFONA: If CICO scenario develops during RSI
• Bronchoscopy: For particulate aspiration management

Referral Criteria

• Failed RSI — senior anaesthetist involvement
• Aspiration event — ICU care for monitoring and potential ARDS management
• Suxamethonium apnoea — anaesthetic follow-up, family testing, alert card issue

• Aspiration incidence during RSI: <0.05% when properly performed
• Suxamethonium apnoea: Occurs in 1 in 2,500 (heterozygous atypical cholinesterase); 1 in 25,000 (homozygous)
• Mendelson's syndrome mortality: ~5% overall; higher if pH <2.5 and volume >25mL
• RSI first-pass intubation success: >95% in experienced hands
• Rocuronium-based RSI: Equivalent first-pass success to suxamethonium with sugammadex safety net

Suxamethonium vs Rocuronium for RSI

Contraindications to Suxamethonium