Emergency Airway Management & Rapid Sequence Intubation
Decide early, match drugs to physiology, prove placement, and always have an exit
Deciding to intubate
Three indications. A definitive airway (a cuffed tube in the trachea) is needed when the patient cannot protect the airway, cannot oxygenate or ventilate despite noninvasive support, or is on a course that will soon close the airway or exhaust the patient. A GCS of 8 or less with pooled secretions or vomit signals loss of protection. Decide on the trajectory: waiting for an ABG or a falling SpO₂ often means intubating a crashing patient.
Anticipated obstruction. Intubate early, while anatomy is still normal, when swelling is coming: inhalation injury (facial burns, singed nasal hairs, carbonaceous sputum, hoarseness, stridor), an expanding neck hematoma, or progressive angioedema of the tongue or floor of the mouth. Burn edema worsens over hours, especially with fluid resuscitation. ACE-inhibitor angioedema is bradykinin-mediated and responds poorly to epinephrine, antihistamines, and steroids.
When difficulty is predicted and the patient still oxygenates, avoid paralysis: perform awake fiberoptic intubation with a cricothyrotomy setup ready.
Noninvasive ventilation. BiPAP suits alert patients with a COPD exacerbation or cardiogenic pulmonary edema. It is contraindicated with depressed consciousness, vomiting or copious secretions, facial trauma, or hemodynamic instability. A failing trial (rising PaCO₂, worsening acidosis, fatigue, or declining mental status within about 1–2 hours) is itself an indication to intubate.
Predicting difficulty
Anatomic: LEMON.
- Look externally: facial trauma, beard, short thick neck.
- Evaluate 3-3-2: mouth opening 3 fingerbreadths, chin-to-hyoid 3, hyoid-to-thyroid notch 2; less predicts a poor view.
- Mallampati: class III–IV (only soft palate or hard palate visible) predicts difficulty.
- Obstruction/Obesity: obesity and pregnancy also shorten safe apnea time.
- Neck mobility: cervical collar, arthritis. In suspected C-spine injury open the collar front and keep manual in-line stabilization; video laryngoscopy minimizes neck movement.
Physiologic: resuscitate before you intubate. Hypotension, hypoxemia, and severe metabolic acidosis all worsen with induction, apnea, and positive pressure, and they kill more often than difficult anatomy. Give fluids or start a vasopressor with a push-dose pressor drawn up, preoxygenate maximally, and use reduced-dose, hemodynamically neutral induction. In severe metabolic acidosis (DKA, salicylate poisoning) the patient's hyperventilation is compensating: match that high minute ventilation after intubation, or avoid intubation if possible.
Rapid sequence intubation
RSI pushes an induction agent and a paralytic back-to-back so the patient is unconscious and flaccid within about 45–60 seconds, minimizing the unprotected interval.
- PreparationSuction, oxygen, airway devices, bougie, supraglottic device, IV access, monitors, capnography, backup plan
- Preoxygenation100% O₂ for ≥3 min (or 8 vital-capacity breaths), head up 20–30°
- Pre-intubation optimizationFluids, vasopressors, apneic oxygenation
- Paralysis with inductionBoth drugs pushed together
- PositioningEar canal level with the sternal notch ("sniffing"); ramp the obese
- Placement with proofWaveform capnography, then chest radiograph
- Post-intubation managementAnalgesia, sedation, ventilator settings, blood pressure support
Preoxygenation. Deliver 100% oxygen by nonrebreather at flush rate, by bag-mask with a PEEP valve, or by noninvasive ventilation when shunting lungs resist saturation. This replaces alveolar nitrogen with an oxygen reservoir in the functional residual capacity. A healthy adult then tolerates about 8 minutes of apnea before SpO₂ reaches 90%; obese, pregnant, septic, and pediatric patients desaturate far sooner. Apneic oxygenation, a nasal cannula at 15 L/min left on during laryngoscopy, extends the window.
Laryngoscopy. Use a video laryngoscope or bougie when difficulty is predicted, and improve a poor view with external laryngeal manipulation (backward-upward-rightward pressure). Routine cricoid pressure (Sellick maneuver) is no longer recommended because it can worsen the view without reliably preventing aspiration.
RSI drugs
| Feature | Etomidate | Ketamine | Propofol |
|---|---|---|---|
| Mechanism | GABA-A agonist | NMDA receptor antagonist (dissociative) | GABA-A agonist |
| Dose | 0.3 mg/kg | 1–2 mg/kg | 1–2 mg/kg; less in shock or the elderly |
| Blood pressure | Neutral | Maintained or raised (catecholamine release) | Falls (vasodilation, myocardial depression) |
| Best for | Trauma, shock, cardiac disease | Status asthmaticus (bronchodilator), shock | Stable patients; status epilepticus, raised ICP |
| Cautions | Adrenal suppression (11β-hydroxylase), myoclonus, vomiting; no analgesia | Hypersalivation, emergence reactions, myocardial depression if catecholamine-depleted | Hypotension, apnea |
Ketamine spares respiratory drive and airway reflexes, and the old concern that it raises ICP is largely unfounded. Propofol is anticonvulsant and antiemetic and lowers ICP. Midazolam is slower and less predictable for RSI.
| Feature | Succinylcholine | Rocuronium |
|---|---|---|
| Mechanism | Depolarizing nicotinic agonist; fasciculations | Competitive nondepolarizing antagonist |
| RSI dose | 1.5 mg/kg IV | 1–1.2 mg/kg IV |
| Onset / duration | 45–60 s / 6–10 min | ~60 s / 45–60+ min |
| Offset | Plasma pseudocholinesterase; no reversal agent | Sugammadex (any depth); neostigmine (partial block only) |
| Key risks | Hyperkalemia, malignant hyperthermia, bradycardia, masseter spasm | Long paralysis: sedate promptly |
Succinylcholine. Potassium normally rises about 0.5 mEq/L. Bradycardia occurs mainly in children and with repeat doses. Pseudocholinesterase deficiency (inherited, or from severe liver disease or organophosphates) turns a 10-minute block into hours of paralysis; keep the patient sedated and ventilated until it resolves.
Avoid succinylcholine with hyperkalemia or its risk: burns or crush injuries older than ~24–72 hours, denervation (stroke, spinal cord injury, Guillain-Barré, ALS, MS), prolonged immobilization or critical illness, and myopathies such as Duchenne. Upregulated extrajunctional receptors or fragile dystrophic muscle release massive potassium and cause arrhythmic arrest. Also avoid it with a personal or family history of malignant hyperthermia. A burn under 24 hours old is still safe.
Rocuronium. No potassium surge and no malignant hyperthermia make it the choice whenever succinylcholine is contraindicated. Sugammadex, a cyclodextrin, encapsulates rocuronium or vecuronium and reverses even deep block within minutes.
Confirmation and the failed airway
Proving tracheal placement. Continuous waveform capnography, a persistent CO₂ waveform over several breaths, is the most reliable confirmation; a colorimetric detector (purple to yellow) is an acceptable backup. Chest rise, breath sounds, tube fogging, and SpO₂ are unreliable alone. No exhaled CO₂ means esophageal intubation until proven otherwise: remove the tube, reoxygenate by bag-mask, and reintubate. Capnography can read falsely low in cardiac arrest because pulmonary blood flow is poor.
Depth. A chest radiograph then shows depth, not tracheal versus esophageal position: the tip should sit about 3–5 cm above the carina, roughly 21 cm at the teeth in women and 23 cm in men. A tube advanced too far enters the right mainstem bronchus (wider, shorter, and more vertical than the left), causing absent left breath sounds, hypoxemia, high airway pressures, and left lung collapse. Deflate the cuff, pull back to proper depth, and recheck.
Failed airway. About three unsuccessful attempts by an experienced operator, or inability to maintain SpO₂, defines a failed airway:
- Call for help and oxygenateTwo-person bag-mask ventilation with oral and nasal airways
- Supraglottic deviceLaryngeal mask; if oxygenation holds, there is time for an alternative technique
- Can't intubate, can't oxygenateImmediate surgical cricothyrotomy through the cricothyroid membrane (scalpel–bougie–tube)
Children. Below about 10–12 years the cricothyroid membrane is tiny and the larynx funnel-shaped, so surgical cricothyrotomy is contraindicated. Needle cricothyrotomy with transtracheal jet ventilation oxygenates but ventilates poorly (CO₂ climbs), so it only bridges to a definitive airway.
After the tube
Post-intubation hypotension. Induction drugs (vasodilation, myocardial depression), loss of sympathetic drive, and positive-pressure ventilation that reduces venous return all lower blood pressure, most in hypovolemia and sepsis. Also consider tension pneumothorax and auto-PEEP; hypotension soon after intubating a patient with asthma or COPD suggests trapped air, relieved by briefly disconnecting the ventilator.
Sedation. Give analgesia and sedation promptly: rocuronium outlasts most induction agents, so an unsedated patient may be awake under paralysis.