Rapid sequence induction details from millers Anaesthesia
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Rapid-Sequence Induction and Intubation (RSI)
— Miller's Anesthesia, 10th Edition
Definition
Rapid-sequence induction and intubation (RSII, commonly abbreviated RSI in anesthesia literature) is a specialized IV induction technique used when there is an increased risk of gastric regurgitation and pulmonary aspiration. The core sequence:
- Adequate preoxygenation
- Cricoid pressure applied
- IV induction agent given rapidly
- Succinylcholine 1–1.5 mg/kg IV
- Tracheal intubation without attempting PPV
The goal is to achieve optimal intubating conditions rapidly, minimizing the time between loss of consciousness (LOC) and securing the airway with a cuffed endotracheal tube (ETT).
Indications
Standard indications (approaching standard of care):
- Full stomach (NPO guidelines not observed)
- Bowel obstruction
- Pregnancy (historically from 2nd trimester onward — now questioned)
Other situations where RSI may be considered (higher aspiration risk):
- Poorly controlled GERD
- Presence of a nasogastric tube
- Morbid obesity
- Diabetic gastroparesis
- Predicted difficult mask ventilation (but intubation not expected to be difficult — e.g., edentulous, bearded patient)
- Critically ill / hemodynamically unstable patients in emergencies
Cricoid Pressure (Sellick Maneuver)
- Described by Sellick — involves pressure at the cricoid ring to occlude the upper esophagus, preventing regurgitation into the pharynx
- Recommended force: 10 N while awake, increased to 30 N after LOC (based on esophageal manometry and cadaver studies)
Controversy around cricoid pressure:
| Against | For |
|---|---|
| Decreases lower esophageal sphincter tone | Properly applied, reduces aspiration risk |
| MRI shows lateral displacement of esophagus, not compression | Effectiveness due to hypopharyngeal occlusion, not esophageal compression |
| Worsens laryngeal view on DL | Reports of problems likely due to incorrect application |
| Can occlude subglottic airway | Relatively low risk of application |
Current recommendation: Cricoid pressure should generally be applied during RSI. If it interferes with intubation, it should be released. There is insufficient evidence to abandon it entirely.
Induction Agents
Traditional RSI used thiopental (fixed dose). Current practice commonly employs:
- Propofol
- Etomidate
- Ketamine
Some advocate titrating the chosen agent to LOC rather than using a fixed predetermined dose.
Neuromuscular Blocking Drugs
First-line: Succinylcholine
- Dose: 1–1.5 mg/kg IV
- Rapid onset, ultra-short duration
- Depolarizing agent — gold standard for RSI
When succinylcholine is contraindicated:
- Rocuronium 1.0–1.2 mg/kg — provides adequate intubating conditions in <90 seconds
- Vecuronium 0.3 mg/kg — also acceptable
- Key advantage with rocuronium: can be fully reversed with sugammadex, removing the traditional disadvantage of prolonged blockade
- Rocuronium + sugammadex is increasingly used in place of succinylcholine
Modified RSI
No standardized definition exists. In US surveys, most commonly refers to mask ventilation with cricoid pressure applied.
Indications for modified RSI:
- Patients at high risk for rapid hypoxemia: obese, pregnant, critically ill, pediatric
- Emergency situations where preoxygenation cannot be adequately completed
- When longer time to intubating conditions is required (e.g., standard-dose nondepolarizing NMBDs used)
Technique: Gentle PPV with inspiratory pressure <20 cm H₂O in conjunction with cricoid pressure may be acceptable in these scenarios.
Key Steps Summary
| Step | Detail |
|---|---|
| Preoxygenation | Denitrogenation via 100% O₂ for 3–5 min (or 8 vital capacity breaths) |
| Positioning | Ramped/head-up preferred, especially in obese patients |
| Induction agent | Propofol / etomidate / ketamine / thiopental — rapid bolus or titrated to LOC |
| Cricoid pressure | 10 N awake → 30 N after LOC |
| Neuromuscular blockade | Succinylcholine 1–1.5 mg/kg (or rocuronium 1.2 mg/kg) |
| No mask ventilation | Avoid PPV between induction and intubation in classic RSI |
| Intubation | Cuffed ETT as soon as optimal conditions achieved |
| Cuff inflation | Immediately after tube placement |
| Cricoid pressure release | After ETT confirmed in trachea with cuff inflated |
Historical Note
RSI as a technique was first described in 1970. The Sellick maneuver was described even earlier, in 1961.
— Miller's Anesthesia, 2-Volume Set, 10e, pp. 5862–5864
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