Rapid sequence intubation (RSI) is a series of steps that must include administering a paralytic agent to a critically ill or injured patient presumed to have a full stomach. This facilitates rapid orotracheal intubation while minimizing complications. But what are these steps? Teachers commonly use a mnemonic of seven Ps to describe them, but I like to use 10 Ps.
Preoxygenation is a critical step in RSI that often negates the need for interposed positive-pressure ventilation. Preoxygenation will usually be accomplished with a tight-fitting non-rebreather mask on 10 to 15 liters per minute for at least three minutes, ideally with at least 20 degrees of head elevation. After preoxygenation, patients may be categorized as having “adequate,” “limited,” or “no” reserve with corresponding preparations made. (See my previous column: EMN 2006;28:8.)
Protect the C-Spine
Whenever the mechanism of injury suggests a possible cervical spine injury, maintain cervical spine immobilization during the entire intubation process. When intubating a person with suspected cervical spine injury, remove the front of the cervical collar so the mandible can be displaced anteriorly to allow visualization of the vocal cords and have an assistant provide in-line stabilization and possibly a jaw thrust. (Anesthesiology 2004;100:598.)
Pressure to the Cricoid
Cricoid pressure is used to prevent air insufflation during positive pressure ventilation and passive regurgitation. It is critical to avoid overcompressing the larynx and obstructing the airway and recognize that cricoid pressure itself may obscure the laryngeal view. Cricoid pressure should be reduced in the event of difficult laryngoscopy and released to perform external laryngeal manipulation (AKA bimanual laryngoscopy). (See my previous column: EMN 2006;28:24.)
Before paralyzing your patient, it is vital that you pause briefly (the equivalent of the JCAHO timeout) and consider if RSI is really the best option for this patient, whether this is likely to be a difficult intubation, if you are adequately prepared, and what your back-up plan will be in the even of a failed intubation.
Prepare Equipment and People
Being prepared means:
- □ Having medications drawn up, labeled, and ready to go that will be needed to perform the procedure and to maintain sedation, analgesia, and paralysis after the procedure.
- □ Having appropriately sized nasal and oral pharyngeal airways.
- □ Being equipped with a laryngoscope with choice of blades.
- □ Having an appropriately sized self-inflating bag and mask with reservoir and oxygen pre-connected, suction, and endotracheal tubes of the appropriate size as well as one a size smaller for adults and one smaller and one larger for children. A stylette also is usually recommended for emergency intubations. The recommended starting shape is “straight-to-cuff” to “hockey stick.” (“The AirwayCam Guide to Intubation and Practical Emergency Airway Management.” AirwayCam Technologies, Inc. Wayne, PA. 2004.)
- □ Being equipped with a gum-elastic bougie to facilitate the difficult airway.
- □ Having a back-up airway device such as an LMA or Combitube or King-LT available. The device does not necessarily need to be taken out of the package, checked, and lubricated unless you anticipate a difficult airway or things start to go awry. In adults, it is a good idea to have equipment available to perform a surgical airway, though this should be a back-up of last resort.
- □ Having the means to confirm tube placement. This will usually be a qualitative end-tidal CO2 detector.
- □ Being equipped with the means to secure the tube after it has been placed in the trachea. In adults, commercially available devices are usually the easiest to use.
- □ Having a 10 cc syringe to inflate the balloon on a cuffed endotracheal tube.
- □ Having a stethoscope.
- □ Assigning people to appropriate tasks before the procedure begins. These may include someone to administer medications, someone to watch the saturation and report any drop, a staff member to maintain in-line cervical immobilization and jaw thrust, and someone to maintain cricoid pressure, assist with ELM if necessary, and hold the tube and corner of the mouth. The intubator should never have to take his eyes off the vocal cords once visualized.
The first medications given ideally should help reduce the patient's adverse physiologic responses to subsequent medications and the laryngoscopy, such as bradycardia, tachycardia, hypertension, and increased intracranial and intraocular pressure. Potential premedications include atropine, lidocaine, fentanyl, beta-blockers, and defasiculating doses of paralytics. On the basis of available evidence, I consider these agents, except atropine for pediatric patients about to receive succinylcholine, optional or unnecessary. (RSI pharmacology will be reviewed in upcoming columns.)
Position the Patient Optimally
The optimal head position in most older children and adults is the sniffing position (head flexion and neck extension). The goal is to put the ear canal and sternal notch at the same level. In some cases, additional or hyperelevation of the head may be beneficial, and in the morbidly obese, the ramped position is preferred. (J Clin Anesth 2002;14:335; Obesity Surgery 2004;14:1171.) These positions are contraindicated in patients with potential cervical spine injury. In infants, airway position may be optimized with a towel roll behind the shoulders and in small children no padding at all. (Airway positioning will be reviewed in upcoming columns.)
Paralyze and Induce
The purpose of an induction agent is to render the patient unconscious and unresponsive prior to intubation. The purpose of the paralytic is to eliminate muscle tone to optimize laryngoscopy and prevent vomiting and aspiration. (RSI pharmacology will be reviewed in upcoming columns.)
Pass the Tube
Intubation is performed as gently as possible after there is full relaxation of the airway muscles. The onset time of paralysis will depend on the agent used, and in the case of competitive agents, the dose used. It is very important to wait until the patient is fully paralyzed or you risk inducing vomiting and aspiration.
Post-Intubation Management: Confirm, Secure, Sedate, Ventilate
Tube placement should be confirmed objectively with end-tidal CO2. As soon as the tube is confirmed in the trachea, cricoid pressure may be released. The tube should be secured with tape or a commercial device. The patient should receive sedation and analgesia as soon as possible and be placed on a ventilator.