Rapid Sequence Intubation

The near simultaneous administration of a sedative induction agent and a neuromuscular blocking agent to produce optimal conditions for tracheal intubation with a minimal interval of unprotected airway, in a patient assumed to have a full stomach.

Rationale

Every emergency patient is assumed to be at risk of aspiration. The technique minimises the period between loss of airway reflexes and cuff inflation by avoiding positive pressure ventilation during that interval, which would insufflate the stomach and increase regurgitation risk.

The seven Ps: preparation, preoxygenation, pretreatment, paralysis with induction, positioning, placement with proof, and postintubation management.

First pass success

The single most important measure of quality. Complications rise steeply with each additional attempt: hypoxia, hypotension, airway trauma, oesophageal intubation, aspiration and cardiac arrest. The determinants of first pass success are preparation, positioning, adequate preoxygenation and the choice of the most skilled available operator for the first attempt rather than the least skilled learning on the sickest patient.

Indications for intubation

• Failure to maintain or protect the airway: obtunded patient, absent gag with pooling secretions, expanding neck haematoma, angioedema, burns to the airway.
• Failure of oxygenation.
• Failure of ventilation with rising carbon dioxide.
• Anticipated clinical course: progressive burns, penetrating neck trauma, rapidly deteriorating overdose, the need for interhospital transfer, or a patient who will require prolonged imaging or procedures.
• Glasgow Coma Scale of 8 or below is a traditional trigger but is not an absolute rule; the question is whether the airway is protected and whether the trajectory is one of deterioration.

Predicting a difficult airway: LEMON

• Look externally for markers of difficulty: facial trauma, obesity, large teeth, beard, small mandible, short neck, burns, masses.
• Evaluate the 3-3-2 rule: three of the patient's fingerbreadths between the incisors, three between the hyoid and the chin, and two between the thyroid notch and the floor of the mouth. Failure of any of these predicts difficulty in aligning the axes.
• Mallampati score of 3 or 4.
• Obstruction and obesity: stridor, muffled voice, foreign body, epiglottitis, tumour, expanding haematoma.
• Neck mobility reduced by immobilisation, arthritis or ankylosing spondylitis.

Also assess for difficulty with the alternatives: difficult bag mask ventilation, indicated by a beard, obesity, edentulousness, age over 55 and snoring; difficult supraglottic airway placement; and difficult front of neck access from obesity, a fixed flexed neck, previous surgery or radiotherapy.

If a difficult airway is predicted, stop and consult a clinician experienced in airway management before proceeding. Proceeding with rapid sequence intubation in a patient who cannot be intubated or ventilated after paralysis converts a difficult airway into a lethal one. In such patients, awake techniques with topical anaesthesia and maintained spontaneous ventilation, or a planned surgical airway, are the correct approach.

Physiologically difficult airway

Distinct from anatomically difficult. Patients with hypoxia, hypotension, severe metabolic acidosis or right ventricular failure may be anatomically straightforward but tolerate the apnoea and the haemodynamic effects of induction extremely poorly.

Resuscitate before you intubate: correct hypotension with fluid and vasopressors, optimise preoxygenation, and recognise that a patient with a severe metabolic acidosis compensating with a high minute ventilation will arrest if apnoeic for even a short period and requires ventilation matched to their pre intubation minute volume.

Preparation is the diagnostic and organisational phase, and it is where errors are prevented.

Equipment check: MALE MESS

• Mask, correctly sized, with a good seal.
• Airways, oropharyngeal and nasopharyngeal, in a range of sizes.
• Laryngoscopes, checked and working, with both Macintosh and Miller blades and a video laryngoscope where available; and a laryngeal mask airway as a rescue device.
• Endotracheal tubes: adult males 8.0 mm, adult females 7.5 mm, with a size above and below opened and ready. In children over 1 year, uncuffed size equals age divided by 4 plus 4, and cuffed size equals age divided by 4 plus 3.5. Check the cuff before use.
• Monitoring: pulse oximetry, electrocardiography and waveform capnography, all attached before induction. Magill forceps available.
• Emergency drugs and a resuscitation trolley immediately at hand, including vasopressors drawn up.
• Self inflating bag valve resuscitator with a reservoir.
• Suction, tested and placed under the patient's right shoulder where it can be reached without looking, plus a stylet and a bougie.
• Plentiful oxygen supply, with the cylinder or wall supply checked.

Assign roles before starting: intubator, assistant for laryngeal manipulation and equipment, drug administrator, monitor and a person watching the saturation and calling it aloud. Verbalise the plan and the plan for failure before any drug is given.

Preoxygenation

The purpose is to replace nitrogen in the functional residual capacity with oxygen, creating a reservoir that extends the safe apnoeic period from around 1 minute to several minutes.

• Attach nasal prongs and turn them to maximum flow, and leave them in place throughout the entire intubation process including during laryngoscopy. This provides apnoeic oxygenation, which meaningfully extends the time to desaturation, and it costs nothing.
• Spontaneously breathing patient: position the patient and allow at least 5 minutes of spontaneous breathing through a tight fitting non rebreathing mask at maximum flow, continuing until the patient stops breathing after induction. Avoid positive pressure ventilation where possible, since it insufflates the stomach.
• Patient not breathing or breathing inadequately: use a bag valve mask with a reservoir and oxygen at 15 litres per minute, giving 1 breath every 6 seconds synchronised to the patient's own efforts, with gentle pressures, until the highest achievable saturation is reached and sustained.
• In the shocked, obese or critically ill patient, use non invasive positive pressure ventilation or high flow nasal oxygen for preoxygenation where available, since a standard mask may not achieve adequate denitrogenation.
• Aim for a saturation as close to 100 percent as achievable and sustained for several minutes. A patient who will not preoxygenate above 90 percent will desaturate within seconds and needs a different plan.

Positioning

• Ensure 360 degree access to the patient.
• Set the trolley at belt or belly height, with the patient's head at or just above the operator's waist.
• Move the head of the patient to the head of the bed with nothing obstructing the operator.
• Elevate the head of the bed by 30 degrees, and use reverse Trendelenburg in high body mass index, late pregnancy and where spinal immobilisation prevents head elevation. Head up positioning improves preoxygenation, improves the view and reduces regurgitation.
• Align the external auditory meatus with the sternal notch, with the face plane parallel to the ceiling or tilted back by around 10 degrees. In the obese patient this requires substantial ramping with blankets or a purpose made wedge under the shoulders, back and head.
• Have assistants ready to provide external laryngeal manipulation, further head elevation, jaw thrust and mouth opening.

Paralysis with induction

Give the induction agent and the neuromuscular blocker in immediate succession, each followed by a saline flush.

Induction agents

• Ketamine 2 mg/kg intravenously. Preferred in haemodynamic instability, since it preserves sympathetic tone, and in bronchospasm for its bronchodilator effect. It also preserves respiratory drive at induction doses. Reduce the dose to 1 mg/kg in shock, since catecholamine depleted patients may become hypotensive. Raises intraocular pressure modestly and produces emergence phenomena, which are managed with a benzodiazepine afterwards.
• Etomidate 0.3 mg/kg intravenously. Haemodynamically the most neutral agent, with rapid onset and short duration. Causes reversible adrenal suppression after a single dose, the clinical significance of which remains debated, and myoclonus at induction.
• Midazolam 0.15 to 0.2 mg/kg intravenously, with the dose reduced in the elderly and critically ill. It is slower in onset, less reliable and more hypotensive than the alternatives, and it is often underdosed for fear of hypotension, producing awareness under paralysis. If it is the only agent available, give an adequate dose and be prepared to support the blood pressure.
• Propofol 1 to 2 mg/kg where available, reduced substantially in shock, recognising that it is the most hypotensive of the options.
• Reduce all induction doses in shock, and increase the paralytic dose, since a shocked patient has a slow circulation time and a low reserve.

Neuromuscular blocking agents

• Succinylcholine, a depolarising blocker, at 1.5 mg/kg intravenously in adults, 2 mg/kg in infants and 3 mg/kg in neonates. Onset 30 to 60 seconds, duration 6 to 10 minutes. The short duration is its advantage.
• Contraindications: hyperkalaemia including renal failure with a raised potassium; burns beyond 24 to 48 hours from injury; crush injury beyond 24 to 48 hours; denervation injury including spinal cord injury and stroke beyond 72 hours; and neuromuscular disease. In all of these, upregulation of extrajunctional acetylcholine receptors produces massive potassium efflux and cardiac arrest. Organophosphate poisoning is a separate contraindication with a different mechanism: organophosphates inhibit plasma pseudocholinesterase, the enzyme that metabolises succinylcholine, so paralysis is prolonged, sometimes for several hours, rather than the usual 6 to 10 minutes, and prolonged ventilatory support must be anticipated. Rocuronium is often preferred for this reason in known or suspected organophosphate poisoning.
• Also avoid with a personal or family history of malignant hyperthermia.
• Causes bradycardia, particularly in children and with repeat dosing, for which atropine should be available.
• Rocuronium, a non depolarising blocker, at 1.2 mg/kg intravenously. Onset around 45 to 60 seconds at this dose, which is comparable to succinylcholine, with a duration of 20 to 35 minutes. It has no contraindications of consequence in emergency practice and is the preferred agent in many departments for that reason. The longer duration is only a disadvantage if the intubation fails and the patient cannot be ventilated, in which case the airway must be rescued rather than the paralysis waited out. Sugammadex 16 mg/kg reverses it rapidly where available.
• Do not underdose the paralytic. Inadequate paralysis is a leading cause of a poor view and of failed first attempts.

Pretreatment, used selectively rather than routinely: fentanyl 1 to 3 micrograms/kg to blunt the sympathetic response in aortic dissection, raised intracranial pressure and ischaemic heart disease; and atropine 0.02 mg/kg in infants receiving succinylcholine.

Placement

• Wait for full paralysis, which is 45 to 60 seconds, before attempting laryngoscopy. Attempting too early produces a poor view, coughing and trauma.
• Limit each attempt to under 30 seconds, and proceed down the algorithm after 30 seconds or if the saturation falls below 90 percent.
• Use external laryngeal manipulation, with the operator's own right hand initially and then handing over to an assistant to maintain the position.
• Use a bougie liberally rather than as a rescue, particularly for a grade 2 or 3 view.
• Advance the tube under direct vision to the appropriate depth and inflate the cuff.

Proof of intubation

• Waveform capnography is the definitive confirmation, showing a sustained square waveform over at least six breaths with an end tidal carbon dioxide of 35 to 45 mmHg. A colorimetric device is an acceptable alternative but is less reliable, particularly in low cardiac output states.
• Five point auscultation: epigastrium first, then both axillae and both lung bases. Auscultating the epigastrium first identifies an oesophageal intubation before the chest findings can mislead.
• Chest rise, misting in the tube and condensation are unreliable and must not be relied on.
• Unrecognised oesophageal intubation is fatal and is entirely preventable by capnography. If there is no waveform, the tube is in the oesophagus until proven otherwise. Remove it and ventilate.

After successful intubation

• Ventilate with the self inflating bag at 1 breath every 6 seconds, or connect to the ventilator.
• Secure the tube at a depth of approximately three times the tube size at the teeth or gums, so a size 8.0 tube sits at approximately 24 cm.
• Recheck vital signs including blood pressure, pulse, respiratory rate, oxygen saturation, temperature and blood glucose. Anticipate post intubation hypotension from loss of sympathetic tone, from induction agents and from positive pressure ventilation reducing venous return, and treat it with fluid and vasopressors.
• Connect to the ventilator with lung protective settings.
• Initiate post intubation analgesia and sedation immediately. A paralysed patient without sedation is awake and aware, and this is a recurrent and serious failure:
• Morphine 0.1 to 0.4 mg/kg/hour.
• Ketamine 0.05 to 0.4 mg/kg/hour, which provides both analgesia and sedation and preserves blood pressure.
• Midazolam 0.02 to 0.1 mg/kg/hour.
• Dexmedetomidine 0.2 to 0.7 micrograms/kg/hour, which sedates without respiratory depression but which causes bradycardia and hypotension.
• Give an analgesic before or with the sedative, since pain is the commonest cause of apparent agitation.
• Obtain a portable chest radiograph to confirm the depth of the tube. Note that the radiograph confirms depth and excludes endobronchial placement; it does not confirm that the tube is in the trachea rather than the oesophagus, which is the role of capnography.
• Insert a nasogastric or orogastric tube to decompress the stomach.

Failed intubation

• If the attempt is unsuccessful, stop at 30 seconds and resume bag valve mask ventilation with 1 breath every 3 seconds and a two person technique with an oropharyngeal airway, jaw thrust and a good seal.
• Optimise before the next attempt rather than repeating the same approach: change the operator, change the blade, add or improve external laryngeal manipulation, improve the position, use a bougie, use a video laryngoscope, and increase the head elevation.
• Limit attempts to a maximum of three, with the third by the most experienced operator available.
• Insert a supraglottic airway as a rescue if bag mask ventilation is difficult.
• Declare a can't intubate can't oxygenate situation without delay when saturation cannot be maintained despite bag mask ventilation and a supraglottic airway, and proceed immediately to front of neck access with a scalpel, bougie and tube cricothyroidotomy. Hesitation at this point is what kills patients. In children under 8 to 10 years, needle cricothyroidotomy with jet insufflation is used instead given the small cricothyroid membrane.
• Verbalise each step and the transition between plans, so the team knows where in the algorithm they are.