Vol. 17 •Issue 7 • Page 44
Emergency Airway Management
Understanding the principles of rapid sequence intubation for pediatric patients
A 16-year-old restrained passenger in a car struck by a truck is found unconscious, opening her eyes to painful stimulation but not moving.
She has a cephalohematoma and scalp laceration. It is determined she will need intubation, so 100 percent oxygen is given by non-rebreather mask while she is extricated from the car. Once she is removed from the vehicle, her spine is immobilized, and the aeromedical team administers lidocaine, etomidate, and rocuronium. She is then successfully orotracheally intubated.
The sequence of events leading to this patient’s intubation is called rapid sequence intubation or RSI. The term describes a sequence of actions that facilitate rapid and safe direct laryngoscopy and tracheal intubation (DLTI) in a patient presumed to have a full stomach. The sequence uses the concomitant
administration of sedatives and neuromuscular blockers to create intentional rapid onset of apnea and paralysis to facilitate direct laryngoscopy and passage of the endotracheal tube.
The technique was developed to help clinicians manage the airway in a decompensating patient presenting to the emergency department or, as in our hypothetical case, the aeromedical field. It is intended for use in nonarresting, noncomatose patients with intact or depressed upper-airway reflexes.
RSI is now a standard part of emergency medicine training and also is taught in resuscitation courses such as pediatric advanced life support.
Because RSI has a high success rate and is associated with a low risk for serious adverse events, it is the preferred method for intubation in emergency rooms.1
In order to understand the protective effects RSI provides, one must first become familiar with the airway protective and hemodynamic effects stimulated by DLTI.
First, DLTI stimulates protective airway reflexes such as coughing, gagging, swallowing, and sneezing, which can lead to pulmonary aspiration of gastric and oral contents. DLTI also can trigger apnea, laryngospasm, and bronchospasm.
The sympathetic and adrenal medullary systems are activated, leading to systemic hypertension, tachycardia, increased myocardial oxygen consumption, increased cerebral perfusion pressure, and elevated intracranial pressure.
Finally, placement of the larnygoscope and endotracheal tube can cause bradyarrhythmias in children younger than 5 by vagus nerve stimulation.
The sequence of events and medications administered during RSI can control these reflexes, lowering the risk for aspiration and undesired changes in hemodynamics.
Once the clinician determines that RSI is necessary, then all appropriate personnel, equipment, and medications should be gathered for an organized, safe, and rapid intubation.
The sequence of RSI events is as follows:
- evaluation and assessment
- preparation and pre-oxygenation
- cricoid pressure
- DLTI (if unsuccessful, options include bag-valve-mask ventilation, laryngeal mask airway, cricothyrotomy)
- manage intubated patient
RSI begins with evaluation and assessment of the patient. It is necessary to obtain a good patient history before intubation.
Often there is not enough time to get a detailed medical history, so the clinician should quickly collect information about the patient’s history that will help guide the choice of medications and equipment to use and avoid during RSI.
Using the mnemonic AMPLE adapted from the American Heart Association’s pediatric advanced life support course, you can quickly learn the following about the patient:
- drug Allergies
- current Medications
- Past medical history
- last Meal
- Existing circumstances and events leading to the need for intubation.2
The clinician also should perform a quick physical examination paying particular attention to the head and neck. This often is difficult to perform in an anxious and fearful child. If there is any suspicion that the patient has a difficult airway, then RSI is not the preferred method for intubation. In this case, an anesthesiologist or an otolaryngologist should be called for assistance with intubation. In the meantime, the airway should be managed with noninvasive methods.
Preparation and pre-oxygenation
As soon as the decision to intubate is made, begin pre-oxygenation with 100 percent FiO2or the highest oxygen concentration available. This pre-oxygenation helps to increase the hemoglobin and plasma oxygen saturation by washing out airway nitrogen. If done for at least two minutes before induction of apnea, the patient will have a reservoir of oxygen at functional residual capacity. This buys time for intubation without the need for supplemental oxygen.3
Clinicians should avoid using positive pressure ventilation to minimize the entry of air in the stomach because this can lead to pulmonary aspiration of gastric contents.4While the patient is being pre-oxygenated, all necessary equipment and personnel should be gathered. (See Table) The most skillful person available should be the one to intubate. At least one respiratory therapist and nurse should be at the bedside to assist the person performing the intubation.
Pre-medication, sedation, paralysis
Next, the patient should be medicated with adjunctive agents. Atropine should be used in children younger than age 1 to pre-treat vagal stimulation caused by direct laryngoscopy. Atropine also should be used in any patient already bradycardic before intubation. Finally, since succinylcholine can cause bradycardia and asystole, atropine should be given to adolescents needing a second dose of succinylcholine and children ages 1 to 5 before receiving succinylcholine.
Intravenous lidocaine is useful for attenuating adrenergic and physiologic responses to DLTI. Lidocaine should be given to help lower intracranial or intraocular pressure in patients with known or presumed elevations in either of these pressures.
Analgesics with rapid onset can be used to blunt the sympathetic response to DLTI and provide analgesia. Some sedatives have analgesic properties, making this step unnecessary.
Priming or “defasciculating” agents are also used at this stage. Succinylcholine is a nondepolarizing neuromuscular blocker. It causes muscle fasciculations before the onset of paralysis. In order to defasciculate, use one-tenth of the paralytic dose of either succinylcholine or a nondepolarizing agent before giving the paralytic dose of succinylcholine.
Alternatively, if the team plans to use a nondepolarizing neuromuscular blocker, you can speed up the onset of paralysis if you prime with one-tenth of the paralytic dose of these agents. The priming or defasciculating dose should ideally be given one to three minutes before the paralytic dose is given.5Obviously, sedation should be given before paralysis is obtained to avoid having an awake patient paralyzed. The agent chosen should have a rapid onset of action and minimal side effects. Each drug has advantages and disadvantages for specific clinical scenarios. The clinician should be familiar with the common side effects of these drugs and should know when to use a specific agent for a clinical situation. The ideal paralytic has rapid onset of action and short duration or reversibility or both.
External pressure applied over the cricoid cartilage is a key maneuver in RSI. It provides three significant advantages. First, cricoid pressure (CP) helps bring the infant’s or child’s anterior larynx more posterior and in line with the oral pharynx. This maneuver helps the clinician visualize the vocal cords.
Second, CP closes off the esophagus to prevent air insufflation of the stomach. Third, it helps prevent refluxed gastric contents from entering the pharynx, preventing pulmonary aspiration of gastric contents.
The application of CP should come after paralysis and sedation. Firm pressure should be applied over the cricoid cartilage using single- or double-handed technique.6
Direct laryngoscopy and intubation
Sedation, paralysis, and application of CP should be done in 60 to 90 seconds. When the patient is positioned, the mouth can be opened and the laryngoscope blade inserted.
Miller blades can be used to lift the -epiglottis in young children and infants. Macintosh blades can be placed in the valecula to help indirectly lift the epiglottis for vocal cord visualization in older children and adults. The patient should be intubated with an appropriate-sized endotracheal tube.
Cuffed tubes, once contraindicated, may be used in infants if available. The cuff can be inflated to help ventilation if there is a significant air leak around the endotracheal tube. This helps to prevent the need for additional intubation attempts.
Endotracheal tube placement should be confirmed with visualization of the tube passing through the vocal cords, observing chest rise with ventilation, and detection of end-tidal carbon dioxide. A chest X-ray also should be performed to look at tube positioning.
Mechanical ventilation should begin as soon as possible. Initial settings should compensate for paralysis. Bag-valve ventilation should be used until mechanical ventilation begins without risk of increased gastric air entry. A nasogastric or orogastric tube should be placed to decompress a distended stomach and bowel.
Longer-acting sedatives and analgesic agents should be administered for patient comfort and safety.
The clinician also should be prepared to manage the intubated patient or the airway of a patient in whom RSI is unsuccessful. If intubation is unsuccessful while the patient is still sedated and paralyzed, the clinician should begin rescue procedures to maintain the airway until other personnel arrive to help secure the airway.
One option is to use bag-valve-mask ventilation. In this case, the placement of a nasogastric tube should be placed to decompress a distended stomach. Another option is the placement of a laryngeal mask airway. This may help to avoid some of the air entry into the stomach caused by using bag-valve-mask ventilation.
If the team cannot deliver oxygen, or if there is difficulty ventilating the patient with these maneuvers, then a surgical airway should be obtained.
For a list of references, look under the “Magazine” tab at www.advanceweb.com/respmanager.
Nicole M. Johnson, MD, is a board-certified pediatrician and a fellow training in pediatric critical care at University Hospitals Case Medical Center, Rainbow Babies and Children’s Hospital, Cleveland. Michael R. Anderson, MD, is an associate professor of pediatrics and attending physician in pediatric critical care at Rainbow.
Table: Essential equipment
- functional intravenous access
- syringe for endotracheal tube cuff inflation
- properly sized endotracheal tube
- properly sized stylet
- properly sized and functioning laryngoscope and blade
- end-tidal CO2detector
- monitor of oxygen saturation, blood pressure, heart rate and rhythm