* This is the Professional Version. *
- Clearing and Opening the Upper Airway
- Airway and Respiratory Devices
- Tracheal Intubation
- Surgical Airway
- Complications of Tracheal Intubation
- Drugs to Aid Intubation
- Resources In This Article
Airway Establishment and Control
Airway management consists of clearing the upper airway, maintaining an open air passage with a mechanical device, and sometimes assisting respirations. There are many indications for airway control (see Situations Requiring Airway Control) and many methods of establishing an airway.
Whatever airway management techniques are used, tidal volume should be 6 to 8 cc/kg (significantly less than previously recommended) and ventilatory rate should be 8 to 10 breaths/min (significantly slower than previously recommended to avoid negative hemodynamic consequences).
Situations Requiring Airway Control
To relieve airway obstruction caused by soft tissues of the upper airway and provide optimal position for bag-valve-mask (BVM) ventilation and laryngoscopy, the operator flexes the patient’s neck to elevate the head until the external auditory meatus is in the same plane as the sternum and positions the face roughly parallel to the ceiling (see Figure: Head and neck positioning to open the airway.). This position is slightly different from the previously taught head tilt position. The mandible should be displaced upwards by lifting the lower jaw and submandibular soft tissue or by pushing the rami of the mandible upward (see Figure: Jaw lift.).
Head and neck positioning to open the airway.
Anatomic restriction, various abnormalities, or considerations caused by trauma (eg, inadvisability of moving a possibly fractured neck) may obviate the operator’s ability to employ these maneuvers, but careful attention to optimal positioning can maximize airway patency and improve BVM ventilation and laryngoscopy.
Obstruction by dentures and oropharyngeal foreign material (eg, blood, secretions) may be removed by finger sweep of the oropharynx and suction, taking care not to push the material deeper (more likely in infants and young children, in whom a blind finger sweep is contraindicated). Deeper material can be removed with Magill forceps or by suction.
The Heimlich maneuver consists of manual thrusts to the upper abdomen or, in the case of pregnant or extremely obese patients, chest thrusts until the airway is clear or the patient becomes unconscious; it is the preferred initial method in the awake, choking patient.
In conscious adults, the rescuer stands behind the patient with arms encircling the patient’s midsection. One fist is clenched and placed midway between the umbilicus and xiphoid. The other hand grabs the fist, and a firm inward and upward thrust is delivered by pulling with both arms (see see Figure: Abdominal thrusts with victim standing or sitting (conscious).).
An unconscious adult with an upper airway obstruction is initially managed with CPR. In such patients, chest compressions increase intrathoracic pressure in the same manner that abdominal thrusts do in conscious patients. The oropharynx should be examined before each set of breaths, and any visible objects removed with your fingers. Direct laryngoscopy with suction or Magill forceps can also be used to remove a foreign body in the proximal airway, but once an object has passed through the vocal cords positive pressure from below the obstruction is most likely to be successful.
In older children, the Heimlich maneuver may be used. However, in children < 20 kg (typically < 5 yr), very moderate pressure should be applied, and the rescuer should kneel at the child’s feet rather than astride.
In infants < 1 yr, the Heimlich maneuver should not be done; they should be held in a prone, head-down position, supporting the head with the fingers of one hand, while delivering 5 back blows (see Figure: Back blows—infant.). Five chest thrusts should then be delivered with the infant in a head-down position with the infant’s back on the rescuer’s thigh (supine—see Figure: Chest thrusts—infant.). This sequence of back blows and chest thrusts is repeated until the airway is cleared.
If no spontaneous respiration occurs after airway opening and no respiratory devices are available, rescue breathing (mouth-to-mask or mouth-to-barrier device) is started; mouth-to-mouth ventilation is rarely recommended. Exhaled air contains 16 to 18% O2 and 4 to 5% CO2, which is adequate to maintain blood O2 and CO2 values close to normal. Larger-than-necessary volumes of air may cause gastric distention with associated risk of aspiration.
These devices consist of a self-inflating bag (resuscitator bag) with a nonrebreathing valve mechanism and a soft mask that conforms to the tissues of the face; when connected to an O2 supply, they deliver from 60 to 100% inspired O2. In the hands of experienced practitioners, a BVM provides adequate temporary ventilation in many situations, allowing time to systematically achieve definitive airway control. However, if BVM ventilation is used for > 5 min, air is typically introduced into the stomach, and an NGT should be inserted to evacuate the accumulated air.
These devices do not maintain airway patency, so patients with soft-tissue relaxation require careful positioning and manual maneuvers (see Head and neck positioning to open the airway. and Jaw lift.), as well as additional devices to keep the airway open. An oropharyngeal airway or a nasal trumpet is used during BVM ventilation to keep soft tissues of the oropharynx from blocking the airway. These devices cause gagging and the potential for vomiting and aspiration in conscious patients. Devices must be sized appropriately; an oropharyngeal airway should be as long as the distance between the corner of the patient’s mouth and the angle of the jaw.
Resuscitator bags are also used with artificial airways, including endotracheal tubes and supraglottic and pharyngeal airways. Pediatric bags have an adjustable pressure relief valve that limits peak airway pressures (usually to 35 to 45 cm H2O); practitioners must monitor the valve setting to avoid inadvertent hypoventilation.
An LMA or other supraglottic airway can be inserted into the lower oropharynx to prevent airway obstruction by soft tissues and to create an effective channel for ventilation (see see Figure: Laryngeal mask airway (LMA).). A variety of available LMAs allow passage of an endotracheal tube or a gastric decompression tube. As the name implies, these devices seal the laryngeal inlet (rather than the face-mask interface) and thus avoid the difficulty of maintaining an adequate face-mask seal and the risk of displacing the jaw and tongue. LMAs have become the standard rescue ventilation technique for situations in which endotracheal intubation cannot be accomplished, as well as for certain elective anesthesia cases and emergencies. Complications include vomiting and aspiration in patients who have an intact gag reflex, who are receiving excessive ventilation, or both.
There are numerous techniques for LMA insertion. The standard approach is to press the deflated mask against the hard palate (using the long finger of the dominant hand) and rotate it past the base of the tongue until the mask reaches the hypopharynx so that the tip then sits in the upper esophagus. Once in the correct position, the mask is inflated. Inflating the mask with half the recommended volume before insertion stiffens the tip, possibly making insertion easier. Newer versions replace the inflatable cuff with a gel that molds to the airway.
Although an LMA does not isolate the airway from the esophagus as well as an endotracheal tube, it has some advantages over BVM ventilation: It minimizes gastric inflation and provides some protection against passive regurgitation. Newer versions of LMAs have an opening through which a small tube can be inserted to decompress the stomach.
The efficacy of the airway seal with an LMA, unlike endotracheal tubes, is not directly correlated with the mask inflation pressure. With endotracheal tubes, higher balloon pressure causes a tighter seal; with an LMA, overinflation makes the mask more rigid and less able to adapt to the patient’s anatomy. If the seal is inadequate, mask pressure should be lowered somewhat; if this approach does not work, a larger mask size should be tried.
In emergencies, LMAs should be viewed as bridging devices. Prolonged placement, overinflation of the mask, or both may compress the tongue and cause tongue edema. Also, if noncomatose patients are given muscle relaxants before LMA insertion (eg, for laryngoscopy), they may gag and possibly aspirate when such drugs wear off. Either the device should be removed (assuming ventilation and gag reflexes are adequate), or drugs should be given to eliminate the gag response and provide time for an alternative intubation technique.
Laryngeal mask airway (LMA).
An endotracheal tube is inserted directly into the trachea via the mouth or, less commonly, the nose. Endotracheal tubes have high-volume, low-pressure balloon cuffs to prevent air leakage and minimize the risk of aspiration. Cuffed tubes were traditionally used only in adults and children > 8 yr; however, cuffed tubes are increasingly being used in infants and younger children to limit air leakage (particularly during transport); sometimes cuffs are not inflated or inflated only to the extent needed to prevent obvious leakage.
An endotracheal tube is the definitive method to secure a compromised airway, limit aspiration, and initiate mechanical ventilation in comatose patients, in patients who cannot protect their own airways, and in those who need prolonged mechanical ventilation. It also permits suctioning of the lower respiratory tract. Although drugs can be delivered via an endotracheal tube during cardiac arrest, this practice is discouraged.
Placement typically requires laryngoscopy by a skilled practitioner, but a variety of novel insertion devices that provide other options are becoming available.
Another class of rescue ventilation devices is laryngeal tube or twin-lumen airways (eg, Combitube®, King LT®). These devices use 2 balloons to create a seal above and below the larynx and have ventilation ports overlying the laryngeal inlet (which is between the balloons). As with LMAs, prolonged placement and balloon overinflation can cause tongue edema.
Most patients requiring an artificial airway can be managed with tracheal intubation. Orotracheal intubation, typically done via direct laryngoscopy, is preferred in apneic and critically ill patients because it can usually be done faster than nasotracheal intubation, which is reserved for awake, spontaneously breathing patients or for cases when the mouth must be avoided.
Maneuvers to create a patent airway and to ventilate and oxygenate the patient are always indicated before attempting tracheal intubation. Once a decision to intubate has been made, preparatory measures include
Correct patient positioning (see see Figure: Head and neck positioning to open the airway.)
Ventilation with 100% O2
Readying of necessary equipment (including suction devices)
Ventilation with 100% O2 denitrogenates healthy patients and significantly prolongs the safe apneic time (effect is less in patients with severe cardiopulmonary disorders).
Strategies to predict difficult laryngoscopy (eg, Mallampati scoring, thyromental distance testing) are of limited value in emergencies. Practitioners should always be prepared to use an alternate technique (eg, LMA, BVM ventilation, surgical airway) if laryngoscopy does not work.
During cardiac arrest, chest compressions should not be halted for intubation attempts. If practitioners cannot intubate while compressions are being done (or during the brief pause that occurs during compressor changes), an alternate airway technique should be used.
Suction should be immediately available with a rigid tonsil-tip suction device to clear secretions and other material from the airway.
Anterior cricoid pressure (Sellick maneuver) has previously been recommended before and during intubation to prevent passive regurgitation. However, current literature suggests that this maneuver may be less effective than once thought and may compromise laryngeal view during laryngoscopy.
Drugs (see Airway Establishment and Control : Drugs to Aid Intubation), including sedatives, muscle relaxants, and sometimes vagolytics, are typically given to conscious or semiconscious patients before laryngoscopy.
Most adults can accept a tube with an internal diameter of ≥ 8 mm; these tubes are preferable to smaller ones because they have lower airflow resistance (reducing the work of breathing), facilitate suctioning of secretions, allow passage of a bronchoscope, and may aid in liberation from mechanical ventilation.
For infants and children ≥ 1 yr, uncuffed tube size is calculated by (patient’s age + 16)/4; thus, a 4-yr-old should have a (4 + 16)/4 = 5 mm endotracheal tube. The tube size suggested by this formula should be reduced by 0.5 (1 tube size) if a cuffed tube is to be used. Reference charts (see Guide to Pediatric Resuscitation—Mechanical Measures) or devices such as the Broselow Tape or Pedi-Wheel can rapidly identify appropriate-sized laryngoscope blades and endotracheal tubes for infants and children.
For adults (and sometimes in children), a rigid stylet should be placed in the tube, taking care to stop the stylet 1 to 2 cm before the distal end of the endotracheal tube, so that the tube tip remains soft. The stylet should then be used to make the tube straight to the beginning of the distal cuff; from that point, the tube is bent upward about 35° to form a hockey stick shape. This straight-to-cuff shape improves tube delivery and avoids blocking the operator’s view of the cords during tube passage. Routinely filling the distal endotracheal tube cuff with air to check the balloon is not required; if this technique is used, care must be taken to remove all the air before tube insertion.
Successful intubation on the first attempt is important. Repeated laryngoscopy (≥ 3 attempts) is associated with much higher rates of significant hypoxemia, aspiration, and cardiac arrest. In addition to correct positioning, several other general principles are critical for success:
The laryngoscope is held in the left hand, and the blade is inserted into the mouth and used as a retractor to displace the mandible and tongue up and away from the laryngoscopist, revealing the posterior pharynx. Avoiding contact with the incisors and not placing undue pressure on laryngeal structures are important.
The importance of identifying the epiglottis cannot be overstated. Identifying the epiglottis allows the operator to recognize critical airway landmarks and correctly position the laryngoscope blade. The epiglottis may rest against the posterior pharyngeal wall, where it blends in with the other pink mucus membranes or gets lost in the pool of secretions that invariably exists in the cardiac arrest patient’s airway.
Once the epiglottis is found, the operator may pick it up with the tip of the blade (the typical straight blade approach) or advance the tip of the blade into the vallecula, pressing against the hyoepiglottic ligament, to indirectly lift the epiglottis up and out of the line of sight (the typical curved blade approach). Success with the curved blade depends on the proper positioning of the blade tip in the vallecula and the direction of the lifting force (see see Figure: Bimanual laryngoscopy.). Lifting the epiglottis by either technique reveals the posterior laryngeal structures (arytenoid cartilages, interarytenoid notch), glottis, and vocal cords. If the tip of the blade is too deep, laryngeal landmarks may be entirely bypassed, and the dark, round hole of the esophagus may be mistaken for the glottis opening.
If identifying structures is difficult, manipulating the larynx with the right hand placed on the anterior neck (allowing the right and left hands to work together) may optimize the laryngeal view (see see Figure: Bimanual laryngoscopy.). Another technique involves lifting the head higher (lifting at the occiput, not atlanto-occipital extension), which distracts the jaw and improves the line of sight. Head elevation is inadvisable in patients with potential cervical spine injury and is difficult in the morbidly obese (who must be placed in a ramped or head-elevated position beforehand).
In an optimal view, the vocal cords are clearly seen. If the vocal cords are not seen, at a minimum, the posterior laryngeal landmarks must be viewed and the tip of the tube must be seen passing above the interarytenoid notch and posterior cartilages. Operators must clearly identify laryngeal landmarks to avoid potentially fatal esophageal intubation. If operators are not confident that the tube is going into the trachea, the tube should not be inserted.
Once an optimal view has been achieved, the right hand inserts the tube through the larynx into the trachea (if operators have been applying anterior laryngeal pressure with the right hand, an assistant should continue applying this pressure). If the tube does not pass easily, a 90° clockwise twist of the tube may help it pass more smoothly over the anterior tracheal rings. Before withdrawing the laryngoscope, operators should confirm that the tube is passing between the cords. Appropriate tube depth is usually 21 to 23 cm in adults and 3 times the endotracheal tube size in children (for a 4.0-mm endotracheal tube, 12 cm; for a 5.5-mm endotracheal tube, 16.5 cm). In adults, the tube, if inadvertently advanced, typically migrates into the right mainstem bronchus.
A number of devices and techniques are increasingly used for intubation after failed laryngoscopy or as a primary means of intubation. Devices include
Each device has its own subtleties; practitioners who are skilled in standard laryngoscopic intubation techniques should not assume they can use one of these devices (especially after use of muscle relaxants) without becoming thoroughly familiarized with it.
Video and mirror laryngoscopes enable practitioners to look around the curvature of the tongue and usually provide excellent laryngeal views. However, the tube requires an exaggerated bend angle to go around the tongue and thus may be more difficult to manipulate and insert.
To pass an endotracheal tube through an LMA, practitioners must understand how to optimally position the mask over the laryngeal inlet; there are sometimes mechanical difficulties passing the endotracheal tube.
Flexible fiberoptic scopes and optical stylets are very maneuverable and can be used in patients with abnormal anatomy. However, practice is required to recognize laryngeal landmarks from a fiberoptic perspective. Compared with video and mirror laryngoscopes, fiberoptic scopes are more difficult to master and are more susceptible to problems with blood and secretions; also, they do not separate and divide tissue but instead must be moved through open channels.
Tube introducers (commonly called gum elastic bougies) are semirigid stylets that can be used when laryngeal visualization is suboptimal (eg, the epiglottis is visible, but the laryngeal opening is not). In such cases, the introducer is passed along the undersurface of the epiglottis; from this point, it is likely to enter the trachea. Tracheal entry is suggested by the tactile feedback, noted as the tip bounces over the tracheal rings. An endotracheal tube is then advanced over the introducer. During passage over a tube introducer or bronchoscope, the tube tip sometimes catches the right aryepiglottic fold. Rotating the tube 90° counterclockwise often frees the endotracheal tube tip and allows it to pass smoothly.
The stylet is removed and the balloon cuff is inflated with air using a 10-mL syringe; a manometer is used to verify that balloon pressure is < 30 cm H2O. Properly sized endotracheal tubes may need considerably < 10 mL of air to create the correct pressure.
After balloon inflation, tube placement should be checked using a variety of methods, including
When a tube is correctly placed, manual ventilation should produce symmetric chest rise, good breath sounds over both lungs, and no gurgling over the upper abdomen.
Exhaled air should contain CO2 and gastric air should not; detecting CO2 with a colorimetric end-tidal CO2 device or waveform capnography confirms tracheal placement. However, in prolonged cardiac arrest (ie, with little or no metabolic activity), CO2 may not be detectable even with correct tube placement. In such cases, an esophageal detector device may be used. These devices use an inflatable bulb or a large syringe to apply negative pressure to the endotracheal tube. The flexible esophagus collapses, and little or no air flows into the device; in contrast, the rigid trachea does not collapse, and the resultant airflow confirms tracheal placement.
In the absence of cardiac arrest, tube placement is typically also confirmed with a chest x-ray.
After correct placement is confirmed, the tube should be secured using a commercially available device or adhesive tape. Adapters connect the endotracheal tube to a resuscitator bag, T-piece supplying humidity and O2, or a mechanical ventilator.
Endotracheal tubes can be displaced, particularly in chaotic resuscitation situations, so tube position should be rechecked frequently. If breath sounds are absent on the left, right mainstem bronchus intubation is probably more likely than a left-sided tension pneumothorax, but both should be considered.
If patients are spontaneously breathing, this technique can be used in certain emergency situations—eg, when patients have severe oral or cervical disorders (eg, injuries, edema, limitation of motion) that make laryngoscopy difficult. Historically, nasal intubation was also used when muscle relaxants were unavailable or forbidden (eg, prehospital settings, certain emergency departments) and when patients with tachypnea, hyperpnea, and upright positioning (eg, those with heart failure) might literally inhale a tube. However, availability of noninvasive means of ventilation (eg, bilevel positive airway pressure [BiPAP]), improved access to and training in pharmacologic adjuncts to intubation, and newer airway devices have markedly decreased the use of nasal intubation. Additional considerations are problems with nasal intubation, including sinusitis (universal after 3 days), and the fact that tubes large enough to permit bronchoscopy (eg, ≥ 8 mm) can rarely be inserted nasotracheally.
When nasotracheal intubation is done, a vasoconstrictor (eg, phenylephrine) and topical anesthetic (eg, benzocaine, lidocaine) must be applied to the nasal mucosa and the larynx to prevent bleeding and to blunt protective reflexes. Some patients may also require IV sedatives, opioids, or dissociative drugs. After the nasal mucosa is prepared, a soft nasal trumpet should be inserted to ensure adequate patency of the selected nasal passage and to serve as a conduit for topical drugs to the pharynx and larynx. The trumpet may be placed using a plain or anesthetic (eg, lidocaine) lubricant. The nasal trumpet is removed after the pharyngeal mucosa has been sprayed. The nasotracheal tube is then inserted to about 14 cm depth (just above the laryngeal inlet in most adults); at this point, air movement should be audible. As the patient breathes in, opening the vocal cords, the tube is promptly passed into the trachea. A failed initial insertion attempt often prompts the patient to cough. Practitioners should anticipates this event, which allows a second opportunity to pass the tube through a wide open glottis. More flexible endotracheal tubes with a controllable tip improve likelihood of success. Some practitioners soften tubes by placing them in warm water to lessen the risk of bleeding and make insertion easier. A small commercially available whistle can also be attached to the proximal tube connector to accentuate the noise of air movement when the tube is in the correct position above the larynx and in the trachea.
If the upper airway is obstructed because of a foreign body or massive trauma or if ventilation cannot be accomplished by other means, surgical entry into the trachea is required. Historically, a surgical airway was also the response to failed intubation. However, surgical airways require on average about 100 sec from initial incision to ventilation; LMAs and other devices provide a faster means of rescue ventilation, and very few patients require an emergency surgical airway.
Cricothyrotomy (see see Figure: Emergency cricothyrotomy.) is typically used for emergency surgical access because it is faster and simpler than tracheostomy.
Unlike positioning for laryngoscopy or ventilation, the correct position for cricothyrotomy involves extending the neck and arching the shoulders backward. After sterile preparation, the larynx is grasped with the nondominant hand while a blade held in the dominant hand is used to vertically incise the skin, subcutaneous tissue, and cricothyroid membrane. A tracheal hook helps keep the space open and prevent retraction of the trachea while a small endotracheal tube (6.0 mm internal diameter [ID]) or small tracheotomy tube (cuffed 4.0 Shiley preferred) is advanced through the surgical site into the trachea.
Complications include hemorrhage, subcutaneous emphysema, pneumomediastinum, and pneumothorax. Various commercial products allow rapid surgical access to the cricothyroid space and provide a tube that allows adequate oxygenation and ventilation. Contrary to prior recommendations, needle cricothyrotomy with large bore IV catheters cannot provide adequate ventilation unless a 50-psi driving source (jet insufflator or jet ventilator) is readily available.
Tracheostomy is a more complex procedure because the trachea rings are very close together and part of at least one ring usually must be removed to allow tube placement. Tracheostomy is preferably done in an operating room by a surgeon. In emergencies, the procedure has a higher rate of complications than cricothyrotomy and offers no advantage. However, it is the preferred procedure for patients requiring long-term ventilation.
Percutaneous tracheostomy is an attractive alternative for mechanical ventilated, critically ill patients. This bedside technique uses skin puncture and dilators to insert a tracheostomy tube. Fiberoptic assistance (within the trachea) is usually used to prevent puncture of the membranous (posterior) trachea and esophagus.
Laryngoscopy can damage lips, teeth, tongue, and supraglottic and subglottic areas.
Tube placement in the esophagus, if unrecognized, causes failure to ventilate and potentially death or hypoxic injury. Insufflating a tube in the esophagus causes regurgitation, which can result in aspiration, compromise subsequent BVM ventilation, and obscure visualization in subsequent intubation attempts.
Any translaryngeal tube injures the vocal cords somewhat; sometimes ulceration, ischemia, and prolonged cord paralysis occur. Subglottic stenosis can occur later (usually 3 to 4 wk).
Rarely, tracheostomy insertion causes hemorrhage, thyroid damage, pneumothorax, recurrent laryngeal nerve paralysis, injury to major vessels, or late tracheal stenosis at the insertion site.
Erosion of the trachea is uncommon. It results more commonly from excessively high cuff pressure. Rarely, hemorrhage from major vessels (eg, innominate artery), fistulas (especially tracheoesophageal), and tracheal stenosis occur. Using high-volume, low-pressure cuffs with tubes of appropriate size and measuring cuff pressure frequently (every 8 h) to maintain it at < 30 cm H2O decrease the risk of ischemic pressure necrosis, but patients in shock, with low cardiac output, or with sepsis remain especially vulnerable.
Pulseless and apneic or severely obtunded patients can (and should) be intubated without pharmacologic assistance. Other patients are given sedating and paralytic drugs to minimize discomfort and facilitate intubation (termed rapid sequence intubation).
Pretreatment typically includes
If time permits, patients should be placed on 100% O2 for 3 to 5 min; this measure may maintain satisfactory oxygenation in previously healthy patients for up to 8 min. However, O2 demand and safe apnea times are very dependent on pulse rate, pulmonary function, RBC count, and numerous other metabolic factors.
Laryngoscopy causes a sympathetic-mediated pressor response with an increase in heart rate, BP, and possibly intracranial pressure. To blunt this response, when time permits, some practitioners give lidocaine 1.5 mg/kg IV 1 to 2 min before sedation and paralysis.
Children and adolescents often have a vagal response (marked bradycardia) in response to intubation and are given atropine 0.02 mg/kg IV (minimum: 0.1 mg in infants, 0.5 mg in children and adolescents) at the same time.
Some physicians include a small dose of a neuromuscular blocker (NMB), such as vecuronium 0.01 mg/kg IV, in patients > 4 yr to prevent muscle fasciculations caused by full doses of succinylcholine. Fasciculations may result in muscle pain on awakening and cause transient hyperkalemia; however, the actual benefit of such pretreatment is unclear.
Laryngoscopy and intubation are uncomfortable; in conscious patients, a short-acting IV drug with sedative or combined sedative and analgesic properties is mandatory.
Etomidate 0.3 mg/kg, a nonbarbiturate hypnotic, may be the preferred drug. Fentanyl 5 mcg/kg (2 to 5 mcg/kg in children; note: this dose is higher than the analgesic dose) also works well and causes no cardiovascular depression. Fentanyl is an opioid and thus has analgesic as well as sedative properties. However, at higher doses, chest wall rigidity may occur. Ketamine 1 to 2 mg/kg is a dissociative anesthetic with cardiostimulatory properties. It is generally safe but may cause hallucinations or bizarre behavior on awakening. Thiopental 3 to 4 mg/kg and methohexital 1 to 2 mg/kg are effective but tend to cause hypotension and are used less often.
Skeletal muscle relaxation with an IV NMB markedly facilitates intubation.
Succinylcholine (1.5 mg/kg IV, 2.0 mg/kg for infants), a depolarizing NMB, has the most rapid onset (30 sec to 1 min) and shortest duration (3 to 5 min). It should be avoided in patients with burns, muscle crush injuries > 1 to 2 days old, spinal cord injury, neuromuscular disease, renal failure, or possibly penetrating eye injury. About 1/15,000 children (and fewer adults) have a genetic susceptibility to malignant hyperthermia (see Malignant Hyperthermia) from succinylcholine. Succinylcholine should always be given with atropine in children because pronounced bradycardia may occur.
Alternative nondepolarizing NMBs have longer duration of action (> 30 min) but also have slower onset unless used in high doses that prolong paralysis significantly. Drugs include atracurium 0.5 mg/kg, mivacurium 0.15 mg/kg, rocuronium 1.0 mg/kg, and vecuronium 0.1 to 0.2 mg/kg injected over 60 sec.
Intubation of an awake patient (typically not done in children) requires anesthesia of the nose and pharynx. A commercial aerosol preparation of benzocaine, tetracaine, butyl aminobenzoate (butamben), and benzalkonium is commonly used. Alternatively, 4% lidocaine can be nebulized and inhaled via face mask.
* This is the Professional Version. *