Drugs to Aid Intubation
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% oxygen for 3 to 5 min; this measure may maintain satisfactory oxygenation in previously healthy patients for up to 8 min. However, oxygen 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 due to 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.