Emergency physicians have established expertise in the field of rapid sequence intubation (RSI). All emergency physicians must be facile not only with the skill of intubation, but also with the different pharmacologic agents appropriate for unique airway scenarios. Ultimately, by maximizing pharmacologic resources, the emergency physician will maximize the potential for success during RSI.
The pharmacology of RSI can be deconstructed into four phases: 1) premedication, 2) sedation, 3) paralysis, and 4) postintubation. The emergency physician’s armamentarium must have enough options to adapt each step to all clinical presentations. This article will focus in detail on each phase of RSI pharmacology.
When intubating a patient, manipulation of the hypopharynx, larynx, and trachea cause a reflex sympathetic response to laryngoscopy (RSRL). The physiologic response caused by RSRL leads to a catecholamine-mediated increase in blood pressure, heart rate, and intracranial pressure (ICP).1 Different case scenarios will dictate how clinically relevant these reflexes are to airway management. Premedication allows the emergency physician to minimize the deleterious effects of laryngoscopy and RSI medications. Classically, the four agents used for premedication have been described by the acronym LOAD (lidocaine, opioids, atropine, and a defasciculating dose). These agents must be given 3-5 minutes prior to sedation and paralysis.
When used as a pretreatment agent, lidocaine is dosed at 1.5 mg/kg intravenously, and the duration of action is approximately 10-20 minutes.1 Lidocaine offers protection in two clinical scenarios: 1) prevention of increase in ICP caused by RSRL, and 2) bronchodilation in reactive airway disease. Robinson and Clancy in the Emergency Medicine Journal published a literature review showing that although this agent does blunt the RSRL-caused ICP increase, there is no evidence of improved neurologic outcome when using lidocaine in head-injured patients.2 However, current recommendations are to premedicate with lidocaine in patients with suspected increases in ICP. Use of lidocaine should be avoided in patients with bradydysrhythmia or hypotension, and in those allergic to amide.
Fentanyl as a pretreatment agent is dosed at 1-3 mcg/kg IV, and the duration of action is approximately 30-60 minutes. Fentanyl is effective at attenuating the catecholamine surge described in RSRL, which can be harmful in patients with increased ICP, ischemic heart disease, abdominal aortic aneurysm, or aortic dissection.3,4 Although dose-related respiratory depression is a concern, this adverse effect becomes less relevant in the setting of RSI. Also, fentanyl should be avoided in patients in shock states and in children.1