Induction agents used in rapid sequence intubation all lead to a similar endpoint which includes providing sedation and amnesia and can improve intubating conditions. But small pharmacologic differences between these drugs may offer advantages over another in certain clinical scenarios.
Head injury or stroke
The drug of choice in cases where elevated intracranial pressure (ICP) is suspect, whether from traumatic head injury or other conditions, is etomidate.
Ketamine is generally avoided because it is thought to potentially increase ICP through it’s sympathetic stimulation. Although evidence suggesting that ketamine increases intracranial pressure is weak.
Other agents such as propofol and midazolam have been used in cases of elevated ICP, however, because of their relatively increased risk of hypotension compared to etomidate, their use should be considered carefully because of the risk of hypotension induced brain injury.
Status Epilepticus
Propofol and midazolam are two induction agents commonly used in RSI that have anticonvulsive properties and as a result, recommended in the use in status epilepticus requiring intubation. Keep in mind that both propofol and midazolam can cause drops in blood pressure resulting in hypotension. For example, the administration of routine doses for midazolam in RSI (0.2 mg/kg) has been shown to have an average drop in mean arterial blood pressure in healthy patients of 10 to 25 percent. Because of the hemodynamic profile for both propofol and midazolam to cause decreases in mean arterial pressure, their use in status epilepticus when the patient develops hemodynamic compromise is limited.
When blood pressure or shock is of concern in the setting of status epilepticus, etomidate can be used because of its hemodynamic stability, although it has a slightly higher rate of EEG-documented seizure activity compared with other medications.
Ketamine should not be used in status epilepticus because of its stimulant effects.
Reactive Airway Disease
For hemodynamically stable patients with severe bronchospasm requiring intubation, ketamine, or propofol are recommended because of their bronchodilatory properties.
In hypotensive patients, ketamine or etomidate are preferred because of their favorable hemodynamic profiles.
Cardiovascular disease
Because of its hemodynamic stability and absence of induced hypertension, etomidate is the recommended induction agent for patients with significant cardiovascular disease.
Pretreatment with fentanyl, may also be considered, especially in patients with coronary artery disease or in cases of suspected aortic dissection, in order to mitigate the catecholamine release associated with laryngoscopy and intubation.
Shock
Although all induction agents, commonly used in RSI, can cause some degree of hypotension, ketamine and etomidate, are the recommended agents in cases of severe hypotension or shock because of their favorable cardiovascular profiles. Ketamine causes a sympathetic surge that may sustain blood pressure, however both ketamine and etomidate have still been shown to cause small drops in mean arterial pressure in patients with severe hypotension, but less than other agents.
Indications and Contraindications to Rapid Sequence Intubation
Indications for RSI are simply those patients who cannot ventilate, oxygenate or fail to protect their aiway. Contraindications are few and relative.
The ICU Book
A fundamental and respected resource in critical care. Including a review of various common critical care pathology, ariway and mechnical ventilation.
Seven P's of RSI - The Process of Rapid Sequence Intubation
RSI involves the use of an induction agent, followed immediately by a neuromuscular blocking agent to quickly create an optimal environment for intubation.