1. Describe what an induction agent is and what the optimal characteristics are for an induction agent to be used in RSI.
Ron Walls states that the optimal induction agent “would smoothly and quickly render the patient unconscious, unresponsive and amnestic in one arm/heart/brain circulation time. Such an agent would also provide analgesia, maintain stable cerebral perfusion pressure and cardiovascular hemodynamics, be immediately reversible, and have few, if any, side effects. Unfortunately, such an induction agent does not exist.”
2. What are the advantages and disadvantages of the following induction agents: etomidate, ketamine, propofol and midazolam? Do any of these agents have relative/absolute contraindications?
Etomidate: Pro: hemodynamically stable, rapid on, rapid off. Con: no analgesia, no reversal agent. Debatable downside in sepsis (see question #3 below).
Ketamine: Pro: hemodynamically stable (may actually increase BP and HR), rapid on, rapid off, analgesic agent. Con: No reversal agent. May not be advisable for older patients (especially those with known cardiovascular disease). Historically, ketamine was thought to be bad for induction in head trauma due to an increase in ICP, but recent literature shows that it does not appear to increase ICP, and suggests it may actually be neuroprotective (Filanovsky, 2010).
Propofol: Pro: rapid on/off, anti-epileptic properties. Con: hemodynamically unstable, no reversal agent.
Midazolam: Pro: rapid onset of action, anti-epileptic properties. Con: can be a hemodynamically unstable agent at induction doses (0.3 mg/kg).
3. Why may etomidate be a poor choice in RSI for septic shock? What evidence exists for this potential contraindication?
Etomidate causes transient (up to 48 hours) of adrenal axis suppression with single dose use, leading to decreased response to exogenous cosynotropin stimulation testing. A raging debate has surrounded its use in RSI in patients with sepsis for this reason, and due to studies showing worse outcomes in patients sedated in an ICU setting with etomidate infusions. However, there has never been a study that was adequately powered, randomized, etc., that showed a mortality or morbidity change with single dose etomidate for RSI. A recent study by Tekwani, et al., 2009, showed no significant difference in hospital length of stay or mortality between patients randomized to RSI with etomidate versus midazolam. Etomidate is extremely useful in septic shock for RSI because it is hemodynamically fairly neutral. Given the lack of readily available, superior alternatives, and the lack of sufficient evidence of negative outcomes caused by etomidate for RSI in sepsis, many emergency physicians still use it as their first line induction agent, and advocate as such (Walls and Murphy, 2008). Still others are concerned by the clear-cut evidence of adrenal suppression caused by its use, even without proof that it is connected to bad outcomes, and choose to avoid the drug entirely (Sacchetti, 2008).
4. What agent would you chose for each of the following patients:
1. 18 yo male (approx 100 kg) MVC w/ head trauma, GCS 6, Vitals: 125/70, 80, 100% on NRB (Our answer: etomidate, ketamine, or propofol)
2. 45 yo female w/ status asthmaticus (approx 80 kg), Vitals 95/55, 125, 92% (Our answer: ketamine)
3. 63 yo male w/ pneumonia (approx 80 kg), Vitals: 70/40, 144, 93% on NRB (Our answer: ketamine or etomidate)
4. 47 yo male w/ EtOH withdrawal s/p valium 350 mg over 2 hours, Vitals: 165/95, 137, 98% on NRB (Our answer: propofol)