Should Midazolam (Versed) or Fentanyl be used in a post-cardiac arrest patient?

From the Guidelines

Fentanyl should be used as the first-line drug for analgesia and sedation in post-cardiac arrest patients, with midazolam added as needed for sedation, particularly in cases of severe haemodynamic instability. According to the most recent and highest quality study 1, fentanyl is effective for the treatment of shivering and is often used as a continuous infusion for patients after cardiac arrest who are undergoing mechanical ventilation and/or targeted temperature management. The study also suggests that propofol may be added as needed, but midazolam can be considered in cases of severe haemodynamic instability.

Key Considerations

• Fentanyl is generally preferred for analgesia in post-cardiac arrest patients, with a typical dose of 25-100 mcg IV every 1-2 hours as needed or as a continuous infusion at 25-200 mcg/hr, titrated to effect 1.
• Midazolam is more appropriate for sedation, usually started at 1-2 mg IV bolus followed by 1-10 mg/hr continuous infusion 1.
• The ideal approach is often a combination of both medications: fentanyl for pain control and midazolam for sedation, allowing for lower doses of each medication and reducing side effects.
• Careful monitoring of vital signs is essential when administering either medication, as both can cause respiratory depression and hypotension, which may be particularly problematic in hemodynamically unstable post-arrest patients.

Potential Side Effects and Limitations

• Fentanyl can cause respiratory depression, hypotension, and tachyphylaxis, and has a risk of accumulation or withdrawal during prolonged infusion 1.
• Midazolam can cause respiratory depression, hypotension, and delayed awakening, and has a risk of accumulation in kidney dysfunction and propylene glycol toxicity at high doses 1.
• Dose adjustments are necessary for patients with liver or kidney dysfunction, as these organs metabolize and eliminate these medications.

Goal of Sedation and Analgesia

• The goal of sedation and analgesia in post-cardiac arrest patients is to maintain comfort, reduce oxygen consumption, facilitate mechanical ventilation if needed, and potentially provide neuroprotection during targeted temperature management.

From the Research

Sedation Options for Post-Cardiac Arrest Patients

• Midazolam and fentanyl are commonly used sedatives and analgesics in post-cardiac arrest patients, with midazolam being used in 45.2% of cases and fentanyl in 26.8% of cases 2.
• The choice of sedative and analgesic can affect patient outcomes, with some studies suggesting that propofol and remifentanil may be associated with faster recovery times and more ventilator-free days compared to midazolam and fentanyl 3, 4.
• However, the optimal sedation regimen for post-cardiac arrest patients is not well established, and more research is needed to determine the best approach 5.

Pharmacokinetics of Sedatives and Analgesics

• Therapeutic hypothermia can affect the disposition of sedatives and analgesics, with increased elimination half-lives and decreased total clearance for morphine, fentanyl, and propofol 6.
• Midazolam pharmacokinetics are not significantly affected by therapeutic hypothermia 6.
• The effects of hypothermia on sedative and analgesic pharmacokinetics should be considered when selecting a sedation regimen for post-cardiac arrest patients.

Clinical Outcomes

• Sedation and analgesia dosing and titration are associated with delayed awakening, incidence of clinical seizures, and survival in post-cardiac arrest patients 5.
• The use of sedatives and analgesics in the peri-resuscitation period may reduce the risk of skeletal and soft tissue injuries, as well as ischemia-reperfusion brain injury 2.
• Further research is needed to fully understand the relationships between sedation and analgesia regimens and clinical outcomes in post-cardiac arrest patients.