Question

Etomidate.

Hint:

Etomidate is ideal for induction in patients with cardiovascular instability due to its minimal impact on blood pressure, but its use should be cautious in patients with adrenal insufficiency.

Answer 1

Step 1: Introduction to Etomidate.
Etomidate is a short-acting intravenous anesthetic agent commonly used for induction of anaesthesia and for sedation in critically ill patients. It is a imidazole derivative that provides rapid and smooth induction without causing significant respiratory depression. Etomidate is frequently used in emergency and intensive care settings due to its favorable pharmacokinetic profile.
Step 2: Mechanism of Action.
- Etomidate works by potentiating GABA (gamma-aminobutyric aci activity at the GABA-A receptors, leading to central nervous system depression. This results in sedation, hypnosis, and anesthesia.
- Unlike barbiturates or propofol, etomidate has a relatively minimal effect on cardiovascular function, making it a suitable option in hemodynamically unstable patients.
Step 3: Indications for Etomidate Use.
(1) Induction of Anaesthesia:
- Etomidate is commonly used for induction of general anaesthesia in patients who may have compromised cardiovascular function. It is especially beneficial in patients with hypotension, shock, or cardiac disease, as it causes minimal changes to blood pressure and heart rate.
(2) Sedation in Critical Care:
- It is often used for sedation in mechanically ventilated patients or for procedures like endotracheal intubation in the emergency department or intensive care unit.
(3) Rapid Sequence Intubation (RSI):
- Etomidate is a preferred drug for rapid sequence intubation due to its fast onset and short duration of action. It can be used in combination with muscle relaxants to facilitate intubation in emergent settings.
Step 4: Pharmacokinetics and Administration.
(1) Onset and Duration:
- Etomidate has a rapid onset of action, typically within 30-60 seconds after intravenous administration, with a duration of effect lasting around 5-10 minutes. It is metabolized by the liver and excreted in the urine.
(2) Dosing:
- The typical dose for induction of anaesthesia is 0.2-0.3 mg/kg IV, which can be adjusted based on the patient’s clinical condition.
Step 5: Side Effects and Contraindications.
(1) Adverse Effects:
- Adrenocortical Suppression: One of the most significant adverse effects of etomidate is suppression of adrenal steroid synthesis, leading to adrenal insufficiency, particularly when administered repeatedly or for prolonged periods. This effect may last for up to 24 hours after a single dose.
- Injection Site Pain: Pain at the injection site is a common complaint, although it is usually transient.
- Myoclonus: Involuntary muscle movements or myoclonus may occur during induction. This is generally not clinically significant but can be alarming.
- Nausea and Vomiting: These side effects may occur postoperatively in some patients.
(2) Contraindications:
- Etomidate should be used with caution in patients with adrenal insufficiency or those at risk for it. It is generally avoided in pregnancy unless absolutely necessary.
- Severe allergic reactions or hypersensitivity to etomidate or its components may be a contraindication.