Etomidate

Question 1

What is etomidate?

Answer 1

Carboxylated imidazole derivative hypnotic

Presented as clear colourless solution of 2mg/ml in 10ml vial

Question 2

What is the dose of etomidate?

Answer 2

0.3 mg/kg

Question 3

What are the physicochemical properties of etomidate?

Answer 3

Lipid and water soluble (much more water soluble than propofol)

70% bound to plasma proteins

In vial - aqueous solution, pH 8.1 stabilized in 35% propylene glycol = 2mg/ml (0.2% etomidate)

Question 4

What are the SEs of etomidate?

Answer 4

Pain on injection (25%)
Nausea and vomiting
Adrenocortical suppression - inhibits steroid synthesis for 24hrs after 1 dose
Hypersensitivity (1:75000)
Avoid in porphyria
Antiplatelet activity

Question 5

What are the CVS effects of etomidate?

Answer 5

Most stable induction agent
Very little effect on HR, BP, CO or SVR
Myocardial O2 consumption not affected

Question 6

What are the RS effects of etomidate?

Answer 6

Minimal and transient dose-dependent resp depression

Does not inhibit hypoxic pulmonary vasoconstriction

Question 7

What are the CNS effects of etomidate?

Answer 7

Hypnosis
Tremor
Involuntary movements
Decreased tone
Epileptiform activity on EEG in 25%
Decreased ICP, IOP, CPP and CMRO2

Question 8

What is the absorption/distribution of etomidate?

Answer 8

75% protein bound
Rapid distribution
Volume of distribution = 3L/kg

Question 9

What are the uses of etomidate?

Answer 9

Induction of anaesthesia

Treatment of Cushing’s syndrome before surgery

Question 10

What is the MOA of etomidate?

Answer 10

Increased duration of opening of GABA Cl- channels in CNS causes hyperpolarisation and neuronal inhibition

Only the D isomer causes hypnosis

Question 11

How is etomidate metabolised?

Answer 11

It’s an ester and undergoes ester hydrolysis in plasma and liver.

May inhibit plasma cholinesterase

Excreted in urine (90%) and bile (10%)

Question 12

What is the pH of etomidate?

Answer 12

8.1 in solution

Question 13

What is the pKa of etomidate?

Answer 13

4.1

Question 14

What is the onset/offset of etomidate?

Answer 14

Onset 30 secs

Offset 3-7 mins

Question 15

What are the biological properties of an ideal induction agent?

Answer 15

Non-toxic
No physiological effects other than making the patient unconscious
Analgesic

Question 16

What are the physical properties of an ideal induction agent?

Answer 16

Cheap
Long shelf life at room temp
Rapid onset
Rapid offset
No accumulation following infusion
H2O soluble and easy to store
Painless on injection
Safe if injected intraarterially
No interaction with other drugs
No excitation/emergency phenomena