II. Indications
- Refractory Ventricular Fibrillation
- Refractory Ventricular Tachycardia
- Not a first line drug, use only after failed use of:
- Electrical cardioversion
- Epinephrine
- Lidocaine
- New ACLS Guidelines (2000) do not refer to Bretylium
- Natural Bretylium sources exhausted
- Severe adverse effects (Hypotension)
III. Mechanism
- Background
- Adrenergic Neuronal blocking drug
- Originally used as an Antihypertensive in 1950s
- Adrenergic Effects (Biphasic) in non-Cardiac Arrest
- Initial (Lasts first 20 minutes after dose)
- Stimulates Norepinephrine release
- Results in Hypertension and Tachycardia
- Subsequent (begins at 20 min and peaks at 60 min)
- Inhibits Norepinephrine release
- Results in Hypotension
- Initial (Lasts first 20 minutes after dose)
- Effects on Fibrillation and Defibrillation
- Increases Ventricular Fibrillation threshold
- Lidocaine also increases fibrillation threshold
- Does not increase Defibrillation threshold
- Lidocaine does increase Defibrillation threshold
- Synergistic response when used with Lidocaine
- Increases Ventricular Fibrillation threshold
IV. Dose
-
General
- Administer as rapid IV push
- Flush the IV line with saline immediately after bolus
- Pediatrics and Adult
- Initial: 5 mg/kg rapid IV push
- Subsequent: 10 mg/kg rapid IV push
- May be repeated every 5-20 min up to twice
- Max total dose of 35 mg/kg
V. Adverse Effects
-
Postural Hypotension (non-Cardiac Arrest patient)
- Seen in 60% of patients
- Arterial Pressure usually falls less than 20 mmHg
- Treatment of symptomatic Hypotension
- Trendelenburg's position
- Vasopressors (e.g. Norepinephrine) rarely needed
- Initial transient effects
VI. Precautions
- May exacerbate Digitalis Toxicity!
- Occurs with Bretylium mediated Catecholamine release
VII. References
- (2000) Circulation 102(suppl I): 86-89
- Katzung (1989) Pharmacology, Lange, p. 179