Dobutamine

Dobutamine is a synthetic catecholamine and beta 1 selective inotrope. It raises contractility and cardiac output with less vasoconstriction than adrenaline. It is used in cardiogenic shock and acute heart failure with low output, in septic shock with myocardial dysfunction, and for dobutamine stress echocardiography.

Classification. Inotrope; beta 1 adrenergic agonist with weak beta 2 and alpha 1 activity.

Mechanism. Racemic mixture: the dextro isomer is a beta 1 and beta 2 agonist and alpha 1 antagonist, the laevo isomer is an alpha 1 agonist. Net effect is increased contractility and mild peripheral vasodilation.

Pharmacodynamics. Onset 1 to 2 minutes; peak effect about 10 minutes. Heart rate rises modestly at moderate doses; systemic vascular resistance falls slightly. Atrial fibrillation rate can rise. Tolerance appears after 48 to 72 hours of infusion.

Pharmacokinetics. Inactive orally. Half life about 2 minutes. Metabolised by catechol O methyltransferase and conjugation; excreted in urine.

Cardiogenic shock and acute decompensated heart failure with low output, adult.

• Start 2.5 to 5 micrograms/kg/min IV.

• Titrate every 15 to 30 minutes to 10 micrograms/kg/min; usual range 2.5 to 20 micrograms/kg/min.

• Maximum 40 micrograms/kg/min is labelled, but doses over 20 give more arrhythmia without added output.

• No loading dose; do not give a bolus.

• Duration: shortest effective course, usually 24 to 72 hours; reassess need daily.

Septic shock with low cardiac output despite adequate volume and vasopressor. 2.5 to 20 micrograms/kg/min, titrated to cardiac output and lactate; add to noradrenaline.

Dobutamine stress echocardiography, adult. Infuse 5, 10, 20, 30 and 40 micrograms/kg/min in 3 minute stages; add atropine 0.25 to 0.5 mg IV in increments, total 2 mg, if the target heart rate (85% of age predicted maximum) is not reached. Stop for ischaemia, arrhythmia, severe hypertension or hypotension.

Children. 2 to 20 micrograms/kg/min; specialist use.

Patients on beta blockers. Response is reduced; higher doses or an alternative inotrope such as milrinone may be required.

Contraindications. Hypertrophic obstructive cardiomyopathy; severe mechanical outflow obstruction; phaeochromocytoma; uncorrected hypovolaemia; sulphite allergy where the product contains it.

Warnings. Ventricular and supraventricular arrhythmias, tachycardia, and myocardial ischaemia. May worsen hypotension through vasodilation. Hypokalaemia. Extravasation can cause local injury. Avoid prolonged infusions without reassessment.

Adverse effects. Palpitations, ectopics, tachycardia, hypertension, headache, nausea, tremor, chest pain, hypokalaemia.

Interactions. Beta blockers antagonise. Monoamine oxidase inhibitors and tricyclic antidepressants increase pressor response. Halogenated anaesthetics: arrhythmia. Nitroprusside adds to the rise in cardiac output.

Special groups.

• Pregnancy: use only if essential; limited data.

• Breastfeeding: no data.

• Children: dose by weight.

• Older adults: start low; arrhythmia and ischaemia risk.

• Kidney and liver impairment: no adjustment.

Formulations. Injection 12.5 mg/mL (20 mL vial, 250 mg); premixed bags.

Preparation. Dilute before use in 5% glucose or 0.9% sodium chloride, for example 250 mg in 250 mL (1 mg/mL) or 250 mg in 50 mL (5 mg/mL) through a central line. The diluted solution may turn pink but remains potent for 24 hours. Incompatible with alkaline solutions such as sodium bicarbonate.

Baseline. ECG, blood pressure, potassium, magnesium, echocardiography or cardiac output estimate.

Monitoring. Continuous ECG and arterial pressure, heart rate, urine output, lactate, perfusion, potassium. Reduce or stop for heart rate over 120 to 140/min, new arrhythmia or ischaemia.

Weaning. Reduce by 1 to 2.5 micrograms/kg/min every 30 to 60 minutes while watching for relapse.

Common prescribing errors. Giving a loading bolus; infusing without checking volume status; continuing beyond tolerance without reassessment; ignoring the reduced response with beta blockers.