DOPAMINE HYDROCHLORIDE (DOPAMINE)

DOPAMINE HYDROCHLORIDE (DOPAMINE)

CLASSIFICATION

� Natural occurring Catecholamine

MODE OF ACTION

� Dopamine is a precursor of Adrenaline and Noradrenaline

 � It can stimulate alpha, beta, and Dopamine receptors.

� The actions of Dopamine are dose related ie the amount of drug determines which receptors are predominantly stimulated.

� Low dose (2 - 5 mcg/kg/min) Dopamine stimulates Dopamine receptors causing renal and mesenteric vasodilation increasing renal blood flow, glomerular filtration rate and sodium excretion. There are no changes in cardiac output (C.O), stroke volume (S.V), heart rate or myocardial contractility at this dose.

 � Intermediate dose (5 - 20 mcg/kg/min) cause peripheral vasoconstriction (alpha effects) and muscle vasodilation (beta effects) this results in unchanged peripheral vascular resistance. Increases in C.O, S.V, myocardial contractility, renal blood flow, urine output and initial increase in heart rate followed by a decrease to normal rate as the infusion continues.

 � Above 20 mcg/min. Vasoconstriction due to the alpha receptors stimulation, resulting in increases in C.O, myocardial contractility and potential for tachyarrhythmias. Renal blood flow & urine output decreased at this flow rate.

� Half life is approximately 2 minutes.

INDICATIONS

� Cardiogenic and septic shock

 � Low doses may be useful in patients with low C.O or renal impairment.

� Higher doses are infrequently used for inotropic support to increase HR, S.V, and C.O of patients in cardiogenic shock or severe cardiac failure.

CONTRA INDICATIONS

� Atrial or ventricular tachyarrhythmias.

 � Hyperthyroidism.

� Concurrent use with Phenytoin may cause sudden hypotension and bradycardia.

PRECAUTIONS

� Ensure hypovolaemia is corrected first as it may decrease the blood pressure.

 � Use with caution in patients in atrial fibrillation with rapid ventricular response.

 � Patients taking MAO inhibitors or tricyclic antidepressants will need a reduced dose approx 1 / 10th normal dose.

ADVERSE REACTIONS

� Tachycardia, ectopic beats, palpitations hypotension and vasoconstriction

� Nausea, vomiting and headache

� Angina

� Dyspnoea.

 � Ventricular ectopic activity

PRESENTATION

200 mg per 5 ml ampoule

DOSAGE AND ADMINISTRATION

� Renal dose 2 - 5 mcg/kg/min acute renal failure when hypovolaemia is prevented

� Cardiac dose 5 - 10 mcg/kg/min

� Peripheral vasoconstrictor dose 10 - 20 mcg/kg/min NB patient response to varying dosages is individual, the rate of administration of Dopamine is titrated according to the required effects of Dopamine. Dosage needs to be adjusted according to patient response, in particular urine output, tachycardia and arrhythmias. 400 mg Dopamine in 100 mls dextrose (burette) or normal saline (4 mg/ml) 1 mcg/kg/min = 1 ml/hr if adult patient is 66.6 kg

NURSING CONSIDERATIONS

� Dopamine must be given via a CVC, but can be used through normal cannula, strict observation of site to ensure extravasation does not occur. Extravasation of Dopamine into tissue will cause necrosis, ischaemia, and sloughing of the area. If extravasation does occur there must be immediate filtration of the affected area with Phentolamine 5 - 10 mg dilutes in 10 15 ml of 0.9 % sodium chloride, or subcutaneously as soon as possible.

� Dopamine is stable for 24 hours. Flask therefore should be changed every 24/24

� Correct hypovolaemia, electrolyte imbalance acidosis hypercapnia or hypoxia prior to commencement of Dopamine infusion.

 � Monitoring of BP, cardiac status (PA catheter often desirable) and renal output is necessary.

� Pulmonary hypertension maybe exacerbated due to Dopamine induced pulmonary vasoconstriction.

� Weaning: Dopamine must be weaned not ceased suddenly. Low dose Dopamine can be weaned by 1 - 2 mcg/kg/min at hourly intervals. Patients on high dose maybe weaned be 2 - 5 mcg/kg/min intervals every 15 minutes.