What is the dose of dopamine (a catecholamine neurotransmitter) for a 50 kg man with hypotension (blood pressure 80/45 mmHg) given a concentration of 200 mg in 5 ml?

From the Guidelines

For a 50 kg man with hypotension (BP 80/45), I recommend starting dopamine at 5 mcg/kg/min and titrating as needed up to 10 mcg/kg/min, as suggested by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1. To calculate the dose, we can use the following formula: dose (mcg/kg/min) x weight (kg) x 60 min / concentration (mcg/ml).

• The concentration of dopamine is 200 mg in 5 ml, which is equivalent to 40 mg/ml or 40,000 mcg/ml.
• To create a more manageable concentration, we can add this to 250 ml of compatible IV fluid, resulting in a concentration of 800 mcg/ml (200 mg / 250 ml = 0.8 mg/ml or 800 mcg/ml).
• For this patient, the initial infusion rate would be 15.6 ml/hour (5 mcg/kg/min × 50 kg × 60 min ÷ 800 mcg/ml = 18.75 ml/hr, but using the provided concentration of 200 mg in 5 ml, the calculation is 5 mcg/kg/min × 50 kg = 250 mcg/min, 250 mcg/min ÷ 40,000 mcg/ml = 0.00625 ml/min, 0.00625 ml/min × 60 min = 0.375 ml/hr for 200 mg in 5 ml, then 0.375 ml/hr × (250 ml / 5 ml) = 18.75 ml/hr). However, considering the provided dopamine concentration, the calculation should be adjusted to reflect the actual dose needed. Dopamine has dose-dependent effects: at low doses (1-5 mcg/kg/min) it primarily affects dopaminergic receptors improving renal perfusion, at moderate doses (5-10 mcg/kg/min) it stimulates beta-adrenergic receptors increasing cardiac output, and at higher doses (>10 mcg/kg/min) it activates alpha-adrenergic receptors causing vasoconstriction. Monitor the patient's blood pressure, heart rate, urine output, and peripheral perfusion continuously, and be alert for tachyarrhythmias, tissue ischemia, or worsening of existing cardiac conditions as potential side effects.

From the FDA Drug Label

Dopamine Hydrochloride in 5% Dextrose Injection should be infused into a large vein whenever possible to prevent the infiltration of perivascular tissue adjacent to the infusion site. Administration rates greater than 50 mcg/kg/min have safely been used in adults in advanced circulatory decompensation states Begin infusion of dopamine hydrochloride solution at doses of 2 to 5 mcg/kg/min in adult or pediatric patients who are likely to respond to modest increments of heart force and renal perfusion In more seriously ill patients, begin infusion of dopamine hydrochloride at doses of 5 mcg/kg/min and increase gradually, using 5 to 10 mcg/kg/min increments, up to a rate of 20 to 50 mcg/kg/min as needed.

To calculate the dose for a 50 kg man, we need to determine the appropriate dose range.

• The patient has low blood pressure (80/45), which may indicate the need for a higher dose.
• The suggested regimen is to begin infusion at 2 to 5 mcg/kg/min and increase as needed.
• For a 50 kg man, the dose would be:

• 2 mcg/kg/min: 2 mcg/kg/min x 50 kg = 100 mcg/min
• 5 mcg/kg/min: 5 mcg/kg/min x 50 kg = 250 mcg/min

• Since the patient has low blood pressure, we may want to start at the higher end of this range (250 mcg/min) and adjust as needed.
• The dopamine concentration is 200 mg in 5 mL, which is equivalent to 40 mg/mL or 40,000 mcg/mL.
• To deliver 250 mcg/min, we would need:

• 250 mcg/min ÷ 40,000 mcg/mL = 0.00625 mL/min
• Since we want to deliver this dose in mL/hr, we multiply by 60:
• 0.00625 mL/min x 60 = 0.375 mL/hr

• However, the dose range can be increased up to 50 mcg/kg/min as needed, so the maximum dose would be:

• 50 mcg/kg/min x 50 kg = 2500 mcg/min
• 2500 mcg/min ÷ 40,000 mcg/mL = 0.0625 mL/min
• 0.0625 mL/min x 60 = 3.75 mL/hr

The dose for a 50 kg man with low blood pressure could be started at 0.375 mL/hr (250 mcg/min) and adjusted as needed up to a maximum of 3.75 mL/hr (2500 mcg/min) 2.

From the Research

Calculation of Dopamine Dose

To calculate the dose of dopamine for a 50 kg man with blood pressure 80/45, we need to understand the standard dosing of dopamine.

• The standard concentration of dopamine is 200 mg in 5 ml, which is 40 mg/ml.
• The usual dose of dopamine is 5-10 mcg/kg/min, which can be titrated to achieve the desired blood pressure.

Dosing for Hypotension

For a 50 kg man, the dose would be:

• 5 mcg/kg/min: 50 kg x 5 mcg/kg/min = 250 mcg/min
• 10 mcg/kg/min: 50 kg x 10 mcg/kg/min = 500 mcg/min

Conversion to ml/hour

To convert this dose to ml/hour, we can use the concentration of dopamine (40 mg/ml or 40,000 mcg/ml).

• 250 mcg/min: 250 mcg/min / 40,000 mcg/ml = 0.00625 ml/min, which is approximately 0.375 ml/hour
• 500 mcg/min: 500 mcg/min / 40,000 mcg/ml = 0.0125 ml/min, which is approximately 0.75 ml/hour

Clinical Considerations

It is essential to note that the use of dopamine in hypotensive patients, especially those with acute kidney injury, is a topic of debate 3, 4, 5.

• Some studies suggest that norepinephrine may be a better choice than dopamine for hypotensive patients 3, 4.
• Other studies have found no significant difference in mortality between dopamine and norepinephrine 5, 6.
• The choice of vasopressor should be individualized based on the patient's condition and response to treatment 4, 7.