What syringe pump rate in mL per hour is required for Dobutamine at 2 µg/kg/min in a 70‑kg adult using a 1 mg/mL (250 mg/250 mL) solution?

Dobutamine Infusion Rate Calculation

For a 70-kg adult receiving dobutamine at 2 µg/kg/min using a 1 mg/mL (250 mg/250 mL) solution, set the syringe pump to 8.4 mL/hr.

Step-by-Step Calculation

Calculate the Required Dose in µg/min

• For a 70-kg patient at 2 µg/kg/min: 70 kg × 2 µg/kg/min = 140 µg/min 1

Convert to mg/min

• 140 µg/min ÷ 1000 = 0.14 mg/min 1

Convert to mg/hr

• 0.14 mg/min × 60 min/hr = 8.4 mg/hr 1

Calculate mL/hr Based on Concentration

• With a 1 mg/mL concentration: 8.4 mg/hr ÷ 1 mg/mL = 8.4 mL/hr 1

Clinical Context and Dosing Guidelines

Standard Dosing Range

• Dobutamine infusion should be started at a low rate of 0.5-1.0 µg/kg/min and titrated at intervals of a few minutes based on the patient's response, including systemic blood pressure, urine flow, frequency of ectopic activity, heart rate, and measurements of cardiac output when possible 1

• The optimal infusion rates typically range from 2-20 µg/kg/min, though rates slightly outside this range are sometimes necessary 1

• The European Society of Cardiology recommends starting dobutamine at 2.5 µg/kg/min and doubling the dose every 15 minutes according to response, with dose titration usually limited by excessive tachycardia, arrhythmias, or ischemia 2

Hemodynamic Effects at 2 µg/kg/min

• At this starting dose, dobutamine increases cardiac output by selectively augmenting stroke volume, with minimal effect on heart rate or systemic arterial pressure 3, 4

• The drug produces a decrease in total peripheral vascular resistance that is mediated in part by reflex withdrawal of sympathetic tone to the vasculature 4

• Pulmonary wedge pressure typically decreases, improving cardiac performance in patients with ventricular dysfunction 3

Solution Preparation and Stability

Standard Dilution Protocol

• At the time of administration, dobutamine must be diluted in an IV container to at least a 50-mL solution using compatible diluents such as 5% Dextrose Injection, 0.9% Sodium Chloride Injection, or Lactated Ringer's Injection 1

• The intravenous solution should be used within 24 hours of preparation 1

• Concentrations of up to 5,000 µg/mL (5 mg/mL) have been administered to humans, with the final volume determined by the patient's fluid requirements 1

Visual Inspection Required

• Inspect the solution visually before administration and do not use if particulate matter or discoloration is present 1

Monitoring Parameters During Infusion

Essential Clinical Assessments

• Monitor systemic blood pressure continuously, as dobutamine's hemodynamic profile includes minimal changes in mean arterial pressure (typically 93-98 mmHg range maintained) 3

• Track heart rate, expecting only slight increases (approximately 7 beats/min elevation from baseline at therapeutic doses) 3

• Assess urine output as a marker of improved organ perfusion 2

• Monitor for frequency of ectopic activity and arrhythmias, which may limit dose escalation 2, 1

• When possible, measure cardiac output, central venous pressure, and pulmonary capillary wedge pressure to guide titration 1

Common Pitfalls to Avoid

Calculation Errors

• Anesthesiologists have significant difficulty calculating pediatric drug concentrations for continuous infusions, with only 15% providing all correct answers in one study, and incorrect calculations ranging from 50 times too low to 56 times too high 5

• Use electronic infusion pumps rather than manual calculations whenever possible to minimize dosing errors 5

• Double-check all weight-based calculations, as the mean time required for manual calculation is approximately 205 seconds, increasing the risk of errors under time pressure 5

Clinical Management Errors

• Do not use dobutamine as primary treatment in conditions characterized by marked hypotension and shock, as it has less vasopressor activity than norepinephrine or dopamine 6

• Avoid prolonged continuous infusions exceeding 72 hours, as tolerance to dobutamine develops with extended use 7

• Do not mix dobutamine with sodium bisulfite and ethanol-containing agents or diluents 1

• Recognize that dobutamine's mechanism involves complex interactions with β₁-, β₂-, and α₁-adrenoceptors, not just selective β₁-stimulation as previously thought 4