What is the titration dose in ml/hour of nitroglycerin to deliver 5 ug/min, given 50 ug/ml concentration?

Calculating Nitroglycerin Titration Dose

To deliver 5 μg/min of nitroglycerin from a 50 μg/ml concentration, you need to administer 6 ml/hour.

Calculation Method

The calculation for determining the correct titration dose involves a simple conversion:

1. Identify what you have:

   • Concentration: 50 μg/ml
   • Desired dose: 5 μg/min

2. Calculate the flow rate in ml/min:

   • Flow rate (ml/min) = Desired dose (μg/min) ÷ Concentration (μg/ml)
   • Flow rate = 5 μg/min ÷ 50 μg/ml = 0.1 ml/min

3. Convert to ml/hour:

   • Flow rate (ml/hour) = Flow rate (ml/min) × 60 min/hour
   • Flow rate = 0.1 ml/min × 60 min/hour = 6 ml/hour

Clinical Context for Nitroglycerin Administration

When administering intravenous nitroglycerin, several important considerations should be kept in mind:

• The FDA label indicates that nitroglycerin must be diluted in 5% dextrose or 0.9% sodium chloride prior to infusion 1.
• Initial dilution typically involves transferring nitroglycerin into a 500 ml glass bottle of either solution to yield a final concentration of 100 μg/ml 1.
• The European Society of Cardiology recommends intravenous nitrates for patients with acute heart failure with systolic blood pressure > 110 mmHg and may be used cautiously in patients with SBP between 90-110 mmHg 2.

Administration Considerations

• The infusion tubing material significantly affects the delivered dose:

  • Non-absorbing tubing (polyolefin-based) delivers higher plasma concentrations compared to PVC or polyurethane tubing 3.
  • When using non-absorbing infusion sets, start with lower doses (5 μg/min) and titrate carefully 1.

• Titration protocol:

  • Initial titration should be in 5 μg/min increments every 3-5 minutes until response is noted 1.
  • If no response at 20 μg/min, increments can be increased to 10 and later 20 μg/min 1.
  • Once partial response is observed, dose increases should be reduced and intervals between increases lengthened 1.

Monitoring Parameters

• Titration endpoints include:

  • Control of clinical symptoms
  • Decrease in mean arterial pressure (10% in normotensive patients, 30% in hypertensive patients, but never below 90 mmHg systolic)
  • Heart rate increase <10 beats/min (generally not exceeding 110 beats/min)
  • Decrease in pulmonary artery wedge pressure by 10-30% 2, 1

• Although there is no absolute upper dosing limit, doses >200 μg/min are associated with increased risk of hypotension, and alternative therapy should be considered 2, 4.

Remember that nitroglycerin administration requires careful monitoring and individualized titration based on patient response, with the primary goal of delivering the precise dose (in this case, 5 μg/min) through an appropriate infusion rate (6 ml/hour).