From the Guidelines
Milrinone typically causes a decrease in blood pressure due to its vasodilatory effects, and its use should be carefully considered in patients with low blood pressure or those who are hypovolemic. As a phosphodiesterase-3 inhibitor, milrinone increases cardiac contractility while simultaneously reducing both pulmonary and systemic vascular resistance, which can lead to hypotension, particularly when administered as an IV bolus 1. The standard dosing includes a loading dose of 25-75 mcg/kg given over 10-20 minutes, followed by a continuous infusion of 0.125-0.75 mcg/kg/minute 1. To minimize hypotensive effects, the loading dose should be administered slowly, and patients should be adequately volume-resuscitated before initiation. Blood pressure should be monitored closely during administration, especially during the loading phase and when increasing the infusion rate. If significant hypotension occurs, reducing the infusion rate or providing additional volume support may be necessary. The hypotensive effect occurs because milrinone's vasodilation can outweigh its positive inotropic effects, particularly in patients who are hypovolemic or already taking other vasodilators.
Some key points to consider when using milrinone include:
- Monitoring blood pressure closely during administration, especially during the loading phase and when increasing the infusion rate
- Administering the loading dose slowly to minimize hypotensive effects
- Ensuring patients are adequately volume-resuscitated before initiation
- Reducing the infusion rate or providing additional volume support if significant hypotension occurs
- Considering alternative agents or adjusting the dose in patients with low blood pressure or those who are hypovolemic.
It's also important to note that the choice of inotropic agent should be individualized based on the patient's specific clinical scenario, and the ongoing need for inotropic support and the possibility of discontinuation should be regularly assessed 1. Additionally, lower doses of parenteral inotropic drugs are preferred to minimize adverse effects, and the development of tachyphylaxis should be acknowledged, and the choice of agent may need to be changed during longer periods of support.
From the FDA Drug Label
OVERDOSAGE Doses of milrinone lactate may produce hypotension because of its vasodilator effect. Other cardiovascular adverse reactions include hypotension, 2.9%
Milrinone can cause a decrease in blood pressure, specifically hypotension, due to its vasodilator effect 2. The incidence of hypotension is reported to be 2.9% in patients receiving milrinone lactate 2.
From the Research
Milrinone Effects on Blood Pressure
- Milrinone is a potent positive inotropic and vascular smooth muscle-relaxing agent that can cause a decrease in blood pressure due to its vasodilatory effects 3.
- The drug has been shown to decrease systemic vascular resistance, mean arterial pressure, and left ventricular filling pressure in patients with severe congestive heart failure 3, 4.
- In a study, milrinone caused a significant decrease in mean aortic pressure from 82 +/- 3 to 71 +/- 3 mmHg at the maximum dose administered 3.
- Milrinone has also been compared to nitroprusside, and it was found that milrinone caused a significantly greater increase in stroke work index at the same or lower left ventricular end-diastolic pressure 3.
- The vasodilatory effect of milrinone can be profound, and the resulting hypotension may require the administration of catecholamine pressors or alternative vasopressors like vasopressin 5.
- A study in healthy subjects and patients with renal impairment found a tendency to a decrease in supine blood pressure from 1 to 6-8 hours after oral dosing of milrinone, with the maximal decrease at 2-3 hours 6.
- The overall haemodynamic effect of milrinone is due to significant contributions from both its positive inotropic and its vasodilator actions, making it different from pure vasodilators and relatively pure positive inotropic agents 7.