From the Guidelines
Vasopressin does not increase pulmonary vascular resistance (PVR), it actually increases afterload without pulmonary vasoconstriction. When considering the effects of vasopressin on PVR, it is essential to understand its mechanism of action and how it differs from other vasoactive agents. According to the study by 1, vasopressin increases afterload without causing pulmonary vasoconstriction, which sets it apart from other agents like norepinephrine and epinephrine that can increase pulmonary artery pressure and pulmonary vascular resistance.
The effects of vasopressin on the pulmonary circulation are crucial in critically ill patients, particularly those with pre-existing pulmonary hypertension or right ventricular dysfunction. In these patients, the use of vasopressin may have beneficial effects on right heart function, as suggested by studies 1. However, it is essential to consider the individual patient's condition and the potential risks and benefits of using vasopressin in each case.
Some studies, such as 1, discuss the management of critically ill patients with pulmonary arterial hypertension (PAH) and highlight the importance of maintaining systemic vascular resistance (SVR) greater than pulmonary vascular resistance (PVR) to avoid right ventricular ischemia. While vasopressin is not specifically mentioned as a primary agent for increasing SVR in PAH patients, its use as a replacement-dose vasopressin to offset potential drops in SVR is noted.
In summary, vasopressin does not increase PVR, and its use in critically ill patients requires careful consideration of its effects on the pulmonary circulation and right heart function. Clinicians should be aware of the potential benefits and risks of using vasopressin in patients with compromised pulmonary circulation and make informed decisions based on the individual patient's condition and the latest available evidence 1.
From the FDA Drug Label
Vasopressin causes vasoconstriction by binding to V1 receptors on vascular smooth muscle coupled to the Gq/11-phospholipase C-phosphatidyl-inositol-triphosphate pathway, resulting in the release of intracellular calcium. At therapeutic doses exogenous vasopressin elicits a vasoconstrictive effect in most vascular beds including the splanchnic, renal and cutaneous circulation. In patients with vasodilatory shock vasopressin in therapeutic doses increases systemic vascular resistance and mean arterial blood pressure
Vasopressin increases Pulmonary Vascular Resistance (PVR) by causing vasoconstriction in most vascular beds, including pulmonary circulation, through its effect on V1 receptors 2.
- The pressor effect of vasopressin is proportional to the infusion rate of exogenous vasopressin.
- The increase in PVR is likely due to the vasoconstrictive effect of vasopressin on pulmonary vascular smooth muscle.
From the Research
Effects of Vasopressin on PVR
- Vasopressin has been shown to decrease the pulmonary-to-systemic vascular resistance ratio in various studies 3, 4, 5.
- In a pilot study, arginine vasopressin consistently resulted in a decrease in the ratio of systolic pulmonary artery-to-aortic pressure in pediatric patients with pulmonary hypertension 3.
- A study in a rat model of pulmonary hypertension found that vasopressin decreased pulmonary vascular resistance index (PVRI) and improved right ventricular dilatation and oxygenation 4.
- Another study in a porcine model of severe hemorrhagic shock found that vasopressin increased systemic vascular resistance while sparing the pulmonary vasculature, leading to a 45% decrease in the PVR/SVR ratio 5.
- The effects of vasopressin on PVR are distinct from those of catecholamine vasopressors such as norepinephrine and phenylephrine, which can increase pulmonary vascular resistance 6, 5.
Mechanisms and Implications
- The decrease in PVR/SVR ratio with vasopressin may be associated with selective systemic vasoconstriction and improved cardiac pump function 4, 5.
- Vasopressin may be a useful adjunct in the management of hemorrhagic shock and pulmonary hypertension, as it can help maintain blood oxygenation and prevent hypoxemia 5.
- Further studies are needed to confirm the efficacy and safety of vasopressin in these conditions and to define optimal dosing strategies 3, 4.