Is vasopressor (vasoconstrictor) therapy effective in patients with pulmonary hypertension?

Vasopressor Use in Pulmonary Hypertension

Vasopressors should be used with caution in pulmonary hypertension, with vasopressin being the preferred agent as it supports systemic vascular resistance without worsening pulmonary vascular resistance. 1

Hemodynamic Principles in Pulmonary Hypertension

• The major guideline for selecting vasopressors in pulmonary hypertension is to maintain systemic vascular resistance (SVR) greater than pulmonary vascular resistance (PVR) 2, 3
• Right ventricular coronary perfusion occurs during both systole and diastole, unlike left ventricular perfusion which occurs only during diastole 2
• If pulmonary vascular resistance exceeds systemic vascular resistance during systole (systolic pulmonary arterial pressure > systolic systemic arterial pressure), right ventricular ischemia can occur 2
• This necessitates higher systolic systemic arterial pressure goals in pulmonary hypertension patients compared to non-pulmonary hypertension patients 2

Preferred Vasopressors in Pulmonary Hypertension

• Vasopressin at replacement doses is recommended to offset potential drops in SVR when using inotropes like dobutamine 2, 3
• Vasopressin has been shown to cause pulmonary vasodilation experimentally and in animal models of pulmonary hypertension 1
• Vasopressin has demonstrated consistent decreases in the ratio of pulmonary-to-systemic vascular resistance in pediatric patients with pulmonary hypertension 4
• Vasopressin may have differential effects on the pulmonary and systemic circulations, allowing systemic pressure support without detrimental effects on the pulmonary circulation 1

Inotropes in Pulmonary Hypertension

• Inotropes that have neutral or beneficial effects on PVR include dobutamine, milrinone, and epinephrine 2
• Dobutamine is often preferred over milrinone due to its shorter half-life, which provides better control in the face of potential hypotension 2
• The selection of inotropes and vasopressors is challenging in pulmonary hypertension patients and requires careful consideration of their effects on both systemic and pulmonary circulation 2

Adjunctive Therapies

• Inhaled nitric oxide (iNO) is recommended for acutely decreasing PVR and improving cardiac output in pulmonary hypertension 2
• iNO has the advantage of not affecting SVR while selectively reducing PVR 2, 3
• iNO can improve oxygenation by augmenting ventilation-perfusion matching and unloading an acutely failing right ventricle 2
• Upon weaning from iNO, a phosphodiesterase inhibitor should be started or restarted as replacement therapy to prevent rebound pulmonary hypertension 2

Monitoring Considerations

• Direct hemodynamic evaluation is recommended in critically ill pulmonary hypertension patients 2
• Central line placement with direct measurement of central venous pressure and mixed oxygen saturation is often necessary 2
• A pulmonary arterial catheter can be useful but is not required 2
• Volume status assessment is notoriously difficult in pulmonary hypertension patients, and non-invasive estimates of central venous pressures may be misleading 2

Pitfalls and Caveats

• No single inotrope or pressor is entirely contraindicated in critically ill pulmonary hypertension patients, but each agent should be considered carefully 2
• Intubation alone can acutely decrease right ventricular preload and increase afterload, potentially precipitating hemodynamic collapse 2
• The effects of induction and sedation agents, combined with the loss of sympathetic drive once work of breathing is relieved, can instigate sudden and potentially irreversible hypotension 2
• Patients with advanced pulmonary hypertension and severe right ventricular dysfunction may be unable to tolerate vasodilators due to negative inotropic effects 2

By carefully selecting vasopressors that maintain SVR while avoiding increases in PVR, clinicians can optimize hemodynamics in pulmonary hypertension patients and reduce the risk of right ventricular failure.