No consensus guidelines exist for the management of critically ill patients with pulmonary hypertension in the ED. The mainstays of ED therapy include supplemental oxygen, optimizing intravascular volume, augmenting right ventricular function, maintaining coronary artery perfusion, and decreasing right ventricular afterload (Table 58-2).25
TABLE 58-2Drugs for Pulmonary Hypertension
OXYGEN AND MECHANICAL VENTILATION
While the optimal oxygen saturation is unknown, consensus opinion is to titrate supplemental oxygen to maintain a level >90%.25 Although intubation and mechanical ventilation are common ED therapies for the patient with acute respiratory failure, be wary of the complications. In patients with severe pulmonary hypertension, intubation and ventilation can cause rapid cardiovascular collapse due to increased intrathoracic pressure from positive-pressure ventilation and effects of sedative medications on right ventricular function and systemic vascular resistance.
When mechanical ventilation is needed, set the ventilator to maintain low airway pressure,25 using lung-protective settings (i.e., a tidal volume of 6 mL/kg of ideal body weight and the lowest positive end-expiratory pressure to maintain the oxygen saturation above 90%). Monitor serial plateau pressure measurements and target pressures to <30 cm H2O. Adjust the respiratory rate to avoid hypercapnia, which can increase pulmonary vascular resistance, pulmonary artery pressure, and RV strain.26
Volume overload can cause RV dilation, displacing the intraventricular septum, impairing left ventricular output, and ultimately compromising tissue perfusion.3 For patients who are hypovolemic, give serial boluses of an isotonic crystalloid solution in 250- to 500-mL aliquots with close monitoring. As a result of baseline elevations in right-sided pressures, common methods used to monitor volume responsiveness, such as absolute values of central venous pressure and respiratory variation of the inferior vena cava with US, are less reliable in the patient with pulmonary hypertension.
RIGHT VENTRICULAR FUNCTION
For RV failure, start an inotropic medication to augment function and improve cardiac output. Dobutamine is preferred,25,27,28 starting at 2 micrograms/kg/min and titrated to 10 micrograms/kg/min. Avoid doses >10 micrograms/kg/min, because large doses can increase pulmonary vascular resistance and cause tachydysrhythmias and hypotension.29,30 For patients unable to tolerate dobutamine, milrinone is an alternative. Milrinone is a phosphodiesterase-3 inhibitor and can indirectly augment right ventricular function through a reduction in pulmonary vascular resistance.25 Start milrinone at 0.375 micrograms/kg/min and titrate to a maximum of 0.75 micrograms/kg/min. Higher doses of milrinone can cause hypotension.
RIGHT CORONARY ARTERY PERFUSION
Adequate perfusion of the RCA is necessary to maintain right ventricular function and cardiac output. To maintain RCA blood flow, arterial pressure at the aortic root must be higher than the pulmonary artery pressure. For the hypotensive pulmonary hypertension patient, use a vasopressor to increase aortic root pressure and maintain RCA perfusion. Although there are limited data regarding a singular superior agent, norepinephrine is recommended.25 Norepinephrine improves cardiac output and is initiated at a dose of 0.05 micrograms/kg/min. Avoid high doses of norepinephrine because it can increase pulmonary vascular resistance and impair right ventricular output. Avoid dopamine and phenylephrine because these drugs can cause tachydysrhythmias and can elevate pulmonary artery pressure and pulmonary vascular resistance.
RIGHT VENTRICULAR AFTERLOAD
Reducing right ventricular afterload with pulmonary vasodilators is a critical component in the management of stable patients with pulmonary hypertension. The most commonly used pulmonary vasodilators are prostanoids, endothelin receptor antagonists, and phosphodiesterase-5 (PDE-5) inhibitors. These medications are used primarily in the treatment of patients with pulmonary arterial hypertension; they are rarely, if ever, administered in the ED, but understanding the therapeutic agents is important. Prostanoids (epoprostenol, treprostinil, and iloprost) are potent vasodilators and are the initial treatment of choice in patients with pulmonary arterial hypertension and right ventricular failure. These medications have antiplatelet and antiproliferative properties.1 Epoprostenol is the only therapy proven to improve survival.25 It has a half-life of just 2 to 5 minutes and must be given by continuous IV infusion.31,32 In contrast, treprostinil has a half-life of 4 to 5 hours and is approved for both IV and SC administration.
For the acutely ill pulmonary hypertension patient receiving ongoing IV prostanoid, the first step is to confirm catheter and pump function. If occlusion or malfunction is detected, consult with the primary provider. Both epoprostenol and treprostinil can be administered by peripheral IV. Iloprost is given as an aerosol and is usually reserved for patients unable to tolerate a parenteral prostanoid.25 Side effects of prostanoids include headache, nausea, vomiting, flushing, diarrhea, and jaw pain.1
Endothelin receptor antagonists are administered orally and increase exercise capacity, improve hemodynamics, and can delay the time to clinical worsening in pulmonary hypertension patients.1,33,34,35,36,37 Currently, bosentan and ambrisentan are the only available endothelin receptor antagonists, but neither drug has been evaluated in the acutely decompensating pulmonary hypertension patient with right ventricular failure.25 Side effects of these medications include an elevation in liver transaminase levels and a decrease in hemoglobin concentration.1
The PDE-5 inhibitors sildenafil and tadalafil are approved for use in patients with pulmonary hypertension. They are administered orally, seeking to improve hemodynamics and exercise capacity in patients with pulmonary arterial hypertension.1,38,39,40,41,42,43 Like the endothelin receptor antagonists, they are not currently used in acutely ill pulmonary hypertension patients. Side effects of the PDE-5 inhibitors include headache, flushing, dyspepsia, and hypotension when used concomitantly with nitrates.1