(998) When Hope Deflates: A Patient Case of Inhaled Milrinone

Introduction: Inhaled milrinone (iMil) has been investigated for use in pulmonary hypertension (pHTN) and acute respiratory distress syndrome (ARDS). In cardiac surgical patients, iMil has demonstrated decreased mean pulmonary arterial pressure and pulmonary vascular resistance with no effect on heart rate, mean arterial pressure, central venous pressure, or cardiac output. ARDS research suggests iMil has less systemic hypotension and improved oxygenation by increasing alveolar-arterial oxygen gradients compared to systemic milrinone. Inhaled pulmonary vasodilators (epoprostenol, nitric oxide) are used as temporizing measures to definitive treatment, however, these treatments may not be widely available.

Description: A 68 year old male with a history of heart failure with preserved ejection fraction, hypertension, chronic kidney disease, chronic hypoxic respiratory failure on 4 liters of oxygen at baseline presented with shortness of breath, weakness, and lethargy. He was hypercapnic with partial pressure of carbon dioxide 78 mmHg and maintained an oxygen saturation of 85% while on 15 liters nonrebreather. Patient was transitioned to bilevel positive airway pressure (BPAP) with 100% fraction of inspired oxygen. Empiric antibiotic coverage with cefepime and vancomycin was initiated. Cultures were only positive for human metapneumovirus. Diuresis and supportive measures did not improve oxygen demands. Right heart catheterization demonstrated mixed pHTN with mean pulmonary artery pressure 50 mmHg, pulmonary capillary wedge pressure 16 mmHg, thermodilution cardiac index 2.4 L/min, thermodilution pulmonary vascular resistance 5.6 wood units. Continuous iMil 1 mg per hour was nebulized via BPAP as an alternative pulmonary vasodilator. After 6 hours of iMil, arterial blood gas and oxygen saturation remained unchanged. IMil was continued for 24 hours without improvement in symptoms or oxygen requirements. The patient elected to transition to comfort care and expired.

Discussion: This case does not support the current theory of iMil as a therapeutic alternative to traditional pulmonary vasodilators for pHTN or ARDS. Lack of benefit in this case may be attributed to inadequate dosing, as iMil has only been reported as endotracheal tube delivery and no known data exists supporting use via BPAP.