Nimodipine-induced acute hypoxemia: case report.

Objective and Importance: Nimodipine is commonly used to improve neurological outcomes after subarachnoid hemorrhage. Although nimodipine reportedly has high specificity for the cerebral vasculature, adverse systemic effects such as hypotension have been described. This case report describes a patient with traumatic subarachnoid hemorrhage who experienced two episodes of previously undescribed, life-threatening hypoxemia that was directly related to nimodipine therapy.
Clinical Presentation: The patient experienced acute hypoxemia (partial pressures of oxygen of 32.9 and 58.7 mm Hg), on two separate occasions (3 d apart), that was temporally related to single doses of nimodipine therapy for traumatic subarachnoid hemorrhage. Other disease- and medication-related causes did not explain these episodes.
Intervention: After the inspired oxygen concentration was increased to 100% (both episodes) and the positive end expiratory pressure was increased to 7.5 mm Hg (first episode), the arterial oxygen saturation of the patient returned to baseline levels (>99%) within 40 minutes in each instance. Nimodipine therapy was discontinued after each episode.
Conclusion: It is hypothesized that, in the presence of concomitant adult respiratory distress syndrome, nimodipine increased ventilation/perfusion ratio mismatch, through its direct vasodilatory effects on the pulmonary artery, and possibly interfered with the reflex hypoxic pulmonary vasoconstriction necessary to maintain adequate oxygenation for this patient. Clinicians should carefully monitor the oxygenation status of patients when nimodipine therapy is initiated.