To the Editor:—
I read with great interest the case report by Dr. Dolinski et al. 1of a patient with severe pulmonary hemorrhage associated with negative-pressure pulmonary edema after an episode of postextubation laryngospasm. Last year, I reviewed six cases of negative-pressure pulmonary edema at my institution. 2Hemoptysis was a feature in five of these, and one patient, like the patient of Dr. Dolinski et al. , had clinical and computed tomography findings consistent with alveolar hemorrhage. This latter patient was also investigated extensively for a vasculitic process to explain the airway bleeding, but no such pathology was found. It seems that airway bleeding is a feature of negative-pressure pulmonary edema. In fact, some have suggested that the condition should be renamed “negative-pressure injury” to reflect the pathophysiology more accurately. 3The negative pressure seems to cause a more severe injury to the lung than could be explained by changes in hydrostatic forces across the pulmonary capillary basement membrane alone. To my knowledge, bronchoscopy has been performed twice during an episode of negative-pressure pulmonary edema. Schwartz et al. 4found fresh blood in the airway in his case of negative-pressure–induced alveolar hemorrhage. Koch et al. 5found hemorrhagic lesions lining the trachea and large airways leading to speculation that bronchial rather than pulmonary capillary disruption was to blame. Analysis of the edema fluid itself has consistently revealed it to be an exudate, 6,7further evidence for disruption of the capillary basement membrane.
I agree that the incidence of this problem is higher than is commonly believed. The incidence of 0.1% of anesthetic procedures reported by Dr. Dolinski et al. is supported an incidence of 0.094% reported by Deepika et al. 8in a much larger series (30 patients). My own smaller series suggested a figure of approximately 0.05%. 2Because the condition can be life threatening and the usual consequence is intensive care admission and a prolonged hospital stay, negative-pressure pulmonary edema is an important cause of perioperative morbidity. I think it is underreported and often misdiagnosed as fluid overload, aspiration, or even bronchospasm.
