Noncardiogenic pulmonary edema in small animals

OBJECTIVE

To review various types of noncardiogenic pulmonary edema (NCPE) in cats and dogs.

ETIOLOGY

NCPE is an abnormal fluid accumulation in the lung interstitium or alveoli that is not caused by cardiogenic causes or fluid overload. It can be due to changes in vascular permeability, hydrostatic pressure in the pulmonary vasculature, or a combination thereof. Possible causes include inflammatory states within the lung or in remote tissues (acute respiratory distress syndrome [ARDS]), airway obstruction (post-obstructive pulmonary edema), neurologic disease such as head trauma or seizures (neurogenic pulmonary edema), electrocution, after re-expansion of a collapsed lung or after drowning.

DIAGNOSIS

Diagnosis of NCPE is generally based on history, physical examination, and diagnostic imaging. Radiographic findings suggestive of NCPE are interstitial to alveolar pulmonary opacities in the absence of signs of left-sided congestive heart failure or fluid overload such as cardiomegaly or congested pulmonary veins. Computed tomography and edema fluid analysis may aid in the diagnosis, while some forms of NCPE require additional findings to reach a diagnosis.

THERAPY

The goal of therapy for all types of NCPE is to preserve tissue oxygenation and reduce the work of breathing. This may be achieved by removing the inciting cause (eg, airway obstruction) and cage rest in mild cases and supplemental oxygen in moderate cases and may require mechanical ventilation in severe cases.

PROGNOSIS

Prognosis is generally good for most causes of veterinary NCPE except for ARDS, although data are scarce for some etiologies of NCPE.

Hydrochlorothiazide-induced systemic capillary leak

Hypersensitivity reactions to drugs may cause very rapid physiologic derangements that can be fatal in the absence of adequate compensatory mechanisms or definitive treatment. For the most part, adverse drug reactions that progress over the course of minutes are mediated either by mast cell or complement activation. If a patient survives the acute event, appropriate long-term management requires the identification and future avoidance of the inciting drug. Here, we describe a patient who experienced two life-threatening multisystem reactions with cardiopulmonary compromise minutes after taking hydrochlorothiazide (HCTZ). The reactions were associated with systemic vascular leak resulting in hypotension and non-cardiogenic pulmonary edema.

Recurrent Hydrochlorothiazide-Induced Acute Respiratory Distress Syndrome Treated With Extracorporeal Membrane Oxygenation

BACKGROUND

Hydrochlorothiazide (HCTZ) is a commonly prescribed sulfonamide thiazide-type diuretic medication that has been associated with rare cases of noncardiogenic pulmonary edema.

CASE REPORT

A man in his 50s with a medical history notable for hypertension was transferred to our institution for evaluation of refractory hypoxemia. After taking an initial dose of HCTZ earlier in the day, he developed progressive respiratory failure and was intubated at a referring hospital. Progressive hypoxemia and acute respiratory distress syndrome (ARDS) developed and he was transferred to our institution for extracorporeal membrane oxygenation (ECMO). Venovenous ECMO (vv-ECMO) was initiated in the Emergency Department and he was admitted to the intensive care unit. After several days of ECMO, his ARDS resolved and he was decannulated and extubated. Further history indicated that he had had two previous episodes of ARDS in the setting of HCTZ use without recognition of the inciting trigger, likely explaining his presentation. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: One of the most commonly prescribed antihypertensives, HCTZ is associated with rare cases of pulmonary edema, which typically develop within minutes to hours of the initial dose of the medication. Although most cases resolve with supportive care, severe cases may require intubation and even vv-ECMO. The mechanism of the reaction is unknown, and affected individuals are typically able to tolerate other sulfonamide medications without issue.