Negative pressure pulmonary edema as a post-anesthetic complication associated with upper airway obstruction in a horse.

The research article discusses a case where an 8-year-old Trakehner mare experienced severe pulmonary edema, possibly due to an upper airway obstruction, following anesthesia recovery after a surgery. Efforts to establish a clear airway and implement cardiopulmonary resuscitation were unsuccessful. The presence of pulmonary edema without visible laryngeal inflammation or bleeding suggests laryngospasm or functional airway collapse could be to blame.

Case Overview

• The study revolves around an 8-year-old Trakehner mare that experienced severe pulmonary edema suspected to be due to an upper airway obstruction during recovery from anesthesia after a surgery.
• The horse was undergoing a process to repair the reinnervation of the left cricoarytenoideus dorsalis muscle and ventriculocordectomy, procedures related to improving respiratory functions.

Post-operative Complications

• About 50 minutes into the recovery from anesthesia, the mare started to show signs of a dysfunctional respiratory system, hypothesized to be an upper airway obstruction.
• Efforts to reestablish a patent airway and resuscitate the horse were unsuccessful, leading to the animal’s death.

Postmortem Findings

• A comprehensive postmortem investigation, including gross, histological, and electron microscopic examinations, found severe hemorrhagic pulmonary edema, an often fatal condition indicated by accumulation of fluid and blood in the lungs.
• Interestingly, no signs of swelling or bleeding in the larynx were detected, which poses a question about the cause of the upper airway obstruction that led to the condition.

Cause of Obstruction and Edema

• The absence of apparent physical trauma suggests that the cause might be a laryngospasm or a functional airway collapse associated with the underlying left laryngeal paralysis.
• A laryngospasm is an abrupt contraction of the vocal cords, whereas a functional airway collapse refers to a collapse in the airway due to weak cartilage or abnormal muscle function.

Negative Pressure Pulmonary Edema (NPPE)

• The incidence of negative pressure pulmonary edema as a postanesthetic complication hasn’t been widely reported in veterinary literature, making this case important in addressing this lacuna.
• NPPE usually results in horses from a strong inspiratory effort against an obstructed upper airway, generating a steep negative intrathoracic pressure that draws fluids into the pulmonary interstitial and alveolar spaces, thereby causing the edema.