Need for Pharmacologic Targets and Therapeutics for Postoperative Respiratory Depression and Pulmonary Complications...

Acute and delayed negative effects on the respiratory system are a common occurrence during and following veterinary surgery. Although direct mortality is relatively uncommon, pulmonary sequalae as a consequence of intraoperative analgesics and other respiratory-depressing drugs lead to immediate or delayed postoperative respiratory depression (PORD) and other postoperative pulmonary complications (PPCs) that are surprisingly commonplace.

A narrative review was conducted using PubMed, EMBASE, and other databases of peer-reviewed original research, mechanistic studies, comparative veterinary investigations, and clinical case literature published in English language.

Available data suggest a low anesthetic-related mortality. However, prospective systematically evaluated dog data demonstrate postoperative hypoxemia in a significant percentage. Mechanistic contributors include central ventilatory depression (eg, inhalational anesthetics, opioid analgesics, propofol, alfaxalone, and α₂-adrenoceptor agonists), upper airway obstruction (particularly in brachycephalic breeds), atelectasis and ventilation-perfusion mismatch, aspiration, and residual neuromuscular blockade.

Definitions of PORD and PPCs vary widely across studies, limiting consensus diagnosis and, therefore, recognition of the magnitude of the problem. Consequently, PORD and PPCs attributable to residual anesthetic, analgesic, or neuromuscular drug-induced effects after anesthesia in veterinary patients are more prevalent and serious than mortality statistics alone suggest.

To counteract the problems of analgesic and other respiratory depressants used in veterinary surgery, pharmacologically targeted mitigation strategies are needed to advance perioperative respiratory safety. The use of novel (namely inhibition of BK-channels), peripherally-acting (on the carotid bodies), "agnostic" (ie, independent of the drug cause) respiratory stimulants might represent a future therapeutic option.