Postoperative Respiratory Depression and Other Postoperative Pulmonary Complications in Veterinary Practice: A Narrative Review.

Postoperative respiratory depression (PORD) and other postoperative pulmonary complications (PPCs) represent significant contributors to perioperative morbidity and mortality in companion animal practice. The Confidential Enquiry into Perioperative Small Animal Fatalities (CEPSAF) established that cardiovascular and respiratory causes account for approximately 74% and 72% of perioperative deaths in dogs and cats, respectively, with 47% of canine and 61% of feline anesthetic-related deaths occurring in the postoperative period. PORD arises from a convergence of opioid-induced respiratory depression (OIRD), residual inhalant anesthetic effects, other drug-induced effects (e.g., neuromuscular blockade), and patient-specific vulnerabilities. PPCs encompass a broad spectrum of conditions, including atelectasis, aspiration pneumonia, pneumonia, hypoventilation, acute respiratory distress syndrome (ARDS), and respiratory arrest, with laparotomy studies reporting a PPC incidence of 22% in dogs. This narrative review synthesizes current evidence on the pathophysiology, risk factors, diagnostic approaches, prevention strategies, and treatment of PORD and PPCs in veterinary practice, incorporating insights from both veterinary-specific and translational human anesthesia literature, while explicitly identifying areas where veterinary-specific evidence remains limited. The importance of continuous monitoring during the postanesthetic period, multimodal analgesia to reduce opioid exposure, protective lung ventilation strategies, and early intervention is highlighted as a key strategy to improve outcomes, together with the unmet need for reversal-independent ("agnostic") respiratory stimulants capable of countering PORD irrespective of the causative agent.