Influence of Comprehensive Pre-Anaesthetic Assessment on ASA Classification and Surgical Cancellations in Dogs and Cats: A Retrospective Observational Study

Anaesthesia carries an inherent risk of morbidity and mortality in veterinary patients, yet the clinical impact of comprehensive pre-anaesthetic assessment (PAA) is insufficiently quantified. We retrospectively reviewed 350 PAAs including 267 dogs and 83 cats, performed at a small-animal teaching hospital in 2021. Signalment, history, physical examination findings, complementary diagnostics, initial ASA physical status (ASA-i), final ASA status after test review (ASA-f) and procedural outcomes were recorded. Complementary diagnostics-predominantly haematology, serum biochemistry, thoracic radiography, and electrocardiography-were requested in 82-86% of cases. ASA-f differed from ASA-i in 7.5% (11/306) of animals: +1 in 3.6%, +2 in 1.0%, -1 in 2.9%; no patient shifted by more than two classes. Fifty-seven planned procedures (16.2%) were cancelled following PAAs, chiefly abdominal (43.9%) and minor soft-tissue surgeries (31.6%). Internal-medicine abnormalities (47%) and cardiac findings (19%) were the leading causes; in 46% of cancellations, the trigger was an abnormal test result absent from the physical examination. Sixty-three percent of cancelled interventions were later completed after further evaluation or treatment. These data demonstrate that structured PAA substantially alters perioperative decision-making in small-animal practice and supports selective yet rigorous diagnostic test use to enhance patient safety and optimise theatre utilisation.