Identification of Patient-Related Risk Factors for Perioperative and Postoperative Mortality in Veterinary Surgery: A ۲۵-Year Retrospective Study

Perioperative and postoperative mortality are critical indicators of surgical safety, anesthetic management quality, and overall clinical care standards in veterinary hospitals. Identifying patient-related predictors of mortality is essential for improving survival outcomes, optimizing perioperative management, and developing effective risk-reduction strategies in veterinary surgical practice. The present retrospective study evaluated a large dataset of veterinary surgical cases to determine the influence of patient-associated variables on perioperative and early postoperative mortality. A total of ۸,۶۴۲ medical records from animals that underwent surgical procedures at a veterinary teaching hospital between the years ۱۳۷۹ and ۱۴۰۴ (۲۰۰۰-۲۰۲۵) were reviewed. The study population included companion animals and large animals, consisting of ۴,۹۱۸ dogs (۵۶.۹%), ۲,۱۴۷ cats (۲۴.۸%), ۱,۱۲۶ small ruminants (۱۳.۰%), and ۴۵۱ large ruminants and other species (۵.۳%). The overall median age of the patients was ۴.۶ ± ۳.۲ years (range: ۲ months to ۱۶ years). Sex distribution included ۴,۷۳۲ males (۵۴.۸%) and ۳,۹۱۰ females (۴۵.۲%). Body condition score (BCS) was categorized on a ۱-۹ scale, with ۱۹.۷% of animals classified as underweight (BCS <۳), ۵۸.۴% as ideal (BCS ۴-۶), and ۲۱.۹% as overweight or obese (BCS ≥۷). The variables extracted from medical records included species, breed, age, sex, body condition score, physiological stability at admission, presence of comorbidities, hematological and biochemical parameters, American Society of Anesthesiologists (ASA) physical status classification, type of surgical procedure, urgency of surgery (elective vs emergency), and postoperative complications. Hematological abnormalities were recorded in ۲۸.۳% of patients, including anemia (Hb <۸ g/dL) in ۱۱.۶%, leukocytosis in ۹.۴%, and thrombocytopenia in ۴.۸%. Biochemical abnormalities such as elevated liver enzymes, renal dysfunction (creatinine >۲ mg/dL), and electrolyte imbalance were observed in ۲۲.۱% of cases. Comorbid conditions were present in ۳۱.۵% of patients, with cardiovascular disease (۹.۲%), respiratory disorders (۶.۷%), renal disease (۵.۱%), and endocrine disorders (۳.۸%) being the most frequently recorded. According to ASA classification, ۳۷.۶% of patients were categorized as ASA I, ۲۹.۴% as ASA II, ۲۰.۸% as ASA III, ۹.۳% as ASA IV, and ۲.۹% as ASA V. Elective surgeries accounted for ۶,۱۰۴ procedures (۷۰.۶%), whereas ۲,۵۳۸ surgeries (۲۹.۴%) were classified as emergency procedures. The most common surgical categories included soft tissue surgery (۴۸.۷%), orthopedic procedures (۲۷.۹%), reproductive surgeries (۱۴.۶%), and other specialized procedures (۸.۸%). Perioperative mortality, defined as death occurring during anesthesia or within the immediate perioperative period, was recorded in ۲۴۲ cases, representing an overall rate of ۲.۸%. Postoperative mortality within ۷ days of surgery occurred in ۳۵۴ cases, corresponding to a mortality rate of ۴.۱%. Species-specific mortality rates showed notable variation: dogs demonstrated a perioperative mortality of ۲.۳% and postoperative mortality of ۳.۵%, cats showed rates of ۳.۴% and ۴.۶%, respectively, while ruminants exhibited the highest mortality in emergency surgeries, with perioperative mortality reaching ۵.۸%. Multivariate logistic regression analysis identified several significant predictors of mortality. Advanced age (>۸ years) was associated with increased mortality risk (OR = ۲.۳۷, ۹۵% CI: ۱.۸۲-۳.۰۹, p < ۰.۰۰۱). Low body condition score (BCS <۳) significantly increased mortality risk (OR = ۱.۹۴, ۹۵% CI: ۱.۲۷-۲.۴۱, p = ۰.۰۰۲). Emergency surgical procedures were strongly associated with increased mortality (OR = ۳.۱۲, ۹۵% CI: ۲.۴۱-۴.۰۵, p < ۰.۰۰۱). Pre-existing cardiovascular disease also significantly increased the risk of death (OR = ۲.۸۵, ۹۵% CI: ۱.۶۵-۳.۹۴, p = ۰.۰۰۴). Severe anemia (Hb <۸ g/dL) was one of the strongest hematologic predictors of mortality (OR = ۳.۴۱, ۹۵% CI: ۲.۵۶-۴.۳۷, p < ۰.۰۰۱). Additionally, animals classified as ASA physical status III-V showed significantly higher mortality compared with ASA I-II patients (HR = ۲.۹۶, ۹۵% Cl: ۲.۱۵-۴.۰۸, p < ۰.۰۰۱). Species-specific analysis demonstrated important differences in risk patterns. Ruminants undergoing emergency abdominal surgery exhibited the highest perioperative mortality rates, largely due to metabolic disturbances and delayed referral. In contrast, cats showed a relatively higher proportion of anesthesia-related complications, particularly in cases involving cardiovascular instability and hypothermia during prolonged procedures. In conclusion, this large retrospective study demonstrates that patient-related factors play a substantial role in perioperative and early postoperative mortality in veterinary surgical patients. Advanced age, poor body condition, emergency surgical status, cardiovascular comorbidities, anemia, and higher ASA classification were identified as the most significant predictors of mortality. These findings highlight the importance of thorough preoperative assessment, optimization of physiological status prior to surgery, implementation of standardized monitoring protocols, and development of predictive risk scoring systems to improve surgical outcomes and reduce mortality in veterinary clinical practice.

کلیدواژه ها:

perioperative mortality ، postoperative mortality ، veterinary surgery ، risk factors ، anesthesia ، ASA classification ، comorbidities