Low observed perioperative complication rates associated with surgical sterilization of 1,011 heartworm-infected dogs using standard, unmodified anesthesia and surgical protocols

BACKGROUND: Shelters routinely sterilize dogs before adoption using standardized, high-volume protocols. Many also admit heartworm-positive dogs, which often experience reduced adoption appeal, longer shelter stays and higher euthanasia risk. Sterilizing these dogs before melarsomine treatment can expedite placement, but safety data on using standard, unmodified protocols remain limited. This study investigated perioperative complications in dogs with mild to moderate heartworm disease (HWD) undergoing sterilization prior to melarsomine therapy. METHODS: This was a retrospective observational study of 1,011 clinically stable shelter dogs with Class 1-2 HWD treated between 2014 and 2024. All received a standardized anesthetic protocol of dexmedetomidine, ketamine, butorphanol, and isoflurane. Surgeries were classified as routine or complex. Complications were categorized as major (life-threatening events, severe surgical problems, or aborted procedures) or minor (self-limiting issues or those requiring minimal, non-surgical intervention). RESULTS: The study included 1,011 dogs (440 females, 571 males); 92.2% underwent routine spay-neuter procedures. No perioperative deaths occurred. Twelve dogs (1.2%) experienced major complications, including three anesthetic events of unclear etiology that could not be definitively attributed to HWD, and nine surgical-site complications requiring revision. Minor complications occurred in 39 dogs (3.9%), primarily superficial incisional issues (3.6%) and transient hematuria (< 1%). Most complications were superficial surgical‑site issues commonly observed after routine sterilization, and there was no evidence of an unexpectedly high rate of cardiopulmonary events in this heartworm‑positive cohort. CONCLUSIONS: Unmodified high-volume anesthetic and surgical protocols were associated with low perioperative complication rates in a selected population of dogs with Class 1-2 HWD. Sterilizing dogs with mild to moderate HWD before adulticide therapy appears safe when using standard spay-neuter protocols and supports earlier adoption, improved shelter throughput, and efficient resource use without compromising patient safety.