A 12-year-old spayed female domestic shorthair cat weighing 3.6 kg presented to the University of Minnesota Veterinary Medical Center (VMC) for evaluation of recurrent FISS of the right scapula. The tumor was first noted by the primary veterinarian as a 1 cm × 1 cm × 1 cm movable mass on the dorsal border of the right scapula. It was marginally removed, and histopathology revealed an incompletely excised FISS. Tumor recurrence was noted 7 months later, and the cat was referred to the VMC. Upon initial physical examination, a small (dimensions not noted), firm, movable, multilobulated subcutaneous mass immediately caudal to the right scapula was appreciated. No other abnormalities were detected. Routine preoperative bloodwork was collected and showed no abnormalities other than a moderately low platelet count (53,000/µl; reference interval [RI] 110,000–413,000). Coagulation analysis revealed a factor XII deficiency. D-dimer was 229 ng/ml (RI <250). Owing to scheduling constraints, advanced imaging was arranged for the following month. At re-presentation (19 days later), the mass was measured at 3 cm × 2 cm × 1 cm, with a second nodule and another cluster of smaller nodules detected immediately cranial to the main mass. The remainder of the physical examination was unchanged. The patient was anesthetized for CT of the neck and chest for surgical planning. The patient was premedicated with intramuscular butorphanol (0.4 mg/kg) and dexmedetomidine (3 µg/kg). Anesthesia was induced with propofol (2.5 mg/kg IV) and maintained with isoflurane in oxygen. The cat breathed spontaneously throughout the procedure and recovery was uneventful. CT revealed multiple irregularly shaped, lobulated, soft tissue-attenuating masses affecting the right latissimus dorsi muscle, right thoracic subcutaneous structures and right serratus ventralis muscle, with the largest measuring 2.7 cm × 1.8 cm × 1.3 cm (). There was no evidence of nodal or pulmonary metastasis. The initial recommendation to the client was radiation followed by surgery and chemotherapy, but this plan was declined for financial reasons. As a result, a surgery-only option was offered to the owner, with an understanding that there was a higher risk of morbidity with this approach. Re-excision of the tumor via right forequarter amputation, spinous process ostectomies (3–8) and rib resections (3–8) was scheduled to take place 4 days later. On the morning of the procedure, a platelet count was within normal limits, but a preoperative packed cell volume (PCV) revealed a new anemia of 23% and total protein of 4.8 g/dl. A complete blood count to further characterize the anemia was not performed at this time. Coinduction was performed intravenously with a combination of fentanyl (5 µg/kg), midazolam (0.2 mg/kg), ketamine (2 mg/kg) and propofol (1.5 mg/kg), and maintained with isoflurane in oxygen along with constant rate infusions of fentanyl (10–20 µg/kg/h) and ketamine (2 mg/kg/h). A right-sided brachial plexus block was performed using bupivacaine (2.5 mg) and dexmedetomidine (2.5 µg). Invasive blood pressure (IBP), pulse oximetry (SpO2) and end-tidal carbon dioxide (ETCO2) were continuously monitored. A mechanical ventilator (MV) was used for the duration of surgery. Episodes of hypotension were treated with balanced crystalloid (lactated Ringer’s solution; Hospira) and tetrastarch (VetStarch; Zoetis) boluses, dopamine and atropine. A unit each of type- and crossmatch-compatible packed red blood cells and fresh frozen plasma were sequentially administered during the procedure to treat the pre-existing anemia and proactively manage the potential for significant intraoperative blood loss. Intraoperatively, 5 cm surgical margins were outlined around the primary mass and satellite lesions, based on a combination of palpation and CT guidance (). A standard right forequarter amputation was performed with the surgical borders extending from the deep pectoralis muscles ventrally and medially to the contralateral muscles of spinous processes of vertebrae 3–8 dorsally, as well as from the right second intercostal space cranially to the right eighth intercostal space caudally, leaving the ninth rib in situ. Intercostal nerve blocks of ribs 3–8 were performed with bupivacaine. These ribs were disarticulated and removed to the level of the costochondral junction along with the associated dorsal spinous processes, thoracic wall and right forelimb en bloc (). An omental flap was prepared via a right paracostal flank approach and passed into the chest, then sutured to the body wall covering the lungs. A single layer of polypropylene mesh (Bard monofilament; Davol) was fitted to the defect and sutured to the body wall using 3-0 PDS in a horizontal mattress pattern, incorporating the omental layer (). The deep adipose and subcutaneous layers were apposed with 3-0 PDS in a simple continuous pattern. The skin was closed with 3-0 Nylon in a cruciate pattern (). A 14 G thoracostomy tube (#CT1410; MILA International) was placed using the modified Seldinger technique. The tube was suctioned until negative pressure was established. Total surgical time was approximately 4 h 30 mins. No excessive bleeding was noted during surgery. The post-transfusion, postoperative PCV was 30%, and postoperative temperature was 90.9°F (32.7°C). The cat was successfully weaned from vasopressor support 30 mins after the end of surgery. Recovery from anesthesia was prolonged, prompting partial antagonism of fentanyl with butorphanol (0.2 mg/kg IV) 2 h post-procedure. At 5 h post-procedure, the patient remained too sedated to be safely extubated, but was disconnected from the anesthesia ventilator to test respiratory ability. During spontaneous inspiration, there was a visibly asynchronous respiratory pattern with minimal expansion of the right chest wall. The cat immediately desaturated (SpO2 80%) and therefore manual assisted breathing was instituted. In an attempt to eliminate the confounding effect of drugs on recovery, an additional 4 h of assisted manual ventilation were provided, during which there was no improvement in mentation or respiratory effort. When disconnection was attempted again during transfer to the intensive care unit (ICU), the cat quickly became hypoxemic (PaO2 70 mmHg) and hypercapnic (PaCO2 88 mmHg). At that time, MV with a critical care ventilator (Respironics V200; Philips) was initiated. The patient’s temperature had increased to 97.2°F (36.2°C), but its mentation remained stuporous and the gag reflex was minimal. Initially, the ventilator mode was set to pressure-controlled, synchronized intermittent mandatory ventilation. ETCO2 normalized almost immediately. The fraction of inspired oxygen (FiO2) was decreased to 0.6 within 1 h, which was sufficient to maintain SpO2 at 98–100%. Arterial blood gas samples were collected for serial monitoring (). Ventilator settings were adjusted to maintain a PaCO2 of 35–45 mmHg and PaO2 of >90 mmHg. Additional therapies consisted of ampicillin sulbactam (30 mg/kg IV) due to the prolonged surgical time, fentanyl (1 µg/kg/h) and ketamine (1 µg/kg/min) for postoperative analgesia. The cat remained stuporous despite subtherapeutic doses of sedatives and no dosage increases were required overnight. The following morning, chest wall excursions during periods of spontaneous breathing were subjectively improved. The ventilator mode was changed to continuous positive airway pressure ventilation with pressure support prior to successful ventilator weaning. In total, the cat was mechanically ventilated for 12 h. Upon extubation, the cat was placed in an oxygen cage set to FiO2 0.6. Only a low-dose ketamine infusion (1 µg/kg/min) was maintained for analgesia. Monitoring with an electrocardiogram, IBP, SpO2 and rectal thermometer were continued. The patient was breathing well initially (PaO2 293 mmHg, PaCO2 42 mmHg, estimated FiO2 0.7) but became progressively hypercapnic (PaCO2 58 mmHg). After 6 h, given the concern for respiratory muscle fatigue, the patient was reintubated and placed back on the ventilator with similar settings as before. At this time, the cat was more alert and required additional drugs to remain intubated. Fentanyl was restarted (2 µg/kg/h) and ketamine was increased (2 µg/kg/min). Overnight, these doses were doubled to achieve an adequate plane of anesthesia. The next morning, the cat developed anisocoria, characterized by mydriasis in the left eye and miosis in the right eye. Pupillary light reflexes were intact but slow. A dazzle reflex was present bilaterally. No other cranial nerve abnormalities were noted. A drop of 1% phenylephrine was administered into the right eye to rule out Horner’s syndrome as a cause of miosis. No response was appreciated and therefore an intracranial cause of anisocoria was deemed most likely. The owner was contacted and, owing to the guarded prognosis for long-term ventilatory ability, elected for euthanasia. Necropsy revealed no apparent cause of the central nervous system signs on gross or histologic examination. Variable amounts of fibrin were found within multiple organs, including blood vessels within the cerebrum, brainstem and spinal cord. Several areas of hemorrhage were identified, including within the omental flap, subcutaneous ventral thorax, and intravenous and arterial catheter sites. The lungs contained areas of multifocal, mild alveolar congestion and edema without evidence of atelectasis. The chest wall reconstruction with mesh and omental flap were intact without evidence of complications.