FATAL VENOUS AIR EMBOLISM IN A CAT WITH A RETROPHARYNGEAL DIVERTICULUM

Incidental findings of soft tissue gas in canine and feline thoracic computed tomographic examinations

Computed tomography (CT) is a commonly used modality in small animal veterinary medicine. Anecdotally, gas bubbles are frequently identified in small animals undergoing thoracic CT examination. The aim of this retrospective observational study was to record the occurrence and prevalence of vascular and extravascular gas in routine thoracic CT examinations in dogs and cats. Patients with any clinical signs of diseases   related to soft tissue gas were excluded. A total of 84 canine studies and 90 feline studies were included, detecting gas in 66.7% of all studies, with gas more likely to be detected in canine studies (75.0%) than in feline cases (58.9%) (P = 0.009). Canine studies were more likely to have gas detected in postcontrast studies than in precontrast studies (P = 0.016). Intravascular gas was detected in 65.5% of all included studies (75% canine and 56.7% feline). Extravascular gas was detected in 13.8% of all studies (14.3% canine, 13.3% feline), with gas detected in the vertebral canal of 8.62% of all studies (canine 11.9%, feline 5.56%) and within fascial planes in 5.75% of all studies (canine 2.38%, feline 8.89%). In conclusion, gas bubbles were identified in the majority of canine and feline thoracic CT studies without clinical evidence of a pathologic etiology.

Suspected systemic gas embolism associated with lung tissue perforation caused by a previously inserted chest drain in a dog

OBJECTIVE

To report a case of systemic gas embolism associated with removal of a chest drain perforating a lung lobe in a dog undergoing sternotomy under general anesthesia and intermittent positive pressure ventilation.

CASE SUMMARY

An 8-year-old Cocker Spaniel underwent an exploratory thoracotomy via median sternotomy for surgical management of pyothorax that was treated conservatively for 7 days prior to referral following bilateral chest drain placement. The surgical procedure consisted of a subphrenic mediastinectomy and pericardiectomy. During surgery, it became apparent that the right drain was perforating the right middle lung lobe. Sudden desaturation and rapid hemodynamic deterioration occurred after the drain was removed. A systemic gas embolism was suspected on the basis of clinical signs and results of an arterial blood gas analysis, and immediate supportive treatment was started with an adequate response. Once the surgical procedure was completed, a clear "mill wheel" sound was audible on cardiac auscultation and point-of-care cardiac ultrasound confirmed the presence of gas bubbles in the cardiac chambers. The dog recovered from anesthesia and was managed in the intensive care unit where arterial blood gas analyses were nearly normal and the dog made a full recovery.

NEW OR UNIQUE INFORMATION PROVIDED

In people, there are reports of fatal air embolism related to the use of chest drains. To our knowledge, this is the first case report in dogs of a systemic gas embolism during open-chest surgery caused by a chest drain perforating a lung lobe. Immediate recognition and aggressive treatment of this life-threatening condition should be provided in order to achieve a favorable outcome.

Surgical management of a cervical esophageal diverticulum in and long-term outcome for a five-month-old cat

CASE DESCRIPTION

A 5-month-old domestic shorthair cat was presented for recurrent regurgitation and hypersalivation after eating, which had been evident since adoption 2 months earlier.

CLINICAL FINDINGS

Physical examination was unremarkable. Plain thoracic radiography, positive contrast esophagography, endoscopy, CT, electromyography, and blood analysis were performed. A caudal cervical esophageal diverticulum, likely congenital, was diagnosed.

TREATMENT AND OUTCOME

A diverticulectomy was performed with a surgical stapler while an endoscope was in the esophageal lumen. No intra- or postoperative complications were reported. Postoperative and short-term outcomes were excellent, with resolution of clinical signs and no endoscopic esophageal abnormality 3 months after surgery. The cat remained without clinical signs 8 months after surgery.

CLINICAL RELEVANCE

An esophageal diverticulum in a cat is rare. The cat of this report had a good outcome following surgical management of a cervical esophageal diverticulum. Surgery is worth considering for similarly affected cats, but additional cases are required to confirm the benefit of surgery versus conservative management.

Suspected air embolism through the thoracic ventral internal vertebral venous plexus during hemilaminectomy in dogs

Venous air embolism entering via the ventral internal vertebral venous plexus was suspected during thoracic spinal surgery in two dogs. In both cases, air was seen bubbling from a pool of blood on the floor of the vertebral canal accompanied by sudden cardiopulmonary disturbances: low end-tidal carbon dioxide pressure, tachycardia and reduction in oxygen in the blood. One dog became dyspnoeic and one died.

FORENSIC RADIOLOGY AND IMAGING FOR VETERINARY RADIOLOGISTS

Imaging studies are often of evidentiary value in medicolegal investigations involving animals and the role of the veterinary radiologist is to interpret those images for courts as an expert or opinion witness. With progressing interest in prosecuting animal crimes and strengthening of penalties for crimes against animals, the participation of veterinary radiologists in medicolegal investigations is expected to increase. Veterinary radiologists who are aware of radiographic and imaging signs that result in animal suffering, abuse, or neglect; knowledgeable in ways radiology and imaging may support cause of death determinations; conversant in postmortem imaging; comfortable discussing mechanisms and timing of blunt or sharp force and projectile trauma in imaging; and prepared to identify mimics of abuse can assist court participants in understanding imaging evidence. The goal of this commentary review is to familiarize veterinary radiologists with the forensic radiology and imaging literature and with the advantages and disadvantages of various imaging modalities utilized in forensic investigations. Another goal is to provide background information for future research studies in veterinary forensic radiology and imaging.

Perianesthetic Mortality in Domestic Animals

Autopsy of animals that die in the perianesthetic period allows identification of anesthetic and surgical complications as well as preexisting disease conditions that may have contributed to mortality. In most studies to date investigating perianesthetic mortality in animals, inclusion of autopsy data is very limited. This retrospective study evaluated autopsy findings in 221 cases of perianesthetic death submitted to a veterinary diagnostic laboratory from primary care and referral hospitals. Canine ( n = 105; 48%) and feline ( n = 90; 41%) cases predominated in the study, involving elective (71%) and emergency (19%) procedures. The clinical history provided to the pathologist was considered incomplete in 42 of 221 cases (19%), but this history was considered essential for evaluating the circumstances of perianesthetic death. Disease had been recognized clinically in 69 of 221 animals (31%). Death occurred in the premedication or sedation ( n = 19; 9%), induction ( n = 22; 11%), or maintenance ( n = 73; 35%) phases or in the 24 hours postanesthesia ( n = 93 animals; 45%). Lesions indicative of significant natural disease were present in 130 of 221 animals (59%), mainly involving the heart, upper respiratory tract, or lungs. Surgical or anesthesia-associated complications were identified in 10 of 221 cases (5%). No lesions were evident in 80 of 221 animals (36%), the majority of which were young, healthy, and undergoing elective surgical procedures. Lesions resulting from cardiopulmonary resuscitation were identified in 75 of 221 animals (34%). Investigation of perianesthetic death cases should be done with knowledge of prior clinical findings and antemortem surgical and medical procedures; the autopsy should particularly focus on the cardiovascular and respiratory system, including techniques to identify pneumothorax and venous air embolism.

Fatal venous air embolism during anesthesia in an apparently healthy adult Chihuahua

An apparently healthy adult female Chihuahua was presented for elective ovariohysterectomy. After induction of general anesthesia, but prior to the start of the surgery, air was inadvertently administered to the patient via the i.v. fluid line. The patient convulsed, became apneic, arrested, and died despite attempted cardiopulmonary resuscitation. At necropsy, the pericardial sac was incised and filled with water to entirely submerge the intact heart. The right ventricular free wall was punctured, releasing several air bubbles from the right ventricle. Death was attributed to venous air embolism based on the clinical history, gross findings, and paucity of underlying gross and microscopic pathology that might have predisposed the dog to an anesthetic-related death. The discussion of this case includes a review of previously reported veterinary cases of fatal venous air embolism, including the varied mechanisms of embolus formation, the potential impact of pre-existing cardiopulmonary disease, and the methods used to detect emboli. This report outlines the events of fatal iatrogenic venous air embolization and emphasizes the importance of considering this entity in the case of sudden death of a patient with an indwelling catheter in order to pursue either appropriate diagnostic tests or necropsy techniques to aid in the diagnosis.

Venous air embolism detected on computed tomography of small animals

OBJECTIVE

To describe the prevalence, location and clinical significance of abnormal gas accumulations in dogs and cats detected on computerised tomography images.

METHODS

Retrospective evaluation of all canine and feline computed tomography examinations (292 pre-contrast and 219 post-contrast) performed in a 12-month time period. All studies were evaluated for the presence of venous air emboli. The location of intravenous gas was noted and the volume of intravenous air emboli was estimated visually. The medical records of animals with venous air embolism were reviewed for signs of cardiopulmonary complications.

RESULTS

The overall prevalence of air embolism on pre- and incidence on post-contrast images was 4 · 5 and 2 · 3%, respectively. The prevalence of air embolism on pre-contrast and incidence on post-contrast thoracic images was 35 · 7 and 14 · 2%, respectively. The volume of venous air was generally small and the most common was in an axillary vein. None of the animals had any cardiopulmonary complications.

CLINICAL SIGNIFICANCE

The presence of small volume venous air embolism on routine computed tomography examinations is a frequent incidental finding that does not appear to cause cardiopulmonary complications.

Full recovery after cardiac arrest secondary to accidental iatrogenic venous air embolism in a cat

OBJECTIVE

To describe the successful management of cardiac arrest following accidental venous air embolism (VAE) in a cat.

CASE SUMMARY

A 3-year-old spayed female domestic shorthair cat, weighing 4 kg, was presented for continuation of its chemotherapy protocol. The cat was inadvertently administered approximately 5.5 mL of air IV during initiation of fluid therapy. Immediate cardiac arrest resulted and CPR successfully achieved return of spontaneous circulation. The cat was discharged 5 days later and is reportedly clinically normal 7 months post-discharge.

NEW OR UNIQUE INFORMATION PROVIDED

VAE has been rarely reported in the veterinary literature. This is the first report of a cat surviving cardiac arrest secondary to VAE.

Esophageal Diverticulum Associated With a Trichobezoar in a Cat

A 9-year-old, castrated male, domestic longhaired cat was evaluated for persistent regurgitation over the previous month. The cat had presented 9 months earlier and was diagnosed with esophageal obstruction secondary to a trichobezoar. The trichobezoar had been removed endoscopically, and the cat was subsequently fed a canned prescription diet. The owners noted only infrequent regurgitation over the following 9 months. After signs recurred, contrast radiography with fluoroscopy revealed an esophageal diverticulum at the thoracic inlet, with an ovoid filling defect. Decreased esophageal motility was noted distal to the diverticulum. Esophagoscopy confirmed the presence of a trichobezoar within an esophageal diverticulum. Following removal of the trichobezoar and therapy to prevent trichobezoar formation, the cat did well for 2 months until it died suddenly with signs of hyperventilation and open-mouth breathing.

Fatal venous air embolism in a cat undergoing dental extractions

A five-year-old domestic shorthair cat underwent general anaesthesia and tooth extractions. Immediately after use of a high-speed, air-driven, water-cooled dental drill, the cat suffered cardiac arrest and attempted resuscitation was unsuccessful. Post-mortem radiographs showed air in the vena cava, right atrium, right auricle and right ventricle, hepatic and renal veins. These findings were confirmed at post-mortem examination. The cause of death was massive air embolism. There are reports of fatal venous air embolism in the human literature from the use of high-speed, air-driven, water-cooled dental drills. In this case, we believe that the air jet from the cooling system provided an enormous pressure gradient allowing air entry through an alveolar bone fracture or the inflamed gingival tissues. This is the first report of fatal venous air embolism associated with the use of a high-speed dental drill in the veterinary literature.