Iatrogenic gas embolism in a juvenile loggerhead sea turtle (Caretta caretta)

A mild pneumocoelom was diagnosed by computed tomography in a stranded juvenile loggerhead sea turtle (Caretta caretta). After gas extraction by ultrasound-guided puncture, the animal did not improve and was subjected to hyperbaric oxygen therapy (HBOT). After HBOT, the turtle developed marked subcutaneous emphysema and was found dead the following morning. Gross lesions included a distended right atrium with numerous gas bubbles within the epicardium, gas bubbles in the hepatic, gastric and mesenteric veins, a small gas-filled bulla in the left lung and diffuse haemorrhages in the encephalon. Histological lesions included gas-like emboli in the lumen of the right atrium with myocardial necrosis, gas-like emboli in the lumina of intestinal, pulmonary and renal blood vessels and severe meningeal haemorrhages. From a forensic pathology perspective, the subcutaneous emphysema of immediate onset after HBOT and the greater severity of the histological lesions in blood vessels, heart, lung and brain differentiate this case from other cases of gas embolism in turtles due to incidental capture. Two factors contributed to this outcome: the existence of a probably unresolved pneumocoelom and the application of HBOT without an initial diagnosis that accurately indicated its use. Therefore, as in human medicine, the use of HBOT in sea turtles with lung lesions and pneumocoelom is discouraged. This is the first description of an iatrogenic gas embolism in a sea turtle.

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.

Gas embolism and massive blunt force trauma to sea turtles entrained in hopper dredges in North and South Carolina, USA

Decompression sickness (DCS) has been described mainly in loggerhead turtles Caretta caretta bycaught in trawls and gillnets. Here we present cases of gas emboli (GE) in 8 green turtles Chelonia mydas and 2 Kemp's ridleys Lepidochelys kempii entrained in hopper dredges that were working at 8.8-15.2 m depths during shipping channel maintenance or beach renourishment activities. Turtle weights ranged from 2.2 to 6.7 kg. All were found alive with blunt force injuries from passage through the dredge and were taken to rehabilitation facilities. Four green turtles died or were euthanized within 24 h. Six turtles survived. Radiographic or ultrasonographic evidence of GE was detected in 4 turtles, including 3 mortalities. Computed tomography (CT) revealed perirenal and cervical GE in 4 turtles, including 1 mortality. No GE were detected in 2 of the survivors. Upon necropsy, GE were found in mesenteric vessels, the right atrium, and kidneys. Histopathology confirmed that tissues were in a good state of preservation without evidence of bacterial overgrowth or putrefactive gas formation. Death likely resulted primarily from massive tissue trauma from the dredge, but moderate GE could have led to DCS and complicated recovery. The surviving turtles weighed less than those that did not survive. Besides hypothesized stress/exercise-induced circulatory changes of blood through the lungs and pressure reduction of forced surfacing from depth, drastic pressure change within the dredge pipes before and after the pump could contribute to GE. Hopper dredge entrainment is an additional cause of GE and potential DCS in sea turtles.

Acute and Chronic Outcomes of Gas-Bubble Disease in a Colony of African Clawed Frogs (Xenopus laevis)

Gas-bubble disease occurs in aquatic species that are exposed to water that is supersaturated with gases. In February 2007, municipal water supersaturated with gas was inadvertently pumped into the vivarium's aquatic housing systems and affected approximately 450 adult female Xenopus laevis. The inflow of supersaturated water was stopped immediately, the holding tanks aggressively aerated, and all experimental manipulations and feeding ceased. Within the first 6 h after the event, morbidity approached 90%, and mortality reached 3.5%. Acutely affected frogs showed clinical signs of gas-bubble disease: buoyancy problems, micro- and macroscopic bubbles in the foot webbing, hyperemia in foot webbing and leg skin, and loss of the mucous slime coat. All of the frogs that died or were euthanized had areas of mesenteric infarction, which resulted in intestinal epithelial necrosis and degeneration of the muscular tunic. Over the subsequent 2 wk, as gas saturation levels returned to normal, the clinical symptoms resolved completely in the remaining frogs. However, 3 mo later, 85% of them failed to lay eggs or produce oocytes, and the remaining 15% produced oocytes of low number and poor quality, yielding cytosolic extracts with poor to no enzymatic activity. Histology of the egg mass from a single 2- to 3-y-old frog at 3 mo after disease resolution revealed irregularly shaped oocytes, few large mature oocytes, and numerous small, degenerating oocytes. At 6 mo after the incident, the remaining frogs continued to fail to produce eggs of sufficient quantity or quality after hormonal priming. The researchers consequently opted to cull the remainder of the colony and repopulate with new frogs.

Portomesenteric venous gas in a 2-week-old Holstein calf

A 2-week-old Holstein Friesian female calf was presented with profuse diarrhea and abdominal distension. Clinicopathological findings included marked hypoproteinemia, hypoglycemia and leucopenia, mild hyperlactatemia, and hyperfibrinogenemia. On abdominal ultrasonography, features were consistent with portomesenteric venous gas (PVG), a rare condition reported in the medical literature. The PVG in this calf was associated with severe gastrointestinal illness and sepsis.

Pathology of ocular lesions associated with gas supersaturation in white seabass

Cultured juvenile white seabass Atractoscion nobilis (WSB) can suffer from intraocular emphysemas and exophthalmia in the hatchery environment. To identify the cause, two size-groups of WSB were exposed to five gas saturation levels, ranging from 98% to 122% total gas pressure (TGP), over a 96-h exposure period in 18 degrees C and 23 degrees C seawater. Histological examination revealed that the gross and subgross lesions associated with gas supersaturation included corneal and orbital emphysema, along with subretinal, optic nerve, and iridial hemorrhage. Corneal emphysema was the most prominent gross lesion, with the severity and prevalence increasing between size-groups and water temperatures as TGP increased. Following the same pattern was orbital emphysema, which affected more than 93% of the fish examined and caused hemorrhage in the subretinal space, around the optic nerve, in the iris, or a combination thereof. Iridial hemorrhage occurred in 91% of the fish examined and decreased significantly with fish size. The prevalence and severity of hemorrhage in the subretinal space increased significantly with TGP and fish size but not with temperature. Optic nerve hemorrhage was absent in small fish exposed at 18 degrees C but increased significantly with temperature and fish size. The reverse was true for the large fish.

Carbonic anhydrase activities from the rainbow trout lens correspond to the development of acute gas bubble disease

Dissolved gas supersaturation is hazardous to fish and can result in gas bubble disease (GBD). Signs of GBD typically include bubbles in the eyes, fins, skin, lateral line, and gill filaments. Ocular abnormalities in diseased salmonids typically occur after aberrant gas production in the eyes. In this study, freshwater rainbow trout Oncorhynchus mykiss were exposed experimentally to percent total gas pressure (TGP%) levels of 104% (control) and 115%. No mortalities occurred during the 7-d experimental period. Effects of GBD were observed externally as a darkened skin, exophthalmia, localized hemorrhage in the eye, and gas bubbles on the operculum. Additional signs included increased swimming activity and, more frequently, panic episodes. Carbonic anhydrase (CA) enzyme activities from the lens and retina were determined at days 0, 1, 3, 5, and 7 of the study. Venous blood gases were also measured on day 7. Retinal pH did not differ between normal and affected fish, but blood characteristics such as the partial pressure of O2, partial pressure of CO2, carboxyhemoglobin level, and bicarbonate ion concentration were significantly elevated in affected fish relative to normal fish. Venous blood pH and oxyhemoglobin levels were not significantly different between affected and normal fish. Patterns of response to total dissolved gas levels differed between the lens and the retina. Mean CA activities in the lenses of fish exposed to a TGP% level of 115% were significantly below those of control fish. However, retinal CA activities did not significantly differ between the two groups over the course of the experiment. These findings show that dissolved gas supersaturation reduces CA activity in the rainbow trout lens.

Suspected air embolism associated with post-anesthetic pulmonary edema and neurologic sequelae in a horse

A 523 kg Quarter Horse was anesthetized for unilateral eye enucleation. The anesthetic period was unremarkable. During anesthetic recovery the cap on the jugular venous catheter became dislodged. Clinical signs of pulmonary edema associated with moderate arterial hypoxemia subsequently developed. Although pulmonary edema resolved with medical therapy, the day following anesthetic recovery, clinical signs of vestibular disease and blindness developed. Treatment included nasal oxygen insufflation, flunixin meglumine, furosemide, dexamethasone, thiamine, dimethylsulfoxide, antimicrobials, and phenylbutazone. The horse recovered and was discharged from the hospital after 7 days of treatment and was neurologically normal at 6 weeks. While venous air embolism was not confirmed in this case, the catheter cap complication followed by signs of pulmonary edema and neurologic sequelae support the presumptive pathogenesis of this horse's complications. Diagnostic confirmation of air embolism in horses with compatible acute clinical signs should be documented with echocardiography.

A case of spontaneous venous embolism with carbon dioxide during laparoscopic surgery in a pig

BACKGROUND

Carbon dioxide (CO2) embolism is a possible complication of capnoperitoneum during laparoscopic surgery. Experimentally induced venous CO2 embolism has been studied in pigs. In this paper we report a case of spontaneous CO2 embolism.

OBSERVATIONS

A 4-month-old Large White pig weighing 20 kg underwent experimental laparoscopic surgery under general anaesthesia. Monitoring consisted of pulse oximetry, capnography, airway pressure, electrocardiography, invasive arterial and central venous blood pressures, and arterial blood-gas analysis. Shortly after the start of laparoscopy and onset of CO2 insufflation, sudden decreases in end-tidal CO2 (Pe'CO2), haemoglobin saturation of oxygen (SpO2), systolic arterial blood pressure and heart rate were observed. Airway pressure increased and pulmonary compliance decreased simultaneously. Insufflation was immediately discontinued and epinephrine (2 mg IV), atropine (0.5 mg IV) and a 50 mL bolus of a polygeline solution were administered without effect. At this time arterial blood-gas analysis revealed a pH of 7.29 and a PaCO2 of 6.8 kPa (51.2 mmHg); PaO2 was 26.6 kPa (199.5 mmHg). After 4 minutes asystole occurred.

CONCLUSIONS

The sudden decrease of Pe'CO2 and lung compliance combined with the sudden decrease in systolic blood pressure, heart rate and a poor response to resuscitation suggest a case of fatal gaseous venous embolism.

FATAL VENOUS AIR EMBOLISM IN A CAT WITH A RETROPHARYNGEAL DIVERTICULUM

A cat with a 1-year history of oropharyngeal foreign bodies was diagnosed with a pharyngeal diverticulum. The cat experienced fatal cardiac arrest during endoscopy, and postmortem radiographs and ultrasound revealed venous air embolism. Venous air embolism is uncommonly reported in veterinary medicine, but is a risk during any procedure that introduces air into a body cavity. Precautions should be taken during these procedures to help minimize the risk of adverse events.

Suspected fatal venous air embolism during anaesthesia in a Pomeranian dog with pulmonary calcification

CASE HISTORY

Death occurred in a 1.25 kg, 9-month-old female Pomeranian dog undergoing anaesthesia for surgical repair of partially healed fractures of the radius and ulna.

CLINICAL FINDINGS

Following sedation, anaesthesia was induced using thiopentone and maintained with halothane in oxygen. An acute decrease in the dog's end-tidal carbon dioxide (EtCO2) measurements was noted approximately 50 min after induction, immediately following delivery of a 5-ml bolus of lactated Ringer's solution (LRS) administered to flush a small (0.06 ml) volume of fentanyl via a pre-placed intravenous (I/V) catheter. Venous air embolism (VAE) was suspected and the dog died despite interventive therapy. On post-mortem examination, several air bubbles were noted when the right ventricle was opened under water. Histologically, the kidneys appeared abnormal with immature glomeruli, and the lungs appeared diffusely mineralised. The origin of the air was probably small bubbles and microbubbles that may have been present in the extension set and 20 ml syringe used for the administration of fentanyl and I/V fluids to the dog.

DIAGNOSIS

Renal dysplasia and diffuse pulmonary calcification, with VAE as the probable cause of death.

CLINICAL RELEVANCE

In this case of VAE-associated anaesthetic death, it is further speculated that underlying pulmonary disease, in the form of pulmonary calcification, may have contributed to an increased sensitivity to the adverse effects of VAE.

Suspected venous air embolism in a horse

A horse which had had a caecal impaction for 10 days was treated by means of an ileocolostomy [corrected] but failed to respond satisfactorily. Before a second laparotomy was performed it was observed to have dislodged the extension set from a jugular catheter and air was heard being sucked into the vein. It became very agitated but was anaesthetised again and the impaction was removed through an incision in the apex of the colon [corrected] After recovering from the anaesthesia it developed severe signs of pruritus which subsided only after 12 hours. These signs were considered most likely to have resulted from a venous air embolism.

Clinical and pathological observations on Streptococcus sp. infection on South African trout farms with gas supersaturated water supplies

Infection with a faecal Streptococcus species belonging to Lancefield group D has been a major cause of mortalities on certain trout farms on the escarpment of the Mpumalanga Province in the Republic of South Africa. Evidence is given of a connection between subclinical gas bubble disease and infection with this organism in rainbow trout, Oncorhynchus mykiss. The condition causes serious losses during the summer months when water temperatures rise above 18 degrees C. The larger table-size fish are affected first and present with exophthalmos before developing signs of a typical bacterial septicaemia. The design of the water supply to the fish ponds on these farms allowed supersaturation of the water with atmospheric gas. Vortex formation at water extraction points appears to have been the main cause of air entrainment into the water supply leading to the ponds. By correcting the faults responsible for the development of hyperbaric gas pressure in the water, it was possible to control this disease on two badly affected farms. The overlapping similarities in the clinical signs and pathology of gas bubble disease and that seen in fish suffering from Streptococcus D infection are discussed, as well as the diagnostically significant changes in the gill tissues that are specific to subclinical exposure to gas supersaturation in the water. An explanation is given for the increased susceptibility to infection with this organism.

Gas bubble disease in farmed fish in Saudi Arabia

Four outbreaks of gas bubble disease were encountered among farmed fish in Saudi Arabia. Two of them occurred among subadult (52.5 g) saltwater tilapia (Oreochromis spilurus), the first affecting about 50 per cent of the stock and resulting in about 30 per cent mortality, and the second affecting about 25 per cent of the population with about 5 per cent mortality. Another outbreak occurred among adult (270 g) brackish water (0.5 per cent salinity) tilapia (Oreochromis niloticus), affecting about 40 per cent of the population with about 25 per cent mortality. The fourth outbreak occurred among three-month-old (15 g) grouper (Epinephelus fuscogutiatus) and resulted in 10 per cent mortality. In all cases the total water gas pressure ranged between 111.2 and 113.4 per cent saturation and nitrogen was supersaturated while oxygen was undersaturated. The outbreaks were alleviated by reducing the gas pressure by splashing the source water or by switching to a source of water with lower gas pressure. However, in O niloticus the conditions of gas supersaturation resulted in a heavy infection by monogenetic trematodes which was treated with formalin at 40 mg/litre for seven hours on five successive days.

[Gas bubble disease of fish]

Gas bubble disease (GBD), a non-infectious, environmentally/physically induced trauma, is caused by an increase in the dissolved gas pressure above the ambient air pressure (supersaturation). Frequently the cause is an increased partial pressure of nitrogen-especially in spring-/groundwater. All fish species as well as amphibians and aquatic invertebrates are susceptible. Fish species and age groups are different sensitive; swim up fry is very endangered. The disease may occur in a chronic form at approximately 103% and in an acute form at above 110/115% total gas pressure (TGP). Fish, especially fry, with the chronic form die slowly without symptoms. The clinical symptoms of the acute form are disorientation, subcutaneous emphysema, embolism, exophthalmus mostly only on one side, swimming near the water surface with darkened skin, haemorrhages and high mortality. Losses increase with increased TGP. Generally, mortality in the chronic form increases by secondary infections of emphysematous tissue. As technical processes may be the cause for an increased total gas pressure, such as water pumping, heating water or mixing cold with warm water, in this context we could speak from a "technopathy". The following "therapeutic" measurement is recommended: avoid causal factors, transfer damaged fish in expanded water, turn off the cause, compensate the pressure in deeper water, if possible.

Preliminary findings of ophthalmological abnormalities in farmed halibut

Ocular abnormalities occurring in farmed halibut at the Sea Fish Industry Authority Marine Farming Unit, Ardtoe, Argyll were investigated clinically and post mortem. A significant number of fish were found to have posterior polar cystic changes either causing scleral ectasia or gross degenerative posterior segment abnormalities with chorioretinal atrophy. Other ocular abnormalities included cataract formation and intraocular inflammation. In a small number of fish gas bubble formation in the anterior chamber was observed during capture and examination. It is possible that the lesions seen in these fish are a form of gas bubble disease although super-saturation, the cause of gas bubble disease previously reported in farmed fish, does not occur in the tanks in which these fish are housed. While this paper provides no answers with regard to the aetiopathogenesis of the lesions, it is hoped that it will stimulate discussion, leading to resolution of these questions through a multidisciplinary approach to the problem.

Histopathology and ultrastructure of ocular lesions associated with gas bubble disease in salmonids

Ocular lesions associated with natural and experimental outbreaks of gas bubble disease (GBD) in commercial salmonids were assessed histologically and by scanning electron microscopy. Small gas emboli were first detected in the choroid gland of the posterior uvea. In subacute and chronic cases, bubble size increased markedly and localization in retrobulbar and periocular sites was favoured. During the acute phase of GBD, ocular lesions were limited to anatomical displacement of tissue and local degeneration of compressed tissues around the perimeter of bubbles. Subacute sequelae included the formation of anterior synechia, lens cataract, and suppurative panophthalmitis. During chronic stages, when large retrobulbar bubbles had caused severe exophthalmia, there was stretching of the optic nerve and of retinal blood vessels and severe distortion of the posterior aspects of the globe. The sequential development, pathogenesis and persistence of ocular lesions associated with GBD in fish are discussed.

Granulocyte depletion attenuates sustained pulmonary hypertension and increased pulmonary vasoreactivity caused by continuous air embolization in sheep

Chronic pulmonary hypertension can develop in diseases associated with acute or repeated inflammation in the lungs, e.g., adult respiratory distress syndrome, chronic bronchitis. Inflammation has also been associated with some animal models of chronic pulmonary hypertension. We have previously shown that 12 days of continuous air embolization into sheep results in the functional and structural changes of chronic pulmonary hypertension. To determine whether granulocytes contribute to these changes, five sheep were granulocyte-depleted with hydroxyurea immediately before and during air embolization (AIR-PMN) and were compared with sheep receiving air embolization (AIR only). Air embolization was discontinued briefly every 4 days for monitoring of pulmonary vascular pressures and assessment of pulmonary vasoreactivity to a bolus injection of PGH2-A. After 12 days of air embolization, the lungs were removed for structural studies. AIR-PMN sheep did not develop the sustained increase in pulmonary artery pressure seen in the AIR sheep (Day 12, AIR-PMN = 20 +/- 3 cm H2O; AIR = 29 +/- 2; mean +/- SE). Similarly, the increased pulmonary pressor response to PGH2-A seen in AIR sheep was not found in the AIR-PMN group. Structural studies of the barium-injected lungs of AIR-PMN sheep revealed a twofold increase in medial thickness of normally muscular arteries and a significant increase in the percent of muscular intraacinar arteries (similar to findings in lungs from AIR sheep). The number of barium-filled arteries was increased in AIR-PMN sheep when compared with that in AIR sheep, but the number was still less than in the control sheep. We conclude that granulocytes may contribute to the functional changes of chronic pulmonary hypertension after continuous air embolization in sheep, but they do not play a role in structural changes involving pulmonary arterial smooth muscle cells and their precursors. The present data also suggest that the reduction in peripheral arterial filling is the structural alteration that contributes most to the sustained rise in pulmonary artery pressure. The data further suggest that pulmonary hypertension after air embolization may have a vasoconstrictive component that is granulocyte-dependent.

Fatal air embolism during anesthesia for laparoscopy in a dog

A 13-year-old dog went into cardiopulmonary arrest after insufflation of the abdominal cavity with nitrogen for laparoscopy. Resuscitation was unsuccessful. Necropsy findings included a punctured spleen and confirmed the development of air embolism.