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Case Report: n-butyl-2-cyanoacrylate Pleurodesis to manage Intractable, Spontaneous Pneumothorax in a Labrador Retriever

History

fig.2 - R lateral radiograph: note elevation of the cardiac silhouette

fig.1 – DV radiograph of chest showing bilateral pneumothorax

A three-year-old, entire, female Labrador Retriever presented to the referring veterinarian for assessment of progressive orthopnoea with associated vomiting over several months.  There had been no history of trauma or access to toxins.  Investigations by the referring vet including radiology and thoracocentesis, revealed bilateral pneumothorax. 

On examination, the patient exhibited a mild increase in  respiratory effort, with an elevated rate of 40 breaths per minute.  She became distressed in lateral recumbency.  This was relieved on exsufflation of two litres of air (total) from both sides of the chest.

 

Investigations

Haematology, biochemistry, bronchoscopy and abdominal ultrasound revealed no abnormalities.  Thoracic radiology (post-drainage, figs. 1 & 2) revealed mild bilateral pneumothorax but there was no evidence of underlying parenchymal lung disease. Given the chronicity of the clinical signs it was decided to perform elective, exploratory  thoracotomy.

 

Results

fig. 3 - intraoperative photo showing blebs on the ventral surface of the middle lung lobe.

A median sternotomy was performed to facilitate thorough inspection of the entire pleural cavity.  Perioperative potentiated amoxicillin and lignocaine/ ketamine constant rate infusions were administered along with opiate, NSAIDs and bupivacaine intercostal blocks as part of a multimodal analgesic regime.  Both sides of the chest were sequentially flooded with sterile saline before positive pressure ventilation so as to identify any air leaks; this revealed small bubbles of air escaping from the hilar region of the right  middle lung lobe.  Closer inspection of this lobe revealed a series of small blebs along the ventral surface, adjacent to the primary bronchus (see fig. 3 – click to enlarge).  No other pathology was noted.

The affected lobe was removed using a thoraco-abdominal stapling device.  The pleural cavity was re-flooded to check for further leaks.  All resected lung tissue was submitted for histopathology, which revealed evidence of mild pleural fibrosis, but no other pathology.  A thoracostomy tube was placed at the right, 10th intercostal space to provide for postoperative drainage.  The sternum was closed with wire mattress sutures and the remainder of the wound was closed in layers. 

 

Aftercare

fig. 4 - lateral view of chest showing pleural effusion with pneumothorax.

Intermittent suction of the chest drain was performed every 30 minutes throughout the recovery period.  Initially, small amounts of fluid were produced but a significant volume of air was noted after approximately three hours. 

A continuous thoracic drainage unit was connected to the chest drain in an attempt to create a fibrin seal.  However, air continued to enter the pleural space over the following 48 hours.  At this point the thoracotomy was repeated as a ‘second look’ procedure.  The pleural cavity was re-flooded with saline to check for on-going air leaks; no further leaks were found.  The thoracostomy tube was replaced with a new set in the contralateral chest wall and the sternotomy was closed again as above.

Intermittent suction of the second chest drain was non-productive and the drain was removed three days later.  Signs of increased respiratory effort were noted 24 hours later and further air was drawn off both sides of the chest. 

Five days post revision surgery a profuse, serosanguinous discharge was noted from the surgical wound but the respiratory rate was not elevated.  Repeat radiology (fig. 4) revealed a pleural effusion as well as persistent pneumothorax. 

Analysis of pleural fluid aspirate was consistent with septic pleurisy.  Bacteriology revealed a profuse growth of E.coli, resistant to potentiated amoxicillin.  A course of enrofloxacin was given and the pleural effusion gradually reduced over the following few days; repeat bacteriology of aspirates four days later yielded no bacterial growth.  However, air continued to be drawn off both sides of the chest at a rate of approximately 500mls every three days.   Intermittent thoracocentesis was continued every 3-5 days over the following two weeks.  This produced decreasing amounts of fluid which on repeat bacteriology, proved sterile on each occasion.  Air leakage remained constant for a total of more than three weeks after initial presentation.

 

Pleurodesis

 

fig. 5 - schematic representation of pleurodesis procedure.

General anaesthesia was induced prior to placement of a thoracostomy tube (connected to a suction unit) and separate 22G 38mm spinal needle in the right thoracic wall (see fig. 5 – click to enlarge). 

Room air was allowed into the right side of the chest to partially collapse the right lung.  3mls of sterile, n-butyl-2-cyanoacrylate adhesive (Vetbond 3M) were then rapidly instilled through the spinal needle, whilst re-directing the needle so as to distribute the adhesive throughout the right hemithorax.  The needle was then immediately removed.  All air within the chest was evacuated via the thoracostomy tube over the following few seconds and the thoracostomy set was also withdrawn without further delay.  The patient made an unremarkable recovery from anaesthesia. Mild, right-sided subcutaneous emphysema was noted over the chest wall a few hours after the procedure but this resolved after application of a supportive dressing. 

fig. 6 - 24h post right-sided pleurodesis. A left-sided pneumothorax is still evident.

The following day,  further radiology (fig. 6) revealed little free air within the right side of the pleural cavity.

One week later, repeat aspirates from both sides of the chest revealed moderate amounts of air and a small amount of pleural fluid.  Cytology of this fluid was consistent with suppurative inflammation (non-degenerate neutrophils), but no organisms were identified and bacteriology again yielded no growth. 

Pleurodesis was repeated on the contralateral side of the chest with a similar volume of n-butyl-2-cyanoacrylate.  On recovery, the patient exhibited mild signs of discomfort but these responded to opiate analgesia within 12 hours.  No further subcutaneous emphysema was observed.

Repeat radiology after a further week revealed minimal amounts of air within the pleural space (figs. 7 & 8). 

The patient has  remained free of signs over the six months since pleurodesis.

 

Discussion

fig. 7 – right lateral radiograph one week after second pleurodesis. There is lung tissue visible throughout the lung fields with only a small amount of pleural air cranially and mild effusion ventrally.fig. 7 - DV radiograph one week after second pleurodesis. There is lung tissue visible throughout both sides of the chest.fig. 7 - DV radiograph one week after second pleurodesis. There is lung tissue visible throughout both sides of the chest.fig. 7 - DV radiograph one week after second pleurodesis. There is lung tissue visible throughout both sides of the chest.fig. 7 - DV radiograph one week after second pleurodesis. There is lung tissue visible throughout both sides of the chest.

Spontaneous (atraumatic) pneumothorax is a rare and sometimes challenging presentation.  It frequently involves the formation of bullae and/ or blebs within the lung parenchyma.  These are often not visible on plain radiography.  CT has been

proposed as a more sensitive imaging method1.  The underlying aetiology is not known but breed predilection (e.g. Huskies) suggest a genetic component.  Less common causes of spontaneous pneumothorax would also include underlying neoplasia, pulmonary cysts/ emboli, pleural adhesions, parasites (e.g. Heartworm) or ruptured abscesses and in cats, severe asthma. 

Immediate treatment should focus on improving ventilation by aspiration of both sides of the chest before definitive assessment is undertaken.

The condition carries a favourable prognosis provided primary lung pathology is non-progressive, limited in distribution and successfully excised in its entirety.  However,  cases are infrequently reported where no such pathology is found, or the pleural space continues to fill with air despite appropriate management (more than five days of continuous or intermittent suction).  Comparative pathology is seen in humans and is usually managed following unsuccessful drainage, by pleurodesis or lung transplant. 

In the case described here, both continuous and intermittent negative pressure failed to resolve the air leak(s) over a period greater than three weeks, despite the initial presence of significant fibrin production secondary to infection.  Consideration was therefore given to obliteration of the pleural space by means of pleurodesis.

Effective pleurodesis in dogs is difficult to achieve due to the fibrinolytic tendencies of the pleural mesothelium.  A variety of methods have been tried, with mechanical abrasion at the time of thoracotomy, introduction of talc slurries, tetracyclines/ other antimicrobials, silver nitrate, iodine compounds and blood, which have met with variable morbidity and success2,3

n-butyl-2-cyanoacrylate is a well-known tissue adhesive licensed for closure of superficial wounds. Its use as a pleural adhesive was considered in this case by virtue of its ability to bond moist surfaces in seconds with minimal tissue reaction. 

The above case describes a low morbidity, relatively simple and inexpensive technique for long-term resolution of intractable, spontaneous pneumothorax.

 

fig. 8 - DV radiograph one week after second pleurodesis. There is lung tissue visible throughout both sides of the chest.

References

1. Au JJ et al. The use of computed tomography for evaluation of lung lesions associated with spontaneous pneumothorax in dogs: 12 cases (1999-2002) JAVMA March 2006;288(5):733-7

2. Merbl Y et al. Resolution of persistent pneumothorax by use of blood pleurodesis in a dog after surgical correction of  a diaphragmatic hernia. JAVMA August 2010; 237(3):299-303

3. Athanassiadi K et al. Autologous blood pleurodesis for persistent air leak. Thorac Cardiovasc Surg Dec 2009;57(8):476-9.