Thoracic surgery (part 2) (Proceedings)

Surgical implications of the following conditions are discussed: pulmonary neoplasia, spontaneous pneumothorax, and pyothorax. Pulmonary lobectomy (partial and complete) and postoperative management recommendations are included.

Pulmonary neoplasia

Primary lung tumors, while uncommon in dogs and cats, are most frequently seen in older animals (9 to 12 years of age). Tumors are most frequently malignant, with carcinoma being most common. The most common clinical sign in dogs with pulmonary neoplasia is a nonproductive cough. Thoracic radiography is most useful for diagnosing primary pulmonary neoplasia, with a single, well-circumscribed, dense soft tissue pulmonary mass usually noted. Cavitary lesions also may be seen. Definitive diagnosis may be achieved by fine-needle aspiration of the mass, although excisional biopsy confirmation is indicated. Treatment of choice for solitary pulmonary masses is complete lung lobectomy. Chemotherapy may be indicated postoperatively.

Spontaneous pneumothorax

Spontaneous pneumothorax occurs in dogs without evidence of trauma. This condition results most frequently from rupture of pulmonary blebs or bullae. The cause of pulmonary blebs and bullae in dogs is unknown, and definitive diagnosis and determination of extent of disease presurgically often is difficult to achieve. Diagnosis is based on physical and radiographic findings, evidence of pneumothorax on thoracentesis, and lack of a recent history of trauma.

Treatment of spotaneous pneumothorax usually involves thoracic exploration and partial or complete pulmonary lobectomy. Intermittent thoracentesis and thoracostomy tube placement to evacuate the pleural cavity frequently are ineffective long-term. A median sternotomy approach is preferred to a lateral thoracotomy, because the median sternotomy provides better exposure of the entire pleural cavity and access to both lungs. Source(s) of air leakage usually can be located by temporarily filling the pleural cavity with warm saline and observing for air bubbles during ventilation. Lesions, particularly peripheral lesions, are often excised by partial pulmonary lobectomy using stapling equipment. Place a thoracostomy tube, and record the amount of air retrieved daily. Remove the thoracostomy tube when air is no longer retrieved.

Exercise restriction is recommended in the immediate postoperative period. Recurrence of spontaneous pneumothorax is higher when nonsurgical methods are used than when surgery is performed.

Pulmonary lobectomy

Surgical removal of all or a portion of a lung lobe is performed with some frequency in the dog and cat. Indications for pulmonary lobectomy include pulmonary abscessation (usually caused by foreign bodies, such as grass awns), lung lobe torsion, pulmonary blebs or bulla (as a cause of spontaneous pneumothorax), and neoplasia.

Partial lobectomy

Non-neoplastic conditions involving the distal aspect of a lung lobe, including pulmonary blebs and bullae, may be amenable to partial lobectomy. Stapling equipment (e.g., thoracoabdominal [TA] staplera) or suture techniques can be employed. Match the size of the stapling equipment (30 mm, 55 mm, or 90 mm) to the width of the portion of lung lobe to be excised. Excise the portion of the lung lobe distal to the staples and observe the edge for evidence of air leakage or hemorrhage. Place simple interrupted sutures (3-0 to 5-0 synthetic absorbable suture material) to control air leaks. Suture techniques often involve placing a continuous overlapping pattern of synthetic absorbable suture material (3-0 or 4-0) proximal to the lesion to be excised. Be sure to select a suture that has a swaged-on needle with a diameter that closely matches that of the suture. After excision, suture the edge of the lung lobe in a simple continuous pattern using synthetic absorbable suture material (3-0 to 5-0). Observe for leaks and insert additional sutures, as needed.

Complete lobectomy

Surgical options for performing a complete lobectomy include individual ligation of components of the hilus (artery(ies), vein(s), and bronchus), en masse ligation of the hilus with a single large suture, use of stapling equipment, or combinations. When removing a twisted lung lobe, do not untwist the lobe prior to its removal. An en masse ligation technique using larger suture diameter (0 or #1) is used. Once the involved lung lobe has been removed, additional ligatures (usually on the artery) may need to be placed if hemorrhage is noted upon untwisting of the pedicle.

For the individual ligation technique, control the arterial supply to the lobe first. When removing lung lobes near the cranial aspect of the thorax (cranial or middle lobes), be particularly careful to preserve arterial supply to the more caudal lung lobes. The segmental pulmonary artery to the lobe is dorsal to the left bronchus and ventrolateral to the right bronchus. Isolate the segmental pulmonary artery and place 3 ligatures on the isolated segment. The middle ligature should be a transfixation ligature. Transect the artery between the distal two ligatures. Isolate the pulmonary veins (which are ventral to the bronchus) and double ligate them. Transect the veins between the ligatures. Ligate the bronchus (and the associated bronchial artery) with synthetic suture material. Place a clamp distal to the ligature and transect the bronchus just proximal to the clamp. Remove the lung lobe. Oversew the end of the bronchus with a simple continuous pattern of 4-0 synthetic absorbable suture material. Check the distal end of the bronchus for air leaks, and place additional sutures, as needed.

Performing a complete lobectomy with stapling equipment is an acceptable alternative to the suturing technique. The equipment may be difficult to position, particularly in a small thorax, and its size should be matched with the width of the pedicle. Excise the lung lobe distal to the stapling device. Check the pedicle for leaks (air or blood), and place additional sutures, as needed.

Pyothorax management

Pyothorax, defined as suppurative inflammation of the pleural cavity, is a potentially recurrent condition resulting in systemic illness. Clinical signs of pyothorax often include dyspnea, tachypnea, anorexia, fever, and exercise intolerance. Pleural effusion is based on radiographic or ultrasonographic evaluation, while pyothorax is based on cytologic, microbiologic, and Gram-stain evaluation. Treatment is intended to improve ventilation, eliminate infection, and minimize pleural fibrosis and recurrence.

Sources of bacterial contamination include inhalation and migration of foreign bodies (especially grass awns), penetrating thoracic wounds, extension from bacterial pneumonia, esophageal perforations, and hematogenous spread. Multiple microorganisms may be isolated from dogs with pyothorax, with anaerobic bacteria frequently encountered. Gram-positive filamentous bacteria (Nocardia or Actinomyces spp.) may be isolated or noted on Gram-stain evaluation.

Dogs with pyothorax are frequently managed both medically and surgically. Medical management involves use of appropriate antimicrobial(s), usually for a minimum of 6 weeks. Antimicrobial selection should be based on culture and susceptibility testing results. Surgical management involves local treatment of the pleural cavity through use of thoracostomy tube(s), local lavage of the pleural cavity using warmed PSS or LRS with heparin (100 IU/kg body weight) at least twice daily, and possible debridement of the thoracic cavity via thoracotomy.

Long-term results of 50 dogs with pyothorax treated by one of three methods (thoracentesis and systemic antimicrobials only; thoracostomy tube[s], pleural lavage, and systemic antimicrobials, or thoracotomy with debridement, pleural lavage, and systemic antimicrobials) and associated microbiologic findings will be presented.

Postoperative considerations

Postoperative analgesia should be initiated before recovery from anesthesia in thoracotomy patients. Options include parenteral opioids, epidural opioids, local anesthetic blocks, and intra-pleural anesthetics. Butorphanolb and buprenorphinec produce less consistent analgesia but these drugs do not cause bradycardia and minimally depress respiration compared to oxymorphoned. Local anesthetic use (bupivacainee at < 2 mg/kg in dogs or 1 mg/kg in cats) as both an intercostal nerve block and within the pleural cavity seems to be helpful. Place and maintain a thoracostomy tube until it is no longer needed. Depending on the condition being treated, the tube can usually be removed within hours or days of surgery. Monitor patients closely in the postoperative period to verify that they are ventilating adequately. Oxygen supplementation in the immediate postoperative period is recommended. Such supplementation could be by nasal O2 or by oxygen cage.

Summary

Surgical management of pulmonary neoplasia, spontaneous pneumothorax, and pyothorax can be challenging. Selection of the proper surgical approach and conscientious perioperative patient management helps improve results.

     • Thoracoabdominal stapling device, Tyco Healthcare Group LP, Mansfield, MA 02048

     • Torbugesic, Fort Dodge, Fort Dodge, IA 50501

     • Buprenex, Norwich Eaton, Norwich, NY 13815

     • Numorphan, DuPont Pharmaceuticals, Wilmington, DE 19898

     • Bupivacaine, Abbott Labs, North Chicago, IL 60064

References & suggested reading

Boothe HW, Howe LM, Boothe DM, et al. Evaluation of outcomes in dogs treated for pyothorax: 46 cases (1983-2001). J Am Vet Med Assoc 2010;236: 657.

Holtsinger RH, Ellison GW. Spontaneous pneumothorax. Compend Contin Educ Pract Vet 1995;17: 197.

Rooney MB, Monnet E. Medical and surgical treatment of pyothorax in dogs: 26 cases (1991-2001). J Am Vet Med Assoc 2002;221: 86.

Greenfield DL. Respiratory tract neoplasia. In Slatter D (ed). Textbook of Small Animal Surgery, 3rd ed. W. B. Saunders Co, Philadelphia, 2003, p 2474.