Advances in Video-Assisted Thoracic Surgery, Thoracoscopy

Advances in Video-Assisted Thoracic Surgery, Thoracoscopy

Advances in Video-Assisted Thoracic S u r g e r y, T h o r a c o s c o p y Joseph Brad Case, DVM, MS KEYWORDS  Thoracoscopy  Video-assisted thorac...

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Advances in Video-Assisted Thoracic S u r g e r y, T h o r a c o s c o p y Joseph Brad Case,

DVM, MS

KEYWORDS  Thoracoscopy  Video-assisted thoracic surgery  Pericardectomy  Lung lobectomy  Pleural  One-lung ventilation  Pneumothorax KEY POINTS  Patient selection is critical, and general and specific contraindications exist.  Anesthetic management can be challenging and may require an anesthesiologist if one-lung ventilation (OLV) is to be used.  Elective and emergent conversion may be necessary, and the operating surgeon must be willing to convert if patient safety or the success of the surgery is in question.  Perioperative management is similar to cases undergoing planned thoracotomy.

PERICARDIAL EFFUSION AND NEOPLASIA

Pathologic pericardial effusion can result from malignancy, infectious, or idiopathic etiologies. Among malignant causes, hemangiosarcoma of the right auricular appendage is most common, but aortic body chemodectoma and diffuse mesothelioma are also seen. Malignant pericardial effusion is diagnosed in about 70% and idiopathic pericardial effusion is seen in about 20% to 30% of dogs presenting for pathologic pericardial effusion.1,2 When the volume of effusion becomes significant, a reduction in end diastolic volume and cardiac output results, a condition referred to as cardiac tamponade. One of the most commonly performed video-assisted thoracic surgery (VATS) procedures in dogs is pericardectomy.2–6 The objective of pericardectomy is to excise enough pericardium to eliminate tamponade and to obtain a histologic diagnosis of the patient’s condition (Table 1). The surgeon must decide how much pericardium to excise when considering pericardectomy. In palliative cases, such as those associated with neoplastic effusions, a 4  4 cm pericardial window seems to be adequate unless right auriculectomy is being

The author has nothing to disclose. Small Animal Surgery, College of Veterinary Medicine, University of Florida, 2015 Southwest 16th Avenue, Gainesville, FL 32608, USA E-mail address: [email protected] Vet Clin Small Anim - (2015) -–http://dx.doi.org/10.1016/j.cvsm.2015.07.005 vetsmall.theclinics.com 0195-5616/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.

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Table 1 VATS indications and contraindications Indications

Contraindications

Pericardial effusion and neoplasia

Lack of training and instrumentation

Cranial mediastinal mass resection

Unstable patient

Pulmonary neoplasia

Lack of anesthetic support

Pulmonary blebs and bullae

Large masses or lesions

Chylothorax



Vascular ring anomaly



considered.2,3,6,7 With presumed idiopathic cases, a complete pericardioscopic evaluation is necessary to reduce the chance of a missed diagnosis and a larger pericardectomy is indicated.2,8 Because masses are common on the right auricle and heart base (Fig. 1), the surgeon must have adequate experience and understanding of the pericardial anatomy before performing pericardoscopy, auriculectomy, or epicardial biopsy.6,7 The combination of a pericardial window and pericardial fillet has recently been described.9 The pericardial fillet facilitates exposure of most of the intrapericardiac anatomy without the need for subphrenic pericardectomy.9 Pericardial fillet is performed by creating several individual incisions, from ventral to dorsal toward the phrenic nerves, following excision of an approximate 4  4 cm apical window (Fig. 2). The orientation of the window (and fillet if performed) is likely not as important as performing a thorough pericardioscopic assessment. This is particularly important in presumed idiopathic cases, because it is possible for small nodules and masses to be identified on endoscopy around the heart base (Fig. 3) in dogs with a preoperative negative echocardiogram.2,8 In this scenario, some dogs are tentatively diagnosed with an idiopathic pericardial effusion. If a representative epicardial (Fig. 4) sample is not obtained during pericardioscopy and/or if the pericardial sample obtained is not representative of the underlying disease, then a missed diagnosis and lost opportunity for disease-specific medical therapy occurs. Right auricular mass resection in combination with pericardectomy has recently been described in nine dogs.6 One dog died during surgery from hemorrhage but eight

Fig. 1. Intraoperative image of a large chemodectoma originating from the heart base in a dog undergoing VATS pericardectomy.

Video-Assisted Thoracic Surgery, Thoracoscopy

Fig. 2. Intraoperative image of a dog undergoing VATS pericardial window (A) and pericardial fillet (B). The arrow heads show the phrenic nerve. (Courtesy of Mary Ann Radlinsky, DVM, MS, DACVS, University of Georgia, Athens, GA.)

dogs underwent successful resection of the atrial mass. Dogs with masses limited to the tip of the atrial appendage were considered to be good candidates for a VATS auricular resection.6 The benefits of performing appendage resection in conjunction with pericardectomy are to obtain histologic diagnosis and to reduce the risk of hemorrhage from atrial rupture.6,7 CRANIAL MEDIASTINAL NEOPLASIA

Cranial mediastinal neoplasia is uncommon in dogs and cats. However, when observed, the most likely diagnoses are lymphoma, thymoma, and less commonly thymic carcinoma. Other neoplasms of the cranial mediastinum have also been described.10 Dogs with thymic lymphoma are managed medically, whereas dogs with other neoplasms, such as thymoma, are treated surgically. Traditionally, resection of cranial mediastinal masses (CMMs) has been accomplished via median sternotomy or intercostal thoracotomy.11–14 Recently, a VATS approach to CMM resection in two dogs was reported.15 A VATS approach to CMM resection is feasible and associated with low operative morbidity, although ultimate prognosis depends on the underlying disease. For example, dogs with myasthenia gravis and megaesophagus have a poor

Fig. 3. Multiple small nodules on the aortic root and right auricle in a dog undergoing pericardectomy and epicardial biopsy for presumed idiopathic pericardial effusion. The pericardium histopathology showed pericarditis and the epicardial biopsy revealed mesothelioma.

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Fig. 4. A dog with presumed idiopathic pericardial effusion undergoing epicardial biopsy at the heart base after pericardectomy.

short-term outcome.11,14,16 Preoperative computed tomography (Fig. 5) is strongly advised in preoperative case selection for confirmation of noninvasiveness. Dogs greater than 20 kg with noninvasive masses and masses with a diameter less than 7 cm or an approximate volume less than 300 cm3 seem to be good candidates for a CMM resection.16 Dogs undergoing VATS CMM resection are positioned in dorsal recumbency (Fig. 6). Ports are placed as previously described.15 The fourth intercostal space facilitates finger-assisted retraction and ultimately extraction of the mass following dissection. Once all ports have been placed and the mediastinum has been dissected, the mass is explored laterally and dorsally to ensure no adhesions or infiltration of major vessels, such as the cranial vena cava, brachycephalic artery, and left subclavian artery (Fig. 7). It is common for the internal thoracic vessels (Fig. 8) to be adhered and infiltrative to the mass but careful dissection allows separation of these vessels without compromise of the tumor capsule. Dissection of the mass begins ventrally to separate the mass from the internal thoracic vessels. This is usually performed with a combination of sharp and blunt dissection using VATS Kelly and right-angle dissecting forceps in addition to a vessel-sealing device. Perhaps the most critical aspect of the dissection is ventral retraction of the mass away from the phrenic nerves and major cardiac vessels (eg, vena cava and brachycephalic artery) during dissection dorsal to the mass. This is accomplished with sponge forceps, Babcock forceps, fan retractors, and/or transthoracic digital retraction (Fig. 9). Once the mass has been dissected free, a sterile specimen retrieval bag is used to remove the mass from the thoracic

Fig. 5. Sagital computed tomography image of a dog with a noninvasive thymoma. Notice the close association of the mass with the internal thoracic vessels and brachycephalic trunk.

Video-Assisted Thoracic Surgery, Thoracoscopy

Fig. 6. A dog correctly positioned in dorsal recumbency before VATS thymectomy.

cavity (Fig. 10). With the required training and experience with VATS, CMM resection is feasible and associated with low operative morbidity. A recent abstract revealed that only 1 out of 18 dogs undergoing VATS CMM resection did not survive surgery.16 The complication in this case was laceration of the cranial vena cava during dissection dorsal to the mass. PERSISTENT RIGHT AORTIC ARCH AND LEFT LIGAMENTUM ARTERIOSUM

Vascular ring anomalies are uncommon malformations of the aortic arches during fetal development, which result in some degree of constriction of the esophagus. The most common vascular ring anomaly seen in dogs is the persistent right aortic arch with a left ligamentum. This malformation causes the esophagus to become constricted between the ligamentum arteriosum, right-sided descending aorta and pulmonary artery, and the trachea. Surgical transection of the ligamentum is

Fig. 7. Transverse computed tomography image of a dog with a noninvasive thymoma. Notice the cranial vena cava, brachycephalic trunk, and subclavian vessels immediately dorsal to the mass.

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Fig. 8. Intraoperative image of a dog undergoing VATS thymectomy. The right-angle forceps are useful in dissecting the internal thoracic vessels away from the mass.

necessary and the prognosis is good to excellent in most cases, although some degree of esophageal dilation may persist.17 Dogs are young and typically malnourished at the time of diagnosis and are therefore not ideal surgical candidates. Effort should be made to encourage nutritional support as best possible before surgical intervention, although treatment should not be delayed for an extended period of time. Because affected dogs usually only tolerate gruel diets, small-volume elevated feedings can be continued up to 12 hours before surgery to reduce the chance of hypoglycemia. A VATS approach to ligamentum transection has been reported in one, two, and 14 dogs.18–20

Fig. 9. Intraoperative image of a thymoma being elevated ventrally by the surgeon’s finger to aid in dorsal dissection. Ventral elevation is critical during dissection to reduce the risk of injury to a great vessel.

Video-Assisted Thoracic Surgery, Thoracoscopy

Fig. 10. Intraoperative image of a thymoma being placed in a specimen retrieval bag for removal from the thorax.

The left hemithorax is clipped completely from dorsal to ventral across midline and from the caudal cervical region to the cranial abdomen. Dogs are positioned in right lateral recumbency (Fig. 11) with the dorsal spine elevated approximately 15 . Three intercostal ports are used for ligamentum transection. The author’s preference is to use two 3.5-mm pediatric threaded cannulas in the dorsal and ventral seventh or eighth intercostal spaces and a 1-mL syringe case in between the two pediatric ports. A 3-mm telescope is inserted through one of the threaded cannulas and a metered blunt probe is placed through the other for exploration and palpation of the ligamentum. A flexible endoscope can be positioned in the esophagus during VATS to help identify the ligamentum (Fig. 12). Once the esophagus and ligamentum are identified, right-angle or curved Kelly forceps are used to dissect the ligamentum free from the esophagus (Fig. 13). A 5-mm bipolar vessel-sealing device is placed in the third port and used to seal and divide the ligamentum. Residual constriction can be evaluated with a flexible endoscope or by placing a Foley catheter in the esophagus and distending the balloon while retracting the balloon across the constricted region.

Fig. 11. Image of a puppy positioned in lateral recumbency with the spine slightly elevated before VATS ligamentum arteriosum ligation and division.

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Fig. 12. Intraoperative image of the esophageal endoscope light demonstrating the location of the esophageal constriction.

Any remaining fibers should be excised to allow complete relief of the esophageal constriction. PULMONARY NEOPLASIA

Video-assisted lung lobectomy is indicated for primary and metastatic pulmonary lesions.21,22 Although early experience suggested that lesions away from the hilus of the left caudal lung lobe were most ideal for VATS lung lobectomy, a recent study has demonstrated feasibility in most lung lobes provided mass lesions are less than 8 cm in diameter or less than 150 cm3 in dogs greater than 30 kg.22 Video-assisted lung lobectomy has been described.21–23 The use of one-lung ventilation (OLV) is recommended during VATS lung resection to improve visibility and to facilitate application of the stapling device to the collapsed lung.21,22 Identification of surgical margins is challenging and tracheobronchial lymphadenectomy and

Fig. 13. Intraoperative image of a puppy with a persistent right aortic arch and left ligamentum undergoing ligamentum ligation and division. (Courtesy of Dr Eric Monnet, Colorado State University, Fort Collins, CO.)

Video-Assisted Thoracic Surgery, Thoracoscopy

histopathology is recommended to better assess prognosis and the need for adjunctive treatment in dogs with lung tumors.22,24,25 Recently, near-infrared field fluorescent (NIRF) technology has been investigated for pulmonary neoplasia VATS applications experimentally.26 NIRF allows for activation of cancer cells in tissues, such as the pleura and lung. NIRF is considered a smart or specific form of fluorescent imaging, which creates a significant visible tumor-to-background ratio. The increased visible distinction between neoplastic and normal tissue, in addition to the superior illumination and visualization provided by VATS, seems to facilitate intraoperative assessment of surgical margins and sentinel lymph node assessment (Figs. 14 and 15). Although no literature on VATS applications of NIRF currently exists in veterinary surgery, early evidence supports the use of NIRF technology in this application and future study is indicated.26–28 The value of tracheobronchial lymphadenectomy and histopathology has been established.24 Consequently, the surgeon performing VATS lung lobectomy must have a plan to assess these lymph nodes to better treat and prognosticate their patients. Tracheobronchial lymphadenectomy is feasible in dogs and has recently been described in clinical and experimental settings.22,29 Tracheobronchial lymphadenectomy is performed in lateral recumbency and OLV is recommended to facilitate visualization of the tracheobronchial lymph nodes (TBLN) and to impart increased safety during the dissection.22,29 The left TBLNs are approached from the left side and the central and right TBLNs are approached from the right.29 The affected hemithorax is clipped completely from dorsal to ventral across midline and from the caudal cervical region to the cranial abdomen. Dogs are positioned in lateral recumbency with the dorsal spine slightly elevated. Once the dog is positioned, OLV is induced using a double-lumen endobronchial tube (Fig. 16) or an endobronchial blocker.21,22,29,30 Three to four 5.5- and/or 11.5-mm cannulas are typically required for VATS lung lobectomy. For access to cranial lung lobes, cannulas are placed in triangulating fashion along the ninth and tenth intercostal spaces (Fig. 17). For caudal and middle lobes, cannulas are placed along the third, fourth, or fifth intercostal spaces. For caudal lung lobectomy, the pulmonary-diaphragmatic ligament must be divided before lobectomy. A blunt palpation probe is helpful to elevate and

Fig. 14. Intraoperative image of a dog with a lung tumor before tracheobronchial lymphadenectomy. The asterisk shows the azygous vein and the arrow shows the location of the TBLN. (Courtesy of Dr Michelle Steffey, University of California Davis, Davis, CA.)

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Fig. 15. Intraoperative image of the same dog from Fig. 14 following administration of indocyanine green and visualization with NIRF. The asterisk shows the azygous vein and the arrow shows the location of the TBLN. (Courtesy of Dr Michelle Steffey.)

evaluate the parietal and visceral pulmonary surfaces (Fig. 18). Once the affected lung has been isolated, a 45- or 60-mm endoscopic stapler is inserted via one of the 11.5-mm cannulas or an additional cannula can be placed to allow unrestrained access to the pulmonary hilus (Fig. 19). For complete lung lobectomy, the stapler is

Fig. 16. Double-lumen endobronchial tube. The inset shows the angled bronchial portion of the tube and the Murphey eye from the endotracheal region.

Video-Assisted Thoracic Surgery, Thoracoscopy

Fig. 17. Intraoperative image showing cannula location for a dog undergoing VATS caudallung lobectomy. (Courtesy of Dr Phil Mayhew, University of California Davis, Davis, CA.)

directed to the most proximal aspect of the pulmonary hilus before deploying the staples (Fig. 20). The lung lobe should be placed in an endoscopic tissue retrieval bag before extraction from the thorax to reduce the risk of neoplastic port site implantation. TBLN excision can be performed by incising the pleura around the local TBLN followed by a combination of blunt dissection using right-angle Kelly forceps and vessel-sealing tissue dividing instruments. The TBLNs are immediately adjacent to the pulmonary artery and vein so caution should be exercised during the dissection. Recently, a video-assisted, extracorporeal method for lung lobectomy or thoracoscopic-assisted pulmonary surgery was described in three cats and eight dogs.31 This hybrid approach to lung lobectomy offers a minimally invasive alternative to open thoracotomy but at the same time eliminates the requirement for OLV and intracorporeal stapling.31 Patients are prepared similarly to that described for VATS lung lobectomy.

Fig. 18. Intraoperative image from the same dog from Fig. 17 showing atraumatic palpation and manipulation of the mass with a blunt palpation probe. (Courtesy of Dr Phil Mayhew.)

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Fig. 19. Intraoperative image from the same dog with a 60-mm endoscopic stapler applied to the hilus of the caudal lung lobe. (Courtesy of Dr Phil Mayhew.)

Patients are positioned in lateral recumbency with the diseased hemithorax uppermost. A 5.5-mm cannula with a 5-mm 30 telescope is placed initially for exploration of the hemithorax and identification of the diseased lung. The intercostal location of the telescope cannula may vary but it is recommended that cranial lobes be explored from the 9th to 12th intercostal spaces and caudal lobes from the fourth to sixth intercostal spaces. Once the affected lobe is identified, a miniature extraction thoracotomy is made over the hilus of the lobe and a wound retractor placed to distract the intercostal wound (Fig. 21). The affected lobe is grasped with Babcock forceps or the surgeon’s finger under intracorporeal visualization and elevated via the extraction wound (Fig. 22). Either partial or complete lung lobectomy is then performed using endoscopic or traditional stapling devices (Fig. 23). TBLNs should be evaluated before

Fig. 20. Intraoperative image from the same dog following VATS lung lobectomy. (Courtesy of Dr Phil Mayhew.)

Video-Assisted Thoracic Surgery, Thoracoscopy

lobectomy and extirpation performed if medically indicated. The miniature thoracotomy and cannula incisions are closed routinely following placement of an indwelling chest tube. In this report, median surgery time and time to discharge were 90 minutes and 3 days, respectively. No significant complications were reported and all patients survived to hospital discharge.31 SPONTANEOUS PNEUMOTHORAX

VATS treatment of spontaneous pneumothorax in dogs has been described in 3 and 12 dogs.32,33 In the original case report, three dogs were treated successfully without complications and all had a good outcome.32 More recently, in a report of 12 dogs with spontaneous pneumothorax and pulmonary blebs and bullae, a rate of conversion to thoracotomy of 50% to 60% was reported because of inability to consistently identify active pulmonary leaks.33 In this study adhesions and type 1 pulmonary lesions were thought to be the cause of inability to identify active leaks in several dogs. In one dog an adhesion in the dorsal and cranial aspect of the left cranial lobe was identified following median sternotomy. The lobe was found to leak only after conversion and disruption of the adhesion. In another dog, a missed bulla was identified at postmortem examination after failure of resolution of the pneumothorax. This case was not converted to median sternotomy. The conclusions and recommendations from this report were to anticipate a high rate of conversion and to convert all cases of spontaneous pneumothorax if an explanatory lesion was not identified and treated during VATS. Finally, as is seen in human surgery, a VATS approach to spontaneous pneumothorax may be associated with a higher rate of recurrence.33 Exploratory and Partial Lung Lobectomy

Dogs are positioned in dorsal recumbency and are tilted about 15 to the right (Fig. 24) and left for evaluation of individual hemithoraces. Individual lung lobes are evaluated on the pleural and parietal surfaces. Following initial evaluation, each lobe is submerged in saline and a positive-pressure breath hold initiated (Fig. 25). In instances where significant expansion of the lung lobes is necessary to elicit a leak, obliteration of working room occurs, which prevents assessment of the pleural surfaces.33 This is

Fig. 21. Creation of a miniature thoracotomy and positioning of a surgical wound retractor over the hilus of the lung during thoracoscopic-assisted pulmonary surgery (TAPS). (Courtesy of Dr Jeff Runge, University of Pennsylvania, Philadelphia, PA.)

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Fig. 22. Elevation of the lung to be removed by the surgeon’s finger during TAPS. (Courtesy of Dr Jeff Runge.)

particularly true of type 1 pulmonary lesions and the author of this article has found these lesions exceptionally difficult to identify with a VATS approach. Consequently, if an active leak or lesion is not identified, conversion to median sternotomy is strongly recommended.33 If an active leaking lesion is identified during surgery, then partial or complete lung lobectomy can be performed (Fig. 26). For lesions in the middle to dorsal aspect of the lung lobe where a larger or complete lobectomy is necessary, the dog can be tilted and additional ports placed more dorsally to facilitate application of the endoscopic stapler. A 60-mm endoscopic stapler is recommended in most cases, and initiation of OLV is helpful during application of the endoscopic stapler. Saline can be infused on the staple line, and a breath hold maneuver performed to check for leaks (Fig. 27). For mid to apical lesions in which a partial lobectomy is indicated, an articulated endoscopic stapler can usually be applied via one of the ventral intercostal ports. Again, initiation of OLV is useful to facilitate application of the endoscopic stapling device.

Fig. 23. Intraoperative image of the same patient from the previous figures showing stapled lung lobectomy during TAPS. (Courtesy of Dr Jeff Runge.)

Video-Assisted Thoracic Surgery, Thoracoscopy

Fig. 24. Intraoperative image of a dog in dorsal recumbency being tilted to the right for VATS exploration and assessment of the left hemi-pleura.

The author of this article prefers to remove diseased lung from the thorax with an endoscopic retrieval bag because in some cases, bulla may result from neoplastic disease, which may not be diagnosed until histopathologic analysis has been completed.

Fig. 25. Intraoperative image of the left cranial lung lobe in a dog with spontaneous pneumothorax being submerged in sterile saline to assess for pulmonary rupture.

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Fig. 26. Intraoperative image of a dog undergoing VATS partial lung lobectomy. Only the parietal pleural surface is shown but both surfaces are evaluated before partial lung lobectomy.

Following exploration and lung lobectomy, all port sites are closed routinely. Again, if an explanatory lesion or actively leaking lobe is not identified, conversion to median sternotomy is strongly recommended. CHYLOTHORAX

Idiopathic chylothorax is a frustrating disease in dogs and cats and is often associated with recurrence or failure after initial therapy. Generally speaking, surgical treatment is the standard of care for idiopathic chylothorax in dogs and cats because medical therapy alone is unlikely to resolve the condition. A myriad of surgical treatments have been described and performed where the aims are ultimately to eliminate antegrade flow of chyle through the thoracic duct and/or to remove chylous effusion from the thorax. The most common procedures performed for cessation of chyle flow through the thoracic duct are thoracic duct ligation or embolization, cysterna chili ablation, and pericardectomy. Techniques used to remove fluid from the thorax include pleuroperitoneal shunt placement and thoracic omentalization. Success rates for resolution of chylous effusion following surgical intervention range from 80% to 100% in dogs and cats with most surgeons performing a combination of thoracic duct ligation,

Fig. 27. Intraoperative image of the same dog from the previous figure following partial lobectomy. The catheter is being used to drip saline over the suture line to assess for leakage.

Video-Assisted Thoracic Surgery, Thoracoscopy

pericardectomy, and/or cysterna chili ablation.34–38 Because access to multiple regions of the body is needed for these procedures, a video-assisted thoracic approach to the thoracic duct and pericardium may be of significance in dogs undergoing surgical treatment of idiopathic chylothorax. Two techniques have been described for VATS thoracic duct ligation and pericardectomy in dogs.34,35 The original report used an intercostal VATS approach to the thoracic duct with the dog in sternal recumbency (Fig. 28), followed by alteration of the dog into dorsal recumbency for pericardectomy.34 More recently, a similar approach was described but with the dogs in lateral recumbency for thoracic duct ligation followed by repositioning into dorsal recumbency for pericardectomy.35 Thoracic Duct Ligation

The entire thorax and abdomen are clipped and prepared aseptically for surgery. The dog is positioned in left lateral recumbency and the initial telescope portal is placed in the eighth or ninth intercostal space, approximately at the middle or dorsal third of the space (Fig. 29). Two instrument portals are then placed, one in the dorsal third of the ninth or tenth intercostal space and the other in the dorsal third of the seventh or eighth intercostal space. Five-millimeter cannulae are preferred for the telescope and dissecting instruments and at least one 11.5-mm cannula is required for the vessel-clip applicator. Once caudal mediastinal visualization has been accomplished, a miniature laparotomy is performed in the right lateral abdomen. A surgical wound retractor is used to retract the abdominal wall, and the ileocecocolic lymph nodes are isolated for injection of methylene blue. Less than 1 mL of a 1:1 solution of sterile saline to methylene blue is sufficient in most cases. Filling of the thoracic duct usually occurs within 5 to 10 minutes (Fig. 30). Once the thoracic duct is well visualized, dissection using a 5-mm vessel sealing device and 5-mm right-angle and Kelly forceps can commence. Dissection should be performed as caudal or near to the diaphragmatic crus as possible and all thoracic duct branches need to be identified and clipped (Fig. 31). Use of Harmonic shears for thoracic duct seal has been reported in a nondiseased, experimental canine model.39 In this study, 50% of dogs were converted to an assisted miniature thoracotomy and 50% required resealing of the thoracic duct because of an inadequate initial seal. Ultimately, all six dogs experienced complete seal of the thoracic duct as confirmed by postprocedure lymphangiography

Fig. 28. Intraoperative image of a dog in sternal recumbency before VATS thoracic duct ligation. (Courtesy of Dr Phil Mayhew.)

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Fig. 29. Intraoperative view demonstrating cannula placement in a dog undergoing VATS thoracic duct ligation. (Courtesy of Dr Phil Mayhew.)

Fig. 30. Intraoperative view of the caudal mediastinum following dissection to the thoracic duct. Notice the thoracic duct is easily observed following administration of methylene blue. (Courtesy of Dr Phil Mayhew.)

Video-Assisted Thoracic Surgery, Thoracoscopy

and histopathology. Evaluation in dogs with naturally occurring disease is necessary before this can be recommended clinically. It is strongly recommended that an intraoperative or postoperative lymphangiogram be performed to rule out continued thoracic duct patency following thoracic duct ligation. With the approach described by Mayhew and colleagues35 this is easily accomplished immediately after thoracic duct ligation by reinjection of the ileocecocolic lymph nodes with iohexol under fluoroscopic visualization. The miniature laparotomy and portal sites are closed routinely. Pericardectomy

If pericardectomy is to be performed, the dog can be repositioned into dorsal recumbency and a 4-cm apical pericardical window with pericardial fillet can be performed as previously described.34 If a subphrenic pericardectomy is desired, then OLV has been recommended to improve visualization of the phrenic nerves during dissection.40 Dissection of the pericardium is completed approximately 1 cm ventral and parallel to the phrenic nerves. COMPLICATIONS

Complications include hemorrhage (great vessels, intercostal vessels, pericardium), pneumothorax (pulmonary pleura, missed bleb bullae), hypoxemia (V/Q mismatch, pleural space, pneumonia), and port site metastasis. POSTOPERATIVE CARE

Thoracostomy drains are recommended following VATS (Fig. 32). Intrapleural and intercostal bupivicaine is administered for local analgesia. Intravenous opioids are administered for at least 24 hours postoperatively. OUTCOMES Pericardectomy and Pericardial Window

Median disease free interval (DFI) for dogs with idiopathic pericardial effusion treated by VATS pericardial window was 11.6 months and was significantly worse than dogs treated by subtotal pericardectomy (median DFI not reached) in one recent study.2 However, dogs with a neoplastic cause for their pericardial effusion experienced a similar DFI

Fig. 31. Intraoperative view from the same dog following ligation of the thoracic duct with vessel clips. (Courtesy of Dr Phil Mayhew.)

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Fig. 32. Intraoperative image of a dog following a VATS procedure with a narrow chest tube placed.

if treated with a pericardial window (median DFI, 2.7 months) or a subtotal pericardectomy (median DFI, 3.8 months). Similarly, median survival time (MST) for dogs with idiopathic pericardial effusion treated by VATS pericardial window was 13.1 months and was significantly worse than dogs treated by subtotal pericardectomy (MST not reached).2 However, dogs with a neoplastic cause for their pericardial effusion experienced a similar MST if treated with a pericardial window (MST, 2.7 months) or a subtotal pericardectomy (MST, 4.0 months). The 1-, 2-, and 3-year survival rates for dogs with an idiopathic pericardial effusion undergoing VATS pericardial window was 58%, 35%, and 35%, respectively. Oneyear survival for dogs with a neoplastic effusion undergoing VATS pericardial window was 9%.2 Cranial Mediastinal Mass Extirpation

CMM extirpation is an excellent application for VATS in select dogs. A conversion frequency of 10% has been reported but careful patient selection and proficiency with VATS will likely reduce the incidence of conversion. Survival in dogs with a noninvasive thymoma undergoing VATS thymectomy was 100% in a recent study. In this same report, dogs with a thymoma and paraneoplastic myasthenia gravis with megaesophagus had an MST of only 20 days following successful VATS thymectomy.16 Most of these dogs died of complications related to myasthenia gravis and megaesophagus (eg, aspiration pneumonia). Left Ligamentum Division

Outcome is good to excellent in most dogs.18–20 Lung Lobectomy: Neoplasia

Although conversion to thoracotomy has been reported in up to 44% of dogs undergoing VATS lung lobectomy, a recent report has demonstrated a much lower rate (9%), which is likely the result of improved case selection and progressive experience

Video-Assisted Thoracic Surgery, Thoracoscopy

with VATS lung lobectomy.21,22 The reported median surgery times for VATS lung lobectomy are 108 and 120 minutes.21,22 Clinical outcome is equivalent to dogs undergoing lung lobectomy via thoracotomy.22 Survival is ultimately related to the underlying disease process as indicated by histopathology. Pulmonary Exploratory and Partial Lung Lobectomy–Spontaneous Pneumothorax

Complete pleural exploratory and detection of pulmonary ruptures is challenging with a VATS approach in some cases. Recently, conversion to median sternotomy was required in 58% of dogs with spontaneous pneumothorax although conversion was not necessary in another report of three dogs with spontaneous pneumothorax.32 Although clinical outcome may be good with a VATS approach to spontaneous pneumothorax in some dogs, only 50% of dogs treated with VATS without conversion experienced a successful clinical outcome. In contrast, 83% of dogs that underwent conversion to median sternotomy had a successful outcome.33 Thoracic Duct Ligation and Pericardectomy

Conversion to thoracotomy was not required in any dogs undergoing thoracic duct ligation for idiopathic chylothorax in two recent studies. Resolution of chylous effusion occurred in six out of seven dogs with idiopathic chylothorax and resolution of clinical signs occurred in six out of six dogs with a median follow-up time of 39 months, range 19 to 60 months in two separate studies.34,35 SUMMARY

The indications and applications for VATS are evolving constantly in veterinary surgery as more and more clients and surgeons are recognizing the benefits of reduced tissue trauma, less postoperative pain, and quicker recovery in their animals. As technology and experience continue to progress, this trend is sure to continue. Because specialized training and experience is a requirement and because VATS is associated with prolonged surgical times and certain limitations, prospective inquiries are indicated to better determine the relative benefits and possible limitations of VATS compared with traditional thoracotomy and sternotomy. REFERENCES

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