Dogs and cats undergoing VATS should have a thorough preoperative evaluation, including a complete physical and neurologic examination, complete blood count, serum chemistry, urinalysis, and thoracic imaging. Fluid, electrolyte, and acid–base abnormalities should be addressed before anesthesia. Anemic dogs should be transfused with erythroid-rich blood (packed red blood cells or whole blood) to maximize oxygen-carrying capacity before anesthesia and VATS. Significant hemorrhage or preoperative anemia can complicate the procedure and compromise the patient during VATS. Because oxygen delivery (CO × O₂ content) to tissues is dependent on the oxygen content of blood (Hg × SPO₂ × 1.34 + PaO₂ × 0.003), most significantly hemoglobin, patients undergoing thoracoscopic surgery should have a minimum preoperative hematocrit of 30% and blood transfusion should be considered in patients with marked intraoperative hemorrhage. A cross-match should be performed ahead of surgery, and donor blood should be readily available if needed in an emergency. Rupture of a great ­thoracic vessel may result in the near-immediate death of the patient if not dealt with rapidly, and the surgeon must avoid this complication by judicious preparation, careful attention to technique, and possessing the ability to convert to thoracotomy rapidly.

Depending on the underlying pathology or suspected pathology, survey thoracic radiography, echocardiography, contrast-enhanced computed tomography, or magnetic resonance imaging (MRI) may be indicated. In general, dogs with pericardial effusion should undergo echocardiography in addition to survey radiography and electrocardiography before VATS pericardectomy and pericardoscopy. If diastolic function is compromised by cardiac tamponade, pericardiocentesis should be performed before surgery. Echocardiography is more sensitive in detecting epicardial masses if ­pericardial fluid is present.³ MRI does not appear to be reliable in differentiating neoplastic from non-neoplastic causes of pericardial disease in dogs.⁴ In dogs with a pronounced pneumothorax or pleural effusion, preoperative thoracocentesis or placement of a thoracic drain should be accomplished before VATS. Thorough preoperative assessment facilitates patient selection for a VATS approach and therefore reduces the risk for conversion to thoracotomy and allows for more accurate surgical planning.

Dogs and cats undergoing VATS are prepared similarly to those undergoing traditional thoracotomy. This is because general surgical principles apply to both open and VATS operations and because VATS may require elective or emergent conversion to an open thoracotomy if complications such as inability to complete the procedure or major hemorrhage occur. It is therefore mandatory that the minimally invasive thoracic surgeon has a secondary site prepared for an open conversion for all VATS procedures. Finocietto retractors, electrosurgical capabilities, vascular forceps and clip applicators, vessel-sealing devices, and staplers normally used for open thoracic surgery should be made available in the operating suite ready for immediate use.⁵ For patients in which a median sternotomy may be used for conversion, an oscillating saw should be present. After the VATS patient is induced, a wide surgical clip is completed, which includes the regions that may be needed if conversion becomes necessary. Thoracic surgical site infections have the potential to progress to pyothorax if not detected early and treated effectively. Thus, careful attention to surgical asepsis and patient preparation should be considered paramount in patients undergoing thoracic surgery even if a minimal VATS approach is used.

Perioperative antibiotic administration is recommended in VATS patients just as it is recommended in patients undergoing open thoracic surgery to reduce the risk of surgical wound infection.⁶ All surgical wounds are contaminated by bacteria, but only a small fraction of these become infected. VATS is likely associated with a reduced risk of surgical site infection compared with thoracotomy or median sternotomy.⁷ The risk of developing a postoperative infection varies greatly with the nature of the operation and the characteristics of the patient undergoing the procedure. The optimal timing for the preoperative dose of antibiotics is within 30 to 60 minutes of the start of the surgical incision.^8,9 In human surgery, repeat intraoperative antimicrobial dosing is recommended to ensure adequate serum and tissue concentrations of the antibiotic if the duration of the procedure exceeds two half-lives of the drug or if there is excessive blood loss during the procedure.⁸ In veterinary surgery, several different protocols have been suggested with most surgeons using preoperative cefazolin at 22 mg/kg intravenously and then every 90 minutes for the remainder of the procedure.^10,11 The prophylactic antibiotic need not be administered beyond 24 hours postoperatively unless a major break in sterile technique or a change in contamination classification indicates that a therapeutic course of antimicrobials should be prescribed.

The initial requirement for any VATS procedure is an active pneumothorax. However, in some cases, increasing the amount of working space beyond that created by the initial pneumothorax may be necessary or beneficial for safe completion of a VATS procedure. Numerous factors play a role in limiting the actual amount of operable space during VATS, including patient size and morphology, positioning, instrumentation, and attributes of the patient’s underlying disease (e.g., adhesions, effusion, tumor size). Various techniques have been used to circumvent these limitations, including patient tilting or repositioning, organ retraction, intermittent ventilation, pleural space CO₂ insufflation, and one-lung ventilation (OLV).

Pneumothorax causes retraction of the pulmonary parenchyma away from the thoracic wall, which generates the initial exposure and working space necessary to evaluate the pleural space. Pneumothorax also limits pulmonary expansion and therefore gas exchange at the blood–gas interface of the alveoli. Consequently, hypoventilation and hypoxemia will result if the patient is not adequately supported. Gas exchange is further impaired by positioning of the patient, use of pleural insufflation with CO_2, and use of one-lung ventilation techniques.^12,13-16 However, the addition of positive end-expiratory pressure ventilation may minimize some of these untoward effects.¹³

Appropriate port placement is critical to the success of a VATS procedure. In some instances, an exploratory thoracoscopy may be necessary before a definitive procedure such as lung lobectomy, or a targeted procedure such as lung lobectomy may be planned based on preoperative imaging. Regarding the former, ports should initially be placed to allow for triangulated evaluation of the major cardiopulmonary structures. After the target organ has been ­identified, additional ports can be placed as needed to perform the definitive treatment. If the definitive organ and procedure are known in advance, then the patient’s position and ports should be placed to best create triangulation around the region of interest. Inappropriate patient and port positioning may result in the inability to complete the VATS procedure and will increase the risk of complications.