Video-assisted thoracoscopic surgery

Video-assisted thoracoscopic surgery

Anesthesia type	General
Airway	Double-lumen endotracheal tube or endobronchial blocker
Lines and access	Adequate peripheral IV access; consider arterial line
Monitors	Standard; consider arterial monitoring
Primary anesthetic considerations
Preoperative	Pulmonary function testing, prehabilitation to optimize pulmonary status; consider thoracic epidural catheter
Intraoperative	One-lung ventilation; protective ventilation strategies; conservative fluid administration
Postoperative	Pain control, pulmonary hygiene
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Anesthesia for minimally invasive, video-assisted or robotic-assisted thoracoscopic surgery (VATS), is similar to anesthesia for open thoracic cases in many respects. However, achieving lung isolation quickly and completely is even more important, since even a slightly inflated lung may obstruct the surgeon’s view. Procedures that are amenable to VATS include but are not limited to:

• Mediastinoscopy
• Wedge resection or lung biopsy
• Lobectomy or segmentectomy, including bronchial sleeve resection
• Mediastinal and/or thoracic lymph node dissection
• Pleurodesis, mechanical or talc, for pleural effusion or spontaneous pneumothorax
• Decortication, including evacuation of empyema or hemothorax
• Thymectomy
• Lung volume reduction for severe emphysema
• The intrathoracic portion of esophagectomy
• Thoracic sympathectomy for hyperhidrosis or treatment of refractory ventricular tachycardia
  

Nearly any patient may be a candidate regardless of extremes of age or pulmonary disease. 

Procedures usually requiring open thoracotomy as opposed to VATS include pneumonectomy, intrathoracic tracheal resection, and chest wall resection. 

The advantages of VATS include decreased hospital length of stay, decreased morbidity, and less postoperative pain.

The keys to anesthesia success include:

• Availability of video laryngoscopy to facilitate intubation;
• Facility with placing both right and left endobronchial tubes;
• Skill with fiberoptic bronchoscopy;
• Having a dedicated team of personnel with expertise in thoracic anesthesiology.

Primary anesthetic considerations include optimal double-lumen tube placement with fiberoptic guidance, management of one-lung ventilation to avoid hypoxia and unnecessary hyperoxia, and use of protective ventilation strategies to avoid injury to the ventilated lung. Acute lung injury following thoracic surgery may lead to the development of ARDS with potentially lethal outcomes.

Preoperative management

Patients may present for VATS in sound health or with substantial disease burden.

A young, otherwise healthy patient who presents for thoracic sympathectomy for hyperhidrosis, or bleb resection with mechanical pleurodesis for recurrent spontaneous pneumothorax, may require no preoperative testing.

At the opposite extreme, patients may present with COPD, decreased lung function on the affected side, pleural or pericardial effusion, anemia, poor nutritional status, and effects of neoadjuvant chemotherapy and/or radiation. Whenever possible, prehabilitation in preparation for surgery should be considered to correct anemia, improve nutritional status, and improve functional capacity.

Patient evaluation

System	Considerations
Cardiovascular	Evidence of ventricular or valvular dysfunction, coronary disease, pulmonary hypertension
Respiratory	History of COPD, asthma, pleural effusion, pulmonary fibrosis, sarcoidosis, other pulmonary pathology
Neurologic	Peripheral neuropathy due to chemotherapy; evidence of myasthenia or paraneoplastic syndrome; assess appropriateness for epidural analgesia
Gastrointestinal	Evidence of carcinoid syndrome in cases of lung or endobronchial carcinoid tumor
Hematologic	Hypercoagulability due to underlying malignancy

Labs and studies

1. Routine preoperative laboratory, EKG, and radiographic studies as appropriate for patient age and institutional guidelines
2. Consider pulmonary function testing
3. Consider echocardiography, stress testing
4. Consider ventilation/perfusion (v/q) scan before major lung resection

Operating room setup

1. Double-lumen endotracheal tube (DLT) or endobronchial blocker as appropriate
2. Fiberoptic bronchoscope
3. Video laryngoscope to facilitate DLT insertion
4. Consider arterial line setup and transducer

Patient preparation and premedication

Patients should fast per institutional guidelines. Premedication is at the choice of the anesthesiologist depending on the patient's age and other relevant factors.

Regional and neuraxial techniques

Thoracic epidural analgesia may be considered especially if bilateral VATS is undertaken or if the surgeon thinks there is a high likelihood that conversion to open thoracotomy may be necessary.

The epidural catheter should be inserted at a high enough level that the patient will not have any lumbar motor block and can safely ambulate. Insertion prior to surgery offers the advantage of beginning continuous epidural infusion before the patient emerges from anesthesia. Some anesthesiologists prefer to utilize the epidural infusion along with general anesthesia for the entire case. Others prefer to activate the epidural catheter only near the end of surgery once blood loss is over in order to avoid intraoperative hypotension. There is no conclusive evidence that either approach is superior.

If the patient has a contraindication to epidural catheter placement, other regional techniques may be considered for postoperative pain relief: lumbar spinal opioid analgesia, erector spinae plane block, intercostal or paravertebral blocks.

Intraoperative management

The goals of intraoperative management include:

1. Optimal placement of DLT or endobronchial blocker for effective one-lung ventilation
2. Avoidance of hyperoxia which may be an exacerbating factor in acute lung injury
3. Maintaining satisfactory peak airway pressure (preferably less than 25-30 cmH20) and plateau pressure during one-lung ventilation; permissive hypercapnia may be necessary to avoid barotrauma to the ventilated lung
4. Avoiding excessive administration of crystalloid which been associated with acute lung injury

Monitoring and access

Standard monitors suffice for induction for many patients. Patients presenting for less invasive procedures may not require any more than standard monitoring for the duration of the case; examples might include thoracic sympathectomy for hyperhidrosis, limited lung biopsy for tissue diagnosis, talc pleurodesis for palliation of recurrent pleural effusion, or placement of PleurX catheter.

Arterial monitoring is commonly performed for lung resection, esophagectomy, thymectomy, and other major operative procedures. It enables continuous observation of blood pressure, and arterial blood gas measurement if indicated. Whether the arterial catheter should be inserted prior to or after anesthesia induction is a matter of anesthesiologist preference.

As the administration of fluids is best kept to a modest amount for lung resection, more than one well-functioning peripheral IV catheter may not be necessary. This again is a matter of individual judgment and preference.

Central venous pressure or flow parameter monitoring (e.g. FloTrac, Edwards Lifesciences) may be considered for patients undergoing procedures where substantial blood loss and/or fluid requirements are likely, such as esophagectomy or pleurectomy/decortication. A central venous line may be indicated in any procedure if peripheral veins are inadequate.

Induction and airway management

1. Induction medications and muscle relaxant choice per anesthesiologist preference. Ketamine may be a useful adjunct, especially for patients with chronic pain or a history of preoperative opioid use.
2. DLT (typically 35-39 Fr) is inserted and position confirmed with fiberoptic bronchoscopy. Selection of the DLT size is dependent on patient height and weight. A 37 Fr DLT is suitable for most average-size female patients, and 37-39 Fr for most male patients. DLT smaller than 35 Fr will not easily accommodate a fiberoptic bronchoscope.
3. Alternatively, an endobronchial blocker may be inserted through a single-lumen ETT.
4. The selection of right or left DLT is dependent on the situation and on user experience. One absolute indication for a R DLT is the planned sleeve resection of a L mainstem tumor (Fig. 1).
5. During any resection of the left lung, several factors argue in favor of placing a R DLT as opposed to a L DLT or L bronchial blocker:
   • There is no risk of stapling the tube or the endobronchial blocker to the bronchus during lobectomy or pneumonectomy, which can lead to serious or fatal complications.
   • If the tracheal cuff of the R DLT tears on the patient’s molars during intubation, the bronchial cuff will still guarantee lung isolation.
   • The tracheal lumen is the one occluded during lung isolation, so it is easy to look down the tracheal lumen with a bronchoscope to check the position of the blue (bronchial) cuff without interrupting ventilation.
   • With left lung surgery and a left DLT, the tracheal orifice (which is now in the dependent or posterior position after the patient is positioned R lateral decubitus) may be pushed against the tracheal wall and occluded.
   • With left lung surgery and a left DLT, pressure on the operated lung may dislodge the bronchial cuff and push it out into the trachea, impairing lung isolation.
   • The occurrence of complications or ventilation problems has not been shown to differ with R vs. L DLTs.
   • This video offers a more comprehensive review of R DLT insertion, indications, advantages and disadvantages.
6. For bilateral procedures, a L DLT is recommended.
7. Some centers have experience in doing selected VATS procedures under sedation or thoracic epidural anesthesia.

Figure 1: Malignant mucoepidermoid tumor in L mainstem bronchus near the main carina, with R DLT bronchial cuff edge seen at right

Positioning

Most VATS procedures (including robotic-assisted) are performed with the patient in the lateral decubitus position and the operating table flexed.

Some bilateral procedures (thymectomy, thoracic sympathectomy) may be performed with the patient supine. Oxygenation may be more problematic in the supine position during one-lung ventilation, as the lateral position offers the advantage that both ventilation and perfusion are greater in the dependent (ventilated) lung.

Maintenance and surgical considerations

Before beginning one-lung ventilation, the lungs are usually ventilated with 100% FiO2 in order to denitrogenate the lung that will be collapsed. Tidal volume to the ventilated lung should be reduced to approximately 5 ml/kg of ideal body weight, and adjusted to maintain peak airway pressure of less than 25-30 cmH20. A somewhat higher tidal volume may be possible during L-sided procedures, as the R lung has more than 50% of total lung capacity. PEEP may be added at a typical range of 5-8 cmH20 for the ventilated lung, with caution that excessive PEEP may reduce blood pressure and compress alveolar capillaries.

The choice of ventilatory mode is at the discretion of the anesthesiologist. Some experienced anesthesiologists prefer pressure-controlled ventilation, and others prefer volume control.

After the onset of one-lung ventilation, it is normal to see a decrease in SaO2 over the first 20-30 minutes. The process of hypoxic pulmonary vasoconstriction (HPV) is not instantaneous. If the SaO2 declines to an unacceptable level, additional PEEP may be added to the ventilated lung or CPAP applied to the operative lung. However, it should be noted that adding CPAP to the operative lung may obscure the surgeon's view to an unacceptable degree, and this technique should be used for the minimal time necessary. As HPV takes effect, the SaO2 often improves without intervention. During lung resection, surgical clamping of the lobar or pulmonary artery results in prompt improvement of V/Q mismatch and SaO2 rises accordingly.

Air may be added to the fresh gas inflow at the anesthesiologist's discretion after SaO2 has stabilized. If the patient has risk factors for acute lung injury such as previous chemotherapy with bleomycin, the FiO2 should be decreased as promptly as possible. With a properly positioned DLT, FiO2 as low as 35-40% may be tolerated with acceptable SaO2 around 90%.

The choice of maintenance technique for general anesthesia favors inhalation anesthesia over total intravenous anesthesia (TIVA). In addition to the beneficial bronchodilating effects of volatile anesthetics, both desflurane and sevoflurane have been found to suppress the alveolar proinflammatory effects of one-lung ventilation compared with TIVA.

Arrhythmias are not uncommon during VATS, but typically are self-limited if they are due to direct irritation of the heart by surgical instrumentation. If sustained arrhythmia requires treatment, it is important to bear in mind the association of amiodarone with acute pulmonary injury. Many thoracic surgeons will include metoprolol or diltiazem in postoperative orders for prevention of atrial fibrillation.

Restriction of IV crystalloid remains a cornerstone of intraoperative management. As previously noted, acute lung injury (ALI) is a feared complication of lung resection, and carries a high mortality rate if it progresses to full ARDS. ALI is defined as acute hypoxemia accompanied by radiographic pulmonary infiltrates without a clearly identifiable cause, occurring in the first 72 hours post surgery. In 1984, Zeldin and colleagues identified three major causative factors in the development of "post-pneumonectomy pulmonary edema", which we would now recognize as ALI or ARDS:  right-sided pneumonectomy, large perioperative fluid load, and high urine output.  At Memorial Sloan-Kettering, a retrospective review of more than 2000 lung resection cases revealed an overall ALI incidence of 2.5%. Mortality was 50% in the post-pneumonectomy patients, and 42% in the post-lobectomy patients. Review of causative factors once again showed perioperative fluid load (more than 3 liters in the first 24 hours) to be a significant risk factor, along with poor preexisting pulmonary function (decreased DLCO and FEV₁). Other risk factors include neoadjuvant chemotherapy, and/or radiation therapy.

No subsequent study has disproved the value of being conservative with fluid administration, especially crystalloid, during lung resection. Blood transfusion may be required in some cases, but carries the additional risk of transfusion-related acute lung injury (TRALI).

Emergence

Emergence from general anesthesia for VATS requires the usual precautions: complete reversal of muscle relaxants, adequate control of pain, and demonstration of satisfactory respiratory mechanics prior to extubation. In some cases where pulmonary function is poor and there are copious secretions in the large airways, it may be beneficial to change the DLT to a single-lumen ETT to allow bronchoscopy, bronchial lavage, and thorough suctioning before emergence.

It is always preferable to extubate the trachea in any case of lung resection, as postoperative mechanical ventilation increases the risk of developing a leak in the fresh bronchial staple line and creating a bronchopleural fistula. Deep vs. awake extubation is at the discretion of the anesthesiologist. Some anesthesiologists prefer to extubate with the patient in the lateral position to preserve the advantages of increased ventilation and perfusion to the nonoperative (dependent) lung.

Postoperative management

Disposition

Whether the patient needs intensive care in the postoperative period will depend on several factors: the magnitude of the surgical procedure, whether or not extubation is possible, any continuing need for invasive monitoring, and the patient's underlying risk factors. Some centers send post-VATS patients routinely to a non-ICU ward, where the nursing staff is experienced in the care of chest tubes, and continuous monitoring is available with pulse oximetry and capnography.

Pain management

Effective pain management utilizes a multimodal approach, including non-narcotic analgesics and regional techniques, to avoid respiratory depression and encourage early mobilization.

Potential complications

The potential complications and postoperative sequelae of VATS are variable depending on the exact surgical procedure:

• Acute lung injury
• Injury to airway from traumatic DLT insertion
• Arrhythmia, especially atrial fibrillation
• Anastamotic leak after esophagectomy; mediastinitis
• Hypotension as a result of inadequate volume replacement and/or epidural analgesia
• Persistent air leak; bronchopleural fistula
• Positioning injury
• Respiratory depression/failure
• Post-surgical bleeding
• Acute kidney injury