Friday, March 19, 2021

Thoracoscopic Lung Resection Case File

Posted By: Medical Group - 3/19/2021 Post Author : Medical Group Post Date : Friday, March 19, 2021 Post Time : 3/19/2021
Thoracoscopic Lung Resection Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 26
A 65-year-old Caucasian man presents to the anesthesia preoperative clinic for an evaluation in anticipation of a video-assisted thoracoscopic (VATS) resection of a right lower lobe squamous-cell carcinoma. His symptoms include shortness of breath after climbing two flights of stairs, and a chronic morning cough with yellow productive sputum.

His past medical history includes a smoking history of 1 pack per day for 40 years and chronic obstructive lung disease (COPD). He also has hypertension and a review of his medical record shows multiple blood pressure readings which were elevated. His only medication is amlodipine.

The patient is 70 in tall and weighs 70 kg. His vital signs include BP = 170/90 mm Hg, heart rate = 90 bpm, respiratory rate (RR) = 20 breaths per minute, and Temp = 97.2°F. His airway examination demonstrates a supple neck with full range of motion, a hyomental distance of 6 cm, and an airway classification of Mallampati 2. Scattered expiratory wheezes are audible on auscultation of his chest. The rest of his physical examination was unremarkable.

Preoperative tests include a complete blood count (CBC), chemistry- 7, coagulation profile, chest x-ray, and ECG. Pertinent findings on preoperative tests include hemoglobin = 12 (an Hct of 35). The rest of his preoperative tests are unremarkable.

➤ What pulmonary function tests may help to assess this patient’s surgical risk and why?

➤ What are the most important intraoperative concerns in a patient undergoing lung resection?

➤ Why is postoperative analgesia important in these patients?


ANSWERS TO CASE 26:
Thoracoscopic Lung Resection

Summary: This is a 65-year-old man with a 40-pack-year smoking history and a past medical history of hypertension and COPD being scheduled for a thoracoscopic resection of right middle lobe squamous cell carcinoma. Additional concerns found during anesthesia preoperative evaluation include poorly-controlled hypertension and mild anemia.

Pulmonary function tests: Since a vital capacity of at least three times the tidal volume is needed to produce an effective cough, pulmonary function tests (PFTs) can predict increase risk of postoperative pulmonary morbidity. PFTs are also useful to determine the degree of severity of his lung disease and to evaluate the degree of reversibility with bronchodilator treatment prior to proceeding with surgery. Predictors of perioperative morbidity include:

1. FEV1 < 2 L
2. FEV1/FVC < 0.5
3. Vital capacity (VC) <15 cc/kg
4. Arterial blood gas with hypoxemia and/or hypercarbia

If the FEV1/FVC value is low on the PFT, then this supports the diagnosis of COPD in this patient. Unlike patients with restrictive lung disease who will have a normal FEV1/FVC value, patients with obstructive lung disease will have a low FEV1/FVC due to a markedly low FEV1.

The three most important intraoperative concerns: (1) Maintaining hemodynamic stability, (2) maximizing oxygenation and maintaining adequate ventilation during one lung ventilation, and (3) avoiding overhydration of fluid replacements.

Importance of adequate analgesia: This allows patients to effectively perform incentive spirometry and enables the pulmonary toilet functions to clear airway secretions, both of which reduce atelectasis and thereby improve ventilatory function. Conversely, it is also important to avoid oversedating these patients, for essentially the same reasons.


ANALYSIS

Objectives
1. Identify preoperative anesthesia concerns as it pertains to patient undergoing surgery for lung resection.
2. Become acquainted with use of a double lumen tube, and some of the factors to consider when choosing a right-versus left-sided tube.


Considerations
This patient is an ASA-3, with poorly controlled hypertension, tobacco use, chronic obstructive lung disease (COPD), squamous-cell lung carcinoma, and anemia. The fact that he can climb two flights of stairs before developing shortness of breath indicates that he has a MET of > 6, indicating that he has an adequate cardiopulmonary reserve to undergo an intermediate risk procedure.

He has not had pulmonary function tests, and is currently not receiving bronchodilator therapy. A pulmonary function test (PFT) should be requested to determine severity of COPD and to determine if patient responds to bronchodilator treatment. If PFTs indicates good bronchodilator response, he should be referred to his primary care physician (PCP) to initiate bronchodilator treatment.

Since his surgery date is 2 weeks following the preoperative evaluation, he will also benefit from referral to his PCP for optimization of his blood pressure prior to surgery. Patients with long-standing uncontrolled or poorly controlled hypertension will have a right shift of the cerebral autoregulatory curve, and as a result, require a higher blood pressure to maintain adequate cerebral perfusion. Hemodynamic liability, especially acute hypotension, may occur with general anesthesia and predisposes these patients to a higher risk of ischemic strokes during surgery.

It is important to ensure that cross-matched blood is available during surgery since patient has mild anemia and is undergoing a procedure with potential for large blood loss. He should give consent for general anesthesia with invasive (arterial and CVP) monitoring, possible thoracic epidural catheter placement, and blood transfusion therapy.


APPROACH TO
Thoracoscopic Lung Resection

DEFINITIONS
VATS (VIDEO-ASSISTED THORACOSCOPIC SURGERY): A procedure involving the use of advanced video technology, computers, and high-tech electronics to perform surgeries within the chest.
DOUBLE LUMEN TUBE: A specialized endotracheal with two separate ventilation lumens .
UNIVENT: A single lumen endotracheal tube with a build-in endobronchial blocker .
WEDGE RESECTION: A surgical procedure to remove a triangle-shaped slice of tissue.
LOBECTOMY: A surgical procedure to remove an entire lobe of an organ.
PNEUMONECTOMY: An entire resection of a lung.
LEFT LATERAL DECUBITUS POSITION: Lateral position during surgery in which the patient’s body will be lying on the left side.


CLINICAL APPROACH
In 2009, the National Cancer Institute reports 219,440 new cases of lung cancer and 159,390 deaths from lung cancer in the United States. These numbers include small-cell- and non–small cell-lung carcinomas. The cancer mortality rate is usually expressed as the number of deaths due to cancer per 100,000 population. That is, 

Mortality Rate = (Cancer Deaths/Population) × 100,000

The overall outcome of patients with lung cancer depends on early detection and treatment. The benefits of preoperative optimization must be weighed against the risks of delaying the early surgical treatment of his lung cancer. COPD is common in this population, and preoperative optimization reduces the incidence of pulmonary complications after surgery. Similarly, preoperative blood pressure control can decrease the incidence of hemodynamic lability and incidence of stroke during the perioperative period.

The preparation for pulmonary resection includes cross-matched blood, which is immediately available because of the potential of large blood loss during surgery. This is particularly true in the cancer patient, who may be anemic. It is preferable to place a large-bore (preferably 16 gauge or larger) peripheral intravenous (PIV) in the arm on the operative side. Since patients are placed in the lateral decubitus position (nonoperative side down) during surgery, there is a potential for vascular compression of the upper extremity on the nonoperative side (the “down” arm). Should vascular compression of the “down” arm occur due to a position related problem, then an i.v. placed in the “down” arm would be rendered useless during surgery. This is the reason why the PIV is recommended to be placed in the upper extremity on the operative (“up”) side.

After the i.v. is placed, the placement of an arterial catheter will allow a room air blood gas to be sent prior to induction of anesthesia. Additional monitors for this patient include: (1) arterial line and (2) central venous pressure (CVP) monitoring. The strongest clinical indication for an arterial line placement in this case is to provide serial sampling of arterial blood gas in order to monitor arterial oxygen and carbon dioxide levels during surgery. Room air blood gas is also useful in determining the degree of severity of lung disease, and will be invaluable later in the case as one lung ventilation is established. A right thoracoscopic surgical approach requires that this patient be placed in a left lateral decubitus position (left side down and right side up). Placing the arterial line in the “anatomically down” arm will allow early detection of axillary artery and brachial plexus compression during surgery. A central line is usually placed in order to provide rapid access for fluid resuscitation and to provide close monitoring of central venous filling pressures in order to avoid overhydration during surgery. Besides standard monitors and equipments, additional equipment should include a fiberoptic bronchoscope, a CPAP device, a vascular clamp to facilitate one lung ventilation, a double lumen tube, and in case of difficulty intubation, a standard endotracheal tube with a stylette.

With the possible exception of endoscopic procedures, surgical procedures on the lung require general endotracheal anesthesia. If the likelihood of an open thoracotomy is high, then patients will benefit from the preoperative placement of a thoracic epidural for postoperative pain control. The epidural may also be used during the intraoperative period to decrease intravenous use of narcotics, and therefore, facilitate early endotracheal extubation of patients at termination of surgery. If a thoracic epidural catheter is considered and there are no contraindications, then it is preferred to place the thoracic epidural catheter between levels of T4 and T7 prior to the induction of general anesthesia. Patient cooperation during thoracic epidural catheter placement is essential. Therefore, at a maximum, light sedation can be provided to facilitate this procedure.

Once the proper surgery protocol including patient identification and surgical marking is completed, the patient is transported into the operating room. Following the application of standard monitors (ECG, noninvasive blood pressure [NIBP], pulse oximetry) and connection of arterial line for continuous blood pressure monitoring, 100% oxygen is administered prior to the induction of general anesthesia.

Unlike routine general anesthesia cases, one lung ventilation is needed to maximize the surgical exposure when using a thoracoscopic approach. One lung ventilation can be achieved by using a double-lumen endotracheal tube (Figure 26–1) or a single-lumen endotracheal tube with a built-in endobronchial

Double-lumen endotracheal tube

Figure 26–1. Double-lumen endotracheal tube. The most distal tip of the doublelumen tube is always the bronchial lumen. A left pneumonectomy will require a right-sided double-lumen tube for one lung ventilation.Otherwise, a left-sided doublelumen tube is preferred by most since it is easier to position than a right-sided doublelumen tube.

Univent endotracheal tube

Figure 26–2. Univent endotracheal tube. This is a single-lumen endotracheal tube with a built-in endobronchial blocker. Using fiberoptic bronchoscopy, the endobronchial blocker can be positioned into the desired bronchus to achieve one lung ventilation. The advantage of the Univent tube is that it is easier to place than the double lumen tube.The disadvantages are that suctioning of the nonventilated lung cannot be achieved and continuous positive airway pressure (CPAP) cannot be applied during one lung ventilation.

blocker such as the Univent tube (Figure 26–2). The advantages of a doublelumen endotracheal tube include better lung isolation, the ability to provide continuous positive airway pressure (CPAP), and better access for endotracheal suctioning of airway secretions. For patients with a difficult airway and need one lung ventilation, a Univent tube may offer the advantage of easier endotracheal insertion than a double-lumen endotracheal tube.

Double-lumen endotracheal tubes are available in both left-sided and right-sided versions and in 28F, 35F, 37F, 39F, and 41F. Most male adult tracheas accommodate a 39F or 41F DLT, while most female adult tracheas accommodate a 35F or 37F. Though it is actually easier to intubate the right mainstem bronchus due to its larger size and less acute angle with the trachea, it is very difficult to align the small orifice made for the right upper lobe with the right upper lobe bronchus, often leading to right upper lobe atelectasis. Although counterintuitive, a left-sided double lumen tube is actually easier to position for one lung ventilation than a right-sided double lumen tube, and obviously does not carry the risk of right upper lobe collapse. A left-sided double lumen tube is preferred by most anesthesiologists, unless the patient is undergoing a left pneumonectomy (which includes bronchial resection), and therefore requires a right-sided double lumen tube.

If the patient does not appear to have a difficult airway, general anesthesia is induced, and laryngoscopy performed to visualize the vocal cord for direct placement of the double-lumen tube. Once the trachea is intubated, ventilation is confirmed by listening for presence of bilateral breath sounds and by detecting the presence of end-tidal carbon dioxide using capnography. In addition to auscultation, the proper placement of the double-lumen tube is confirmed by fiberoptic bronchoscopy through the tracheal lumen of the double-lumen tube. The trachea and carina are used as a marker to identify the carina, which in turn identifies the right and left mainstem bronchi. Once the carina is identified, it is interesting to identify the anterior and posterior parts of the trachea. The posterior trachea does not have tracheal rings: rather, it consists of soft tissue with a smooth surface. Looking straight at the carina, if tracheal rings are noted on the anterior part of the bronchoscope screen, then the right main bronchus will be located on the right side of the screen. If the bronchial lumen of the double-lumen tube has already advanced into the left main bronchus (a desirable outcome if one is using a left double-lumen tube), the left mainstem bronchus may not be visualized. A left endobronchial intubation is also verified by advancing the fiberoptic bronchoscope through the tube’s tracheal lumen, into the right mainstem bronchus. From the carina, the visualization of three bronchial lumens distal to the main bronchus correctly identifies the right main bronchus. The correct placement of the double-lumen tube in the left main bronchus is confirmed by visualization of bronchial lumen placed in the left main bronchus, and visualization of a slight herniation of the bronchial cuff into the trachea after it is inflated with 3 cc of air.

Once the double-lumen tube is secured, the patient’s neck is prepped for central line placement. Unless otherwise contraindicated, it is recommended to place the central line on the same side of the surgical procedure. An iatrogenic pneumothorax is always possible following central line placement. So if it occurs, it’s preferable that the pneumothorax be on the operative side where the chest is open anyway, and where a chest tube will be placed.

The next step is to position the patient into the lateral decubitus position. During position, it is important to keep the neck in a neutral position, and to ensure that the eyes and ears are free from being compressed. A chest roll is placed under the arm distal to the left axilla, making sure brachial plexus and axillary vasculature are not being compressed. The right arm is placed on a specialized arm board (sometimes called the “airplane”) to allow adequate surgical exposure of the right chest. It is important to make sure that all pressure points are well padded during patient positioning. After the patient is well positioned, the position of the double-lumen tube is confirmed one more time. This can be achieved by listening over the lung fields during one lung ventilation, and by using the fiberoptic bronchoscope.

During surgery, both lung fields are ventilated until the surgeon requests one lung ventilation. Take note of the tidal volume and peak airway pressure during normal ventilation. One goal of one lung ventilation is to provide nearly the same tidal volume and peak airway pressure as with double lung ventilation, in order to maintain adequate oxygenation and ventilation and avoid barotrauma. When one lung ventilation is requested, a clamp is applied to the tracheal lumen of the DLT. This will cease ventilation to the right lung, produce a quiet surgical field, and allow better surgical exposure. Ventilation and oxygenation to the left lung is maintained through the left bronchial lumen of the double-lumen tube. It is important to note (and document) the tidal volume, peak airway pressure, end-tidal carbon dioxide tension, and pulse oximetry, both prior to clamping the tracheal lumen, as well as after. Adjustments to ventilator settings maintain oxygenation and ventilation, and avoid the barotrauma caused by high-peak airway pressures during one lung ventilation. Whether to use a high FiO2 (1.0) or a lower FiO2 remains controversial. Clearly, maintenance of an acceptable PaCO2, One concern of using a high FiO2 during surgery, especially with one lung ventilation, is that it causes absorption atelectasis, potentially increasing the degree of shunting caused by the collapsed alveoli. The concept of high FiO2 causing oxygen toxicity is a theoretical concern, unless the patient has been previously exposed to chemotherapeutic agents such as bleomycin or busulfan.

Approximately 10 to 15 minutes after initiation of one lung ventilation, an arterial blood gas is sampled to monitor arterial oxygen and carbon dioxide tensions. One major goal during OLV is to keep the PaO2 between 150 to 200 mm Hg. If PaO2 falls below 150 mm Hg, continuous airway pressure (CPAP) can be applied to the nondependent (nonventilated) lung and positive endexpiratory pressure (PEEP) can be added to the dependent (ventilated) lung to improve oxygenation.

After the right middle lobectomy is completed, the surgeon will request to return to two lung ventilation. After 10 to 15 minutes on two lung ventilation, another arterial blood gas is obtained to determine if oxygenation and ventilation is significantly affected after lobectomy. Optimization of oxygenation and ventilation during this time is important if patient is to be considered for extubation at termination of surgery. Maneuvers such as endotracheal suctioning to remove airway secretions and nebulization with bronchodilator agents may help to improve oxygenation prior to extubation. If extubation cannot be achieved at the end of surgery, once the patient is moved to a supine position, the double-lumen tube is replaced by a single-lumen endotracheal tube.

If a thoracic epidural catheter is placed for this patient, this epidural can be used to supplement anesthesia and analgesia and decrease intravenous narcotic administration during surgery. This allows the patient to be comfortable and yet awake enough to respond to coaching deep breathing exercises. Hypotension is a concern with intraoperative use of thoracic epidural catheters, since infusions or boluses of these catheters using dense concentration local anesthetic may result in hypotension. A dilute epidural regimen using 0.0625% to 0.125% of bupivacaine and 2 to 5 μg/cc of fentanyl infusing at 5 to 10 cc/h started just prior to surgical incision may be considered as an alternative. Providing adequate analgesia so that patient can be comfortable to perform deep incentive spirometry and to produce an effective cough to clear airway secretions is essential during the postoperative period. These maneuvers will help reexpand the lungs, decrease atelectasis, and improve lung function after surgery.

Another concern during lung resection surgery is avoiding excessive fluid resuscitation. Central venous pressure monitoring can help guide fluid management during this case, although the absolute number provided by the CVP is not necessarily accurate in either the lateral position, or in the presence of an open chest. Excessive fluid resuscitation during lung resection surgery, especially lobectomy and pneumonectomy, predisposes patients to an increase risk of right heart failure and cardiac dysrhythmias, especially atrial fibrillation, during the postoperative period. Indeed, during lung surgery, even normal amounts of fluid are often considered to be “excessive.”


Comprehension Questions

26.1. What is the smoking history of a patient who smokes 2 packs per day for 50 years?
A. 40 pack years
B. 50 pack years
C. 80 pack years
D. 90 pack years
E. 100 pack years

26.2. A vital capacity of at least how many times the vital capacity is needed to produce an effective cough?
A. One
B. Two
C. Three
D. Four
E. Five

26.3. Which of the following values on the pulmonary lung test is useful in differentiating between restrictive and obstructive pulmonary disease?
A. FVC
B. FEV1
C. FEV1/FVC
D. RV/TLC
E. MVV

26.4. Which of the following values will predict an increase risk of postoperative pulmonary complications?
A. PaO2 > 80 (room air arterial blood gas)
B. PCO2 > 50
C. FEV1 > 2 L
D. FEV1/FVC > 0.5
E. VC > 15 cc/kg

26.5. Which of the following maneuvers can help improve oxygenation during one lung ventilation?
A. Increasing the concentration of an inhaled anesthetic to aid bronchodilation
B. Adding mild suction to the nondependent (nonventilated) lung
C. Adding PEEP to nondependent (nonventilated) lung
D. Adding PEEP to the dependent (ventilated) lung

26.6. Which of the following tests would be useful in determining the surgical risk for a patient with COPD, complaining of severe shortness of breath after one flight of stairs, and who has a new left bundlebranch block on the preoperative ECG?
A. Exercise stress test
B. Pulmonary function test
C. Chemical stress test
D. Echocardiography


ANSWERS
26.1. E. Total pack years of smoking is calculated by multiplying the number
of packs the patient smokes a day with the total number of years
smoked (2 packs/day × 50 years = 100 pack years).

26.2. C. A vital capacity of at least three times the tidal volume is needed
to produce an effective cough.

26.3. C. A low FEV1 is indicative of airway obstruction. However, the ratio of FEV1/FVC is more useful in differentiating between restrictive and obstructive pulmonary disease. This ratio is normal in restrictive lung disease and low in obstructive lung disease. Both FEV1 and FVC decrease with restrictive lung disease. As a result, the FEV1/FVC ratio will be normal. FEV1 is markedly decreased with obstructive lung disease. As a result, the FEV1/FVC ratio will be low.

26.4. B. The presence of hypercarbia on an arterial blood gas (ABG) is predictive of increased postoperative pulmonary complications. Other predictors of postoperative pulmonary complications include: (1) an FEV1 lower than 2 L, (2) the ratio of FEV1/FVC of less than 0.5, (3) the VC of less than 15 cc/kg, and (4) the presence of hypoxemia on the arterial blood gas.

26.5. D. Adjusting the minute ventilation, respiratory rate, and tidal volume help improve oxygenation during one lung ventilation. In addition, PEEP can be applied to the dependent (ventilated) lung and CPAP can be applied to the nondependent (nonventilated) lung to improve oxygenation during one lung ventilation. With respect to answer C, positive end-expiratory pressure (PEEP) cannot be added to the nondependent lung because the nondependent (operative) lung is not ventilated, and PEEP can only be added to a ventilated circuit. Increasing the concentration of an inhaled anesthetic to aid bronchodilation is only helpful if the patient is wheezing. Adding mild suction to the nondependent (nonventilated) lung will not affect oxygenation.

26.6. D. The presence of a new left bundle-branch block (LBBB) on the preoperative ECG may indicate cardiac disease. Since this patient has low functional capacity due to shortness of breath with exertion, it is important to determine if his dyspnea is due to COPD and lung cancer or cardiac disease caused by myocardial ischemia. A chemical stress test (myocardial perfusion scan and dobutamine stress echo) will help to determine if dyspnea is due to cardiac or pulmonary pathophysiology. Shortness of breath with exercise can indicate a severely depressed systolic myocardial function, and stress-induced ischemia.


Clinical Pearls
➤ It is important to thoroughly evaluate the patient undergoing lung surgery to determine the risk for anesthesia and surgery.
➤ Early detection and treatment of lung cancer offers better outcome. If time permits, then patient’s medical problems need to be optimized prior to surgery.
➤ For patients scheduled for lung resection surgery, especially with lobectomy and pneumonectomy, it is important to determine whether or not the patient has enough pulmonary reserve to undergo the surgical procedure. Pulmonary function tests, room air arterial blood gas, split lung function test, and pulmonary artery balloon-occlusion test can help predict patient’s postoperative outcome after lung resection surgery, and are especially important prior to a pneumonectomy.

References

Barash PG, Cullen BF, Stoelting RK. Clinical Anesthesia. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006. 

National Cancer Institute. www.cancer.gov. 2009. 

Stoelting RK, Miller RD. Basics of Anesthesia. 4th ed. New York, NY: Churchill Livingston; 2000.

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