Thoracic WebEx - dr. Raffel

Thoracic webex

Transcript

1. Brian Raffel, DO Department of Anesthesiology Thoracic Anesthesia Webex
2. Thoracic Anesthesia Webex Case A 60-year-old man has suffered from cough, intermittent hemoptysis, and weight loss for 2 months. He has smoked one pack of cigarettes per day for 40 years. A chest radiograph 1 month ago revealed a right middle lobe infiltrate that was treated with antibiotics without clinical improvement. Subsequent evaluation revealed a carcinoma. He is now scheduled for fiberoptic bronchoscopy, mediastinoscopy, and possible video-assisted thoracoscopic (VATS) lobectomy.
3. Thoracic Anesthesia Webex The patient has a long history of cigarette smoking. What is the significance of this finding?
4. Thoracic Anesthesia Webex • Cigarette smoking still remains the leading cause of lung cancer in the United States. • Tobacco exposure leads to chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis and emphysema, and is strongly associated with an increased incidence of stroke, myocardial infarction, and cancer (lung, oral cavity, larynx, and esophagus). • Pulmonary hypertension from chronic hypoxemia and subsequent cor pulmonale may also occur. • Eight percent to 17% of patients with lung cancer who are scheduled for surgical resection are still smoking at the time of surgery. Current tobacco use increases the risk of postoperative respiratory failure, pneumonia, aspiration, air leak, atelectasis, as well as 1-year mortality. • Preoperative smoking cessation is strongly recommended, but it is unclear how long is needed to see a significant reduction in postthoracotomy complications. • Carboxyhemoglobin concentrations decline substantially within 12 hours of smoking cessation.
5. Thoracic Anesthesia Webex How would you evaluate the patient prior to surgery?
6. Thoracic Anesthesia Webex • Preoperative evaluation should investigate cardiac risks in case of perioperative cardiac disease, lung function, gas exchange capacity, and cardiopulmonary reserve. • The first step should include a complete history, physical examination, and laboratory tests (e.g., complete blood count, basic metabolic profile, coagulation study, electrocardiogram, chest radiography, and computed tomographic imaging). • An abnormal exercise tolerance, such as the inability to climb at least three flights of stairs or walk for 6 minutes, may indicate a patient with compromised cardiorespiratory function and unable to tolerate the stress of anesthesia and surgery. • In addition to routine preoperative testing, patients scheduled for lung resection usually undergo pulmonary function testing to help define the relative risks of the planned resection.
7. Thoracic Anesthesia Webex • Respiratory mechanics: evaluated via forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and the ratio between residual volume and total lung capacity (RV/TLC). Flow–volume loops may be helpful to document the location of the obstruction (small vs. large airway) and its severity. Post bronchodilator FEV1 and FEV1/FVC paired with clinical symptoms are used to determine the severity of COPD. • Cardiopulmonary reserve: evaluated with maximal oxygen uptake (VO2 max), stair climbing, 6-minute walk, and shuttle walk. VO2 max is the gold standard for aerobic capacity and cardiorespiratory fitness. Patients with VO2 max value less than 10 mL/kg/min are at increased risk for postoperative morbidity and mortality. • Lung parenchymal function: Diffusing lung capacity for carbon monoxide (DLCO), partial pressure of oxygen in the arterial blood (PaO2), and partial pressure of arterial carbon dioxide (PaCO2). Predicted postoperative DLCO and FEV1 less than 40% to 44% are significant independent predictors for increased postoperative morbidity and mortality.
8. Thoracic Anesthesia Webex What are the pulmonary function guidelines that indicate an increased risk for morbidity and mortality?
9. Thoracic Anesthesia Webex • The reported mortality from lung resection is between 2% and 4%, mainly as a result of pneumonia, respiratory failure, bronchopleural fistula, empyema, and pulmonary embolism. Respiratory insufficiency occurs in approximately 5% of patients following lung resection and is associated with a 50% mortality rate. • Advanced age and the increased incidence of concomitant nonpulmonary disease seem to contribute to this outcome. • An increased risk of postoperative complications can be predicted by the following: • Spirometry: Spirometric parameters, such as FEV1/FVC ratio and FEV1 (reflective of the degree of airway obstruction), as well as static volumes (such as inspiratory and TLC), are used to define the severity of COPD. Several studies have indicated a strong correlation between predicted postoperative FEV1 and DLCO and a respective increase in morbidity and mortality, especially for open procedures and extensive dissection. Concerning values are summarized in • Arterial blood gases: Historically, hypercapnia (PaCO2 greater than 45 mm Hg) was considered an exclusion criterion for lung resection. However, no independent correlation has been found with an increased mortality. Patients who are hypercapnic often have a low predicted postoperative FEV1 and an abnormal exercise capacity, which preclude surgery. Preoperative hypoxemia (PaO2 less than 50 mm Hg, and percentage of available hemoglobin saturated with oxygen [SaO2] less than 90%) has been associated with an increased risk of postoperative complications. Other factors influencing outcome include patient comorbidities and functional status, the extent and location of the proposed surgical resection, and whether the patient has undergone preoperative induction chemotherapy.
10. Thoracic Anesthesia Webex How would you premedicate, monitor, and anesthetize this patient?
11. Thoracic Anesthesia Webex • Parenteral premedication before transport to the • If not contraindicated, a small intravenous dose (0.2 mg) of glycopyrrolate can be considered as an antisialagogue, particularly in patients who smoke. Cervical mediastinoscopy is now reserved for small lymph nodes not readily accessible via EBUS. • During mediastinoscopy, intermittent compression or occlusion of the innominate artery can occur. • Therefore, the blood pressure cuff should be placed on the left arm and the pulse oximeter on the right hand. • In the case of innominate artery compression, a damping of the pulse oximetry trace will be evident while blood pressure measurements will remain accurate. • Arterial access is not routinely used for this procedure unless the patient has clinical indications for continuous hemodynamic monitoring. • Body temperature should be monitored, and a warming blanket applied. • Propofol is usually used for induction of general anesthesia followed by rocuronium, vecuronium, or cisatracurium to facilitate tracheal intubation via a single-lumen endotracheal tube (ETT). • Anesthesia can be maintained with a potent inhalational agent in oxygen or air, if oxygen saturation tolerates it. • Fentanyl often provides sufficient analgesia for the procedure. • Nonsteroidal anti-inflammatory drugs (NSAIDs) are used by some providers as adjuvant agents; nevertheless, the potential for bleeding in a closed space in ambulatory patients should be considered.
12. Thoracic Anesthesia Webex The decision was made to proceed with a thoracoscopic right middle lobectomy. How would this alter your management?
13. Thoracic Anesthesia Webex VATS • Patients are positioned in the lateral decubitus and the bed maximally flexed. • The upper arm is suspended and sometimes abducted away from the chest cavity. Unnatural positioning with stretching of the brachial plexus can lead to potentially permanent damage. • Optimal lung isolation and collapse are needed to enhance lung visualization • Intravenous access should be placed before final positioning and draping because patient access will be limited. • An arterial line (in the dependent radial artery) may be beneficial in patients undergoing robotic procedures for hemodynamic monitoring, although not uniformly regarded as necessary for lung
14. Thoracic Anesthesia Webex What are the indications for single-lung ventilation and how is it accomplished?
15. Thoracic Anesthesia Webex • Several techniques can be used to provide single-lung ventilation, including DLTs, bronchial blocking catheters passed outside or inside the ETT, ETTs with incorporated bronchial blocking catheters (Univent® ETT, Teleflex, Triangle Park, NC), or conventional ETTs placed endobronchially. • Currently, DLTs remain the most common method for achieving lung isolation. • Sizes: 35, 37, 39, and 41 French and two sides (right and left). • General rule is that average-sized Caucasian men usually accommodate a 39-French and average sized women a 37-French.
16. Thoracic Anesthesia Webex What are the contraindications to the use of double-lumen endotracheal tubes (DLTs)?
17. Thoracic Anesthesia Webex Placement of a DLT should be carefully considered in the following situations: • Patients whose upper airway anatomy may preclude safe insertion of the tube (recessed jaw, prominent teeth, bull neck, anterior larynx, mandibular surgery, and neck radiation) • Patients with lesions present somewhere along the pathway of the tube that could be traumatized, such as airway stricture or endoluminal tumors • Small patients for whom a no. 35 French tube is too large to fit comfortably through the larynx • Critically ill patients who have a single-lumen tube already in place and who cannot tolerate cessation of mechanical ventilation and positive end-expiratory pressure (PEEP) for a short period of time Under these circumstances, single-lung ventilation can be achieved via an endobronchial blocker. Endobronchial placement of a single- lumen tube for lung isolation is an alternative but suboptimal option. The tip of the ETT can cause direct distal airway trauma, whereas significant airway compression with potential mucosal ischemia may occur if the cuff bulges at carina. When placed on the right side, the right upper lobe can also be occluded by the cuff of the tube, preventing the ability to ventilate.
18. Thoracic Anesthesia Webex Would you use a right- or left-sided DLT?
19. Thoracic Anesthesia Webex • A left-sided DLT is generally preferable for most procedures due to its margin of safety. • The left mainstem bronchus is much longer than the right • The variable origin of the right upper lobe (1.5 to 2.0 cm below carina) may complicate maintaining a good placement of a right-sided tube. • A right-sided DLT is indicated in the case of pathology of the left mainstem bronchus, such as large exophytic lesions, significant bronchial stenosis, tracheobronchial disruption, endobronchial stent, and distortion by an adjacent tumor or a thoracoabdominal aneurysm. • Other indications include left pneumonectomy, sleeve resection, or lung transplantation to avoid the presence of a “foreign body” in the surgical field that could be included in the staple line or prevent suturing of the donor lung.
20. Thoracic Anesthesia Webex How do you know that the tube is in the correct position?
21. Thoracic Anesthesia Webex • Recommended insertion techniques for a DLT include direct laryngoscopy followed by fiberoptic guidance in the appropriate mainstem. • Blind insertion is not recommended due to the potential of airway injury. • Auscultation alone is unreliable to confirm the position of a double-sided lumen due to a possible decrease in breath sounds, especially in patients with COPD. • The position of the device should be reconfirmed once the patient is in the lateral decubitus prior to lung collapse. • During bronchoscopy, the tracheal cartilaginous rings are anterior and the tracheal membrane is posterior. • When properly positioned, the upper part of the blue endobronchial cuff is visualized just below the tracheal carina in the left mainstem bronchus • The bronchoscope should also be inserted in the bronchial lumen to evaluate the distance between the tip of the tube and the distal bifurcation of the bronchus.
22. Thoracic Anesthesia Webex How will systemic oxygenation be monitored during single- lung ventilation?
23. Thoracic Anesthesia Webex Pulse oximetry is still the hallmark for monitoring arterial oxygenation during lung Resection. Cerebral oximetry has recently become a popular monitor of brain perfusion during thoracic and cardiac anesthesia.
24. Thoracic Anesthesia Webex The patient was placed in the lateral decubitus position. Describe the effects of lateral positioning on pulmonary blood flow.
25. Thoracic Anesthesia Webex The patient was placed in the lateral decubitus position. Describe the effects of lateral positioning on pulmonary blood flow.
26. Thoracic Anesthesia Webex In both upright and supine positions, the right lung receives approximately 55% of the total blood flow, whereas the left lung receives the remaining 45%. In the lateral decubitus position, gravity causes a vertical gradient in blood flow distribution. Therefore, perfusion of the dependent lung is significantly greater than the nondependent counterpart. When the right lung is nondependent, it receives 45% of the total blood flow while 55% perfuses the dependent left lung. When the left lung is nondependent, it receives 35% of the total blood flow, while right lung receives 65%. Therefore, the average blood flow of the nondependent lung is approximately 40% of the total blood flow with the dependent lung being perfused with the remaining 60%
27. Thoracic Anesthesia Webex What is hypoxic pulmonary vasoconstriction (HPV)?
28. Thoracic Anesthesia Webex • HPV is an autoregulatory mechanism to prevent ventilation/perfusion mismatch and improve arterial oxygenation. • Proposed mechanisms include an increase in reactive oxygen species in the pulmonary arterial smooth muscle, activation of redox- based oxygen sensors, and an increase in intracellular calcium. • HPV is triggered by a decrease in PaO2 within the lung from low FIO2, hypoventilation, or atelectasis. • The selective increase of vascular resistance in the hypoxic parenchyma diverts blood away to the better ventilated normoxic lung, decreasing the amount of shunt flow. • This is a biphasic response that starts within 15 to 30 minutes from lung collapse, culminates at 120 minutes, and takes hours to reverse after normoxia is restored. • Recommendations to decrease reexpansion injury include reinflating the collapsed lung with less than 100% FIO2 as well as using protective lung strategies. The lowest FIO2 possible is also recommended.
29. Thoracic Anesthesia Webex What are the effects of anesthetic agents on HPV and their clinical implications?
30. Thoracic Anesthesia Webex • Any drug that causes vasodilatation may inhibit hypoxic vasoconstriction. • Several clinical studies have failed to demonstrate a decrease in HPV during single-lung ventilation and total intravenous anesthesia. • Intravenous anesthetics, such as thiopental, ketamine, morphine, and fentanyl have no direct effect on HPV. • In contrast,inhalational anesthetics have been shown to inhibit HPV in a dose-related fashion but usually at concentrations much higher than used clinically. • There is no good evidence that neuroaxial blockade affects HPV, unless causing a decrease in cardiac output or systemic vasodilatation.
31. Thoracic Anesthesia Webex How could you improve oxygenation during single-lung ventilation?
32. Thoracic Anesthesia Webex When hypoxia occurs during single-lung ventilation, the goal is to optimize the match between ventilation and perfusion on the dependent lung or increase the amount of oxygen in the shunted blood of the collapsed lung. Ventilated lung a. Optimize ventilation • Use 100% oxygen. • Check the position of the DLT with a fiberoptic bronchoscope. • Ventilate manually to determine whether higher or lower tidal volumes or inspiratory pressures are beneficial. • Set minute ventilation to maintain Paco2 at 40 mm Hg (hypocapnia may inhibit HPV in the nondependent lung, whereas hyperventilation may increase airway pressure and promote blood flow to the nonventilated lung). • Apply 5 cm H2O of PEEP • Increase PEEP as needed at expense of Venous Return • Use two-lung ventilation intermittently. b. Increase perfusion • Selective vasodilators (inhaled nitric oxide, inhaled prostacyclin PGI2)
33. Thoracic Anesthesia Webex Collapsed lung a. Oxygenate shunt blood: A variety of approaches have been described but must be carefully considered for minimally invasive procedures because most involve some degree of lung reexpansion and therefore may affect surgical visualization. • Insufflate oxygen continuously: A flow of about 3 L per minute allowed to freely circulate will often increase arterial oxygen saturation 3% to 4%. • Intermittent single breath with oxygen • Partially reexpand the nonventilated lung then keep the lumen side closed. • Apply continuous CPAP. • Differential CPAP to the collapsed lung and PEEP to the ventilated lung has been described but is rarely necessary and generally impractical for VATS procedures. • High-frequency ventilation to the nonventilated lung b. Decrease the shunt • Use drugs to augment HPV (phenylephrine, norepinephrine).. • Clamp lobar vessels or the pulmonary artery of the nonventilated lung temporarily (rarely necessary).
34. Thoracic Anesthesia Webex Why is it important to control postoperative pain? How would you achieve this?
35. Thoracic Anesthesia Webex Adequate postoperative analgesia is important not only for patient comfort but also to minimize pulmonary complications, allowing the patient to breathe deeply, cough effectively, and ambulate. • Thoracic Epidural • Systemic Opioids • Intercostal and Paravertebral Nerve Block • Cryoanalgesia