General Thoracic Surgery





The focus of this chapter is on concepts in the perioperative period germane to general thoracic surgery. Areas that will be covered include preoperative pulmonary reserve assessment, prevention of postoperative pulmonary complications with emphasis on smoking cessation and the current evidence for use of incentive spirometry, prevention of arrhythmia, and a comprehensive assessment of the role for enhanced recovery protocols in thoracic surgery. Although the majority of the discussion centers on lung resection, the principles detailed in this chapter can be applied to the perioperative aspects of any general thoracic surgical procedure.


Before ordering diagnostic tests to assess surgical risk, the following should be carefully considered:



  • 1.

    Will the test results sufficiently alter the estimate of surgical risk derived from history & physical (H&P), and will the surgery be canceled, postponed, or changed in nature?


  • 2.

    Will the test results lead to possible changes in the perioperative management to help improve outcomes?


  • 3.

    What is the cost of the test?


  • 4.

    What is the risk of the test itself?



Preoperative Pulmonary Function Assessment


Lung function, the ability of the lungs to provide oxygen to the body and to remove carbon dioxide, is a critical factor in a patient’s perioperative well-being. Assessment of the pulmonary reserve is an important element of risk stratifying and determination of eligibility of patients for lung resection. The comprehensive assessment of pulmonary reserve to determine eligibility for lung resection encompasses three areas: pulmonary function tests, exercise capacity, and predicted postoperative value (amount of lung reserve after resection).


Pulmonary Function Tests


Spirometry measures the volumes that an individual can breathe in and out, whereas diffusion capacity measures the functional ability, specifically measuring gas diffusion within the lungs (ability of exchange of CO 2 for O 2 ). According to guidelines from the European Respiratory Society (ERS) and European Society of Thoracic Surgeons (ESTS), both spirometry (specifically FEV1 [forced expiratory volume in 1 second]) and the assessment of the diffusion capacity of the lungs (DL CO ) are the most important for assessing preoperative pulmonary function status.


Although prior guidelines from the American College of Chest Physicians (ACCP) in 2007 and the British Thoracic Society (BTS) were selective about use of DL CO assessment, numerous recent studies have demonstrated that reduced DL CO levels constitute an independent risk factor for increased mortality and perioperative complications, even in patients with normal FEV1.


Assessment of Pulmonary Function Tests (PFTs)





  • If both FEV1 and DL CO are greater than 80% of predicted levels, no further testing is needed.



  • When at least one of the parameters (FEV1 or DL CO ) is less than 80% of predicted level, the next step is to assess the patient’s exercise capacity.



Exercise Capacity


The most precise test amongst the exercise assessments is the cardiopulmonary exercise test (CPET). CPET may be performed on a treadmill or on a cycloergometer. The measurement of exercise capacity is peak oxygen uptake expressed by the VO 2 max parameter. Reduced VO 2 max results in an increased risk of postresection complications. Specific values of importance:




  • Greater than 75% predicted value or > 20 mL/kg/min: safe to proceed to resection;



  • Less than 65% predicted value or < 16 mL/kg/min: resection not recommended.



Criticism of CPET has been directed at both the difficulty of doing the test and the exorbitant cost. Other low-cost methods for assessment of exercise capacity include the 6-minute walk test (6MWT), shuttle walk test, and stair climbing test.


The distance covered during 6MWT has best been correlated with VO 2 values in lung transplantation patients but has less correlation with complications after lung resection. During the shuttle walk test, patients walk between two points 10 meters apart and increase their pace (speed) by a signal during the test. The distance covered during this test correlates well with VO 2 max for the majority of patients. Those patients who walk less than 250 meters are at significantly increased risk of complications after lung resection.


During the stair climbing test, patients climb flights of stairs, with assessment of both distance and number of floors. Patients who climb less than three floors are twice as likely to suffer from complications, have 13-fold increased mortality, and 2.5-fold increased costs of treatment, compared with those who are able to climb five floors of stairs. All patients who are able to climb more than five floors of stairs are able to undergo even a pneumonectomy safely.


Predicted Postoperative Values


After assessment of PFTs and exercise capacity, the final step is the calculation of the predicted postoperative values of FEV1 and DL CO . The formula used incorporates the number of bronchopulmonary segments removed at the time of resection. The number of bronchopulmonary segments per lobe:




  • Right lung: upper lobe (3), middle lobe (2), lower lobe (5)



  • Left lung: upper lobe (5–3 apical + 2 lingula), lower lobe (4)



Formula:


<SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='Predicted postoperativePPOvalue=Preoperative value×19-excised number of segments19′>Predicted postoperative(PPO)value=Preoperative value×(19excised number of segments)19Predicted postoperativePPOvalue=Preoperative value×19-excised number of segments19
Predicted postoperativePPOvalue=Preoperative value×19-excised number of segments19


Historically, PPO values greater than 50% were ideal. With improvement in surgical and critical care practices, PPO values of 40% are acceptable and can be considered even as low as 30% if the care is at centers of excellence who have robust experience taking care of high-risk patients.


Special Considerations


For patients with marginal pulmonary reserve needing a pneumonectomy for eradication of disease, additional assessment with ventilation–perfusion (VQ) scans can help determine regional function. VQ scans are also helpful for those patients with heterogenous distribution of lung disease (e.g., upper lobe predominant emphysema; area-specific bronchiectasis).


Prevention of Postoperative Pulmonary Complications


Once a decision is made to go forward with surgical intervention, the focus shifts toward optimization of patient health before surgical intervention, safe and efficient conduct of the operation, and prevention of postoperative complications. Although all three are components of enhanced recovery protocols, we will now discuss steps toward prevention of postoperative pulmonary complications (PPCs). These steps include:




  • Stop smoking, 6 to 8 weeks before elective surgery, but can be safely done if quit date at least 3 weeks before surgical date.



  • Undergo a preoperative exercise regimen, including deep breathing and strong cough practice.



  • Optimize medications for chronic obstructive pulmonary disease (COPD) and other lung diseases. This may include use of bronchodilators, inhaled or oral steroids, and antibiotics to treat bacterial infections of the lungs.



  • Delay surgery and treat pneumonia with culture-specific antibiotics, as well as effective use of chest physical therapy.



  • Maximize nutrition before elective surgery.



Optimal Timing of Smoking Cessation


Across the globe, 230 million adults undergo major surgery annually, with cardiorespiratory complications amongst the most devastating complications. Approximately 30% of patients undergoing surgery are smokers at the time of their surgery and it is well known that smoking is associated with an increased risk of postoperative complications, the strongest correlation of which is for respiratory complications.


The optimal duration of smoking cessation prior to surgery has been one of debate. Historically based on two cohort studies from the Mayo Clinic on coronary artery bypass patients, initial recommendations advised a minimum of 8 weeks of smoking cessation prior to surgery. A major textbook of anesthesiology in the 1990s incorrectly extrapolated that smoking cessation less than 8 weeks was associated with increased complications because in the cohort studies there was a nonsignificantly increased rate in that group. Several studies then emerged demonstrating brief preoperative smoking cessation was not associated with increased pulmonary risk.


A systematic review of five perioperative smoking cessation trials demonstrated preoperative smoking cessation reduced a broad composite of postoperative complications. These preoperative smoking cessation programs were positively associated with long-term (12 months) smoking cessation. The trial data did not provide guidance on optimal timing of smoking cessation. The closest guidance of minimal duration of effective smoking cessation prior to surgery comes from a 2011 meta-analysis that concluded the available evidence (an assessment of several studies that admittedly had heterogeneity of the types of surgeries and definition of pulmonary complications) supported smoking cessation at least 3 to 4 weeks prior to surgery. This assessment is supported physiologically by the time it takes for pulmonary benefits of smoking cessation to manifest. However, it should not be forgotten that surgery is a powerful opportunity and motivation for smoking cessation and hence other than the first 48 to 72 hours after smoking cessation where there may be increased bronchorrhea, any amount of time may indeed be a good enough amount of time for smoking cessation prior to surgical intervention.


Use of Incentive Spirometer


PPCs are mostly seen in abdominal, cardiac, and thoracic surgery, and can lead to high rates of morbidity, mortality, increased hospital costs, and prolonged hospital stay. PPCs encompass atelectasis, pneumonia, tracheobronchitis, bronchospasm, exacerbation of COPD, acute respiratory failure, and prolonged mechanical ventilation (longer than 48 hours).


When assessing PPCs, the major contributory factors include shallow breathing and monotonous tidal volumes in the postoperative period. Anesthesia, opioids, and splinting from postoperative pain contribute to this ventilation pattern.


As a result, physical therapy techniques of lung reexpansion have been recommended as strategies to prevent and to treat PPCs, as well as to recover ventilatory function in the postoperative period. Techniques such as deep inspiration, incentive spirometry (IS) and positive airway pressure exercises stimulate the generation of a large and sustained increase in the transpulmonary pressure, with consequent expansion of collapsed alveolar units in order to prevent and/or to treat PPCs.


In the 1960s, intermittent positive-pressure breathing (IPPB) was commonly used to prevent postoperative pulmonary complications. However, further scrutiny determined that there was no evidence of benefit to advocate for its widespread use. Amidst this controversy emerged the incentive spirometer introduced by Bartlett et al. Based on the concept that yawning might generate pulmonary benefits for postoperative patients, they designed a device for patients to emulate a yawning-like sustained maximal inspiration in order to prevent atelectasis.


Several systematic reviews and meta-analyses have been conducted on the use of IS in the perioperative period and the results are mixed. Thomas and McIntosh assessed the efficacy of IS, IPPB, and deep-breathing exercises in the prevention of PPCs in patients undergoing major abdominal surgery. The authors concluded that IS and deep-breathing exercises appear to be more effective than no therapy to prevent PPCs, but there was no evidence to determine which was better. Overend et al. conducted a systematic review on the use of IS for preventing PPCs and found that in 35 of 46 studies they could not accept the conclusions because of flaws in methodology. Of the remaining 11 studies, only one demonstrated any positive effect and in that study, IS, IPPB, and deep breathing were equally effective compared with no treatment. In the systematic review by Carvalho et al. the authors were by and large underwhelmed by the results of IS. Analyzing only studies that evaluated the effect of IS in patients undergoing abdominal surgery, there was no significant difference when compared with other interventions. The results in cardiac surgery were similarly lacking.


Additional Cochrane reviews for coronary artery bypass grafting and upper abdominal surgery did not demonstrate any significant evidence for the use of IS. Agostini and Singh conducted a systematic review of IS after thoracic surgery, where they concluded that the physiologic evidence does support IS use after major thoracic surgery. A novel program that had IS as a component (the I COUGH program ) demonstrated reduction in postoperative pneumonia and unplanned intubations. Individual component contribution was not measured because the intervention occurred as a bundle (IS, coughing, deep breathing, oral care [brushing teeth and mouthwash twice a day], getting out of bed three times daily, and head of bed elevation).


Prevention of Arrhythmia


Atrial fibrillation (AF) has been reported to occur in 12%– 44% of patients after pulmonary and esophageal surgery. Risk factors for postoperative include male sex, increasing age, magnitude of lung resection, magnitude of esophagus resection, history of congestive heart failure, underlying lung disease, preoperative episodes of AF, length of procedure, and procedures associated with postoperative pericardial inflammation as a result of dissection around the atria. In terms of types of surgery, those operations with the highest rates of postoperative AF are pneumonectomies, extrapleural pneumonectomies, and adult lung transplants.


The onset of AF most commonly occurs on postoperative days 2 and 3. The risk of postoperative AF subsequently decreases over the course of a month until it reaches preoperative risk of AF.


Recently the Society of Thoracic Surgeons compiled evidence-based practice guidelines on the prophylaxis and management of AF associated with general thoracic surgery. This was a synthesis of the available clinical trials, cohort studies, and case reports, stratified by categories of recommendation based on the evidence. The recommendations spanned the categories of prevention of postoperative AF, treatment of postoperative AF, and use of anticoagulation therapy. Guideline recommendations included the following:


Preventing Postoperative Atrial Fibrillation





  • Patients taking beta blockers preoperatively should continue to take them without missing doses in the postoperative period (dose adjustment may be needed if epidural is used).



  • Dilitiazem prophylaxis is reasonable in most patients undergoing major pulmonary resection who are not taking beta blockers preoperatively.



  • Magnesium supplementation is reasonable to augment the prophylactic effects of other medications.



  • Amiodarone prophylaxis can be used, but strict dosing protocols are needed. Amiodarone should not be used after pneumonectomy.



  • Use of postoperative beta blockers can be considered in select cases to treat AF, but use is more limited because of side effects.



  • Flecainide and Digoxin should not be used for prophylaxis.



Treatment of Postoperative Atrial Fibrillation





  • Hemodynamically unstable AF should be electrically cardioverted.



  • Hemodynamically stable and symptomatic AF should be chemically cardioverted, with electrical cardioversion if chemical cardioversion fails.



  • Hemodynamically stable and asymptomatic or acceptable symptomatic AF should receive a trial of rate control lasting 24 hours before cardioversion (chemical then electrical).



  • Hemodynamically stable, continuous or recurrent, paroxysmal postoperative AF after adequate levels of chemical cardioversion agent may be considered for an attempt at electrical cardioversion.



Choice of Agent for Treatment


Rate Control





  • For rate control, a selective β1-blocking agent is the initial drug of choice in the absence of moderate to severe COPD.



  • If moderate to severe COPD or bronchospasm is present, dilitiazem is the drug of choice.



Rhythm Control





  • For chemical cardioversion in the setting of continuous or recurrent paroxysmal postoperative AF, the recommendation is for intravenous (IV) followed by oral (PO) administration of amiodarone.



  • For mechanically ventilated patients, preexisting lung disease, or after pneumonectomy, avoid the use of amiodarone.



  • Once initiated and successful, antiarrhythmic therapy should be continued for a minimum of 1 week up to a maximum of 6 weeks. (Most current protocols advocate a 1-month duration of therapy.)



Use of Anticoagulation Therapy





  • Anticoagulation is recommended in those patients with postoperative AF and two or more risk factors for stroke (age greater than 75 years, impaired left ventricular function, hypertension, prior stroke, or prior transient ischemic attack), and who have postoperative AF that lasts more than 48 hours.



  • For those with fewer than two risk factors for stroke and AF that persists or recurs for more than 48 hours, 325 mg of aspirin should be used.



  • Anticoagulation therapy once initiated should be continued for 4 weeks after return of sinus rhythm.



Enhanced Recovery After Thoracic Surgery


Enhanced recovery after surgery (ERAS) addresses the entire patient journey from referral to discharge. The principle of ERAS is that individual components may have a limited effect on outcome in isolation, but they act synergistically when applied in combination to reduce surgical stress and hasten recovery. The elements of ERAS have been known for decades. For thoracic surgery, in addition to the traditional components of ERAS, the most relevant modifiable risk factors are the management of chest tubes, pain control, and social support plans. A recent systematic review and meta-analysis demonstrated that ERAS pathways in lung cancer surgery are associated with reduced complications, shorter length of stay, and cost savings.


The 2019 guidelines for enhanced recovery after lung surgery compiled evidence-based recommendations of the ERAS society and ESTS. Specific details about ERAS protocols pertinent to successful perioperative outcomes in thoracic surgery are as follows:




  • Preoperative counselling helps to set expectations about surgical and anesthetic procedures, which in itself may help to increase patient understanding, diminish fear, fatigue and pain, and thus enhance early discharge.



  • Nutritional components of ERAS include preoperative fluid and carbohydrate loading (up to 3 hours before surgery), and early postoperative restarting of oral diet and oral nutritional supplements (ONS). Malnutrition is an important modifiable risk factor for adverse outcomes after major surgery. Because the vast majority of pulmonary rehabilitation programs for patients with significant COPD emphasize nutritional supplementation, ONS is recommended and improves patient quality of life and muscle function. Additionally, cancer patients should be screened for malnutrition with appropriate interventions initiated once it is identified in the preoperative setting.



  • Alcohol is associated with perioperative morbidity and mortality and should be avoided for at least 4 weeks before surgery in patients who abuse alcohol.



  • Anemia should be identified and corrected for iron deficiency and any underlying disorder before surgery. Where possible, blood transfusion or erythropoiesis-stimulating agents should not be used to correct preoperative anemia.



  • Although recent systematic reviews and meta-analyses have determined that rehabilitation is beneficial, the wide heterogeneity of studies (duration, intensity, structure, patient selection) precludes the ability to determine the protocol for maximal benefit.



  • Early ERAS protocols recommended epidural analgesia as an essential part of the bundle for pain management. With recognition of increased adverse events such as hypotension, urinary retention, and muscular weakness associated with epidurals, alternative agents have emerged as agents of choice. Paravertebral blocks provide somatic and sympathetic blockade of nerves that lie in the paravertebral space. Recent randomized studies suggest that paravertebral blocks are more effective at reducing respiratory complications compared with thoracic epidurals and after the first few hours provide equivalent analgesia.



  • During the postoperative phase, a multimodal analgesic regimen should be used with the aim of minimizing the use of opioids. Acetaminophen in combination with nonsteroidal inflammatory drugs is more effective than either drug alone.



  • In lung resection surgery, patients are prone to develop interstitial and alveolar edema with fluid administration. Preexisting lung disease, prior chemoradiation, one-lung ventilation, direct lung manipulation at the time of surgery, and ischemia–reperfusion injury can all increase the risk of lung injury. As a result, volume restriction of IV fluids is advocated, with a goal of perioperative fluid balance of less than 1500 mL (20 mL/kg/24 hours). In the postoperative period, attention is kept on fluid balance and PO intake should be resumed as soon as it is clinically safe to do so.



  • Early mobilization is a core component of ERAS in the postoperative period.




References

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Jun 9, 2021 | Posted by in ANESTHESIA | Comments Off on General Thoracic Surgery
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