Lung Resections for Cancer and Benign Chest Tumors

Mark Stafford-Smith

Clinical Vignette

In the past two decades, significant research and innovation has improved both therapy and prognosis for lung cancers and benign tumors. Medical gains in imaging, better timing, prescription, and selectivity of radiation and chemotherapy have complemented surgical advances, including routine tumor staging, port access video-assistance, titanium staplers with scalpel blades, and more targeted operations designed to preserve unaffected lung tissue. Anesthesia advances have kept pace, with better lung isolation methods and a broadened pharmacologic armamentarium providing an enhanced flexibility that combines safe surgery with multiple options for postoperative analgesia and prompt wake-up and extubation, even for patients with limited respiratory reserve or when a procedure is terminated prematurely. Notably, many of these improvements have expanded the candidate pool for lung resection to include patients who would previously have been ineligible due to their marginal lung function.

Despite advances, perioperative morbidity and mortality rates for lung resection still exceed those for many major procedures (eg, aortocoronary bypass surgery), and few dispute the important role of the anesthesiologist’s actions in influencing patient outcome.^1–3 The aim of this chapter is to address and integrate numerous elements of thoracic anesthesia, some outlined in more detail in other chapters, which combine to optimize anesthesia provision for lung resection surgery for cancer and benign chest tumors.

TYPES OF LUNG TUMORS

Over 170,000 primary lung tumors are diagnosed each year in the United States, with the majority being malignant (>95%). Malignant lung tumors are the largest source of cancer-related deaths in the United States. Cigarettes increase lung cancer risk for the average smoker by approximately tenfold, twentyfold for heavy smokers. Other inhalation exposures act alone or can compound smoking risk, including radiation (eg, radon, uranium), asbestos, nickel, chromate, mustard gas, arsenic, beryllium, iron, and vinyl chloride. Lung cancer is about twice as common in men as women (74 vs 31 per 100,000 per year), presenting most often during the sixth and seventh decades of life. While inhalation exposures are the major risk for lung cancer occurrence, in victims less than 40 years old (<2% patients) genetic vulnerability is also likely important.⁴

First symptoms of a primary lung cancer may include productive cough, hemoptysis, weight loss, pain or dyspnea, and less commonly clubbing, superior vena cava syndrome, Horner syndrome, muscle weakness, peripheral neuropathy, or ataxia. The most common tumors related to smoking are squamous and small cell and less frequently adenocarcinoma (Table 13–1). At diagnosis, over 80% of small cell tumors are metastatic, whereas less than half of squamous and adenocarcinomas have spread. While most benign tumors are resectable, only 30% of malignant primary tumors are still sufficiently localized to potentially benefit from surgery.

Table 13–1. Classification of Lung Tumors Commonly Presenting for Lung Resection

Surgical resection of lung metastases improves survival in some situations. In the absence of other spread, one or several lung metastases can be removed on one or repeated occasions, often involving a simple wedge resection achieved using VATS surgery. Disease states include melanoma, soft tissue and osteo-sarcomas, germ cell tumors, colorectal, renal cell, uterine and breast cancer, and squamous cell cancers of the head and neck.⁵

LUNG RESECTION—PROCEDURE PLANNING

Minimizing loss of healthy tissue is a logical part of surgical planning for any lung resection. Limited procedures such as localized wedge or segmental lung resection are often all that is necessary for benign tumors. For cancerous lesions, evidence of tumor spread from noninvasive (eg, chest x-ray, CT, and PET scan) or invasive procedures such as bronchoscopy and mediastinoscopy provides the most important guide in avoiding unhelpful lung resection surgery. When mediastinoscopy reveals ipsilateral mediastinal lymph-node spread, subsequent response to induction chemotherapy (eg, cis-platinum, paclitaxel), evidenced by a negative re-mediastinoscopy, still indicates eligibility for curative surgery, and long-term outcomes are improved.⁶

When tumor spread is unlikely, bronchoscopy and mediastinoscopy may be scheduled at the same time as lung resection, but the anesthetic plan must always be able to adapt to early termination if staging samples return positive for cancer. Of practical clinical significance with early termination is not to have used agents with prolonged effects that delay wakeup (eg, muscle relaxants) or require prolonged observation (eg, neuraxial opioids). Delayed discharge home is particularly distressing for the patient coping with the news of their cancer spread.

Early stage cancerous tumors are treated by complete resection of the involved lung lobe. However, some early stage tumors, by reason of more extensive local spread or their relationship to major airways, are ineligible for lobectomy and have traditionally been candidates for pneumonectomy. Examples of lung-sparing alternatives to pneumonectomy for selected individuals include bi-lobectomy and upper lobe/sleeve bronchus resection with reattachment of the lower lung lobes. In high-risk patients with limited pulmonary reserve, localized wedge or segmental lung resection may be all that is possible even for malignant disease.

Video-assisted thoracic surgery (VATS) is taking an ever expanding role in the approach to lung tumor surgery. The introduction of VATS surgery for lung resection has been associated with good results and a reduction in complication rates (Table 13–2),^7,8 although some institutions have not seen improvements in outcome.⁹ VATS procedures are particularly reliant on perfect lung isolation and place added responsibility on the anesthesiologist in this regard. Lung resection more extensive than lobectomy is generally not eligible for VATS, in part due to the disproportionately small size of the port incision relative to the resected tissue that must be extracted through it. However, even small tumors are sometimes so placed as to be ineligible for resection by a VATS approach (eg, hilar). Studies indicate that appropriate use of VATS procedures capably achieve surgical goals with lower dehiscence, bleeding and infection rates, reduced pain, and faster recovery. Compared to open thoracotomy, VATS also often reduces the need for rib spreading and the possibility of rib fractures. Other differences between VATS and open thoracotomy for equivalent procedures is the tendency for less pain and blood loss and quicker recovery from VATS surgery. Sources of morbidity and mortality following lung resection surgery vary by procedure and surgical approach, increasing with more extensive lung resection and open (vs VATS) surgical approaches (see Table 13–2).

Table 13–2. Complication Rates (%) in a Population of 1079 Patients Undergoing Lobectomy Lung Resection by Conventional Thoracotomy (n = 382) and video-assisted thoracoscopic surgery (VATS), n = 697 Approaches

PREOPERATIVE ASSESSMENT (SEE ALSO CHAPTER 9)

Beyond standard preoperative assessment, patients scheduled for lung tumor procedures commonly have considerations specific to their presenting condition and planned surgery. Perioperative risk may be increased by issues related to the origin of their cancer (eg, smoking), but tumor-derived concerns can also contribute to risk (eg, paraneoplastic syndromes). For lung tumor surgeries, a detailed assessment of airway, bleeding risk, and eligibility for neuraxial procedures is particularly relevant.

Smoking increases the risk of lung cancer, and also chronic bronchitis, reactive airway disease, and obstructive lung disease. Some patients present for surgery so affected by these accompanying conditions as to require supplemental home oxygen therapy. For these patients, preparation should include pulmonary function data to quantify their respiratory impairment and a plan for preoperative optimization. In patients with poor respiratory function, preoperative arterial blood gas assessment can also inform postoperative management (Figure 13–1). Risk for atherosclerotic heart and vascular disease is also increased in smokers, as is cor pulmonale, supraventricular tachyarrhythmias, and atrial fibrillation. Assessment of cardiac risk follows standardized protocols as for any nonscardiac surgery patient.¹⁰

Figure 13–1. Evidence of an elevated arterial partial pressure of carbon dioxide (PaCO₂) while breathing spontaneously is strongly suggestive that a patient has very impaired pulmonary function, as represented in this data by severely impaired forced expiratory volume in 1 second with maximal effort (FEV₁). The shaded area represents normal PCO₂ values.

Paraneoplastic syndromes sometimes are a presenting symptom of lung cancer. Tumor-mediated autoantibodies to calcium channels and Purkinje cells can cause Lambert-Eaton myesthenic syndrome and subacute cerebellar degeneration, respectively.¹¹ The former involves muscle weakness that may be symptomatic, but whose diagnosis is sometimes missed until an exaggerated muscle relaxant response requires postoperative ventilator management; the latter is a degenerative neurologic disorder characterized by broad ataxic gait and nystagmus without other gross neurologic deficits. Lambert-Eaton syndrome contrasts with myesthenia gravis by its involvement of proximal more than distal limb muscles and improved strength with repetitive movements but not in response to acetylcholinesterase inhibitor therapy (eg, neostigmine). Other lung tumor-related hormone effects include hyponatremia due to inappropriate anti-diuretic hormone secretion, Cushing syndrome from excess adrenocorticotrophic hormone, and hypercalcemia from parathyroid hormone release. Among patients with benign lesions, those with neurofibromatosis-1 are notable for the frequent coexistence of neuroendocrine tumors including pheochromocytoma (up to 6% patients, and 20%-50% of those with associated hypertension) and carcinoids (up to 10% patients).^12–14 Although neurofibromatosis-1 is associated with an increased lung cancer risk, VATS in these patients is usually performed for neurofibroma resection with the offending tumor most often protruding from an intervertebral foramen. Presumably due to tumor friability and location, epidural hematoma with paraplegia can complicate neurofibroma resection and must be considered in the risk/benefit analysis for neuraxial analgesia.

Identification of patients with increased bleeding risk and those who may be ineligible for spinal/epidural analgesia (see Chapters 6, 9, 24) requires careful assessment of bleeding history (eg, with tooth extraction), chronic drug therapies (eg, clopidogrel), and review of coagulation tests. Neuraxial procedure guidelines are available regarding acceptable coagulation parameters and timing of anticoagulation cessation.¹⁵ The plan for coordinated epidural catheter removal and postoperative thromboprophylaxis must also be formulated preoperatively to minimize spinal hematoma risk. In some patients presenting with conditions requiring chronic warfarin anticoagulation (eg, atrial fibrillation), heparin “bridging” therapy may be required until just prior to surgery. Concurrent infection and anatomic spinal abnormalities are also factors in determining suitability for spinal/epidural procedures.

Management of chronic drug therapies must involve attention to respiratory depressant effects, particularly in patients with marginal pulmonary reserve. Delayed tracheal extubation is a strong predictor of poor outcome, and agents such as extended release opioids can sometimes take partial blame for this complication after lung resection. Even depressant effects from well-intentioned but ill-considered “modest” preanesthetic intravenous sedative (eg, midazolam for anxiety) can complicate lung resection in high-risk patients; by compounding the respiratory depression due to agents that are arguably of more importance at the end of surgery, such as opioids for analgesia. In these circumstances, patient reassurance for anxiolysis, including an explanation of the need to limit preoperative sedation, is often sufficient, but if pharmacologic intervention is deemed essential (eg, during complicated epidural placement), then in the author’s experience, for an average-sized adult, small doses of a short acting intravenous sedative (eg,10-20 mg propofol) alone or potentiated by a very small dose of longer acting agent (eg, 0.25-0.5 mg midazolam) are generally very effective.

ANESTHETIC PLAN

Preinduction

Preparation for even the most “straightforward” lung surgery demands sufficient monitoring and vascular access to appropriately respond to complications that can occur, most notably including significant hemorrhage, an uncommon but ever-present risk for any intrathoracic procedure. Beyond standard monitoring requirements and two large bore peripheral intravenous catheters, invasive lines generally include a peripheral intra-arterial catheter for continuous blood pressure recording and repeated blood gas assessment. A right-sided radial arterial line is convenient if staging procedures are also planned since this location also facilitates recognition of innominate artery compression during mediastinoscopy (see Chapter 10).

Neuraxial injection or catheter placement prior to anesthesia induction (eg, epidural catheter insertion) most conveniently occurs following placement of peripheral intravenous and intra-arterial catheters but prior to central venous access. Such a sequence provides intra-arterial monitoring for recognition of intravascular or intrathecal injection of an epidural catheter test-dose and avoids the cumbersome movement required to have a patient transfer into the sitting or lateral position with a central venous line in situ.

While central venous access is not essential for lung resection surgery, patient and procedural factors such as comorbidities (eg, cardiac history), bleeding risk (eg, redo thoracotomy), and the likelihood of postoperative pulmonary edema (eg, pneumonectomy) may warrant such monitoring. If placement of a central venous catheter is deemed necessary, selection of the side ipsilateral to the operative lung is highly preferable for subclavian or internal jugular central venous puncture, due to possibilites such as unrecognized bullous lung disease and the potential for tension pneumothorax in the nonoperative lung. “Down-side” tension pneumothorax can be lethal when it manifests intraoperatively and is difficult to detect. One way is to attach a stethoscope earpiece to a suitable esophageal temperature probe and use it as an esophageal stethoscope. In the case of a “down-side” tension pneumothorax, the chest is completely silent on manual inflation of the reservoir bag.

Bladder catheter placement is not essential for all lung resection procedures and can occur after anesthesia induction. Urinary output monitoring provides some information regarding intravascular volume status in the absence of central venous pressure data and should always be used to avoid the possibility of urinary retention in patients with postoperative epidural analgesia.

Standard preinduction considerations include administration of intravenous antibiotic prophylaxis within 1 hour prior to surgical incision and planning for postoperative disposition (PACU vs stepdown vs ICU observation). Postoperative analgesia strategy often influences disposition when continuous epidural infusions are used, since the care team must be equipped and trained to recognize and treat potentially serious complications associated with their use such as hypotension from local anesthetic-mediated reductions in sympathetic tone and delayed respiratory depression due to cephalad spread of neuraxial opioids (see Chapter 6).

The potential for major hemorrhage with lung surgery is partially explained by the thin walled and high flow characteristics of the pulmonary arterial tree, making these vessels both vulnerable to injury and difficult to repair, with the same capacity for rapid blood loss as major systemic arteries. The uncommon but serious bleeding complication with lung resection mandates preparatory steps in addition to good intravenous access and monitoring. Confirmation that blood products are available and/or in the operating room is essential immediately prior to surgery. Routine availability of colloid volume expanders, use of fluid and patient warming technology, and a rapid transfusion device immediately available or nearby should also be considered.

Nonetheless, the liberal availability of blood products required in preparation for lung resection surgery must be accompanied by thoughtful application of transfusion “triggers” and strict avoidance of unjustifiable blood product administration. Poorer outcomes with “unnecessary” transfusion including pulmonary complications are particularly relevant to lung surgery. Also, a note of caution is warranted regarding the potential for resuscitation “overshoot” that can occur in any response to acute hemorrhage. An effort to keep scale in the resuscitation of hemorrhage, assisted by good communication with the surgeon, will help avoid the lung edema that can occur from fluid overload.

Intraoperative Management

Related posts:

Practice Improvement and Patient Safety in Thoracic Anesthesia: A Human Factors Perspective Lung Separation Techniques Bronchopleural Fistula: Anesthetic Management Thoracic Trauma Management Pericardial Window Procedures Therapeutic Bronchoscopy, Airway Stents, and Other Closed Thorax Procedures

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