Cardiac Risk Stratification

This is by far the most important aspect of preoperative assessment. Any patient with a score >2 should be referred to cardiology for additional testing. The Revised Cardiac Risk Index is shown in Table 16.1.

The Thoracic Revised Cardiac Risk Index has four components, each of which is weighted. Patients with a score ≥2 should be referred to a cardiologist for risk stratification and additional testing if needed [Reference Salati and Brunelli1].

Assessment of Lung Resectability

The initial step in assessing lung resectability is a cardiopulmonary examination using the Thoracic Revised Cardiac Risk Index. Once cleared from a cardiac standpoint, the patient’s pulmonary function must be examined to generate predictive postoperative values (ppoFEV₁ and ppoDLCO), calculated based on the maximum proposed number of segments removed:

Reductions in ppoFEV₁ and ppoDLCO are both associated with an increased risk of postoperative pulmonary complications (PPCs), including increased 30-day readmission, prolonged length of stay, and decreased overall survival. According to the American College of Chest Physicians (ACCP), patients with ppoFEV₁ and ppoDLCO >60% are considered low risk for PPCs and do not require additional cardiopulmonary testing. Those with ppoFEV₁ or ppoDLCO <60% and >30% are recommended to undergo informal evaluation of their cardiopulmonary reserve. This could include the stair climbing test, shuttle walk test, 6-minute walk test, or exercise oxygen desaturation test. Conversely, those with a high risk cardiac evaluation, poor results on informal exercise testing, or a ppoFEV₁ or ppoDLCO <30% are recommended to undergo formal laboratory exercise testing or cardiopulmonary exercise testing. Those with low VO₂ max <10 mL/(kg min) or <35% predicted are considered to be at high risk. These patients should be counseled on sublobar resections, less invasive surgical options, nonoperative treatments, and palliative care. A flowchart summarizing the recommendations of the American College of Chest Physicians (ACCP) for preoperative evaluation is shown in Figure 16.1.

Figure 16.1 The American College of Chest Physicians (ACCP) algorithm for cardiopulmonary preoperative assessment of patients requiring lung resection. According to the ACCP, low risk indicates a mortality rate below 1%. In patients deemed moderate risk, morbidity and mortalityrates vary, based on pulmonary function, exercise tolerance, and the extent of resection. High-risk patients may have perioperative mortality rates in excess of 10%. CPET, cardiopulmonary exercise test; DLCO, diffusing capacity of the lungs for carbon monoxide; FEV₁, forced expiratory volume in first second; ppo, predicted postoperative; SCT, stair climbing test; SWT, shuttle walk test; VO₂ max, maximal oxygen consumption. Source: Reprinted with permission from Brunelli A, Kim A, Burger KI, Addrizzo-Harris, DJ. Physiologic evaluation of the patient with lung cancer being considered for resectional surgery: diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2013;143(5 Suppl):e166S–90S.

Remember, these equations and procedures reflect the typical relationship between the extent of resection and postoperative complications. Values such as ppoDLCO decrease as more functional lung tissue is removed; thus, there is an increase in morbidity and mortality. Notable exceptions include disease processes that reduce lung compliance and/or functional capacity. For example, in patients with chronic obstructive pulmonary disease (COPD), the removal of emphysematous lung may actually improve the degree of ventilation/perfusion mismatch postoperatively. Therefore, in these patients, regional lung studies may provide a more accurate prediction of postoperative pulmonary function.

Finally, many thoracic procedures are related to previous cancer diagnosis. Therefore, it is important for anesthesiologists to understand the anesthetic implications of various malignancies. Broadly, nonsmall-cell cancers have better outcomes with surgical treatment than small-cell cancers. However, metabolic activity, size, and location can play a large role in airway and intraoperative management. Therefore, it is critical to perform a focused evaluation on the “4 Ms” in all patients with pulmonary masses:

• 
  

  Mass effects – obstructive pneumonia, lung abscess, superior vena cava syndrome, tracheobronchial distortion, Pancoast syndrome, nerve palsy, chest wall or mediastinal extension

  
  
• 
  

  Metabolic – Lambert–Eaton syndrome, hypercalcemia, hyponatremia, Cushing’s syndrome

  
  
• 
  

  Metastases – particularly to the brain, bone, liver, and adrenals

  
  
• 
  

  Medications – chemotherapy agents: pulmonary, cardiac, and renal toxicity.

Preoperative Optimization

Smoking cessation, in particular, is important for thoracic surgeries. Smoking is the most common cause of lung disease and is associated with an increased postoperative 30-day mortality rate, as well as an increased risk of postoperative pulmonary complications. Furthermore, these outcomes are directly correlated with the number of pack-years smoked. While the required duration of smoking cessation preoperatively to mitigate these risks is unknown, recent studies have suggested that smoking cessation of <8 weeks is still beneficial.

Lung Isolation Techniques

Lung isolation, or one-lung ventilation (OLV), is desired in surgery to optimize surgical access and exposure and prevent puncturing of the lung, and can prevent contamination of healthy lung tissue by a diseased lung in cases of severe infection or bleeding [Reference Mehrotra and Jain2]. Tables 16.2 and 16.3 show indications for OLV, two methods of OLV, and relevant information.

Double-lumen tubes (DLTs) are the main method of anatomic and physiologic isolation in most thoracic surgery cases. Selective ventilation of an individual lung can also be achieved using a bronchial blocker, with an open-tipped model applying continuous positive pressure and suction in the airway therefore being a more useful choice to use, rather than a closed-tip. Single-lumen endotracheal tubes are preferred for patients younger than 6 months [Reference Mehrotra and Jain2].

Physiology of One-Lung Ventilation

In order to improve gas exchange and ventilation efficiency during OLV, recruitment maneuvers should be employed. Peak airway pressure for recruitment in healthy lung should remain <40 cmH₂O, with a PEEP slowly increasing up to 20 cmH₂O, and lower in a diseased lung [Reference Blank, Colquhoun and Durieux3, Reference Colquhoun, Naik and Durieux4]. Final recruitment maneuvers with two-lung ventilation should be performed at lower pressure levels to prevent disrupting surgical staples. The end result of these techniques improves oxygenation, increases compliance, and decreases dead space, while also potentially reducing inflammatory cytokine release [Reference Karzai and Schwarzkopf5]. Thoracic surgical procedures should use all of the American Society of Anesthesiologists standard basic anesthetic monitoring. Summarized below are the most important vitals to monitor during OLV:

• 
  

  FiO₂: lowest to maintain SpO₂ >90%

  
  
• 
  

  TV: 4–6 mL kg⁻¹ based on ideal body weight

  
  
• 
  

  PEEP: 5–10 cmH₂O to dependent lung

  
  
• 
  

  CPAP: 2–5 cmH₂O (disrupt when visibility impaired) to nondependent lung

  
  
• 
  

  PaCO₂: <60–70 mmHg.

Addressing Hypoxemia

Hypoxemia is defined as an oxygen saturation below 85–90% PaO₂ while inspired FiO₂ is 1.0 [Reference Inoue, Nishimine, Kitaguchi, Furuya and Taniguchi6]. This occurs in approximately 5–10% of patients. In this scenario, nonurgent procedures should be stopped, and dual-lung ventilation should be restored until oxygenation improves. If hypoxia persists or recurs, check placement of the DLT or bronchial blocker, as they are the most common cause. Table 16.4 summarizes the management of hypoxemia during OLV [Reference Karzai and Schwarzkopf5].

Goal-Directed Fluid Management

Hypovolemia results in insufficient oxygen delivery and flow-dependent organ dysfunction, as opposed to hypervolemia, which leads to pulmonary interstitial edema with impaired oxygen diffusion and poor collagen regeneration. Table 16.5 shows the parameters that need to be monitored to maximize cardiac output and oxygen delivery while minimizing perioperative complications [Reference Licker, Triponez, Ellenberger and Karenovics8–10].

Nonintubating Technique for Thoracic Surgical Procedures

Although the mainstay of all thoracic surgery patients has been intubation with endotracheal tube/DLT after induction of general anesthesia, nonintubating techniques have been gaining popularity over recent years.

Benefits include reduced postoperative morbidity, faster discharge, decreased hospital costs, and a globally reduced perturbation of the patient’s well-being. Important results from a meta-analysis suggests that nonintubating general anesthesia for thoracic procedures can reduce operative morbidity and hospital stay when compared to equipollent procedures performed under general anesthesia [Reference Tacconi and Pompeo11]. See Table 16.6 for indications of sedation for thoracic procedures [Reference Kiss and Castillo12].

Regional Techniques

The types of blocks used in thoracic techniques can be complicated. Table 16.7 summarizes the different types of anesthetic blocks, and their complications are described in Table 16.8.

Table 16.7 Sedation indications and techniques for thoracic procedures

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