Updates to Thoracic Procedures: Perioperative Care and Anesthetic Considerations

Abstract

Thoracic surgery is a rapidly evolving field, as is the perioperative and anesthetic care of patients undergoing major thoracic surgery. As surgical techniques continue to evolve, new guidelines are needed to help standardize patient care. To this end, Enhanced Recovery After Surgery (ERAS) protocols were created and have seen increasingly widespread adoption within the field of thoracic surgery. Despite their name, the scope of these protocols includes not only the postoperative period, but also helps guide care in the preoperative and intraoperative periods. Thus, ERAS pathways are relevant to both thoracic surgeons and anesthesiologists. This chapter aims to summarize current guidelines for managing patients undergoing thoracic surgery (from the preoperative period all the way through to postoperative care) by discussing recent updates within the field as well as some more well established tenets that remain relevant to the topic.

1. Introduction

Within the field of thoracic surgery, recent emphasis has been placed on the creation of standardized enhanced recovery after surgery (ERAS) pathways for patients undergoing intrathoracic procedures. These multidisciplinary pathways are designed to span all temporal aspects of perioperative care — preoperative, intraoperative, and postoperative [1]. Through standardization, such protocols aim to improve provider efficiency, increase patient throughput, and, ultimately, to diminish patient morbidity and mortality after surgery. Although this chapter will address each of these phases, particular attention will be paid to intraoperative ventilatory management and perioperative pain control given their importance within thoracic-specific ERAS protocols.

2. Methods

Literature review was performed using Google Scholar and PubMed databases. Search topics included “thoracic anesthesia”, “enhanced recovery after thoracic surgery”, “one-lung ventilation”, and “thoracic regional anesthesia”. Reference lists of eligible articles were crosschecked for other relevant material. Literature from the past five years (2017–2022) was prioritized wherever possible; however, less contemporary sources (1997–2016) were also utilized when more recent data was not available.

3. Enhanced recovery after thoracic surgery

The concept of ERAS protocols was first described with regards to colorectal surgery in 1997 by Kehlet [2], and this protocolized approach was soon adapted to various other surgical specialties, including thoracic surgery [3]. The aim of such protocols is to minimize the stress response to major surgery and thereby expedite postoperative return to homeostasis. enhanced recovery after thoracic surgery (ERATS) protocols, in comparison to other surgical specialties, places a heavier emphasis on the quality rather than the speed of patient recovery [4]. They have been shown to improve patient outcomes after surgery, minimize fluid overload, and reduce the rates of pulmonary and cardiac complications [5]. They have the additional benefit of minimizing not only individual practitioner variability, but also analgesic practices associated with greater negative side effect profiles such as schedule II opioids [6, 7]. Furthermore, with regards to operative strategy (i.e., video-assisted thoracoscopic surgery [VATS] versus thoracotomy], the implementation of ERATS protocols may help minimize the differences in outcome conferred by surgical incision [8].

And while improving the quality of patient recovery remains the focus, the speed and efficiency of postoperative recovery is also improved with ERATS pathways, as demonstrated by a statistically significant decrease in postoperative time to removal of chest drains, time to enteral nutrition, and time to ambulation [9]. The net result of these improvements is a reduction in hospital and ICU length of stay as well as an overall decrease in hospital costs [10, 11]. For patients undergoing pulmonary resections for malignancy, this quicker return to baseline also means a quicker return to intended oncologic treatments, positively affecting the ability of those patients to initiate and complete adjuvant chemotherapy and radiation [4].

In 2018, the ERAS® Society and the European Society of Thoracic Surgeons (ESTS) released recommendations for enhanced recovery after lung surgery [5]. However, ERATS protocols remain largely institution specific in the United States [11].

4. Preoperative phase

4.1 Screening and optimization

The main goals of preoperative care are to identify high-risk patients, address modifiable risk factors, and optimize organ function (Table 1) [1].

Risk Factor	Criteria
Anemia	Hemoglobin <12 g/dL (females) or < 13 g/dL (males)
Dysnatremia	Serum sodium <135 mEq/L or > 145 mEq/L
Malnutrition	10–15% weight loss within 6 months, BMI <18.5 kg/m^2, serum albumin <3.0 g/dL
Hyperglycemia	Elevated HbA1c (for patients with diabetes mellitus)
Renal impairment	High serum creatinine or low GFR
Alcohol dependency	Alcohol use within 4 weeks of surgery (for patients with chronic alcohol abuse)
Active smoking	Ongoing smoking within 4 weeks of surgery
Poor lung function	FEV1 or DLCO <40% of expected
Impaired functional capacity	VO2max < 15 mL/kg/min

Table 1.

Preoperative considerations for patients participating in ERATS.

BMI (body mass index), HbA1c (glycosylated hemoglobin A), GFR (glomerular filtration rate), FEV1 (forced expiratory volume in 1 second), DLCO (diffusing capacity for carbon monoxide), VO2_max (maximal oxygen consumption).

Preoperative care often begins with preoperative counseling. This can take the form of verbalized education, leaflets, and/or multimedia information. Such counseling helps to address patient concerns and set realistic expectations. It has been suggested that psychological counseling may help improve postoperative pain, behavioral recovery, and length of stay after surgery [12].

Routine preoperative lab work should be collected on patients undergoing thoracic surgery. It is important to identify and correct preoperative anemia, as it is associated with increased postoperative morbidity and mortality [13]. Underlying causes should be addressed, and iron therapy should be initiated when appropriate. Correction of even mild anemia (hemoglobin <12 g/dL in females and < 13 g/dL in males) can reduce the need for perioperative blood transfusion [14]. Preoperative blood transfusion should be avoided whenever possible, as perioperative transfusion has been associated with worse outcomes in cancer patients [15]. Dysnatremia (serum sodium <135 mEq/L or > 145 mEq/L) should similarly be identified and correctly, as it has also been shown to be an independent risk factor for perioperative mortality in patients with lung cancer [13].

Nutrition is another preoperative consideration, as malnutrition is an important modifiable risk factor. Up to 28% of patients with operable lung cancer are at severe nutritional risk [14], and routine preoperative nutrition screening can help identify malnourished patients who may be at increased risk for postoperative complications. Patients with weight loss of 10–15% within six months, BMI <18.5 kg/m², and/or serum albumin <3.0 g/dL should receive nutritional support for 10–14 days prior to surgery, and it may be beneficial to delay surgery to allow for this support [1, 14]. Although the traditional methodology has been to keep patient NPO after midnight on the day of surgery, it has been shown that these restrictions are needlessly prohibitive. Instead, it is recommended to allow intake of clear liquids up to two hours prior to surgery and solid foods up to 6 hours prior to surgery for patients without conditions associated with gastric outlet obstruction [5]. Preoperative carbohydrate loading—often in the form of carbohydrate drinks—can decrease postoperative insulin resistance and, although this has not been thoroughly investigated in diabetic patients, is generally believed to be safe in patients with well-controlled diabetes [5]. It may also serve to decrease postoperative nausea and vomiting (PONV).

Glycemic management is an important factor to consider in patients undergoing thoracic surgery. This is true not only of patients with known history of diabetes mellitus, but also those without. A glycosylated hemoglobin A (HbA1c) may be checked preoperatively in order to assess overall glycemic control. A higher HbA1c is associated with high levels of intraoperative insulin resistance, and intraoperative hyperglycemia has been shown to be an independent predictor of postoperative complications and mortality in patients with and without diabetes [16, 17]. Patients with uncontrolled preoperative glucose levels should therefore be referred to either their primary care physician or endocrinologist for optimization prior to surgery.

Alcohol dependency is associated with increased postoperative pulmonary complications (PPCs) and mortality in patients undergoing surgery for lung cancer [5]. The chronic effects of alcohol abuse are known to have deleterious effects on cardiac function as well as coagulation and immune functions, thereby leading to increased morbidity. Patients with alcohol dependency should therefore completely abstain from alcohol intake prior to undergoing thoracic surgery; while this may reduce the incidence of PPCs, it has not been shown to significantly reduce mortality or LOS [5]. It should be noted that this recommendation only applies to patients with alcohol use disorder rather than all patients who consume alcohol.

Smoking cessation should be strongly encouraged in all patients undergoing thoracic surgery. Active smoking is associated with high risk for post-operative complications, and its risks are slowly mitigated by complete preoperative cessation [18]. Not only does it confer an elevated risk of myocardial infarction, cerebrovascular accident, and likelihood of death within 30 days of surgery [1], but patients who smoke are twice as likely to experience PPCs than never smokers or, importantly, those who had quit smoking for at least four weeks [5]. Furthermore, ongoing smoking at the time of surgery is associated with poor postoperative quality of life, increased fatigue, and reduced long-term survival [19]. The deleterious effects of smoking on pulmonary function have been shown to improve within four weeks of cessation, and, when feasible, it may be reasonable to delay surgery for up to four weeks to allow for smoking cessation [20]. Various smoking cessation interventions such as behavioral support, pharmacotherapy, and nicotine replacement may be used, although there is no strong evidence to suggest that these specific methods actively decrease postoperative morbidity [5].

Poor preoperative lung function and physical inactivity are also among the biggest risk factors for poor outcomes after thoracic surgery [1]. The most common preoperative assessments of lung function include exercise testing in conjunction with pulmonary function tests. Thus, preoperative optimization of pulmonary function (“pulmonary prehabilitation”) is another tenet of ERATS protocols. Although there are no current consensus guidelines regarding the exact nature and duration of pulmonary prehabilitation, patients who underwent moderate to high intensity preoperative training programs for a median duration of four weeks with a frequency of five sessions per week were demonstrated to have a significant improvement in lung function [21], as well as improved postoperative outcomes and quality of life [1]. Patients with untreated chronic obstructive pulmonary disease (COPD) are at increased risk for PPCs and therefore stand to benefit significantly from preoperative pulmonary optimization. Such patients should be started on a long-acting bronchodilator to improve respiratory symptoms and pulmonary function; additionally, inhaled corticosteroids may help to improve postoperative outcomes in these patients [14].

4.2 High-risk patients and procedures

It is important to note, however, that ERATS protocols are designed with most, but not all patients in mind. Patient selection and safety are paramount, and protocol should never be allowed to supersede surgical decision making. High-risk surgical candidates should be identified through routine preoperative screening. Risk factors for poor outcomes after thoracic surgery include age, obesity, poor preoperative lung function (forced expiratory volume in 1 second [FEV1] or diffusing capacity for carbon monoxide [DLCO] <40% of expected), impaired functional capacity (maximal oxygen consumption [VO2_max] <15 mL/kg/min), higher ASA physical status, ongoing alcohol abuse, active smoking, insulin-dependent diabetes mellitus, chronic kidney disease, and regular preoperative analgesic use [14]. Providers may wish to exclude such high-risk patients from ERATS pathways. Special consideration should also be given to patients undergoing particularly high-risk procedures (e.g., esophagectomy or pneumonectomy), as there are no current guidelines specific to such procedures [7], although traditional ERATS pathways may still be of benefit [22]. As the adoption of ERATS protocols continues to rise, perhaps high-risk procedure-specific recommendations will be made.

5. Intraoperative phase

5.1 Pulmonary physiology

At the most basic level, the pulmonary system exists to facilitate gas exchange from the environmental air we breathe in to the blood in the circulatory system. Respiratory tract organs include the nose, throat, larynx, trachea, bronchi, and lungs, the right lung having three lobes and the left lung having two lobes. The lobes of the lung are made up of small sacks of air called alveoli, and it is at the surface of these alveoli where oxygen exchange occurs via diffusion from the air into pulmonary arterioles. Clinically this is important because an improperly functioning pulmonary system will manifest as hypoxia in the thoracic patient. Hypoxia can have many different etiologies. Hypoventilation occurs when ventilation of the alveoli is decreased. Ventilation-perfusion (V/Q) mismatch occurs when there is an imbalance between available ventilation and arteriolar perfusion, either related to anatomical regions of the lung or various disease states. Right-to-left shunting occurs when deoxygenated blood from the right side of the heart is allowed to bypass the lungs and instead move to the left side of the heart, either anatomical or physiological, and results in a pathological alternate pathway of circulation. Diffusion limitation occurs when oxygen cannot efficiently move from alveoli to pulmonary arterioles, usually related to chronic disease states [23].

Understanding these basic principles is important in understanding the pathophysiologic mechanisms that underlie the creation of acute lung injury (ALI) during and after one-lung ventilation (OLV) in the thoracic surgery patient [24]. Injury to the ventilated lung is primarily through hyperperfusion and ventilator-induced injury. High tidal volumes produce end-inspiratory lung overdistention and result in alveolar damage, increased alveolar-capillary permeability, and gross pulmonary edema [24]. Hyperperfusion, when the ventilated lung is exposed to high pulmonary blood flow, can result in capillary shear stress and disruption of the capillary endothelium. Injury to the non-ventilated, collapsed lung is primarily through ischemia–reperfusion injury, as well as shear stress on reventilation. Lung re-expansion from the atelectatic state exposes the alveolar units to significant mechanical stress and creates high shear forces affecting the adjacent alveoli [24]. Hypoperfusion and ischemia in the collapsed lung can result in microvascular permeability, capillary leak, and lung edema, while reperfusion injury is similar to hyperperfusion injury in the ventilated lung. Systemic factors affecting both lungs include the release of proinflammatory cytokines and reactive oxygen species (ROS), resulting in damage to the endothelial glycocalyx and a leaky alveolar-capillary membrane [24]. Surgical trauma and manipulation alone can cause alveolar damage. It is important to realize that OLV in any form is nonphysiologic and will result in some degree of lung injury, but protective OLV can be implemented to reduce the risk and severity of ALI in this specific patient population.

5.2 One-lung ventilation

The idea of isolated lung ventilation can be dated back as early as the late 19th century, and its birth and development have allowed for facilitation of complex thoracic surgical procedures, as well as extension of use into esophageal, mediastinal, orthopedic, and neurosurgical procedures [25]. OLV in its most basic form allows the anesthesiologist to control ventilation to each lung, deflating the operative (nondependent) lung and preferentially ventilating the non-operative (dependent) lung. OLV facilitates good surgical exposure of the collapsed lung in the thoracic patient, while ensuring adequate gas exchange of the ventilated lung and protecting it from contamination with surgical debris, pus, or secretions from the operative lung [26, 27]. OLV is not an all-or-nothing phenomenon, as the extent of lung deflation differentiates lung separation (adequate deflation) from lung isolation (complete deflation) [27]. Common indications include pulmonary resection, video-assisted thoracoscopic surgeries, biopsies of the lungs or lymph nodes, thoracic aortic surgery, esophageal surgery, mediastinal surgery, among many others.

5.3 Anesthesia equipment

OLV is typically achieved using either a double-lumen endobronchial tube (DLT) (Figure 1), or an endobronchial blocker (BBs) (Figure 2), although DLTs are the predominant technique utilized. Recent surveys conducted by the European Association of Cardiothoracic Anesthesiologists suggest that DLTs are preferred by a large majority (>90%) of thoracic anesthesiologists, with many of these experts (up to 30%) stating they never use BBs [26]. Despite the predominance of DLTs, users should still be familiar with and possess basic knowledge of BBs, as well as SLTs, to ensure safe management of OLV and ensure safety of the thoracic patient while on the operation table. Both DLTs and BBs can be used safely in most thoracic procedures, and choice of device is typically guided by patient-specific factors, operator preference and experience, etc.

Figure 1.

Typical double lumen tube (DLT) and appropriate positioning within the trachea and mainstem bronchi. Arrows indicating where to clamp each of the tracheal and bronchial lumens as detailed in section 4.3.

Figure 2.

Bronchial blocker and appropriate positioning within the trachea and main stem bronchi.

Single-lumen endobronchial tubes (SLTs) are another alternative, possessing a single lumen with a distal bronchial cuff and a proximal tracheal cuff. Both lungs can be ventilated when the proximal cuff is inflated and the tip of the SLT remains within the trachea, or the SLT can be advanced into one of the mainstem bronchi and OLV achieved with inflation of the distal cuff (proximal cuff remains deflated) [27]. These have fallen out of favor for reasons such as inability to aspirate secretions from the operative lung. Their use is mainly reserved for emergency situations intra-operatively (such as an initially unrecognized difficult airway) where securing the airway is the main priority, as this is performed quickest and easiest with a SLT; they can also be used in pediatric populations. Additionally, in situations where a patient has known anatomical abnormalities of the airway (e.g., after laryngeal or pharyngeal surgery, tracheostomy), the patient has a predicted or recognized difficult airway, or are at risk for vocal cord injury, use of SLTs would be a suitable option [27].

DLTs remain the gold standard technique for OLV in many thoracic surgical procedures, and their design is thanks to Frank Robertshaw in the mid-20th century, who settled on an almost universally adopted color-coding scheme with a red tracheal cuff and blue bronchial cuff [25]. Typical sizes available for adults range from 35 to 41 French; in general, a 37 Fr can be used in most adult women, whereas a 39 Fr can be used in most adult men [27]. Pediatric sizes do exist, 26 and 28 Fr, as well as a smaller 32 Fr option for smaller adults, although these three sizes are newer on the market relatively speaking. Once inserted to the optimal depth, the tracheal cuff should be inflated first, followed by confirmation of placement with the distal bronchial component sitting in the desired mainstem bronchus, this blue color easily identified in contrast to the pink bronchial mucosa by fiber-optic bronchoscopy. Confirmation that the tip of the bronchial lumen is sitting in the desired mainstem bronchus can be done by clamping the tracheal lumen, then auscultating and observing unilateral ascent of the ventilated hemithorax [27].

Following confirmation, the bronchial lumen is clamped to ventilate the tracheal lumen and the non-operative lung, deflating the operative lung. The bronchial cuff can then be inflated incrementally until the air leak disappears. Although placement can be confirmed by auscultation and observation alone, it is common practice confirm with fiber-optic bronchoscopy, as blindly placed DLTs can be malpositioned upwards of 50% of the time. Importantly, the margin of error for positioning a right-sided DLT is much less compared to a left-sided DLT, given the distance from the carina to the splitting of the upper lobe bronchus on the right (~2.5 cm) compared to the left (~5 cm) [27]. One challenge of DLT use is the lack of objective data and guidance for selection of appropriate size and optimal depth; chest x-ray, computed tomography, and ultrasound have all been suggested to measure tracheal diameter, factoring in patient sex and height to predict DLT size and depth [26, 27]. Undersized tubes can lead to auto positive end-expiratory pressure (PEEP) and pulmonary hyperinflation, failed lung collapse, or tube malposition, while oversized cuffs could potentially lead to serious airway complications such as trachea-bronchial rupture, although the incidence is <1% [26].

Advantages of DLTs include their wide applicability including bronchopulmonary lavage, rapid lung deflation-reinflation times, allowing for bronchoscopy of the non-ventilated lung, and their suitability for operation on both lungs even sequentially in the same surgery. They are inexpensive and easily disposable, allowing for safe, quick and accurate placement. Disadvantages include the higher risk of airway trauma and other adverse events, and occasional need for multiple tube exchanges in settings such as post-operative ventilation and in patients already intubated with a SLT.

Bronchial blockers allow for blocking of one main stem or lobar bronchus and resulting collapse of the lung or lobe distal to that blockage. These are better suited for patients with difficult airway anatomy, pediatric populations, or presence of a tracheostomy. BBs can be used in both nasal and oral intubations, can deflate selective lobes or segments, and can be removed at the conclusion of surgery without the need for tube exchange. Interestingly, transient post-operative symptoms such as sore throat, hoarseness, and irritating cough have been less reported with the use of BBs when compared to DLTs [27]. Disadvantages include limited options for adequate suctioning relative to DLTs, increased risk of balloon displacement, impossibility of differential lung ventilation, high price, and more limited availability.

5.4 Ventilatory protective strategies during one-lung ventilation

Despite being advantageous and useful for the surgeon, OLV subjects the patient to some degree of barotrauma, volutrauma, atelectatrauma, and oxygen toxicity, all of these contributing to ventilator-induced lung injury [28]. Acute ventilatory-induced lung injury and the PPCs that can result will have a strong effect on the morbidity and mortality of the thoracic patient. Ventilatory protective strategies are implemented to mitigate the risks of lung injury and reduce PPCs, usually encompassing the combination of positive-end expiratory pressures (PEEP), tidal volumes (TV), and alveolar recruitment maneuvers (ARMs). Only recently has the idea of individualized PEEP gained popularity, as it was historically set at fixed values, either high or low, with no verdict as to which was better to prevent PPCs. Individualized PEEP can prevent alveolar collapse in the dependent lung, increase the residual volume, improve the V/Q ratio and respiratory compliance, and reduce the shear stress damage caused by periodic opening and closing of the alveoli [28]. This allows for reduced PPCs, such as atelectasis, and better perioperative oxygenation when using an individualized PEEP. Fixed-setting PEEP, on the other hand, may lead to either over-distended or under-ventilated lungs.

Low, rather than high, tidal volumes during OLV have been shown in the clinical setting to decrease the expression of proinflammatory cytokines and their resulting alveolar damage and reduce the risk of postoperative respiratory failure [29]. Large tidal volumes >8–10 mL/kg are typically where you start to see increased inflammatory response, injury to the lungs, and increases in postoperative complications [30]. Lower tidal volumes around 4–6 mL/kg can be used to reduce airway pressures, maintaining driving pressures <25 cmH2O. Lower tidal volumes are associated with preserved gas exchange after OLV, as well as lower incidences of pulmonary infiltration and acute respiratory distress syndrome (ARDS) [30].

5.5 Management of Hypoxia

Thanks to improvements in lung isolation devices, patient positioning techniques, and newer anesthetic agents, the incidence of hypoxemia during OLV has significantly decreased since its early use, approximately 4–10% today compared to 25% in the 1970s [27, 31]. Although less frequent, it is still important to be able to properly manage hypoxemia intra-operatively and understand why it occurs in the first place. When the operative lung is deflated and excluded from ventilation, it becomes atelectatic but continues to be perfused by the pulmonary vasculature, creating a large ventilation-to-perfusion (V/Q) mismatch, and resulting obligatory pulmonary shunt. Hypoxemia results when SpO2 drops below 85–90%, or partial pressure of oxygen (PaO2) drops below 60 mmHg. The pulmonary vasculature detects these changes and responds with vasoconstriction, termed hypoxic pulmonary vasoconstriction (HPV), redirecting blood flow from the poorly ventilated regions of the operative lung to the well-ventilated regions of the non-operative, in an attempt to decrease the pulmonary shunt that was created. HPV is believed to reach its peak within 20–30 minutes of OLV, and the shunt fraction is estimated to be upwards of 35% by 30 minutes of OLV [27, 30]. It is intuitive, then, that any factors inhibiting HPV will worsen the V/Q mismatch and result in hypoxemia.

Risk factors for the development of hypoxemia during OLV can be separated into two categories: patient specific and surgery specific (Table 2). As is the case with many other operations and procedures, individuals with other comorbidities including cardiovascular, cerebrovascular, or pulmonary disease are at increased risk of hypoxemia and hypoxemia-induced complications. These patient factors include high BMI (>30 kg/m²), history of lung surgery on the contralateral side, low baseline PaO2, and normal preoperative spirometry (interestingly, COPD decreases the risk of hypoxemia). Surgery specific factors that increase the risk of hypoxemia during OLV include positioning (supine position) and side of the surgery (right-sided surgery with right lung collapse and left-sided ventilation). Generally speaking, healthy individuals (i.e., normal preoperative spirometry, age < 50 years, BMI <30 kg/m², non-smoker, absence of COPD or other major comorbidities) with normal cardiopulmonary function will tolerate transient episodes of desaturation and hypoxemia well without systemic acidosis or circulatory impairment [30]. That said, it is still important to recognize risk factors, recognize when it occurs, and address it appropriately.

Risk factors for the development of hypoxemia during OLV
Patient-specific
Cardiovascular, cerebrovascular, or pulmonary disease
BMI > 30 kg/m^2
History of contralateral lung surgery
Low baseline PaO2
Normal preoperative spirometry
Surgery-specific
Supine positioning
Right-sided laterality for surgery

Table 2.

Risk factors for the development of hypoxemia during OLV.

BMI (body mass index), PaO₂ (partial pressure of oxygen in the arterial blood).

Given the risk for hypoxemia during OLV, anesthesia providers should be familiar with the various techniques to identify and correct the cause (Figure 3). It is standard to pause from any nonurgent portion of the surgical procedure, restore two-lung ventilation, and increase the fraction of inspired oxygen (FiO2) to 100%. It is important to assess for common causes of hypoxemia such as malpositioning of the lung isolation device. This can be done using fiberoptic bronchoscopy to confirm visually the DLT/BB in optimal position. Fiberoptic bronchoscopy can also be used to inspect all ventilated bronchi and ensure the airway is clear of secretions [30]. After hypoxemia is treated and corrected, OLV can be re-established, and the surgery can move forward. Because persistently high FiO2 has been shown to cause lung injury secondary to its induction of an inflammatory response, oxidative stress, and lung edema, it is important to be judicious in the delivery of oxygen. The goal is to maintain adequate oxygenation while minimizing these deleterious effects of high FiO2, with most sources agreeing on trying to keep FiO2 at or below 60% when possible.

Figure 3.

Strategies for the management of hypoxemia during OLV. HFJV (high-frequency jet ventilation).

Some pharmacologic interventions have been suggested for the treatment of hypoxemia intraoperatively, although not yet widely adopted. Theoretically, inhaled nitric oxide (iNO) should improve V/Q mismatch via pulmonary artery dilation and increased blood flow to the ventilated lung, however this benefit has not been consistently shown and its routine use is therefore not recommended [30]. Inhaled anesthetics are known to inhibit HPV and worsen V/Q mismatch compared to intravenous anesthetics, so one would think using intravenous anesthetics to maintain general anesthesia would improve oxygenation. This has not consistently been shown to be the case, although volatile anesthetics such as sevoflurane have been shown to attenuate the inflammatory response in the lung and protect the endothelial glycocalyx, without worsening hypoxemia [27].

Alveolar recruitment maneuvers (ARM) before OLV initiation or shortly thereafter have been shown to improve arterial oxygenation and decrease pulmonary shunting as well as dead space, so it is conceivable that ARMs can also treat hypoxemia after it occurs [30]. This typically consists of ten consecutive breaths at a plateau pressure of 40 mmHg. This serves to reserve atelectasis through brief, controlled increases in airway pressure [30]. Incremental increases in PEEP of the non-operative lung, usually levels of 5–10 to a maximum of 20 cmH2O of PEEP, can also improve hypoxemia by opening atelectatic alveoli. It is well accepted that application of PEEP should be individualized to the patient during surgery, rather than generally aiming for high or low PEEP. Continuous positive airway pressure (CPAP) can also be applied to the nondependent, operative lung to improve oxygenation through passive mechanisms, usually starting at 5 cmH2O [27, 30].

5.6 Fluid management

The main goal of fluid management during the intra- and peri-operative periods of thoracic surgery is to minimize end-organ injury while also reducing and preventing postoperative ALI. This is done with targeted fluid administration, where euvolemia, rather than liberal fluid administration, is the goal in surgeries such as lung resection and esophagectomy, to achieve an ideal lung water state [27]. Practice over time has shifted away from the historical standard of liberal fluid administration, as the deleterious effects this can cause have been more documented and understood. Postoperative complications such as pulmonary edema, ARDS, pneumonia, reintubation, prolonged hospital and/or ICU stay, and generally increased morbidity and mortality, can all result from excessive fluid administration in the intra- and peri-operative periods [27]. On the other hand, aggressive fluid restriction can result in postoperative acute kidney injury (AKI), which is associated with increased morbidity. A universally accepted protocol or rule on ideal fluid management strategy has yet to be developed, and the topic remains controversial among surgeons in the field. Goal-directed fluid therapy (GDFT) is gaining favor most recently, using hemodynamic parameters such as pulse pressure variation and stroke volume variation to target fluid administration [27]. GDFT is not applicable to all surgical settings and procedures, however, and further progress needs to be made in fluid management strategies and protocol.

5.7 Regional Anesthesia

Thoracic epidural analgesia (TEA) has traditionally been considered the “gold standard” for postoperative pain control after thoracic surgery. TEA is not without significant risks, however, including hypotension, postoperative urinary retention, and muscle weakness [5]. Regional anesthesia was therefore developed as an alternative to TEA, and a multitude of thoracic wall fascial plane blocks have since been developed. There is evidence to suggest that many of these techniques are equivalent analgesia to TEA [32]. Furthermore, the widespread adoption of ultrasound has revolutionized regional anesthesia. Ultrasound has been instrumental in the development of fascial plane blocks, which rely on the passive spread of local anesthetic (LA) to target nerves, as its use can both guide and confirm needle placement and fascial spread of LA [33].

Regional anesthesia provides pain relief via unilateral afferent nerve blockade, affecting both the somatic and sympathetic nervous systems, thereby downregulating the stress response through decreased activation of the neuroendocrine system [34]. TEA also acts through similar neural mechanisms; however, the bilateral sympathetic blockade produced by TEA is significantly more likely to result in hypotension than is the unilateral effect of regional anesthesia [35]. This phenomenon makes regional blocks an especially attractive option in higher-risk cardiac patients with other comorbid conditions.

Other benefits of regional anesthesia include relative ease of performance and its safety when compared to TEA. The targets for injection are relatively distant from critical structures, resulting in minimal risk of spinal cord injury, epidural hematoma, major vascular injury, and lung or pleural damage [33]. There is the additional benefit that injections sites tend to be superficial and easily compressible, limiting the likelihood of expansile hematomas [36]. As such, thoracic wall blocks may also be considered in patients with coagulopathy, albeit with careful consideration of the risks and benefits. When compared to opioid-based postoperative pain regimens, regional anesthesia is associated with less sedation, less PONV, and less constipation, and thus encourages both earlier postoperative mobilization and earlier initiation of enteral nutrition [37, 38].

While the benefits of regional anesthesia are many, there are several drawbacks associated with fascial plane blocks. Epidural spread of local anesthetic is possible (such as with retrolaminar or erector spinae plane blocks), thus there is a potential concern for resultant hypotension, although the risk is far lower than with TEA [33]. The extent and intensity of pain blockade can be variable due to injection technique as well as several anatomic factors, such as contralateral and/or overlapping innervation [33]. Perhaps the most notable risk of fascial plane blocks is the risk of local anesthetic systemic toxicity (LAST), as relatively large volumes of LA into well-vascularized tissues where the systemic absorption is high thirty). The risk of LAST can be minimized by remaining within the maximum recommended weight-based LA dose limits, adding epinephrine to reduce the systemic absorption of LA, and closely monitoring patients for at least thirty minutes following LA injection with easy accessibility of LAST rescue medications [33].

There are numerous types of thoracic wall and fascial plane blocks available, and providers can tailor specific blocks to expected areas of postoperative pain for each procedure (Figure 4). A thorough description of each block is beyond the scope of this chapter; however, a brief review is useful to demonstrate the uses of more commonly used blocks. Included among this list are the intercostal nerve block (ICNB), the paravertebral block (PVB), the erector spinae plane block (ESPB), and the serratus anterior plane block (SAPB). Newer alternatives to the PVB include the retrolaminar block and the mid-point transverse process to pleura block (MTPB).

Figure 4.

Thoracic wall fascial plane blocks. PIP (parasternal-intercostal plane), SPB (serratus plane block), ESPB (erector spinae plane block), RLB (retrolaminar block), Tm (trapezius muscle), RMm (rhomboid major muscle), ESm (erector spinae muscle), SAm (serratus anterior muscle), Pmm (pectoralis minor muscle), TTm (transversus thoracis muscle).

The ICNB is perhaps one of the most widely utilized blocks given its effectiveness and relative ease of performance. It is most commonly performed intraoperatively by the surgeon prior to chest closure by sequential LA injection into the relevant intercostal spaces, thus interrupting the transmission of afferent pain signals [34]. Its attractiveness has been greatly enhanced by the introduction of liposomal bupivacaine, which allows for up to 96 hours of drug diffusion following a single injection [39]. Studies have shown that ICNB can provide equivalent analgesia to that of TEA [40], and its use has been demonstrated to decrease the risk of major pulmonary complications [41]. As previously noted, there is a risk of LAST with ICNB, as well as bleeding due to the proximity of the intercostal nerves to the associated intercostal arteries.

The PVB is another frequently used form of regional anesthesia in patients undergoing thoracic surgeries. It is performed on the side of surgery either by single injection or catheter placement for continuous infusion [34]. Both methods have been shown to lower postoperative pain scores, postoperative opioid consumption, and rates of PONV; however, continuous PVB can provide a longer duration of analgesia compared to the single injection technique [37]. It provides unilateral somatic and sympathetic analgesia via blockade of both the dorsal and ventral rami as well as the sympathetic chain [35]. It is thus safer to use than TEA given its diminished risk for causing hypotension. Notably, it may provide more intense and longer lasting analgesia compared to interpleural blocks [35].

Newer alternatives to the PVB include the retrolaminar block and MTPB. The retrolaminar block was developed as a simpler landmark-guided alternative to PVB, and entails injection of LA into the fascial plane that lies between the posterior surface of the thoracic lamina and the transversospinalis muscles [33]. Thus, this technique avoids the need to enter the true paravertebral space by forgoing the need to pierce the superior costotransverse ligament. The MTPB is similar to the retrolaminar block but involves LA injection just beyond the posterior aspect of the thoracic transverse processes while still remaining superficial to the superior costotransverse ligament [33]. The advantages of these two approaches are conferring a similar level of analgesia to PVB while carrying less risk of pleural puncture [33].

The ESPB involves injection of LA into the fascial plane between the thoracic transverse processes and the longissimus thoracis muscle [35]. This results in LA spread to the paravertebral and epidural spaces, as well as to the lateral cutaneous branches of the intercostal nerves [33]. Performance of ESPB confers lower postoperative active and passive pain scores, less PONV, and faster time to postoperative mobilization, and it has been shown to be non-inferior to PVB [37]. Additionally, it may be more specifically indicated if damage to the parietal pleural leaflet has occurred, which would preclude the use of PVB with catheter [37].

The SAPB is a relatively quick and easily performed technique and may be performed either superficial to or deep within the serratus anterior muscle [33]. Both techniques primarily target the lateral cutaneous branches of the intercostal nerves, although may also target the long thoracic nerve and/or thoracodorsal nerve as well depending on injection site and amount of LA infiltrated [35]. It can be performed anywhere between the anterior and posterior axillary lines between the second and seventh ribs. It has limited side-effects, although has been associated with slightly higher levels of opioid consumption when compared to PVB [37].

It is worth noting that these methods of regional anesthesia do little to alleviate the postoperative shoulder pain that stems from diaphragmatic irritation transmitted along the phrenic nerve. This commonly encountered symptom may be addressed anesthetizing the phrenic nerve intraoperatively via LA infiltration of the periphrenic fat pad above and below the hilum [34, 42]. Performance of phrenic nerve infiltration, however, should be contingent the absence of any respiratory contraindication and requires close postoperative monitoring [43].

In 2022, new PROSPECT (PROcedure-SPEcific Postoperative Pain ManagemenT) guidelines were released detailing recommendations for VATS. Either PVB or ESPB is recommended for all patients undergoing VATS, and SAPB may be used as a second-line choice; TEA is not recommended for any VATS procedures [37]. Whereas previous PROSPECT guidelines had recommended TEA when performing thoracotomy, PVB is now recommended for open thoracic surgeries as well [44].

6. Postoperative phase

6.1 Postoperative pain control

Postoperative pain can have a significant effect on patient outcomes following thoracic surgery. Acute pain alters pulmonary mechanics, such as diminished vital capacity and poor pulmonary toilet [45]. Such deleterious effects can lead to the development of atelectasis and pneumonia [1]. The long-term effects of inadequate analgesia are also important to consider, as circulating humoral inflammatory factors can induce central sensitization [32]. Consequently, poorly controlled postoperative pain has been linked to the development of chronic postoperative pain (CPOP), such as post-thoracotomy pain syndrome [7, 46]. As surgery on the chest is often considered among the most painful surgical procedures, adequate perioperative pain control is critically important, not only due to ethical considerations and patient satisfaction, but also for improving patient outcomes after thoracic surgery.

ERATS protocols are focused on attenuating the stress response and homeostatic disruptions that accompany major surgery [5, 7]. Tissue damage from surgery activates a systemic inflammatory response, thereby causing changes in the neuroendocrine, metabolic, and immune systems [47]. This pro-inflammatory immune imbalance can lead to organ dysfunction and, ultimately, higher rates of postoperative complication. Poorly-controlled postoperative pain can worsen this immune imbalance through further modulation of the neuroendocrine axis, thereby increasing the body’s stress response to surgery [32]. It is logical, therefore, that attenuation of pain perception with adequate analgesia has been shown to decrease levels of proinflammatory cytokines [34].

Multimodal analgesia is the cornerstone of postoperative pain control after thoracic surgery and is a major component of ERATS protocols. The combination of opioid and non-opioid analgesics, when used in conjunction with perioperative regional anesthesia, provides both a central and peripheral pain block, and has been shown to improve patient outcomes and decrease HLOS [32]. Multimodal pain control stems from the concept that several analgesic agents with different mechanisms of action may have synergistic effects in both the prevention and the treatment of acute postoperative pain [7]. Ideally, this also allows for the minimization of side effects of each individual anesthetic agent as well [5]. By utilizing non-opioid adjuncts, there is the additional benefit of reducing opioid-related side effects, such as constipation, PONV, and sedation.

The use of oral acetaminophen for postoperative analgesia is well established, and it is a vital component of ERATS pathways. At clinical doses, acetaminophen has few adverse effects or contraindications, and it can additionally be used safely in patients with renal failure [5]. Intravenous acetaminophen, having been approved by the United States Food and Drug Administration in 2010, has also been increasingly utilized for thoracic surgery [32].

Non-steroidal anti-inflammatory drugs (NSAIDs) are another frequently used adjunct in postoperative pain control. The combination of NSAIDs with acetaminophen has been shown to be more effective than either drug when used alone [48]. Intravenous ketorolac has powerful analgesic effects; however, the risks and benefits should be carefully weighed prior to administering, as its use has been shown to increase the volume of blood in thoracic drains [49]. Cyclooxygenase-2 inhibitors such as celecoxib are sometimes preferred in the postoperative setting due to their lessened effect on platelet function. There is a risk of renal failure with NSAID use, especially in patients with advanced age, hypovolemia, or pre-existing renal failure, and these risk factors may be present in patients undergoing thoracic surgery [5]. There is also the theoretical concern that the anti-inflammatory properties of NSAIDs may reduce the efficacy of surgical pleurodesis, although this phenomenon has yet to be proven in human studies. Animal studies, however, have demonstrated a significant reduction in the quality of pleural adhesions with NSAID use [50].

The use of N-methyl-D-aspartate (NMDA) antagonists has become increasingly popular given their analgesic properties. Ketamine should be considered for use in some postoperative patients; it is an especially attractive option for patients with a history of chronic opioid use [5]. The addition of low-dose ketamine to morphine in patient-controlled analgesia (PCA) was shown to reduce morphine use and improve early postoperative lung function in patients who had undergone thoracic surgery [51]. Although the NMDA receptor is known to play a role in central sensitization and neuropathic pain, studies have unfortunately failed to show a reduction in the incidence of CPOP with NMDA antagonist use [32].

Gamma-aminobutyric acid (GABA) analogs such a gabapentin and pregabalin, target neuropathic pain pathways, and while they have demonstrated efficacy in multiple neuropathic pain conditions, multiple studies have failed to show that these agents reduce either acute or chronic postoperative pain following thoracic surgery [5, 11, 32, 37]. Furthermore, it was not shown to alleviate the ipsilateral shoulder pain commonly seen in patients receiving TEA [5]. Therefore, neither PROSPECT nor ERAS/ESTS guidelines recommended postoperative gabapentinoid use.

Glucocorticoids have multiple actions, several of which (e.g., analgesic, antiemetic, antipyretic, anti-inflammatory) may be beneficial for patients having recently undergone surgery. However, the adverse effects of glucocorticoid use are also wide ranging, including gastric irritation, poor wound healing, sodium retention, and, notably, impaired glucose homeostasis leading to hyperglycemia [5]. There is no current consensus regarding the optimal dose that balances these advantages and disadvantages. And while the use of steroids such as dexamethasone and methylprednisolone has been shown to produce opioid-sparing effects and reduced pain scores in other surgical settings, there is limited procedure-specific evidence for their use in VATS [37]. Therefore, routine use of glucocorticoids is not recommended for patients undergoing thoracic surgery.

Postoperative opioid use, including PCA, should be minimized or, if feasible, avoided altogether [5]. When opioids are utilized, their benefits (such as analgesia and prevention of splinting) should be very carefully weighed against their multiple detrimental effects (including constipation, PONV, sedation, and ventilatory suppression). If opioids are necessary to achieve adequate levels of pain control, their use should be limited to rescue analgesia in cases of breakthrough pain.

6.2 Postoperative pulmonary complications

Postoperative pulmonary complications may lead to longer HLOS, worsen outcomes, and even increased mortality in patients undergoing thoracic surgery [52]. Thoracic procedures have a higher incidence of PPCs than non-thoracic surgical procedures. This is likely due to the nature of the operation and the patient characteristics, but also the result of interventions done in the intraoperative period. It is for this reason that ventilatory protective strategies are becoming more widely accepted, in attempts to decrease the incidence of such complications. The overall incidence of PPCs in the thoracic surgery patient population has been shown to be as high as 45.7% [53]. These complications range on a spectrum from more minor complications such postoperative supplemental oxygen and hypotension, to more severe complications such as respiratory failure and ARDS, unplanned invasive or non-invasive mechanical ventilation, pneumonia, unplanned ICU admission, increased HLOS, and hospital mortality (Table 3) [53]. Predictably, patients deemed moderate to high risk had a higher incidence of PPCs than those deemed low risk, this included increased age, higher BMI, the presence of COPD and other comorbidities, and male gender. Patients with higher preoperative ASA and ARISCAT scores also had higher incidences of PPCs. Interestingly, there seems to be no difference in incidence of PPCs when comparing OLV to two-lung ventilation (TLV), or when comparing open and endoscopic procedures [53]. It is important to understand the relationship between thoracic surgical procedures, the characteristics of this patient population, and the ensuing PPCs, so that we can develop scores and other strategies of risk prediction specific to this population and optimize the allocation of resources to minimize the incidence of such complications [53].

Postoperative Pulmonary Complications
Severe
Respiratory failure
Acute respiratory distress syndrome
Invasive ventilation
Non-invasive ventilation
Pneumonia
Unplanned ICU admission
Increased hospital length of stay
Hospital mortality
Minor
Supplemental oxygen
Hypotension
Transient arrythmias

Table 3.

Summary of postoperative pulmonary complications by severity.

7. Conclusion

As ERATS protocols continue to gain widespread adoption, they will continue to have a significant impact on how providers manage patients undergoing thoracic procedures. As more research into the efficacies of ERATS protocols emerges, these pathways will inexorably change in response, as they have already done since their inception. So too do advances in surgical and anesthetic techniques affect the course of ERATS protocols. The rise of minimally invasive thoracic surgery over the past three decades has revolutionized the field of thoracic surgery, mandating significant changes in evidence-based guidelines and new standards of care. More recently, the use of robotic surgery has risen and may well continue to gain traction, which may lead to updated guidelines in the future. Already, many of the components of ERATS are now received by a majority of patients undergoing thoracic surgery, such that some aspects may be considered “standard” rather than “enhanced” care [3]. As such, it is possible that we are moving towards a “post-ERATS” era, although this is more a distinction in nomenclature than in actual concept. As new standards of care are adopted, new methods for enhanced care will certainly emerge, although it is difficult to accurately predict the direction this will take. Regardless of the direction they take, such protocols are aimed at providing the best possible outcome for the thoracic surgery patient, and, although practices continue to evolve, providing safe and effective perioperative care for those undergoing thoracic surgeries will always remain at the forefront.

Conflict of interest

The authors declare no conflict of interest.