Wedge Resection, Lobectomy, Pneumonectomy

Introduction

The primary indications for resection of lung parenchyma include both malignant and benign conditions. Primary lung malignancy remains the leading cause of cancer-related deaths and lung resection surgery is the cornerstone of therapy for stage I and II (localized) primary lung nonsmall cell lung cancer malignancies, as well as for some patients presenting with stage III disease. The lung is the third most common location of metastasis from other tumor types and metastasectomy is indicated in selected cases, usually with lung sparing techniques.

Benign pathology requiring lung resection may include pulmonary blebs and bullae, benign masses and nodules, bronchiectasis, infectious lung disease, including mycobacterial infection, lung reduction surgery for patients with chronic obstructive pulmonary disease (COPD) and traumatic lung injuries. Sublobar wedge resection and segmentectomy are typical ­options for benign disease.

The type of lung resection performed will depend on the size and location of the disease, the primary pathology and the ability to obtain a safe negative margin. Lung resection can be broadly classified into anatomic and nonanatomic approaches. Anatomic resection requires selective ligation of the feeding vessels and airway for a segment or lobe of the lung. Examples of anatomic resection include pneumonectomy, lobectomy, segmentectomy, and sleeve resection. Segmentectomy (or sublobar resection) is a lung sparing operation but does not appear to provide equivalent long-term survival outcomes when compared with lobectomy, especially for larger tumors.

Nonanatomic wedge resections are accomplished without ligating individual airways and vessels. A wedge or slice of lung parenchyma containing the diseased tissue is stapled and removed using surgical linear cutting staplers.

In this chapter, the authors will provide a comprehensive overview of the perioperative care for patients undergoing lung resection surgery. We will combine relevant and recent evidence with the authors, institutional practice from a quaternary care academic center in Vancouver, Canada.

The Preoperative Evaluation of the Patient for Lung Resection Surgery (See Chapter 8 )

Major respiratory and/or cardiac complications occur in up to 15% to 20% of thoracic surgery patients and are predictors of prolonged postoperative length of stay after lobectomy. The broad goals of preoperative evaluation for the patient being considered for lung resection are to determine the patient’s likelihood to tolerate the procedure, as well as to quantify the overall risk of morbidity and mortality.

The American College of Chest Physicians (ACCP) and the British Thoracic Society (BTS) have published guidelines for preoperative assessment. ^, These guidelines recommend a thorough evaluation consisting of measurements of pulmonary function, gas exchange, cardiopulmonary fitness, as well as specialized testing. Concomitant comorbidities must be evaluated in a comprehensive and multidisciplinary fashion and optimized before the surgery. All patients scheduled for major lung resection are seen in the anesthesia consult clinic for a detailed evaluation. In this setting, we review all previous pulmonary and extrapulmonary testing, and, if necessary, request additional tests or consultation with internal medicine or pneumonologist colleagues and provide education for their perioperative rehabilitation. Reviewing patients well ahead of the surgical date also provides an opportunity to discuss more challenging cases with the surgeon if the preoperative evaluation raises doubts about a patient’s ability to tolerate the proposed resection, enabling additional testing or modifications to the surgical plan as required. It is at the time of the anesthetic consultation that we establish a plan for the postoperative disposition and advanced postoperative monitoring ( Box 40.1 ).

The anesthetic preoperative evaluation includes the standard elements of preoperative evaluation including past medical history, anesthetic and surgical history, allergies, medications, social history, and review of symptoms. The goals of the history are to highlight comorbidities that require further optimization. A targeted physical examination should include an upper airway assessment to help predict ease of mask ventilation and intubation, as well as an assessment of the pulmonary and cardiac systems to evaluate for the risk of volume overload, bronchospasm, and or active pulmonary infection. Examination of the limbs for adequacy of intravenous access and the back for palpable landmarks for planning of neuraxial pain modalities are also performed.

We subscribe to the “three-legged stool” approach for the preoperative assessment of patients having pulmonary resections ( Fig. 40.1 ). This assessment targets three areas of respiratory function: (1) respiratory mechanics, (2) pulmonary parenchymal function, and (3) cardiopulmonary reserve. From a physiologic standpoint these three areas evaluate oxygen transport: (1) into the alveoli, (2) into the blood, (3) and to the tissues, respectively.

Pulmonary function testing, including the forced expiratory volume in 1 second (FEV ₁ ) and diffusing capacity for carbon monoxide (DLCO), is routine for the vast majority of patients presenting for lung resection surgery. Minor wedge resections in otherwise healthy individuals arguably do not require formal pulmonary function testing. FEV ₁ and DLCO are valiant predictors for both open and video-assisted thoracic surgery (VATS) resections. The percent of predicted FEV ₁ is a value that is corrected for age, sex, and height and is a strong predictor of postoperative complications and correlates with respiratory impairment in patients with COPD. The single greatest predictor of postlung resection pulmonary complications is the predicted postoperative FEV ₁ (ppoFEV ₁ %) (BTS 2001), which is calculated as follows:

There are 6, 4, and 12 subsegments in the right upper, middle and lower lobes, respectively, and 10 subsegments each in the left upper and left lower lobes ( Fig. 40.2 ). The amount of functional lung tissue removed is calculated by the total number of subsegments associated with the lung resection and assumes that all segments contribute equally to gas exchange, which may not be the case if the segments being resected are not contributing to gas exchange. For example, a patient with a preoperative FEV ₁ % of 60 undergoing a left upper lobectomy will have 10 of 42 subsegments removed; his ppoFEV ₁ % is therefore 60 × (1 − 10/42) = 45.

The same calculation can be used to determine the predicted postoperative DLCO (ppoDLCO%) to predict gas exchange abnormalities. Baseline arterial blood gas analysis is a more invasive ancillary test of gas exchange. Arterial PaO2 is not widely considered an important predictor of postoperative complications whereas baseline hypercapnia (arterial PaCO2 <45) often coexists with a low ppoFEV ₁ or maximal oxygen consumption (VO ₂ max) and may be a contraindication for lung resection in this population.

Patients with ppoDLCO% or ppoFEV ₁ % greater than 40% have a low risk of postresection respiratory complications whereas those with values less than 30% are at high risk for postoperative morbidity. Guidelines from the European Respiratory Society and the European Society of Thoracic Surgery (ERS/ESTS) use a cutoff value for ppoFEV ₁ and ppoDLCO of 30% (rather than 40%) based on what these societies considered widespread improvements in surgical technique. If either ppoFEV ₁ or ppoDLCO are less than 30%, an exercise test is warranted to consider the decision of the suitability for resection. The lowest acceptable value of ppoFEV ₁ % to tolerate lung resection as reported by a high volume lung resection surgery center was 20%. The ppoFEV ₁ % value has some limitations, including the fact that actual ppoFEV ₁ % can exceed the calculated value at 6 months following surgery because the resected segments may be diseased and/or emphysematous and therefore contribute little to preoperative lung function.

Patients at elevated risk (ppoFEV ₁ % <40) should undergo complete pulmonary function testing, ventilation/perfusion scans and a functional assessment, such as cardiopulmonary exercise testing, stair climbing or 6-minute walk test (6MWT). Formal cardiopulmonary exercise testing to determine the VO ₂ max is the most useful predictor of postresection outcome. The ACCP and the ERS/ETST both consider a VO ₂ max less than 10 mL/kg/min to be high risk for postoperative morbidity and mortality whereas patients with a VO ₂ max greater than 20 mL/kg/min have a low risk of postoperative respiratory complications even for pneumonectomy. VO ₂ max values between 10 and15 mL/kg/min indicate an increased mortality risk and suitability for surgery should therefore take into account the entirety of preoperative testing (ppoFEV ₁ , ppoDLCO) and additional patient comorbidities. Licker et al. in a retrospective observational study included 210 patients with FEV ₁ less than 80% who were submitted to lung resection. The VO ₂ max was a predictor of cardiopulmonary complication and death at the multivariate analysis, including preoperative clinical, surgical, and ergometric variables. Patients with a VO ₂ max <10 mL/kg/min had a risk of total morbidity, cardiovascular morbidity, and cardiac morbidity of 65%, 39%, and 35%, respectively, in case of major resection ( Fig. 40.3 ).

Alternatives to formal cardiorespiratory exercise testing include the 6MWT and stair climbing. The VO ₂ max may be estimated from a 6MWT value by taking the total distance walked on flat ground in 6 minutes and dividing by 30. For example, walking 900 m total divided by 30 corresponds to a VO ₂ max of 30 mL/kg/min. Stair climbing at the patient’s own pace corresponds to VO ₂ max, such that a person able to climb five flights or more has a VO ₂ max over 20 mL/kg/min, and two flights of stairs are equivalent to 12 mL/kg/min.

Regional lung function testing, such as ventilation perfusion lung scanning, is indicated in the patient undergoing major lung resection with a ppoFEV ₁ % less than 40 or when there is reason to confirm that the lung to be removed is diseased and not contributing fully to preoperative lung function. In this situation, a ppoFEV ₁ is more accurately calculated by using the preoperative FEV ₁ % and the perfusion value of the remaining (nonresected) lung. For example, for a patient presenting for a left pneumonectomy with preoperative FEV ₁ % 74 and perfusion of the left lung 35% and right lung 65% the ppoFEV ₁ % is 74 × 0.65 = 48, which corresponds to an acceptable value ( Box 40.2 ).

The combination of preoperative respiratory assessment tools is better than any single test and provides valuable information for the thoracic anesthesiologist to help predict postoperative outcome and to plan intra- and postoperative management. For patients with ppoFEV ₁ % greater than 40, a standard weans and extubation in the operating room would generally be considered safe. For patients with values between 30 and 40, information from functional and other ancillary tests should be factored into determining suitability for lung resection surgery and may require a staged wean from mechanical ventilation in the postanesthesia care unit or in the intensive care unit. As with all patients, optimal analgesia with an epidural or paravertebral catheter along with normothermia, normal metabolic parameters, and minimization of long acting sedatives will assist with extubation and early postoperative lung function. For patients with ppoFEV ₁ % 20 to 30, more conservative management may be warranted, including delayed extubation and planned transfer to an intensive care unit.

ACCP Physiologic evaluation resection algorithm is depicted in Fig. 40.4 .

Next to respiratory complications, cardiac complications are the most common source of postoperative complications in lung resection patients. The most common cardiac complications following lung resection surgery are myocardial ischemia and arrhythmias. A thorough cardiac evaluation is guided by the American College of Cardiology/American Heart Association, the European Society of Cardiology/European Society of Anaesthesiology and the Canadian Cardiovascular Society guidelines on preoperative assessment for noncardiac surgery. These guidelines recommend a baseline electrocardiogram (ECG), assessment of functional status, determination of preoperative cardiac risk using the revised cardiac risk index (RCRI), preoperative brain natriuretic peptide (BNP) testing and selective additional cardiac risk stratification, including stress testing and echocardiography. In patients with elevated baseline risk and/or positive BNP, postoperative myocardial injury surveillance should be conducted with serial ECG and troponins on postoperative day 1 through 3. Patients should continue their cardiac medications, including beta blockers and antiarrhythmics up to the day of surgery.

In the Lee cardiac risk classification evaluated among 4513 patients, the incidence of a major cardiac complication increases with a higher cardiac risk index (1–4), which is based upon six independent predictors, including high-risk type of surgery, history of ischemic heart disease, history of heart failure, history of cerebrovascular disease, preoperative treatment with insulin, and preoperative serum creatinine over 2.0 mg/dL (177 mol/L). Thoracic procedures are considered high-risk surgery, similar to major intraabdominal procedures and abdominal aortic aneurysm resections, and therefore classified at least as risk class 2. Higher cardiac risk indices are indicative of a statistically significant increase in cardiac complications amongst thoracic surgery patients. COPD is a common comorbidity in patients undergoing lung resection surgery and care should be taken to thoroughly evaluate for the presence of bronchospasm, atelectasis, infection, and pulmonaryedema. These comorbidities should be adequately optimized before lung resection surgery. Preoperative treatment may be required, including bronchodilators, steroids, antibiotics, and diuretics. Smoking cessation counseling is an important component of the preoperative consultation, as quitting smoking before surgery decreases wound infection postoperative pulmonary complications (PPCs) and improves pulmonary recovery. Pulmonary rehabilitation before lung resection surgery, including moderate to intense exercise which improves aerobic capacity, physical fitness, and quality of life, and may reduce postoperative complications and hospital length of stay. Pouwels et al. evaluated 11 studies with a methodologic quality ranging from poor to good. The most important finding of this systematic review was that PET based on moderate to intense exercise in patients scheduled for lung surgery has beneficial effects on aerobic capacity, physical fitness, and quality of life. The patient with pulmonary malignancy may present with additional factors that may complicate care and these should be sought out and evaluated. For example, squamous cell cancers (SCC) can grow to a large size, which may produce a compression effect on adjacent airways and pulmonary vessels leading to airways obstruction, postobstructive pneumonia, superior vena cava syndrome or cavitation and hemoptysis. Hypercalcemia is sometimes seen in patients with SCC. Small cell lung cancers are associated with several paraneoplastic conditions, including hyponatremia from the syndrome of inappropriate antidiuretic hormone secretion, a Cushing syndrome from excess cortisol secretion and rarely Lambert-Eaton myasthenic syndrome. Carcinoid tumors that are found in the central airways can cause airway obstruction or hemoptysis, as well as a carcinoid syndrome from the secretion of vasoactive mediators, although rarely seen in lung cardioid, can precipitate hemodynamic collapse, coronary vasospasm, or bronchospasm. All patients with malignancy should be assessed with the 4 Ms in mind: mass effect of the tumor especially on airways and great vessels; the side effects of chemotherapeutic medications , including respiratory toxicity from bleomycin or cardiac or renal toxicity from other agents; metabolic effects related to paraneoplastic disorders; and other organ dysfunction related to metastatic disease . Finally, placement of neuraxial or regional nerve block catheters requires exclusion of pre-existing coagulopathy and discontinuation of anticoagulant medication in accordance with the American Society of Regional Anesthesia recommendations. Anticoagulant medications should therefore be reviewed and held for an appropriate preoperative interval.

An important part of the preoperative evaluation is the review of the preoperative imaging, particularly the computed chest tomography (CT) scan. The preoperative CT provides valuable information that can be used to carefully plan airway management and anticipate difficulties with endobronchial tube placement, oxygenation, or ventilation during one-lung ventilation (OLV). Anesthesiologists should learn to evaluate the images themselves, as the radiologist’s report may not comment on specific factors relevant to lung isolation. For example, if a left-sided resection or pneumonectomy is planned or the patient presents with a left mainstem bronchus tumor, a left-sided double lumen tube would be contraindicated. The evaluation of central airway anatomy is also important in patients presenting for a subsequent lung resection. For left-sided double lumen tube placement, the left mainstem bronchus diameter can be measured on the CT scan and be used to guide the selection of double-tumen tube size. Radiologic lung pathology can be identified on chest CT and can indicate the presence of bullous lung disease or blebs, fibrotic changes, or interstitial patterns, including pulmonary edema, atelectasis, consolidation, or pleural disease including effusions. The size and precise location of any lung mass, particularly when centrally located, may yield helpful clues as to the surgical difficulty with resection and the likelihood of conversion from thoracoscopic to open approaches. Mass effect on great vessels, including the superior vena cava, brachiocephalic veins, or pulmonary arteries, can alter the plan for venous access, such as placement of additional access in the lower extremities. Extrapulmonary pathologies, including coronary artery calcification, severe cardiac chamber enlargement, pulmonary artery enlargement, or pericardial effusion, can be seen. Finally, review of the imaging will facilitate neuraxial catheter placement, both the depth of laminae for paramedian epidural placement and the absence of spinal deformities ( Table 40.1 ) .

Monitoring (See Chapters 11,12 )

Basic monitoring for all patients undergoing lung resection surgery will consist of pulse oximetry, noninvasive blood pressure (NIBP) cuff and five-lead electrocardiogram and continuous end-tidal carbon dioxide (CO2), as well as ventilator pressure and flows after initiation of positive pressure ventilation in accordance with national society guidelines.

Direct or invasive arterial catheter monitoring is appropriate in most patients and in particular in patients with comorbidities that require close monitoring of hemodynamics and for all patients undergoing the dissection of mediastinal vessels in more extensive procedures, such as lobectomy or pneumonectomy. Direct arterial monitoring allows for a reliable and continuous assessment of blood pressure, and intravascular volume status during lung resection surgery. Whether waveform analysis can provide information on cardiac contractility is controversial. Arterial cannulation before the induction of anesthesia allows for baseline blood gas sampling, particularly important in patients with COPD, if not already performed, as well as periodic sampling during and after the lung resection as warranted. Having baseline arterial blood gases (ABGs) are important to define what values are acceptable when the decision for extubation is planned. Central venous catheters are appropriate in patients for whom intra- and/or postoperative vasopressors are necessary, for more secure intravenous access or as an option for larger volume fluid administration.

Pulmonary artery catheters (PAC) and transesophageal echocardiography (TEE) are more invasive monitoring modalities that may be beneficial in certain situations. For example, a PAC in the patient with moderate to severe pulmonary hypertension and right ventricular dysfunction will better allow the anesthesiologist to titrate pulmonary vasodilator and inotropic therapies according to pulmonary artery pressure, cardiac output, and mixed venous oxygen saturation. TEE is gaining more traction as a perioperative hemodynamic monitor because it is a granular technique for guiding resuscitation. It would allow continuous monitoring of both right and left ventricular systolic and diastolic function, regional wall motion, valvular heart function, intracardiac shunts, fluid responsiveness and fluid tolerance, systemic vascular resistance, mass effect during surgery, monitoring for the extent and the changes in the pericardial or pleural fluid collections, as well as diagnosing causes of hypoxemia.

At our center we customize monitoring based on the clinical situation. In addition to the standard intraoperative monitors, all patients receive a temperature monitoring device and neuromuscular monitor. We place urinary catheters in patients undergoing major lung resections or if they receive a thoracic epidural. We place arterial catheters, usually in the dependent radial artery, for all patients undergoing lobectomy and pneumonectomy procedures and for patients with significant cardiac disease for less extensive lung resections. Central venous catheters (CVCs) are reserved for the pneumonectomy patient, the patient with a concomitant mediastinal mass, and if continuous vasopressor or inotropic therapy is thought to be necessary. The CVC is best placed on the operative (nondependent) side to avoid kinking and obstruction from the patient’s head and neck. It also eliminates the potential pneumothorax in the case of dependent lung inadvertent needle puncture, although this complication is largely avoided by the use of direct continuous needle tip viewing with ultrasound. For the most part, PAC and TEE are seldom used outside of lung transplantation; however, we will consider these modalities during aggressive and extensive resections or in the patient with severe cardiac disease.

The advancements in ventilator technology have resulted in more granular monitoring of respiratory mechanics. Capnometry is mandatory and can identify inspiratory and expiratory flow patterns, airways obstruction associated with lung isolation devices, a sudden drop in cardiac output, and for the monitoring the degree of permissive hypercapnia, which is common during OLV. Spirometry allows for the continuous monitoring of flows, pressures, and volumes, which can provide valuable information on the malpositioning of airway devices, the development of autopositive end-expiratory pressure (PEEP), the severity of pulmonary air leaks following lung resection and perhaps most importantly to prevent the incidence of ventilator-associated lung injury. Respiratory compliance and driving pressure (plateau pressure—PEEP) measurements allow for the individualization of ventilatory strategy as recommended in recent guidelines. Evidence suggests that reduction of PPCs frequently associated with substantial morbidity and mortality can be reduced by using lung-protective ventilation strategies intraoperatively. Young et al. selected seven experts and produced 24 questions concerning preoperative assessment and intraoperative mechanical ventilation for patients at risk of developing PPCs. An expert consensus was reached for 22 recommendations and four statements among them: (1) a dedicated score should be used for preoperative pulmonary risk evaluation; and (2) an individualized mechanical ventilation may improve the mechanics of breathing and respiratory function, and prevent PPCs. The ventilator should initially be set to a tidal volume of 6 to 8 mL/kg predicted body weight and PEEP 5 cm H ₂ O. PEEP should be individualized thereafter. When recruitment maneuvers are performed, the lowest effective pressure and shortest effective time or fewest number of breaths should be used. We advise individualizing both PEEP and tidal volume during OLV as guided by driving pressure and pulmonary compliance.

Methods of Lung Separation (See Chapter 16 )

In brief, lung isolation is required during lung resection surgery to facilitate surgical exposure and produce a quiet surgical field. The choice of lung separation device should take into account several perioperative factors, including the nature and location of the lung resection, the upper and lower airway anatomy, the presence or risk for pulmonary infection, bleeding, or pulmonary air leak. Whether the patient is already intubated or will require postoperative ventilation, and the provider’s experience and preference. Successful lung separation device placement requires a thorough understanding of tracheobronchial anatomy and expertise with fiberoptic bronchoscopy. An excellent resource for anesthesiologists to improve their knowledge of airway anatomy and bronchoscopy is available online at www.thoracic-anesthesia.com .

Double-lumen tubes (DLTs) and bronchial blockers (BBs) placed through a single-lumen ETT are the two most common methods used for lung separation during lung resection surgery and each have their advantages and disadvantages ( Table 40.2 ). Left-sided DLTs are the most commonly used device at our center for lung resection surgery because of the ease of access to either lung for bronchoscopy, suction, continuous positive airway pressure (CPAP), or ventilation. BBs can be used for anatomical or nonanatomic resections, in patients presenting to the operating room with an ETT or tracheostomy in-situ or patients with irregular tracheobronchial or difficult upper airway anatomy where DLT placement is difficult or impossible.

Right-sided DLTs are less commonly selected because of the smaller margin of error for placement because of the shorter right mainstem bronchus and a potential tube migration resulting in inadequate ventilation or loss of isolation. In a small minority of patients, the right upper lobe bronchus may originate from the carina or within the trachea. Right-sided DLTs should be placed during left pneumonectomy, distorted left mainstem bronchus anatomy (internal or external intraluminal left bronchus compression, such as in thoracic aortic aneurysm) or when the site of the surgery involves the left mainstem bronchus (sleeve resection, pneumonectomy, tracheobronchial disruption). Single-lumen tube for lung isolation may be used when immediate lung isolation is required and access to specialized lung isolation equipment is not available. Some institutions used right-sided double lumen tubes for all left-side procedures or vice versa. It is standard practice to confirm the position of the lung isolation device with a 4.0-mm fiberoptic bronchoscope; these are widely available today, also in disposable form.

Airway trauma from the placement of lung separation devices is fortunately rare but can be associated with significant morbidity and mortality. Airway trauma can be reduced through a thorough assessment of tracheobronchial anatomy, by choosing an appropriately sized DLT ( Table 40.3 ), and by using care during placement and cuff inflation. We recommend routinely reviewing the preoperative CT scan specifically for pathology and anatomic distortion of the lower airways, using bronchoscopy routinely to assist in placement especially when resistance is encountered and carefully inflating the cuff under direct visualization. Removing the stiff stylet after the distal tip of the DLT passes through cords and avoiding nitrous oxide are additional recommendations.

Fluid Management (See Chapter 21 )

The ideal strategy for fluid administration during lung resection surgery is to balance the replacement of fluid losses to maintain cardiac output and oxygen delivery to the tissues with the avoidance of tissue hypoperfusion and potential acute kidney injury (AKI). Excessive fluid delivery is associated with expansion of the extravascular compartment and precipitates tissue edema, increases the risk of acute lung injury (ALI) and delays recovery. A sensible approach to fluid management during lung resection surgery is to balance these two extremes, avoid overly restrictive or liberal fluid regimes, and maintain euvolemia. This is an approach endorsed by the enhanced recovery after surgery (ERAS) and ESTS ERAS guidelines for thoracic surgery.

To achieve euvolemia throughout the perioperative setting the patient should present to the operating room in a euvolemic state. This is facilitated by the consumption of an oral carbohydrate drink up to 2 hours before surgery. If blood loss is minimal, we limit total intraoperative intravenous fluid to less than 6 mL/kg/h (500–1500 mL) to reduce PPC. Fortunately, patients receiving less than 2 to 3 mL/kg/h of fluid intraoperatively do not experience a greater incidence of AKI, and fluid boluses to treat oliguria do not seem to affect postoperative renal function. Intravenous fluids should be replaced by enteral fluids as soon as possible in the postoperative period. Balanced crystalloids are preferred to 0.9% saline solution.

In the setting of hypotension related to anesthetic agents and neuraxial blockade and assuming euvolemia has been achieved, vasopressors may be used to enhance tissue perfusion although additional fluid boluses may be necessary if hypoperfusion ensues. Using cardiac output monitors including pulse contour analysis to guide fluid administration during OLV and an open chest at the present time is lacking in evidence. ^,

Patients scheduled for elective lobectomy at our center consume clear, carbohydrate rich fluids until their arrival to hospital and typically receive less than 1–1.5 liter of fluid in the operating room. In the setting of intraoperative hypotension or hypoperfusion, which may occur when epidural local anesthetic agents are administered, we administer boluses and/or low dose infusions of vasopressors, such as phenylephrine or norepinephrine. A maintenance intravenous fluid infusion is provided postoperatively until the patient resumes enteral nutrition. In the case of intraoperative hemorrhage or prolonged surgery, intravascular volume is replaced with a combination of balanced crystalloids, albumin and rarely packed red blood cells. Fluid administration is guided by routine monitors and clinical intuition rather than noninvasive cardiac output monitors, such as pulse contour analysis.