Anesthetic Considerations in Candidates for Lung Volume ...

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Anesthetic Considerations in Candidates for Lung Volume ...

  1. 1. Anesthetic Considerations in Candidates for Lung Volume Reduction Surgery Neil W. Brister1, Rodger E. Barnette1, Victor Kim2, and Michael Keresztury1 1 Department of Anesthesiology, Temple University Hospital, Philadelphia, Pennsylvania; and 2 Department of Pulmonary and Critical Care Medicine, Temple Lung Center, Temple University Hospital, Philadelphia, Pennsylvania The administration of anesthesia to patients undergoing lung vol- ume reduction surgery (LVRS) requires a complete understanding of the pathophysiology of severe chronic obstructive pulmonary dis- ease, the planned surgical procedure, and the anticipated postoper- ative course for this group of patients. Risk factors and associated morbidity and mortality are discussed within the context of patients with obstructive pulmonary disease in the National Emphysema Treatment Trial having surgical procedures. Preoperative evaluation and the anesthetic techniques used for patients undergoing LVRS arereviewed, as are monitoringrequirements. Intraoperative events, including induction of anesthesia, lung isolation, management of fluid requirements,and optionsfor ventilatory supportarediscussed. Possible intraanesthetic complications are also reviewed, as is the optimal management of such problems, should they occur. To min- imize the potential for a surgical air leak in the postoperative period, positive-pressure ventilation must cease at the conclusion of the procedure. An awake, comfortable, extubated patient, capable of spontaneousventilation,isonlypossibleifthereiscarefulattentionto pain control. The thoracic epidural is the most common pain control method used with patients undergoing LVRS procedures; however, other alternative methods are reviewed and discussed. Keywords: preoperative assessment; anesthesia techniques; lung isolation; pain control The anesthetic management of the patient with emphysema un- dergoing lung volume reduction surgery (LVRS) has been de- scribed as ‘‘challenging.’’ However, perioperative complications can be minimized if one understands the unique pathophysiology of emphysema and how it increases risk during LVRS. Emphysema and severe airflow obstruction, coupled with the need for general anesthesia, positive-pressure ventilation, and one-lung ventilation (OLV) can lead to severe gas trapping or dynamic hyperinflation upon induction or during surgery. Dynamic hyperinflation or pneumothorax can have sudden and severe hemodynamic consequences. Additionally, patients with emphysema have limited exercise capability, are older, and have a long history of heavy smoking; thus, they are at increased risk for occult coronary artery disease, which can manifest itself abruptly in the operating room. Because of severe parenchymal lung injury, the possibility of postoperative air leak secondary to disruption of the suture line or adjoining lung tissue is a significant risk. For that reason, rapid emergence from anesthesia and early extubation in the operating room are two of the primary goals of the anesthesi- ologist. To accomplish early extubation, the anesthesiologist must use short-acting anesthetic agents, employ appropriate invasive and noninvasive monitoring, provide excellent post- operative pain control, and maintain the patient in a euvolemic, normothermic state. PREOPERATIVE EVALUATION Assessment of risk for postoperative pulmonary complications (PPC) is crucial to evaluating the patient with advanced em- physema being considered for LVRS. The presence of obstruc- tive lung disease has been shown to be a significant risk factor for PPC, with reported relative risks varying from 2.7 to 4.7 (1). Furthermore, LVRS is associated with significant mortality and morbidity. Before the National Emphysema Treatment Trial (NETT), reported operative mortality rates for LVRS varied from 0 to 19% (2–5). This variability was most likely due to differences in patient population, study design, surgical tech- nique, surgeon experience, and perioperative management. The NETT research group recently reported an operative mortality rate (deceased within 90 d of LVRS) of 5.5% and a major pulmonary morbidity rate of 29.5% (6). The population ana- lyzed excluded patients found to be at high risk for death after LVRS with little functional benefit (patients with FEV1 < 20% predicted and either homogeneous emphysema or diffusing capacity of carbon monoxide [DLCO] < 20% predicted); this subgroup of patients had a 30-day mortality rate of 16% (7), but included patients with non–upper lobe–predominant emphy- sema and high exercise capacity during maximum cycle ergo- metry testing after rehabilitation. This latter profile was also found to predict significant risk for mortality with LVRS (8). LVRS is a major thoracic surgical procedure performed on patients with limited pulmonary reserve, many of whom have other comorbidities, which may put them at added risk for com- plications after LVRS. Few studies have examined risk factors for complications after LVRS specifically, but those that have been performed corroborate prior reports on the perioperative risk factors for thoracic surgery. Predictors of mortality after LVRS as reported by others are summarized in Table 1. In a study of 47 patients with severe emphysema (FEV1, 23.4 6 1% predicted mean 6 SD), Szekely and colleagues (5) found a six-minute-walk distance of less than 200 m and a resting PaCO2 greater than 45 mm Hg to be risk factors for unacceptable post- operative outcome, defined as death within 6 months or a hos- pital course of greater than 3 weeks; however, no significant correlation was found between lung function and outcome. In contrast, O’Brien and colleagues (9) found no difference in mor- tality, and similar improvements in lung function and exercise capacity in 15 patients with hypercapnic emphysema (PaCO2 , 58 6 7 mm Hg) compared with a population with eucapnea. Chatila and colleagues (10) found increased age, increased dura- tion of anesthesia, and presence of coronary artery disease to in- crease the risk of postoperative respiratory failure with LVRS. Naunheim and colleagues (7) analyzed risk factors for oper- ative morbidity and mortality in the patients in the NETT after (Received in original form September 5, 2007; accepted in final form November 5, 2007) The National Emphysema Treatment Trial (NETT) is supported by contracts with the National Heart, Lung, and Blood Institute (N01HR76101, N01HR76102, N01HR76103, N01HR76104, N01HR76105, N01HR76106, N01HR76107, N01HR76108, N01HR76109, N01HR76110, N01HR76111, N01HR76112, N01HR76113, N01HR76114, N01HR76115, N01HR76116, N01HR76118, and N01HR76119), the Centers for Medicare and Medicaid Services (CMS), and the Agency for Healthcare Research and Quality (AHRQ). Correspondence and requests for reprints should be addressed to Neil W. Brister, M.D., Ph.D., Temple University Hospital, Department of Anesthesiology, 3401 N. Broad Street, Philadelphia, PA 19140. E-mail: neil.brister@temple.edu Proc Am Thorac Soc Vol 5. pp 432–437, 2008 DOI: 10.1513/pats.200709-149ET Internet address: www.atsjournals.org
  2. 2. excluding those found on interim analysis to be at high risk of death after LVRS (patients with FEV1 < 20% predicted and either homogeneous emphysema or DLCO < 20% predicted). In those not considered to be high risk, only age, FEV1, and DLCO (relative odds, 1.05, 0.97, and 0.97, respectively) were found to be risk factors for major pulmonary morbidity, defined as tra- cheostomy, failure to wean from mechanical ventilation, rein- tubation, pneumonia, and mechanical ventilation for 3 days or longer. In contrast to earlier literature, the analysis of NETT data did not reveal hypercapnia or poor exercise tolerance to be predictors of worse outcome. This may reflect trial design, with the intentional exclusion of those with a PaCO2 greater than 60 mm Hg (55 mm Hg in Denver) and a six-minute-walk distance of 140 m or less (8). Interestingly, a non–upper lobe–predominant distribution of emphysema did not increase the risk for PPC, but did increase operative mortality (relative odds, 2.99; P 5 0.009) and cardiovascular morbidity (relative odds, 2.67; P , 0.001). Careful assessment for cardiac disease before selection for LVRS is also necessary. A high degree of coexistent coronary artery disease exists in chronic obstructive pulmonary disease (COPD) (11). Numerous studies have demonstrated an inverse association between reduced FEV1 and an increased cardiovascular mortal- ity, with relative risks ranging from 1.10 to 2.11 (12). The Lung Health Study found increases in all cause mortality (14%), car- diovascular mortality (28%), and nonfatal coronary events (20%) for every 10% decrease in FEV1 (13). To better characterize cardiovascular risk in the patient with emphysema undergoing LVRS, a pharmacologic stress test is recommended to screen for occult cardiac ischemia. Exercise stress tests are usually inadequate, as many patients with ad- vanced emphysema are unable to attain heart rates that defin- itively exclude cardiac ischemia. In addition, many patients have abnormal baseline electrocardiograms, making interpretation dif- ficult. If clinical suspicion is high, and/or a pharmacologic stress test is equivocal or submaximal, coronary angiography should be considered. LVRS carries a risk of significant cardiac stress, and intraoperative myocardial infarction has been reported (14). The use of b-blockers and nitrates throughout the perioperative pe- riod should be considered. Although cardioselective b-blockers are tolerated in patients with severe COPD (15), close monitor- ing for bronchospasm is warranted. PERIOPERATIVE COURSE All patients should be maximally treated with long-acting bron- chodilators, including on the day of surgery. Preoperative bron- chodilator treatment in patients with COPD results in a decrease in PPC (16, 17). Patients should maintain long-term abstinence from cigarette smoking before surgery. The risk of developing PPC has been shown to decrease significantly after 8 weeks of smoking cessation (17), and is increased in those who continue to smoke (18). In addition, it is recommended that all patients un- dergo pulmonary rehabilitation before LVRS. This will increase patients’ endurance and exercise capacity and aid in early ambu- lation after surgery. Postponement of surgery should be consid- ered if medical treatment of COPD is suboptimal or withheld, or if a recent upper respiratory tract infection or COPD exacerba- tion is present. Perioperative stress–dose steroids should be con- sidered in those patients receiving preoperative steroid therapy. INTRAOPERATIVE CARE If the patient is calm and cooperative, sedative premedication is not necessary (19). However, small doses of a benzodiazepine may be beneficial for those treated chronically with benzodia- zepines, or if heightened anxiety about the anticipated surgery contributes to dyspnea. Careful titration is necessary; an overly large dose of a sedative/hypnotic agent may delay extubation at the conclusion of surgery. The addition of a small amount of opioid has also been advocated as a premedication (20). On arrival in the operating room, noninvasive monitoring of blood pressure and temperature, electrocardiogram, pulse oxi- metry, and capnography are initiated. A large-bore intravenous line is established and premedications administered. If a neu- raxial procedure is planned, the patient is positioned, and the procedure is initiated at this juncture. Some authors advocate that the placement of a thoracic epidural catheter be confirmed by fluoroscopy or a measure of clinical effect before the induc- tion of anesthesia (20, 21). An arterial line should be placed before induction; it is mandatory for beat-by-beat hemodynamic monitoring and re- petitive blood gas sampling. In addition, administration of vaso- active agents may be necessary to counteract the sympathetic TABLE 1. PREDICTORS OF MORTALITY WITH LUNG VOLUME REDUCTION SURGERY Study Variable First Author (Ref. No.) Study Design (n) Comments Age Naunheim (32) Multicenter retrospective (682) 63.8 6 8.2 yr in survivors vs. 68.3 6 7.6 yr in nonsurvivors Glaspole (33) Single center, retrospective (89) Age . 70 yr; OR, 9.0 for perioperative mortality Male gender Naunheim (32) Multicenter, retrospective (682) 60% in survivors vs. 80% in nonsurvivors Ciccone (34) Single center, retrospective (250) Females had RR of 0.543 compared to males Exercise tolerance Szekely (5) Single center, retrospective (47) 6MWD , 200 m associated with death Naunheim (32) Multicenter, retrospective (682) 6MWD of 885 6 322 m in survivors vs. 740 6 415 m in nonsurvivors PaCO2 Szekely (5) Single center, retrospective (47) PaCO2 . 45 mm Hg associated with death O’Brien (9) Single center, prospective (46) No increased mortality with PaCO2 . 45 mm Hg Keenan (35) Single center, prospective (67) PaCO2 . 50 mm Hg associated with death FEV1 NETT (7) Multicenter, prospective (1,033) FEV1 ,20% combined with DLCO , 20% increased risk of death Ciccone (34) Single center, retrospective (250) Low FEV1 increased risk of death DLCO Geddes (36) Single center, prospective (15) DLCO , 30% associated with increased risk of death Keenan (35) Single center, prospective (67) DLCO , 25% associated with serious postoperative risk NETT (7) Multicenter, prospective (1,033) DLCO , 20% combined with FEV1 , 20% increased risk of death Imaging studies Naunheim (6) Multicenter, prospective (511) Non–upper lobe–predominant emphysema RR, 2.99 for operative mortality (after high-risk patients excluded) Wisser (37) Single center, retrospective (47) Severity of emphysema correlated with mortality NETT (7) Multicenter, prospective (1,033) Diffuse emphysema combined with FEV1 , 20% increased risk of death Definition of abbreviations: DLCO 5 diffusing capacity of carbon monoxide; NETT 5 National Emphysema Treatment Trial; OR 5 odds ratio; RR 5 relative risk; 6MWD 5 six-minute-walk distance. Adapted by permission from Reference 6. Brister, Barnette, Kim, et al.: Anesthesia for LVRS Patients 433
  3. 3. blockade commonly seen with the administration of local anesthetics via a thoracic epidural catheter. An arterial moni- toring line will allow rapid titration of these agents. Central venous catheters may be employed (19, 21), and are useful for rapid delivery of pharmacologic agents to the central circulation, but are not absolutely necessary. Placement of a central catheter is usually performed after induction of anes- thesia due to the discomfort that the patient may experience in the Trendelenberg position and the possibility of oxygen desaturation. Buettner and colleagues (22) reported on the use of pulmo- nary artery (PA) catheters in 55 patients, and found no evidence that PA catheter use improved care; therefore, they no longer use catheters routinely. Triantafillou (20) reported no benefit from the use of PA catheters and/or transesophageal echocar- diography (TEE) selectively in patients with underlying cardiac disease or pulmonary hypertension. Jo¨rgensen and colleagues (23) compared PA data and TEE data obtained from patients undergoing LVRS and lobectomy without severe COPD. PA data suggested poorer left ventric- ular (LV) function (lower stroke volume index, stroke work index, cardiac index) in the patients undergoing LVRS than in the lobectomy group at baseline and improved LV performance in patients (improved stroke volume index, stroke work index, cardiac index and LV filling) after LVRS. They concluded that the results ‘‘could be tentatively explained by an alleviation of intrinsic PEEP [positive end-expiratory pressure], with a con- sequent increase in intrapulmonary and intracardiac blood volume.’’ Mineo and colleagues (24) showed right ventricular end-diastolic volume increased after LVRS. These studies lend support for the value of the LVRS procedure, as it improves cardiopulmonary physiology, but do not support the routine use of PA catheters or TEE. Although use of a PA catheter or TEE in patients with a history of significant cardiac disease, ventricular dysfunction, or pulmonary hypertension is commonly recommended, there is little evidence that their use improves outcomes. Falsely ele- vated intrathoracic venous pressure may occur secondary to intrinsic PEEP (25). Repositioning of the patient after placement of the flow-directed PA catheter may contribute to inaccurate measurement of cardiac filling pressures. If more definitive intra- operative assessment of right or left heart function is required, the TEE will likely provide greater value (13, 19). The possibility of intraoperative awareness is real. These patients receive little or no amnestic agents, are administered neuromuscular blocking agents, and, due to the concerns re- garding hypotension, may receive insufficient anesthesia to pre- vent awareness. For all of these reasons, some type of brain function monitoring during surgery should be considered. Before induction of anesthesia, the patient is preoxygenated; this may be done with the patient in a partial sitting position if the supine position provokes severe dyspnea. A longer-than- normal period of preoxygenation may be required due to air trapping from severe lung disease. Propofol, sodium pentothal, and etomidate have all been used for induction (20). Upon loss of consciousness, the patient is placed supine to facilitate airway control. Multiple techniques and agents are available for induction and maintenance of anesthesia. Both total intravenous anesthe- sia (TIVA) and inhalational agents have been successfully used (21). Propofol is the most commonly used agent for TIVA, usually in combination with an opioid, such as remifentanil; the key consideration should be use of short-acting intravenous agents. Proponents of propofol note that hypoxic pulmonary vasoconstriction is preserved, thus avoiding an increase in oxy- gen shunt fraction. Although vecuronium bromide is the most common neuromuscular blocking agent used to facilitate in- tubation and intraoperative muscle relaxation, any intermediate muscle relaxant that is devoid of hemodynamic effects is accept- able. Monitoring the degree of neuromuscular blockade with a train-of-four twitch monitor is appropriate; for a variety of reasons, these patients may evidence increased sensitivity to neuromuscular blocking agent (26). A variety of inhalation agents have been used, but no agent has emerged as clearly superior. Use of nitrous oxide has been avoided in all published reports (19). Due to the severity of the bullous disease, and the associated large dead space, uptake and distribution of in- halational agents is unpredictable (19) and delayed awakening may be seen. Concern regarding the respiratory depressant effect of par- enteral narcotics in this population is valid, but should not preclude their use. Prophylactic administration of antiemetics should be considered. HYPOTENSION Hypotension may occur at any time during LVRS, but is most commonly seen upon induction of anesthesia. A common eti- ology is dynamic hyperinflation (air-trapping, auto-PEEP), which can occur with either hand ventilation or upon conversion to mechanical ventilation. This reflects not only the severity of the airway disease and its effect on venous return, but also a de- creased intravascular volume (25); disconnecting the ventilator circuit from the endotracheal tube leads to a rapid resolution of hypotension if this is the etiology. Other causes of hypoten- sion include the sympathetic blockade from a thoracic epidural catheter or the vasodilatory effects of induction agents. Myo- cardial ischemia must also be considered if the patient has significant coronary artery disease. Less likely, but still possible, are catastrophic occurrences, such as pneumothorax or anaphy- laxis secondary to induction agents, antibiotic administration, or latex sensitivity. Although treatment is possible with a vasoconstrictor (mixed b/a-agonist or a-agonist) or fluid administration, we believe that conservative fluid management supports the goal of early extubation. This philosophy of fluid management is based on patients after pneumonectomy developing pulmonary edema (rarely) and care of patients with acute lung injury; there are no comparative fluid management studies for patients undergoing LVRS. It should be noted that, later in the perioperative course, it is also important that fluid administration not be the primary therapy for treatment of sympathetic blockade secondary to administration of local anesthetics via a thoracic epidural catheter. Finally, temperature preservation is important, as hypother- mia may affect coagulation, lead to shivering and increased production of CO2, and delay extubation. Temperature preser- vation devices include, but are not limited to, lower body forced-air warmers, warmed intravenous fluids, heating pads, and heat–moisture exchangers. ISOLATION OF LUNG AND VENTILATION TECHNIQUE The surgical approaches to this operation include median ster- notomy, with the patient supine, or video-assisted thoracoscopy and/or thoracotomy, with the patient in the lateral decubitus position. OLV in the lateral position is associated with the greatest physiologic changes, and anesthetic management fol- lows the same principles used in other lung surgeries. Although most practitioners will achieve lung isolation for this procedure by placing a left double-lumen tube (21, 22, 25), bronchial 434 PROCEEDINGS OF THE AMERICAN THORACIC SOCIETY VOL 5 2008
  4. 4. blockers have also been used with success. The major disadvan- tage of the bronchial blocker is its small lumen, which will delay deflation of lung and limit suctioning of secretions from the operative lung. However, a bronchial blocker is more easily placed than a double-lumen tube in some patients. When using a bronchial blocker, it is commonly accepted practice to direct it into the left lung first; upon completion of the procedure on that lung, the bronchial blocker is then repositioned into the right main-stem bronchus. Regardless of which device is used, appro- priate positioning should be confirmed via fiberoptic bronchos- copy. If lung isolation is problematic and OLV cannot be initiated, successful surgical completion of LVRS may be accomplished using low tidal volume ventilation during surgical exposure, and apneic oxygenation during the stapling of the diseased lung section. Although technically more challenging for the surgeon, it has been well tolerated in the few patients for whom it was necessary. Intraoperative ventilatory management is directed toward producing adequate oxygenation with a low tidal volume tech- nique while maximizing exhalation time. This helps prevent dynamic hyperinflation and minimizes the likelihood of disrup- tion of suture lines or of the adjacent nonresected lung tissue. Both pressure-controlled and volume-controlled ventilation have been used to successfully achieve these goals. Sophisticated ven- tilators, with volume and pressure control settings, are now standard on most anesthesia machines; a ventilator capable of measuring auto-PEEP may also be useful. Pressure-controlled ventilation limits peak airway pressure and may help minimize the risk of barotrauma. With volume- controlled ventilation, air trapping can be minimized by using no more than moderate tidal volumes (,9 ml/kg for ventilation of both lungs; ,5ml/kg during OLV) (21), low respiratory rates, and inspiration:expiration ratios that range from 1:3 to 1:5. Hypercapnia is the most common result of the low tidal volume ventilation strategy; good communication with the surgeon and periodic evaluation of the PCO2 and pH is advised when using the low tidal volume strategy intraoperatively. Most patients tolerate elevated CO2 levels well during surgery; however, when pH falls below 7.2, maneuvers need to be instituted to increase minute ventilation (25). The first strategy would be to increase the rate of ventilation, while remaining mindful of the risk of increased auto-PEEP. Communication with the surgeon to anticipate time expectations is imperative. Although oxygena- tion is often easily maintained in this group of patients, a step- wise approach to any change in oxygen saturation is prudent. These steps would include assuring maximal inspired oxygen, removal of secretions, adequate muscle relaxation, and ag- gressive treatment of any bronchospasm. The use of PEEP in the dependent lung can also be used with caution. Insufflation of oxygen into the nondependent lung tends to obstruct the surgical field. Occasionally, the surgeon may need to tempo- rarily obstruct the PA flow to reduce the shunt and improve oxygenation. Many of the techniques and considerations related to lung isolation and OLV apply to this population of patients (27). However, several unique aspects of the patient undergoing LVRS are worth noting. Due to decreased elastic recoil, deflation of the operative lung is prolonged in this patient population. Suc- tioning is of little value in accelerating lung collapse (25), and it is common after opening the chest to note that the lung, al- though isolated from the ventilator circuit and open to the atmosphere, is still inflated. For that reason, our practice has been to proceed with OLV as early as possible, in consultation with the surgeon, to maximize the time available for lung deflation. Additionally, the diseased portions of the lung will deflate more slowly than the more normal parenchyma, and this may assist the surgeon in identifying which portions of the lung should be resected. Additional methods that may help deflate this lung include suctioning of secretions or gentle pressure exerted on the lung by the surgeon. It is not unusual for severely emphysematous lungs to never completely collapse during OLV. Resection of the most diseased lung first has been advised by some (28), and may allow for a smoother intraoperative course. After stapling, low tidal volume ventilation is reinstituted and the lung is inspected for air leaks. If additional surgical inter- vention is required, the same sequence may be repeated. PAIN CONTROL Post-sternotomy pain is usually tolerated better by patients than post-thoracotomy pain, but regardless of surgical approach, good pain control is a necessary component of the anesthetic plan for LVRS. Although the majority of published reports include thoracic epidural infusions as part of the pain manage- ment strategy, no approach is universally agreed upon, and most practitioners use a multimodality approach combining one or more regional techniques with parenteral agents. Thoracic epidural catheter infusion of local anesthetics with or without narcotics can provide patients with excellent pain control after surgery. Thoracic epidural analgesia is considered mandatory by some practitioners (19), and is the most com- monly recommended form of regional pain control for LVRS. Indeed, in some centers, if acceptable placement of a thoracic epidural catheter cannot be confirmed before induction of anes- thesia, the surgery will be postponed. The amount of narcotic administered with the local anesthetic varies in published reports (20, 22). Some practitioners infuse local anesthetic agents only, due to concern for the somnolence, hypopnea, nausea, and vomiting that may be seen with neuraxial opioids (22). It is important to note that the effect of thoracic epidural analgesia on patient outcome has not been definitively demonstrated, and other methods of achieving excellent pain control are viable. If the surgical approach is via median sternotomy and tho- racic epidural analgesia is used for pain relief, it is common for patients to have residual upper sternotomy pain (20). Dorje and colleagues (29) supplemented thoracic epidural analgesia by blocking the medial supraclavicular nerves of the cervical plexus bilaterally, just above the suprasternal notch. The authors re- port good results, while minimizing the risk of phrenic nerve(s) blockade; they acknowledge that additional investigation is needed. Liu and colleagues (28) administered diamorphine (bolus followed by a continuous infusion) alone via a lumbar epidural catheter to eight patients. Although pain relief was good, nal- oxone was administered after extubation to two patients to treat respiratory depression. We recently reported the use of intrathecal morphine for pain control in patients undergoing LVRS (30). Although a minority of patients had delayed extubation, pain control during the first postoperative day was superior compared with that achieved with morphine/ropivicaine administered via a thoracic epidural catheter. The amount of intravenous opioids adminis- tered was not statistically different on Postoperative Days 2 or 3 for patients receiving a thoracic epidural versus those receiving intrathecal morphine, indicating similar pain levels. Complica- tions were similar in both groups, as were outcomes. One advantage of intrathecal opioid therapy is the ease of perform- ing the procedure, which translates into a higher success rate. Thoracic epidural catheter placement is technically difficult, may not function as expected, and carries significant risk (22); further investigation is needed. Brister, Barnette, Kim, et al.: Anesthesia for LVRS Patients 435
  5. 5. Most anesthesiologists involved in the care of patients under- going LVRS will also routinely use parenteral nonsteroidal agents to supplement pain control. Buettner and colleagues (22) noted 93% use of nonsteroidal antiinflammatory drugs in patients postoperatively to supplement other analgesia. If an acute pain service is available, early involvement of this resource should be routine. Other techniques for pain relief include surgically sited pleural catheters, the ON-Q pain relief system, and patient- controlled analgesia. EXTUBATION AND TRANSFER TO THE INTENSIVE CARE UNIT Extubation at the conclusion of surgery is dependant on rever- sal of neuromuscular blockade, adequate pain control, and the absence of significant bronchospasm, secretions, hypercapnia, or acidosis. If the patient is somnolent and there is some question as to whether this is related to premedication with a benzodi- azepine, the use of a reversal agent (flumazenil) may be con- sidered. It is important to note that patients with hypercapnia may still be extubated if other criteria are acceptable. The patient is placed in a head-up position and, when the patient is conscious and ventilatory effort is acceptable, the endotracheal tube is removed. A humidified face mask is used to deliver oxygen, and the patient is transferred to the intensive care unit. Upon arrival in the intensive care unit, the patient continues to require close monitoring for postoperative respiratory dys- function, oversedation, and respiratory acidosis. Frequent or continual nebulization of bronchodilators is essential, and the patient is maintained in a head-up position. Our practice has been to place the chest tubes to water-seal rather than suction; however, low-level suction has also been reported (31). If serial blood gases reveal progressive hypercapnia, noninvasive ven- tilatory support may be used to stabilize gas exchange and de- crease the work of breathing while further investigation proceeds. CONCLUSIONS Good preoperative evaluation and anesthetic management are essential to a successful surgical outcome with LVRS. Although either a TIVA technique or a volatile anesthetic agent can be used, there must be complete reversal of anesthetic effect at the conclusion of surgery to allow extubation in the operating room. Postoperative pain management is multimodal; the goal is good pain relief and minimal effect on respiratory work. Positive-pressure ventilation contributes significantly to mor- bidity and mortality (22), and so the need to reintubate and institute positive-pressure ventilation may dramatically worsen outcome. Although the anesthetic management of the patient undergoing LVRS is fraught with potential problems, careful attention to detail can give patients—who would not have been operated on just a few short years ago—an opportunity for a new lease on life. Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. References 1. Smetana GW. Preoperative pulmonary evaluation. N Engl J Med 1999; 340:937–944. 2. Cooper JD, Trulock EEP, Triantafillou AN, Patterson GA, Pohl M, Deloney P, Sundaresan R, Roper C. Bilateral pneumectomy (volume reduction) for chronic obstructive pulmonary disease. J Thorac Cardiovasc Surg 1995;109:106–119. 3. Cooper JD, Patterson GA, Sundaresan RS, Trulock E, Yusen R, Pohl M, Lefrak S. Results of 150 conseccutive bilateral lung volume reduction procedures in patients with severe emphysema. J Thorac Cardiovasc Surg 1996;112:1319–1330. 4. 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