Chronic obstructive pulmonary disease (COPD) is a highly prevalent condition that has frequent morbidity and mortality (1). Medical treatment of COPD relies on the appropriate use of bronchodilators, steroids, antibiotics, and supplemental oxygen. However, in the later stages of the disease patients are severely dyspneic at rest despite maximal medical therapy.
A surgical approach to treatment of severe emphysema is now gaining in popularity. In the late 1950s Brantigan et al. (2,3) described a technique of non-anatomical resection of the lung aimed at reducing total lung volume, with the intention of permitting the chest wall to operate at a more normal physiological volume, thereby improving respiratory mechanics. However, their inability to demonstrate any objective improvement in their patients and the frequent mortality (18%) caused the procedure to be abandoned. In 1995 Cooper et al. (4) revived lung volume reduction surgery (LVRS) and were able to demonstrate an objective improvement in lung function after surgery. There were no deaths among the initial 20 patients at 6-month follow-up. LVRS is now practiced in specialist centers across the United States and Europe. It carries a 4%–5% 30-day mortality as well as significant morbidity (5). Clearly, thoracic surgery, be it via thoracotomy, sternotomy, or video-assisted thoracoscopic surgery, on patients with severe emphysema is a major undertaking with a significant risk of death and it sometimes involves a prolonged postoperative course in the survivors.
A lung volume reduction procedure via flexible bronchoscopy has been developed that may offer similar benefits to LVRS while avoiding much of the morbidity associated with major surgery in this group of patients. Our institution has recently published a preliminary series of bronchoscopic lung volume reduction (6), and this report provides a summary of the anesthetic experience in the patients undergoing this novel procedure.
The Royal Brompton Hospital ethics committee approved the trial and written consent was obtained from all patients. All the patients selected had severe emphysema, severe dyspnea, good target zones on computerized tomogram (CT), and were well motivated. Patients were excluded who had any of the following:
- Clinical evidence of cor pulmonale (defined as ankle edema, increased jugular venous pressure, and cardiomegaly on chest radiogram).
- More than four acute exacerbations per year.
- Evidence of active infection.
- Cardiac failure.
- Active treatment for terminal disease.
All of these conditions are relative or absolute contraindications for LVRS. Any other comorbid condition that was felt to increase the risk of the procedure also disqualified potential subjects from admission to the trial.
Preoperative assessment included the shuttle walking test (7), pulmonary function testing (including body plethysmography and carbon monoxide diffusing capacity), chest radiography, high resolution CT scanning, and ventilation/perfusion scintigraphy. Results are reported elsewhere (6).
All patients’ medical treatment had been optimized, and their regular medication was continued up until the time of the procedure. This medication included oral and inhaled bronchodilators and steroids. No sedative premedication was given, but the patients were given nebulized salbutamol approximately 30 min before the start of the procedure. Intraarterial blood pressure monitoring and large bore IV access were established under local anesthesia before induction of general anesthesia. A total IV anesthetic technique of target-controlled infusion propofol, supplemented by a remifentanil infusion, was used. For induction and intubation, a propofol target concentration of 4 μg/mL was used, with 0.5 μg · kg−1 · min−1 remifentanil. Neuromuscular blockade was achieved with vecuronium 10 mg at induction, with subsequent doses of 2–3 mg vecuronium as required. Endotracheal intubation was performed using a single-lumen 9 mm or 10 mm internal diameter endotracheal tube. Once the tube was passed, a propofol target concentration of 2 μg/mL, with 0.25 μg · kg−1 · min−1 remifentanil was used. During the procedure, infusion rates were titrated to the hemodynamic response and metaraminol 0.25 mg given as necessary to maintain the arterial blood pressure to within 20% of preinduction levels. Cefazolin 1 g was also given at induction.
Intermittent positive pressure ventilation was performed with a Draeger Evita 2 (Draeger, Luebeck, Germany). The objective of ventilation was to avoid dynamic hyperinflation; therefore, hypercapnia was accepted. To this end, intermittent positive pressure was limited to 20 mm Hg, with a rate of 10 breaths/min and a prolonged expiratory time (inspiratory:expiratory ratio, 1:3). An inspired oxygen of 50% was set and altered to maintain an arterial O2 saturation more than 95%. The procedure consisted of inserting two to five valves into the segmental bronchi of the more diseased upper lobe. The number of valves required was decided at the time of the procedure and was determined primarily by the relative sizes of the valves and the airways. If the segmental airways were large, the valves were placed more distally, requiring more valves. Most patients required three valves. Valves were positioned using a guidewire passed through a fiberoptic video-bronchoscope. Once placed, the one-way valves allow egress of air, without allowing any ingress of air, thus resulting in collapse of the target segment. The valves are illustrated in Figure 1. At the end of the procedure, residual neuromuscular blockade was antagonized by neostigmine and bradycardia prevented by glycopyrrolate, ventilation was changed to synchronous intermittent mandatory ventilation (maintaining the pressure limit and prolonged expiratory time), and propofol and remifentanil infusions were stopped. Tracheal extubation was performed in the operating room once the patient was awake and making a good ventilatory effort. In all cases this was within a few minutes of the end of the procedure. The patient was observed in the postoperative anesthesia recovery unit until judged ready, by standard criteria, to return to the respiratory high dependency unit, where invasive arterial blood pressure monitoring could be continued if required and there was a nurse: patient ratio of 1:1. In the postoperative period, salbutamol inhalers were given as required and oral codeine was used as an antitussive. Statistical testing was with nonparametric Wilcoxon’s matched pairs test and with Student’s t-test.
Results from the first seven patients to undergo bronchoscopic lung volume reduction are reported. One patient underwent a second procedure (on the contralateral side). All cases took place between April and December 2002, and the total follow-up time is now 2 yr. Preoperative pulmonary function tests are shown in Table 1.
During the procedure, all patients maintained arterial oxygen saturation more than 95% on Fio2 0.5. Paco2 increased during the procedure and was increased in the early postoperative period. However, by 2 h after the procedure it was returning to baseline level in all patients (Table 2). No clinical sequelae that could be attributed to hypercapnia were seen at any point during the procedure or in the early postoperative period. Between zero and six doses of metaraminol 0.25 mg (median, two doses) were required to maintain arterial blood pressure within 20% of preinduction levels. All patients could be discharged to the respiratory high dependency unit after their procedures, and no patient required subsequent admission to intensive care. There were no deaths. One patient developed a pneumothorax on the second day after the procedure and required a chest drain to be inserted, three patients developed acute exacerbations of COPD (defined by increased cough and sputum production but with no consolidation apparent on chest radiogram) that required treatment with a 7 to 10 day course of oral antibiotics and steroids, and one patient had a transient increase in cough that resolved spontaneously. All patients were discharged from hospital within 5 days, and in most cases this length of stay was only necessary to enable postprocedure tests to be done. Seven days after the procedure the median forced expiratory volume in 1 s had increased from 0.79 L (range, 0.61–1.07 L) to 1.06 L (range, 0.75–1.22 L), a difference of 34% (P = 0.028), and the median diffusing capacity (TLCO) increased from 3.05 mL · min−1 · mm Hg−1 (range, 2.35–4.71) to 3.92 mL · min−1 · mm Hg−1 (range, 2.89–5.40), a difference of 29% (P = 0.017). Figure 2 shows 3-D computed tomogram reconstructions of the chest of one patient before and after the procedure with the horizontal fissure highlighted. This demonstrates that the upper lobe has collapsed allowing the lower lobe to re-expand.
There is compelling evidence that for some patients, LVRS can result in improved lung function, exercise tolerance, and a better quality of life (8). The National Emphysema Treatment Trial (9) has confirmed that although LVRS does not offer any survival benefit over medical therapy, it does result in improved exercise capacity for at least 2 years. It also suggests that the patients who benefit most from LVRS are those with poor exercise capacity and predominantly upper lobe disease. Conversely, in those patients with non-upper lobe disease and a better exercise capacity, mortality is increased with surgical treatment without any outcome benefit when compared with medical therapy. The physiological improvement arises through three mechanisms:
- Re-expansion of less diseased areas of lung after resection of the most hyperexpanded areas.
- Improvement in diaphragm and chest wall mechanics resulting from redoming of the diaphragms and a decrease in hyperexpansion of the chest wall.
- Reduced tamponade of the right ventricle caused by hyperexpanded lung and increased intrathoracic pressure (10).
LVRS, however, does not alter the underlying disease process, and there is an inexorable decline in lung function after surgery, with a return to baseline usually seen in 18 months to 2 years. It has been suggested that performing a staged procedure will prolong this functional improvement, but this is a very serious undertaking for both patients and medical staff.
Bronchoscopic lung volume reduction aims to achieve the same physiological improvements as LVRS while avoiding the adverse consequences of major thoracic surgery in this high-risk group of patients. Furthermore, because of its relatively noninvasive nature, it is ideally suited as a staged procedure, potentially maximizing the benefit to the patient.
Two key considerations influenced the choice of anesthetic technique: avoidance of gas trapping during positive pressure ventilation and the need for optimum respiratory function in the immediate postoperative period. The concerns regarding gas trapping were because of the nature of emphysema, the severity of the patients’ lung disease, and the fact that the procedure involves a number of instruments being passed through the endotracheal tube, potentially further limiting expiratory gas flow.
A total IV technique offered a number of advantages over the use of inhaled anesthesia. It enabled the use of an unmodified Draeger Evita 2 ventilator, which was required to provide pressure-controlled ventilation with a prolonged expiratory phase. Furthermore, during the procedure, as a result of the amount of instrumentation to the airway, frequently there was a large gas leak; thus maintenance of anesthesia with volatile drugs would have been unreliable. There is evidence that propofol preserves hypoxic pulmonary vasoconstriction compared with the volatile anesthetics, which was also desirable in these patients (11).
Remifentanil significantly reduces the amount of anesthetic required to maintain anesthesia, and, because of its rapid metabolism by nonspecific blood and tissue esterases, it can be administered at large dosage without risk of accumulation and with minimal postoperative respiratory depression (12). These properties make it an ideal drug to facilitate the immediate return of optimal respiratory function after a procedure associated with minimal pain.
IV drugs do not depend on the damaged lungs for either uptake or elimination, thereby making the anesthetic course more predictable than would have been the case with inhaled anesthesia.
Although an initial dose of neuromuscular blocking drug was used at induction of anesthesia to facilitate tracheal intubation, the use of subsequent doses was avoided in the later cases to minimize the risk of residual neuromuscular blockade and re-paralysis with subsequent respiratory compromise. To facilitate this, a larger dose of remifentanil was used than would otherwise have been necessary, which at times required the use of vasopressors to support the systemic blood pressure. We considered that this was an acceptable compromise.
Postoperative analgesia is a major consideration with LVRS. Although some authors consider that thoracic epidural analgesia is the best option, there is no strong evidence to support this. What is clear, however, is that poor analgesia is a strong contributor to poor outcome. One of the great strengths of the bronchoscopic approach to achieving lung volume reduction is that it obviates this need for postoperative analgesia.
An increased Paco2 in the first 24 hours after LVRS is a ubiquitous finding, presumably related to postoperative pain, atelectasis, and the consequences of the operated lung or lungs having been collapsed for the duration of surgery (13–15). The bronchoscopic procedure only caused a modest increase in Paco2, and this was approaching preprocedure levels within 2 hours, reflecting a rapid return to more normal respiratory function because of the absence of the factors present after LVRS.
This novel approach to lung volume reduction shows very promising early results. We have demonstrated that using modern anesthetic techniques and drugs, which minimize intraoperative gas trapping and postoperative respiratory depression, patients with extremely poor lung function can safely be anesthetized and cared for through the perioperative period. If the early results are sustained, this procedure will supplant the surgical approach to lung volume reduction; the anesthetic problems associated with the surgical approach have recently been reviewed (16). In combination with appropriate regional analgesia, this technique could also be applied in cases of patients with severe respiratory disease having other surgical procedures.
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© 2004 International Anesthesia Research Society
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