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Ann Thorac Surg 2000;69:1711-1716
© 2000 The Society of Thoracic Surgeons
a Department of Respiratory Medicine, Alfred Hospital, Prahran, Australia
b Department of Thoracic Surgery, Alfred Hospital, Prahran, Australia
Address reprint requests to Dr Snell, Department of Respiratory Medicine, Alfred Hospital, Commercial Rd, Prahran, Australia, 3181
e-mail: greg.snell{at}med.monash.edu.au
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Abstract |
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Methods. We reviewed preoperative characteristics of the first 89 patients who underwent lung volume reduction surgery at the Alfred Hospital. Data included arterial blood gases, prednisolone use, pulmonary function tests, 6-minute walk test, and anesthetic time. Length of stay and reintubation for respiratory failure were used as markers of morbidity.
Results. Findings included PaCO2 of 43 ± 0.7 mm Hg, PaO2 70 ± 1.1 mm Hg, percent predicted values for forced expiratory volume in 1 second 29.6% ± 0.8%, TLCO% predicted 35.2 ± 1.4%, and 6-minute walk test of 315 ± 10.6 m (mean ± SEM). Mean length of stay was 19 ± 2 days, with 17 (19%) patients reintubated for respiratory failure. Mortality rate was 5.6% at 1 year post surgery, with no deaths in patients less than 65 years old. Multivariate analysis revealed that length of stay, reintubation and mortality were predicted by age and surgical time (p < 0.05), with no correlation with any other variables tested. Age greater than 70 years was associated with a significant risk of mortality (OR 9.0; p = 0.04).
Conclusions. Age greater than 70 years and anesthetic time greater than 210 minutes predict both perioperative morbidity and mortality.
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Introduction |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Standard therapy over several decades has included the use of inhaled bronchodilator therapy, theophylline, and corticosteroids where a reversible component of obstruction exists. Although pulmonary rehabilitation has been shown to lead to symptomatic improvement, the only therapy proven to prolong life thus far has been long-term oxygen therapy [3]. Up until 1995, surgical therapy had been limited to reduction pneumoplasty of large bullae and lung transplantation. At this time Cooper and colleagues [4] created a surge of interest in lung volume reduction surgery (LVRS) with the results of their first series of 20 patients. Within that group, and then subsequently in an expanded series of 150 patients [5], Cooper and colleagues showed that remarkable improvements in both physiological and symptomatic parameters could be achieved in carefully selected severely emphysematous patients.
Although other groups around the world have been able to produce sustained improvements similar to the results of Cooper and coworkers [6], LVRS has not yet achieved general acceptance because of its as yet unproven cost-benefit ratio. Although this is in part due to a lack of long-term follow-up data available on recipients, it also relates to the fact that comment on functional outcome is premature while the best selection criteria, surgical technique, and postoperative care are still being refined.
Initial selection criteria at our institution were based on those suggested by Cooper and coworkers, and aimed to include those patients with severe emphysema who most clearly had anatomically accessible areas of relatively functionless lung, while excluding those patients that were likely to be at significant operative risk. Specific risk factors that were believed likely to be important encompassed those general factors suggested by Goldman and associates [7] and the American Society of Anesthesiologists, as well as particular pulmonary risk factors such as significant hypoxia, hypercapnia, or pulmonary hypertension [8].
Subsequent work has shown that unacceptable postoperative outcomes in LVRS are associated with a 6-minute walk test distance of less than 200 m, or a resting room air PaCO2 greater than 45 mm Hg [9], whereas death is associated with increased age, higher PaCO2 values, and lower trapped gas values [10]. More recent work associates prior myocardial infarction, male gender, chronic steroid use, and median sternotomy incision with early mortality [11], whereas a higher forced expiratory ratio or diffusion capacity has a protective effect [12].
Many of these parameters were considered in the drafting of our institution’s selection criteria (see Table 1) [13]. To aid the further refinement of selection criteria, we evaluated preoperative and operative predictors of morbidity and mortality in the first 89 patients undergoing LVRS within the Alfred Hospital.
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Material and methods |
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Preoperative assessment and operative technique
Prospective patients undergo a detailed preoperative assessment during which significant comorbidity is excluded (see Table 2). Suitable target areas for resection are identified, being those that represent upper lobe emphysema on computed tomography, as well as being functionally useless on the basis of perfusion scanning [13]. All patients are required to undergo a pulmonary rehabilitation program with the aim of achieving a 60% to 80% maximum predicted heart rate for a duration of 30 minutes during aerobic exercise on a treadmill or exercise bike. Surgery is carried out electively and scheduled to coincide with optimization of performance. The operative technique used at our institution is that described by Cooper and colleagues [3] through a median sternotomy with simultaneous resection of half of both upper lobes of the lung, and closure of the pleura using a linear stapler with bovine pericardium. After the procedure, anesthesia is reversed and the patient extubated as soon as possible, generally within the first hours of the postoperative period. Patients are cared for on a cardiothoracic intensive care unit on the first day postprocedure, then transferred to a specialist respiratory ward until discharge [14].
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Date of procedure was recorded and used to assess the effect of learning curve. The duration of the patient’s operation was obtained from the patient’s anesthetic record and represented time spent immediately preoperatively undergoing induction and intravenous catheterisation, the operation itself, and postoperative reversal of anesthesia.
Measures of morbidity included patients’ length of hospital stay and whether they were reintubated for respiratory failure. Patients reintubated for surgery to oversew persistent air leaks were not included in the reintubation group. Deaths in the same admissions as those during which surgery was performed were defined to represent perioperative mortality.
Statistical analysis
Data was expressed as mean (± SEM) unless otherwise indicated. Comparisons between groups were made using a Mann-Whitney test for nonparametric continuous data and Fischer’s exact test for categorical data. Correction for multiple testing (Bonferroni) was made. To determine parameters that predicted outcome, univariate linear regression analysis was used, with length of hospital stay as the dependent variable, and logistic regression was used with reintubation and perioperative mortality as the dependent variables. Perioperative mortality was defined as mortality occurring at the same admission as that at which the procedure occurred, or within 30 days of the procedure being performed. Potentially significant parameters were then tested for possible interrelationships by multivariate regression analysis, which also included the noncontinuous variables gender, use of oral glucocorticoids at the time of surgery, and inclusion within the first 45 operations (as opposed to the subsequent 44). All statistical analysis was performed with the SPSS software package (SPSS, Chicago, IL).
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Results |
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Patient characteristics
A total of 35 men and 54 women underwent lung volume reduction surgery between September 1995 and August 1998. The mean age was 62.3 ± 0.1 years. In all, 37 patients were using oral glucocorticoids at the time of their operation, all less than 10 mg prednisolone daily. Preoperative data is displayed in Table 3. Twenty-five patients (29%) had a preoperative PaCO2 greater than 45 mm Hg, whereas 19 patients (22%) had a preoperative PaCO2 less than 60 mm Hg on room air. 6MWT data revealed severe reduction in exercise capacity, with 13 patients (15%) achieving a best distance of less than 200 m. Spirometry revealed all patients to have severe obstructive deficits, with 12 patients (13%) having an FEV1 of less than 500 mL, and 11 patients (12%) having an FEV1%pred less than 20%, whereas 30 patients (36%) had a TLCO%pred less than 30%. Anesthetic time showed considerable variation in its duration, and this did not alter with respect to increasing staff experience. The mean anesthetic time was 194 (±9) minutes, with a range of 60 to 620 minutes. Functional outcome for our cohort compares favorably with data published by other groups. In our earlier series, mean MRC score increased from 2.1 to 3.4, mean FEV1 from 0.72 L to 1.07 L, and mean 6MWT from 306 m to 431 m [13].
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Perioperative mortality occurred in 5 patients (5.6%), all more than 65 years of age (see Table 4). No significant change in rate of perioperative morbidity or mortality occurred as experience increased. Two later deaths occurred, one due to primary lung cancer, the other vascular disease. We separately analyzed actuarial survival using survival analysis techniques and found this to be 95.5% at 1 month, 93.3% at 1 year, and 92.1% at 2 years (see Fig 1). These figures compare favorably with LVRS survival data presented by other groups [11, 15].
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With regard to mortality, when logistical regression analysis was applied, age and anesthetic time were again found to have statistically significant associations, with regression coefficients of 0.28 (p = 0.01) and 0.22 (p = 0.04), respectively. No association was found between either of the above markers of morbidity or mortality, and gender, case number, oral glucocorticoid use, preoperative 6MWT, arterial blood gas measurements, or pulmonary function test parameters.
Odds ratios
Based on the results from univariate regression analysis of our patients and factors previously shown to predict morbidity and mortality [9–11] we examined whether certain patient characteristics were associated with an increased risk of poor outcome (Table 5). We examined the risk of mortality, reintubation, and hospital stay as well as a total risk of any of these using combined "poor outcome," a concept based on the work of Szekely and colleagues [9]. We found that although there was a significant risk for patients more than 65 years old, this was especially highlighted in the group more than 70 years old. A prolonged anesthetic time (>210 minutes) was also a risk factor for poor outcome in all parameters measured. A 6MWT less than 200 m was associated with a higher risk of intubation, but this just failed to reach statistical significance. No other single factor was associated with the development of poor outcome.
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Previous studies of the LVRS population have also suggested that age is a risk factor for unacceptable outcome, and indeed that age greater than 75 years is a relative contraindication to lung volume reduction surgery [10]. Within our study population, no deaths occurred in the group aged 65 years and less (55 of 89 patients) either perioperatively or at 1 year. However, in the group more than 65 years old mortality was 15% (5 of 34 patients), and in the group more than 70 years old mortality was 20% (3 of 15 patients). Similar results were apparent for morbidity with respect to age, with 35% of patients more than 65 years old and 47% of patients more than 70 years old being reintubated, whereas only 9% of patients 65 years or less required reintubation. On the basis of this, it seems that caution is required in the application of this procedure to older age groups.
On the other hand, these findings suggest that lung volume reduction surgery is a relatively safe procedure in the group less than 65 years of age. This is a particularly important finding when one considers that its potential alternative, lung transplantation, has a reported 1-year mortality rate of approximately 22% for emphysema and a proportionately high morbidity [16].
Increased anesthetic time was significantly associated with both markers of morbidity as well as mortality, and could not be predicted by the other preoperative variables assessed in this study. It is possible that prolonged anesthetic time places the patient at greater metabolic demand, and thus less capable of adequate ventilation and sputum clearance, in the early hours postprocedure when this is most important.
Although increased anesthetic time may not appear to be a variable selectable at preoperative evaluation, there seem to be a number of avenues available to pursue this. The most obvious way is to avoid performing combined procedures such as coronary artery bypass grafting plus LVRS, as this has already been shown to increase the risk of postoperative respiratory failure [17]. An extended anesthetic time may be a surrogate marker of surgically difficult lung disease. Our surgeons report that one of the major causes of prolonged surgery is the repair of air leaks within more severely emphysematous areas on reinflation of the lung, although division of adhesions is also an important cause. The former of these two findings would seem to indicate that increased tissue friability was a risk factor for prolonged procedures, which coincides with the finding that severity of tissue destruction on computed tomography strongly predicts 30-day mortality [18]. An analysis comparing surgical time with the severity of parenchymal destruction on computed tomography is now required. Finally, it is relevant to assess whether alterations in surgical or anesthetic technique can remove this factor as a cause of unacceptable outcome.
As summarized in Table 4, all perioperative deaths occurred in relation to an episode of sepsis that was predominantly due to methicillin-resistant staphylococcus aureus. In a general sense, postoperative sepsis has previously been shown to correlate with surgical time and physical status [19]. As preoperative screening removes most candidates with other significant comorbidities, and all have roughly equivalently severe lung disease, age is likely to represent one of the few variables that affects differences in our patients’ general physical status.
Our study failed to confirm the increased morbidity and mortality demonstrated for variables such as resting PaCO2 greater than 45 mm Hg and 6MWT greater than 200 m noted by previous authors [9]. Although this may be seen as contradictory, we do not believe this to be the case. Our experience has occurred on the back of the early published reports relating to the successes and problems associated with LVRS [4–6]. On the basis of these reports, conservative selection criteria were established at our institution, although patients perceived to be at increased risk for complications on the basis of not meeting single parameters such as raised PaCO2 were still considered for LVRS, provided that these patients were excellent candidates in other physiological measurements. This may have led to single risk factors having less effect. Alternatively, as only small numbers had these characteristics, the study may have been underpowered to detect effect.
A striking feature of lung volume reduction surgery is the challenge it poses to previously established predictors of morbidity and mortality in thoracic surgery. Although most patients within our study population had features on pulmonary function testing that have previously been associated with poor outcome after thoracic surgery [8], no correlation could be found between worsening FEV1, or TLCO, as well as with 6MWT, PaO2, or PaCO2 and operative morbidity or mortality. Other authors have used combined values to establish predictors of mortality. Pierce and coworkers [20] used a predicted postoperative product of FEV1%pred and TLCO%pred in patients undergoing thoracotomy for lung cancer. In their study, seven of eight deaths occurred in patients with a postoperative value of less than 1850. Within our study population 80 of 87 patients had a value below less than 1850 before surgery, and no correlation could be obtained for morbidity or mortality. This supports the notion that traditionally held preoperative risk factors are less relevant in LVRS. It may also suggest that with the increased sophistication of thoracic surgical preoperative assessment and technique that has occurred with the advent of LVRS, the applicability of these risk factors to other thoracic procedures needs to be reassessed.
In summary, our study demonstrates that patients of older age or who have a prolonged anesthetic time are at an increased risk for both perioperative morbidity and mortality. We believe that patients of advanced age should be scrutinized very carefully before being accepted for LVRS and should be counseled regarding their greater chance of unfavorable outcome from LVRS. Methods of predicting prolonged anesthetic time at preoperative evaluation, as well as operative and anesthetic mechanisms to reduce its duration, need to be evaluated so that this risk factor can be minimized.
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