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Ann Thorac Surg 2007;83:S870-S876
© 2007 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, New York, New York
b Department of Anesthesiology, Mount Sinai School of Medicine, New York, New York
c Department of Cardiothoracic Surgery, Montefiore Medical Center, New York, New York
* Address correspondence to Dr Etz, Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029. (Email: christian.etz{at}mountsinai.org).
Presented at Aortic Surgery Symposium X, New York, NY, April 27–28, 2006.
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Abstract |
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METHODS: Two hundred nineteen patients (median age, 66 years; range, 18 to 88; 112 male) underwent DTA (n = 79 [36%; 23 elephant trunk completions]) or TAAA (n = 140 [64%; Crawford I (52%), II (10%), III (11%), IV (7%); 31 elephant trunk completions]) between June 2002 and June 2005. Forty-one patients presented with ruptured aneurysms. Left atrial-to-femoral bypass was utilized in 51% of the patients. Femorofemoral bypass and distal aortic perfusion were used in 41% of the patients, deep hypothermic circulatory arrest (DHCA) was used in 43 patients (mean duration: 31 ± 9 minutes); 8% were done with clamp-and-sew technique.
RESULTS: Adverse outcomes were seen in 21 patients (9.5%); hospital death in 13 (5.9%), and stroke in 13 (5 of whom died; 5.9%). Sixty patients (27%) experienced respiratory complications with prolonged postoperative ventilation (longer than 48 hours); 24 required tracheostomy (11%). Independent predictors of pulmonary complications after DTA/TAAA were TAAA (p = 0.03), preoperative blood urea nitrogen greater than 24 mg/dL (p = 0.03) and rupture (p = 0.09). The median hospital stay was 11 days (interquartile range, 6 to 35). Independent predictors of length of hospital stay were preoperative blood urea nitrogen (p = 0.045), postoperative bleeding (p < 0.005), reintubation (p = 0.001), tracheostomy (p < 0.0005), and transfusion of platelets (p = 0.008).
CONCLUSIONS: This contemporary experience demonstrates that preoperative renal insufficiency and extensive aneurysm are important predictors of respiratory complications after aortic aneurysm surgery.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Spinal cord ischemic complications after extensive aortic surgery have been the focus of research of aortic surgeons over the past 20 years, and the incidence of paraparesis and paraplegia have decreased significantly. Although neurologic complications have the most dramatic impact on post-operative outcome [8–11], renal, pulmonary, visceral and cardiac complications have an important influence on mortality and postoperative recovery [12, 13].
In most series of TAAA and DTA repairs, the most common postoperative complications are respiratory [1–4, 14]. The aim of this study was to examine the incidence of pulmonary complications in a contemporary series of 219 patients who underwent DTA and TAAA repair in two high-volume centers. An extensive analysis of preoperative, intraoperative, and postoperative predictors associated with pulmonary complications was also undertaken.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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The mean age of the patients was 63.8 years (range, 18 to 88). There were 112 males and 107 females. Preoperative risk factors considered included a history of hypertension in 212 patients (97%); a history of smoking in 110 patients (50%), with chronic obstructive pulmonary disease (COPD) in 53 (24%); a history of cerebrovascular accident in 34 patients (16%); chronic renal insufficiency in 27 patients (12%), with preoperative need for hemodialysis in 8 (4%), and insulin-dependent diabetes mellitus in 24 patients (11%). In all, 144 patients (66%) underwent elective operation owing to enlargement of their known aneurysm; 34 patients (16%) had urgent operations; and 41 patients (19%) underwent emergent repairs owing to ruptured aneurysms.
The patients in the two centers differed somewhat, and therefore statistical analyses were stratified by center. As seen in Table 1, the patients at Montefiore had higher rates of several comorbid conditions, perhaps reflecting poorer overall preoperative health status or differences in record keeping. Notably, there was a higher proportion of patients with rupture, of former and current smokers, and a higher rate of renal failure. Perhaps because Mount Sinai has a longer tradition as an aneurysm referral center, there were more chronic dissections. The patients were combined for multivariate analysis, stratifying for institution.
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Operative Management
All patients were placed in the standard thoracoabdominal position. A double-lumen endotracheal tube was used to isolate the left lung. A right radial arterial line, a right common femoral line, and a pulmonary artery catheter were inserted. Intraoperative transesophageal echocardiography was used in all patients. A spinal catheter was placed, and cerebrospinal fluid (CSF) pressure was monitored during the operation and for the subsequent 72 hours: the CSF was drained at a maximum rate of 15 cc/h as long as CSF pressure remained above 10 mm Hg. Somatosensory evoked potential and motor-evoked potential monitoring was utilized intraoperatively, and somatosensory evoked potentials for the first 12 hours postoperatively, in 100 patients [8].
As detailed in Table 2, left atrial-to-femoral bypass was used in 112 patients (51%). Partial femorofemoral bypass with an in-line oxygenator and distal aortic perfusion were used in 90 patients (41%). In 17 patients (8%), the clamp-and-sew technique was utilized. In 41 patients, full cardiopulmonary bypass and deep hypothermic circulatory arrest were required because placement of the proximal clamp was deemed impossible. The mean total deep hypothermic circulatory arrest time was 31 ± 9 minutes.
Operative Technique
The essential steps of our approach to the repair of DTA and TAAA have previously been described. The aorta is accessed through a left thoracotomy or thoracoabdominal incision. The diaphragm is divided circumferentially. The infradiaphragmatic aorta is exposed through a retroperitoneal approach. All operations are carried out under moderate hypothermia (32°C). If needed, deep hypothermia is utilized, with circulatory arrest initiated at a bladder temperature of 15°C and jugular bulb cerebral venous saturation 95% or greater.
Postoperative Management
In both institutions, aggressive fluid administration for at least the first 24 postoperative hours is initiated, aiming for a mean aortic pressure of 80 to 90 mm Hg, with peripheral vasoconstrictors given as necessary to maintain this pressure. Gentle diuresis is initiated 48 to 72 hours after the operation.
Somatosensory evoked potential, when utilized, are monitored until the patient awakens. Thereafter, hourly brief neurologic examinations are performed for 72 hours. Cerebrospinal fluid drainage is continued for 72 hours (target pressure < 10 mm Hg). Steroids are tapered over 48 to 72 hours.
Every effort is made to extubate the patients by the second postoperative day. Tracheostomy is usually performed within 5 to 7 days after the operation if the patient has significant pulmonary problems. Chest drains are removed sequentially as the output is 150 cc or less in 24 hours. Chest physiotherapy and nebulizer treatments are routine in the postoperative protocol. In both institutions, the transfusion of blood products was accomplished according to a similar protocol. Cell-saving device blood was used only intraoperatively.
Statistical Methods
Data were entered into independently maintained databases at Mount Sinai Medical Center and Montefiore Medical Center and transferred to a SAS (SAS Institute, Cary, North Carolina) file. Characteristics are described as percentages or as means and standard deviations or medians and interquartile range. Data were stratified by institution. Chi-square tests were used to identify individual factors associated with the various outcomes. Independent factors were identified by logistic regression. For pulmonary failure, logistic regression was first applied to preoperative factors. After significant or near-significant independent preoperative factors were identified, they were retained in the model, and stepwise logistic regression analysis was applied to identify significant perioperative factors while controlling for the previously selected preoperative factors.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Postoperative Complications
As detailed in Table 3, postoperative paraplegia occurred in 4 patients (1.8%). The most common cardiac complication was atrial fibrillation, which occurred in 62 patients (28%); 5 patients (2%) had myocardial infarction. Thirteen patients (5.9%) suffered a postoperative stroke, 5 of whom died. Eight patients had renal failure requiring postoperative dialysis (3.7%). Seventeen patients (8%) required reoperation for bleeding.
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Potential risk factors for pulmonary failure after DTA and TAAA repair are shown in Table 4, stratified by institution. Factors tested were selected with regard to their potential relevance for pulmonary failure: they include age; sex; extent of aneurysm (DTA, TAAA); preoperative pulmonary function (forced expiratory volume in 1 second [FEV1], forced vital capacity [FVC], FEV1/FVC); comorbidity (eg, COPD, preoperative renal failure); operative parameters (eg, operative technique, transfusions), and bypass details (CPB time, aortic cross-clamp time, deep hypothermic circulatory arrest); postoperative complications (other than pulmonary, eg, renal insufficiency, bleeding, wound infection), and preoperative, intraoperative, and postoperative blood values (eg, creatinine, blood urea nitrogen [BUN], lactic dehydrogenase [LDH], pH). Diabetes mellitus could not be used for this analysis as there were different definitions in the two institutions.
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When one considers the various components of our criteria for pulmonary failure—prolonged ventilation, reintubation, and tracheostomy—separately, a history of COPD, creatinine greater than 2.5 mg/dL either preoperatively or postoperatively, and transfusions of various allogeneic blood products were all associated with one or more manifestations of pulmonary failure on univariate analysis.
Intraoperative Transfusion of Blood Products
Data on perioperative transfusion of allogeneic blood products and autotransfusions (cell-saving device) were analyzed. There were statistical associations between administration of allogeneic blood products and pulmonary complications, as well as a marked association of allogeneic transfusions with extended hospital stay. Twenty-five patients (11.4%) did not receive any allogeneic blood products perioperatively, 12 of whom received autotransfusion of 250 to 1,000 mL. There was no association of cell-saving device use with pulmonary complications or mortality.
Hospital Stay
The median hospital stay was 11 days (range, 5 to 127). There were no preoperative univariate predictors of prolonged hospital stay. Postoperative risk factors for prolonged hospital stay were need for ventilatory support for longer than 48 hours (p < 0.0005); pneumonia (p = 0.003); tracheostomy (p < 0.0005); reintubation (p = 0.001); CPB duration (p = 0.0004); postoperative bleeding (p = 0.05); postoperative creatinine greater than 2.5 mg/dL, and also transfusion of platelets (p < 0.0005) and fresh-frozen plasma (p = 0.005).
Independent factors associated with prolonged hospital stay were preoperative BUN (p = 0.045), postoperative bleeding (p < 0.0005), reintubation (p = 0.001), tracheostomy (p < 0.0005), and transfusion of platelets (p = 0.008).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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A number of entities have been considered respiratory dysfunction, but prolonged ventilatory support, reintubation, and requirement for a tracheostomy are the ones that have a serious impact on hospital mortality and long-term functional outcomes [14–16]. Patients with DTAs and TAAAs are a population at high risk for pulmonary dysfunction after aneurysm repair because of age, and a high prevalence of cardiovascular disease, of COPD, and protracted smoking history [16]. Our current findings are in accord with these observations.
In addition, large thoracoabdominal incisions are associated with significant pain, and may have a negative impact on postoperative pulmonary function. Division of the diaphragm has been associated with a higher probability of prolonged ventilatory support, independent of known pulmonary risk factors, and preservation of the diaphragm was associated with a significant decrease—by an average of 4 days—in hospital stay in a report by Huynh and colleagues [17]. Our data indicate that patients with the most extensive aneurysms had the greatest likelihood of respiratory complications. Consequently, if it is technically feasible an attempt should be made to minimize the extent of the incision on the diaphragm by incising only its muscular portion and leaving the trefoil-shaped central tendon intact, particularly in patients with significant underlying pulmonary disease [17].
In our study, the need for prolonged respirator therapy was clearly associated with a higher mortality rate. Of the 60 patients (27%) who required ventilatory support for more than 48 hours, 7 (12%) died, whereas of the 159 patients (73%) who were extubated within 2 days after the operation, only 5 (3%) died. We believe that with modern techniques of anesthesia, intensive care unit management, and pain control, extubation should be feasible by the second postoperative day in the majority of patients [18]. That enables initiation of early pulmonary physiotherapy and should lead to a significant decrease in ventilator-related pneumonia. In our study population, the diagnosis of pneumonia was made in 30 patients (14%) either because of new infiltrates on chest radiograph or positive sputum microbiology: 50% of the patients who required reintubation had pneumonia. Of the patients with pneumonia, 23 patients (76%) required prolonged ventilatory support, and 15 patients (50%) required reintubation. Interestingly, none of the patients who required reintubation because of pneumonia died, suggesting that aggressive intervention for respiratory infections may be effective.
The need for tracheostomy is the benchmark of respiratory failure. Tracheostomy after TAA/A repair occurs in 4% to 9% [19] of the patients and has been reported to be associated with a high mortality rate. In a series of 1,414 patients reported by Svensson and associates [15] and Money and coworkers [20], 112 (8%) had pulmonary complications requiring tracheostomy, and 45 (40%) died in the hospital. In our series, the tracheostomy rate was slightly higher (11%), but associated with only 4% hospital mortality. Extensive TAAA, presence of COPD, pneumonia, renal insufficiency and transfusion of red blood cells and platelets were found by univariate analysis to correlate with the need for tracheostomy. Both univariate and multivariate analysis, however, failed to reveal a correlation between the need for tracheostomy and mortality in our series. This finding may be explained by our policy of carrying out tracheostomy early in patients with significant pulmonary problems, in an effort to improve pulmonary care and hasten their mobilization and physical therapy.
In our series, a history of COPD was one of the significant predictors of pulmonary failure. This is in agreement with a previous prospective study of 98 patients who underwent repair of thoracoabdominal aortic aneurysms[15]. However, there is more than the occasional patient in both studies—as well as in other series of TAAA repair—with a history of COPD and smoking, and therefore identification of those who will do poorly after operation can be difficult. In this series, although a higher incidence of respiratory complications was seen in the group of patients from Montefiore—among whom were a higher proportion of current and former smokers—smoking history did not distinguish between those with and without subsequent pulmonary complications. Rather surprisingly, the most powerful predictor of respiratory complications—apart from extent of aneurysm—was the presence of preoperative renal dysfunction.
Preoperative pulmonary function tests have been utilized to try to identify the patients at greatest risk for pulmonary complications; FEV1 and FVC have a linear relationship with postoperative respiratory complications, but as yet it has been difficult to identify a value below which the operation has a prohibitive pulmonary risk. In Svensson’s study, a forced expiratory volume (FEV25) was the only independent predictor of respiratory failure in patients with chronic pulmonary disease [15]. In our study, pulmonary function tests were performed in only 23 high-risk patients, 3 of whom subsequently required tracheostomy, but none of the preoperative screening tests had a significant predictive value. Nonetheless, if COPD is present preoperatively, spirometric tests and arterial blood gas analysis should be performed. Careful patient selection and preoperative optimization of pulmonary function in patients with COPD may decrease the incidence of serious respiratory complications.
During DTA and TAAA repair, large volumes of fluid are routinely administered during the operation and for the first 12 hours after surgery to compensate for the significant losses that occur perioperatively. Maintaining an adequate preload is important to prevent hypotension and avert possible spinal cord ischemia. Consequently, we agree with Svensson and associates that inducing vigorous diuresis to achieve early extubation should be avoided to prevent the precipitation of delayed paraparesis or paraplegia.
It is notable that current techniques can reduce the paraplegia rate below the stroke rate. In general, we will start gentle diuresis after the second postoperative day, when the inflammatory response to the operation and the significant associated capillary leak have subsided.
Impaired kidney function clearly reduces the ability to cope with excessive intraoperative and postoperative fluid administration. That may explain why the preoperative presence of renal insufficiency—reflected by elevated BUN or creatinine—significantly raised the risk of postoperative pulmonary failure in our series. Among the 60 patients with postoperative pulmonary failure, 28 (47%) also suffered from renal failure, and 7 died in the hospital. Previous studies have shown an increased risk of prolonged ventilation if postoperative renal complications are present: renal failure may be associated with multiple other problems which contribute to the need for prolonged intubation, which then poses a risk for ventilator-associated pulmonary infections. In addition, the treatment of postoperative pulmonary failure requires strategies opposite to those for prevention of renal failure. Prevention of renal failure often involves administration of large volumes to achieve sufficient renal preload, raising the risk of respiratory insufficiency due to volume overload. The role of preoperative renal insufficiency in predicting postoperative pulmonary failure in this study underscores the importance of carefully balanced postoperative fluid management. In patients with impaired renal function, use of short-term vasoconstrictors to maintain high normal blood pressure, in combination with more restrained fluid administration, may improve postoperative pulmonary outcome.
In our study, the use of homologous blood and blood products was associated with a higher incidence of postoperative respiratory dysfunction. In contrast, use of cell-saving device blood had no adverse impact on pulmonary function. These findings are in accordance with the findings in the study by Svensson and coworkers [15]. Consequently, we continue to use cell-saving device blood routinely, and to minimize the use of bank blood. Additionally, precise evaluation of the intraoperative coagulation status of the patients enables use of targeted component-specific replacement therapy, rather than indiscriminate use of blood products to combat bleeding.
In conclusion, respiratory complications after repair of DTA and TAA aneurysms have a significant impact on mortality, functional status, and length of stay. Preoperative identification of patients at high risk for respiratory complications is important. Subsequently, optimization of pulmonary function before surgery, meticulous intraoperative management, avoidance of excessive blood and blood product administration, early extubation, and liberal use of early tracheostomy may help to reduce the impact of these complications on outcome.
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