- Email: [email protected]
Pulmonary risk factors of elective abdominal aortic surgery
Pulmonary risk factors of elective abdominal aortic surgery Keith D. Calligaro, M D , Daniel J. Azurin, M D , M a t t h e w J. Dougherty, M D , R a h u l Dandora, BS, Steve M. Bajgier, P h D , Steven Simper, M D , R o n a l d P. Savarese, M D , Carol A. Raviola, M D , and Dominic A. DeLaurentis, M D , Philadelphia, Pa.
Purpose: The purpose of this study was to retrospectively identify risk factors for postoperative pulmonary complications in patients undergoing elective abdominal aortic surgery via a midline incision. Methods- We reviewed 181 consecutive patients who underwent operation between July 1986 to December 1992. Preoperative factors analyzed[ included age, sex, diabetes mellitus, history of smoking, chronic obstructive pulmom ry disease, obesity, indication for surgery (aneurysm [126] or aortoiliac occlusive disease [AIOD] [55]), history of coronary artery disease, length of preoperative hospital stay, American Society of Anaesthesiologists class, and pulmonary function tests. Intraoperative factors analyzed included endotracheal tube diameter, percent of inspired oxygen, blood loss, blood and crystalloid replacement, total operative time, epidural analgesia, and stress ulcer prophylaxis. Results: Although the operative mortality rate was only 1.7% (3 of 181), major pulmonary complications occurred in 29 (16%) patients, including two lung-related deaths. Pneumonia occurred in 17 (9%) patients, prolonged intubation greater than 24 hours occurred in nine (5%), and reintubation caused by pulmonary insufficiency occurred in three (2%). On univariate analysis, the following were associated with m~jor pulmonary complications (p < 00.05): American Society of Anaesthesiologists class IV, age greater than 70 years, ideal body weight greater than 150%, forced vital capacity of 80% or less predicted, forced expiratory flow rate (25 to 75) of 60% or less predicted, crystalloid replacement greater than 6 L, and total operative time greater than 5 hours. Conclusions: The presence of these pulmonary risk factors, notably increased age and weight, decreased forced vital capacity and forced expiratory flow rate (25 to 75), and expected prolonged operative time, influences our decision not to proceed with surgery for small aortic aneurysms or for AIOD causing dandication. Patients at high pulmonary risk with AIOD who require revascularization for limb salvage would be more likely to undergo extraanatomic bypass. Pulmonary risk factors may play as important a role as cardiac factors in elective aortic surgery. (I VASC SURG 1993;18:914-21.)
To increase the safety of elective aortic surgery, significant attention has been devoted to the identification of risk factors that may be associated with perioperative complications. Recent attention has been directed to the identification of cardiac risk
From the Section of Vascular Surgery, PennsylvaniaHospital, University of Pennsylvania School of Medicine, and the Department of Quantitative Methods (Dr. Bajgier), Drexel University,Philadelphia. Supported by a grant from the John F. ConneUyFoundation. Presented at the SeventhAnnualMeetingof the Eastern Vascular Society, Philadelphia,Pa., April 29-May2, 1993. Reprint requests: Keith D. CaUigaro,MD, Suite 101, 700 Spruce St., Philadelphia,PA 19106. Copyright © 1993 by The Society for Vascular Surgery and InternationalSocietyfor CardiovascularSurgery,North American Chapter. 0741-5214/93/$1.00 + .10 24/6/51369 914
factors. We have been struck by the seemingly high rate o f pulmonary complications in our patients and by the paucity of reports addressing this subject) 6 Major pulmonary complications after elective abdominal aortic surgery of only 3% to 8% have been reported in several large series. 1-3 Pulmonary complications in these reports were not strictly defined and were possibly underestimated. Because a recent randomized study by Cambria et al) did not document decreased pulmonary complications with a retroperitoneal approach, our group and possibly most vascular surgeons continue to use a midline incision for routine abdominal aortic operations. The purpose of this study was to identify preoperative and intraoperative pulmonary risk factors in patients undergoing elective abdominal aortic surgery via a midline incision.
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MATERIAL AND METHODS We reviewed 181 consecutive patients who underwent elective abdominal aortic surgery via a midline incision between July 1986 and December 1992 at Pennsylvania Hospital. Patients were excluded from analysis if they required emergency aortic surgery, underwent concomitant major nonvascular surgery such as a colon resection or gastrectomy, had incomplete hospital records, or were approached via a retroperitoneal incision. During this same time interval, 24 patients tmderwent emergency aortic surgery. Rupture was found in 21 patients (10 died), and an intact aorta was documented in three patients who survived surgery. Preoperative risk factors. These variables included age, sex, history of smoking (past or present), history of coronary artery disease, diabetes mellitus, hypertension, chronic obstructive pulmonary disease (COPD) based on clinical impression or chest radiography (CXR) findings, pulmonary function tests (PFTs), obesity as defined by ideal body weight (IBW), 7 indication for surgery (aneurysm [126] or aortoiliac occlusive disease [55]), length of preoperative stay, and the American Society of Anaesthesiologists (ASA) Class. 8 Intraoperative risk factors. These variables included the percent inspired oxygen (% FI-O2) administered during surgery, operative time, diameter of the endotracheal tube, use ofepidural analgesia, estimated blood loss, blood replacement, crystalloid replacement, and stress ulcer prophylaxis (none, histamine blockers including cimetidine or ranitidine, oral antacid titration, or sucralfate). Major pulmonary complications. Major complications were defined as pneumonia, reintubation as a result of pulmonary insufficiency, and postoperative intubation more than 24 hours solely because of respiratory problems. Postoperative pneumonia was strictly defined as the simultaneous presence of all of the following: (1) new CXR infiltrate as interpreted by a staff radiologist, (2) persistent fever greater than 38 ° C, (3) persistently elevated white blood cell count, or a newly elevated white blood cell count after it had returned to normal after operation, and (4) administration of intravenous antibiotics as a result of these three findings. 2,9,1° Minor pulmonary complications. The only finding that we considered as a minor pulmonary complication was atelectasis. This complication was based on CXR findings associated with fever greater than 38 ° C that prompted further work-up of the fever, including sputum and blood cultures, urinalysis, and repeat CXRs. Every patient underwent CXR in the recovery room and on the first postoperative day.
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Statistical analyses were performed by use of MINITAB (MINITAB, Inc., State College, Pa.) and SAS (SAS Institute, Inc., Cary, N. C.) statistical software packages. A test of differences in proportions with a z statistic as the approximate correct statistic was used to assess the univariate statistical significance of the association between respiratory failure and each categorical variable. Discriminate analysis was used to assess the relationship between the risk of respiratory failure and each interval-scaled study factor. Stepwise logistic regression analysis was used to select from the study factors a set of independent risk factors that demonstrated a simultaneous significant association with respiratory failure. Because some variables have missing values for several patients, loss of power may result from multivariate analysis (which deletes patients with missing data). Most statistical tests were directional andp values of 0.05 or less were considered significant. RESULTS Morbidity and mortality rates. In this series of 181 patients who underwent elective abdominal aortic surgery via midiine incision, the mortality rate was 1.7% (3 of 181). Two of the three deaths were due to pneumonia, and the third was due to postoperative hemorrhage. The total pulmonary complication rate was 54% (97 of 181). Major complications occurred in 16% (29) of patients, and minor complications (atelectasis) occurred in 38% (68). Of the 29 patients who had major pulmonary complications, 9% (16) had pneumonia, 5% (9) required prolonged intubation more than 24 hours after operation solely because of respiratory compromise, and 2% (4) required reintubation as a result of pulmonary insufficiency. Of the 16 patients who had pneumonia, one died as a result of multiple organ failure, and one of adult respiratory distress syndrome. Of the 14 survivors, one had adult respiratory distress syndrome and one had septic shock. Sputum and blood cultures. Sputtun specimens from the 16 patients with pneumonia cultured bacteria in eight cases, including tmidentified gramnegative rods (four patients), Enterobacter organisms (2), Staphylococcus epidermidis (1) and Haemophilus influenzae (1). Blood culture results were positive in two patients: one patient's blood (and sputum) grew Enterobacter organisms, and another patient's blood (with negative sputum culture results) grew Staphy-
lococcusa u r e u s . Risk factors (Table I). The preoperative risk factor with the strongest correlation with major pulmonary complications was the ASA class. Fifty percent of patients with ASA class 4 had major
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Table I. Risk factors associated with pulmonary complications of abdominal aortic surgery* Total Variable ASA class
Obesity
Age
Group
%
No.
%
No.
%
p Value
32 139 10
17% 77% 6%
4 19 5
13% 14% 50%
28 120 5
87% 86% 50%
0.005
Total
181
100%
< 120% _>120%
92 36
72% 18%
17 7
19% 19%
75 29
81% 81%
0.450
Total
128
100%
_<125% > 125%
102 26
80% 20%
17 7
17% 27%
85 19
83% 73%
0.160
Total
128
100%
-< 150% > 150%
121 7
95% 5%
21 3
17% 43%
100 4
83% 57%
0.042
Total
128
100%
36 145
20% 80%
4 25
11% 17%
32 120
89% 83%
0.185
181
100%
109 72
60% 40%
13 16
12% 22%
96 56
88% 78%
0.037
181
100%
172 9
95% 5%
11 3
15% 33%
161 6
85% 67%
0.073t
Total
181
100%
_<80% > 80%
29 35
45% 55%
10 5
35% 14%
19 30
65% 86%
0.029
Total
64
100%
35 29
55% 45%
11 4
31% 14%
24 25
69% 86%
0.048
64
100%
71 110
39% 61%
8
21
11% 19%
62 89
89% 81%
0.080
181
100%
116 65
64% 36%
14 15
12% 23%
102 50
88% 77%
0.027
181
100%
110 71
61% 49%
17 13
15% 18%
93 58
85% 82%
0.250
181
100%
140 41
77% 23%
20 10
14% 24%
120 31
86% 76%
0.048
181
100%
160 21
88% 12%
22 7
14% 33%
138 14
86% 67%
0.011
181
100%
2 3 4
<-60 > 60
-<70 > 70 Total -< 80 > 80
FEF 25-75 (% of pred)
<_60% > 60% Total
Operative time (hours)
<4 >4 Total <__5 >5 Total
CrystaUoid (liters in OR)
Without major complications
No.
Total
FVC (% of pred)
With major complications
<5 >5 Total -<6 >6 Total <__7 >7 Total
OR, Operating room. *Not all "totals" = 181 patients because some data were not available in every patient. tThis value did not reach statistical significance because of small sample size of patients greater than 80 years old (although there was a steady percent increase in pulmonary complications with increasing age).
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complications compared with 13% of patients with dass II and 14% of patients with class III (p = 0.01). Additionally, a forced vital capacity (FVC) of 80% of normal or less, a forced expiratory flow rate (FEF 25 to 75) of 60% of normal or less, IBW greater than 150% of normal, and age greater than 70 years all were significant risk factors of postoperative pulmonary complications. Intraoperative risk factors that correlated with major pulmonary complications included operative time more than 5 hours and administration of more than 6 L crystalloid during surgery. Patients who had major pulmonary complications had significantly longer postoperative intensive care unit (ICU) and total hospital stays (7.4 and 21.7 days, respectively) than patients without major pulmonary complications (2.5 and 10.1 days, respectively) (p < 0.0001). The only significant risk factor predicting minor complications (atelectasis) was administration of greater than 5 L crystalloid during surgery (p = 0.03). Although the development of atelectasis was more than twice as likely in current smokers as in patients who never smoked (29% vs 13%, respectively), and the incidence of postoperative atelectasis rose with increasing operative times, these factors did not reach statistical significance (p = 1.03 for both variables). There was no significant difference in length of postoperative ICU or hospital stay between patients who did and did not have atelectasis. DISCUSSION Several studies have reported major pulmonary complications in fewer than 10% of patients, and a similarly low incidence of atelectasis, after elective aortic surgery. 1-3We maintained vigorous pulmonary toilet in patients undergoing aortic surgery, including frequent chest physiotherapy and incentive spirometry. The higher pulmonary complication rate in our series may be attributed to our definitions of these complications but more likely reflects our rigorous attempt to delineate all postoperative respiratory problems. Supporting this belief is our overall mortality rate of only 1.7% (3 of 181). Although it has been suggested that a midline incision as opposed to a retroperitoneal approach may increase pulmonary complications, 3,4 the only randomized study addressing this issue did not confirm this.1 Our definition of pneumonia is somewhat arbitrary. Most definitions of pneumonia include presence of a new lung infiltrate on CXR, fever greater than 38 ° C, and leukocytosis. 11-16 The presence of
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purulent secretions or sputum pathogens is considered essential by some investigators, ~113 but not by others. 14,1~ Half of the 16 patients who met our definition of pneumonia had positive sputum culture results. Horan et al) z documented that only 6% of patients with nosocomial infections had positive blood culture results in his series, and in our patients blood culture results were positive in only two of 16 (13%) patients with pneumonia. Preoperative factors predictive of pulmonary complications. The ASA class has been shown to be reproducible and correlate well with operative mortalky rates. 8 The ASA class is divided into five categories. Class i includes the patients at lowest risk; class 5 includes patients who require emergency surgery with little chance of survival. The ASA classification includes hypertension, organic heart disease, diabetes mellitus, extremes of age, obesity, COPD, and emergency operations. It is not surprising that the ASA class proved to be the most statistically significant factor associated with major pulmonary complications because this classification includes several variables that we found to correlate with postoperative pulmonary complications. The incidence of major pulmonary complications rose with increasing IBW but did not attain statistical significance until a value greater than 150% was reached. Although Crapo et al?8 suggested that preoperative spirometric testing is not indicated in morbidly obese patients with no other identifiable risk factors for postoperative respiratory complications, Jackson 19 reported that PFTs should be obtained before operation in obese patients because of their increased pulmonary risk. In a prospective study by Latimer et al., 2° obesity defined by 10% above the Metropolitan Life Insurance Tables was the most important risk factor associated with clinically significant atelectasis after upper abdominal surgery and occurred in 53% of his patients. Although advancing age has been reported as not being associated with postoperative pulmonary complications,21,22we found a significantly increased rate of major respiratory complications in patients older than 70 years. Jackson 19 agreed that PFTs should be obtained in patients more than 60 years old. The exact role of PFTs to predict postoperative pulmonary complications in patients undergoing abdominal aortic surgery is not well defined. In a review of 135 clinical articles assessing the value of preoperative spirometry before any abdominal operations, Lawrence et al. 23 concluded that the value of preoperative spirometry is limited, even though
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significant postoperative pulmonary complications occur in 5% to 70% of all upper abdominal operations. Jackson ~9 suggested that preoperative PFTs should be obtained in patients who are older than 60 years, have a 20-pack-year or greater history of smoking, are obese, or have a productive cough. We found that FVC of 80% or less of normal and an FEF (25 to 75) of 60% or less correlated with respiratory complications. Similarly, Gracey et al.24 found that FVC less than 75% and FEF (25 to 75) less than 50% correlated with a high risk of prolonged mechanical ventilation after operation. Intraoperafive factors predictive of pulmonary complications. Prolonged operative time correlated with pulmonary comphcations in our study (greater than 5 hours) and in others (greater than 3.5 hours). 2° We encourage early extubation because prolonged intubation may predispose to pulmonary complications. In a prospective study of trauma patients, Rodriguez 1° found that as the number of days of mechanical ventilation continued, the probability of hospital-acquired pneumonia increased. Pulmonary complications associated with prolonged operative time, and specifically prolonged aortic clamp time, may be related to prolonged ischemia of the lower extremities. Reperfusion of the lower extremities after prolonged aortic clamping may lead to a pulmonary capillary defect. This mechanism may be mediated via inflammatory agents such as cytokines, complement, mast cells, and leukotrienes that become activated during aortic surgery) °,25 Although increasing volumes of blood transfusion did not correlate with pulmonary complications, large volumes (greater than 6 L) of crystalloid did. There is conflicting experimental and clinical evidence regarding extravasation of crystalloid and colloid into the lungs. Crystalloid may be more likely to leak into the interstitial and alveolar spaces than blood products and predispose to respiratory complications. 26 For routine aortic surgery in a hemodynamically stable patient, administration of excess crystalloid should be avoided. Preoperative factors not predictive of pulmonary complications. Length of preoperative hospital stay, which varied between 1 and 25 days (mean 2.9 days), did not correlate with pulmonary comphcations. We suspected that increased exposure to potentially infected hospitalized patients might increase the pulmonary risk, bur this did not prove to be true. We did not find that current or past history of smoking was predictive of major pulmonary comphcations. Svensson et al.,s however, found that history of smoking was an independent predictor of respi-
December1993
ratory failure after thoracoabdominal aortic surgery. Jackson 19 suggested that patients with a productive cough or those with more than a 20-pack-year history of smoking are at greater risk of pulmonary complications. Warner et al. 27found a statistically significant decrease in pulmonary complications in patients who quit smoking at least 8 weeks before undergoing coronary artery bypass grafting. COPD based on clinical or CXR findings without PFTs did not prove to be a statistically significant factor that correlated with major pulmonary comphcations although a trend existed: 22% of patients with COPD had major complications compared with 14% of patients without COPD (p = 0.17). Smith et al..6 reported that respiratory complications developed in five of 10 patients with severe COPD after aortic reconstruction, although three of these were easily managed and there were no deaths. Intraoperative factors not predictive of pulmonary complications. We did not document that increased amounts of blood loss or blood replacement predicted pulmonary complications. Diehl et al. 2 found that more than 4 units of transfused homologous blood correlated with increased pulmonary insufficiency. We also did not find any correlation with respiratory comphcations and the type of transfused blood (autologous, heterologous, Cell Saver Autotransfusion Device [Haemonetics Corp., Braintree, Mass.]). One-hundred forty of our patients received greater than 80% F I - O 2 during surgery and 35 received 80% FI-O 2 or less. Exposing a patient to higher inspired oxygen levels during surgery might theoretically predispose to alveolar damage, but this factor showed no correlation with pulmonary complications. We also suspected that a smaller endotracheal tube diameter might require increased inspiratory effort during weaning attempts, but the size of the tube did not correlate with prolonged postoperative intubation or pneumonia. Our study and recent randomized trials and metaanalysis studies did not document a correlation between histamine2 blockers or antacid therapy and postoperative pneumonia. 2s,29 Some reports have suggested that stress ulcer prophylaxis leads to bacterial overgrowth in the stomach and predisposes to pneumonia as a result of subclinical episodes of aspiration of infected gastric contents. 1°,15 Several randomized reports have noted that sucralfate, which does not raise the pH of the stomach, was associated with a lower incidence of hospital-acquired pneumonia when compared with histamine2 blockers or antacid therapy. 3°-32 Lastly, we did not demonstrate that epidural analgesic decreased pulmonary complications. This
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technique theoretically diminishes postoperative abdominal pain and potentially allows deeper inSpirations. Cambria ~ reported that liberal use of epidural anesthetic contributed to an improved respiratory complication rate in patients undergoing abdominal aortic surgery. Although patients who received epidural analgesic tended to be older and were more likely to have worse pulmonary function test results in our study, patients who did not receive epidural analgesic were more likely to be obese, have COPD, and have received greater volume of crystalloid during operation. Thus, our study did not confirm that use of epidural analgesic helps prevent pulmonary complications. Cost. Major pulmonary complications lead to increased medical cost as documented by the significantly longer postoperative ICU and hospital stay in our patients with major pulmonary complications. Preoperative chest physiotherapy, incentive spirometry, bronchodilators, and antibiotics, along with similar postoperative maneuvers, may reduce pulmonary complications in patients who are at high risk. 19 We have documented a high incidence of pulmonary complications after elective abdominal aortic surgery performed via a midline incision and have applied the results of this study in the following ways. The presence of risk factors (advanced age, extreme obesity, low FVC and FEF (25 to 75), expected prolonged operative time) influences our decision not to proceed with surgery for small aortic aneurysms and for claudication caused by aortoiliac occlusive disease. These factors must be considered along with evidence that COPD increases the risk of rupture of even small aortic aneurysms. 33 In those patients at high pulmonary risk with aortoiliac stenosis who require revascularization for limb salvage, we would be more likely to perform an extraanatomic bypass. Despite modern anesthetic techniques, our results confirm that aortic surgery should still be performed as expeditiously as possible. Finally, the surgeon should assume joint responsibility with the anesthesiologist for fluid replacement during the operation, and administration of excess crystalloid should be avoided.
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5.
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7.
8.
9.
10.
11.
12.
13. 14.
15.
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17. 18.
19. 20.
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approach for reconstruction of the infrarenal abdominal aorta. J VASC SURG 1987;5:19-27. Leather RP, Shah DM, Kaufman JL, Fitzgeral KM, Chang BB, Feustel PJ. Comparative analysis of retroperitoneal and transperitoneal aortic replacement for aneurysm. Surg Gynecol Obstet 1989;168:387-93. Svensson LG, Hess KR, Coselli JS, Sail HJ, Crawford ES. A prospective study of respiratory failure after high-risk surgery on the thoracoabdominal aorta. J VAsc SuRe 1991;14:27182. Smith PK, Fuchs ICA, Sabiston DC. Surgical management of aortic abdominal ancurysms in patients with severe pulmonary insufficiency. Surg Gynccol Obstet 1980;151:407-11. Boh LE. Ideal or lean body weight calculation. In: Boh LE, ed. Clinical clerkship manual. Vancouver: Applied Therapeutics, Inc., 1992:6-7. Dripps RD. Physical status and risk. In: Dripps RD, Eckenhoff JF, Vandam LD, eds. Introduction to anesthesia: the principles of safe practice. Philadelphia: WB Saunders, 1977:13-15. Meduri GU. Ventilator associated pneumonia in patients with respiratory failure: a diagnostic approach. Chest 1990;97: 1208-19. Rodtiguez JL. Hospital-acquired gram-negative pneumonia in critically ill, injured patients. Am J Surg 1993;165(Suppl HA) :34S-42S. Rello J, Quintana E, Ausina, et al. Incidence, etiology, and outcome ofnosocomial pneumonia in mechanically ventilated patients. Chest 1991;100:439-44. Simms lJ, DeMaria E, McDonald L, Peterson D, Robinson A, Burchard K. Role of gastric colonization in the development of pneumonia in critically ill trauma patients: results of a prospective randomized trial. J Trauma 1991;31: 531-6. Mock CN, Burchard KW, Hassan F, et al. Surgical intensive care unit pneumonia. Surgery 1988;104:494-9. Johanson WG Jr, Pierce AK, Sanford J-P, Thomas GD. Nosoconfial respiratory infections with gram-negative bacilli: the significance of colonization of the respiratory tract. Ann Intern Med 1972;77:701-6. 8cheld WM. Developments in the pathogenesis, diagnosis and treatment of nosocomial pneumonia. Surg Gynecol Obstet 1991;172(Suppl) :42-53. Matthew EB, Holstrom FMG, Kaspar RL. A simple method for diagnosing pneumonia in intubated or tracheostomized patients. Crit Care Med 1977;5:76-81. Horan TC, White JW, Jarvis WR. Nosocomial infection surveillance, 1984. Morb Mortal WHy Rep 1986;35[Suppl]: 17-29. Crapo RO, Kelly TM, Elliott G, Jones SB. Spirometry as a preoperative screening test in morbidly obese patients. Surgery 1986;99:763-8. Jackson CV. Preoperative pulmonary evaluation. Arch Intern Med 1988; 148:2120-7. Latimer RG, Dickman M, DayWC, et al. Ventilatorypatterns and pulmonary complications after upper abdominal surgery determined by preoperative and postoperative computerized spirometry and blood gas analysis. Am J Surg 1971;122:62232. Tarhan S, Mofitt EA, Sessler AD, et al. Risk of anesthesia mid surgery in patients with chronic bronchitis and chronic obstructive pulmonary disease. Surgery 1973;74:720-6. Mitchell C, Garrahy P, Peake P. Postoperative respiratory morbidity: Identification and risk factors. Aust N Z I Surg 1982;52:203-9. Lawrence VA, Page CP, Harris GD. Preoperative spirometry
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Submi~edMayl2, 1993;accep~d Sept. 8, 1993.
DISCUSSION Dr. John J. Ricotta (Buffalo, N. Y.). This study provides us with some useful data confirming some prejudices such as the value of pulmonary function tests and raises some questions about others such as the importance of blood transfusions and epidural anesthesia. Do you have any idea about how accurate or how repeatable the ASA classification is by the anesthesiologist? You indicated that prolonged intubation was greater than 24 hours. H o w many of these patients underwent ventilation greater than 3 or 4 days? What was the relationship of intubation to postoperative pneumonia? Is your complication rate, which I agree is higher than is reported b y many people, higher because you were more assiduous in looking for these complications? Do you have any data on whether the postoperative stay in patients who had minor pulmonary complications was different than in those who did not have any? Were there standard indications for epidural anesthesia, or was this applied on a case-by-case basis? If it was not applied in a standard way, could you give us some insight about your indications for the use of epidural anesthesia in patients who are undergoing aortic surgery? Did yon apply multivariant analysis techniques to these data, or were the results that you presented based on univariant analysis? If you did apply multivariant techniques, were factors other than ASA class predictive of outcome? Aside from planning expeditious operation and from perhaps tailoring the operation in patients with abnormal pulmonary function test results, are there other things that you suggest we do in terms of the use of preoperative bronchodilators or preoperative pulmonary toilet the use of preoperative caaltures, sputum cultures with directed antibiotic coverage, or some sort of standard perioperative respiratory and anesthetic care that might decrease the incidence of these complications?
Dr. Keith D. Calligaro. The ASA class has been documented in several other series to be reproducible and validated, especially relating to cardiac complications in patients undergoing general surgery. In general, patients were either extubated within 24 hours or after 35 or 36 hours. There was no relationship to pneumonia. There was not a difference in postoperative stay in terms of people who had minor complications, but there was a significantly increased length of ICU stay and hospital stay in patients who had major pulmonary complications as we defined them. That's one of the main points we wanted to get across. We chose strict definitions because all of these patients underwent additional tests that raised the cost of their hospitalization. By identifying risk factors, we could be more aggressive in the future and possibly prevent these complications. Patients were not randomized to receive epidural anesthetic. Our data did not show a benefit, and it's been controversial in the literature whether there really is a benefit. We used univariant analysis. In terms of preoperative bronchodilators and culture results, we did not examine these factors in this study. This would require a prospective study with very large numbers to really show any benefit. Dr. Enrico Ascer (Brooklyn, N. Y.). I have noticed in my practice over the last 10 years that some of these patients who have pulmonary complications are the ones who had undergone prolonged cross-clamping, and I suspect as Dr. Blaisdell has shown many years ago, that perhaps ischemia reperfusion may affect the lungs specifically and that's why we get extravasation of fluid, activation of white blood cells and so on. I wonder whether these patients who did have pulmonary complications are the ones who had prolonged cross-clamped time in comparison to the ones who did not.
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Second, I wonder if just telling our anesthesiologist not to give fluid to the patient is really the correct thing to do. Some of these patients need fluids to keep up their effective intravascular volume. If the fluid is extravasating to the extracellular space, how are we going to be able to keep that intravascular volume enough to perfuse the kidneys, the brain, and the heart? I'm not sure that we should hold the fluid. We have to find better ways to keep that intravascular volume effective and not just hold fluids. Dr. Calligaro. The cross-clamp time of the aorta correlated with the complication rate. The only way to prove whether reperfusion led directly to the pulmonary complications would require measuring certain blood parameters. A plethora of literature suggests that reperfusion syndrome after leg ischemia may lead to pulmonary complications, not only in animal studies but in some human studies, so that may very well play a role. We are not suggesting that anesthesiologists be told not to give crysralloid. We've been struck, though, by a very liberal attitude that our anesthiologists take with some of
our patients in giving a lot of crystalloid for a very short operation that went very smoothly. This study suggests that we should be more cognizant of that and not give up all responsibility for fluid resuscitation to the anesthesiologist during the surgery. Dr. Richard Spence (Camden, N. J.). There is clear evidence that blood transfusion is an immunomodulator and the incidence of infection after operation, both at the wound site and distant sites, is about 25% in patients who are transfused. There is an entity known as TRALI, or transfiasion-related acute lung injury, that's becoming more and more recognized in patients that are transfused. Did you stratify for the number of units your patients received that came from the blood bank, and did you differentiate between those who received homologous blood versus autologous blood? Dr. Calligaro. We specifically looked at blood transfusions and divided it into autologous, homologous, and Cell Saver blood. There was absolutely no correlation with any of those factors.
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FOUNDATION
GRANT AWARD
The Lifeline Foundation of the Society for Vascular Surgery invites grant applications for funding of meritorious research by young surgical investigators. The awards are intended for surgeons who have completed their formal surgical education in general surgery and who have completed or are in an advanced training program ha vascular surgery. To be considered for selection a candidate: 1. Should be certified by the American Board of Surgery or have completed the requirements for certification 2. Should submit an application within 3 years of completion of an approved residency training program 3. Must have either a faculty appointment in an approved medical school in the United States or Canada or have received an academic appointment within the guidelines of the applicant's institution Grant awards are not intended to supplement salary, which will remain the responsibility of the institution in which the awardee holds an appointment. The awardee is expected to devote a significant amount of time to the fianded project. A progress report will be presented by the investigators during the annual meeting of the Society for Vascular Surgery. A grant awards committee will review competitive applications. It is anticipated that two grants will be awarded annually totaling $50,000 each to include indirect costs. Each award will be for I year with the option to extend for an additional year. Grant applications may be obtained from: The Lifeline Foundation Society for Vascular Surgery Thirteen Elm St. Manchester, MA 01944 (508)526-8330 The deadline for receiving applications in the Foundation office is January 15, 1994. Funds will be awarded by July 1, 1994.
Purpose: The purpose of this study was to retrospectively identify risk factors for postoperative pulmonary complications in patients undergoing elective abdominal aortic surgery via a midline incision. Methods- We reviewed 181 consecutive patients who underwent operation between July 1986 to December 1992. Preoperative factors analyzed[ included age, sex, diabetes mellitus, history of smoking, chronic obstructive pulmom ry disease, obesity, indication for surgery (aneurysm [126] or aortoiliac occlusive disease [AIOD] [55]), history of coronary artery disease, length of preoperative hospital stay, American Society of Anaesthesiologists class, and pulmonary function tests. Intraoperative factors analyzed included endotracheal tube diameter, percent of inspired oxygen, blood loss, blood and crystalloid replacement, total operative time, epidural analgesia, and stress ulcer prophylaxis. Results: Although the operative mortality rate was only 1.7% (3 of 181), major pulmonary complications occurred in 29 (16%) patients, including two lung-related deaths. Pneumonia occurred in 17 (9%) patients, prolonged intubation greater than 24 hours occurred in nine (5%), and reintubation caused by pulmonary insufficiency occurred in three (2%). On univariate analysis, the following were associated with m~jor pulmonary complications (p < 00.05): American Society of Anaesthesiologists class IV, age greater than 70 years, ideal body weight greater than 150%, forced vital capacity of 80% or less predicted, forced expiratory flow rate (25 to 75) of 60% or less predicted, crystalloid replacement greater than 6 L, and total operative time greater than 5 hours. Conclusions: The presence of these pulmonary risk factors, notably increased age and weight, decreased forced vital capacity and forced expiratory flow rate (25 to 75), and expected prolonged operative time, influences our decision not to proceed with surgery for small aortic aneurysms or for AIOD causing dandication. Patients at high pulmonary risk with AIOD who require revascularization for limb salvage would be more likely to undergo extraanatomic bypass. Pulmonary risk factors may play as important a role as cardiac factors in elective aortic surgery. (I VASC SURG 1993;18:914-21.)
To increase the safety of elective aortic surgery, significant attention has been devoted to the identification of risk factors that may be associated with perioperative complications. Recent attention has been directed to the identification of cardiac risk
From the Section of Vascular Surgery, PennsylvaniaHospital, University of Pennsylvania School of Medicine, and the Department of Quantitative Methods (Dr. Bajgier), Drexel University,Philadelphia. Supported by a grant from the John F. ConneUyFoundation. Presented at the SeventhAnnualMeetingof the Eastern Vascular Society, Philadelphia,Pa., April 29-May2, 1993. Reprint requests: Keith D. CaUigaro,MD, Suite 101, 700 Spruce St., Philadelphia,PA 19106. Copyright © 1993 by The Society for Vascular Surgery and InternationalSocietyfor CardiovascularSurgery,North American Chapter. 0741-5214/93/$1.00 + .10 24/6/51369 914
factors. We have been struck by the seemingly high rate o f pulmonary complications in our patients and by the paucity of reports addressing this subject) 6 Major pulmonary complications after elective abdominal aortic surgery of only 3% to 8% have been reported in several large series. 1-3 Pulmonary complications in these reports were not strictly defined and were possibly underestimated. Because a recent randomized study by Cambria et al) did not document decreased pulmonary complications with a retroperitoneal approach, our group and possibly most vascular surgeons continue to use a midline incision for routine abdominal aortic operations. The purpose of this study was to identify preoperative and intraoperative pulmonary risk factors in patients undergoing elective abdominal aortic surgery via a midline incision.
IOURNAL OF VASCULAR SURGERY Volume 18, Number 6
MATERIAL AND METHODS We reviewed 181 consecutive patients who underwent elective abdominal aortic surgery via a midline incision between July 1986 and December 1992 at Pennsylvania Hospital. Patients were excluded from analysis if they required emergency aortic surgery, underwent concomitant major nonvascular surgery such as a colon resection or gastrectomy, had incomplete hospital records, or were approached via a retroperitoneal incision. During this same time interval, 24 patients tmderwent emergency aortic surgery. Rupture was found in 21 patients (10 died), and an intact aorta was documented in three patients who survived surgery. Preoperative risk factors. These variables included age, sex, history of smoking (past or present), history of coronary artery disease, diabetes mellitus, hypertension, chronic obstructive pulmonary disease (COPD) based on clinical impression or chest radiography (CXR) findings, pulmonary function tests (PFTs), obesity as defined by ideal body weight (IBW), 7 indication for surgery (aneurysm [126] or aortoiliac occlusive disease [55]), length of preoperative stay, and the American Society of Anaesthesiologists (ASA) Class. 8 Intraoperative risk factors. These variables included the percent inspired oxygen (% FI-O2) administered during surgery, operative time, diameter of the endotracheal tube, use ofepidural analgesia, estimated blood loss, blood replacement, crystalloid replacement, and stress ulcer prophylaxis (none, histamine blockers including cimetidine or ranitidine, oral antacid titration, or sucralfate). Major pulmonary complications. Major complications were defined as pneumonia, reintubation as a result of pulmonary insufficiency, and postoperative intubation more than 24 hours solely because of respiratory problems. Postoperative pneumonia was strictly defined as the simultaneous presence of all of the following: (1) new CXR infiltrate as interpreted by a staff radiologist, (2) persistent fever greater than 38 ° C, (3) persistently elevated white blood cell count, or a newly elevated white blood cell count after it had returned to normal after operation, and (4) administration of intravenous antibiotics as a result of these three findings. 2,9,1° Minor pulmonary complications. The only finding that we considered as a minor pulmonary complication was atelectasis. This complication was based on CXR findings associated with fever greater than 38 ° C that prompted further work-up of the fever, including sputum and blood cultures, urinalysis, and repeat CXRs. Every patient underwent CXR in the recovery room and on the first postoperative day.
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Statistical analyses were performed by use of MINITAB (MINITAB, Inc., State College, Pa.) and SAS (SAS Institute, Inc., Cary, N. C.) statistical software packages. A test of differences in proportions with a z statistic as the approximate correct statistic was used to assess the univariate statistical significance of the association between respiratory failure and each categorical variable. Discriminate analysis was used to assess the relationship between the risk of respiratory failure and each interval-scaled study factor. Stepwise logistic regression analysis was used to select from the study factors a set of independent risk factors that demonstrated a simultaneous significant association with respiratory failure. Because some variables have missing values for several patients, loss of power may result from multivariate analysis (which deletes patients with missing data). Most statistical tests were directional andp values of 0.05 or less were considered significant. RESULTS Morbidity and mortality rates. In this series of 181 patients who underwent elective abdominal aortic surgery via midiine incision, the mortality rate was 1.7% (3 of 181). Two of the three deaths were due to pneumonia, and the third was due to postoperative hemorrhage. The total pulmonary complication rate was 54% (97 of 181). Major complications occurred in 16% (29) of patients, and minor complications (atelectasis) occurred in 38% (68). Of the 29 patients who had major pulmonary complications, 9% (16) had pneumonia, 5% (9) required prolonged intubation more than 24 hours after operation solely because of respiratory compromise, and 2% (4) required reintubation as a result of pulmonary insufficiency. Of the 16 patients who had pneumonia, one died as a result of multiple organ failure, and one of adult respiratory distress syndrome. Of the 14 survivors, one had adult respiratory distress syndrome and one had septic shock. Sputum and blood cultures. Sputtun specimens from the 16 patients with pneumonia cultured bacteria in eight cases, including tmidentified gramnegative rods (four patients), Enterobacter organisms (2), Staphylococcus epidermidis (1) and Haemophilus influenzae (1). Blood culture results were positive in two patients: one patient's blood (and sputum) grew Enterobacter organisms, and another patient's blood (with negative sputum culture results) grew Staphy-
lococcusa u r e u s . Risk factors (Table I). The preoperative risk factor with the strongest correlation with major pulmonary complications was the ASA class. Fifty percent of patients with ASA class 4 had major
916
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Calligaro et al.
Table I. Risk factors associated with pulmonary complications of abdominal aortic surgery* Total Variable ASA class
Obesity
Age
Group
%
No.
%
No.
%
p Value
32 139 10
17% 77% 6%
4 19 5
13% 14% 50%
28 120 5
87% 86% 50%
0.005
Total
181
100%
< 120% _>120%
92 36
72% 18%
17 7
19% 19%
75 29
81% 81%
0.450
Total
128
100%
_<125% > 125%
102 26
80% 20%
17 7
17% 27%
85 19
83% 73%
0.160
Total
128
100%
-< 150% > 150%
121 7
95% 5%
21 3
17% 43%
100 4
83% 57%
0.042
Total
128
100%
36 145
20% 80%
4 25
11% 17%
32 120
89% 83%
0.185
181
100%
109 72
60% 40%
13 16
12% 22%
96 56
88% 78%
0.037
181
100%
172 9
95% 5%
11 3
15% 33%
161 6
85% 67%
0.073t
Total
181
100%
_<80% > 80%
29 35
45% 55%
10 5
35% 14%
19 30
65% 86%
0.029
Total
64
100%
35 29
55% 45%
11 4
31% 14%
24 25
69% 86%
0.048
64
100%
71 110
39% 61%
8
21
11% 19%
62 89
89% 81%
0.080
181
100%
116 65
64% 36%
14 15
12% 23%
102 50
88% 77%
0.027
181
100%
110 71
61% 49%
17 13
15% 18%
93 58
85% 82%
0.250
181
100%
140 41
77% 23%
20 10
14% 24%
120 31
86% 76%
0.048
181
100%
160 21
88% 12%
22 7
14% 33%
138 14
86% 67%
0.011
181
100%
2 3 4
<-60 > 60
-<70 > 70 Total -< 80 > 80
FEF 25-75 (% of pred)
<_60% > 60% Total
Operative time (hours)
<4 >4 Total <__5 >5 Total
CrystaUoid (liters in OR)
Without major complications
No.
Total
FVC (% of pred)
With major complications
<5 >5 Total -<6 >6 Total <__7 >7 Total
OR, Operating room. *Not all "totals" = 181 patients because some data were not available in every patient. tThis value did not reach statistical significance because of small sample size of patients greater than 80 years old (although there was a steady percent increase in pulmonary complications with increasing age).
JOURNAL OF VASCULAR SURGERY Volume 18, Number 6
complications compared with 13% of patients with dass II and 14% of patients with class III (p = 0.01). Additionally, a forced vital capacity (FVC) of 80% of normal or less, a forced expiratory flow rate (FEF 25 to 75) of 60% of normal or less, IBW greater than 150% of normal, and age greater than 70 years all were significant risk factors of postoperative pulmonary complications. Intraoperative risk factors that correlated with major pulmonary complications included operative time more than 5 hours and administration of more than 6 L crystalloid during surgery. Patients who had major pulmonary complications had significantly longer postoperative intensive care unit (ICU) and total hospital stays (7.4 and 21.7 days, respectively) than patients without major pulmonary complications (2.5 and 10.1 days, respectively) (p < 0.0001). The only significant risk factor predicting minor complications (atelectasis) was administration of greater than 5 L crystalloid during surgery (p = 0.03). Although the development of atelectasis was more than twice as likely in current smokers as in patients who never smoked (29% vs 13%, respectively), and the incidence of postoperative atelectasis rose with increasing operative times, these factors did not reach statistical significance (p = 1.03 for both variables). There was no significant difference in length of postoperative ICU or hospital stay between patients who did and did not have atelectasis. DISCUSSION Several studies have reported major pulmonary complications in fewer than 10% of patients, and a similarly low incidence of atelectasis, after elective aortic surgery. 1-3We maintained vigorous pulmonary toilet in patients undergoing aortic surgery, including frequent chest physiotherapy and incentive spirometry. The higher pulmonary complication rate in our series may be attributed to our definitions of these complications but more likely reflects our rigorous attempt to delineate all postoperative respiratory problems. Supporting this belief is our overall mortality rate of only 1.7% (3 of 181). Although it has been suggested that a midline incision as opposed to a retroperitoneal approach may increase pulmonary complications, 3,4 the only randomized study addressing this issue did not confirm this.1 Our definition of pneumonia is somewhat arbitrary. Most definitions of pneumonia include presence of a new lung infiltrate on CXR, fever greater than 38 ° C, and leukocytosis. 11-16 The presence of
Calligaro et al.
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purulent secretions or sputum pathogens is considered essential by some investigators, ~113 but not by others. 14,1~ Half of the 16 patients who met our definition of pneumonia had positive sputum culture results. Horan et al) z documented that only 6% of patients with nosocomial infections had positive blood culture results in his series, and in our patients blood culture results were positive in only two of 16 (13%) patients with pneumonia. Preoperative factors predictive of pulmonary complications. The ASA class has been shown to be reproducible and correlate well with operative mortalky rates. 8 The ASA class is divided into five categories. Class i includes the patients at lowest risk; class 5 includes patients who require emergency surgery with little chance of survival. The ASA classification includes hypertension, organic heart disease, diabetes mellitus, extremes of age, obesity, COPD, and emergency operations. It is not surprising that the ASA class proved to be the most statistically significant factor associated with major pulmonary complications because this classification includes several variables that we found to correlate with postoperative pulmonary complications. The incidence of major pulmonary complications rose with increasing IBW but did not attain statistical significance until a value greater than 150% was reached. Although Crapo et al?8 suggested that preoperative spirometric testing is not indicated in morbidly obese patients with no other identifiable risk factors for postoperative respiratory complications, Jackson 19 reported that PFTs should be obtained before operation in obese patients because of their increased pulmonary risk. In a prospective study by Latimer et al., 2° obesity defined by 10% above the Metropolitan Life Insurance Tables was the most important risk factor associated with clinically significant atelectasis after upper abdominal surgery and occurred in 53% of his patients. Although advancing age has been reported as not being associated with postoperative pulmonary complications,21,22we found a significantly increased rate of major respiratory complications in patients older than 70 years. Jackson 19 agreed that PFTs should be obtained in patients more than 60 years old. The exact role of PFTs to predict postoperative pulmonary complications in patients undergoing abdominal aortic surgery is not well defined. In a review of 135 clinical articles assessing the value of preoperative spirometry before any abdominal operations, Lawrence et al. 23 concluded that the value of preoperative spirometry is limited, even though
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significant postoperative pulmonary complications occur in 5% to 70% of all upper abdominal operations. Jackson ~9 suggested that preoperative PFTs should be obtained in patients who are older than 60 years, have a 20-pack-year or greater history of smoking, are obese, or have a productive cough. We found that FVC of 80% or less of normal and an FEF (25 to 75) of 60% or less correlated with respiratory complications. Similarly, Gracey et al.24 found that FVC less than 75% and FEF (25 to 75) less than 50% correlated with a high risk of prolonged mechanical ventilation after operation. Intraoperafive factors predictive of pulmonary complications. Prolonged operative time correlated with pulmonary comphcations in our study (greater than 5 hours) and in others (greater than 3.5 hours). 2° We encourage early extubation because prolonged intubation may predispose to pulmonary complications. In a prospective study of trauma patients, Rodriguez 1° found that as the number of days of mechanical ventilation continued, the probability of hospital-acquired pneumonia increased. Pulmonary complications associated with prolonged operative time, and specifically prolonged aortic clamp time, may be related to prolonged ischemia of the lower extremities. Reperfusion of the lower extremities after prolonged aortic clamping may lead to a pulmonary capillary defect. This mechanism may be mediated via inflammatory agents such as cytokines, complement, mast cells, and leukotrienes that become activated during aortic surgery) °,25 Although increasing volumes of blood transfusion did not correlate with pulmonary complications, large volumes (greater than 6 L) of crystalloid did. There is conflicting experimental and clinical evidence regarding extravasation of crystalloid and colloid into the lungs. Crystalloid may be more likely to leak into the interstitial and alveolar spaces than blood products and predispose to respiratory complications. 26 For routine aortic surgery in a hemodynamically stable patient, administration of excess crystalloid should be avoided. Preoperative factors not predictive of pulmonary complications. Length of preoperative hospital stay, which varied between 1 and 25 days (mean 2.9 days), did not correlate with pulmonary comphcations. We suspected that increased exposure to potentially infected hospitalized patients might increase the pulmonary risk, bur this did not prove to be true. We did not find that current or past history of smoking was predictive of major pulmonary comphcations. Svensson et al.,s however, found that history of smoking was an independent predictor of respi-
December1993
ratory failure after thoracoabdominal aortic surgery. Jackson 19 suggested that patients with a productive cough or those with more than a 20-pack-year history of smoking are at greater risk of pulmonary complications. Warner et al. 27found a statistically significant decrease in pulmonary complications in patients who quit smoking at least 8 weeks before undergoing coronary artery bypass grafting. COPD based on clinical or CXR findings without PFTs did not prove to be a statistically significant factor that correlated with major pulmonary comphcations although a trend existed: 22% of patients with COPD had major complications compared with 14% of patients without COPD (p = 0.17). Smith et al..6 reported that respiratory complications developed in five of 10 patients with severe COPD after aortic reconstruction, although three of these were easily managed and there were no deaths. Intraoperative factors not predictive of pulmonary complications. We did not document that increased amounts of blood loss or blood replacement predicted pulmonary complications. Diehl et al. 2 found that more than 4 units of transfused homologous blood correlated with increased pulmonary insufficiency. We also did not find any correlation with respiratory comphcations and the type of transfused blood (autologous, heterologous, Cell Saver Autotransfusion Device [Haemonetics Corp., Braintree, Mass.]). One-hundred forty of our patients received greater than 80% F I - O 2 during surgery and 35 received 80% FI-O 2 or less. Exposing a patient to higher inspired oxygen levels during surgery might theoretically predispose to alveolar damage, but this factor showed no correlation with pulmonary complications. We also suspected that a smaller endotracheal tube diameter might require increased inspiratory effort during weaning attempts, but the size of the tube did not correlate with prolonged postoperative intubation or pneumonia. Our study and recent randomized trials and metaanalysis studies did not document a correlation between histamine2 blockers or antacid therapy and postoperative pneumonia. 2s,29 Some reports have suggested that stress ulcer prophylaxis leads to bacterial overgrowth in the stomach and predisposes to pneumonia as a result of subclinical episodes of aspiration of infected gastric contents. 1°,15 Several randomized reports have noted that sucralfate, which does not raise the pH of the stomach, was associated with a lower incidence of hospital-acquired pneumonia when compared with histamine2 blockers or antacid therapy. 3°-32 Lastly, we did not demonstrate that epidural analgesic decreased pulmonary complications. This
JOURNAL OF VASCULAR SURGERY Volume 18, Number 6
technique theoretically diminishes postoperative abdominal pain and potentially allows deeper inSpirations. Cambria ~ reported that liberal use of epidural anesthetic contributed to an improved respiratory complication rate in patients undergoing abdominal aortic surgery. Although patients who received epidural analgesic tended to be older and were more likely to have worse pulmonary function test results in our study, patients who did not receive epidural analgesic were more likely to be obese, have COPD, and have received greater volume of crystalloid during operation. Thus, our study did not confirm that use of epidural analgesic helps prevent pulmonary complications. Cost. Major pulmonary complications lead to increased medical cost as documented by the significantly longer postoperative ICU and hospital stay in our patients with major pulmonary complications. Preoperative chest physiotherapy, incentive spirometry, bronchodilators, and antibiotics, along with similar postoperative maneuvers, may reduce pulmonary complications in patients who are at high risk. 19 We have documented a high incidence of pulmonary complications after elective abdominal aortic surgery performed via a midline incision and have applied the results of this study in the following ways. The presence of risk factors (advanced age, extreme obesity, low FVC and FEF (25 to 75), expected prolonged operative time) influences our decision not to proceed with surgery for small aortic aneurysms and for claudication caused by aortoiliac occlusive disease. These factors must be considered along with evidence that COPD increases the risk of rupture of even small aortic aneurysms. 33 In those patients at high pulmonary risk with aortoiliac stenosis who require revascularization for limb salvage, we would be more likely to perform an extraanatomic bypass. Despite modern anesthetic techniques, our results confirm that aortic surgery should still be performed as expeditiously as possible. Finally, the surgeon should assume joint responsibility with the anesthesiologist for fluid replacement during the operation, and administration of excess crystalloid should be avoided.
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7.
8.
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10.
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13. 14.
15.
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17. 18.
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before abdominal operations: a critical appraisal of its predictive value. Arch Intern Med 1989;149:280-5. GraceyDR, Divertie MB, Didier EP. Preoperative pulmonary preparation of patients with chronic obstructive pulmonary disease, Chest 1979;76:123-9. Goldman G, Welbourn R, Klausner JM, et al. Mast cells and leukotrienes mediate neutrophil sequestration and lung edema after remote ischemia in rodents. Surgery 1992;112:57886. Shoemaker WC. Comparison of the relative effectiveness of whole blood transfiasions and various types of fluid therapy in resuscitation. Crit Care Med 1976;4:71-8. Warner MA, Divertie MB, Tinker JH. Preoperative cessation of smoking and pulmonary compfications in coronary artery bypass patients. Anesthesiology 1984;60:380-3. Fabian TC, Boucher BA, Croce MA, et al. Pneumonia and stress ulceration in severely injured patients: a prospective evaluation of the effects of stress ulcer prophylaxis. Arch Surg 1993;128:185-92. Cook DJ, Laine LA, Guyatt Gift, Raffin TA. Nosocomial
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Submi~edMayl2, 1993;accep~d Sept. 8, 1993.
DISCUSSION Dr. John J. Ricotta (Buffalo, N. Y.). This study provides us with some useful data confirming some prejudices such as the value of pulmonary function tests and raises some questions about others such as the importance of blood transfusions and epidural anesthesia. Do you have any idea about how accurate or how repeatable the ASA classification is by the anesthesiologist? You indicated that prolonged intubation was greater than 24 hours. H o w many of these patients underwent ventilation greater than 3 or 4 days? What was the relationship of intubation to postoperative pneumonia? Is your complication rate, which I agree is higher than is reported b y many people, higher because you were more assiduous in looking for these complications? Do you have any data on whether the postoperative stay in patients who had minor pulmonary complications was different than in those who did not have any? Were there standard indications for epidural anesthesia, or was this applied on a case-by-case basis? If it was not applied in a standard way, could you give us some insight about your indications for the use of epidural anesthesia in patients who are undergoing aortic surgery? Did yon apply multivariant analysis techniques to these data, or were the results that you presented based on univariant analysis? If you did apply multivariant techniques, were factors other than ASA class predictive of outcome? Aside from planning expeditious operation and from perhaps tailoring the operation in patients with abnormal pulmonary function test results, are there other things that you suggest we do in terms of the use of preoperative bronchodilators or preoperative pulmonary toilet the use of preoperative caaltures, sputum cultures with directed antibiotic coverage, or some sort of standard perioperative respiratory and anesthetic care that might decrease the incidence of these complications?
Dr. Keith D. Calligaro. The ASA class has been documented in several other series to be reproducible and validated, especially relating to cardiac complications in patients undergoing general surgery. In general, patients were either extubated within 24 hours or after 35 or 36 hours. There was no relationship to pneumonia. There was not a difference in postoperative stay in terms of people who had minor complications, but there was a significantly increased length of ICU stay and hospital stay in patients who had major pulmonary complications as we defined them. That's one of the main points we wanted to get across. We chose strict definitions because all of these patients underwent additional tests that raised the cost of their hospitalization. By identifying risk factors, we could be more aggressive in the future and possibly prevent these complications. Patients were not randomized to receive epidural anesthetic. Our data did not show a benefit, and it's been controversial in the literature whether there really is a benefit. We used univariant analysis. In terms of preoperative bronchodilators and culture results, we did not examine these factors in this study. This would require a prospective study with very large numbers to really show any benefit. Dr. Enrico Ascer (Brooklyn, N. Y.). I have noticed in my practice over the last 10 years that some of these patients who have pulmonary complications are the ones who had undergone prolonged cross-clamping, and I suspect as Dr. Blaisdell has shown many years ago, that perhaps ischemia reperfusion may affect the lungs specifically and that's why we get extravasation of fluid, activation of white blood cells and so on. I wonder whether these patients who did have pulmonary complications are the ones who had prolonged cross-clamped time in comparison to the ones who did not.
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Calligaro et al.
Second, I wonder if just telling our anesthesiologist not to give fluid to the patient is really the correct thing to do. Some of these patients need fluids to keep up their effective intravascular volume. If the fluid is extravasating to the extracellular space, how are we going to be able to keep that intravascular volume enough to perfuse the kidneys, the brain, and the heart? I'm not sure that we should hold the fluid. We have to find better ways to keep that intravascular volume effective and not just hold fluids. Dr. Calligaro. The cross-clamp time of the aorta correlated with the complication rate. The only way to prove whether reperfusion led directly to the pulmonary complications would require measuring certain blood parameters. A plethora of literature suggests that reperfusion syndrome after leg ischemia may lead to pulmonary complications, not only in animal studies but in some human studies, so that may very well play a role. We are not suggesting that anesthesiologists be told not to give crysralloid. We've been struck, though, by a very liberal attitude that our anesthiologists take with some of
our patients in giving a lot of crystalloid for a very short operation that went very smoothly. This study suggests that we should be more cognizant of that and not give up all responsibility for fluid resuscitation to the anesthesiologist during the surgery. Dr. Richard Spence (Camden, N. J.). There is clear evidence that blood transfusion is an immunomodulator and the incidence of infection after operation, both at the wound site and distant sites, is about 25% in patients who are transfused. There is an entity known as TRALI, or transfiasion-related acute lung injury, that's becoming more and more recognized in patients that are transfused. Did you stratify for the number of units your patients received that came from the blood bank, and did you differentiate between those who received homologous blood versus autologous blood? Dr. Calligaro. We specifically looked at blood transfusions and divided it into autologous, homologous, and Cell Saver blood. There was absolutely no correlation with any of those factors.
SOCIETY FOR VASCULAR SURGERY LIFELINE
921
FOUNDATION
GRANT AWARD
The Lifeline Foundation of the Society for Vascular Surgery invites grant applications for funding of meritorious research by young surgical investigators. The awards are intended for surgeons who have completed their formal surgical education in general surgery and who have completed or are in an advanced training program ha vascular surgery. To be considered for selection a candidate: 1. Should be certified by the American Board of Surgery or have completed the requirements for certification 2. Should submit an application within 3 years of completion of an approved residency training program 3. Must have either a faculty appointment in an approved medical school in the United States or Canada or have received an academic appointment within the guidelines of the applicant's institution Grant awards are not intended to supplement salary, which will remain the responsibility of the institution in which the awardee holds an appointment. The awardee is expected to devote a significant amount of time to the fianded project. A progress report will be presented by the investigators during the annual meeting of the Society for Vascular Surgery. A grant awards committee will review competitive applications. It is anticipated that two grants will be awarded annually totaling $50,000 each to include indirect costs. Each award will be for I year with the option to extend for an additional year. Grant applications may be obtained from: The Lifeline Foundation Society for Vascular Surgery Thirteen Elm St. Manchester, MA 01944 (508)526-8330 The deadline for receiving applications in the Foundation office is January 15, 1994. Funds will be awarded by July 1, 1994.