- Email: [email protected]
The effects of aprotinin and steroids on generation of cytokines during coronary artery surgery
The Effects of Aprotinin and Steroids on Generation of Cytokines During Coronary Artery Surgery ¨ ner Gu¨lcan, MD, Ayda Tu¨rko¨z, MD, Ahmet C¸ig˘li, MD, Kadir But, MD, Nurzan Sezgin, MD, Rıza Tu¨rko¨z, MD, O ¨ zcan Ersoy, MD and M. O Objectives: To compare the efficacy of aprotinin and methylprednisolone in reducing cardiopulmonary bypass (CPB)–induced cytokine release, to evaluate the effect of myocardial cytokine release on systemic cytokine levels, and to determine the influence of cytokine release on perioperative and postoperative hemodynamics. Design: Prospective, randomized clinical trial. Setting: University teaching hospital and clinics. Participants: Thirty patients undergoing elective coronary artery bypass graft surgery. Interventions: Patients were randomly allocated into groups treated with aprotinin (n ⴝ 10) or methylprednisolone (n ⴝ 10) or into an untreated control group (n ⴝ 10). Aprotinin-treated patients received aprotinin as a high-dose regimen (6 ⴛ 106 KIU), and methylprednisolone-treated patients received methylprednisolone (30 mg/kg intravenously) before CPB. Measurements and Main Results: Patients were analyzed for hemodynamic changes and alveolar-arterial PO2 difference (AaDO2) until the first postoperative day. Plasma levels of proinflammatory cytokines (tumor necrosis factor [TNF]␣, interleukin [IL]-1, IL-6, and IL-8) were measured in peripheral arterial blood immediately before the induction of anesthesia, 5 minutes before CPB, 3 minutes after the start of CPB, 2 minutes after the release of the aortic cross-clamp, 1 hour after CPB, 6 hours after CPB, and 24 hours after CPB; and in coronary sinus blood immediately before CPB and 2 minutes after the release of the aortic cross-clamp. The hemodynamic parameters did not differ among the groups
throughout the study. After CPB, AaDO2 significantly increased (p < 0.05) in all groups. A significant decrease in AaDO2 was observed in aprotinin-treated patients at 24 hours after CPB compared with the other groups (p < 0.05). TNF-␣ level from peripheral arterial blood significantly increased in control patients 1 hour after CPB (p < 0.01) and did not significantly increase in methylprednisolone-treated patients throughout the study. In all groups, IL-6 levels increased after the release of the aortic cross-clamp and reached peak values 6 hours after CPB. At 6 hours after CPB, the increase in IL-6 levels in methylprednisolone-treated patients was significantly less compared with levels measured in control patients and aprotinin-treated patients (p < 0.001). In control patients, IL-8 levels significantly increased 2 minutes after the release of the aortic cross-clamp (p < 0.05), and peak values were observed 1 hour after CPB (p < 0.01). IL-8 levels in control patients were significantly higher compared with patients treated with aprotinin and patients treated with methylprednisolone 1 hour after CPB (p < 0.05). Conclusion: This study showed that methylprednisolone suppresses TNF-␣, IL-6, and IL-8 release; however, aprotinin attenuates IL-8 release alone. Methylprednisolone does not produce any additional positive hemodynamic and pulmonary effects. An improved postoperative AaDO2 was observed with the use of aprotinin. Copyright © 2001 by W.B. Saunders Company
T
operative hemodynamics in adult patients undergoing elective coronary artery bypass graft surgery.
HE SYSTEMIC inflammatory response during cardiopulmonary bypass (CPB) continues to be a significant cause of morbidity and an occasional cause of mortality. This systemic response may be caused by many processes, including blood–foreign surface interaction in the CPB circuit,1,2 the development of ischemia and reperfusion injury,3 and the presence of endotoxemia.4 These processes can result in the release of many inflammatory mediators, including tumor necrosis factor (TNF)-␣, interleukin (IL)-1, IL-6, and IL-8.5-7 It has been suggested that these inflammatory mediators may be responsible for postoperative organ dysfunction and morbidity.8-11 If pathway activation and cytokine release can be reduced during CPB, some of the adverse clinical consequences of CPB can be avoided. Many approaches have been suggested, including use of steroids,12,13 use of aprotinin,14 improvement of biocompatibility by heparin-coated CPB circuits,15,16 and ultrafiltration.17,18 Although much research has been reported on cytokine-reducing effects of steroids and aprotinin, the number of combined studies investigating the comparative effectiveness of these drugs is not sufficient.19,20 This prospective randomized study has 3 objectives: (1) to compare the efficacy of aprotinin and methylprednisolone in reducing CPB-induced cytokine release, through the use of a control group; (2) to evaluate the effect of myocardial cytokine release on systemic cytokine levels; and (3) to examine the role of aprotinin and methylprednisolone in perioperative and post-
KEY WORDS: aprotinin, methylprednisolone, cardiopulmonary bypass, cytokine
MATERIAL AND METHODS
After obtaining ethical committee approval and informed consent, 32 patients undergoing coronary artery bypass graft surgery were included in the study. Two patients were excluded because retrograde coronary sinus cannulation could not be performed. Patients undergoing a reoperation, had a myocardial infarction within 1 month, suffering from an uncontrolled systemic disease (diabetes mellitus, hypertension, or renal failure), or receiving long-term glucocorticoids were excluded. The use of aspirin, dipyridamole, and nonsteroidal anti-inflammatory drugs was discontinued 10 days before the surgery. The patients were randomized as follows: control patients (n ⫽ 10), aprotinin-treated patients (n ⫽ 10), and methylprednisolone-treated patients (n ⫽ 10). After the administration of an initial test dose for allergic response, aprotinin-treated pa-
From the Departments of Anesthesiology, Biochemistry, and Cardiovascular Surgery, I˙no¨nu¨ University Hospital, Malatya, Turkey. ¨ niversitesi Address reprint requests to Ayda Tu¨rko¨z, MD, I˙no¨nu¨ U Tıp Faku¨ltesi Anesteziyoloji AD, Malatya, Turkey. E-mail:rturkoz@ yahoo.com Copyright © 2001 by W.B. Saunders Company 1053-0770/01/1505-0014$35.00/0 doi:10.1053/jcan.2001.26539
Journal of Cardiothoracic and Vascular Anesthesia, Vol 15, No 5 (October), 2001: pp 603-610
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tients received a high-dose aprotinin (Trasylol) regimen (total dose 6 x 106 KIU).21 This regimen included an initial intravenous loading dose of 280 mg (2 ⫻ 106 KIU). An equivalent loading dose was added to the pump prime, and 70 mg/h (5 ⫻ 105 KIU) of constant intravenous infusion was administered during the operation. Methylprednisolone-treated patients received 30 mg/kg of methylprednisolone intravenously 5 minutes before CPB. After premedication with diazepam (0.2 mg/kg), anesthesia was induced with fentanyl, 10 g/kg; etomidate, 0.2 mg/kg; and thiopental, 2 mg/kg, followed by vecuronium, 0.1 mg/kg. Anesthesia was maintained with fentanyl, 20 g/kg. The patients were ventilated with a fraction of inspired oxygen of 0.5, and when necessary, isoflurane (0.2% to 0.5%) was added to the air-oxygen mixture. An intra-arterial catheter was placed in the right radial artery under local anesthesia. A pulmonary artery catheter (TD Thermodilution, Abbot Laboratories, Chicago, IL) was inserted into the right internal jugular vein after induction of anesthesia. Continuous monitoring of 2 electrocardiogram leads (II and modified V5), radial and pulmonary artery pressures, oxygen saturation, end-tidal carbon dioxide level, and rectal and esophageal temperatures was performed. After CPB, dobutamine and dopamine were provided when necessary. CPB was performed using a roller pump (Cobe Cardiovascular Inc, Arvada, CO), a hollow-fiber membrane oxygenator (Dideco D 708, Simplex, Mirandola, Italy), a polyvinylchloride tubing set, a 2-stage venous cannula, a venous reservoir (Univox IC, Baxter Healthcare Corp, Irvine, CA), and an arterial filter (Dideco D 734 Micro 40, Simplex, Mirandola, Italy). The circuit was primed with 2000 mL of Ringer’s lactate solution, 250 mL of mannitol, 1 g of cefazolin, and 2500 IU of heparin. A nonpulsatile flow of 2.4 L/min/m2 and mild hypothermia (with a rectal temperature of 33°C) were used. During CPB, hematocrit was maintained between 20% and 25%, and the mean arterial pressure was maintained between 50 and 70 mmHg (with sodium nitroprusside or phenylephrine administration as required). Anticoagulation was obtained by the administration of bovine lung heparin (300 IU/kg) just before the institution of CPB; additional doses were administered as required to maintain activated coagulation time ⬎750 seconds for aprotinin-treated patients and ⬎480 seconds for control patients and methylprednisolone-treated patients. After aortic cross-clamping, myocardial preservation was achieved by antegrade and retrograde administration of cold hyperkalemic blood cardioplegia (with a blood-to-crystalloid ratio of 4:1). Before the removal of the aortic cross-clamp, an additional bolus of warm cardioplegia was infused. Distal anastomoses were performed, the aortic cross-clamp was removed, and proximal anastomoses to the aorta were completed during the rewarming period. Extracorporeal circulation was terminated at a rectal temperature of 36°C. At the termination of CPB, 1.3 mg of protamine for every 100 U of total heparin dose was administered and confirmed by the return of activated coagulation time to baseline values. Shed mediastinal blood was not reinfused in any patient. The indication for transfusion was defined as a hematocrit level ⬍20% during CPB and ⬍25% in the postoperative period. Platelet concentrates were administered only in the case of a platelet count ⬍50,000/mm3.
All operations were performed by the same surgeon (R.T.) using a similar operative technique and the same perfusion protocol. Hemodynamic measurements (mean arterial pressure [MAP], mean pulmonary arterial pressure [MPAP], pulmonary capillary wedge pressure [PCWP], and thermodilution cardiac index [CI]) were obtained as follows: TH1, before CPB; TH2, after termination of CPB and administration of protamine; and TH3, 24 hours after CPB (in the intensive care unit). Pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) were calculated using standard formulae. Arterial blood samples were obtained from the radial artery catheter for blood gas measurements (Blood Gas System, Stat Profile 5, Nova Biomedical Waltham, MA). Alveolar-arterial PO2 difference (AaDO2) was calculated using the alveolar gas equation, assuming a respiratory quotient (RQ) of 0.8: PAO 2 ⫽ 共F I O 2 ⫻ 关PBatm ⫺ SVPH 2 O兴兲 ⫺ 共PACO 2 ⫻ 关F I O 2 ⫹ 共1 ⫺ FIO 2 ⲐRQ兲兴兲 where PAO2 is alveolar PO2, FIO2 is fraction of inspired oxygen, PBatm is barometric pressure, SVPH2O is saturated vapor pressure of water at 37°C, and PACO2 is alveolar PCO2, which is assumed to be equal to PaCO2. All measurements were performed with the patient anesthetized in the supine position. The measurement of AaDO2 was simultaneously performed with hemodynamic measurements. Blood samples (20 mL) were drawn from the radial artery catheter or, during CPB, the arterial port of the oxygenator as follows: TB1, immediately before the induction of anesthesia; TB2, 5 minutes before CPB; TB3, 3 minutes after the start of CPB; TB4, 2 minutes after the release of aortic cross-clamp; TB5, 1 hour after CPB; TB6, 6 hours after CPB; and TB7, 24 hours after CPB. Coronary sinus blood samples were obtained from the retrograde cardioplegia cannula at TCSB1, immediately before CPB, and TCSB2, 2 minutes after the release of aortic cross-clamp. Blood samples were centrifuged at 4°C with 3500 rpm for 20 minutes. Plasma was stored at ⫺40°C until assayed. The levels of TNF-␣, IL-1, IL-6, and IL-8 were determined by enzymelinked immunosorbent assay with Immulite kits (Diagnostic Products, Los Angeles, CA) according to the manufacturer’s instructions. The effects of aprotinin or methylprednisolone within the groups were evaluated by the Friedman rank analysis of variance. When the test results indicated significant differences within a group, the measurements were compared against the baseline data using the Wilcoxon matched pair test. The differences among the study groups were evaluated by the Kruskal-Wallis test, followed by the U-test, to detect the groups being actually different from each other. A p value ⬍ 0.05 was considered to be statistically significant. RESULTS
There were no statistically significant differences among the groups with regard to age, sex, body weight, ejection fraction, cross-clamp time, duration of CPB, lowest temperature, number of grafts, the amount of transfused packed red blood cells,
CYTOKINE GENERATION DURING CORONARY SURGERY
Table 1. Demographic and Clinical Characteristics of Patients Group A (n ⫽ 10)
Group MP (n ⫽ 10)
Group C (n ⫽ 10)
Age (y) 60.2 ⫾ 3.4 58.3 ⫾ 3.0 63.8 ⫾ 1.9 Sex (m/f) 9/1 8/2 9/1 Body weight (kg) 74.2 ⫾ 3.1 75.3 ⫾ 3.2 69.1 ⫾ 2.9 EF (%) 50.1 ⫾ 2 53.6 ⫾ 2.3 50.6 ⫾ 2.6 Cross-clamp duration (min) 70.2 ⫾ 4.2 68.2 ⫾ 4.0 68.6 ⫾ 3.7 CPB duration (min) 110.6 ⫾ 5.3 111.4 ⫾ 5.0 111.5 ⫾ 2.4 Lowest temperature (°C) 32.3 ⫾ 1.4 33.2 ⫾ 1.3 33.4 ⫾ 1.4 No. distal grafts (n) 3.6 ⫾ 0.5 3.4 ⫾ 0.2 3.3 ⫾ 0.2 Internal mammary artery (n) 9 10 10 Total heparin dose 32,000 ⫾ 4165*† 24,620 ⫾ 3368 21,530 ⫾ 2814 (103 U) Total protamine dose (mg) 409 ⫾ 54*† 303 ⫾ 43 283 ⫾ 33 Transfusion of PRBC (U) 1.9 ⫾ 0.5 2.1 ⫾ 0.8 2 ⫾ 0.9 Mediastinal tube drainage (mL) 510 ⫾ 44 600 ⫾ 55 680 ⫾ 58 NOTE. Values are mean ⫾ SD or number. Abbreviations: A, aprotinin; MP, methylprednisolone; C, control; EF, ejection fraction; CPB, cardiopulmonary bypass; PRBC, packed red blood cells. *p ⬍ 0.05 Group A v Group MP. †p ⬍ 0.05 Group A v Group C.
and the amount of mediastinal tube drainage. Total heparin dose and total protamine dose were higher in aprotinin-treated patients (Table 1). No patients required platelet transfusions. All patients had uncomplicated perioperative and postoperative recoveries. The principal hemodynamic parameters are summarized in Table 2. MAP was observed to decrease in all groups after CPB (p ⬍ 0.05), but there was no difference among the groups (Table 2). PCWP and SVR decreased similarly in all groups after CPB at TH2 and TH3 (p ⬍ 0.05). PVR increased similarly in all groups after CPB at TH2 and TH3 (p ⬍ 0.05). In all groups, MPAP and CI were not different after CPB at TH2 and TH3 (Table 2). AaDO2 significantly increased (p ⬍ 0.05) in all 3 groups after CPB at TH2. Although the increase was higher in control patients, there were no significant differences among the groups. A significant decrease in AaDO2 was found at 24 hours after CPB in aprotinin-treated patients compared with the other groups (p ⬍ 0.05) (Table 2). TNF-␣ level from the radial artery significantly increased in control patients at 1 hour after CPB (p ⬍ 0.01), and the increase was greater than in aprotinin-treated patients (p ⬍ 0.05) (Fig 1). TNF-␣ did not significantly increase in methylprednisolonetreated patients throughout the study (Table 3 and Fig 1). There was no statistically significant increase in coronary sinus blood levels of TNF-␣ after the release of the aortic cross-clamp in any of the groups (Table 3). No difference was observed for IL-1 level in radial artery and coronary sinus blood throughout the study in any of the
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Table 2. Perioperative and Postoperative Hemodynamic Data TH1
TH2
MAP (mmHg) Group A 99.2 ⫾ 2.9 84 ⫾ 3.1* Group MP 94.5 ⫾ 2.8 82.9 ⫾ 2.3* Group C 93.1 ⫾ 2.3 81.4 ⫾ 3.7* MPAP (mmHg) Group A 20.5 ⫾ 0.9 18.7 ⫾ 1.4 Group MP 19.3 ⫾ 1.3 19.8 ⫾ 1.7 Group C 20.1 ⫾ 2.1 20.2 ⫾ 1.4 PCWP (mmHg) Group A 16.8 ⫾ 0.9 13.1 ⫾ 3.7* Group MP 15.9 ⫾ 0.9 13 ⫾ 1.9* Group C 16 ⫾ 1.7 13.8 ⫾ 1.4* CI (L/min/m2) Group A 2.5 ⫾ 0.2 2.7 ⫾ 0.2 Group MP 2.6 ⫾ 0.1 3.1 ⫾ 0.2 Group C 2.6 ⫾ 0.1 3.1 ⫾ 0.1 SVR (dyne 䡠 sec 䡠 cm⫺5) Group A 1862 ⫾ 134 1501 ⫾ 120* Group MP 1688 ⫾ 136 1355 ⫾ 129* Group C 1678 ⫾ 105 1300 ⫾ 159* PVR (dyne 䡠 sec 䡠 cm⫺5) Group A 69.6 ⫾ 8.9 97.6 ⫾ 7.6* Group MP 58.1 ⫾ 7.5 97.4 ⫾ 12.8* Group C 74.2 ⫾ 10.7 91.9 ⫾ 11.3* AaDO2 (mmHg) Group A 79.5 ⫾ 24.6 135.4 ⫾ 9.6* Group MP 78 ⫾ 31.5 143.5 ⫾ 19.3* Group C 76 ⫾ 20.3 165 ⫾ 16.8*
TH3
87.7 ⫾ 2.4 86.3 ⫾ 4.5 85.9 ⫾ 3.0 18.4 ⫾ 1.2 18.5 ⫾ 1.3 18.9 ⫾ 1.8 11.9 ⫾ 0.9* 12 ⫾ 1.2* 12.4 ⫾ 1.3* 3.0 ⫾ 0.0 3.2 ⫾ 0.0 3.2 ⫾ 0.0 1423 ⫾ 100* 1330 ⫾ 104* 1360 ⫾ 75* 101.9 ⫾ 12.8* 90.2 ⫾ 11* 95.5 ⫾ 14.8* 87.2 ⫾ 16.7†‡ 128.6 ⫾ 2.5* 117.4 ⫾ 1.6*
NOTE. Values are mean ⫾ SD. Abbreviations: TH1, before cardiopulmonary bypass (CPB); TH2, after cessation of CPB and administration of protamine; TH3, 24 hours after CPB; A, aprotinin; MP, methylprednisolone; C, control; MAP, mean arterial pressure; MPAP, mean pulmonary arterial pressure; PCWP, pulmonary capillary wedge pressure; CI, cardiac index; SVR, systemic vascular resistance; PVR, pulmonary vascular resistance; AaDO2, alveolar-arterial PO2 gradient. *p ⬍ 0.05 v TH1. †p ⬍ 0.05 Group A v Group MP. ‡p ⬍ 0.05 Group A v Group C.
Fig 1. Tumor necrosis factor (TNF)-␣ levels. Aprotinin group (}); methylprednisolone group (■); control group (Œ). *p < 0.05 versus TB1. **p < 0.01 versus TB1. †p < 0.05 between aprotinin and control group. ‡p < 0.05 between methylprednisolone and control group. #p < 0.05 between aprotinin and methylprednisolone group. See text for explanation of abbreviations.
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Table 3. Cytokine Levels (pg/mL) TB1
TNF-␣ Group Group Group IL-1 Group Group Group IL-6 Group Group Group IL-8 Group Group Group
TB2
TB3
TB4
TB5
TB6
A MP C
7.7 ⫾ 0.5 8.2 ⫾ 1 9.6 ⫾ 0.3
11.4 ⫾ 1.9 8.2 ⫾ 1.2 10.1 ⫾ 0.8
12.4 ⫾ 4 10.1 ⫾ 2.5 10.6 ⫾ 1.2
12.7 ⫾ 2.5 10 ⫾ 2.4 13 ⫾ 1.1
*14 ⫾ 1.8† 10 ⫾ 1.4‡ **30 ⫾ 6.3
*18.1 ⫾ 4.3# 9.5 ⫾ 1.6‡ *16.2 ⫾ 1.7
A MP C
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 6.3 ⫾ 1.4
8.8 ⫾ 6.6 7.8 ⫾ 5.9 6.1 ⫾ 1.2
A MP C
7.7 ⫾ 1.3 8.1 ⫾ 1.3 10.5 ⫾ 3.1
10.2 ⫾ 2.8 12.7 ⫾ 2.3 9.6 ⫾ 2.2
A MP C
17.7 ⫾ 4.5 12.2 ⫾ 4 9.6 ⫾ 1.3
15 ⫾ 3.7 9.8 ⫾ 2 8.4 ⫾ 1
11.8 ⫾ 1.8 *15.6 ⫾ 3.1‡† ***250 ⫾ 38# ****704 ⫾ 89• 13.3 ⫾ 10 **29.4 ⫾ 8.5‡ ***122 ⫾ 29¶ ***148 ⫾ 34¶ 12.9 ⫾ 2.7 **80.4 ⫾ 23 ****522 ⫾ 10 ****671 ⫾ 82 18 ⫾ 9.2 7.0 ⫾ 0.9 6.1 ⫾ 0.8
17.8 ⫾ 5.5 *29.5 ⫾ 16 *22.3 ⫾ 9.7
*35.8 ⫾ 26† *35.8 ⫾ 9.6‡ ****114.5 ⫾ 3.1
**63.6 ⫾ 14 **49.8 ⫾ 18 ***83 ⫾ 22
TB7
TCSB1
TCSB2
*15.6 ⫾ 2.7 11.9 ⫾ 2.5 12.3 ⫾ 1.3
10.1 ⫾ 5 11.3 ⫾ 2 16 ⫾ 4.4
11.5 ⫾ 3 8.5 ⫾ 3 19 ⫾ 7.2
5.0 ⫾ 0.1 5.0 ⫾ 0.1 4.9 ⫾ 0.0
4.9 ⫾ 0.1 4.9 ⫾ 0.1 4.9 ⫾ 0.0
4.9 ⫾ 0.1 5.5 ⫾ 0.1 4.9 ⫾ 0.0
***437 ⫾ 107• **65.8 ⫾ 14¶ ***279 ⫾ 46
16.4 ⫾ 7.4 25.9 ⫾ 11 14.7 ⫾ 5.9
15.4 ⫾ 3.6 37.3 ⫾ 7.3 *77 ⫾ 39
**46.2 ⫾ 7.6 *32.0 ⫾ 11‡ ***48.9 ⫾ 9.4
14.8 ⫾ 4.9 17.1 ⫾ 5 11.3 ⫾ 0.8
20.2 ⫾ 6.7 20.2 ⫾ 7.9 *20 ⫾ 4.7
NOTE. Values are mean ⫾ SD. Abbreviations: TB1, immediately before the induction of anesthesia; TB2, 5 minutes before cardiopulmonary bypass (CPB); TB3, at 3 minutes on CPB; TB4, 2 minutes after release of the aortic cross-clamp; TB5, 1 hour after CPB; TB6, 6 hours after CPB; TB7, 24 hours after CPB; TCSB1, coronary sinus blood samples immediately before CPB; TCSB2, 2 minutes after release of the aorta cross-clamp; A, aprotinin; MP, methylprednisolone; C, control; TNF, tumor necrosis factor; IL, interleukin. *p ⬍ 0.05 v baseline. **p ⬍ 0.01 v baseline. ***p ⬍ 0.005 v baseline. ****p ⬍ 0.001 v baseline. †p ⬍ 0.05 (group A v group C). ‡p ⬍ 0.05 (group MP v group C). #p ⬍ 0.05 (group A v group MP). ‡†p ⬍ 0.01 (group A v group C). •p ⬍ 0.005 (group A v group MP). ¶p ⬍ 0.005 (group MP v group C).
groups (Table 3). In all groups, plasma IL-6 levels were low before and at 3 minutes on CPB (Table 3 and Fig 2). IL-6 levels were elevated after the release of the aortic cross-clamp in all groups. IL-6 levels continued to increase at 1 hour and 6 hours
Fig 2. Interleukin (IL)-6 levels. Aprotinin group (}); methylprednisolone group (■); control group (Œ). *p < 0.05 versus TB1. **p < 0.01 versus TB1. ***p < 0.005 versus TB1. ****p < 0.001 versus TB1. ‡p < 0.05 between methylprednisolone and control group. ††p < 0.01 between aprotinin and control group. #p < 0.05 between aprotinin and methylprednisolone group. ¶p < 0.005 between methylprednisolone and control group. ●p < 0.005 between aprotinin and methylprednisolone group. See text for explanation of abbreviations.
after CPB and peaked at 6 hours after CPB. IL-6 levels decreased at 24 hours after CPB but remained above baseline levels in all groups. The elevation of IL-6 levels in methylprednisolone-treated patients was significantly less compared with control patients at 1 hour after CPB (p ⬍ 0.001). The increase in IL-6 levels in aprotinin-treated patients was less compared with control patients (p ⬍ 0.05); however, the difference was less pronounced when compared with methylprednisolone-treated patients. At 1 hour and at 6 hours after CPB, the increases in IL-6 levels in methylprednisolone-treated patients were significantly less compared with the other groups (p ⬍ 0.001). In coronary sinus blood, IL-6 levels increased only in control patients after the release of the aortic cross-clamp (p ⬍ 0.05), but the level was not different from the radial artery samples obtained at the same time period (Table 3). IL-8 levels were similar before and at 3 minutes on CPB in all groups (Table 3 and Fig 3). In control patients, IL-8 levels significantly increased at 2 minutes after the release of the aortic cross-clamp (p ⬍ 0.05), and the increase peaked at 1 hour after CPB (p ⬍ 0.001). IL-8 levels in control patients were significantly higher compared with aprotinin-treated patients and methylprednisolone-treated patients at 1 hour after CPB (p ⬍ 0.05). At 6 hours after CPB, IL-8 levels remained above baseline levels in all groups. The elevation was less pronounced in methylprednisolone-treated patients and aprotinin-treated
CYTOKINE GENERATION DURING CORONARY SURGERY
Fig 3. Interleukin (IL)-8 levels. Aprotinin group (}); methylprednisolone group (■); control group (Œ). *p < 0.05 versus TB1. **p < 0.01 versus TB1. ***p < 0.005 versus TB1. ****p < 0.001 versus TB1. †p < 0.05 between aprotinin and control group. ‡p < 0.05 between methylprednisolone and control group. See text for explanation of abbreviations.
patients (p ⬍ 0.01) compared with control patients (p ⬍ 0.001). IL-8 level in methylprednisolone-treated patients was significantly different from that in control patients at 24 hours after CPB (p ⬍ 0.05). In coronary sinus blood, IL-8 levels increased in all groups, but the increase was significant only in control patients after the release of the aortic cross-clamp (p ⬍ 0.05) (Table 3). IL-8 levels in coronary sinus blood were not different from the radial artery samples obtained at the same time period. DISCUSSION
This study focuses on systemic and myocardial cytokine release after CPB. The effects of aprotinin and methylprednisolone in reducing the levels of proinflammatory cytokines and the effects of cytokine release on hemodynamic parameters have been investigated. The major findings of the study can be summarized as follows: (1) An increase in TNF-␣ levels was observed after CPB, and this increase was inhibited only by methylprednisolone; (2) an increase in IL-6 levels was observed after the release of the aortic cross-clamp, which peaked 6 hours after CPB and was reduced only with the use of methylprednisolone; (3) IL-8 release peaked 1 hour after CPB, and aprotinin and methylprednisolone suppressed the increase in IL-8 levels, but the suppression was more prominent with methylprednisolone at 24 hours after CPB; and (4) the suppression of cytokine release with the use of aprotinin and methylprednisolone did not directly influence the hemodynamic parameters. Cytokines, a group of low-molecular-weight polypeptides functioning as intercellular communication molecules, have a central role in inflammatory reactions, particularly acting on the heart, lung, liver, coagulation system, and central nervous system, subsequently causing damaging effects.9-11,22-26 Many clinical studies have shown significant increases in blood cytokine levels during and after CPB.5-7,27,28 Alterations in cytokine levels after CPB gathered from various studies are summarized in Table 4. The most widely studied proinflammatory cytokines are TNF-␣, IL-1, IL-6, and IL-8. TNF-␣ contributes to myocardial dysfunction and hemodynamic instability after CPB.23,28,29 In some studies, TNF-␣ has been detected in
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plasma after CPB,30-32 but not in others.5,33,34 The short half-life of TNF-␣ and the differences between the methods of cytokine measurement may explain the discrepancies among the results presented in various studies. The absence of detectable circulating cytokines does not rule out a likely local production by the activated cells.35 The activation pattern of TNF-␣ has been shown to be dependent on the body core temperature during CPB.28 Patients operated with warm CPB have a significantly higher release of TNF-␣.28 In the present study, TNF-␣ levels peaked only in the control patients at 1 hour after CPB. Methylprednisolone completely inhibited the increase in TNF-␣ levels, but with aprotinin the levels were slightly attenuated. The use of tepid temperature (33°C) during CPB might have triggered TNF-␣ release in the control patients. IL-1 is mostly located intracellularly, and the appearance of IL-1 in the circulation is likely a reflection of tissue destruction.36 Various studies have reported different levels of IL-1 increase during and after CPB.28,37-41 IL-1 production has been found to correlate with the maximum postoperative temperature rise.28 In many studies, IL-1 has not been detected in plasma after hypothermic CPB.5-7,41,42 Patients operated with normothermic CPB have a significantly higher release of IL1.28 In the present study, a significant increase in circulating IL-1 levels was not observed after tepid CPB in any group. IL-6 is one of the key mediators in acute-phase response43 and is synthesized by a variety of cells, including endothelial cells and leukocytes.2,6,44 Significantly increased levels of IL-6 have been found in patients after CPB.3,13,16-18,28,39,40,42 IL-6 levels are higher in patients with complications after cardiac surgery.23 The hemodynamic effects of IL-6 are controversial. In 1 study, IL-6 administration in dogs had no acute hemodynamic effects,45 whereas in another study, cytokine-stimulated nitric oxide production was found to be responsible for the reversible myocardial depression.22 Elevated systemic levels of IL-6 have been observed in patients with congestive heart
Table 4. Cytokine Levels After Cardiopulmonary Bypass
al5
Butler et Finn et al7 Jansen et al12 Kawamura et al13 Weerwind et al16 Hill et al19 Diego et al20 Hennein et al23 Wan et al27 Menasche´ et al28 Velthuies et al29 Teoh et al30 Jansen et al31 Frering et al33 Engelman et al37 Deng et al41 Butler et al42 Ashraf et al50 Liebold et al52
TNF-␣
IL-1
NC NC 1
NC
NC 1 1 1 1/1 1 1 1 NC 1 NC
NC/1
NC 1 NC
IL-6
IL-8
1 1 1
1 1
1 1 1 1/1
1 1
1
1
1
1 1
1 1 1/1 1
Temperature (°C)
32-34 16-32 28-30 28 32 32 26-28 30 28-30/35-37 28-30 36-37 28-30 36.5 37 37 30-34 18/26-28 32-34
Abbreviations: TNF, tumor necrosis factor; IL, interleukin; NC, no change.
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failure and have been correlated with prognosis.46,47 In the present study, IL-6 levels increased after the release of the aortic cross-clamp. The increase continued at 1 hour after CPB and peaked at 6 hours after CPB. IL-6 levels remained elevated at 24 hours in all groups. Aprotinin did not attenuate the increase in IL-6 levels, but it delayed the increase during the early period of CPB. The administration of methylprednisolone before CPB significantly inhibited the release of IL-6. IL-8, predominantly produced by macrophages, fibroblasts, neutrophils, and endothelial cells, is a potent chemoattractant for neutrophils, controlling their trafficking.33 CPB-induced lung injury is thought to be related to pulmonary leukocyte sequestration. Ratliff et al48 found no severe endothelial damage in the absence of large numbers of polymorphonuclear leukocytes. Subsequent infiltration of neutrophils into the perivascular tissue resulted in the release of oxygen-derived free radicals, proteases, and elastases, leading to increased capillary permeability and nonspecific cellular damage.49 Ashraf et al50 showed a positive correlation between prolonged intubation and IL-8 concentrations in pediatric patients undergoing cardiac surgery. This pathologic process may lead to postoperative respiratory dysfunction and multisystem organ failure. In the present study, methylprednisolone and aprotinin suppressed the increase in IL-8 levels compared with the control group. The suppression was slightly more pronounced with the use of methylprednisolone. Numerous clinical studies have attempted to find the source of proinflammatory cytokines released during and after CPB.23,24,51,52 Some studies concluded myocardium to be the main source of proinflammatory cytokines during CPB, whereas others reported no significant difference between coronary sinus and systemic arterial blood proinflammatory cytokine levels during the early period after CPB. The present study did not find any significant difference between coronary sinus and systemic arterial blood levels. One of the limitations of the present study as well as the other studies that have been unable to find any difference is, however, that coronary sinus blood sampling was concluded immediately after CPB, despite the fact that all cytokines reached peak levels at 1 or 6 hours after CPB. Cytokine release has been found to significantly correlate with the duration of ischemia after cardiac transplantation and coronary artery bypass graft surgery.27 The cardiac release of the cytokines significantly increased with reperfusion after longer ischemic periods or acute myocardial infarction.27,53 TNF-␣, IL-1, IL-6, and IL-8 levels have been found to be increased during CPB, and the release of these cytokines has been proposed to contribute to the development of postoperative organ dysfunction and multiple organ failure.8-11 Several studies have examined a variety of strategies to diminish the release of proinflammatory cytokines, including use of corticosteroids, aprotinin, adenosine, pentoxifylline, heparin-coated
CPB circuits, ultrafiltration, and warm versus cold CPB and the modification of surgical techniques (off-pump surgery).54 The administration of steroids before CPB has been used during cardiac surgery since the 1970s. The exact mechanism of action of steroids during CPB is not completely understood. Studies have focused on the inhibition of the release of proinflammatory cytokines, including TNF-␣, IL-1, IL-6, and IL-8.12,13,19,20,30,37,40 Steroids also increase the production of an anti-inflammatory cytokine, IL-10.54 Aprotinin, a known protease inhibitor, is primarily used to improve hemostasis after CPB. Aprotinin has been shown to reduce the inflammatory response characterized by TNF-␣ and IL-6 release14,19,20 and to prevent the upregulation of neutrophil CD11b integrin expression after CPB.19 Aprotinin decreases neutrophil activation and the level of IL-8 in bronchial lavage fluid when compared with placebo.55 In simulated bypass, Wachtfogel et al56 showed that high-dose aprotinin may completely inhibit kallikrein activation, partially inhibit neutrophil activation, and decrease platelet activation. The present study has shown that methylprednisolone exhibits more inhibitory effects on cytokine levels than aprotinin after CPB. The administration of methylprednisolone has not been associated with additional positive hemodynamic effects after CPB, however, compared with the control group. The use of aprotinin, inhibiting only the release of IL-8, has significantly lowered AaDO2 compared with the methylprednisolone group. The protective effects of aprotinin on the lungs have been shown in studies. In the authors’ belief, these effects are not only related to the proinflammatory cytokines, but also to some other mechanisms. In the present study, the lack of any clinical alterations despite the suppression of cytokine levels after methylprednisolone administration was a striking observation. This observation can be explained in part by the facts that the patients included in the study were low risk based on their preoperative cardiac and pulmonary function and that the number of patients included in the study was relatively low. Despite the suppression in cytokine release after methylprednisolone administration in the control group, a 15-fold increase in IL-6 levels and a 3-fold increase in IL-8 levels at 6 hours after CPB in the methylprednisolone group might indicate that methylprednisolone does not lead to adequate suppression. In conclusion, the present study has shown that methylprednisolone suppresses most of the cytokines released, including TNF-␣, IL-6, and IL-8. Aprotinin attenuates only IL-8 release, however. Methylprednisolone does not produce any additional positive hemodynamic and pulmonary effects. An improvement in postoperative lung function in terms of AaDO2 has been observed with the use of aprotinin. Further studies are required to assess the ideal pharmacologic strategies to reduce the effects of cytokines on inflammatory response and the subsequent damaging effects after CPB.
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3. Sawa Y, Shimazaki Y, Kadoba K, et al: Attenuation of cardiopulmonary bypass-derived inflammatory reactions reduced myocardial reperfusion injury in cardiac operations. J Thorac Cardiovasc Surg 111:29-35, 1996 4. Kharazmi A, Andersen LW, Baek L, et al: Endotoxemia and enhanced generation of oxygen radicals by neutrophils from patients
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undergoing cardiopulmonary bypass. J Thorac Cardiovasc Surg 98: 381-385, 1989 5. Butler J, Pillai R, Rocker GM, et al: Effect of cardiopulmonary bypass on systemic release of neutrophil elastase and tumor necrosis factor. J Thorac Cardiovasc Surg 105:25-30, 1993 6. Kawamura T, Wakusawa R, Okada K, Inada S: Elevation of cytokines during open heart surgery with cardiopulmonary bypass: Participation of interleukin 8 and 6 in reperfusion injury. Can J Anaesth 40:1016-1021, 1993 7. Finn A, Naik S, Klein N, et al: Interleukin-8 release and neutrophil degranulation after pediatric cardiopulmonary bypass. J Thorac Cardiovasc Surg 105:234-241, 1993 8. Hashimoto K, Miyamoto H, Suziki K, et al: Evidence of organ damage after cardiopulmonary bypass. J Thorac Cardiovasc Surg 104: 666-673, 1993 9. Roumen R, Redl H, Schlag G, et al: Inflammatory mediators in relation to the development of multiple organ failure in patients after severe blunt trauma. Crit Care Med 23:474-480, 1995 10. Donnelly S, MacGregor I, Zamani A, et al: Plasma elastase levels and the development of the adult respiratory distress syndrome. Am J Respir Crit Care Med 151:1428-1433, 1995 11. Marty C, Misset B, Tamion F, et al: Circulating interleukin-8 concentrations with multiple organ failure of septic and nonseptic origin. Crit Care Med 22:673-679, 1994 12. Jansen NJG, van Oeveren W, van den Broek L, et al: Inhibition by dexamethasone of the reperfusion phenomena in cardiopulmonary bypass. J Thorac Cardiovasc Surg 102:515-525, 1991 13. Kawamura T, Inada K, Okada H, et al: Methylprednisolone inhibits increase of interleukin 8 and 6 during open heart surgery. Can J Anaesth 42:399-403, 1995 14. Whitten CW, Latson TW, Allison PM: Does aprotinin inhibit cardiopulmonary bypass-induced inflammation? Anesthesiology 77: A266, 1992 15. Schreurs HH, Wijers MJ, Gu YJ, et al: Heparin-coated bypass circuits: Effects on inflammatory response in pediatric cardiac operations. Ann Thorac Surg 66:166-171, 1998 16. Weerwind PW, Maessen JG, van Tits LJH, et al: Influence of Duraflo II heparin-treated extracorporeal circuits on the systemic inflammatory response in patients having coronary bypass. J Thorac Cardiovasc Surg 110:1633-1641, 1995 17. Journois D, Pouard P, Greeley WJ, et al: Hemofiltration during cardiopulmonary bypass in pediatric cardiac surgery: Effects on hemostasis, cytokines, and complement components. Anesthesiology 81: 1181-1189, 1994 18. Millar AB, Armstrong L, van der Linden, et al: Cytokine production and hemofiltration in children undergoing cardiopulmonary bypass. Ann Thorac Surg 56:1499-1502, 1993 19. Hill GE, Alonso A, Spurzem JR, et al: Aprotinin and methylprednisolone equally blunt cardiopulmonary bypass-induced inflammation in humans. J Thorac Cardiovasc Surg 110:1658-1662, 1995 20. Diego RP, Mihalakakos PJ, Hexum TD, Hill GE: Methylprednisolone and full-dose aprotinin reduce reperfusion injury after cardiopulmonary bypass. J Cardiothorac Vasc Anesth 11:29-31, 1997 21. Dietrich W, Spannagl M, Jochum M, et al: Influence of highdose aprotinin treatment on blood loss and coagulation pattern in patients undergoing myocardial revascularization. Anesthesiology 73: 1119-1126, 1990 22. Finkel MS, Oddis CV, Jacob TD, et al: Negative inotropic effects of cytokines on the heart mediated by nitric oxide. Science 257:387-389, 1992 23. Hennein HA, Ebba H, Rodriguez JL, et al: Relationship of the proinflammatory cytokines to myocardial ischemia and dysfunction
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after uncomplicated coronary revascularization. J Thorac Cardiovasc Surg 108:626-635, 1994 24. Sawa Y, Ichikawa H, Kagisaki K, et al: Interleukin-6 derived from hypoxic myocytes promotes neutrophil-mediated reperfusion injury in myocardium. J Thorac Cardiovasc Surg 116:511-517, 1998 25. Stadler J, Bentz BG, Harbrecht BG, et al: Tumor necrosis factor alpha inhibits hepatocyte mitochondrial respiration. Ann Surg 216:539546, 1992 26. Schorer AE, Moldow CF, Rick ME: Interleukin 1 or endotoxin increases the release of von Willebrand factor from human endothelial cells. Br J Haematol 67:193-197, 1987 27. Wan S, Marchant A, DeSmet JM, et al: Human cytokine responses to cardiac transplantation and coronary artery bypass grafting. J Thorac Cardiovasc Surg 111:469-477, 1996 28. Menasche´ P, Haydar S, Peynet J, et al: A potential mechanism of vasodilatation after warm heart surgery: The temperature-dependent release of cytokines. J Thorac Cardiovasc Surg 107:293-299, 1994 29. te Velthuies H, Jansen PGM, Oudemans-van Straaten HM, et al: Myocardial performance in elderly patients after cardiopulmonary bypass is suppressed by tumor necrosis factor. J Thorac Cardiovasc Surg 110:1663-1669, 1995 30. Teoh KHT, Bradley CA, Gauldie J, Burrows H: Steroid inhibition of cytokine-mediated vasodilation after warm heart surgery. Circulation 92:II347-II353, 1995 (suppl II) 31. Jansen NJG, van Oeveren W, Gu YJ, et al: Endotoxin release and tumor necrosis factor formation during cardiopulmonary bypass. Ann Thorac Surg 54:744-748, 1992 32. Tonz M, Mihaljevic T, von Segesser LK, et al: Normothermia versus hypothermia during cardiopulmonary bypass: A randomized, controlled trial. Ann Thorac Surg 59:137-143, 1995 33. Frering B, Philip I, Dehoux M, et al: Circulating cytokines in patients undergoing normothermic cardiopulmonary bypass. J Thorac Cardiovasc Surg 108:636-641, 1994 34. George JF: Invited letter concerning: Cytokines and mechanisms of capillary leakage after cardiopulmonary bypass. J Thorac Cardiovasc Surg 106:566-567, 1993 35. Cavaillon JM, Munoz C, Fitting C, et al: Circulating cytokines: The tip of the iceberg? Circ Shock 38:145-152, 1992 36. Matsushima K, Taguchi M, Kovacs EJ, et al: Intracellular localization of human monocyte associated interleukin 1 (IL 1) activity and release of biologically active IL 1 from monocytes by trypsin and plasmin. J Immunol 136:2883-2891, 1986 37. Engelman RM, Rousou JA, Flack JE 3rd, et al: Influence of steroids on complement and cytokine generation after cardiopulmonary bypass. Ann Thorac Surg 60:801-804, 1995 38. Markewitz A, Faist E, Lang S, et al: Successful restoration of cell-mediated immune response after cardiopulmonary bypass by immunomodulation. J Thorac Cardiovasc Surg 105:15-24, 1993 39. Martinez-Pellus AE, Merino P, Bru M, et al: Can selective digestive decontamination avoid the endotoxemia and cytokine activation promoted by the cardiopulmonary bypass? Crit Care Med 21:16841691, 1993 40. Inaba H, Kochi A, Yorozu S: Suppression by methylprednisolone of augmented plasma endotoxin-like activity and interleukin-6 during cardiopulmonary bypass. Br J Anaesth 72:348-350, 1994 41. Deng MC, Wiedner M, Erren M, et al: Arterial and venous cytokine response to cardiopulmonary bypass for low risk CABG and relation to hemodynamics. Eur J Cardiothorac Surg 9:22-29, 1995 42. Butler J, Chong GL, Bailgrie RJ, et al: Cytokine responses to cardiopulmonary bypass with membrane and bubble oxygenation. Ann Thorac Surg 53:833-838, 1992 43. Nijsten MW, de Groot ER, ten Duis HJ, et al: Serum levels of interleukin 6 and acute phase responses. Lancet 2:921, 1987
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44. Lotz M: Interleukin-6: A comprehensive review. Cancer Treat Res 80:209-233, 1995 45. Preiser JC, Schmartz D, van der Linden P, et al: Interleukin-6 administration has no acute hemodynamic or hematologic effect in the dog. Cytokine 3:1-4, 1991 46. Tsutamoto T, Hisanaga T, Wada A, et al: Interleukin-6 spillover in the peripheral circulation increases with the severity of heart failure, and the high plasma level of IL-6 is an important prognostic predictor in patients with congestive heart failure. J Am Coll Cardiol 31:391-398, 1998 47. Lommi J, Koskinen P, Naveri H, et al: Haemodynamic, neuroendocrine and metabolic correlates of circulating cytokine concentrations in congestive heart failure. Eur Heart J 18:1620-1625, 1997 48. Ratliff NB, Young WG Jr, Hackel DB, et al: Pulmonary injury secondary to extracorporeal circulation: An ultrastructural study. J Thorac Cardiovasc Surg 65:425-432, 1973 49. Boyle EM, Pohlman TH, Cornejo CL, Verrier ED: Endothelial cell injury in cardiovascular surgery: Ischemia-reperfusion. Ann Thorac Surg 62:1868-1875, 1996 50. Ashraf S, Bhattacharya K, Tian Y, Watterson K: Cytokine and S100B levels in pediatric patients undergoing corrective cardiac sur-
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gery with or without total circulatory arrest. Eur J Cardiothorac Surg 16:32-37, 1999 51. Wan S, DeSmet JM, Barvais L, et al: Myocardium is a major source of proinflammatory cytokines in patients undergoing cardiopulmonary bypass. J Thorac Cardiovasc Surg 112:806-811, 1996 52. Liebold A, Keyl C, Birnbaum DE: The heart produces but the lungs consume proinflammatory cytokines following cardiopulmonary bypass. Eur J Cardiothorac Surg 15:340-345, 1999 53. Neumann FJ, Ott I, Gawaz M, et al: Cardiac release of cytokines and inflammatory responses in acute myocardial infarction. Circulation 92:748-755, 1995 54. Hall RI, Smith MS, Rocker G: The systemic inflammatory response to cardiopulmonary bypass: Pathophysiological, therapeutic, and pharmacological considerations. Anesth Analg 85:766-782, 1997 55. Hill GE, Pohorecki R, Alonso A, et al: Aprotinin reduces interleukin-8 production and lung neutrophil accumulation after cardiopulmonary bypass. Anesth Analg 83:696-700, 1996 56. Wachtfogel YT, Kucich U, Hack CE, et al: Aprotinin inhibits the contact, neutrophil, and platelet activation systems during simulated extracorporeal perfusion. J Thorac Cardiovasc Surg 106:1-9, 1993
throughout the study. After CPB, AaDO2 significantly increased (p < 0.05) in all groups. A significant decrease in AaDO2 was observed in aprotinin-treated patients at 24 hours after CPB compared with the other groups (p < 0.05). TNF-␣ level from peripheral arterial blood significantly increased in control patients 1 hour after CPB (p < 0.01) and did not significantly increase in methylprednisolone-treated patients throughout the study. In all groups, IL-6 levels increased after the release of the aortic cross-clamp and reached peak values 6 hours after CPB. At 6 hours after CPB, the increase in IL-6 levels in methylprednisolone-treated patients was significantly less compared with levels measured in control patients and aprotinin-treated patients (p < 0.001). In control patients, IL-8 levels significantly increased 2 minutes after the release of the aortic cross-clamp (p < 0.05), and peak values were observed 1 hour after CPB (p < 0.01). IL-8 levels in control patients were significantly higher compared with patients treated with aprotinin and patients treated with methylprednisolone 1 hour after CPB (p < 0.05). Conclusion: This study showed that methylprednisolone suppresses TNF-␣, IL-6, and IL-8 release; however, aprotinin attenuates IL-8 release alone. Methylprednisolone does not produce any additional positive hemodynamic and pulmonary effects. An improved postoperative AaDO2 was observed with the use of aprotinin. Copyright © 2001 by W.B. Saunders Company
T
operative hemodynamics in adult patients undergoing elective coronary artery bypass graft surgery.
HE SYSTEMIC inflammatory response during cardiopulmonary bypass (CPB) continues to be a significant cause of morbidity and an occasional cause of mortality. This systemic response may be caused by many processes, including blood–foreign surface interaction in the CPB circuit,1,2 the development of ischemia and reperfusion injury,3 and the presence of endotoxemia.4 These processes can result in the release of many inflammatory mediators, including tumor necrosis factor (TNF)-␣, interleukin (IL)-1, IL-6, and IL-8.5-7 It has been suggested that these inflammatory mediators may be responsible for postoperative organ dysfunction and morbidity.8-11 If pathway activation and cytokine release can be reduced during CPB, some of the adverse clinical consequences of CPB can be avoided. Many approaches have been suggested, including use of steroids,12,13 use of aprotinin,14 improvement of biocompatibility by heparin-coated CPB circuits,15,16 and ultrafiltration.17,18 Although much research has been reported on cytokine-reducing effects of steroids and aprotinin, the number of combined studies investigating the comparative effectiveness of these drugs is not sufficient.19,20 This prospective randomized study has 3 objectives: (1) to compare the efficacy of aprotinin and methylprednisolone in reducing CPB-induced cytokine release, through the use of a control group; (2) to evaluate the effect of myocardial cytokine release on systemic cytokine levels; and (3) to examine the role of aprotinin and methylprednisolone in perioperative and post-
KEY WORDS: aprotinin, methylprednisolone, cardiopulmonary bypass, cytokine
MATERIAL AND METHODS
After obtaining ethical committee approval and informed consent, 32 patients undergoing coronary artery bypass graft surgery were included in the study. Two patients were excluded because retrograde coronary sinus cannulation could not be performed. Patients undergoing a reoperation, had a myocardial infarction within 1 month, suffering from an uncontrolled systemic disease (diabetes mellitus, hypertension, or renal failure), or receiving long-term glucocorticoids were excluded. The use of aspirin, dipyridamole, and nonsteroidal anti-inflammatory drugs was discontinued 10 days before the surgery. The patients were randomized as follows: control patients (n ⫽ 10), aprotinin-treated patients (n ⫽ 10), and methylprednisolone-treated patients (n ⫽ 10). After the administration of an initial test dose for allergic response, aprotinin-treated pa-
From the Departments of Anesthesiology, Biochemistry, and Cardiovascular Surgery, I˙no¨nu¨ University Hospital, Malatya, Turkey. ¨ niversitesi Address reprint requests to Ayda Tu¨rko¨z, MD, I˙no¨nu¨ U Tıp Faku¨ltesi Anesteziyoloji AD, Malatya, Turkey. E-mail:rturkoz@ yahoo.com Copyright © 2001 by W.B. Saunders Company 1053-0770/01/1505-0014$35.00/0 doi:10.1053/jcan.2001.26539
Journal of Cardiothoracic and Vascular Anesthesia, Vol 15, No 5 (October), 2001: pp 603-610
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tients received a high-dose aprotinin (Trasylol) regimen (total dose 6 x 106 KIU).21 This regimen included an initial intravenous loading dose of 280 mg (2 ⫻ 106 KIU). An equivalent loading dose was added to the pump prime, and 70 mg/h (5 ⫻ 105 KIU) of constant intravenous infusion was administered during the operation. Methylprednisolone-treated patients received 30 mg/kg of methylprednisolone intravenously 5 minutes before CPB. After premedication with diazepam (0.2 mg/kg), anesthesia was induced with fentanyl, 10 g/kg; etomidate, 0.2 mg/kg; and thiopental, 2 mg/kg, followed by vecuronium, 0.1 mg/kg. Anesthesia was maintained with fentanyl, 20 g/kg. The patients were ventilated with a fraction of inspired oxygen of 0.5, and when necessary, isoflurane (0.2% to 0.5%) was added to the air-oxygen mixture. An intra-arterial catheter was placed in the right radial artery under local anesthesia. A pulmonary artery catheter (TD Thermodilution, Abbot Laboratories, Chicago, IL) was inserted into the right internal jugular vein after induction of anesthesia. Continuous monitoring of 2 electrocardiogram leads (II and modified V5), radial and pulmonary artery pressures, oxygen saturation, end-tidal carbon dioxide level, and rectal and esophageal temperatures was performed. After CPB, dobutamine and dopamine were provided when necessary. CPB was performed using a roller pump (Cobe Cardiovascular Inc, Arvada, CO), a hollow-fiber membrane oxygenator (Dideco D 708, Simplex, Mirandola, Italy), a polyvinylchloride tubing set, a 2-stage venous cannula, a venous reservoir (Univox IC, Baxter Healthcare Corp, Irvine, CA), and an arterial filter (Dideco D 734 Micro 40, Simplex, Mirandola, Italy). The circuit was primed with 2000 mL of Ringer’s lactate solution, 250 mL of mannitol, 1 g of cefazolin, and 2500 IU of heparin. A nonpulsatile flow of 2.4 L/min/m2 and mild hypothermia (with a rectal temperature of 33°C) were used. During CPB, hematocrit was maintained between 20% and 25%, and the mean arterial pressure was maintained between 50 and 70 mmHg (with sodium nitroprusside or phenylephrine administration as required). Anticoagulation was obtained by the administration of bovine lung heparin (300 IU/kg) just before the institution of CPB; additional doses were administered as required to maintain activated coagulation time ⬎750 seconds for aprotinin-treated patients and ⬎480 seconds for control patients and methylprednisolone-treated patients. After aortic cross-clamping, myocardial preservation was achieved by antegrade and retrograde administration of cold hyperkalemic blood cardioplegia (with a blood-to-crystalloid ratio of 4:1). Before the removal of the aortic cross-clamp, an additional bolus of warm cardioplegia was infused. Distal anastomoses were performed, the aortic cross-clamp was removed, and proximal anastomoses to the aorta were completed during the rewarming period. Extracorporeal circulation was terminated at a rectal temperature of 36°C. At the termination of CPB, 1.3 mg of protamine for every 100 U of total heparin dose was administered and confirmed by the return of activated coagulation time to baseline values. Shed mediastinal blood was not reinfused in any patient. The indication for transfusion was defined as a hematocrit level ⬍20% during CPB and ⬍25% in the postoperative period. Platelet concentrates were administered only in the case of a platelet count ⬍50,000/mm3.
All operations were performed by the same surgeon (R.T.) using a similar operative technique and the same perfusion protocol. Hemodynamic measurements (mean arterial pressure [MAP], mean pulmonary arterial pressure [MPAP], pulmonary capillary wedge pressure [PCWP], and thermodilution cardiac index [CI]) were obtained as follows: TH1, before CPB; TH2, after termination of CPB and administration of protamine; and TH3, 24 hours after CPB (in the intensive care unit). Pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) were calculated using standard formulae. Arterial blood samples were obtained from the radial artery catheter for blood gas measurements (Blood Gas System, Stat Profile 5, Nova Biomedical Waltham, MA). Alveolar-arterial PO2 difference (AaDO2) was calculated using the alveolar gas equation, assuming a respiratory quotient (RQ) of 0.8: PAO 2 ⫽ 共F I O 2 ⫻ 关PBatm ⫺ SVPH 2 O兴兲 ⫺ 共PACO 2 ⫻ 关F I O 2 ⫹ 共1 ⫺ FIO 2 ⲐRQ兲兴兲 where PAO2 is alveolar PO2, FIO2 is fraction of inspired oxygen, PBatm is barometric pressure, SVPH2O is saturated vapor pressure of water at 37°C, and PACO2 is alveolar PCO2, which is assumed to be equal to PaCO2. All measurements were performed with the patient anesthetized in the supine position. The measurement of AaDO2 was simultaneously performed with hemodynamic measurements. Blood samples (20 mL) were drawn from the radial artery catheter or, during CPB, the arterial port of the oxygenator as follows: TB1, immediately before the induction of anesthesia; TB2, 5 minutes before CPB; TB3, 3 minutes after the start of CPB; TB4, 2 minutes after the release of aortic cross-clamp; TB5, 1 hour after CPB; TB6, 6 hours after CPB; and TB7, 24 hours after CPB. Coronary sinus blood samples were obtained from the retrograde cardioplegia cannula at TCSB1, immediately before CPB, and TCSB2, 2 minutes after the release of aortic cross-clamp. Blood samples were centrifuged at 4°C with 3500 rpm for 20 minutes. Plasma was stored at ⫺40°C until assayed. The levels of TNF-␣, IL-1, IL-6, and IL-8 were determined by enzymelinked immunosorbent assay with Immulite kits (Diagnostic Products, Los Angeles, CA) according to the manufacturer’s instructions. The effects of aprotinin or methylprednisolone within the groups were evaluated by the Friedman rank analysis of variance. When the test results indicated significant differences within a group, the measurements were compared against the baseline data using the Wilcoxon matched pair test. The differences among the study groups were evaluated by the Kruskal-Wallis test, followed by the U-test, to detect the groups being actually different from each other. A p value ⬍ 0.05 was considered to be statistically significant. RESULTS
There were no statistically significant differences among the groups with regard to age, sex, body weight, ejection fraction, cross-clamp time, duration of CPB, lowest temperature, number of grafts, the amount of transfused packed red blood cells,
CYTOKINE GENERATION DURING CORONARY SURGERY
Table 1. Demographic and Clinical Characteristics of Patients Group A (n ⫽ 10)
Group MP (n ⫽ 10)
Group C (n ⫽ 10)
Age (y) 60.2 ⫾ 3.4 58.3 ⫾ 3.0 63.8 ⫾ 1.9 Sex (m/f) 9/1 8/2 9/1 Body weight (kg) 74.2 ⫾ 3.1 75.3 ⫾ 3.2 69.1 ⫾ 2.9 EF (%) 50.1 ⫾ 2 53.6 ⫾ 2.3 50.6 ⫾ 2.6 Cross-clamp duration (min) 70.2 ⫾ 4.2 68.2 ⫾ 4.0 68.6 ⫾ 3.7 CPB duration (min) 110.6 ⫾ 5.3 111.4 ⫾ 5.0 111.5 ⫾ 2.4 Lowest temperature (°C) 32.3 ⫾ 1.4 33.2 ⫾ 1.3 33.4 ⫾ 1.4 No. distal grafts (n) 3.6 ⫾ 0.5 3.4 ⫾ 0.2 3.3 ⫾ 0.2 Internal mammary artery (n) 9 10 10 Total heparin dose 32,000 ⫾ 4165*† 24,620 ⫾ 3368 21,530 ⫾ 2814 (103 U) Total protamine dose (mg) 409 ⫾ 54*† 303 ⫾ 43 283 ⫾ 33 Transfusion of PRBC (U) 1.9 ⫾ 0.5 2.1 ⫾ 0.8 2 ⫾ 0.9 Mediastinal tube drainage (mL) 510 ⫾ 44 600 ⫾ 55 680 ⫾ 58 NOTE. Values are mean ⫾ SD or number. Abbreviations: A, aprotinin; MP, methylprednisolone; C, control; EF, ejection fraction; CPB, cardiopulmonary bypass; PRBC, packed red blood cells. *p ⬍ 0.05 Group A v Group MP. †p ⬍ 0.05 Group A v Group C.
and the amount of mediastinal tube drainage. Total heparin dose and total protamine dose were higher in aprotinin-treated patients (Table 1). No patients required platelet transfusions. All patients had uncomplicated perioperative and postoperative recoveries. The principal hemodynamic parameters are summarized in Table 2. MAP was observed to decrease in all groups after CPB (p ⬍ 0.05), but there was no difference among the groups (Table 2). PCWP and SVR decreased similarly in all groups after CPB at TH2 and TH3 (p ⬍ 0.05). PVR increased similarly in all groups after CPB at TH2 and TH3 (p ⬍ 0.05). In all groups, MPAP and CI were not different after CPB at TH2 and TH3 (Table 2). AaDO2 significantly increased (p ⬍ 0.05) in all 3 groups after CPB at TH2. Although the increase was higher in control patients, there were no significant differences among the groups. A significant decrease in AaDO2 was found at 24 hours after CPB in aprotinin-treated patients compared with the other groups (p ⬍ 0.05) (Table 2). TNF-␣ level from the radial artery significantly increased in control patients at 1 hour after CPB (p ⬍ 0.01), and the increase was greater than in aprotinin-treated patients (p ⬍ 0.05) (Fig 1). TNF-␣ did not significantly increase in methylprednisolonetreated patients throughout the study (Table 3 and Fig 1). There was no statistically significant increase in coronary sinus blood levels of TNF-␣ after the release of the aortic cross-clamp in any of the groups (Table 3). No difference was observed for IL-1 level in radial artery and coronary sinus blood throughout the study in any of the
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Table 2. Perioperative and Postoperative Hemodynamic Data TH1
TH2
MAP (mmHg) Group A 99.2 ⫾ 2.9 84 ⫾ 3.1* Group MP 94.5 ⫾ 2.8 82.9 ⫾ 2.3* Group C 93.1 ⫾ 2.3 81.4 ⫾ 3.7* MPAP (mmHg) Group A 20.5 ⫾ 0.9 18.7 ⫾ 1.4 Group MP 19.3 ⫾ 1.3 19.8 ⫾ 1.7 Group C 20.1 ⫾ 2.1 20.2 ⫾ 1.4 PCWP (mmHg) Group A 16.8 ⫾ 0.9 13.1 ⫾ 3.7* Group MP 15.9 ⫾ 0.9 13 ⫾ 1.9* Group C 16 ⫾ 1.7 13.8 ⫾ 1.4* CI (L/min/m2) Group A 2.5 ⫾ 0.2 2.7 ⫾ 0.2 Group MP 2.6 ⫾ 0.1 3.1 ⫾ 0.2 Group C 2.6 ⫾ 0.1 3.1 ⫾ 0.1 SVR (dyne 䡠 sec 䡠 cm⫺5) Group A 1862 ⫾ 134 1501 ⫾ 120* Group MP 1688 ⫾ 136 1355 ⫾ 129* Group C 1678 ⫾ 105 1300 ⫾ 159* PVR (dyne 䡠 sec 䡠 cm⫺5) Group A 69.6 ⫾ 8.9 97.6 ⫾ 7.6* Group MP 58.1 ⫾ 7.5 97.4 ⫾ 12.8* Group C 74.2 ⫾ 10.7 91.9 ⫾ 11.3* AaDO2 (mmHg) Group A 79.5 ⫾ 24.6 135.4 ⫾ 9.6* Group MP 78 ⫾ 31.5 143.5 ⫾ 19.3* Group C 76 ⫾ 20.3 165 ⫾ 16.8*
TH3
87.7 ⫾ 2.4 86.3 ⫾ 4.5 85.9 ⫾ 3.0 18.4 ⫾ 1.2 18.5 ⫾ 1.3 18.9 ⫾ 1.8 11.9 ⫾ 0.9* 12 ⫾ 1.2* 12.4 ⫾ 1.3* 3.0 ⫾ 0.0 3.2 ⫾ 0.0 3.2 ⫾ 0.0 1423 ⫾ 100* 1330 ⫾ 104* 1360 ⫾ 75* 101.9 ⫾ 12.8* 90.2 ⫾ 11* 95.5 ⫾ 14.8* 87.2 ⫾ 16.7†‡ 128.6 ⫾ 2.5* 117.4 ⫾ 1.6*
NOTE. Values are mean ⫾ SD. Abbreviations: TH1, before cardiopulmonary bypass (CPB); TH2, after cessation of CPB and administration of protamine; TH3, 24 hours after CPB; A, aprotinin; MP, methylprednisolone; C, control; MAP, mean arterial pressure; MPAP, mean pulmonary arterial pressure; PCWP, pulmonary capillary wedge pressure; CI, cardiac index; SVR, systemic vascular resistance; PVR, pulmonary vascular resistance; AaDO2, alveolar-arterial PO2 gradient. *p ⬍ 0.05 v TH1. †p ⬍ 0.05 Group A v Group MP. ‡p ⬍ 0.05 Group A v Group C.
Fig 1. Tumor necrosis factor (TNF)-␣ levels. Aprotinin group (}); methylprednisolone group (■); control group (Œ). *p < 0.05 versus TB1. **p < 0.01 versus TB1. †p < 0.05 between aprotinin and control group. ‡p < 0.05 between methylprednisolone and control group. #p < 0.05 between aprotinin and methylprednisolone group. See text for explanation of abbreviations.
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Table 3. Cytokine Levels (pg/mL) TB1
TNF-␣ Group Group Group IL-1 Group Group Group IL-6 Group Group Group IL-8 Group Group Group
TB2
TB3
TB4
TB5
TB6
A MP C
7.7 ⫾ 0.5 8.2 ⫾ 1 9.6 ⫾ 0.3
11.4 ⫾ 1.9 8.2 ⫾ 1.2 10.1 ⫾ 0.8
12.4 ⫾ 4 10.1 ⫾ 2.5 10.6 ⫾ 1.2
12.7 ⫾ 2.5 10 ⫾ 2.4 13 ⫾ 1.1
*14 ⫾ 1.8† 10 ⫾ 1.4‡ **30 ⫾ 6.3
*18.1 ⫾ 4.3# 9.5 ⫾ 1.6‡ *16.2 ⫾ 1.7
A MP C
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 4.9 ⫾ 0.0
4.9 ⫾ 0.0 4.9 ⫾ 0.0 6.3 ⫾ 1.4
8.8 ⫾ 6.6 7.8 ⫾ 5.9 6.1 ⫾ 1.2
A MP C
7.7 ⫾ 1.3 8.1 ⫾ 1.3 10.5 ⫾ 3.1
10.2 ⫾ 2.8 12.7 ⫾ 2.3 9.6 ⫾ 2.2
A MP C
17.7 ⫾ 4.5 12.2 ⫾ 4 9.6 ⫾ 1.3
15 ⫾ 3.7 9.8 ⫾ 2 8.4 ⫾ 1
11.8 ⫾ 1.8 *15.6 ⫾ 3.1‡† ***250 ⫾ 38# ****704 ⫾ 89• 13.3 ⫾ 10 **29.4 ⫾ 8.5‡ ***122 ⫾ 29¶ ***148 ⫾ 34¶ 12.9 ⫾ 2.7 **80.4 ⫾ 23 ****522 ⫾ 10 ****671 ⫾ 82 18 ⫾ 9.2 7.0 ⫾ 0.9 6.1 ⫾ 0.8
17.8 ⫾ 5.5 *29.5 ⫾ 16 *22.3 ⫾ 9.7
*35.8 ⫾ 26† *35.8 ⫾ 9.6‡ ****114.5 ⫾ 3.1
**63.6 ⫾ 14 **49.8 ⫾ 18 ***83 ⫾ 22
TB7
TCSB1
TCSB2
*15.6 ⫾ 2.7 11.9 ⫾ 2.5 12.3 ⫾ 1.3
10.1 ⫾ 5 11.3 ⫾ 2 16 ⫾ 4.4
11.5 ⫾ 3 8.5 ⫾ 3 19 ⫾ 7.2
5.0 ⫾ 0.1 5.0 ⫾ 0.1 4.9 ⫾ 0.0
4.9 ⫾ 0.1 4.9 ⫾ 0.1 4.9 ⫾ 0.0
4.9 ⫾ 0.1 5.5 ⫾ 0.1 4.9 ⫾ 0.0
***437 ⫾ 107• **65.8 ⫾ 14¶ ***279 ⫾ 46
16.4 ⫾ 7.4 25.9 ⫾ 11 14.7 ⫾ 5.9
15.4 ⫾ 3.6 37.3 ⫾ 7.3 *77 ⫾ 39
**46.2 ⫾ 7.6 *32.0 ⫾ 11‡ ***48.9 ⫾ 9.4
14.8 ⫾ 4.9 17.1 ⫾ 5 11.3 ⫾ 0.8
20.2 ⫾ 6.7 20.2 ⫾ 7.9 *20 ⫾ 4.7
NOTE. Values are mean ⫾ SD. Abbreviations: TB1, immediately before the induction of anesthesia; TB2, 5 minutes before cardiopulmonary bypass (CPB); TB3, at 3 minutes on CPB; TB4, 2 minutes after release of the aortic cross-clamp; TB5, 1 hour after CPB; TB6, 6 hours after CPB; TB7, 24 hours after CPB; TCSB1, coronary sinus blood samples immediately before CPB; TCSB2, 2 minutes after release of the aorta cross-clamp; A, aprotinin; MP, methylprednisolone; C, control; TNF, tumor necrosis factor; IL, interleukin. *p ⬍ 0.05 v baseline. **p ⬍ 0.01 v baseline. ***p ⬍ 0.005 v baseline. ****p ⬍ 0.001 v baseline. †p ⬍ 0.05 (group A v group C). ‡p ⬍ 0.05 (group MP v group C). #p ⬍ 0.05 (group A v group MP). ‡†p ⬍ 0.01 (group A v group C). •p ⬍ 0.005 (group A v group MP). ¶p ⬍ 0.005 (group MP v group C).
groups (Table 3). In all groups, plasma IL-6 levels were low before and at 3 minutes on CPB (Table 3 and Fig 2). IL-6 levels were elevated after the release of the aortic cross-clamp in all groups. IL-6 levels continued to increase at 1 hour and 6 hours
Fig 2. Interleukin (IL)-6 levels. Aprotinin group (}); methylprednisolone group (■); control group (Œ). *p < 0.05 versus TB1. **p < 0.01 versus TB1. ***p < 0.005 versus TB1. ****p < 0.001 versus TB1. ‡p < 0.05 between methylprednisolone and control group. ††p < 0.01 between aprotinin and control group. #p < 0.05 between aprotinin and methylprednisolone group. ¶p < 0.005 between methylprednisolone and control group. ●p < 0.005 between aprotinin and methylprednisolone group. See text for explanation of abbreviations.
after CPB and peaked at 6 hours after CPB. IL-6 levels decreased at 24 hours after CPB but remained above baseline levels in all groups. The elevation of IL-6 levels in methylprednisolone-treated patients was significantly less compared with control patients at 1 hour after CPB (p ⬍ 0.001). The increase in IL-6 levels in aprotinin-treated patients was less compared with control patients (p ⬍ 0.05); however, the difference was less pronounced when compared with methylprednisolone-treated patients. At 1 hour and at 6 hours after CPB, the increases in IL-6 levels in methylprednisolone-treated patients were significantly less compared with the other groups (p ⬍ 0.001). In coronary sinus blood, IL-6 levels increased only in control patients after the release of the aortic cross-clamp (p ⬍ 0.05), but the level was not different from the radial artery samples obtained at the same time period (Table 3). IL-8 levels were similar before and at 3 minutes on CPB in all groups (Table 3 and Fig 3). In control patients, IL-8 levels significantly increased at 2 minutes after the release of the aortic cross-clamp (p ⬍ 0.05), and the increase peaked at 1 hour after CPB (p ⬍ 0.001). IL-8 levels in control patients were significantly higher compared with aprotinin-treated patients and methylprednisolone-treated patients at 1 hour after CPB (p ⬍ 0.05). At 6 hours after CPB, IL-8 levels remained above baseline levels in all groups. The elevation was less pronounced in methylprednisolone-treated patients and aprotinin-treated
CYTOKINE GENERATION DURING CORONARY SURGERY
Fig 3. Interleukin (IL)-8 levels. Aprotinin group (}); methylprednisolone group (■); control group (Œ). *p < 0.05 versus TB1. **p < 0.01 versus TB1. ***p < 0.005 versus TB1. ****p < 0.001 versus TB1. †p < 0.05 between aprotinin and control group. ‡p < 0.05 between methylprednisolone and control group. See text for explanation of abbreviations.
patients (p ⬍ 0.01) compared with control patients (p ⬍ 0.001). IL-8 level in methylprednisolone-treated patients was significantly different from that in control patients at 24 hours after CPB (p ⬍ 0.05). In coronary sinus blood, IL-8 levels increased in all groups, but the increase was significant only in control patients after the release of the aortic cross-clamp (p ⬍ 0.05) (Table 3). IL-8 levels in coronary sinus blood were not different from the radial artery samples obtained at the same time period. DISCUSSION
This study focuses on systemic and myocardial cytokine release after CPB. The effects of aprotinin and methylprednisolone in reducing the levels of proinflammatory cytokines and the effects of cytokine release on hemodynamic parameters have been investigated. The major findings of the study can be summarized as follows: (1) An increase in TNF-␣ levels was observed after CPB, and this increase was inhibited only by methylprednisolone; (2) an increase in IL-6 levels was observed after the release of the aortic cross-clamp, which peaked 6 hours after CPB and was reduced only with the use of methylprednisolone; (3) IL-8 release peaked 1 hour after CPB, and aprotinin and methylprednisolone suppressed the increase in IL-8 levels, but the suppression was more prominent with methylprednisolone at 24 hours after CPB; and (4) the suppression of cytokine release with the use of aprotinin and methylprednisolone did not directly influence the hemodynamic parameters. Cytokines, a group of low-molecular-weight polypeptides functioning as intercellular communication molecules, have a central role in inflammatory reactions, particularly acting on the heart, lung, liver, coagulation system, and central nervous system, subsequently causing damaging effects.9-11,22-26 Many clinical studies have shown significant increases in blood cytokine levels during and after CPB.5-7,27,28 Alterations in cytokine levels after CPB gathered from various studies are summarized in Table 4. The most widely studied proinflammatory cytokines are TNF-␣, IL-1, IL-6, and IL-8. TNF-␣ contributes to myocardial dysfunction and hemodynamic instability after CPB.23,28,29 In some studies, TNF-␣ has been detected in
607
plasma after CPB,30-32 but not in others.5,33,34 The short half-life of TNF-␣ and the differences between the methods of cytokine measurement may explain the discrepancies among the results presented in various studies. The absence of detectable circulating cytokines does not rule out a likely local production by the activated cells.35 The activation pattern of TNF-␣ has been shown to be dependent on the body core temperature during CPB.28 Patients operated with warm CPB have a significantly higher release of TNF-␣.28 In the present study, TNF-␣ levels peaked only in the control patients at 1 hour after CPB. Methylprednisolone completely inhibited the increase in TNF-␣ levels, but with aprotinin the levels were slightly attenuated. The use of tepid temperature (33°C) during CPB might have triggered TNF-␣ release in the control patients. IL-1 is mostly located intracellularly, and the appearance of IL-1 in the circulation is likely a reflection of tissue destruction.36 Various studies have reported different levels of IL-1 increase during and after CPB.28,37-41 IL-1 production has been found to correlate with the maximum postoperative temperature rise.28 In many studies, IL-1 has not been detected in plasma after hypothermic CPB.5-7,41,42 Patients operated with normothermic CPB have a significantly higher release of IL1.28 In the present study, a significant increase in circulating IL-1 levels was not observed after tepid CPB in any group. IL-6 is one of the key mediators in acute-phase response43 and is synthesized by a variety of cells, including endothelial cells and leukocytes.2,6,44 Significantly increased levels of IL-6 have been found in patients after CPB.3,13,16-18,28,39,40,42 IL-6 levels are higher in patients with complications after cardiac surgery.23 The hemodynamic effects of IL-6 are controversial. In 1 study, IL-6 administration in dogs had no acute hemodynamic effects,45 whereas in another study, cytokine-stimulated nitric oxide production was found to be responsible for the reversible myocardial depression.22 Elevated systemic levels of IL-6 have been observed in patients with congestive heart
Table 4. Cytokine Levels After Cardiopulmonary Bypass
al5
Butler et Finn et al7 Jansen et al12 Kawamura et al13 Weerwind et al16 Hill et al19 Diego et al20 Hennein et al23 Wan et al27 Menasche´ et al28 Velthuies et al29 Teoh et al30 Jansen et al31 Frering et al33 Engelman et al37 Deng et al41 Butler et al42 Ashraf et al50 Liebold et al52
TNF-␣
IL-1
NC NC 1
NC
NC 1 1 1 1/1 1 1 1 NC 1 NC
NC/1
NC 1 NC
IL-6
IL-8
1 1 1
1 1
1 1 1 1/1
1 1
1
1
1
1 1
1 1 1/1 1
Temperature (°C)
32-34 16-32 28-30 28 32 32 26-28 30 28-30/35-37 28-30 36-37 28-30 36.5 37 37 30-34 18/26-28 32-34
Abbreviations: TNF, tumor necrosis factor; IL, interleukin; NC, no change.
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failure and have been correlated with prognosis.46,47 In the present study, IL-6 levels increased after the release of the aortic cross-clamp. The increase continued at 1 hour after CPB and peaked at 6 hours after CPB. IL-6 levels remained elevated at 24 hours in all groups. Aprotinin did not attenuate the increase in IL-6 levels, but it delayed the increase during the early period of CPB. The administration of methylprednisolone before CPB significantly inhibited the release of IL-6. IL-8, predominantly produced by macrophages, fibroblasts, neutrophils, and endothelial cells, is a potent chemoattractant for neutrophils, controlling their trafficking.33 CPB-induced lung injury is thought to be related to pulmonary leukocyte sequestration. Ratliff et al48 found no severe endothelial damage in the absence of large numbers of polymorphonuclear leukocytes. Subsequent infiltration of neutrophils into the perivascular tissue resulted in the release of oxygen-derived free radicals, proteases, and elastases, leading to increased capillary permeability and nonspecific cellular damage.49 Ashraf et al50 showed a positive correlation between prolonged intubation and IL-8 concentrations in pediatric patients undergoing cardiac surgery. This pathologic process may lead to postoperative respiratory dysfunction and multisystem organ failure. In the present study, methylprednisolone and aprotinin suppressed the increase in IL-8 levels compared with the control group. The suppression was slightly more pronounced with the use of methylprednisolone. Numerous clinical studies have attempted to find the source of proinflammatory cytokines released during and after CPB.23,24,51,52 Some studies concluded myocardium to be the main source of proinflammatory cytokines during CPB, whereas others reported no significant difference between coronary sinus and systemic arterial blood proinflammatory cytokine levels during the early period after CPB. The present study did not find any significant difference between coronary sinus and systemic arterial blood levels. One of the limitations of the present study as well as the other studies that have been unable to find any difference is, however, that coronary sinus blood sampling was concluded immediately after CPB, despite the fact that all cytokines reached peak levels at 1 or 6 hours after CPB. Cytokine release has been found to significantly correlate with the duration of ischemia after cardiac transplantation and coronary artery bypass graft surgery.27 The cardiac release of the cytokines significantly increased with reperfusion after longer ischemic periods or acute myocardial infarction.27,53 TNF-␣, IL-1, IL-6, and IL-8 levels have been found to be increased during CPB, and the release of these cytokines has been proposed to contribute to the development of postoperative organ dysfunction and multiple organ failure.8-11 Several studies have examined a variety of strategies to diminish the release of proinflammatory cytokines, including use of corticosteroids, aprotinin, adenosine, pentoxifylline, heparin-coated
CPB circuits, ultrafiltration, and warm versus cold CPB and the modification of surgical techniques (off-pump surgery).54 The administration of steroids before CPB has been used during cardiac surgery since the 1970s. The exact mechanism of action of steroids during CPB is not completely understood. Studies have focused on the inhibition of the release of proinflammatory cytokines, including TNF-␣, IL-1, IL-6, and IL-8.12,13,19,20,30,37,40 Steroids also increase the production of an anti-inflammatory cytokine, IL-10.54 Aprotinin, a known protease inhibitor, is primarily used to improve hemostasis after CPB. Aprotinin has been shown to reduce the inflammatory response characterized by TNF-␣ and IL-6 release14,19,20 and to prevent the upregulation of neutrophil CD11b integrin expression after CPB.19 Aprotinin decreases neutrophil activation and the level of IL-8 in bronchial lavage fluid when compared with placebo.55 In simulated bypass, Wachtfogel et al56 showed that high-dose aprotinin may completely inhibit kallikrein activation, partially inhibit neutrophil activation, and decrease platelet activation. The present study has shown that methylprednisolone exhibits more inhibitory effects on cytokine levels than aprotinin after CPB. The administration of methylprednisolone has not been associated with additional positive hemodynamic effects after CPB, however, compared with the control group. The use of aprotinin, inhibiting only the release of IL-8, has significantly lowered AaDO2 compared with the methylprednisolone group. The protective effects of aprotinin on the lungs have been shown in studies. In the authors’ belief, these effects are not only related to the proinflammatory cytokines, but also to some other mechanisms. In the present study, the lack of any clinical alterations despite the suppression of cytokine levels after methylprednisolone administration was a striking observation. This observation can be explained in part by the facts that the patients included in the study were low risk based on their preoperative cardiac and pulmonary function and that the number of patients included in the study was relatively low. Despite the suppression in cytokine release after methylprednisolone administration in the control group, a 15-fold increase in IL-6 levels and a 3-fold increase in IL-8 levels at 6 hours after CPB in the methylprednisolone group might indicate that methylprednisolone does not lead to adequate suppression. In conclusion, the present study has shown that methylprednisolone suppresses most of the cytokines released, including TNF-␣, IL-6, and IL-8. Aprotinin attenuates only IL-8 release, however. Methylprednisolone does not produce any additional positive hemodynamic and pulmonary effects. An improvement in postoperative lung function in terms of AaDO2 has been observed with the use of aprotinin. Further studies are required to assess the ideal pharmacologic strategies to reduce the effects of cytokines on inflammatory response and the subsequent damaging effects after CPB.
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