Efficacy of Ultrafiltration in Removing Inflammatory Mediators During Pediatric Cardiac Operations

Transcription

1 Efficacy of Ultrafiltration in Removing Inflammatory Mediators During Pediatric Cardiac perations Ming-Jiuh Wang, MD, Ing-Sh Chiu, MD, PhD, Chao-Ming Hsu, MD, Chao-Min Wang, MD, Pei-Lin Lin, MD, Chung-I Chang, MD, Chi-Hsiang Huang, MD, and Shu-Hsun Chu, MD Departments of Anesthesiology and Surgery, National Taiwan University Hospital, Taipei, Taiwan Background. Conventional and modified ultrafiltration was used in pediatric cardiac operations to reduce volume overload and total body water. The purpose of this study was to compare the efficacy of these techniques in removing inflammatory mediators during cardiopulmonary bypass. Methods. Fifty pediatric patients undergoing cardiac operations were randomized into a modified or conventional ultrafiltration group. Blood samples were obtained before and after ultrafiltration to assess the plasma concentrations of leukocyte elastase, tumor necrosis factor-o, interleukin-6, and interleukin-8. Results. Except for plasma concentrations of tumor necrosis factor- ~ in the modified ultrafiltration group, the plasma concentrations of all the mediators measured increased after ultrafiltration in both groups of patients. The volume of ultrafiltrate and the total amounts of tumor necrosis factor-~ and interleukin-6 removed by ultrafiltration were significantly greater in the modified group. The concentrations of mediators in the ultrafiltrate and the ratio of ultrafiltrate to plasma concentrations of the mediators did not differ between the groups. Ultrafiltration was more efficient in removing tumor necrosis factor-o~ than the other mediators. Conclusions. The efficacy in removing the inflammatory mediators generated during cardiopulmonary bypass did not differ between modified and conventional ultrafiltration. (Ann Thorac Surg 1996;61:651-6) Pen heart operations in infants and children have associated capillary leak with tissue edema and an increase in total body water [1]. In addition, the systemic inflammatory response occurring during cardiopulmonary bypass (CPB) has resulted in the release of a number of inflammatory mediators, including tumor necrosis factor-a (TNF-a), interleukin-6 (IL-6), interleukin-8 (IL-8), and leukocyte elastase [2-4]. These substances were suggested to be responsible for postoperative organ dysfunction and morbidity [5-8]. Ultrafiltration is a convective process that removes water and low-molecular-weight solutes from the blood through a semipermeable membrane by hydrostatic pressure gradient. This procedure has been used successfully to reduce total body water and tissue edema in pediatric open heart operations [9, 1]. In addition, ultrafiltration has been suggested to be effective in removing inflammatory mediators generated during CPB [1-12]. There are two different ultrafiltration techniques used during CPB. In conventional ultrafiltration, carried out during the rewarming phase of CPB, the ultrafilter inlet is placed distal to the oxygenator and its outlet is positioned in the venous reservoir. In contrast, modified ultrafiltration is carried out after termination of CPB; the ultrafilter inlet is positioned close to the arterial cannula and the Accepted for publication ct 1, Address reprint requests to Dr Huang, Department of Anesthesiology, National Taiwan University Hospital, 7, Chung-Shan South Rd, Taipei, Taiwan, 1. outlet returns directly to the right atrium [13]. The modified ultrafiltration technique was proposed to be superior to the conventional one for improving hemodynamic status after CPB and for reducing total body water [9] and the amount of donor blood used in pediatric cardiac operations [13]. The purpose of this prospective, randomized study was to compare the efficacy of the conventional and modified ultrafiltration techniques for removing the inflammatory mediators generated during CPB in pediatric open heart operations. Material and Methods We studied 52 infants and children undergoing open heart operations. The work was approved by the Committee of Human Investigation of this hospital, and written informed consent was obtained from the parents of the patients. The patients were prospectively randomized into a conventional ultrafiltration group or a modified ultrafiltration group. In all patients, anesthesia was induced with intravenous ketamine (1.5 mg/kg), fentanyl (3 /xg/kg), and pancuronium (.15 mg/kg) and was maintained with fentanyl (.3 ~g kg 1. min 1) during the operations. Cardiopulmonary Bypass and Ultrafiltration In all patients, moderate hypothermic CPB with lowest nasopharyngeal temperature of approximately 2 to 25 C with pulsatile flow was instituted with the roller 1996 by The Society of Thoracic Surgeons /96/$15. PubLished by Elsevier Science Inc SSDI (95)974-4

2 652 WANG ET AL Ann Thorac Surg ULTRAFILTRATIN IN PEDIATRIC CPB 1996;61:651-6 pump (Sarns 5; Sarns 3M, Ann Arbor, MI) and bubble oxygenators (William Harvey H13; Bard, Billerica, MA). The priming solution contained 75 to 1, ml lactated Ringer's solution, and, if the predicted hematocrit during CPB was lower than 2%,.5 to 1 U of packed red blood cells was added to the priming solution. Except for the modified group of patients, a hematocrit greater than 18% was considered adequate during CPB. The perfusion flow was kept greater than 1 ml/kg during hypothermia and greater than 12 ml/kg during normothermia in every patient. Anticoagulation therapy was achieved with heparin, 3 mg/kg, and was reversed with protamine, 3 to 3.5 mg/kg, after termination of CPB and ultrafiltration. Myocardial preservation was achieved with intermittent cold blood cardioplegia composed of crystalloid cardioplegic solution (Plegisol; Abbott Co, Ann Arbor, MI) and oxygenated blood from the oxygenator. The blood cardioplegic solution was aspirated to the cardiotomy reservoir during CPB. In both the conventional and modified ultrafiltration groups, an ultrafiltrater (Hemocor Plus; Minntech Corp, Minneapolis, MN) was placed in the bypass circuit. In the conventional group, the inlet of the ultrafiltrater was connected to the arterial tubing distal to the oxygenator, and the outlet was connected to the cardiotomy reservoir. In the modified group, the inlet was positioned close to the arterial cannula and the outlet was returned directly to the right atrium, as described previously [13]. The process of ultrafiltration was started from the rewarming phase of CPB in the conventional group, with a rate adjusted to reach the cardiotomy reservoir level approaching zero at the termination of CPB. The blood remaining in the CPB circuit after termination of CPB was centrifuged with a cell separator and transfused back to the patient in the intensive care unit. In the modified group, the process of ultrafiltration was started after the termination of CPB with an ultrafiltration rate of 1 to 15 ml/min, and lasted for 15 minutes. Lactated Ringer's solution was added to the oxygenator when the fluid level became very low, to keep the circuit primed. In both groups of patients, suction of 2 mm Hg negative pressure was applied to the filtrate port to maximize the filtration rate. The volume of ultrafiltrate removed during the process was recorded. Assays and Measurements To assess the efficacy of ultrafiltration in removing inflammatory mediators generated during CPB, we took 2-mL blood samples from the radial artery at the following times: before operation, before the start of ultrafiltration, immediately after termination of ultrafiltration, and at the end of the operation. In the conventional group, the time to start ultra filtration was at the initiation of rewarming during CPB; however, in the modified group it was after the termination of CPB. Blood samples and the 2-mL samples of ultrafiltrate were collected in sterile vacuum tubes containing ethylenediamine tetraacetic acid and were immediately centrifuged at 1, g for 2 minutes. Aliquots of plasma were stored at -8 C until assay, within 1 month. ELASTASE. The plasma concentration of leukocyte elastase was measured with the PMN Elastase Immunoassay (E. Merck, Frankfurt, Germany). The elastase is bound to its natural inhibitor cd-antiprotease in the blood. The assay was done by the sandwich method, in which antielastase antibody was precoated in the tube and enzyme-labeled anti-cd-antiprotease antibody with substrate was added to determine the concentrations of elastase-c~lantiprotease complex in the plasma. TUMR NECRSIS FACTR-~/ INTERLEUKIN-6, AND INTERLEU- KIN-8. Concentrations of TNF-~ and IL-6 were analyzed with a specific enzyme-linked immunosorbent assay (Cytoscreen, Biosource International, Camarillo, CA). Biotinylated monoclonal antibodies specific for TNF-a or IL-6 were used for the assays. The sensitivity of detection was 1 pg/ml for both TNF-c~ and IL-6. The level of plasma IL-8 was determined with the IL-8/NAP-1 enzyme-linked immunosorbent assay kit (Bender + Co Ges mbh, Vienna, Austria) with a detection sensitivity of I pg/ml. No values were corrected for hemodilution during CPB. Clinical variables recorded to evaluate clinical outcome of the patients included hematocrit and hemoglobin levels 24 hours after operation, amount of packed red blood cells transfused, times of intubation and hospitalization in the intensive care unit, highest postoperative rectal temperature, urine output, and doses of the diuretic and inotropic agents used in the intensive care unit. Statistical Analysis Student's t test was performed to compare numeric variables between the groups, with a probability less than.5 considered statistically significant. Paired t test was done to compare the values before and after ultrafiltration. ne-way analysis of variance was used to analyze the efficacy of the ultrafiltration techniques for removing the four inflammatory mediators from the plasma. Statistical procedures were done with the advanced version of SPSS for Windows (SPSS Inc, Chicago, IL). Results There were 25 and 27 patients in the modified and conventional ultrafiltration groups, respectively. ne patient in each group died of cardiac failure and could not be weaned from CPB during the operation. The demographic and operative data of the two groups of patients are shown in Table 1. The age and body weight did not differ between the groups, and the surgical procedures performed were similar. Figure 1 shows the alterations of the plasma concentrations of inflammatory, mediators studied before and after ultrafiltration. The plasma concentrations of elastase, IL-6, and IL-8 increased significantly after ultrafiltration in both groups; however, TNF-c, increased significantly only in the conventional group (Fig 1B). The extent of increase and plasma concentrations of elastase, IL-6, and IL-8 after ultrafiltration did not differ between the groups of patients. Table 2

3 Ann Thorac Surg WANG ET AL ;61:651-6 ULTRAFILTRATIN 1N PEDIATRIC CPB Table 1. Demographic and perative Data of the Patients in the Ultrafiltration Groups" Modified Conventional Characteristic (n = 24) (n = 26) Age (y) 5.18 _ _+.54 Sex (male:female) 12:12 18:8 Body weight 18.9 _ Diagnosis Atrial septal defect 3 4 Ventricular septal defect 8 11 Tetralogy of Fallot 9 9 Endocardial cushion defect 1 1 ther 3 1 CPB time 88.6 ± Aortic cross-clamp time 43.6 ± Values are expressed as mean ± standard error of the mean. CPB = cardiopulmonary bypass. presents the volume of the ultrafiltrate in each group and the concentrations and total amount of mediators removed by ultrafiltration. The total amounts of TNF-a and IL-6 removed from the circulation by ultrafiltration were significantly greater in the modified than in the conventional group. Figure 2 illustrates the efficacy of the ultra- fltration techniques in removing inflammatory mediators, as revealed by the ratio of the ultrafiltrate to plasma concentrations of mediators. The process of ultrafiltration was more effective in removing TNF-a than the other mediators, but the efficacy in removing mediators did not differ between the ultrafiltration techniques. The alterations of hematocrit and hemoglobin concentration are shown in Figure 3. The increase of hematocrit after ultrafiltration was significantly greater in the modified group than in the conventional group (13.8% _+.9% versus 7.7% _+ 1.%; p <.1). There were no differences between the modified and conventional groups regarding hours stayed in the intensive care unit, duration of intubation, highest postoperative rectal temperature, urine output, or the doses of diuretic and inotropic agents. Comment Hemofiltration, used in pediatric cardiac operations to remove excessive body water, can be separated into modified and conventional techniques according to the connection with the bypass circuit and the time of starting ultrafiltration [13]. Modified ultrafiltration has been advocated as more effective than conventional ultrafiltration for removing total body water and improving post- 8 - v 6 - t-- [ I-- Modified "-r- 8o- --D--Conventional ~ l ~ ; ~. -._o 6-4- i 2- --I-- Modifed --D-- Conventional UJ (A) Before CPB Pre-filtration Post-filtration P end (C) i i i i Before CPB Pre-filtration Post-filtration P end I-- Modified --B-- Conventional I-- Modified --I-1-- Conventional t "E 12- ~ 6- Z I..- o _J 2-1- i i i i i i i i (B) Before CPB Pre-filtration Post-filtration P end (D) Before CPB Pre-filtration Post-filtration Pend Fig 1. Alterations of the plasma concentrations of leukocyte elastase (A), tumor necrosis factor-a (TNF a) (B), interleukin-6 (IL-6) (C), and interleukin-8 (IL-8) (D) before and after modified ultrafiltration (closed squares) and conventional ultrafiltration (open squares). Asterisks indicate significant increase versus values before modified or conventional ultrafiltration. (CPB = cardiopulmonary bypass; P end - end of operation.)

4 654 WANG ET AL Ann Thorac Surg ULTRAFILTRATIN IN PEDIATRIC CPB 1996;61:651-6 Table 2. Volume of Ultrafiltrate and Concentrations of Inflammatory Mediators" Measurement Modified Conventional p Value Volume of ultrafiltrate Elastase in ultrafiltrate (ng/ml) Elastase removed (ng) TNF-a in ultrafiltrate (pg/ml) TNF-c~ removed (pg) IL-6 in ultrafiltrate (pg/ml) IL-6 removed (pg) IL-8 in ultrafiltrate (pg/ml) IL-8 removed (pg) a Values are expressed as mean +- standard error of the mean. IL = interleukin; NS = not significant; TNF-c~ = tumor necrosis factor-rx. 1,896.7 ± < _ NS 1, , ,587.5 NS 7.48 _ ±.93 NS 14, , , < NS 2, < NS 1,66.7 +_ , ,343. NS operative hemodynamics and organ function [9, 13]. In a recent report about conventional ultrafiltration, it was shown that hemofiltration was effective in removing TNF-a and IL-6, with reductions of the plasma concentrations of these substances after ultrafiltration [1]. However, the efficacy of modified ultrafiltration for removing the inflammatory mediators generated during CPB [3, 4] and comparisons between these techniques regarding their usefulness during pediatric cardiac operations were not demonstrated. This study used modified and conventional ultrafiltration in two groups of pediatric patients to compare their efficacy in removing the inflammatory mediators generated during CPB. Because the ratios of ultrafiltrate to plasma concentrations of TNF-c~, IL-6, IL-8, and leukocyte elastase did not differ between the groups of patients, we suggest that the 1 1 E.9 1/1 ~ -~,6- Q. c- o o "-' -~ in Modified.8-1 T I I Conventional,4- D ~ TNF IL-8 IL-6 Elastase Fig 2. Ratio of ultra filtrate to plasma concentrations of tumor necrosis factor-c~ (TNF), interleukin-6 (IL-6), interleukin-8 (IL-8), and leukocyte elastase. #p <.5 versus other variables in modified group; *p <.5 versus other variables in conventional group. different techniques of ultrafiltration had similar efficacy for removing inflammatory mediators from the blood. In contrast to previous findings [1, 11], our results showed that actual plasma concentrations of all the mediators measured, except for TNF-c~ in the modified group, increased significantly after ultrafiltration in both groups of patients (see Fig 1). Results for hemodilution or hemoconcentration were not corrected because it is the actual plasma concentrations of these mediators that may produce their biologic actions in the body. It is known that the inflammatory mediators were generated maximally during the rewarming phase of CPB [3]. If these mediators were not removed sufficiently during ultrafiltration, their plasma concentrations would increase because of the reduction of total body water by ultrafiltration. Because the plasma concentrations of these inflammatory mediators were increased during CPB [2-4] and the duration of ultrafiltration in the modified group was only 15 minutes, it seemed that the increase of these inflammatory mediators after ultrafiltration was not due to the procedure of ultrafiltration itself. Without the requirement to maintain the reservoir level during CPB, a much higher ultrafiltrate volume could be obtained during modified ultrafiltration, which, in combination with greater efficiency of the ultrafiltration in removing TNF-c~, did not increase the plasma concentration of TNF-a after ultrafiltration. In addition, the total amount of TNF-a removed was significantly greater in the modified group than in the conventional group. n the other hang much less ultrafiltrate volume could be obtained during conventional ultrafiltration, and the ultrafiltration process was less efficient for removing other mediators, as plasma concentrations of leukocyte elastase, IL-6, and IL-8 were increased after ultrafiltration. The volume of the ultrafiltrate for either group in this study was greater than that reported by Journois and associates [1]. However, the efficacy of ultrafiltration in removing these mediators was less evident. This discrepancy between the results of this study and previous findings [1, 11] is not yet explained. However, it may result from the use of a different filtration system with different efficacy, or from different methods of measuring the inflammatory mediators.

5 Ann Thorac Surg WANG ET AL ;61:651-6 ULTRAF1LTRATIN IN PEDIATRIC CPB 45 4(] 35 3 v.~ 25 (3 2 E 15 "1- (A) _1 "o E ~8..I3 6 3 E 4 I Before P During CPB p end (B) Before P During CPB p end Fig 3. Alterations of hematocrit (A) and hemoglobin (B) levels in modij~'ed (closed bars) and conventional (open bars) ultrafiltration groups during operation. (CPB - cardiopulmonary bypass; p end end of operation.) Tumor necrosis factor-a, IL-6, IL-8, and leukocyte elastase were reported to increase during CPB and were suggested to play a role in the development of postoperative organ dysfunction [5-8]. Results revealed that the ultrafiltration technique was most effective in removing TNF-a, but very inefficient in removing IL-6, IL-8, and leukocyte elastase. The reason why ultrafiltration could remove TNF-a efficiently but not the other mediators is not known. Theoretically, substances with a molecular weight of less than 2 kd are able to undergo ultrafiltration [14]; the molecular weight cutoff for the ultrafiltrater used in this study was 17 kd. The molecular weight of IL-6 is between 2 and 3 kd, of IL-8 is 8 to 1 kd, and of TNF-a is 17 to 5 kd [15, 16]. Thus, the efficacy of removal from the circulation by ultrafiltration could not be explained by different molecular weights. Different conformations of molecules might contribute to the efficiency and sieving coefficients [14] of the ultrafiltrater to remove the substances in plasma. Because the elastase-alantiprotease inhibitor complex formed in the circulation may be too large to be filtered in the ultrafiltrate, and the assay system used also measured the quantity of this complex, it is not surprising that elastase was nearly not recovered from the ultrafiltrate. The similar clinical outcomes between the groups of patients indicated that even a greater amount of TNF-a could be removed by modified ultrafiltration; however, the type of ultrafiltration was not a major determinant for postoperative organ dysfunction. This study did not try to determine the efficacy of these two maneuvers of ultrafiltration as the blood conservation technique. Nonetheless, the lower hematocrit during CPB and the significantly greater increase in hematocrit after modified ultrafiltration clearly demonstrated the greater efficacy of modified, as opposed to conventional, ultrafiltration for the removal of total body water. We conclude that the efficacy in removing the inflammatory mediators generated during CPB did not differ between the modified and conventional ultrafiltration techniques. However, a much greater amount of TNF-a could be removed from the circulation in the modified group, as demonstrated by a greater ultrafiltrate volume and higher removal efficiency compared with the other mediators. References 1. Maehara T, Novak I, Wyse RKH, Elliott MJ. Perioperative monitoring of total body water by bioelectrical impedance in children undergoing open heart surgery. Eur J Cardiothorac Surg 1991;5: Butler J, Pillai R, Rocker GM, Westaby S, Parker D, Shale DJ. Effect of cardiopulmonary bypass on systemic release of neutrophil elastase and tumor necrosis factor. J Thorac Cardiovasc Surg 1993;15: Finn A, Naik S, Klein N, Levinsky RJ, Strobel S, Elliott M. Interleukin-8 release and neutrophil degranulation after pediatric cardiopulmonary bypass. J Thorac Cardiovasc Surg 1993;15: Kawamura T, Wakusawa R, kada 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 1993;4: 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 1995;23: 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 1995;151: Hashimoto K, Miyamoto H, Suzuki K, et al. Evidence of organ damage after cardiopulmonary bypass. J Thorac Cardiovasc Surg 1993;14: Marty C, Misset B, Tamion F, Fitting C, Carlet J, Cavaillon J. Circulating interleukin-8 concentrations in patients with multiple organ failure of septic and nonseptic origin. Crit Care Med 1994;22:673-9.

6 656 WANG ET AL Ann Thorac Surg ULTRAFILTRATIN IN PEDIATRIC CPB 1996;61: Naik S, Knight A, Elliott MJ. A prospective randomized study of a modified technique of ultrafiltration during pediatric open-heart surgery. Circulation 1991;84(Suppl 3): Journois D, Pouard P, Greeley WJ, Mauriat P, Vouhe P, Safran D. Hemofiltration during cardiopulmonary bypass in pediatric cardiac surgery. Anesthesiology 1994;81: Millar AB, Armstrong L, van der Linden J, et al. Cytokine production and hemofiltration in children undergoing cardiopulmonary bypass. Ann Thorac Surg 1993;56: Andreasson S, Gothberg S, Berggren H, Bengtsson A, Eriksson E, Risberg B. Hemofiltration modifies complement activation after extracorporeal circulation in infants. Ann Thorac Surg 1993;56: Naik S, Elliott MJ. Ultrafiltration. In: Jonas RA, Elliott MJ, eds. Cardiopulmonary bypass in neonates, infants and young children. 1st ed. xford: Butterworth-Heinemann, 1994: Moore RA, Laub GW. Hemofiltration, dialysis, and blood salvage techniques during cardiopulmonary bypass. In: Gravlee GP, Davis RF, Utley JR, eds. Cardiopulmonary bypass: principles and practice. 1st ed. Baltimore: Williams & Wilkins, 1994: Matsushima K, Morishita K, Yoshimura T, et al. Molecular cloning of a human monocyte-derived neutrophil chemotactic factor (MDNCF) and the induction of MDNCF mrna by interleukin 1 and tumor necrosis factor. J Exp Med 1988;167: Weissenbach J, Chernajovsky Y, Zeevi M, et al. Two interferon mrnas in human fibroblasts: in vitro translation and Escherichia coli cloning studies. Proc Natl Acad Sci USA 198;77: REVIEW F RECENT BKS Cardiothoracic Surgical Nursing Edited by Betsy Finkelmeier Philadelphia, Raven Publishers, pp, illustrated, $65. ISBN X Reviewed by John H. Sanders, MD, Jr, and Virginia Beggs, MS We read with great pleasure Betsy Finkelmeier's new book, Cardiothoracic Surgical Nursing, and can recommend it most highly for all in patient care areas who deal with our unique group of patients. Success in any complex endeavor can only occur consistently when there is close teamwork between all involved. Nowhere is this more important than the cardiothoracic service. Ms Finkelmeier draws her knowledge from 18 years of clinical experience at Northwestern University and the University of Virginia. Her chapters are an amalgam of information rather than a single point of view. The scope of the book is quite broad and provides an excellent discussion of pathology, physiology, preoperative evaluation, surgical procedures, postoperative care, and the nature of the devices we use. It has an excellent style and is aimed well above the entry-level nurse. As such, it will not only serve the graduate nurse well, but is aptly suited for medical students and house staff who rotate through our teaching services and want a readable description of what we do. The book is not confined to cardiac surgery, and includes excellent chapters on general thoracic topics such as lung and esophageal surgery, diseases of the chest wall and mediastinnm, pleural drainage, and trauma. There are excellent chapters on congenital heart disease in adults, transplantation, and mechanical assist devices. Many of the topics such as valvular surgery are difficult to find in as concise a form in other texts. Each chapter includes excellent illustrations from a wide variety of sources, decision-making tables, and extensive references. The information is up-to-date and includes blood conservation, myocardial preservation, anesthetic considerations, and other data helpful to current efforts to improve quality of care while reducing length of stay and cost. We can most highly recommend this excellent and comprehensive work to all who participate in the care of our patients: nursing staff, physicians, and therapists. It should be a part of the local libraries on each of our units, and will do much to help every patient for whom we are privileged to care. Lebanon, New Hampshire 1996 by The Society of Thoracic Surgeons Ann Thorac Surg 1996;61: /96/$15. Published by Elsevier Science Inc SSDI (95)1132-3