Ann Thorac Surg 1997;63:64-67
© 1997 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Effect of Aprotinin on Plasma Fibronectin Levels During Cardiopulmonary Bypass
Dhafir M. Al Khudhairi, Ffarcs(i),
Faris Nadeem, Ffarcs(i),
A. M. Mehrun Zuleika, Ffarcs(i),
Arif Hussain, Ffarcs,
Abdelaziz Ahmed, Ffarcs(i),
Mohammed El Sharkawy, Ffarcs(i)
Department of Cardiac Anaesthesia and Intensive Care Unit, Prince Sultan Cardiac Centre, Armed Forces Hospital, Riyadh, Saudi Arabia
Accepted for publication July 18, 1996.
 |
Abstract
|
|---|
Background. Acute depletion of plasma fibronectin levels has been reported during and after cardiopulmonary bypass; degradation of fibronectin by proteolytic enzymes has been suggested as one of the causes. This study was designed to assess the possible preservation of fibronectin levels by aprotinin during cardiopulmonary bypass.
Methods. Plasma fibronectin levels were evaluated in 19 patients undergoing either elective coronary artery bypass grafting or a valvular heart operation. The study was conducted prospectively in a controlled, randomized, double-blinded manner. Nine test patients (group A) received intraoperative, intravenous administration of aprotinin; 10 control patients (group B) received equivalent volume of normal saline solution. Fibronectin levels were measured immediately after induction of anesthesia (as the baseline for the study) and at the following times: after 5 minutes on bypass, after 30 minutes on bypass, immediately before the start of rewarming, and after being off bypass for 5 minutes, but before protamine administration.
Results. Both groups' basic characteristics were very similar. Group A patients were found to have significantly greater fibronectin levels than group B during and immediately after cardiopulmonary bypass (p < 0.002).
Conclusions. Administration of aprotinin intraoperatively appears to result in better preservation of fibronectin levels during cardiopulmonary bypass. Although the mechanism of action of aprotinin as a proteolytic inhibitor remains unclear, it has been suggested that it exerts an inhibiting effect on proteolytic enzymes by forming an aprotinin-proteinase complex. The clinical implications of the greater level of fibronectin achieved by the intraoperative use of aprotinin during cardiopulmonary bypass need further evaluation.
|
Introduction
|
|---|
Fibronectin is a major circulating plasma glycoprotein that is also found on the cell surface and in the extracellular matrix [1]. It is a major nonimmunoglobulin, noncomplement opsonin of the blood; nonimmunoglobulin opsonization of effete autologous tissue and circulating colloidal matter, such as soluble fibrin, is thought to be an important restorative physiologic process [2].
Independent of the surgical injury, cardiopulmonary bypass (CPB) itself is a potent stimulator of fibronectin consumption [3, 4]. A tendency toward recovery has been shown within 48 hours of cardiac operations in adults and after the third postoperative day in children [5]. The decrease in fibronectin level during CPB is not due solely to dilution by the pump prime, but is probably due in part to opsonization of cellular debris generated by the operation and CPB, and also to the cold precipitation of the heparin-fibronectin complex; adsorption onto the tubing of the bypass apparatus may also contribute to the decline [1]. Furthermore, proteases can cleave fibronectin [6]; therefore, an increase in the plasma levels of proteolytic enzymes after CPB may play an important role in the degradation of fibronectin [7].
Aprotinin is a serine proteinase inhibitor with inhibitory effects on human plasmin, trypsin, and plasma and tissue kallikrein [8]. High-dose intraoperative aprotinin has been shown to reduce surgical bleeding significantly during and after cardiac operations with CPB; its value in the reduction of blood loss has been indisputably demonstrated by many cardiac centers [8–11]. This study was designed to assess the possible preservation of fibronectin levels by aprotinin during CPB, in view of its intrinsic proteolytic enzyme inhibitor properties.
|
Patients and Methods
|
|---|
The effect of intraoperative administration of aprotinin on plasma fibronectin levels was evaluated prospectively in 19 patients undergoing elective cardiac operations with CPB, mostly either coronary artery bypass grafting or valvular heart operations. Patients who had evidence of infection or liver disease were excluded from the study. The patients were randomized into two groups: group A, 9 test patients who received aprotinin, and group B, 10 control patients who received normal saline solution instead. The demographic characteristics of the population under study showed no significant difference. The study population and clinical data are shown in Table 1
.
With the agreement of the hospital research committee, informed consent to enter the trial was obtained from patients who were to undergo cardiac operations with CPB. All patients underwent the same standard anesthetic and CPB techniques: anesthesia was induced with fentanyl, 15 µg/kg, and thiopentone, 3.5 mg/kg. Paralysis was achieved with pancuronium, 0.15 mg/kg. Anesthesia was maintained with nitrous oxide, oxygen, and halothane. Between induction of anesthesia and the start of CPB, 2 mL•kg-1•h-1 of Ringer's lactate solution was infused. Hematocrit before CPB was maintained at 34% ± 2%, whereas during CPB it was maintained around 20% ± 2% in both groups. Aprotinin was administered intravenously through a central venous cannula to group A patients as follows: after induction of anesthesia a test dose of 7 mg (5 mL) of aprotinin was given to detect any possible sensitivity, then a loading dose of 280 mg (2 x 106 KIU) of aprotinin was given over a period of 20 minutes. This was immediately followed by an aprotinin infusion of 70 mg/h (5 x 105 KIU/h), which was maintained until the end of the operation. In addition to the intravenous infusion, another 280 mg (2 x 106 KIU) of aprotinin was added to the priming volume of the CPB machine. The pump prime consisted of 1,600 mL of 5% dextrose in 0.2% saline solution, 1 g of methylprednisolone 1.5 g of cefuroxine, and 50 mL of 8.4% sodium bicarbonate solution. There were no diabetic patients in the study population. Heparin, 400 IU/kg, was administered intravenously before the start of CPB and subsequently as required to maintain the activated clotting time greater than 750 seconds. The activated clotting time was measured by a Hemochron 400 coagulation monitor (International Technidyne Corporation, Edison, NJ). The CPB apparatus included a Shiley bubble oxygenator (Shiley Inc, Irvine, CA) and Cobe-Stöckert pump (Stöckert Instrumente GmbH, Munich, Germany). A standard 170 µm filter was used in the circuit. Patients were cooled to 27°C on CPB.
The plasma fibronectin level was measured as the baseline for the study immediately after induction of anesthesia and before any administration of aprotinin; our laboratory reference range is 180 to 622 mg/L for male patients and 135 to 547 mg/L for female patients. Because a previous study by Pourrat and associates [3] revealed no significant differences in fibronectin levels during CPB between coronary artery bypass grafting and heart valve procedures, they were not analyzed separately. Blood samples for fibronectin estimation were drawn from a central venous line at the following times: after 5 minutes on CPB, after 30 minutes on CPB; immediately before the start of rewarming, and after being off CPB for 5 minutes, but before protamine administration.
The samples were collected in ethylenediamine tetraacetic acid tubes containing the proteinase inhibitor aprotinin (500 U) and sent to the laboratory where they were centrifuged and assayed. Fibronectin levels were estimated on the Cobas Bio Centrifugal analyzer (Roche Diagnostic Systems, Basel, Switzerland) by an automated method using the turbidimetric immunoassay principle. Boehringer Mannheim T Fibronection opsonin protein kits (Boehringer Mannheim GmbH, Mannheim, Germany) based on the above principle were used for the estimation.
Data are presented as mean ± standard deviation. Unpaired t test was used for statistical comparison of data.
|
Results
|
|---|
There was no significant difference between the mean basal fibronectin levels in groups A and B (Fig 1). No significant relationship between the duration of CPB and fibronectin levels was demonstrated in either group. The type and volume of supplemental fluid required in each group during CPB also were not significantly different. (Tables 2, 3). The prime contained 1,500 mL of 5% dextrose in 0.2% sodium chloride. Group A plasma fibronectin levels during CPB are shown in Table 2, and those of Group B in Table 3. Figure 1 illustrates the difference in the mean fibronectin levels between the two groups during and 5 minutes after CPB. Five minutes after the start of CPB, mean fibronectin levels decreased to 225 mg/L in group A patients and to 123 mg/L in group B patients (p = 0.002). Group A patients were found to have significantly greater mean fibronectin levels at all the sampling intervals during and after CPB (see Fig 1). Until rewarming, the mean fibronectin levels did not appear to show much change in either group; rewarming back to normothermia resulted in an increase in the fibronectin levels, but still the fibronectin level in group A was significantly greater than that in group B (p = 0.001).
View larger version (38K):
[in this window]
[in a new window]
|
Fig 1. . Fibronectin levels in group A (aprotinin) and group B (no aprotinin). (CPB = cardiopulmonary bypass.)
|
|
View this table:
[in this window]
[in a new window]
|
Table 2. . Fibronectin Levels Before, During, and After Cardiopulmonary Bypass in Patients Who Received Intraoperative Aprotinin (Group A)
|
|
View this table:
[in this window]
[in a new window]
|
Table 3. . Fibronectin Levels Before, During, and After Cardiopulmonary Bypass in Control Patients Who Did Not Receive Intraoperative Aprotinin (Group B)
|
|
|
Comment
|
|---|
The results of this study showed that fibronectin levels decreased dramatically in both groups A (469 to 225 mg/L) and B (462 to 123 mg/L) within 5 minutes of the start of CPB. Clearly, this decrease in fibronectin levels was in large measure caused by initial hemodilution, but the reduction was limited to 53% in the study group, as opposed to 73% in the controls. At this time there was already a significant difference in mean fibronectin levels between the groups, illustrating the immediate action of aprotinin in the preservation of fibronectin in group A. During CPB, plasma fibronectin level was maintained at significantly greater levels in group A than in group B. In both groups, fibronectin levels increased on rewarming to normothermia; this increase could have been due to the release of fibronectin from heparin-fibronectin complex facilitated by the increase in temperature [1]. At the end of CPB, the significantly better preservation of fibronectin continued in the aprotinin group (287 ± 52 mg/L) compared with the controlled group (186 ± 67 mg/L; p < 0.01). No patients in either group attained their basal levels immediately after CPB. There was no correlation between the duration of CPB and concentrations of fibronectin, which is in accord with a previous study by Miholic and associates [12].
Acute depletion of fibronectin levels has been reported during and after CPB [1, 3, 12]. Acute depletion of plasma fibronectin will limit the phagocytic clearance capacity and thus the reticuloendothelial function of the body [6]. The previously described decrease in opsonic activity after CPB may be due to alteration in the fibronectin level, because fibronectin is a major opsonin, marking particulate matter for ingestion by the reticuloendothelial system [1].
Degradation of fibronectin by proteolytic enzymes has been suggested as one of the causes of fibronectin depletion during and after cardiac operations. Haniuda and associates' study [7] demonstrated that perioperative administration of ulinastatin, a trypsin inhibitor, significantly moderated the reduction in plasma fibronectin levels after cardiac operations with CPB. They further proposed that proteolytic enzyme inhibitor may improve the patient's internal environment after a cardiac operation. The mechanism of action of aprotinin as a proteolytic inhibitor remains unclear. It is proposed that it exerts an inhibiting effect on proteolytic enzymes by forming an aprotinin-proteinase complex.
Further evaluation of the extended role of aprotinin in cardiac operations is required. For example, plasma fibronectin deficiency has been claimed to be associated with depressed host defense against infection, thus favoring the onset of septic complications [3]. Brodin and colleagues [13] concluded that low plasma fibronectin concentration is common in early infections, and that the level is related to the severity of the infection. Mosher [14] reported an association between clinical improvement and an increase in fibronectin values. Persistent plasma fibronectin deficiency in selected patients undergoing coronary artery bypass grafting was also associated with a greater incidence of postsurgical complications [6].
The role of aprotinin in attenuating multiple organ failure also requires further evaluation [1, 3]. Fibronectin has also been implicated in the thrombogenicity of biomaterials; decreased levels of the opsonin may alter fibrin and platelet deposition on plastic surfaces, such as the CPB tubing. Decreased fibronectin levels may lead to fibrin polymerization or fibrin collagen binding, or both, and precipitation [15].
Administration of aprotinin intraoperatively appears to result in improved preservation of fibronectin levels during CPB. The impact of this preservation on the clinical results of CPB and the mechanism of this action warrant further investigation.
|
Acknowledgments
|
|---|
We are grateful to our colleagues in the Departments of Cardiac Anaesthesia and Cardiac Surgery for permission to include their patients in this project. We acknowledge the contribution of Masood AI Malki, Clinical Chemistry Division, in the analyses of the samples, Dr William Sawyer for statistical analysis and assistance in the preparation of the manuscript, and Maureen Meek for secretarial assistance.
|
Footnotes
|
|---|
Address reprint requests to Dr Al Khudhairi, Prince Sultan Cardiac Centre, Armed Forces Hospital, PO Box 7897, Riyadh 11159, Saudi Arabia.
|
References
|
|---|
- Gotta AW, Carsons S, Abrams L, Keany AE. Fibronectin levels during cardiopulmonary bypass. N Y State J Med 1987;87:493–6.[Medline]
- Mosher DF, Williams EM. Fibronectin concentration is decreased in plasma of severely ill patients with disseminated intravascular coagulation. J Lab Clin Med 1978;91:729–35.[Medline]
- Pourrat E, Sie PM, Desrez X, et al. Changes in plasma fibronectin levels after cardiac and pulmonary surgery: role of cardiopulmonary bypass. Scand J Thorac Cardiovasc Surg 1985;19:63–7.[Medline]
- Quitt M, Balan E, Froom P, Hornstein L, Aghaj E. Plasma fibronectin levels in patients with coronary artery disease. Isr J Med Sci 1994;30:905–9.[Medline]
- Hackbarth R, Sarnaik AP, Meert K, Deshmukh DR, Arciniegas E. Changes in plasma fibronectin in children after elective repair of congenital heart defects. J Thorac Cadiovasc Surg 1993;105:31–6.[Abstract]
- Saba TM. Fibronectin deficiency following cardiopulmonary bypass. N Y State J Med 1987;87:487–90.[Medline]
- Haniuda M, Morimoto M, Sugenoya A, Iida F. Suppressive effect of ulinastatin on plasma fibronectin depression after cardiac surgery. Ann Thorac Surg 1988;45:171–3.[Abstract]
- Bidstrup BP, Royston D, Sapsford RN, Taylor KM. Reduction in blood loss and blood use after cardiopulmonary bypass in the high dose aprotinin (Trasylol). J Thorac Cardiovasc Surg 1989;97:364–72.[Abstract]
- Fremes SE, Wong BI, Lee E, et al. Metaanalysis of prophylactic drug treatment in the prevention of postoperative bleeding. Ann Thorac Surg 1994;58:1580–8.[Abstract]
- Parolari A, Antona C, Gerometta P, et al. The effect of "high dose" aprotinin and other factors on bleeding and revisions for bleeding in adult coronary and valve operations: an analysis of 2190 patients during five year period (1987–1991). Eur J Cardiothorac Surg 1995;9:77–82.[Abstract]
- Dietrich W, Barankay A, Dilthey G, et al. Reduction of homologous blood requirement in cardiac surgery by intraoperative aprotinin application-clinical experience in 152 cardiac surgical patients. Thorac Cardiovasc Surg 1989;37:92–8.[Medline]
- Miholic J, Graninger W, Havel M, Klepetko W, Laufer G, Sandtner W. Plasma fibronectin, albumin, IgM and total protein during cardiopulmonary bypass. Thorac Cardiovasc Surg 1985;33:176–8.[Medline]
- Brodin B, Briheim G, Cederblad G, Maller R, Schildt B, Ohman S. Plasma fibronectin concentration in suspected septicaemia is related to severity of sepsis. Acta Chir Scand 1986;152:721–6.[Medline]
- Mosher DF. Fibronectin and liver disease [Editorial]. Hepatology 1986;6:1419–21.[Medline]
- Eriksen HO, Molke-Jensen F, Clemmensen I. Plasma fibronectin concentration in patients admitted to intensive care unit. Haematologia (Budap) 1984;17:93–100.[Medline]
This article has been cited by other articles:
|
|
|
|
 
J. Vedin, A. Antovic, A. Ericsson, and J. Vaage
Hemostasis in Off-Pump Compared to On-Pump Coronary Artery Bypass Grafting: A Prospective, Randomized Study
Ann. Thorac. Surg.,
August 1, 2005;
80(2):
586 - 593.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
