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Retransfusion of suctioned blood during cardiopulmonary bypass impairs hemostasis
Retransfusion of Suctioned Blood During Cardiopulmonary Bypass Impairs Hemostasis Jacob de Haan, Msc, Piet W. Boonstra, MD, PhD, Stefan H. J. Monnink, MD, Tjark Ebels, MD, PhD, and Willem van Oeveren, PhD Department of Cardiothoracic Surgery and Cardiothoracic Surgery Research Division, University Hospital Groningen, Groningen, the Netherlands
In a previous study we observed extensive clotting and fibrinolysis in blood from the thoracic cavities during cardiopulmonary bypass. We hypothesized that retransfusion of this suctioned blood could impair hemostasis. In this prospective clinical study we investigated the effect of suctioned blood retransfusion on systemic blood activation and on postoperative hemostasis. During coronary artery bypass grafting in 40 patients, suctioned blood was collected separately. It then was retransfused to the patient at the end of the operation (n -- 19), or it was retained (n = 21). During the study, 12 consecutive patients, randomized in two groups of 6, were analyzed for biochemical parameters indicating blood activation and clotting. The immediate and significant increase in circulating concentrations of thrombin-antithrombin III complex, tissue-type plasminogen activator, fibrin degradation products, and free plasma hemoglobin dem-
p
,reservation of hemostasis during cardiopulmonary bypass (CPB) still is an aim of clinical research [1, 2]. One of its main targets is the improvement of the components of the extracorporeal circuit, such as pumps, oxygenators, and filters. Unquestionably, the biocompatibility of the extracorporeal circuit has been improved importantly in recent years [3]. Yet, the clinical results concerning intraoperative and postoperative blood loss are not fully satisfactory. Therefore, other substantial blood-damaging mechanisms, besides the extracorporeal circuit, might be held responsible for the deteriorated hemostasis during and after CPB. An interesting phase during CPB in this regard concerns the period after release of the aortic cross-clamp, which is associated with a high level of blood activation. This blood activation is characterized by the circulation of increased concentrations of bioactive products originating from clotting, fibrinolysis, and blood cell damage [4]. Possible explanations include the effect of reperfusion of heart and lungs, rewarming of the patient [5], and the retransfusion of suctioned blood [6]. This suctioned blood originates from the oozing wound sites in the thorax, collects in pleural and pericardial spaces, and is
onstrated the effect of suctioned blood retransfusion. Moreover, the increased concentrations of thrombinantithrombin III complex and fibrin degradation products indicated renewed systemic clotting and fibrinolysis as a direct result of the retransfusion of suctioned blood. Concentrations of all indicators mentioned remained significantly lower in the retainment group. The clinical data showed that retainment of suctioned blood resulted in significantly decreased postoperative blood loss (822 mL in the retransfusion group versus 611 mL in the retainment group; p < 0.05) and similar or even reduced consumption of blood products (513 versus 414 mL red blood cell concentrate and 384 versus 150 mL singledonor plasma; both not significant). We conclude that retransfusion of highly activated suctioned blood during cardiopulmonary bypass exacerbates wound bleeding.
(Ann Thorac Surg 1995;59:901-7)
retransfused by suction via the cardiotomy reservoir of the heart-lung machine. Because all these processes coincide, separate contribution of these processes to the blood activation and postoperative hemostasis could not be distinguished. In a controlled clinical study we altered the technique of retransfusion of suctioned blood and assessed the effect on hemostasis by determination of postoperative blood loss and total consumption of blood products such as red blood cell concentrates (RBC) and single-donor plasma (SDP). Two groups of patients submitted for elective coronary artery bypass grafting were compared: one group in which the suctioned blood was retransfused immediately after release of the aortic cross-clamp and the other group in which the suctioned blood was retained. During the study, 12 consecutive patients, randomized to 6 in each group, were analyzed for plasma components indicating clotting, fibrinolysis, and red blood cell damage, by collecting samples from the circulation and suctioned blood. Material and M e t h o d s
Patients Accepted for publication Dec 15, 1994. Address reprint requests to Dr van Oeveren, BloodInteractionResearch, Cardiothoracic SurgeryResearch Division, Universi~ Hospital Groningen, Bloemsingel10, 9712KZ Groningen, the Netherlands. © 1995 by The Society of Thoracic Surgeons
After informed consent was obtained 40 patients subjected to primary coronary artery bypass grafting with an expected CPB time of less than 120 minutes entered the study. None of the patients was more than 75 years old or 0003-4975/95/$9.50 0003-4975(95)00012-A
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DE H A A N ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
had evidence of severe heart failure, renal or hepatic dysfunction, or a bleeding disorder. None of the patients was treated with drugs affecting the clotting system within 5 days before the operation. Exclusion criteria and drop outs concerned CPB times longer than 120 minutes. The study was approved (May 1993) by the medical ethical committee of the hospital. The patients were assigned to one of two study groups: retransfusion of suctioned blood (retransfusion; n = 19) or retainment of suctioned blood (retainment; n = 21). During the ongoing study 12 consecutive patients were randomized prospectively to one of the two groups and sampled for further biochemical analysis.
Operative and Anesthetic Techniques After premedication with diazepam (10 to 15 rag), anesthesia was induced with sulfentanyl (1 to 3 /zg/kg) and midazolam (1 to 2 mg/kg), and muscle relaxation was induced with pancuronium bromide (0.1 mg/kg). Ventilation was controlled by a volume-controlled respirator with an oxygen/air mixture. Anesthesia was sustained with sulfentanyl and midazolam infusion. Cefamandol (2 g) and dexamethasone (1 mg/kg) were administered preoperatively. Before cannulation, bovine heparin (300 IU/kg; Leo, Emmen, the Netherlands) was injected. The activated coagulation time was determined in every patient 5 minutes before the start of CPB and at regular intervals during CPB (International Technidyne Co, Edison, NJ). The activated coagulation time was confirmed to be greater than 400 seconds throughout CPB in every patient. Whenever an activated coagulation time was less than 400 seconds additional heparin (100 IU/kg) was given. The ECC consisted of a flat membrane oxygenator with an integrated cardiotomy reservoir including a 40-/zm filter (Cobe Excell; COBE Laboratories Inc, Arvada, CO), and polyvinyl chloride tubing. The circuit was primed with 2,000 mL of oxypolygelatin (Gelifundol; Biotest Pharma GmbH, Dreiech, Germany) and 1,500 IU of bovine heparin (Leo). Cardiopulrnonary bypass was performed with moderate hypothermia (27°C nasopharyngeal temperature) with a pump flow of 2.4 L • m -2 • min 1, maintaining a mean arterial pressure of 50 to 60 mm Hg. Myocardial preservation during aortic clamping was implemented with 1 L of St. Thomas' Hospital cardioplegic solution (4°C) injected into the aortic root. After CPB, heparin was neutralized by protamine chloride (3 mg/kg; Hoffman-Laroche bv, Mijdrecht, the Netherlands). During aortic cross-clamping, the aortic root was vented by a shunt between the aortic root and the venous return line of the heart-lung machine. Topical cooling of the myocardium was achieved with a cold (4°C) saline solution. The blood that gradually oozed from the surgical field into the pericardial and pleural cavities was aspirated by a sucker and collected in a separate plastic polyvinyl chloride blood transfer bag connected to the suction roller pump. In the retransfusion group, the contents of the blood transfer bag were retransfused gradually via the cardiotomy reservoir. In the retainment group the suctioned
A n n Thorac S u r g 1995;59:901-7
blood was not retransfused during the operation. In case of immediate blood transfusion requirement during the operation, the collecting bag could be discharged immediately to the cardiotomy reservoir for rapid transfusion.
Blood Loss and Transfusion of Blood Products Operative blood loss was assessed by measuring the weight of the separate collection bag before and after collection of the suctioned blood. Postoperative blood loss was assessed by measuring the blood volume collected from mediastinal and chest tubes during the first 24 postoperative hours. During the period in the operating room and the first 24 postoperative hours, the transfusion of RBC and SDP also was monitored. Assessment of blood products consumption during intensive care was validated by blinding the intensive care unit staff in their policy to use such products. Transfusion of RBC was indicated by hematocrit values lower than 25%; SDP transfusion was used for volume replacement in case the postoperative infusion volume of colloid plasma expander exceeded 1.5 L. The chest tubes were removed from all patients at about 48 hours after the operation.
Blood Samples Before starting CPB but after heparinization, one blood sample was taken from the radial arterial line for determination of baseline values. Just before the end of aortic occlusion a blood sample was taken from the arterial line of the oxygenator. At 5 minutes after the end of aortic occlusion, blood samples were taken simultaneously from the arterial line of the oxygenator and from the collected suctioned blood. At 5 minutes after all suctioned blood was either retransfused to the circulation of the patient (retransfusion group 1) or retained (retainment group), blood samples were taken from the arterial line of the oxygenator. Finally, a blood sample was taken after the protamine infusion immediately before leaving the operating room. Blood samples were collected in the appropriate collecting medium, stored on ice, and, after determination of cell counts and hematocrit, centrifuged at 1,000 g for 10 minutes to obtain platelet-poor plasma (PPP). The PPP samples were stored at -80°C until further processing.
Laboratory Assays In PPP from blood samples collected in 3.06% sodium citrate containing 1,000 KIU/mL aprotinin and 0.05 U/mL hirudin, we determined the concentration of tissue-type plasminogen activator (t-PA) antigen (enzyme-linked immunosorbent assay [ELISA]; Kabi Diagnostica, Stockholm, Sweden), thrombin-antithrombin III complexes (TAT) (ELISA; Behring, Marburg, Germany), and fibrin degradation products (FbDP) (ELISA; Organon Teknika, Turnhout, Belgium). Heparin concentration was determined by its capacity to inhibit factor Xa activity. In the presence of excess antithrombin III and factor Xa the conversion rate of factor Xa specific substrate was determined ($2222; Kabi Diagnostica). Red blood cell damage was assessed by measuring free hemoglobin concentrations in the plasma samples by a spectrophotometric determination [7].
Ann Thorac Surg 1995;59:901-7
DE H A A N ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
The concentration of fibrin fragments was d e t e r m i n e d in 6 separate patients from the r e t a i n m e n t group, a d d i tionally s a m p l e d i m m e d i a t e l y after start of bypass. In PPP from b l o o d samples, collected in 3.06% s o d i u m citrate a n d 10 m m o l / L EDTA, from circulation and the pericardial cavity fibrin fragments concentrations were d e t e r m i n e d according to the m e t h o d of W i m a n a n d R&nby [8]. Briefly, to excess t-PA, plasminogen, a n d a specific plasmin substrate ($2403; Chromogenix, Stockholm, Sweden) a small a m o u n t of PPP was a d d e d . Because of the t - P A - s t i m u l a t i n g character of fibrin fragments, the turnover of plasmin substrate is indicative of fibrin fragment concentrations in the PPP samples. Concentrations of metabolites in the b l o o d circulation also are influenced b y h e m o d i l u t i o n caused b y factors such as the p u m p - p r i m e solution at the start of bypass, infusion of cardioplegia, a n d topical cooling solution in the pericardial cavity. All data p r e s e n t e d in the figures are not " c o r r e c t e d " for any such dilution effects. Finally, a m o u n t s of free p l a s m a h e m o g l o b i n a n d FbDP in the circulating and suctioned blood were calculated from their concentrations in the blood times the b l o o d volumes. The obtained data were p r o c e s s e d to create the correlation d i a g r a m s of Figure 8.
Statistics All values given are expressed as m e a n + s t a n d a r d error of the mean. Because of the m o d e r a t e n u m b e r of biochemical data, statistical analysis was p e r f o r m e d according to the u n p a i r e d M a n n - W h i t n e y test w h e n two study groups were compared, or the p a i r e d Wilcoxon test w h e n changes within one study group were compared. Because of the skewness of the data, statistical analysis of b l o o d loss a n d RBC a n d SDP use also was achieved b y u n p a i r e d M a n n - W h i t n e y statistics. A p value less than 0.05 was considered significant.
Results
Demographic and Surgical Parameters of the Study Groups All d e m o g r a p h i c and clinical p a r a m e t e r s (body weight, b o d y surface area, age, sex, n u m b e r of anastomoses, bypass material u s e d [vein, internal m a m m a r y artery, or gastroepiploic artery[, a m o u n t of suctioned blood, CPB time, a n d aortic cross-clamp time) were similar for the two study groups (Table 1), allowing comparison of clinical and biochemical data.
Blood Balance All patients e n t e r e d into the study were o p e r a t e d on by the same surgeon (P.W.B.) a n d met the inclusion criteria m e n t i o n e d earlier. H e m o g l o b i n values were similar in both groups at entrance to the intensive care unit, allowing a direct comparison b e t w e e n both study groups with respect to postoperative c o n s u m p t i o n of blood products. The average b l o o d loss during the first 24 postoperative hours in the retransfusion group was significantly higher (p < 0.05) than in the r e t a i n m e n t group (822 + 76 mL versus 611 -- 75 mL). Also the postoperative transfusion
903
Table 1. Demographic Data of the Two Study Groupsa Retransfusion (n = 19) Parameter
Mean
SEM
Retainment (n = 21) Mean
SEM
Time of CPB (min) 70.95 5.51 72.19 3.02 Aortic cross-clamp time (rnin) 43.53 4.03 44.48 2.68 Pericardial suction (mL) 842 110 780 210 Postoperative hemoglobin (g]L) 89.89 3.05 93.38 3.02 a A|I p a r a m e t e r s were analyzed by unpaired Student's t test a n d showed no significant difference between the two study groups. CPB = cardiopulmonary bypass;
SEM - standard error of the mean.
of b l o o d products was higher in the retransfusion group than in the r e t a i n m e n t group although not at a significant level: RBC, 513 +_ 102 mL (13/19 patients of the retransfusion group received RBC) versus 414 _+ 142 mL (9121); and SDP, 384 + 115 mL (9/19) versus 150 + 78 mL (4/21) (Fig 1).
Laboratory Assays T H R O M B I N / A N T I T H R O M B I N III
COMPLEX. Concentrations of TAT r e m a i n e d similar in both groups until after crossclamp release a n d up to the p h a s e of retransfusion of the suctioned b l o o d in one group (Fig 2). After this retransfusion phase, TAT concentrations rose significantly in both study groups: tenfold in the retransfusion group and fourfold in the r e t a i n m e n t group (p < 0.01 for both). The ensuing difference b e t w e e n the two groups also was significant (p < 0.01). In both groups, TAT concentration in the suctioned b l o o d was significantly greater than in the circulating b l o o d at the s a m e time (p < 0.001 for both groups). Concentrations of t-PA antigen increased significantly in the retransfusion group only (p < 0.05), i m m e d i a t e l y after the retransfusion of suctioned b l o o d (Fig 3). The o b s e r v e d increase also resulted in a significantly higher t-PA concentration in the retransfusion group c o m p a r e d with the r e t a i n m e n t group (p < 0.05). After p r o t a m i n e a d m i n istration, however, circulating levels of t-PA again were similar in both groups. Concentrations of t-PA antigen in the suctioned blood were similar to concentrations in the circulating b l o o d at the same time. TISSUE-TYPE P L A S M I N O G E N ACTIVATOR ANTIGEN.
significant increase in FbDP concentrations was o b s e r v e d in both groups up to the phase of retransfusion of the suctioned b l o o d (Fig 4). After this retransfusion phase, FbDP concentrations rose significantly in both study groups: fourfold in the retransfusion group a n d twofold in the r e t a i n m e n t group (p < 0.01 for both). The ensuing differences b e t w e e n the two groups after the retransfusion phase a n d after p r o t a m i n e administration also were significant, associated with p values of less than 0.01 a n d less than 0.05. The concentrations of FbDP in the suctioned blood were significantly higher than in the circulating blood at the same time (p < 0.01 for both groups). FIBRIN DEGRADATION PRODUCTS. N O
904
DE HAAN ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
Fig 1. Blood loss during the first 24 postoperative hours in the retransfusion group (n = 19) was significantly higher than in the retainment group (n = 21) when analyzed by Mann-Whitney unpaired test (p < 0.05). Intraoperative and postoperative transfusion of blood products such as red blood cell concentrate (RBC), in the operating room (OR) and in the intensive care unit (ICU), and single-donor plasma (SDP) was higher in the retransfusion group than in the retainment group, although not at a significant level.
Ann Thorac Surg 1995;59:901-7
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FIBRIN FRAGMENTSOR MONOMERS.Some increase in fibrin fragment activity was observed during CPB (p < 0.05) when compared with preoperative baseline values (Fig 5), especially when hemodilution by pump prime solution was taken into account. Throughout the bypass procedure no significant changes in fibrin fragment lev150 -
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els w e r e o b s e r v e d . C o n c e n t r a t i o n s in the s u c t i o n e d blood, s a m p l e d directly from the thoracic cavity during CPB, e x c e e d e d v a l u e s five t i m e s h i g h e r than in s a m p l e s taken from circulation at the s a m e t i m e (p < 0.01). I-IEPARIN. C o n c e n t r a t i o n s of heparin, after the initial increase in all patients at the o n s e t of CPB, s h o w e d decreasing v a l u e s t h r o u g h o u t the w h o l e CPB procedure, especially in the late p h a s e of CPB (Fig 6). H e p a r i n concentrations in the s u c t i o n e d b l o o d w e r e significantly l o w e r at about one fifth in both g r o u p s c o m p a r e d w i t h the circulating b l o o d at the s a m e t i m e (p < 0.001).
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Fig 2. Concentrations of thrombin-antithrombin III IT/AT lid signiftcantly increased in both study groups during the phase after retransfusion of suctioned blood. The observed changes in TAT concentrations led to significantly higher levels in the retransfusion group (open squares) compared with the retainment group (closed circles) after retransfusion (p < 0.01) and after protamine administration (p < 0.01). In both groups, TAT concentrations in the suctioned blood were significantly higher than at the same time in the circulating blood (p < 0.01 for both groups). Suctioned blood values in the retainment group are indicated by the solid black bar, in the retransfusion group by the striped bar. The open triangle indicates the moment of release of the aortic cross-clamp; the arrow indicates the moment of retransfusion of suctioned blood in the retransfusion group. Error bars indicate the standard error of the mean. (CPB = cardiopulmonary bypass.)
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Fig 3. Tissue plasminogen activator antigen (t-PA) level increased only in the retransfusion group, immediately after the retransfusion of suctioned blood, resulting in a significantly higher concentration compared with the retainment group (p < 0.05). After protamine administration, however, circulating levels of t-PA were similar in both groups. Concentrations of t-PA antigen in the suctioned blood were similar to values in the circulating blood at the same time. (All abbreviations and symbols are similar to those in Figure 2.)
Ann Thorac Surg 1995;59:901-7
DE HAAN ET AL RETRANSFUSIONOF SUCTIONED BLOOD IMPAIRSHEMOSTASIS
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Fig 4. Fibrin degradation products (FbDP) concentrations did not change significantly in both groups up to the phase of retransfusion of the suctioned blood. After this phase, significantly higher circulating concentrations of FbDP were observed in both study groups (p 0.01 in both groups). The observed changes in FbDP concentrations led to significantly higher levels in the retransfusion group compared with the retainment group after retransfusion (p < 0.01) and after protamine administration (p < 0.05). In both groups, FbDP concentrations in the suctioned blood were significantly higher than in the circulating blood at the same time (p ~ 0.01 for both groups). (All abbreviations and symbols are similar to those in Figure 2.)
Fig 6. Plasma levels of heparin decreased significantly and similarly in both groups after release of the aortic cross-clamp, resulting in baseline levels after protamine infusion. In both groups, heparin concentrations in the suctioned blood were significantly less than in the circulating blood at the same time (p < 0.01 for both groups). (All abbreviations and symbols are similar to those in Figure 2.)
Although the h e p a r i n concentrations were significantly lower after the retransfusion phase (p < 0.05 for both groups), no significant difference was o b s e r v e d b e t w e e n the two groups. FREE PLASMA HEMOGLOBIN. Significantly decreasing but similar free p l a s m a h e m o g l o b i n concentrations were observed in both groups up to the p h a s e of retransfusion of the suctioned b l o o d (Fig 7). After this retransfusion phase, free p l a s m a h e m o g l o b i n concentrations rose significantly in both study groups: 300% in the retransfusion 750 -
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group a n d 50% in the r e t a i n m e n t group (p < 0.01 for both). The ensuing differences b e t w e e n the two groups after the retransfusion phase a n d after p r o t a m i n e a d m i n istration also were significant (p < 0.05). Free p l a s m a h e m o g l o b i n concentration in the suctioned b l o o d was significantly higher than in the circulating b l o o d at the same time (p < 0.001 for both groups). Comment
To save autologous blood, retransfusion of suctioned blood during CPB is considered a salutary technique. However, if b l o o d d a m a g e in the thoracic cavity is con-
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Fig 5. Fibrin fragments or monomer (FM) concentrations slightly increased in the phase after start of bypass and in the phase after release of the aortic cross-clamp. The FM concentrations in the pericardial cavity blood were significantly higher than in the circulating blood at the same time (p ~ 0.01). The figure shows individual FM levels in 6 patients from the retainment group, including overall mean and standard error of the mean (SEM) values (striped bars). (Other abbreviations and symbols are similar to Figure 2.)
Fig 7. Free plasma hemoglobin (Free Hb) concentrations did not increase significantly in both groups up to the phase of retransfusion of the suctioned blood. After this phase, significantly higher circulating concentrations of Free Hb were observed in both study groups (p < 0.01 in both groups). The observed changes in Free Hb concentrations led to significantly higher levels in the retransfusion group compared with the retainment group after retransfusion (p < 0.05) and after protamine administration (p < 0.05). In both groups, Free Hb concentrations in the suctioned blood were significantly higher than in the circulating blood at the same time (p ~ 0.01 for both groups). (All abbreviations and symbols are similar to those in Figure 2.)
906
DE H A A N ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
Fig 8. Scatter diagrams for Free plasma hemoglobin (FreeHb) (A) and fibrin degradation products (FbDP) (13), showing the highly significant correlation between infused amounts and observed increase in circulating amounts. The Free-Hb data demonstrate the lack qf any further hemolysis resulting from the retransfusion, whereas the FbDP data indicate additional and renewed systemic activation of fibrinolysis. The dashed lines illustrate the expected correlation if only dilution with circulating blood would determine the final circulating concentrations after retransfusion.
Ann Thorac Surg 1995;59:901-7
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siderable and retransfusion of this blood can impair hemostasis and cause a bleeding disorder, this drive for blood saving could induce exactly the opposite effect. In this study we showed unequivocally that retransfusion of suctioned blood is potentially hazardous for impairing hemostasis. Retainment of this highly activated blood preserved hemostasis, which was demonstrated by the significantly reduced postoperative blood loss. Donor blood requirement was not statistically significantly reduced, but the mere fact that retainment of suctioned blood during the operation did not cause additional d e m a n d for blood products indicates the doubtful hematologic benefits of suctioned blood retransfusion. Furthermore, suctioned blood is highly activated blood, especially with regard to clotting and fibrinolysis. Two key factors in these processes are expressed in the thoracic cavity on or by the damaged pericardial and pleural tissue: tissue factor, a strong stimulus for the extrinsic clotting system [9], and t-PA, a potent activator of the fibrinolytic system [10, 11]. As in an earlier study [4], we demonstrated extremely high concentrations of clotting and fibrinolysis metabolites in the suctioned blood. Compared with concentrations of the metabolites in the systemic circulation at that time, concentrations in the suctioned blood were up to 40 times (TAT and FbDP) greater. Moreover, hemolysis in the suctioned blood also was increased significantly, demonstrating once more the blood damage in the pericardial cavity. Heparin concentrations in the suctioned blood were much lower than in circulation, suggesting either heparin binding to nonplasma components such as platelets or debris [12], or increased heparin consumption by platelet factor 4 activity [13]. After retransfusion of suctioned blood proportionally increased levels of free plasma hemoglobin were observed in the circulating blood, as demonstrated by the
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correlation between free plasma hemoglobin values in the suctioned blood and free plasma hemoglobin levels in circulation (Fig 8A). This leaves the conclusion that the retransfusion is not inducing additional hemolysis. However, the increased concentrations of circulating t-PA, TAT, and FbDP after retransfusion are higher than can be explained by the mere infusion of suctioned blood (Fig 8B, FbDP data; data for t-PA and TAT are similar). Hence, an additional mechanism responsible for renewed clotting and fibrinolysis in the blood of retransfused patients must exist. Because heparin concentration in the suctioned blood is about 20% of that in the systemic circulation, we have to consider the possibility that clotting inhibition is not sufficient, and that thrombin is infused during the retransfusion process. In vitro testing of plasma samples from the suctioned blood confirmed the presence of active thrombin, in contrast to the lack of thrombin activity in samples collected from circulation. We hypothesize that this active thrombin is present on soluble fibrin fragments or fibrin m o n o m e r s in suctioned blood. It has been shown that thrombin remains irreversibly b o u n d to these fibrin fragments [14] and can be recirculated as an active enzyme. Moreover, thrombin b o u n d to fibrin fragments is poorly accessible to its inhibitor, antithrombin IlI [15]. In our study we demonstrated high concentrations of fibrin fragments in suctioned blood. The infusion into the circulation of fibrin fragments therefore is likely to induce renewed formation of thrombin, which could account for the observed increase of TAT concentration. Whether the observed TAT increase is related to an active systemic clotting process remains doubtful, although some initial effects immediately after retransfusion cannot be excluded. One of these local effects could be illustrated by the significant increase in circulating t-PA antigen in the retransfused patients, as
Ann Thorac Surg 1995;59:901-7
DE HAANET AL RETRANSFUSIONOF SUCT1ONEDBLOOD IMPAIRSHEMOSTASIS
t h r o m b i n is one of the most potent stimulators of t-PA release [161. In addition to activation of the clotting system, fibrin fragments also activate t-PA [17] a n d thus fibrinolysis. This was visualized in the suctioned blood by the high FbDP levels. Also, an e n h a n c e d fibrinolysis is to be expected after retransfusion, b e c a u s e fibrinolysis is mainly d e p e n d e n t on p l a s m i n o g e n activation by t-PA in association with fibrin or fibrin m o n o m e r s [17]. As t-PA concentrations were increased in both groups from the initiation of CPB a n d because fibrin fragments were retransfused from suctioned blood. A comparable situation was found d u r i n g retransfusion of postoperative drained blood in which r e n e w e d fibrinolysis and a significant correlation b e t w e e n postoperative FDP levels and postoperative blood loss were observed [18]. Likewise, our present data indicate that by retransfusion of suctioned blood the fibrinolytic activity in circulation is enhanced, causing impaired hemostasis. These findings also indicate that use of aprotinin could have two effects. Because of aprotinin's potential to preserve hemostasis, the a m o u n t of suctioned blood most likely will be reduced, allowing one more easily to discard this blood [19l, Moreover, the inhibition of fibrinolysis by aprotinin will reduce the d a m a g i n g effects of suctioned blood if it is retransfused. Finally, as a result of the technical set-up of the study, we demonstrated that reperfusion of heart a n d lungs after release of the aortic cross-clamp does not result in increased circulating concentrations of ischemia-related products such as t-PA. In conclusion, we demonstrated that r e t a i n m e n t of suctioned blood during coronary artery bypass grafting decreases the postoperative blood loss a n d diminishes the blood activation as observed in the control group with c o n v e n t i o n a l retransfusion of suctioned blood. Therefore we believe that during uncomplicated elective coronary artery bypass grafting a m o u n t s of suctioned blood unsuitable for processing in a cell-saving device should be discarded, a n d a m o u n t s that are suitable for such processing should be washed a n d retransfused. In particular, the increasing use of aspirin and consequently higher blood loss during CPB [20] is an indication that cell-saving during CPB could be appropriate more frequently. We express our gratitude to all co-workers in the Department of Cardiothoracic Surgery and Research, the Department of Anaesthesiology, the Bloodbank Groningen-Drenthe, and the Division of Extracorporeal Circulation for their skills and efforts in performing this study.
907
References 1. Harker LA. Bleeding after cardiopulmonary bypass. N Engl J Med 1986;314:1446-7. 2. Edmunds LH Jr. The sangreal. J Thorac Cardiovasc Surg 1985;90:1-6. 3. Videm V, Mollnes TE, Garred P, Svennevig JL. Biocompatibility of extracorporeal circulation. J Thorac Cardiovasc Surg 1991;101:654-60. 4. Tabuchi N, de Haan J, Boonstra PW, van Oeveren W. Activation of fibrinolysis in the pericardial cavity during cardiopulmonary bypass. J Thorac Cardiovasc Surg 1993;106: 828-33. 5. Phillips R, Skov P. Rewarming and cardiac surgery: a review. Heart Lung 1988;17:511-20. 6. Okies JE, Goodnight SH, Litchford B, Connell RS, Starr A. Effects of infusion of cardiotomy suction blood during extracorporeal circulation for coronary artery surgery. J Thorac Cardiovasc Surg 1977;74:440-4. 7. Harboe H. A method for determination of haemoglobin in plasma by near-ultraviolet spectroscopy. Scand Clin Lab Invest 1959;11:66-70. 8. Wiman B, Ranby M. Determination of soluble fibrin in plasma by a rapid and quantative spectrophotometric assay. Thromb Haemost 1986;55:189-93. 9. Marlar RA, Kleiss AJ, Griffin JH. An alternative extrinsic pathway of human blood coagulation. Blood 1982;60:1353-9. 10. Van Hinsbergh VWM, Kooistra T, Scheffer MA, van Bockel JH, van Muijen GNP. Characterization and fibrinolytic properties of human omental tissue mesothelial cells. Comparison with endothelial cells. Blood 1990;75:1490-7. 11. Collen D. Human tissue-type plasminogen activator. Circulation 1985;72:18-20. 12. Brace LD, Fareed J. An objective assessment of the interaction of heparin and its fractions with human platelets. Semin Thrornb Hemost 1985;11:190-8. 13. Maccarana M, Lindahl U. Mode of interaction between platelet factor 4 and heparin. Glycobiology 1993;3:271-7. 14. Banninger H, Lammle B, Furlan M. Binding of alphathrombin to fibrin depends on the quality of the fibrin network. Biochem J 1994;298:157-63. 15. Hogg PhJ, Jackson CM. Fibrin monomer protects thrombin from inactivation by heparin-anfithrombin III: implications for heparin efficacy. Proc Natl Acad Sci USA 1989;86:3619-23. 16. Dichek D, Quertermous T. Thrombin regulation of mRNA levels of tissue plasminogen activator and plasminogen activator inhibitor-1 in cultured human umbilical vein endothelial cells. Blood 1989;74:222-8. 17. Hoylaerts M, Rijken HR, Collen D. Kinetics of the activation of plasminogen by human tissue plasminogen activator: role of fibrin. J Biol Chem 1982;257:2912-9. 18. De Haan J, Sch/Snberger J, Haan J, van Oeveren W, Eijgelaar A. Tissue-type plasminogen activator and fibrin monomers synergistically cause platelet dysfunction during retransfusion of shed blood after cardiopulmonary bypass. J Thorac Cardiovasc Surg 1993;106:1017-23. 19. Harder PH, Eijsma L, Roozendaal KJ, van Oeveren W, Wildevuur CRH. Aprotinin reduces intraoperative and postoperative blood loss in membrane oxygenator cardiopulmonary bypass. Ann Thorae Surg 1991;52:936-41. 20. Gay WA. Aspirin, blood loss, and transfusion. Ann Thorac Surg 1990;50:425-8.
In a previous study we observed extensive clotting and fibrinolysis in blood from the thoracic cavities during cardiopulmonary bypass. We hypothesized that retransfusion of this suctioned blood could impair hemostasis. In this prospective clinical study we investigated the effect of suctioned blood retransfusion on systemic blood activation and on postoperative hemostasis. During coronary artery bypass grafting in 40 patients, suctioned blood was collected separately. It then was retransfused to the patient at the end of the operation (n -- 19), or it was retained (n = 21). During the study, 12 consecutive patients, randomized in two groups of 6, were analyzed for biochemical parameters indicating blood activation and clotting. The immediate and significant increase in circulating concentrations of thrombin-antithrombin III complex, tissue-type plasminogen activator, fibrin degradation products, and free plasma hemoglobin dem-
p
,reservation of hemostasis during cardiopulmonary bypass (CPB) still is an aim of clinical research [1, 2]. One of its main targets is the improvement of the components of the extracorporeal circuit, such as pumps, oxygenators, and filters. Unquestionably, the biocompatibility of the extracorporeal circuit has been improved importantly in recent years [3]. Yet, the clinical results concerning intraoperative and postoperative blood loss are not fully satisfactory. Therefore, other substantial blood-damaging mechanisms, besides the extracorporeal circuit, might be held responsible for the deteriorated hemostasis during and after CPB. An interesting phase during CPB in this regard concerns the period after release of the aortic cross-clamp, which is associated with a high level of blood activation. This blood activation is characterized by the circulation of increased concentrations of bioactive products originating from clotting, fibrinolysis, and blood cell damage [4]. Possible explanations include the effect of reperfusion of heart and lungs, rewarming of the patient [5], and the retransfusion of suctioned blood [6]. This suctioned blood originates from the oozing wound sites in the thorax, collects in pleural and pericardial spaces, and is
onstrated the effect of suctioned blood retransfusion. Moreover, the increased concentrations of thrombinantithrombin III complex and fibrin degradation products indicated renewed systemic clotting and fibrinolysis as a direct result of the retransfusion of suctioned blood. Concentrations of all indicators mentioned remained significantly lower in the retainment group. The clinical data showed that retainment of suctioned blood resulted in significantly decreased postoperative blood loss (822 mL in the retransfusion group versus 611 mL in the retainment group; p < 0.05) and similar or even reduced consumption of blood products (513 versus 414 mL red blood cell concentrate and 384 versus 150 mL singledonor plasma; both not significant). We conclude that retransfusion of highly activated suctioned blood during cardiopulmonary bypass exacerbates wound bleeding.
(Ann Thorac Surg 1995;59:901-7)
retransfused by suction via the cardiotomy reservoir of the heart-lung machine. Because all these processes coincide, separate contribution of these processes to the blood activation and postoperative hemostasis could not be distinguished. In a controlled clinical study we altered the technique of retransfusion of suctioned blood and assessed the effect on hemostasis by determination of postoperative blood loss and total consumption of blood products such as red blood cell concentrates (RBC) and single-donor plasma (SDP). Two groups of patients submitted for elective coronary artery bypass grafting were compared: one group in which the suctioned blood was retransfused immediately after release of the aortic cross-clamp and the other group in which the suctioned blood was retained. During the study, 12 consecutive patients, randomized to 6 in each group, were analyzed for plasma components indicating clotting, fibrinolysis, and red blood cell damage, by collecting samples from the circulation and suctioned blood. Material and M e t h o d s
Patients Accepted for publication Dec 15, 1994. Address reprint requests to Dr van Oeveren, BloodInteractionResearch, Cardiothoracic SurgeryResearch Division, Universi~ Hospital Groningen, Bloemsingel10, 9712KZ Groningen, the Netherlands. © 1995 by The Society of Thoracic Surgeons
After informed consent was obtained 40 patients subjected to primary coronary artery bypass grafting with an expected CPB time of less than 120 minutes entered the study. None of the patients was more than 75 years old or 0003-4975/95/$9.50 0003-4975(95)00012-A
902
DE H A A N ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
had evidence of severe heart failure, renal or hepatic dysfunction, or a bleeding disorder. None of the patients was treated with drugs affecting the clotting system within 5 days before the operation. Exclusion criteria and drop outs concerned CPB times longer than 120 minutes. The study was approved (May 1993) by the medical ethical committee of the hospital. The patients were assigned to one of two study groups: retransfusion of suctioned blood (retransfusion; n = 19) or retainment of suctioned blood (retainment; n = 21). During the ongoing study 12 consecutive patients were randomized prospectively to one of the two groups and sampled for further biochemical analysis.
Operative and Anesthetic Techniques After premedication with diazepam (10 to 15 rag), anesthesia was induced with sulfentanyl (1 to 3 /zg/kg) and midazolam (1 to 2 mg/kg), and muscle relaxation was induced with pancuronium bromide (0.1 mg/kg). Ventilation was controlled by a volume-controlled respirator with an oxygen/air mixture. Anesthesia was sustained with sulfentanyl and midazolam infusion. Cefamandol (2 g) and dexamethasone (1 mg/kg) were administered preoperatively. Before cannulation, bovine heparin (300 IU/kg; Leo, Emmen, the Netherlands) was injected. The activated coagulation time was determined in every patient 5 minutes before the start of CPB and at regular intervals during CPB (International Technidyne Co, Edison, NJ). The activated coagulation time was confirmed to be greater than 400 seconds throughout CPB in every patient. Whenever an activated coagulation time was less than 400 seconds additional heparin (100 IU/kg) was given. The ECC consisted of a flat membrane oxygenator with an integrated cardiotomy reservoir including a 40-/zm filter (Cobe Excell; COBE Laboratories Inc, Arvada, CO), and polyvinyl chloride tubing. The circuit was primed with 2,000 mL of oxypolygelatin (Gelifundol; Biotest Pharma GmbH, Dreiech, Germany) and 1,500 IU of bovine heparin (Leo). Cardiopulrnonary bypass was performed with moderate hypothermia (27°C nasopharyngeal temperature) with a pump flow of 2.4 L • m -2 • min 1, maintaining a mean arterial pressure of 50 to 60 mm Hg. Myocardial preservation during aortic clamping was implemented with 1 L of St. Thomas' Hospital cardioplegic solution (4°C) injected into the aortic root. After CPB, heparin was neutralized by protamine chloride (3 mg/kg; Hoffman-Laroche bv, Mijdrecht, the Netherlands). During aortic cross-clamping, the aortic root was vented by a shunt between the aortic root and the venous return line of the heart-lung machine. Topical cooling of the myocardium was achieved with a cold (4°C) saline solution. The blood that gradually oozed from the surgical field into the pericardial and pleural cavities was aspirated by a sucker and collected in a separate plastic polyvinyl chloride blood transfer bag connected to the suction roller pump. In the retransfusion group, the contents of the blood transfer bag were retransfused gradually via the cardiotomy reservoir. In the retainment group the suctioned
A n n Thorac S u r g 1995;59:901-7
blood was not retransfused during the operation. In case of immediate blood transfusion requirement during the operation, the collecting bag could be discharged immediately to the cardiotomy reservoir for rapid transfusion.
Blood Loss and Transfusion of Blood Products Operative blood loss was assessed by measuring the weight of the separate collection bag before and after collection of the suctioned blood. Postoperative blood loss was assessed by measuring the blood volume collected from mediastinal and chest tubes during the first 24 postoperative hours. During the period in the operating room and the first 24 postoperative hours, the transfusion of RBC and SDP also was monitored. Assessment of blood products consumption during intensive care was validated by blinding the intensive care unit staff in their policy to use such products. Transfusion of RBC was indicated by hematocrit values lower than 25%; SDP transfusion was used for volume replacement in case the postoperative infusion volume of colloid plasma expander exceeded 1.5 L. The chest tubes were removed from all patients at about 48 hours after the operation.
Blood Samples Before starting CPB but after heparinization, one blood sample was taken from the radial arterial line for determination of baseline values. Just before the end of aortic occlusion a blood sample was taken from the arterial line of the oxygenator. At 5 minutes after the end of aortic occlusion, blood samples were taken simultaneously from the arterial line of the oxygenator and from the collected suctioned blood. At 5 minutes after all suctioned blood was either retransfused to the circulation of the patient (retransfusion group 1) or retained (retainment group), blood samples were taken from the arterial line of the oxygenator. Finally, a blood sample was taken after the protamine infusion immediately before leaving the operating room. Blood samples were collected in the appropriate collecting medium, stored on ice, and, after determination of cell counts and hematocrit, centrifuged at 1,000 g for 10 minutes to obtain platelet-poor plasma (PPP). The PPP samples were stored at -80°C until further processing.
Laboratory Assays In PPP from blood samples collected in 3.06% sodium citrate containing 1,000 KIU/mL aprotinin and 0.05 U/mL hirudin, we determined the concentration of tissue-type plasminogen activator (t-PA) antigen (enzyme-linked immunosorbent assay [ELISA]; Kabi Diagnostica, Stockholm, Sweden), thrombin-antithrombin III complexes (TAT) (ELISA; Behring, Marburg, Germany), and fibrin degradation products (FbDP) (ELISA; Organon Teknika, Turnhout, Belgium). Heparin concentration was determined by its capacity to inhibit factor Xa activity. In the presence of excess antithrombin III and factor Xa the conversion rate of factor Xa specific substrate was determined ($2222; Kabi Diagnostica). Red blood cell damage was assessed by measuring free hemoglobin concentrations in the plasma samples by a spectrophotometric determination [7].
Ann Thorac Surg 1995;59:901-7
DE H A A N ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
The concentration of fibrin fragments was d e t e r m i n e d in 6 separate patients from the r e t a i n m e n t group, a d d i tionally s a m p l e d i m m e d i a t e l y after start of bypass. In PPP from b l o o d samples, collected in 3.06% s o d i u m citrate a n d 10 m m o l / L EDTA, from circulation and the pericardial cavity fibrin fragments concentrations were d e t e r m i n e d according to the m e t h o d of W i m a n a n d R&nby [8]. Briefly, to excess t-PA, plasminogen, a n d a specific plasmin substrate ($2403; Chromogenix, Stockholm, Sweden) a small a m o u n t of PPP was a d d e d . Because of the t - P A - s t i m u l a t i n g character of fibrin fragments, the turnover of plasmin substrate is indicative of fibrin fragment concentrations in the PPP samples. Concentrations of metabolites in the b l o o d circulation also are influenced b y h e m o d i l u t i o n caused b y factors such as the p u m p - p r i m e solution at the start of bypass, infusion of cardioplegia, a n d topical cooling solution in the pericardial cavity. All data p r e s e n t e d in the figures are not " c o r r e c t e d " for any such dilution effects. Finally, a m o u n t s of free p l a s m a h e m o g l o b i n a n d FbDP in the circulating and suctioned blood were calculated from their concentrations in the blood times the b l o o d volumes. The obtained data were p r o c e s s e d to create the correlation d i a g r a m s of Figure 8.
Statistics All values given are expressed as m e a n + s t a n d a r d error of the mean. Because of the m o d e r a t e n u m b e r of biochemical data, statistical analysis was p e r f o r m e d according to the u n p a i r e d M a n n - W h i t n e y test w h e n two study groups were compared, or the p a i r e d Wilcoxon test w h e n changes within one study group were compared. Because of the skewness of the data, statistical analysis of b l o o d loss a n d RBC a n d SDP use also was achieved b y u n p a i r e d M a n n - W h i t n e y statistics. A p value less than 0.05 was considered significant.
Results
Demographic and Surgical Parameters of the Study Groups All d e m o g r a p h i c and clinical p a r a m e t e r s (body weight, b o d y surface area, age, sex, n u m b e r of anastomoses, bypass material u s e d [vein, internal m a m m a r y artery, or gastroepiploic artery[, a m o u n t of suctioned blood, CPB time, a n d aortic cross-clamp time) were similar for the two study groups (Table 1), allowing comparison of clinical and biochemical data.
Blood Balance All patients e n t e r e d into the study were o p e r a t e d on by the same surgeon (P.W.B.) a n d met the inclusion criteria m e n t i o n e d earlier. H e m o g l o b i n values were similar in both groups at entrance to the intensive care unit, allowing a direct comparison b e t w e e n both study groups with respect to postoperative c o n s u m p t i o n of blood products. The average b l o o d loss during the first 24 postoperative hours in the retransfusion group was significantly higher (p < 0.05) than in the r e t a i n m e n t group (822 + 76 mL versus 611 -- 75 mL). Also the postoperative transfusion
903
Table 1. Demographic Data of the Two Study Groupsa Retransfusion (n = 19) Parameter
Mean
SEM
Retainment (n = 21) Mean
SEM
Time of CPB (min) 70.95 5.51 72.19 3.02 Aortic cross-clamp time (rnin) 43.53 4.03 44.48 2.68 Pericardial suction (mL) 842 110 780 210 Postoperative hemoglobin (g]L) 89.89 3.05 93.38 3.02 a A|I p a r a m e t e r s were analyzed by unpaired Student's t test a n d showed no significant difference between the two study groups. CPB = cardiopulmonary bypass;
SEM - standard error of the mean.
of b l o o d products was higher in the retransfusion group than in the r e t a i n m e n t group although not at a significant level: RBC, 513 +_ 102 mL (13/19 patients of the retransfusion group received RBC) versus 414 _+ 142 mL (9121); and SDP, 384 + 115 mL (9/19) versus 150 + 78 mL (4/21) (Fig 1).
Laboratory Assays T H R O M B I N / A N T I T H R O M B I N III
COMPLEX. Concentrations of TAT r e m a i n e d similar in both groups until after crossclamp release a n d up to the p h a s e of retransfusion of the suctioned b l o o d in one group (Fig 2). After this retransfusion phase, TAT concentrations rose significantly in both study groups: tenfold in the retransfusion group and fourfold in the r e t a i n m e n t group (p < 0.01 for both). The ensuing difference b e t w e e n the two groups also was significant (p < 0.01). In both groups, TAT concentration in the suctioned b l o o d was significantly greater than in the circulating b l o o d at the s a m e time (p < 0.001 for both groups). Concentrations of t-PA antigen increased significantly in the retransfusion group only (p < 0.05), i m m e d i a t e l y after the retransfusion of suctioned b l o o d (Fig 3). The o b s e r v e d increase also resulted in a significantly higher t-PA concentration in the retransfusion group c o m p a r e d with the r e t a i n m e n t group (p < 0.05). After p r o t a m i n e a d m i n istration, however, circulating levels of t-PA again were similar in both groups. Concentrations of t-PA antigen in the suctioned blood were similar to concentrations in the circulating b l o o d at the same time. TISSUE-TYPE P L A S M I N O G E N ACTIVATOR ANTIGEN.
significant increase in FbDP concentrations was o b s e r v e d in both groups up to the phase of retransfusion of the suctioned b l o o d (Fig 4). After this retransfusion phase, FbDP concentrations rose significantly in both study groups: fourfold in the retransfusion group a n d twofold in the r e t a i n m e n t group (p < 0.01 for both). The ensuing differences b e t w e e n the two groups after the retransfusion phase a n d after p r o t a m i n e administration also were significant, associated with p values of less than 0.01 a n d less than 0.05. The concentrations of FbDP in the suctioned blood were significantly higher than in the circulating blood at the same time (p < 0.01 for both groups). FIBRIN DEGRADATION PRODUCTS. N O
904
DE HAAN ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
Fig 1. Blood loss during the first 24 postoperative hours in the retransfusion group (n = 19) was significantly higher than in the retainment group (n = 21) when analyzed by Mann-Whitney unpaired test (p < 0.05). Intraoperative and postoperative transfusion of blood products such as red blood cell concentrate (RBC), in the operating room (OR) and in the intensive care unit (ICU), and single-donor plasma (SDP) was higher in the retransfusion group than in the retainment group, although not at a significant level.
Ann Thorac Surg 1995;59:901-7
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FIBRIN FRAGMENTSOR MONOMERS.Some increase in fibrin fragment activity was observed during CPB (p < 0.05) when compared with preoperative baseline values (Fig 5), especially when hemodilution by pump prime solution was taken into account. Throughout the bypass procedure no significant changes in fibrin fragment lev150 -
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els w e r e o b s e r v e d . C o n c e n t r a t i o n s in the s u c t i o n e d blood, s a m p l e d directly from the thoracic cavity during CPB, e x c e e d e d v a l u e s five t i m e s h i g h e r than in s a m p l e s taken from circulation at the s a m e t i m e (p < 0.01). I-IEPARIN. C o n c e n t r a t i o n s of heparin, after the initial increase in all patients at the o n s e t of CPB, s h o w e d decreasing v a l u e s t h r o u g h o u t the w h o l e CPB procedure, especially in the late p h a s e of CPB (Fig 6). H e p a r i n concentrations in the s u c t i o n e d b l o o d w e r e significantly l o w e r at about one fifth in both g r o u p s c o m p a r e d w i t h the circulating b l o o d at the s a m e t i m e (p < 0.001).
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Fig 2. Concentrations of thrombin-antithrombin III IT/AT lid signiftcantly increased in both study groups during the phase after retransfusion of suctioned blood. The observed changes in TAT concentrations led to significantly higher levels in the retransfusion group (open squares) compared with the retainment group (closed circles) after retransfusion (p < 0.01) and after protamine administration (p < 0.01). In both groups, TAT concentrations in the suctioned blood were significantly higher than at the same time in the circulating blood (p < 0.01 for both groups). Suctioned blood values in the retainment group are indicated by the solid black bar, in the retransfusion group by the striped bar. The open triangle indicates the moment of release of the aortic cross-clamp; the arrow indicates the moment of retransfusion of suctioned blood in the retransfusion group. Error bars indicate the standard error of the mean. (CPB = cardiopulmonary bypass.)
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Ann Thorac Surg 1995;59:901-7
DE HAAN ET AL RETRANSFUSIONOF SUCTIONED BLOOD IMPAIRSHEMOSTASIS
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Fig 4. Fibrin degradation products (FbDP) concentrations did not change significantly in both groups up to the phase of retransfusion of the suctioned blood. After this phase, significantly higher circulating concentrations of FbDP were observed in both study groups (p 0.01 in both groups). The observed changes in FbDP concentrations led to significantly higher levels in the retransfusion group compared with the retainment group after retransfusion (p < 0.01) and after protamine administration (p < 0.05). In both groups, FbDP concentrations in the suctioned blood were significantly higher than in the circulating blood at the same time (p ~ 0.01 for both groups). (All abbreviations and symbols are similar to those in Figure 2.)
Fig 6. Plasma levels of heparin decreased significantly and similarly in both groups after release of the aortic cross-clamp, resulting in baseline levels after protamine infusion. In both groups, heparin concentrations in the suctioned blood were significantly less than in the circulating blood at the same time (p < 0.01 for both groups). (All abbreviations and symbols are similar to those in Figure 2.)
Although the h e p a r i n concentrations were significantly lower after the retransfusion phase (p < 0.05 for both groups), no significant difference was o b s e r v e d b e t w e e n the two groups. FREE PLASMA HEMOGLOBIN. Significantly decreasing but similar free p l a s m a h e m o g l o b i n concentrations were observed in both groups up to the p h a s e of retransfusion of the suctioned b l o o d (Fig 7). After this retransfusion phase, free p l a s m a h e m o g l o b i n concentrations rose significantly in both study groups: 300% in the retransfusion 750 -
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group a n d 50% in the r e t a i n m e n t group (p < 0.01 for both). The ensuing differences b e t w e e n the two groups after the retransfusion phase a n d after p r o t a m i n e a d m i n istration also were significant (p < 0.05). Free p l a s m a h e m o g l o b i n concentration in the suctioned b l o o d was significantly higher than in the circulating b l o o d at the same time (p < 0.001 for both groups). Comment
To save autologous blood, retransfusion of suctioned blood during CPB is considered a salutary technique. However, if b l o o d d a m a g e in the thoracic cavity is con-
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Fig 5. Fibrin fragments or monomer (FM) concentrations slightly increased in the phase after start of bypass and in the phase after release of the aortic cross-clamp. The FM concentrations in the pericardial cavity blood were significantly higher than in the circulating blood at the same time (p ~ 0.01). The figure shows individual FM levels in 6 patients from the retainment group, including overall mean and standard error of the mean (SEM) values (striped bars). (Other abbreviations and symbols are similar to Figure 2.)
Fig 7. Free plasma hemoglobin (Free Hb) concentrations did not increase significantly in both groups up to the phase of retransfusion of the suctioned blood. After this phase, significantly higher circulating concentrations of Free Hb were observed in both study groups (p < 0.01 in both groups). The observed changes in Free Hb concentrations led to significantly higher levels in the retransfusion group compared with the retainment group after retransfusion (p < 0.05) and after protamine administration (p < 0.05). In both groups, Free Hb concentrations in the suctioned blood were significantly higher than in the circulating blood at the same time (p ~ 0.01 for both groups). (All abbreviations and symbols are similar to those in Figure 2.)
906
DE H A A N ET AL RETRANSFUSION OF SUCTIONED BLOOD IMPAIRS HEMOSTASIS
Fig 8. Scatter diagrams for Free plasma hemoglobin (FreeHb) (A) and fibrin degradation products (FbDP) (13), showing the highly significant correlation between infused amounts and observed increase in circulating amounts. The Free-Hb data demonstrate the lack qf any further hemolysis resulting from the retransfusion, whereas the FbDP data indicate additional and renewed systemic activation of fibrinolysis. The dashed lines illustrate the expected correlation if only dilution with circulating blood would determine the final circulating concentrations after retransfusion.
Ann Thorac Surg 1995;59:901-7
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siderable and retransfusion of this blood can impair hemostasis and cause a bleeding disorder, this drive for blood saving could induce exactly the opposite effect. In this study we showed unequivocally that retransfusion of suctioned blood is potentially hazardous for impairing hemostasis. Retainment of this highly activated blood preserved hemostasis, which was demonstrated by the significantly reduced postoperative blood loss. Donor blood requirement was not statistically significantly reduced, but the mere fact that retainment of suctioned blood during the operation did not cause additional d e m a n d for blood products indicates the doubtful hematologic benefits of suctioned blood retransfusion. Furthermore, suctioned blood is highly activated blood, especially with regard to clotting and fibrinolysis. Two key factors in these processes are expressed in the thoracic cavity on or by the damaged pericardial and pleural tissue: tissue factor, a strong stimulus for the extrinsic clotting system [9], and t-PA, a potent activator of the fibrinolytic system [10, 11]. As in an earlier study [4], we demonstrated extremely high concentrations of clotting and fibrinolysis metabolites in the suctioned blood. Compared with concentrations of the metabolites in the systemic circulation at that time, concentrations in the suctioned blood were up to 40 times (TAT and FbDP) greater. Moreover, hemolysis in the suctioned blood also was increased significantly, demonstrating once more the blood damage in the pericardial cavity. Heparin concentrations in the suctioned blood were much lower than in circulation, suggesting either heparin binding to nonplasma components such as platelets or debris [12], or increased heparin consumption by platelet factor 4 activity [13]. After retransfusion of suctioned blood proportionally increased levels of free plasma hemoglobin were observed in the circulating blood, as demonstrated by the
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correlation between free plasma hemoglobin values in the suctioned blood and free plasma hemoglobin levels in circulation (Fig 8A). This leaves the conclusion that the retransfusion is not inducing additional hemolysis. However, the increased concentrations of circulating t-PA, TAT, and FbDP after retransfusion are higher than can be explained by the mere infusion of suctioned blood (Fig 8B, FbDP data; data for t-PA and TAT are similar). Hence, an additional mechanism responsible for renewed clotting and fibrinolysis in the blood of retransfused patients must exist. Because heparin concentration in the suctioned blood is about 20% of that in the systemic circulation, we have to consider the possibility that clotting inhibition is not sufficient, and that thrombin is infused during the retransfusion process. In vitro testing of plasma samples from the suctioned blood confirmed the presence of active thrombin, in contrast to the lack of thrombin activity in samples collected from circulation. We hypothesize that this active thrombin is present on soluble fibrin fragments or fibrin m o n o m e r s in suctioned blood. It has been shown that thrombin remains irreversibly b o u n d to these fibrin fragments [14] and can be recirculated as an active enzyme. Moreover, thrombin b o u n d to fibrin fragments is poorly accessible to its inhibitor, antithrombin IlI [15]. In our study we demonstrated high concentrations of fibrin fragments in suctioned blood. The infusion into the circulation of fibrin fragments therefore is likely to induce renewed formation of thrombin, which could account for the observed increase of TAT concentration. Whether the observed TAT increase is related to an active systemic clotting process remains doubtful, although some initial effects immediately after retransfusion cannot be excluded. One of these local effects could be illustrated by the significant increase in circulating t-PA antigen in the retransfused patients, as
Ann Thorac Surg 1995;59:901-7
DE HAANET AL RETRANSFUSIONOF SUCT1ONEDBLOOD IMPAIRSHEMOSTASIS
t h r o m b i n is one of the most potent stimulators of t-PA release [161. In addition to activation of the clotting system, fibrin fragments also activate t-PA [17] a n d thus fibrinolysis. This was visualized in the suctioned blood by the high FbDP levels. Also, an e n h a n c e d fibrinolysis is to be expected after retransfusion, b e c a u s e fibrinolysis is mainly d e p e n d e n t on p l a s m i n o g e n activation by t-PA in association with fibrin or fibrin m o n o m e r s [17]. As t-PA concentrations were increased in both groups from the initiation of CPB a n d because fibrin fragments were retransfused from suctioned blood. A comparable situation was found d u r i n g retransfusion of postoperative drained blood in which r e n e w e d fibrinolysis and a significant correlation b e t w e e n postoperative FDP levels and postoperative blood loss were observed [18]. Likewise, our present data indicate that by retransfusion of suctioned blood the fibrinolytic activity in circulation is enhanced, causing impaired hemostasis. These findings also indicate that use of aprotinin could have two effects. Because of aprotinin's potential to preserve hemostasis, the a m o u n t of suctioned blood most likely will be reduced, allowing one more easily to discard this blood [19l, Moreover, the inhibition of fibrinolysis by aprotinin will reduce the d a m a g i n g effects of suctioned blood if it is retransfused. Finally, as a result of the technical set-up of the study, we demonstrated that reperfusion of heart a n d lungs after release of the aortic cross-clamp does not result in increased circulating concentrations of ischemia-related products such as t-PA. In conclusion, we demonstrated that r e t a i n m e n t of suctioned blood during coronary artery bypass grafting decreases the postoperative blood loss a n d diminishes the blood activation as observed in the control group with c o n v e n t i o n a l retransfusion of suctioned blood. Therefore we believe that during uncomplicated elective coronary artery bypass grafting a m o u n t s of suctioned blood unsuitable for processing in a cell-saving device should be discarded, a n d a m o u n t s that are suitable for such processing should be washed a n d retransfused. In particular, the increasing use of aspirin and consequently higher blood loss during CPB [20] is an indication that cell-saving during CPB could be appropriate more frequently. We express our gratitude to all co-workers in the Department of Cardiothoracic Surgery and Research, the Department of Anaesthesiology, the Bloodbank Groningen-Drenthe, and the Division of Extracorporeal Circulation for their skills and efforts in performing this study.
907
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