Effect of cardiac operation on platelets

Effects of high dose ascorbic acid on haemostasis during and after cardiopulmonary bypass

Observations were made on the changes in platelets, bleeding time and clot retraction and the protective effects of high dose ascorbic acid in 31 patients undergoing cardiopulmonary bypass (CPB). Platelet counts in Group B (receiving ascorbic acid) were higher ( p<0.05) and platelet adhesion and aggregation were significantly lower than in Group A (no ascorbic acid) during perfusion. Platelet numbers and function rose much faster, bleeding time was significantly shorter and clot retraction better in Group B than in Group A postoperatively. These results suggest that ascorbic acid may reduce platelet destruction and depletion during CPB and promote the recovery of the haemostatic mechanism postoperatively.

Haematological effects of a depth absorption arterial line filter during extracorporeal circulation

An arterial line filter (Swank High Flow 6000) was used during extracorporeal circulation (ECC) in 21 of 45 patients undergoing coronary artery bypass grafting, to study haematological effects. The mean age was 60 (41-69) years. All patients had obstructions of at least three coronary artery branches. Average ECC and aortic crossclamp times, drainage via chest tubes until the first day after surgery, total transfusions of blood products and haemolysis did not differ in the two groups. After 90 minutes of ECC, leukocyte counts were significantly lower in the filter group whereas haematocrit, counts of erythrocytes, lymphocytes and platelets, platelet volume, fibrinogen concentration and fibrinopeptide A were similar. Release of β-thromboglobulin and platelet factor 4 were significantly higher in the filter group. No clinically significant adverse haematological effects were observed with use of the arterial line filter, although there were indications of more pronounced platelet damage in the filter group.

C1-esterase inhibitor following cardiopulmonary bypass: evaluation of coagulation parameters - a preliminary report

This study was designed to evaluate the effects of C1-esterase inhibitor (C1-INH) on haemostasis and blood loss in routine cardiopulmonary bypass (CPB). To determine whether or not C1-INH reduces blood loss or transfusion requirements after routine CPB, we randomized 20 patients to receive double-blind either C1-INH (15 IU/kg over 10 minutes intravenously) or placebo following heparin administration. The two groups were similar in age, sex, prior salicylate use and time on CPB.

At 30 minutes from the beginning of CPB and postprotamine, factor XII, factor XI, C1-INH and prekallikrein activity were significantly higher ( p < 0.05) than in the placebo group. No manifestations of hypercoagulability were seen in either group. Despite this haemostatic effect, patients treated with C1-INH had similar postoperative blood loss to the placebo group and similar blood transfusion requirements.

We conclude that routine use of C1-INH in CPB is unwarranted.

An overview of platelet indices and methods for evaluating platelet function in thrombocytopenic patients

Thrombocytopenia is associated with bleeding risk. However, in thrombocytopenic patients, platelet count does not correlate with bleeding risk and other factors are thus likely to contribute to this risk. This review presents currently available platelet-related markers available on automated haematology analysers and commonly used methods for testing platelet function. The test principles, advantages and disadvantages of each test are described. We also evaluate the current literature regarding the clinical utility of the test for prediction of bleeding in thrombocytopenia in haematological and oncological diseases. We find that several platelet-related markers are available, but information about the clinical utility in thrombocytopenia is limited. Studies support that mean platelet volume (MPV) can aid diagnosing the cause of thrombocytopenia and low MPV may be associated with bleeding in thrombocytopenia. Flow cytometry, platelet aggregometry and platelet secretion tests are used to diagnose specific platelet function defects. The flow cytometric activation marker P-selectin and surface coverage by the Cone-and-Plate[let] analyser predict bleeding in selected thrombocytopenic populations. To fully uncover the clinical utility of platelet-related tests, information about the prevalence of platelet function defects in thrombocytopenic conditions is required. Finally, knowledge of the performance in thrombocytopenic samples from patients is essential.

Anticoagulation and coagulation management for ECMO

Advances in extracorporeal membrane oxygenation (ECMO) management have helped to reduce complications compared with its inception but they remain high. The principal causes of mortality and morbidity are bleeding and thrombosis. The nonbiologic surface of an extracorporeal circuit provokes a massive inflammatory response leading to consumption and activation of procoagulant and anticoagulant components. The vast differences in neonatal and adult anticoagulation and transfusion requirements demands tremendous clinical knowledge to provide the best care. Increased use of thrombelastogram will complement other methods currently being used to improved care. Methods to recognize the level of thrombin formation at the bedside could help reduce neurologic complications. ECMO requires a multidisciplinary team approach to achieve the best outcomes.

Intradialytic and postdialytic platelet activation, increased platelet phosphatidylserine exposure and ultrastructural changes in platelets in children with chronic uremia

The present research evaluated the intradialytic and postdialytic changes in platelet factor-4 and beta-thromboglobulin plasma levels by enzyme-linked immunoadsorbent assay method and platelet aggregation by ADP as well as flow cytometric percentage of annexin-V-positive platelets as a measure of phosphatidylserine externalization and ultrastructural examination of platelets in 37 uremic patients on regular hemodialysis and 25 age-matched and sex-matched controls. Platelet factor-4 plasma levels increased, remain consistently high during hemodialysis session (20.24 +/- 3.05 IU/ml after 30 min, P < 0.001 and 23.67 +/- 3.68 IU/ml after 240 min, P < 0.001) and returned to control values (6.10 +/- 1.54 IU/ml) only after 24 h following the end of the session. beta-Thromboglobulin showed a trend similar to that of platelet factor-4. Platelet aggregation by ADP showed reduced function in comparison with controls (69.32 +/- 12.37 versus 91.95 +/- 1.59%, P < 0.001). Flow cytometric percentage of annexin-V-positive platelet was significantly elevated (P < 0.001) in uremic patients when compared with normal controls. Ultrastructural studies of platelets 30 min after starting of dialysis showed degranulation of its granules and at 240 min showed complete degranulation, whereas in the postdialytic phase (12 h after the end of dialysis) refilled alpha-granules started to appear. Positive correlations were found between platelet concentration and platelet factor-4 and beta-thromboglobulin plasma levels during and after dialysis (P < 0.001) and with annexin-V-positive platelets percentage (P < 0.001). In conclusion, activated platelets were found in chronic hemodialysis patients, a finding that may explain why uremic patients often suffer from thrombotic accidents. The platelet activation is associated with exposure of phosphatidylserine on the platelet exterior. Platelet factor-4 and beta-thromboglobulin are released from platelets as a result of a defect in their granules membrane as shown by the electron microscopy, mainly as a consequence of the blood-membrane contact during dialysis, and they return only slowly to control values.

Nonsurgical bleeding diathesis in anemic thrombocytopenic patients: role of temperature, red blood cells, platelets, and plasma-clotting proteins

Research at the Naval Blood Research Laboratory (Boston, MA) for the past four decades has focused on the preservation of red blood cells (RBCs), platelets (PLTs), and plasma-clotting proteins to treat wounded servicemen suffering blood loss. We have studied the survival and function of fresh and preserved RBCs and PLTs and the function of fresh and frozen plasma-clotting proteins. This report summarizes our peer-reviewed publications on the effects of temperature, RBCs, PLTs, and plasma-clotting proteins on the bleeding time (BT) and nonsurgical blood loss. The term nonsurgical blood loss refers to generalized, systemic bleeding that is not corrected by surgical interventions. We observed that the BT correlated with the volume of shed blood collected at the BT site and to the nonsurgical blood loss in anemic thrombocytopenic patients after cardiopulmonary bypass surgery. Many factors influence the BT, including temperature; hematocrit (Hct); PLT count; PLT size; PLT function; and the plasma-clotting proteins factor (F)VIII, von Willebrand factor, and fibrinogen level. Our laboratory has studied temperature, Hct, PLT count, PLT size, and PLT function in studies performed in non-aspirin-treated and aspirin-treated volunteers, in aspirin-treated baboons, and in anemic thrombocytopenic patients. This monograph discusses the role of RBCs and PLTs in the restoration of hemostasis, in the hope that a better understanding of the hemostatic mechanism might improve the treatment of anemic thrombocytopenic patients. Data from our studies have demonstrated that it is important to transfuse anemic thrombocytopenic patients with RBCs that have satisfactory viability and function to achieve a Hct level of 35 vol percent before transfusing viable and functional PLTs. The Biomedical Excellence for Safer Transfusion (BEST) Collaborative recommends that preserved PLTs have an in vivo recovery of 66 percent of that of fresh PLTs and a life span that is at least 50 percent that of fresh PLTs. Their recommendation does not include any indication that preserved PLTs must be able to function to reduce the BT and reduce or prevent nonsurgical blood loss. One of the hemostatic effects of RBC is to scavenge endothelial cell nitric oxide, a vasodilating agent that inhibits PLT function. In addition, endothelin may be released from endothelial cells, a potent vasoconstrictor substance,to reduce blood flow at the BT site. RBCs, like PLTs at the BT site, may provide arachidonic acid and adenosine diphosphate to stimulate the PLTs to make thromboxane, another potent vasoconstrictor substance and a PLT-aggregating substance. At the BT site, the PLTs and RBCs are activated and phosphatidyl serine is exposed on both the PLTs and the RBCs. FVa and FXa, which generate prothrombinase activity to produce thrombin, accumulate on the PLTs and RBCs. A Hct level of 35 vol percent at the BT site minimizes shear stress and reduces nitric oxide produced by endothelial cells. The transfusion trigger for prophylactic PLT transfusion should consider both the Hct and the PLT count. The transfusion of RBCs that are both viable and functional to anemic thrombocytopenic patients may reduce the need for prophylactic leukoreduced PLTs, the alloimmunization of the patients, and the associated adverse events related to transfusion-related acute lung injury. The cost for RBC transfusions will be significantly less than the cost for the prophylactic PLT transfusions.

Perioperative blood transfusion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and The Society of Cardiovascular Anesthesiologists clinical practice guideline

BACKGROUND

A minority of patients having cardiac procedures (15% to 20%) consume more than 80% of the blood products transfused at operation. Blood must be viewed as a scarce resource that carries risks and benefits. A careful review of available evidence can provide guidelines to allocate this valuable resource and improve patient outcomes.

METHODS

We reviewed all available published evidence related to blood conservation during cardiac operations, including randomized controlled trials, published observational information, and case reports. Conventional methods identified the level of evidence available for each of the blood conservation interventions. After considering the level of evidence, recommendations were made regarding each intervention using the American Heart Association/American College of Cardiology classification scheme.

RESULTS

Review of published reports identified a high-risk profile associated with increased postoperative blood transfusion. Six variables stand out as important indicators of risk: (1) advanced age, (2) low preoperative red blood cell volume (preoperative anemia or small body size), (3) preoperative antiplatelet or antithrombotic drugs, (4) reoperative or complex procedures, (5) emergency operations, and (6) noncardiac patient comorbidities. Careful review revealed preoperative and perioperative interventions that are likely to reduce bleeding and postoperative blood transfusion. Preoperative interventions that are likely to reduce blood transfusion include identification of high-risk patients who should receive all available preoperative and perioperative blood conservation interventions and limitation of antithrombotic drugs. Perioperative blood conservation interventions include use of antifibrinolytic drugs, selective use of off-pump coronary artery bypass graft surgery, routine use of a cell-saving device, and implementation of appropriate transfusion indications. An important intervention is application of a multimodality blood conservation program that is institution based, accepted by all health care providers, and that involves well thought out transfusion algorithms to guide transfusion decisions.

CONCLUSIONS

Based on available evidence, institution-specific protocols should screen for high-risk patients, as blood conservation interventions are likely to be most productive for this high-risk subset. Available evidence-based blood conservation techniques include (1) drugs that increase preoperative blood volume (eg, erythropoietin) or decrease postoperative bleeding (eg, antifibrinolytics), (2) devices that conserve blood (eg, intraoperative blood salvage and blood sparing interventions), (3) interventions that protect the patient's own blood from the stress of operation (eg, autologous predonation and normovolemic hemodilution), (4) consensus, institution-specific blood transfusion algorithms supplemented with point-of-care testing, and most importantly, (5) a multimodality approach to blood conservation combining all of the above.

A trial of fresh autologous whole blood to treat dilutional coagulopathy following cardiopulmonary bypass in infants

BACKGROUND

Transfusion of fresh whole blood is superior to blood component therapy in correcting coagulopathies in children following cardiopulmonary bypass (CPB); however, a supply of fresh homologous whole blood is difficult to maintain. We hypothesized that transfusion of fresh autologous whole blood obtained prior to heparinization for CPB and infused following CPB would be associated with improved coagulation function when compared with standard therapy.

METHODS

A total of 32 infants 5-12 kg undergoing noncomplex open cardiac surgery were randomly assigned to either the treatment or control group. In the treatment group, 15 ml x kg(-1) of autologous whole blood was collected into a CPDA bag prior to heparinization while 15 ml x kg(-1) of 5% albumin was infused intravenously. After reversal of heparin, coagulation tests were drawn in both groups, and the autologous whole blood was infused over 20 min in the treatment group.

RESULTS

The treatment group had greater (P < 0.05) improvement in platelet count, prothrombin time, and fibrinogen than the control group.

CONCLUSIONS

We conclude that collection of fresh autologous whole blood prior to heparinization and reinfusion following CPB is associated with greater improvement of coagulation status after CPB in infants.

Platelet activation and PDGF-AB release during dialysis

During hemodialysis the blood-membrane contact causes a release of platelet granule content, which contains Platelet Derived Growth Factor (PDGF-AB). In view of its possible role in accelerated atherosclerotic processes, we evaluated the intra- and post-dialytic changes in PDGF-AB serum levels during hemodialysis sessions performed with Hemophan and Polysulfone membranes. PDGF-AB, PF4, betaTG and MPV levels were determined in the peripheral blood in 30 patients each of whom underwent 6 dialysis sessions: 3 with Hemophan (HE) membrane and 3 with Polysulfone (PS) membrane, interpolated by a wash out session with PS membrane. Blood samples were taken at times 0', 30', 120', 180', 240' during dialysis sessions and at 1, 4 and 20 hours after the end of the session. Statistical analysis was done using the ANOVA one way test and Student's t test PDGF-AB serum levels initially increased and, except for a sharp fall at 120', remained constantly high during HD with both membranes tested, not returning to basal values until 20 hours after the end of the session. PF4, betaTG and MPV all showed a similar trend to PDGF. No statistically significant difference was found between the two membranes tested. PDGF-AB, a powerful growth factor in cells of mesenchymal origin, is released during dialysis mainly as a result of the blood-membrane contact. This we found regardless of the type of dialyzer we tested, and, above all, proved to return very slowly to basal values. We speculate that the release of PDGF-AB could play a part like other atherosclerosis risk-factors in the appearance and worsening of atherosclerotic lesions in hemodialysis patients.

Exposure of procoagulant phospholipids on the surface of platelets in patients undergoing cardiopulmonary bypass using non-coated and heparin-coated extracorporeal circuits

Cardiopulmonary bypass (CPB) is associated with a generalized hemostatic defect, in which platelet dysfunction seems to play a central role. The present study was designed to elucidate whether the potential procoagulant activity of platelets, detected as annexin V binding, was altered during coronary bypass surgery, using non-coated and heparin-coated extracorporeal circuits. Thirty patients undergoing elective coronary artery bypass grafting were prospectively randomized using either a standard untreated extracorporeal circuit (n = 15) or a heparin-treated extracorporeal circuit (n=15). Besides measurement of the procoagulant phospholipid activity, the mediastinal blood loss after surgery, and the blood transfusion requirements were also monitored. CPB induced a decrease in the percentage of activated platelets in whole blood, manifest directly after start of CPB, which was significantly attenuated using a non-treated system. Postoperatively, the percentage of activated platelets recovered in both systems, reaching a point of significance 24 hours after the operation, compared to the values 2 hours after the operation. The differences among the groups for mediastinal blood loss during the first 2 and 24 postoperative hours coincided with the differences in procoagulant phospholipid activity. Furthermore, there was no statistical difference among the groups for blood transfusion requirements. The platelets in both groups showed a significantly lower ability to generate ionomycin-induced procoagulant activity after blood-material interaction when compared to the baseline values. These observations are compatible with the notion that during CPB, irrespective of the heparin coating, platelets become modestly activated.

Autologous blood sequestration using a double venous reservoir bypass circuit and polymerized hemoglobin prime

Cardiac surgery often necessitates transfusion of homologous blood. Hemoglobin based oxygen carrying solutions (HBOCs) transport oxygen, suggesting use in cardiopulmonary bypass. HBOC was used in a novel oxygenator double-reservoir circuit that permits acute sequestration of a portion of the autologous blood volume during bypass. Two groups of seven mongrel dogs each were studied in an experimental bypass model using global myocardial ischemia and cardioplegia protection: HBOC group, initial venous return drained to a separate reservoir and hypothermic bypass was conducted with HBOC containing perfusate in a second bypass reservoir; Control group, crystalloid prime in a conventional circuit. Hemodynamics and metabolic and hematologic parameters were measured before and 60 min after aortic clamp removal and reinfusion of sequestered autologous blood. Blood gases, base excess, hematocrit, total hemoglobin, and platelet counts were measured. In the HBOC group, metabolic acidosis did not occur, and ventricular function was preserved. Net conservation of platelets was noted at study conclusion: control 33+/-13 x 10(3) per mm3 versus HBOC 48+/-13 x 10(3), p < 0.05. HBOC based priming in a double venous reservoir system permits bypass at very low hematocrit, with preservation of cardiac function. Net conservation of the platelet mass occurs, a portion of which is not exposed to the deleterious effects of hypothermia and cardiopulmonary bypass.

Intra- and post-dialytic platelet activation and PDGF-AB release: cellulose diacetate vs polysulfone membranes

BACKGROUND

During haemodialysis the blood-membrane contact causes a release of platelet granule content, which contains platelet-derived growth factor AB (PDGF-AB). In view of the potential role of this in altering biocompatibility during haemodialysis, we evaluated the intra- and post-dialytic changes in PDGF-AB serum levels during haemodialysis sessions performed with cellulose diacetate (CDA) and polysulfone (PS) membranes respectively.

METHODS

PDGF-AB, platelet factor 4 (PF4), beta thromboglobulin (betaTG), and mean platelet volume (MPV) levels were determined in 30 patients, each of whom underwent six dialysis sessions: three with a CDA and three with a PS membrane. Blood samples were taken at times 0, 15, 30, 120, 180, and 240 min during dialysis and at 1, 4, and 20 h after the end of the session. Statistical analysis was performed using a one-way ANOVA and Student's t test.

RESULTS

PDGF-AB at 15 min was increased to +41+/-9% with CDA vs +20+/-5% with PS (P<0.001) from the T0 values, and at 120 min it was +19+/-8% with CDA vs -25+/-9% with PS (P<0.001) from T0 levels. At 240 min it was +95+/-14% with CDA vs +49+/-15% with PS (P<0.001) from the T0 values, returning to basal only 20 h after the end of the session. betaTG at 15 min was +60+/-8% for CDA vs +24+/-7.5% for PS (P<0.001) from the T0 values. PF4 showed a similar trend to betaTG. MPV at 30 min from the start of dialysis was 7.4+/-0.3 fl with CDA and 8+/-0.3 fl with PS (P<0.001), and at 240 min MPV was 7.9+/-0.3 fl with CDA and 8.4+/-0.3 fl with PS (P<0.001).

CONCLUSIONS

Platelet activation and platelet release reactions are lower with PS than with CDA membranes. PDGF-AB, released during and after dialysis, represents a clear biocompatibility marker. Its slow return to basal values and its action on vascular cells make it a potential risk factor for atherosclerosis in uraemic patients.

Platelet function during cardiac surgery and cardiopulmonary bypass with low-dose aprotinin

OBJECTIVE

To determine whether two low-dose regimens of aprotinin influence platelet function.

DESIGN

Prospective, randomized, single-blinded trial.

SETTING

University teaching hospital performing 600 cardiac operations per year.

PARTICIPANTS

Fifty-nine patients scheduled for cardiac surgery undergoing cardiopulmonary bypass (CPB) of expected duration of 60 minutes or more.

INTERVENTIONS

Patients were randomized into three groups. Group C (control) included 21 patients who did not receive aprotinin. In group A2, 17 patients received 14,286 kallikrein inhibitor units (KIU)/kg (2 mg/kg) of aprotinin before surgery, followed by a continuous infusion of 7,143 KIU/kg/h (1 mg/kg/h) until the end of surgery. In group A4, 19 patients received 28,572 KIU/kg (4 mg/kg) of aprotinin before surgery, followed by the same infusion.

MEASUREMENTS AND MAIN RESULTS

Postoperative bleeding and transfusion requirements were significantly less in group A4. Changes in platelet number and function were similar in the three groups. Platelet aggregation was assessed in four periods: before CPB (T1), post-CPB (T2), and 2 hours (T3) and 4 hours (T4) after CPB. Platelet aggregation induced by adenosine diphosphate, 1 and 2 micromol/L; ristocetin, 1 mg/mL; and arachadonic acid (AA), 1.4 mmol/L, decreased at T2 (p < 0.001) in all groups, and for the ristocetin and AA groups, remained at less than baseline values at T3 and T4. In five patients from each group, platelet receptors for glycoprotein IIb-IIIa (GPIIb-IIIa) and expression of platelet activation markers, guanosine monophosphate 140 (GMP-140) and lysosomal protein, were measured by flow cytometry before and after CPB. Modifications in the expression of GPIIb-IIIa were always modest and without statistical significance. Platelet activation markers, GMP-140 or lysosomal protein, nearly doubled from baseline to post-CPB only in the A4 group, whereas they remained stable in both other groups (statistically not significant).

CONCLUSION

The two regimens of aprotinin, both considered low dosage, did not exert a protective effect on platelet function. Neither dose produced changes in platelet GPIIb-IIIa or platelet activation markers. However, bleeding and transfusion needs were decreased.

Platelet aggregation during cardiopulmonary bypass evaluated by a laser light-scattering method

BACKGROUND

In regard to postoperative bleeding, the most important consequence of cardiopulmonary bypass (CPB) is the loss of aggregability. However, the mechanism of platelet aggregation loss during CPB is unclear. Newly developed particle-counting methods that use light scattering can be used to quantify changes in the number of platelet aggregates of different sizes after application of an aggregating stimulus. Using a light-scattering method, we investigated changes in platelet aggregation during cardiac operation.

METHODS

Nineteen patients undergoing CPB were evaluated. Blood samples were obtained before the operation, 1 hour after initiation of CPB, at the end of CPB, at the end of the operation, and on day 1 after the operation. Platelet aggregation after stimulation by 2.5 micromol/L adenosine diphosphate and 2.0 microg/mL collagen was determined; small (9 to 25 microm), medium (25 to 50 microm), and large (50 to 70 microm) aggregates were counted.

RESULTS

Generation of medium and large aggregates after stimulation with adenosine diphosphate and collagen were significantly decreased with CPB, whereas, in spite of hemodilution, the quantity of the small aggregates was maintained at the elevated level.

CONCLUSIONS

These results reflect the fact that CPB does not affect the first phase of aggregation. It suggests that platelet dysfunction associated with CPB is mainly caused by an inhibition in the development of small aggregates into larger aggregates.

Evaluation of platelet function by Sonoclot analysis compared with other hemostatic variables in cardiac surgery

Platelet function can be easily measured as time to peak (TP) by Sonoclot Coagulation & Platelet Function Analyzer (Sienco Inc., Morrison, CO) analysis. However a correlation between Sonoclot analysis and platelet aggregation, which is accepted as a test of platelet function, has not been established. In this study, we compared TP and collagen-induced whole blood platelet aggregation in 15 patients undergoing cardiac surgery. Two or three blood samples were randomly obtained from each patient before and after cardiopulmonary bypass (CPB). Sonoclot analysis, collagen-induced whole blood aggregation, and laboratory measurement (including platelet count and coagulation profile) were measured. Seventy-two samples were obtained (35 before CPB and 37 after CPB). TP was correlated with collagen-induced whole blood aggregation (r = -0.652), platelet count (r = -0.671), fibrinogen level (r = -0.598), prothrombin time (r = 0.394), activated partial thromboplastin time (r = 0.486), and use of CPB (r = 0.380). Significant predictors of TP for multiple linear regression modeling were collagen-induced whole blood aggregation, platelet count, and fibrinogen level (r = 0.742). In conclusion, Sonoclot analysis TP predicts approximate platelet function in patients undergoing cardiac surgery.

IMPLICATIONS

Approximate platelet function can be easily measured as time to peak by Sonoclot analysis. In this study, time to peak was predicted by platelet count, whole blood platelet aggregation, and fibrinogen level for multiple linear regression modeling.

Aprotinin counterbalances an increased risk of peri-operative hemorrhage in CABG patients pre-treated with Aspirin

OBJECTIVE

As Aspirin (ASA) has proven efficacy in preventing patients with CAD from complications related to cardiovascular diseases, most patients scheduled for CABG are treated with ASA therapy. Consequently, impaired hemostasis is a problem in the management of CABG patients. Clinical studies have shown that Aprotinin can reduce bleeding and the use of blood products by 50% in patients both with and without pre-operative ASA therapy. Concerning the combined effect of peri-operative low-dose ASA therapy and intra-operative high-dose Aprotinin therapy, the gathering of additional and prospective data seemed to be necessary.

METHODS

We conducted a double-blind two-centre randomised three-arm study in patients with elective primary CABG surgery. Three groups have been tested, comprising 119 patients in total (group A: ASA + Aprotinin, group B: placebo + Aprotinin, group C: placebo + placebo) to investigate a possible reduction of bleeding in Aprotinin treated patients. For all patients, thromboxane levels were used to identify ASA or placebo treatment.

RESULTS

The post-operative blood loss is significantly reduced by 21% after Trasylol administration (B vs. C; P = 0.009). The unexpected result of this study has been that the pre-treatment with ASA led to a further reduction of 18% (A vs. C; P < 0.0001). The difference between the two Aprotinin groups (A and B) is significant (P = 0. 01) in favour of ASA pre-treatment. Myocardial infarction (MI) had been diagnosed at levels of 1.8% in total (2/113), 2.6% (1/38) in group B and 3.2% (1/31 ) in group C. An additional blinded evaluation of ECG, enzyme levels and clinical status revealed 'definite, probable and possible' MIs of 5% in group A, compared to 16% in group B and 13% in group C, thus providing no evidence for a higher risk of infarction by Aprotinin treatment. When comparing the ASA group to non-ASA pre-treatment, a strong trend towards a reduction in MI rate becomes obvious, from 15% to 5% in favour of the ASA pre-treatment (P = 0.08). Concerning other peri-operative complications, no statistical difference between the groups could be detected.

CONCLUSIONS

A reduction in post-operative blood loss in primary elective CABG surgery with intra-operative Aprotinin treatment could be confirmed. A low-dose ASA treatment combined with a high-dose aprotinin administration during surgery not only neutralized a potentially higher risk of bleeding, but did in fact reduce the post-operative blood loss. The protective effect of ASA on peri-operative MI has been evident through a reduction of MI rate in ASA treated patients.

Platelet protective effect of TAK-029, a novel glycoprotein IIb/IIIa antagonist: an in vitro study

Previous studies have indicated that exposure of fibrinogen receptors associated with the glycoprotein IIb/IIIa complex contributes to platelet loss during cardiopulmonary bypass. TAK-029 is a newly developed reversible, nonpeptide inhibitor of platelet glycoprotein IIb/IIIa receptors. In this study, we tested the platelet preserving effect of TAK-029 in an in vitro model. The methods included the comparison of the release of beta-thromboglobulin (beta-TG) between a TAK-029 group (n = 5) and a control group (n = 5) in a mock circulation under a shear force generated by a centrifugal pump. To evaluate the degree of beta-TG release, deltabeta-TG/deltaT was calculated where deltabeta-TG is the increase in beta-TG and deltaT is the time. The results showed that the value of deltabeta-TG/deltaT in the TAK-029 group was significantly lower than it was in the control group (4.22 +/- 0.27 x 10(2) ng/ml vs. 7.33 +/- 0.66 x 10(2) ng/ml, respectively). In conclusion, TAK-029 reduced the platelet activation under the shear forces of an in vitro model, suggesting that TAK-029 is a potential candidate for platelet protection during cardiopulmonary bypass.

Does the duration of cardiopulmonary bypass or aortic cross-clamp, in the absence of blood and/or blood product administration, influence the IL-6 response to cardiac surgery?

Cardiopulmonary bypass (CPB) induces a systemic inflammatory response characterized by release of proinflammatory cytokines, including interleukin 6 (IL-6). Recent reports suggest that plasma IL-6 is increased after CPB. Previous studies evaluating the influence of duration of CPB and/or aortic cross-clamp time on the release of IL-6 are conflicting. Infusion of blood and blood products during these studies may have influenced plasma concentrations of proinflammatory cytokines by inducing host cell (monocyte) activation and IL-6 release. The purpose of our investigation was to determine, in an environment free from blood and/or blood product administration, the influence of duration of CPB and/or aortic cross-clamp on the magnitude of the IL-6 response in patients undergoing cardiac surgery. We prospectively evaluated plasma IL-6 levels preinduction (T0) and at sternal closure in 16 patients undergoing CPB (coronary artery bypass grafting, n = 9; valvular cardiac surgery, n = 7) to determine whether there is a correlation between the absolute increase in IL-6 and the duration of CPB or aortic cross-clamp time. None of the patients received blood and/or blood products during the study to control for the introduction of additional activated cells and soluble mediators, including IL-6. The results demonstrate that the magnitude of the IL-6 response to CPB is positively correlated with the duration of CPB but not with duration of aortic cross-clamp. It seems that induction of IL-6 release is part of a normal response to CPB and does not depend on activation of host cells during prolonged aortic cross-clamp. The activation or presence of inflammatory cytokines associated with administration of blood and/or blood products could have influenced previously published investigations relating the influence of duration of CPB and/or aortic cross-clamp time to the magnitude of the IL-6 response.

IMPLICATIONS

This study found a positive correlation between the magnitude of the interleukin 6 response to cardiopulmonary bypass and duration of cardiopulmonary bypass (but not duration of aortic cross-clamp) when measurements were made in the absence of blood/blood product transfusion. Future studies evaluating strategies to reduce cytokine responses to cardiopulmonary bypass should therefore control for cardiopulmonary bypass duration.

Effects of depletion of leukocytes and platelets on cardiac dysfunction after cardiopulmonary bypass

BACKGROUND

This study examined the effects of the depletion of leukocytes and platelets from circulated blood on cardiac function after cardiopulmonary bypass in 37 patients who underwent coronary artery bypass grafting or aortic valve replacement.

METHODS

Leukocytes and platelets were removed continuously using a blood cell separator, beginning immediately after the start of the operation and ending 1 hour after the release of the aortic cross-clamp in 19 patients (LPD group), but not in the remaining 18 patients (control group). Blood cell counts and levels of thromboxane B2, 6-keto-prostaglandin F1alpha, leukocyte elastase, complements C3a and C4a, thrombin-antithrombin III complex, and D-dimer were determined periodically during and after the operation. The cardiac index, the difference between the central and peripheral core temperatures, and the doses of catecholamines and vasodilators required to support the circulation in the early postoperative period also were assessed.

RESULTS

Leukocyte and platelet counts and levels of leukocyte elastase, thromboxane B2, thromboxane2/6-ketoprostaglandin F1alpha, thrombin-antithrombin III complex, and D-dimer were significantly lower in the LPD group than in the control group before and after the release of the aortic cross-clamp and during the perioperative period. There were no significant differences in the levels of 6-keto-prostaglandin F1alpha or complements C3a and C4a between the two groups. The catecholamine dose was significantly lower in the LPD group than in the control group (1.1 +/- 2.5 versus 5.0 +/- 5.2 mg/kg, respectively). Fewer patients required the use of nitroprusside as a vasodilator in the LPD group than in the control group (1/19 versus 12/18, respectively).

CONCLUSIONS

The depletion of leukocytes and platelets using a blood cell separator prevents the deterioration of cardiac function after cardiac operations using cardiopulmonary bypass.

Modified ultrafiltration attenuates dilutional coagulopathy in pediatric open heart operations

BACKGROUND

Extreme hemodilution caused by relatively large prime volumes required for cardiopulmonary bypass in infants causes a dilutional coagulopathy, characterized by low concentrations of fibrinogen and other circulating coagulation factors. Modified ultrafiltration results in hemoconcentration and is associated with decreases in postoperative bleeding and transfusion requirements in children. This study was undertaken to quantify the effect of modified ultrafiltration on concentrations of fibrinogen, plasma proteins, and platelets in infants and small children.

METHODS

Twenty patients less than 15 kg were studied. Cardiopulmonary bypass circuits were primed with crystalloid solutions. Red blood cells were added during cardiopulmonary bypass for hematocrits less than 15%. Colloid solutions were not administered. Concentrations of fibrinogen, plasma proteins, and platelets, and hematocrit were measured before cardiopulmonary bypass, before modified ultrafiltration, and after modified ultrafiltration.

RESULTS

Modified ultrafiltration was associated with significant (p < 0.001) increases in hematocrit (19% +/- 6% to 31% +/- 9%), fibrinogen (65 +/- 29 to 101 +/- 45 mg/dL), and total plasma proteins (2.7 +/- 0.3 to 4.9 +/- 0.7 g/dL), but no change (p = 0.129) in platelet count.

CONCLUSIONS

We conclude that modified ultrafiltration significantly attenuates the dilutional coagulopathy associated with cardiopulmonary bypass in infants.

Predictors of early and overall outcome in coronary artery bypass without cardiopulmonary bypass

OBJECTIVE

Cardiopulmonary bypass in coronary artery bypass graft operations may adversely affect the outcome especially in high-risk patients. The purpose of this study is to evaluate results of coronary artery bypass performed without cardiopulmonary bypass, in a relatively high-risk cohort, and to identify predictors of unfavorable outcome.

METHOD

Three hundred and thirteen (313) patients, 246 (79%) of whom had high-risk conditions, who have a coronary anatomy suitable for coronary artery bypass surgery without cardiopulmonary bypass, underwent this procedure between December 1991 and July 1995. Mean number of grafts/patient was 1.8 (1-5), and only 71 patients (23%) received a graft to the circumflex coronary system.

RESULTS

Early unfavorable outcome events included operative mortality (12 patients, 3.8%), nonfatal perioperative myocardial infarction (eight patients, 2.6%), emergency reoperation (three patients, 0.9%), sternal infection (five patients, 1.6%), and nonfatal stroke (two patients, 0.6%). Multivariate analysis revealed angina pectoris class IV (odds ratio 5.4) and age > or = 70 years (odds ratio 5.0) as independent predictors of early mortality. Preoperative risk factors such as repeat coronary artery bypass grafting (50 patients, 16%), ejection fraction < or = 0.35 (85 patients, 27%), acute myocardial infarction (86 patients, 28%), cardiogenic shock (ten patients, 3.2%), chronic renal failure (25 patients, 8%), chronic obstructive pulmonary disease (20 patients, 6%), and peripheral vascular disease (51 patients, 16%) did not increase early mortality. During 33 months of follow-up (range 1-57 months), there were 42 deaths, at least 16 cardiac-related (one and four years actuarial survival of 90% and 76% respectively), and 39 patients (12.5%) in whom angina returned. Calcified aorta (odds ratio 2.6) and old myocardial infarction (odds ratio 1.8) were independent predictors of overall unfavorable events.

CONCLUSIONS

Coronary artery bypass grafting without cardiopulmonary bypass can be performed with relatively low operative mortality in certain high-risk subgroups of patients; however, an increased risk of graft occlusion is a potential disadvantage. This procedure should therefore be considered only for patients with suitable coronary anatomy, in whom cardiopulmonary bypass poses a high risk. Although the risk of stroke is relatively low, the procedure is still hazardous for patients aged 70 years and over.

Aprotinin in aortic surgery requiring profound hypothermia and circulatory arrest

OBJECTIVE

The use of aprotinin in cardiac surgery to improve haemostasis and reduce blood loss particularly in patient groups at increased risk of bleeding is well established. Previous retrospective studies in profound hypothermic surgery have highlighted concerns that in this circumstances aprotinin may paradoxically cause increased bleeding and intravascular thrombosis. We therefore adopted a modified protocol for administering aprotinin, which was not started until cardiopulmonary bypass had been reinstituted after circulatory arrest.

METHODS

Between April 1993 and June 1995, 45 patients underwent 46 thoracic aortic procedures which required hypothermic circulatory arrest; 25 of these were emergencies. All of these patients received aprotinin.

RESULTS

There were five deaths (10.8%) in hospital. Two patients with preoperative oliguric renal failure required postoperative dialysis, and a further six (13%) developed transient renal dysfunction with complete recovery. Two patients suffered postoperative stroke; one from embolisation of a severely diseased aorta, while the other had signs of an acute evolving stroke before surgery. None of the patients suffered acute Q-wave perioperative myocardial infarction. The mean blood loss was 575 ml in the first 12 h, with a mean postoperative transfusion requirement of 1 U blood.

CONCLUSIONS

We cannot implicate aprotinin in increased postoperative blood loss, renal dysfunction or mortality when used with hypothermic circulatory arrest according to this protocol. Elucidating the role of aprotinin in hypothermic circulatory arrest requires a randomised prospective study.

Laboratory evaluation of hemostasis before cardiac operations

BACKGROUND

Several opinions prevail on the necessity and on the choice of laboratory coagulation tests to perform before cardiac operations. This review aims at providing simple and clinically relevant recommendations.

METHODS

The literature on preoperative coagulation testing was reexamined, taking into account the low prevalence of unknown and unsuspected hemorrhagic disease, and the risk of false positive results.

RESULTS

Carefully controlled, randomized trials are lacking but it seems appropriate to perform a few inexpensive tests (platelet count, activated partial thromboplastin time, and prothrombin time), mainly to obtain baseline values for patients who are about to undergo a major hemostatic challenge. A more complete coagulation profile (eg. bleeding time, fibrinogen concentration, thrombin time) should be considered in patients who present with a history of bleeding.

CONCLUSIONS

A careful medical history is the key element to detect a bleeding disorder. Only a very limited coagulation profile should be obtained in asymptomatic patients before cardiac operations.

Coronary artery bypass without cardiopulmonary bypass: analysis of short-term and mid-term outcome in 220 patients

Two hundred twenty patients, preferentially those with high-risk conditions, underwent coronary artery bypass grafting without cardiopulmonary bypass. Early unfavorable outcome events included operative mortality (7 patients, 3.2%), nonfatal perioperative myocardial infarction (6 patients, 2.7%), cerebrovascular accident (1 patient, 0.4%), and sternal infection (3 patients, 1.4%). There were two deaths (13%) among 15 patients with calcified aorta and four (12%) in 33 patients who underwent emergency operation. Multivariate analysis revealed these two risk factors to be the only predictors of early mortality (odds ratios, 8.0 and 9.8, respectively). Preoperative risk factors such as left ventricular dysfunction (ejection fraction < or = 35%) (40 patients, 18%), congestive heart failure (46 patients, 21%), acute myocardial infarction (59 patients, 27%), cardiogenic shock (7 patients, 3%), age 70 years or older (59 patients, 27%), renal failure (19 patients, 9%), and cerebrovascular accident and carotid disease (11 patients, 5%) were not found to be major predictors of early mortality or unfavorable outcome. During 12 months of follow-up (range 1 to 21 months), there were four cardiac and three noncardiac deaths (1-year actuarial survival 93%) and 17 cases (7.7%) of early return of angina. Calcified aorta, nonuse of the internal mammary artery, reoperation, and diabetes mellitus were independent predictors of unfavorable events. We conclude that coronary artery bypass grafting without cardiopulmonary bypass can be done with relatively low operative mortality, although there seems to be an increased risk for early return of angina. This procedure should therefore be considered for patients with appropriate coronary anatomy, in whom cardiopulmonary bypass poses a high risk. This procedure is still hazardous with calcified aorta or emergency operation.

Irradiation of fresh whole blood for prevention of transfusion-associated graft-versus-host disease does not impair platelet function and clinical hemostasis after open heart surgery

Since our previous studies suggested that the transfusion of 1 unit fresh whole blood (FWB) after cardiopulmonary bypass (CPB) using a bubble oxygenator may provide hemostatic benefit equivalent to 8-10 units of platelet concentrates, we have routinely used FWB at the termination of CPB. Two patients who received FWB and developed transfusion-associated graft-versus-host disease (TA-GVHD) prompted us to investigate the effect of irradiation of FWB on platelet and clinical hemostasis. Twenty-four patients were randomized to receive either 1 unit FWB (12 patients), or 1 unit irradiated FWB (IrFWB, 1,500 cGy,12 patients) after CPB. Platelet aggregation on extracellular matrix, studied by a scanning electron microscope and graded from 1 to 4 (from poor to excellent aggregation), was similar in both groups preoperatively [3.3 +/- 0.9 (FWB) and 3.5 +/- 0.5 (Ir FWB)], and at the end of CPB [1.8 +/- 1.2 (FWB) and 1.9 +/- 0.9 (IrFWB)]. Platelet aggregation was similar after transfusion of FWB (3.0 +/- 1.0) and after IrFWB (3.2 +/- 0.8), as was the increase in platelet count. Twenty-four hours total postoperative bleeding was similar (560 +/- 420 and 523 +/- 236 ml for FWB and IrFWB, respectively). We conclude that irradiation of FWB for prevention of TA-GVHD does not impair platelet aggregating capacity, and can be used when blood is donated by the patient's next of kin.

Aprotinin improves hemostasis after cardiopulmonary bypass better than single-donor platelet concentrate

Platelet transfusion and aprotinin administration improve platelet function and clinical hemostasis after extracorporeal circulation. To compare two methods of improving postoperative hemostasis, we preoperatively randomized 40 patients undergoing various open heart procedures into two groups. Group A included 20 patients who, immediately after bypass, received single-donor plateletpheresis concentrates collected from ABO-compatible donors (Baxter Autopheresis-C System). They were compared with 20 patients who received high-dose aprotinin (6 x 10(6) KIU) before and during cardiopulmonary bypass (group B). Group A patients showed significantly higher platelet count after single-donor plateletpheresis concentrate transfusion (157 +/- 36 x 10(9)/L compared with 118 +/- 42 x 10(9)/L (p < 0.05). However, platelet aggregation on extracellular matrix was better in group B (3.4 +/- 0.7 versus 2.8 +/- 0.9; p < 0.05). Total 24-hour blood loss and exposure to homologous blood products were significantly less in group B (396 +/- 125 mL and 1.1 +/- 1.6 units compared with 617 +/- 233 mL and 5.4 +/- 3.4 units; p < 0.01). Despite higher platelet count in patients after single-donor plateletpheresis concentrates transfusion, hemostasis in patients receiving aprotinin is better due to improved platelet function.

Hemostatic efficacy of dipyridamole, tranexamic acid, and aprotinin in coronary bypass grafting

Sixty patients (four groups of 15 patients) were entered in a randomized, controlled study to compare the efficacy of prophylactic treatment with dipyridamole, tranexamic acid, and aprotinin to reduce bleeding after elective coronary artery bypass grafting. Only patients with a preoperative platelet count of less than 246 x 10(9)/L were selected because a previous study showed that these individuals are at risk for increased postoperative bleeding. Compared to control subjects, postoperative blood loss 6 hours after operation was significantly reduced by tranexamic acid (674 +/- 411 versus 352 +/- 150 mL; p < 0.05) and by aprotinin (270 +/- 174 mL; p < 0.01). Dipyridamole did not reduce postoperative blood loss and was associated with complications in 3 patients. We conclude that hemostasis after cardiac operations can be improved with tranexamic acid and aprotinin. Dipyridamole appeared to be ineffective.

The skin bleeding time test as a predictor of brain bleeding time in a rat model

Previous studies have indicated that the skin bleeding time test does not accurately reflect visceral bleeding time (BT). The present study examines the predictive value of the skin bleeding time for brain bleeding tendency. Sixteen Sprague-Dawley rats were divided into equal groups. The first group (controls) underwent standardized skin and brain bleeding time tests under general anesthesia. Mean skin BT was found to be 168.8 sec with a standard deviation of +/- 20.8 sec. Mean brain BT was found to be 172.5 sec with a standard deviation of +/- 19.6 sec. The second group was given 23.2 mg/kg of aspirin per day for five days prior to skin and brain BT testing. Mean skin BT in this group was 315 seconds with a standard deviation of +/- 72.2 sec which proved to be significantly different from the control skin BT (P = 0.0005). Brain BT in the aspirin treated group was 155.6 sec with a standard deviation of +/- 22.6 sec. Brain BT in both control and aspirin treated groups was not significantly different (P = 0.13). All animals were euthanized 30 minutes after brain BT and their brains harvested. One animal in the control group showed evidence of a small subcortical hemorrhage upon brain sectioning. Sectioned brains in the aspirin-treated group showed no evidence of subcortical hematoma. The results indicate that skin BT is prolonged by aspirin administration, but brain bleeding time is unaffected. Brain hemostasis is likely more dependent on intrinsic procoagulant than platelet function. The skin BT test may therefore be of little utility as a preoperative screening test for neurosurgical patients.

Predictive value of blood clotting tests in cardiac surgical patients

This study prospectively evaluated numerous tests of clotting function in 897 consecutive adult cardiac surgical patients over 18 months. This included coronary operation, valve replacement, and reoperative patients. The tests included activated clotting time, activated partial thromboplastin time, prothrombin time, thrombin time, fibrinogen, fibrin/fibrinogen degradation products, platelet count, and Duke's earlobe bleeding time. Other variables such as age, sex, and cardiopulmonary bypass duration were included in the multivariate analysis. Statistically significant correlations were found between 16-hour mediastinal drainage and activated partial thromboplastin time, fibrinogen, activated clotting time, fibrin/fibrinogen degradation products, platelet count, and prothrombin time. Scatter plots indicate that these relationships, although statistically significant, had little predictive value and were largely significant as a result of the large number of patients in each group, which permitted weak correlations to reach statistical significance. The best multivariate model constructed could explain only 12% of the observed variation in postoperative blood loss. Because the predictive values of the tests are so low, it does not appear sensible to screen patients routinely using these clotting tests shortly after cardiopulmonary bypass.

Decreased postoperative drainage with addition of epsilon-aminocaproic acid before cardiopulmonary bypass

Desmopressin (DDAVP, 0.3 microgram/kg) has been used routinely after cardiopulmonary bypass, particularly in patients having antiplatelet therapy. Recently epsilon-aminocaproic acid (single dose of 5 g) given before cardiopulmonary bypass has been added to the protocol. One hundred consecutive patients taking desmopressin and epsilon-aminocaproic acid (group A) and another 100 taking desmopressin alone (group B) were analyzed. There was no difference among these two groups in patient age, sex, preoperative history of bleeding and drug consumption, or number of patients for elective, urgent, emergent, redo, and reoperation for bleeding. Results of routine preoperative coagulation studies were within normal limits in both groups. Preoperative hemoglobin level was 13.5 g/dL in group A and 13.8 g/dL in group B (p = 0.12). Estimated blood loss in the operating room was 513 mL for group A and 587 mL for group B (p = 0.07). The total chest drainage at the end of 24 hours was 492 mL in group A and 746 mL in group B (p = 0.0001). Amicar given before cardiopulmonary bypass does not lessen operating room blood loss, but significantly decreases postoperative chest drainage. Group B patients received more fresh frozen plasma (60 U versus 4 U), more platelets (130 U versus 16 U), and more cryoprecipitate (118 U versus 10 U) than group A patients. Adding epsilon-aminocaproic acid could save $206.18 in blood product use per patient, compared with the expense of $24.12 per patient for E-aminocaproic acid administration.

The Use of Aprotinin in Pediatric Cardiac Surgery

From April 1990 to December 1992, we used aprotinin in 80 pediatric cases undergoing cardiac surgery. Most patients had moderate to severe tetralogy of Fallot and other complex cyanotic diseases, and 12 cases were reoperated. One-half to one-third of the recommended dose was adopted, and 3 different patterns of administration were compared. All procedures achieved good results with less postoperative bleeding. We suggest the simplest procedure—adding 1 bolus dose of aprotinin to the pump prime—as the method of choice.

Comparison of thromboelastography to bleeding time and standard coagulation tests in patients after cardiopulmonary bypass

This prospective study of 36 adult patients undergoing cardiopulmonary bypass (CPB) was conducted to determine the utility of thromboelastography (TEG) versus platelet studies (bleeding time, platelet count, mean platelet volume) and standard coagulation tests (prothrombin time, activated partial thromboplastin time, fibrinogen) to more effectively discriminate patients likely to benefit from platelet or fresh frozen plasma (FFP) transfusion. Although the sensitivities of the bleeding time (71.4%) and platelet count (100%) were similar to the TEG (71.4%), the specificity (89.3%) of the TEG was greater than that of the bleeding time (78.5%) and platelet count (53.6%). Seven patients experienced clinically significant hemorrhage; 5 (71.4%) had an abnormal TEG. Three of 8 (38%) other patients with an abnormal TEG had no abnormal bleeding. Only 2 of 27 (7.4%) patients with a normal TEG had abnormal bleeding requiring platelet or FFP transfusion. Therefore, it is suggested that post-CPB patients with a normal TEG should not receive platelet or FFP transfusions empirically. If excessive bleeding is noted in a patient with a normal TEG, this suggests a surgically correctable etiology. Data from this series suggest that patients displaying an abnormal TEG appear to be at increased risk for hemorrhage; therefore, appropriate blood product support should be initiated at the first sign of accelerated bleeding.

RETRACTED: Influence of acute preoperative plasmapheresis on platelet function in cardiac surgery

Withdrawal of autologous plasma offers the possibility of improving patients' hemostasis and of reducing homologous blood consumption in cardiac surgery. The influence of acute, preoperatively performed plasmapheresis (APP) on platelet function was investigated in elective aortocoronary bypass patients subjected to APP producing either platelet-poor plasma (PPP; group 1; n = 12) or platelet-rich plasma (PRP; group 2; n = 12). APP-treated patients were randomly compared to patients without APP (control group; n = 12). Platelet aggregation induced by ADP (concentration 0.25, 0.5, 1.0, and 2.0 mumol/L), collagen (4 microL/mL), and epinephrine (25 mumol/L) was determined by the turbidometric method before and after APP, as well as before and after cardiopulmonary bypass (CPB) until the morning of the 1st postoperative day. APP had no negative effects on the patients' aggregation parameters (maximum aggregation and maximum gradient of aggregation). The platelet counts in the withdrawn plasma were 25 +/- 10 x 10(9)/L (PPP-group) and 250 +/- 30 x 10(9)/L (PRP-group). Platelet counts were highest in the PRP-group at the end of the operation (after retransfusion of autologous plasma). After CPB, maximum aggregation and maximum gradient of aggregation were reduced in all groups (ranging from -6% to -25% from baseline values). Retransfusion of autologous plasma improved platelet aggregability significantly only in the PRP-group. By the first postoperative day, maximum aggregation and maximum gradient of aggregation recovered in all groups (including the control group) or even exceeded baseline values (ranging from +8% to +42% from baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet protection by low-dose aprotinin in cardiopulmonary bypass: electron microscopic study

To evaluate the effect of low-dose aprotinin during cardiopulmonary bypass on platelet function and clinical hemostasis, 30 patients undergoing various cardiopulmonary bypass procedures employing bubble oxygenators were randomized to receive either low-dose aprotinin (2 x 10(6) KIU in the cardiopulmonary bypass priming solution, 15 patients [group A]) or placebo (15 patients [group B]). Blood samples were collected before and after cardiopulmonary bypass to assess platelet count and aggregation on extracellular matrix, which was studied by a scanning electron microscope. On a scale of 1 to 4 preoperative mean platelet aggregation grades were similar in both groups (3.8 +/- 0.5 and 3.5 +/- 0.5 for groups A and B, respectively). Postoperatively, platelet aggregation on extracellular matrix decreased slightly in group A (2.8 +/- 1.3; p < 0.01) and significantly in group B (1.3 +/- 0.5; p < 0.001). Eleven of the 15 patients in group A remained in aggregation grade 3 or 4 compared with none of the group B patients. Platelet count was similar in both groups preoperatively and postoperatively. Total 24-hour postoperative bleeding and blood requirement were lower in the aprotinin group (487 +/- 121 mL and 2.3 +/- 1.0 units) than in the placebo group (752 +/- 404 mL and 6.8 +/- 5.1 units; p < 0.01). These results show that the use of low-dose aprotinin during cardiopulmonary bypass provides improved postoperative hemostasis, which might be related to the protection of the platelet aggregating capacity.

Coagulation defects in neonates during cardiopulmonary bypass

We examined components of the coagulation system in 30 neonates (age, 1 to 30 days) undergoing deep hypothermic cardiopulmonary bypass (CPB). A coagulation profile consisting of activated clotting time; prothrombin time; partial thromboplastin time; factors II, V, VII, VIII, IX, X, and I (fibrinogen); antithrombin III; platelet count; and heparin levels was evaluated before bypass, at three intervals during bypass (1 minute after initiation of bypass, stable hypothermic CPB, warm CPB), after weaning from CPB and administration of protamine, and 2 to 3 hours after skin closure. The initiation of CPB resulted in a 50% decrease in circulating coagulation factors and antithrombin III levels. Platelet counts were reduced by 70% with CPB initiation. Neither deep hypothermic temperatures nor prolonged exposure to extracorporeal surfaces had any additional effect on the coagulation profiles. This suggests that the coagulation system of a neonate undergoing CPB is profoundly and globally effected by hemodilution. We believe that treatment of post-CPB coagulopathy in neonates must address these global deficits.

Platelet protection by aprotinin in cardiopulmonary bypass: electron microscopic study

To evaluate the functional integrity of platelets in patients administered the proteinase inhibitor aprotinin during cardiopulmonary bypass, 20 patients undergoing a complicated and prolonged open heart operation were studied. They were randomized to receive either a high dose of aprotinin (total dose, 6 to 7 x 10(6) KIU) before and during cardiopulmonary bypass (10 patients) or a placebo (10 patients). Blood samples were collected preoperatively, at the termination of bypass, and 90 minutes thereafter to assess platelet count and aggregation on extracellular matrix, which was studied by scanning electron microscopy. On a scale of 1 to 4, mean preoperative platelet aggregation grades were similar in both groups (3.5 +/- 0.5). Postoperatively, at the termination of cardiopulmonary bypass and 90 minutes thereafter, all 10 patients treated with aprotinin revealed normal, unchanged platelet aggregation (grade, 3.5 +/- 0.5), whereas all placebo-treated patients showed severely disturbed aggregation (grade, 1.4 +/- 0.5) (p less than 0.001). The platelet count was similar in both groups before and after operation (preoperatively, 182 +/- 75 x 10(9)/L and 146 +/- 30 x 10(9)/L, and postoperatively, 87 +/- 13 x 10(9)/L and 80 +/- 27 x 10(9)/L for the aprotinin and placebo groups, respectively). Total 24-hour postoperative bleeding and blood requirement were significantly lower in the aprotinin group (371 +/- 84 mL and 2 +/- 0.7 units, respectively) compared with the placebo group (608 +/- 28 mL and 3.4 +/- 1.3 units, respectively) (p less than 0.01). These results demonstrate that improved postoperative hemostasis is directly related to the complete preservation of platelet function achieved by the protective properties of aprotinin.

Fresh blood units contain large potent platelets that improve hemostasis after open heart operations

Twenty units of fresh whole blood were separated into fresh packed red blood cells (PC) and platelet-rich plasma (PRP) and were transfused to 40 patients immediately after coronary bypass grafting. Patients were preoperatively randomized to receive either PRP (group A, 20 patients) or PC (group B, 20 patients). Platelet number in the PRP group was greater, but not significantly greater, than in the PC group (7.5 +/- 3 versus 5.9 +/- 2.2 x 10(10); p = not significant). However, mean platelet volume in the PC group was significantly greater (8.75 +/- 1.1 versus 6 +/- 0.7 fL). Postoperatively, group A patients bled more than group B (566 +/- 164 versus 327 +/- 41 mL; p less than 0.01) and received more red blood cell units (2.7 +/- 1.2 versus 1.6 +/- 0.7 U; p less than 0.05) and a larger number of blood products (5.9 +/- 3.7 versus 2.6 +/- 1.2 U; p less than 0.05). Transfusion of PRP to group A increased platelet count from 128 +/- 20 to 148 +/- 110 x 10(9)/L; however, platelet functions did not improve. Administration of PC to group B increased platelet count from 139 +/- 22 to 156 +/- 23 x 10(9)/L, improved platelet aggregation (with collagen from 33% +/- 20% to 53% +/- 23%, with epinephrine from 36% +/- 24% to 51% +/- 20%; p less than 0.05), and corrected the prolonged bleeding time. The results suggest that the improved hemostasis observed after fresh whole blood administration is related to the large, potent platelets that remained in the PC and were not separated to the PRP during standard platelet concentrate preparation.

Platelet-leukocyte plasmapheresis attenuates the deleterious effects of cardiopulmonary bypass

A method of harvesting a high yield of concentrated platelet- and leukocyte-rich plasma was developed with the goal of attenuating some of the deleterious effects of cardiopulmonary bypass. The study involved 32 patients who underwent coronary artery bypass grafting with plasmapheresis before cardiopulmonary bypass and a control group of 32 patients who did not have plasmapheresis. A volume of 857 +/- 359 mL of platelet- and leukocyte-rich plasma was concentrated from 4.6 +/- 1.5 L of blood, and red cells and plasma were returned to the patient. The platelet- and leukocyte-rich plasma contained yields of 3.5 +/- 1.4 x 10(11) platelets and 3.4 +/- 1.9 x 10(9) leukocytes. There were no differences in age, sex, duration of cardiopulmonary bypass, and major risk factors between groups. However, total mediastinal chest tube drainage was 788 +/- 542 mL in the controls and 425 +/- 207 mL in the plasmapheresis group (p less than 0.01). Homologous units transfused were 3.9 +/- 2 in controls and 1.6 +/- 2 in the plasmapheresis group (p less than 0.01). Arterial oxygen tension on extubation was 94 +/- 32 mm Hg in controls and 119 +/- 25 mm Hg in the plasmapheresis group (p less than 0.01). This technique of platelet and leukocyte protection results in reduced postoperative bleeding, a decreased need for homologous blood products, and improved pulmonary function.

Activation of coagulation and fibrinolysis during surgery, analyzed by molecular markers

Activation of hemostasis during surgery was investigated in 30 elective cases, who underwent either gastric (group G) or hepatic (group H) resection by a serial determination of various molecular markers such as fibrinopeptide A (FPA), fibrinopeptide B beta 15-42 (B beta 15-42) D-dimer, thrombin-antithrombin III complex (TAT) and plasmin-alpha 2 plasmin inhibitor complex (PIC). In both groups, the values of FPA and TAT were significantly elevated intraoperatively, indicating an occurrence of hypercoagulable state. The degree of the elevation was more marked in group H, probably due to greater tissue damage during hepatic resection. Also in both groups, the values B beta 15-42 and PIC were significantly increased during surgery, while the amount of D-dimer was within normal range in most cases, indicating the occurrence of the primary fibrinolysis. These findings are compatible with our previous observations on the postoperative changes in hemostasis. There were statistically significant but variable correlations between the values of fibrinopeptides and the enzyme-inhibitor complexes. The absolute values of the molecular markers of fibrinolysis were always higher than those of coagulation, suggesting that a considerable amount of plasmin, rather than thrombin, is released by surgical tissue damages.