Is cardiopulmonary bypass a reason for aspirin resistance after coronary artery bypass grafting?

OBJECTIVE: 'Off-pump' coronary artery bypass grafting (OPCAB) is an alternative to conventional coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB). While midterm results after OPCAB have become available, systematic studies of changes in platelet function after OPCAB are still missing. Since we have previously shown that oral aspirin treatment (100mg) does not achieve sufficient platelet inhibition in the majority of patients operated on with CPB, we hypothesized that bypass surgery without CPB (off-pump coronary artery bypass, OPCAB) causes less impairment of platelet inhibition by aspirin. The aim of this study was to investigate platelet function and the antiplatelet effect of aspirin after off-pump coronary artery bypass grafting in comparison with conventional on-pump surgery. METHODS: We compared platelet function (in vitro aggregation and thromboxane formation) before and at days 1 and 5 after coronary artery bypass grafting, performed with (n=15) or without (n=14) CPB. Oral aspirin treatment (100mg/d) was started at day 1 after surgery. RESULTS: After a 5 day oral treatment with aspirin, platelet aggregation was inhibited significantly in OPCAB-patients to 55.7+/-16.3% of control before surgery (P<0.05), whereas aggregation remained unchanged after CPB (105.8+/-26.9% of control before surgery; P>0.05). Since aspirin primarily inhibits platelet thromboxane formation, thromoboxane was determined after in vitro aggregation. According to platelet aggregation, thromboxane formation was only inhibited significantly after OPCAB (29.2+/-13.0% of control before surgery, P<0.05), but not after CPB (74.5+/-21.4% of control before surgery, P>0.05). This resistance to aspirin after CPB may be caused by an increased release of new platelets which are competent to form thromboxane, since the number of platelets decreased from 237+/-11x10(3)/microl before CPB to 174+/-13x10(3)/microl at day 1 after surgery and increased significantly the following days reaching 303+/-17x10(3)/microl at day 5. Platelet counts of patients operated on without CPB showed no significant changes (236+/-16x10(3)/microl before OPCAB, 220+/-16x10(3)/microl at day 1 and 266+/-31x10(3)/microl at day 5 after surgery). CONCLUSIONS: The antiplatelet effect of aspirin is largely impaired after CPB, but not after CABG without CPB. Hence, increased platelet turnover after CPB seems to contribute to aspirin resistance, since an increased number of platelets might be competent to form thromboxane within the dosing intervals.     

自体富血小板凝胶的制备及其生长因子分析

目的 探讨不同离心方法 制备自体富血小板凝胶(autologous platelet-rich gel,APG)的方法 ,通过改变离心速度比较不同的离心力对PLT富集的影响分析全血和APG中5种生长因子浓度.方法 对13例糖尿病难治性皮肤溃疡患者行APG治疗.取11例自身外周静脉血,分别用3种离心速度制备富血小板血浆(platelet-rich plasma,PRP).A组(n=6)先以529×g离心4 min,再以854×g离心6 minB组(n=5)先以313×g离心4 min,再以1252×g离心6 min;C组(n=5)先以176×g离心5 min,再以1 252×g离心5 min.将离心后制得的PRP与凝血酶.钙剂以101混合凝固后制备APG,用于患者皮肤溃疡的治疗.采用全自动血细胞分析仪计数各组全血和PRP中PLT数量.采用酶联免疫吸附法测定全血和APG中PDGF.BB、VEGF、IGF.1、EGF和TGF.a1 5种生长因子浓度.结果 A组PRP中PLT数量为(779.67±352.39)×109/L,较全血的(263.50±76.63)×109/L提高(2.98±1.42)倍,差异有统计学意义(P＜0.05);PLT回收率为51.5%±22.2%.B组PRP中PLT数量最高,为(1363.80±919.74)X 109/L,较全血的(232.80±127.99)×109/L提高(5.91±2.04)倍,差异有统计学意义(P＜0.05);PLT回收率为75.2%±21.0%,明显高于A组(P＜0.05).全血和APG中PDGF-BB、EGF、IGF-1以及TGF-a.浓度分别为(145.94±133.24)、(503.81±197.86)pg/mL,(160.73±71.10)、(265.95±138.43)pg/mL,(14.54±35.34)、(110.56±84.36)ng/mL,(3.31±2.27)、(5.67±4.80)ng/mL,差异有统计学意义(P＜0.05);VEGF浓度升高,两者间差异无统计学意义(P＞0.05).对数转换后的PLT数量与PDGF-BB、TGF-a1浓度成正相关,相关系数r分别为0.627和0.437(P＜0.05).13例患者共行18次APG治疗,其中9例治疗12周溃疡愈合,愈合率为69.2%;10例窦道愈合,愈合率为83.3%.结论 以313×g离心4 min,再以1252×g离心6 min是制备PRP的最佳方法 ;APG中生长因子浓度高于全血;PLT数量与PDGF-BB、TGF-a1浓度成正相关.     

Does etiology of end-stage renal disease affect sleep quality in kidney transplant recipients?

BACKGROUND: That hypertension (HTN) as a leading cause of end-stage renal disease (ESRD) is linked to sleep disorders in the general population can be the basis of a hypothesis that HTN may be a contributing factor to the poor quality of sleep in some kidney transplant recipients. This study was designed to investigate the correlation between ESRD secondary to HTN and sleep quality among kidney transplant recipients. METHODS: In this case control study, 201 kidney transplant recipients were divided into group I (ESRD) secondary to HTN, (n=82) and group II (ESRD secondary to other causes, n=119). The groups were matched for medical comorbidities, demographic and clinical data, and symptoms of anxiety and depression. Sleep quality assessed by means of the Pittsburgh Sleep Quality Index (PSQI) was compared between the study groups. RESULTS: The mean (SD) of the total PSQI score was significantly high in group I compared with group II (7.42 +/- 2.36 vs 6.60 +/- 3.07, P=.042). Similar results were observed for the sleep duration scores in the groups (1.22 +/- 1.12 vs 0.86 +/- 1.12, P=.026). In group I, all the other PSQI components were higher than those in group II, difference that were statistically significant. CONCLUSION: Sleep quality and duration was poorer among our kidney transplant recipients with ESRD secondary to HTN compared with the controls. Further studies, however, are required to investigate whether HTN is responsible for the reported poor quality of sleep in some kidney transplant recipients.     

Antihemostatic and antithrombotic effects of monoclonal antibodies against von Willebrand factor in nonhuman primates.

BACKGROUND. Because the adhesive glycoprotein von Willebrand Factor (vWF) mediates initial platelet attachment at sites of vascular injury and may also contribute to shear-dependent platelet thrombus formation, we have determined in vivo the relative antithrombotic efficacy and hemostatic safety of infusing murine monoclonal antibodies against vWF. METHODS. In baboons with chronic arteriovenous shunts, thrombus formation was initiated by interposition of thrombogenic Dacron vascular grafts (VG) and endarterectomized baboon aortic segments (EAS). Thrombus formation on VG and EAS was assessed by use of real-time scintillation camera imaging of indium 111-labeled platelet deposition. In control and treated animals (anti-vWF antibody) platelet hemostatic competence was evaluated by means of serial measurements of platelet count, bleeding time, and ex vivo platelet aggregation in response to adenosine diphosphate and ristocetin. RESULTS. Although bolus antibody infusions did not affect circulating platelet counts, bleeding times were immediately prolonged to 28 +/- 4 minutes (vs 4.7 +/- 0.4 minutes before treatment, p = 0.01). Bleeding times normalized within 24 hours after antibody administration. Platelet aggregation in response to adenosine diphosphate was unchanged by antibody therapy, whereas ristocetin-induced platelet aggregation was abolished acutely and remained impaired for 24 hours. Platelet deposition on VG after 60 minutes of exposure to flowing blood was 2.95 +/- 0.74 x 10(9) platelets/cm in six control animals as compared to 1.86 +/- 0.16 x 10(9) platelets/cm in five treated animals (p = 0.04). Similarly, platelet deposition on EAS averaged 4.40 +/- 0.89 x 10(9) platelets/cm in control studies and was reduced significantly by antibody therapy (1.52 +/- 0.50 x 10(9) platelets/cm, p = 0.02). CONCLUSIONS. Despite profound interruption of platelet hemostatic functions, therapeutic targeting of vWF modestly inhibits platelet-dependent thrombosis.     

Biocompatibility of extracorporeal circulation with autooxygenation.

Platelet damage, complement activation and neutropenia during cardiopulmonary bypass are the result of blood contact with artificial surfaces, mainly in the oxygenator. To evaluate biocompatibility of this kind of bypass we compared two techniques of extracorporeal circulation in 40 patients undergoing elective coronary bypass operations. In 20, a standard technique with a bubble oxygenator was used (group 1), and in the remaining 20 patients with autooxygenation, the patients' own lungs were included in the perfusion circuit (group 2). Several blood samples were taken before, during and after perfusion to estimate the corrected platelet numbers and pulmonary leucocyte sequestration in all patients, and additionally in 6 patients from each group, complement C3a and C5a anaphylatoxins were measured (radioimmunoassay). At the end of cardiopulmonary bypass, the decline of platelet number corrected to haematocrit platelet number in group 1 was significantly higher than in group 2 (P less than 0.01). There was a significant increase in circulating white blood cells when compared to pre-bypass time in both groups (P less than 0.05). However, comparison of differences between leucocyte counts in the blood of the patients' right and left atria showed enhanced leucocyte sequestration in group 1, 1.46 +/- 0.5 x 10(3)/mm3 vs only 0.34 +/- 0.2 x 10(3)/mm3 in group 2. The C3a rose progressively during extracorporeal circulation: in group 1 from 268 +/- 46 ng/l to 521 +/- 65 ng/l, and in group 2 from 244 +/- 46 ng/l to 418 +/- 34 ng/l (P less than 0.05). No characteristic changes in C5a activation were observed in either group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vascular function in patients with end-stage renal disease and/or coronary artery disease: a cardiac magnetic resonance imaging study

Decreased arterial compliance in end-stage renal disease (ESRD) is associated with increased cardiovascular risk. Our aim was to examine aortic compliance in patients with ESRD using cardiac magnetic resonance imaging (MRI) and to compare these with patients with advanced atherosclerotic disease who are known to be at high cardiovascular risk. We examined a total of 83 subjects matched for age: 24 had ESRD and were on dialysis therapy for 3+/-6 years, 24 had severe coronary artery disease (CAD), 11 had both ESRD and CAD (4+/-5 years on dialysis therapy), and 24 healthy subjects with no evidence of CAD. Vascular and cardiac function was assessed using cardiac MRI. Aortic compliance was significantly reduced in patients with CAD compared to control subjects (11.3+/-6.3 ml x 10(-3)/mm Hg vs 15.6+/-6.0 ml x 10(-3)/mm Hg, P=0.009). Patients with ESRD also exhibited significantly reduced aortic compliance compared to healthy controls (12.4+/-5.8 ml x 10(-3)/mm Hg vs 15.6+/-6.0 ml 10(-3)/mm Hg, P=0.012), whereas there was no significant difference in aortic compliance between patients with CAD and ESRD. Even in the absence of symptomatic CAD, patients with ESRD have significantly reduced aortic compliance compared to normal subjects. Patients with ESRD have equivalent aortic compliance to patients with advanced CAD. These findings suggest that a significantly reduced aortic compliance is one of many mechanisms promoting premature cardiovascular events in patients with ESRD compared to age-matched controls from the general population.     

Peripheral blood leukocyte counts in cytomegalovirus infected heart transplant patients: impact of acute disease versus subclinical infection

BACKGROUND: Cytomegalovirus (CMV)-associated leucopenia in heart transplant patients is poorly characterized. METHODS: We conducted a retrospective analysis of timing, degree, and type of leukopenia in four groups of patients: cases (n=20); controls (n=20); subclinical early infection (n=21), and subclinical late infection (n=22). In the cases, white blood cells (WBC) count at diagnosis was compared to prediagnosis; and cases were compared to controls. Subclinical cases (early and late) were identified by measurement of CMV DNA in peripheral blood mononucleocytes, and WBC was compared to those of the cases and controls. RESULTS: First, in human heart transplant recipients the total leukocyte count decreased prior to the time of diagnosis of CMV disease: cases: 5.4+/-2.1 x 10/microL vs. 3.7+/-2.1x10/muL (P<0.01); subclinical early: 8.1+/-4.1 x 10/microL vs. 6.9+/-1.6 x 10/microL (P<0.01). Second, the leukocyte populations most reduced during CMV disease are the neutrophils: 4.4 x 10/microL (78%) to 2.5 x 10/microL (69%) (P<0.05), and monocytes 0.6 x 10/microL (11%) to 0.3 x 10/microL (7.5%) (P<0.05). Third, the reduction in leukocyte count that occurs during CMV disease appears to be independent of immunosuppressive therapy (using cyclosporine A, mycophenolate mofetil, or azathioprine and prednisone). Finally, subclinical CMV infection in stable long-term heart transplant patients without disease is unassociated with a reduction in the leukocyte count. CONCLUSIONS: Aside from implications for early diagnosis, CMV-associated decrease in monocytes is important because viral infections like Epstein-Barr virus cause monocytosis. The absence of leucopenia in subclinical late infections is a new important finding.     

Biochemical abnormalities of platelets in renal failure. Evidence for decreased platelet serotonin, adenosine diphosphate and Mg-dependent adenosine triphosphatase

The platelet content of adenosine triphosphate (ATP), adenosine diphosphate (ADP), serotonin and ouabain-insensitive, magnesium-dependent adenosine triphosphatase (ATPase) was determined in patients with chronic renal failure, patients on chronic hemodialysis, and kidney transplant recipients. Platelet ATP content was normal in all. By contrast, ADP content, expressed in mumol/10(11) platelets, was significantly lower in renal failure: 1.82 +/- 0.96 compared to 2.51 +/- 0.97 in normals (p less than 0.05), but not in dialyzed or transplanted patients; 2.27 +/- 0.96 and 1.87 +/- 0.87, respectively. The mean content of serotonin was also significantly lower in renal failure patients: 0.52 microgram/10(9) platelets as compared to 0.90 microgram/10(9) platelets in normals (p less than 0.05) but was not significantly different in dialyzed and transplanted patients. ATPase was significantly lower in renal failure: 3.13 +/- 1.2 mumol Pi/10(9) platelets in whole suspension and 0.71 +/- 0.22 Pi/mg protein/h in membrane preparation compared to 4.74 +/- 1.1 and 1.18 +/- 0.19, respectively, in normals, and was significantly lower in dialyzed and transplanted patients. Experimental azotemia (BUN 65-86 mg/100 ml), induced by the oral ingestion of urea 2-3 g/kg body weight over 24 h, failed to induce any of these abnormalities. The abnormality in platelet ADP and serotonin content in renal failure paralleled the functional platelet defects which characterize these patients and were reversible following dialysis and transplantation.     

Thrombocytopenia in liver transplant recipients: predictors, impact on fungal infections, and role of endogenous thrombopoietin

BACKGROUND: Thrombocytopenia is a frequent and potentially serious complication in liver transplant recipients. The role of endogenous thrombopoietin level in posttransplant thrombocytopenia, has not been fully defined in liver transplant recipients. Additionally, there is accumulating evidence to suggest that platelets play a important role in antimicrobial host defense. METHODS: There were 50 consecutive liver transplant recipients studied. Variables predictive of thrombocytopenia, its impact on infectious morbidity and outcome, and serial thrombopoietin (TPO) serum concentration were assessed. RESULTS: The median pretransplant platelet count was 67 x 10(3)/cmm. After the liver transplantation, the median nadir platelet count was 33 x 10(3)/cmm and was reached a mean of 6 days after the transplant. A lower pretransplant platelet count (r= +.068, P=.0001), lower serum albumin before the transplants (r=+0.39, P=.014), longer operation time (r=0.27, P=.05), higher intraoperative packed red cells (r=0.28, P=.049) and fresh frozen plasma transfusions (r=0.42, P=.004), higher bilirubin at Day 7 (r=-.386, P=.005), and higher serum creatinine at Day 7 after the transplants (r=-.031, P=.025) correlated significantly with a lower nadir in platelets after the transplant. Nadir in platelet count was significantly lower in nonsurvivors compared with survivors (16 vs. 36 x 10(3)/cmm, P=.0001). Forty-three percent (9 of 21) of the patients with nadir platelet counts of < or =30 x 10(3)/cmm had a major infection within 30 days of the transplant compared with 17% (5 of 29) with nadir platelet counts > 30 x 10(3)/cmm (P=.04). Fungal infections occurred in 14% of the patients with nadir platelet counts of < or =30 x 10(3)/cmm versus 0% in those with nadir platelet counts of > 30 x 10(3)/cmm (P=.06); all patients with fungal infections had nadir platelet counts of < or =30 x 10(3)/cmm before fungal infection. Nadir in platelet count preceded the first major infection by a median of 7 days. Pretransplant TPO level did not differ between survivors (mean 103 pg/ml) or nonsurvivors (mean 144 pg/ml). After the transplantation, TPO levels increased in both groups. TPO level peaked at Day 7 and subsequently declined in survivors. Nonsurvivors had persistent thrombocytopenia despite a progressive rise in TPO level; TPO level was significantly higher at Day 7 (P=.02), Day 9 (P=.0019), and Day 14 (P=.04) in nonsurvivors compared with survivors. CONCLUSION: Persistent thrombocytopenia portended a poor outcome in liver transplant recipients and was not related to low TPO levels. Thrombocytopenia preceded infections and identified a subgroup of liver transplant patients susceptible to early major infections; its precise role in fungal infections warrants validation in larger studies.     

The effects of heparin and extracorporeal circulation on platelet counts and platelet microaggregation during cardiopulmonary bypass

BACKGROUND: Cardiopulmonary bypass is associated with platelet activation and reduced platelet counts. Platelet activation may artifactually lower platelet counts by causing aggregation. In vivo platelet activation may increase existent platelet microaggregation ex vivo. We studied platelet counts and existent platelet microaggregation at different stages of cardiopulmonary bypass. METHODS: Twenty-one patients were studied before and after heparinization (300 U. kg(-1)) and at the end of cardiopulmonary bypass. Unaggregated (or single) platelets were counted in hirudin-anticoagulated blood, and total platelets were counted in ethylenediaminetetraacetic acid-anticoagulated blood. RESULTS: The total platelet count, 198 +/- 61 x 10(9). L(-1), was unaffected by heparin and stayed at 197 +/- 60 x 10(9). L(-1) (P =.7) but fell during extracorporeal circulation; the hemodilution-corrected count was 163 +/- 52 x 10(9). L(-1) (P =.0004). Heparinization reduced the unaggregated platelet count from (mean +/- 1 SD) 178 +/- 62 x 10(9). L(-1) to 155 +/- 60 x 10(9). L(-1) (P =.0001). Extracorporeal circulation had little additional effect. The hemodilution-corrected count was 142 +/- 48 x 10(9). L(-1) (P =.6). CONCLUSIONS: Heparinization caused platelet activation and increased existent platelet microaggregation ex vivo. During extracorporeal circulation, there was a reduction in total platelets that was greater than could be explained by hemodilution alone, but the unaggregated platelet count did not change significantly when corrected for hemodilution. Furthermore, the increased platelet microaggregation observed after heparinization was no longer evident after this loss. These findings suggest that during extracorporeal circulation, the platelets that formed into microaggregates after heparinization were lost from the circulation in preference to single platelets.     

Perioperative suppression of platelet adherence to small-diameter polytetrafluoroethylene (PTFE) grafts

The perioperative effect of platelet antagonists on small-diameter polytetrafluoroethylene (PTFE) grafts was evaluated in forty-six New Zealand white male rabbits receiving either dipyridamole (DPM) 100 mg/kg/day (n = 10; group 1), aspirin (ASA) 10 mg/kg/day (n = 10; group 2), a combination of ASA 10 mg/kg/day and DPM 10 mg/kg/day (n = 9; group 3) or 100 mg/kg/day (n = 10; group 4), or placebo (n = 7) as single daily doses. All regimens began 72 hr prior to insertion of a 20 x 3-mm internal diameter PTFE interposition aortic graft. Autologous indium-111 labeled platelets were injected immediately after implantation. Graft and an equivalent segment of aorta were harvested after 48 hr. Graft platelet adherence index (GPAI) was calculated as the graft:reference aorta ratio of emissions. The GPAI in the control group was 238 +/- 46 (mean +/- SD). Single regimen antiplatelet agents in groups 1 and 2 reduced mean GPAI to 47 +/- 38 and 40 +/- 12, respectively. The combination regimen in group 3 lowered mean GPAI to 43 +/- 8 and in group 4 to 21 +/- 7. Platelet uptake in PTFE grafts at 48 hr is significantly lowered to 8.8 to 19.7% of control by perioperative antiplatelet agents given as a single daily oral dose (P less than 0.001). ASA alone and DPM alone provided similar suppression of platelet uptake, but combination ASA + low dose or high dose DPM gave significantly greater (P less than 0.001) suppression of early platelet deposition than the single agent regimens. These results support perioperative administration of combination oral antiplatelet agents as adjunctive therapy in small diameter prosthetic graft implantation.     

Platelet aggregation in traumatic spinal cord injury.

Study design: Collagen-induced platelet aggregation and platelet count of ten paraplegic patients (four females, six males, aged 16 - 42 years) with traumatic spinal cord injury (SCI) (posttraumatic 12 - 48 weeks) and of ten age-matched healthy volunteers (control group; five females, five males, aged 18 - 37 years) were investigated. Objectives: Investigation of platelet aggregation in the whole blood of the patients with SCI. Setting: Ankara/Turkey. Methods: Platelet aggregation was evaluated by impedance technique using Chrono Log Model 560 WB aggregometer in whole blood. Platelet count was determined by Medonic Cell Analyser 610. Results: Maximal intensity of collagen-induced platelet aggregation of the patients was 18.50+/-8.28 ohm (mean+/-SD) and of the controls was 7.60+/-4.25 ohm. Maximal rate of collagen-induced aggregation of platelets from the patients was 3.98+/-1.59 ohm/min, maximal rate of aggregation of platelets from the controls was 1.57+/-1.01 ohm/min. Platelet counts of the patients and controls were 290 500+/-50 357/mm3 and 273 000+/-48 343/mm3 respectively. It was determined that both maximal rate (P<0.001) and maximal intensity (P<0.01) of collagen-induced platelet aggregation of the patients were significantly higher than those of the controls. There was no significant difference between the two groups in respect to platelet counts. Conclusion: Collagen-induced platelet aggregation of patients with traumatic SCI 12 - 48 weeks after the trauma was significantly higher than that of the controls. Our results indicate that increased tendency of platelet aggregation, which is probably induced by free radicals, may have a great impact on the late thromboembolic complications reported in patients with traumatic SCI.     

Homocysteine and methionine metabolism in ESRD: A stable isotope study.

BACKGROUND: Hyperhomocysteinemia has a high prevalence in the end-stage renal disease (ESRD) population, which may contribute to the high cardiovascular risk in these patients. The cause of hyperhomocysteinemia in renal failure is unknown, and therapies have not been able to normalize plasma homocysteine levels. Insight into methionine-homocysteine metabolism in ESRD is therefore necessary. METHODS: Using a primed, continuous infusion of [2H3-methyl-1-13C]methionine, we measured whole body rates of methionine and homocysteine metabolism in the fasting state in four hyperhomocysteinemic hemodialysis patients and six healthy control subjects. RESULTS: Remethylation of homocysteine was significantly decreased in the hemodialysis patients: 2.6+/-0.2 (SEM) vs. 3.8+/-0.3 micromol. kg(-1)x hr(-1) in the control subjects (P = 0.03), whereas transsulfuration was not 2.5+/-0.3 vs. 3.0+/-0.1 micromol. kg(-1) x hr(-1) (P = 0.11). The transmethylation rate was proportionally and significantly lower in the ESRD patients as compared with controls: 5.2+/-0.4 vs. 6.8+/-0.3 micromol. kg(-1) x hr(-1) (P = 0.02). Methionine fluxes to and from body protein were similar. CONCLUSIONS: The conversion of homocysteine to methionine is substantially (approximately 30%) decreased in hemodialysis patients, whereas transsulfuration is not. Decreased remethylation may explain hyperhomocysteinemia in ESRD. This stable isotope technique is applicable for developing new and effective homocysteine-lowering treatment regimens in ESRD based on pathophysiological mechanisms.     

Trapidil decreases the aggregation of platelets from heart transplant recipients ex vivo

Heart transplant recipients show platelet hyperaggregability, which may be related to the incidence of graft vasculopathy. We investigated whether trapidil can inhibit the aggregation of platelets from these patients. Platelet count, mean platelet volume (MPV), and adenosine diphosphate (ADP)-induced platelet aggregation were determined in 18 heart transplant recipients and 12 healthy subjects. Additionally, platelet-rich plasma from the patients was incubated with trapidil or with saline, prior to measuring ADP-induced aggregation. The MPV was significantly greater in patients compared to controls (9.4+/-1.1 vs 8.5+/-0.7 fL; P=.01), and ADP-induced platelet aggregation was significantly increased in patients compared to controls (81.2%+/-13.1% vs 69.6%+/-16.2%; P=.04, respectively). The trapidil-treated samples showed significantly decreased platelet aggregation compared to the control samples (24.2%+/-12.6% vs 66.7%+/-11.7%; P<.001). Platelets from heart transplant recipients showed an increased MPV and increased ADP-induced aggregation. Trapidil effectively reduced the ADP-induced aggregation ex vivo.     

Autologous platelet sequestration in patients undergoing coronary artery bypass grafting

OBJECTIVES: Blood conservation remains an important issue for patients undergoing cardiac surgery with cardiopulmonary bypass. Platelet sequestration (PSQ) is an aggressive autologous blood conservation method, whose effectiveness is still debated. The main objective of the present study was to evaluate whether PSQ reduces postoperative blood transfusion requirements in patients undergoing coronary artery bypass grafting (CABG) and to determine if PSQ is a cost-effective blood conservation method. MATERIAL AND METHODS: All adult patients admitted for CABG entered the study. Exclusion criteria were: recent blood transfusion (<7 days), a platelet count of 150x10(3)/microl or less, hematocrit less than 35% and body weight 50 kg or less. The sequestration was aim 20% or more of the total platelet plasma volume. The sequestration protocol was three sequestration cycles performed just prior to surgery. The concentrated platelet portion was reinfused after weaning from the cardiopulmonary bypass. Hundred seven parameters/patients were recorded. Sixty patients entered the study; 30 in the PSQ group and 30 controls (CTR). RESULTS: Patient characteristics, operation data, preoperative hematology and coagulation parameters did not differ between the groups. In the PSQ group a mean of 433+/-34 ml concentrated platelet portion was collected. The mean platelet count in the concentrated platelet portion was 749+/-157x10(3)/microl, resulting in a platelet yield of 28+/-6% (2040%). The average total chest tube blood loss was 423 ml (PSQ) compared to 858 ml (CTR), p<0.001. A greater number of CTR patients required blood transfusion postoperatively (23) compared to PSQ (3), P<0.001, and fluid requirements were also significantly increased in the control group, P<0.001. No statistical differences in hematology and coagulation parameters between the groups were observed. The hospital mortality was low and the incidence of postoperative complications was few and without group differences. Post-extubation gas exchange was better in PSQ patients compared to CTR. CONCLUSIONS: A preoperative PSQ of a minimum 20% of the total platelet plasma volume resulted in significantly lower postoperative blood loss and fluid and blood transfusion requirements compared to controls. Post-extubation gas exchange was also better after PSQ. Only one patient did not tolerate the sequestration. No other adverse effects of the procedure were observed.     

Heparin influences human platelet behavior in cardiac surgery with or without cardiopulmonary bypass

The objective was to investigate whether the platelet dysfunction in cardiac surgery is caused by hemodilution or by shear stress due to cardiopulmonary bypass (CPB). Platelet count and function were prospectively analyzed in two groups of patients undergoing cardiac surgery either with or without CPB (n = 40). In the first study (n = 20; 10 patients with and 10 without CPB), platelet counts were assessed at seven time points. In the second study (n = 20; 10 patients with and 10 without CPB), platelet function was studied with platelet aggregometry at different points during surgery: (a) after induction of anesthesia; (b) after sternotomy; and (c) 1 h after heparin. In the first study, the CPB group showed a significant decrease in platelet count starting after sternotomy (230 +/- 34 vs. 182 +/- 25, P < 0.05) and a maximum decrease at day 1 postoperative (96 +/- 34, P < 0.05). A similar observation was made in the non-CBP group. In the second study, a significant decrease of ADP (54 +/- 13% vs. 38 +/- 9%, P < 0.05), AA (76 +/- 16% vs. 22 +/- 14%, P < 0.05), and Collagen (66 +/- 13% vs. 37 +/- 11%, P < 0.05) induced platelet aggregation was observed at MOMENT d compared to the beginning of surgery in the CPB group. In the non-CBP group a significant decrease was observed in AA-induced platelet aggregation at MOMENT d (83% +/- 4 vs. 44% +/- 14, P < 0.05). The reduction in platelet count is similar with or without cardiopulmonary bypass and is due to pure hemodilution. Platelet function reduces significantly after heparin administration. Hemodilution and predominantly heparin are the causes of platelet dysfunction after cardiac surgery.     

Hyperhomocysteinemia, diabetes mellitus, and carotid atherosclerosis independently increase atherosclerotic vascular disease outcome in Japanese patients with end-stage renal disease

BACKGROUND: Patients with end-stage renal disease (ESRD) have high mortality from atherosclerotic/atherothrombotic vascular disease (AVD). However, the role of an elevated plasma total homocysteine (tHcy) level as a risk factor is uncertain in ESRD. METHODS: We enrolled 55 ESRD patients in a prospective follow-up study in order to evaluate the prognostic significance of their tHcy levels, common methylenetetrahydrofolate reductase (MTHFR) gene polymorphism, and other atherosclerotic risk factors, in combination with the results of B mode ultrasound for carotid arteries. RESULTS: Mean intima-media thickness of the common carotid artery (CCA-IMT) in ESRD patients was thicker than that in 102 age- and sex-matched healthy controls. Carotid plaque was more frequently present in patients compared with controls, as was calcified plaque more common in patients (p < 0.001). Plasma tHcy levels (mean +/- SD) in patients (39.1 +/- 27.2 nmol/ml) were higher than that (8.8 +/- 2.7 nmol/ml) in controls (p < 0.001). Folic acid was the major determinant of elevated tHcy levels in ESRD patients. During the follow-up period of 31 +/- 3 months, 14 patients had one or more AVD complications, and 10 consequently died from AVD causes. Proportional hazards modeling showed that 5-year intervals of age (relative risk of 2.95, 95% CI 1.62 - 5.37), 10 nmol/ml intervals of tHcy levels (relative risk of 2.31, 95% CI 1.31 - 4.08), and presence of diabetes mellitus (relative risk of 6.62, 95% CI 1.07 +/- 40.8) were independent predictors of future AVD events, and tHcy levels (relative risk of 2.67, 95% CI 1.29 - 5.52) and age (relative risk of 2.10, 95% CI 1.15 - 3.83) were those of AVD mortality. We also found a significant association between carotid plaque prevalence and AVD events (X(2) = 11.6, p = 0.001). CONCLUSION: Hyperhomocysteinemia, diabetes mellitus, and carotid atherosclerosis appeared to contribute independently to increase the risk of AVD outcome in Japanese patients with ESRD.     

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.     

The effects of nitric oxide on coagulation during simulated extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is associated with profound alterations in hemostasis, with platelet dysfunction often being implicated as a causative factor for transfusion. Nitric oxide (NO) has shown to be a rapid yet temporary inhibitor of platelet function. The purpose of this study was to evaluate the effects of NO on platelet number and function in an in vitro ECMO model. Eight silicone membrane oxygenators were primed with fresh, heparinized, bovine blood and allowed to circulate for 48 hours. The treatment group (NO) consisted of four oxygenators that had an end concentration of 20 ppm NO applied to the sweep gas. Platelet counts, methemoglobin levels, plasma-free hemoglobin levels, activated clotting times, and thromboelastographic (TEG) studies were performed at baseline, 1, 6, 12, and 24 h. Scanning electron microscopy (SEM) was performed on sample areas from each oxygenator. The treatment group maintained an average of 25% higher platelet counts than the control group (85.1 +/- 32.0, x 10(3) versus 66.5 +/- 30.9 x 10(3)) although statistical significance was not achieved. Methemoglobin levels were significantly elevated in the treatment circuit at hours 12 and 24 (p < .05). This could be attributed to the lack of a biological interaction that would break down this toxic by-product. TEG indices steadily declined in both groups from baseline (-0.4 +/- 3.6) to (-17.2 +/- 3.3 p < .0007) treatment and (-20 +/- 4.5, p < .0001) control, with the treatment circuit maintaining only slightly improved indices over the most of the study. SEM data showed increased fibrin and cellular deposits in the control group (p = .05) when compared with the treatment group. NO added to the sweep gas of a simulated ECMO circuit at 20 ppm had little effect on the maintenance of platelet number and function.     

Apoptosis and rejection in rat intestinal transplantation: correlation with FK506 doses and donor specific bone marrow infusions.

BACKGROUND: Our purpose was to investigate the occurrence and the evolution of apoptosis of enterocytes during acute and chronic rejection in an experimental model of allogeneic heterotopic small bowel transplantation (SBTx). METHODS: Forty-five rats were divided in 10 experimental groups according to the dose of FK506 administration and donor bone marrow infusions (DBMI). Groups 1 and 2 did not received BMI. Groups 3 and 4 received 150x106 cells at day 0, groups 5 and 6 received 75x106 cells at days 0-4, groups 7 and 8 received 75x106 cells at days 4 and 10, and groups 9 and 10 received 30x106 cells at days 4, 10, 15, 20, and 25. Animals of groups 1, 3, 5, 7, and 9 were immunosuppressed with 0.5 mg/kg FK 506, although the remaining groups with 1 mg/kg FK 506, from day 0 to 4 after transplant. Fragment end labeling of DNA was used to detect apoptosis. RESULTS: The number of apoptotic cells detected was highest at day 15 (184+/-154) and then progressively decreased thereafter (day 30=159+/-197; day 45=80+/-167; day 60=0). The number of apoptotic enterocytes was found increased during mild (151+/-108) and moderate (281+/-161) allograft rejection, although a low apoptotic rate was observed in cases without rejection (59+/-13) and during severe (53+/-131) and chronic rejection (46+/-136). Furthermore the number of labeled cells was found inversely correlated with fibrosis (P<0.0001). There was no correlation between apoptosis and the presence or absence of DBMI; however, at day 15 rats receiving 1 mg/day of FK 506 had a significantly lower number of apoptotic cells detected (127+/-103 vs. 233+/-174; P<0.02). CONCLUSIONS: In this study the number of apoptotic cells correlated positively with mild and moderate rejection episodes. In case of severe and chronic rejection a low apoptotic rate was found due probably to extensive necrosis and fibrosis of the mucosa. These data suggest an important role of apoptosis in acute and chronic intestinal rejection in a rat model of intestinal transplantation. Determination of apoptosis in allografts might represent an early sign of small bowel rejection and a useful marker in defining the degree of rejection and its outcome/prognosis.