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G Rock

Publications and source records attributed to G Rock.

At least 37 records · Page 2Linked to original sources
PubMed2001

A novel, automated method of temperature cycling to produce cryoprecipitate.

BACKGROUND: Cryoprecipitate continues to find wide application in transfusion practice. Current AABB standards call for a minimum of 80 units (U) of factor VIII and 150 mg of fibrinogen per bag of cryoprecipitate. However, individual cryoprecipitates can vary greatly in content, with as many as 20 different factors known to affect the yield. STUDY DESIGN AND METHODS: Plasma was processed in a new, rapid, automated device (CryoSeal, Thermogenesis) with computer-controlled temperature cycling to produce cryoprecipitate. RESULTS: In repeat runs (n = 20), the automated procedure yielded a product containing 184 mg of fibrinogen and 158 U of factor VIII in 55 minutes. Additional studies using plasma pools to compare the quality of the machine-generated products to those of traditionally prepared cryoprecipitate showed comparative recoveries of 182 and 187 mg of fibrinogen and 172.1 and 129.7 U of factor VIII and no significant difference in the levels of plasminogen, protein C, or protein S. CONCLUSION: The new system offers an automated method of cryoprecipitate production in which the steps involved in temperature cycling are initiated sequentially, producing within 1 hour a preparation that is equivalent to standard cryoprecipitate.

Cryopreservation↗
PubMed2001

Effects of different concentrations of anticoagulant on the in vitro characteristics of autologous whole blood.

BACKGROUND: Routinely, 450 mL of blood is collected into 63 mL of CPDA-1, for a final anticoagulant:blood ratio of approximately 1:7 in a whole-blood autologous unit. If less than 300 mL of blood is to be collected, the AABB standards suggest that there should be a proportionate decrease in anticoagulant. Data from an autologous blood program showed a range in volume from 92 mL to 667 mL per bag, which reflects an anticoagulant:blood ratio of 2:1 to 1:10. STUDY DESIGN AND METHODS: To determine the effects of these ratios on the in vitro function of RBCs at various anticoagulant ratios, blood was collected into different amounts of anticoagulant, and various measurements were made during storage. RESULTS: The number of RBCs and the MCV remained constant over time, regardless of the anticoagulant dilution used. Plasma free Hb increased with time with all dilutions. At a 1:2 ratio, it rose from 734 mg per L on Day 1 to 1805 mg per L on Day 35, and at 1:8, it was 355 mg per L for Day 1 and 854 mg per L on Day 35. Plasma sodium decreased and the potassium increased over time with all dilutions. From Day 1 to Day 35, there was a nine-fold increase in potassium at both the 1:2 and 1:8 dilutions (2.4 to 22.9 mmol/L, 3.2 to 29.6 mmol/L, respectively). The LDH increased over time and the pH decreased in all of the dilutions. Osmotic fragility remained constant at the 1:8 dilution but decreased at all of the other dilutions with storage, with 44-percent fragility on Day 35 at the 1:2 ratio. The WBC and platelet counts decreased consistently over time. Overall, 1 percent of the autologous units were below the cutoff volume of 300 mL at which an adjustment of the anticoagulant volume is required. CONCLUSION: Plasma Hb and plasma potassium concentrations are considerably higher in low-volume units, which indicates that deviation from standard collection procedures is deleterious to RBCs.

Adenine↗
PubMed2001

Inhibitors of von Willebrand factor-cleaving protease in thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP), characterized by platelet thrombi in the arterioles and capillaries, is associated with antibodies that inhibit the activity of von Willebrand factor (vWF)-cleaving protease. Using a modified Bethesda method, we studied the inhibitor titers in patients who participated in the trial conducted by the Canadian Apheresis Group. Among the 41 patients investigated, the inhibitor titers at presentation were 1.4 +/- 1.7 U/mL (range -0.2-6.2 U/mL). Thirty-one patients (76%) had a titer > or = 0.2 U/mL, 8 patients (20%) had a titer > or = 2.0 U/mL but none had a titer > or = 10 U/mL. Among the 33 patients with an inhibitor titer < 2.0 U/mL (low titer group) and the 8 patients with an inhibitor titer > or = 2 U/mL (high titer group), 20 (61%) and 8 (100%) respectively had a platelet count < 25x10(9)/L (P = 0.04). Neurological abnormalities were among the presenting problems in 19 (58%) of the low titer and 6 (75%) of the high titer groups. Among the 23 patients who were randomized to plasma exchange, 5 patients had an inhibitor titer > or = 2 U/mL and none responded at the end of the first treatment cycle, while 8 of the 18 patients (44%) with a titer < 2 U/mL responded. This study shows that inhibitors of vWF-cleaving protease are of low titers in most cases of acquired TTP. A higher inhibitor titer is associated with a more advanced stage of the disease and may delay the response to plasma exchange.

ADAM Proteins↗
PubMed2000

Editorial.

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Journal Article↗
PubMed2000

Editorial.

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Journal Article↗
PubMed2000

The supply of blood products in 10 different systems or countries.

Countries vary greatly in their ability to produce their own blood products including albumin and IVIgG. Part of this variability depends on the supply of plasma within the country. As has been seen most recently in the UK, the quality of the plasma and its acceptability for plasma fractionation must also be considered. Therefore concerns regarding the quality of the plasma have been added to those regarding the quantity.Only a few countries are nationally self sufficient in plasma. This has a marked effect on blood product availability and therefore the ability to treat patients. Unlike most pharmaceuticals, the plasma fractionation industry must rely, for its raw products, on plasma obtained from blood donors. As such this puts it in a potentially compromised situation since neither the supply nor the quality of the raw material can be assured and both of those will vary with time. This paper reviews the processes through which blood products are made available in 10 different systems including: Canada, England, France, Italy, Norway Scotland, Sweden, Switzerland, South Africa and USA. A series of specific questions were posed and the responses received from the various coauthors and other respondents provide comparative data on blood product availability in different areas of the world.

Blood Banks↗
PubMed2000

Quality assurance of progenitor cell content of apheresis products: a comparison of clonogenic assays and CD34+ enumeration. The Canadian Apheresis Group and Canadian Bone Marrow.

The most common methods used for evaluation of the haematopoietic stem cell content of peripheral blood apheresis products are the colony forming cell assay and the enumeration of CD34+ cells by flow cytometry. The Canadian Apheresis Group and the Canadian Bone Marrow Transplant Group established a multicentre study to compare the reproducibility of colony forming cell assays and CD34+ enumeration by flow cytometry in six transplant centres routinely performing haematopoietic stem cell apheresis. Over a 5-month period in 1996, 31 fresh apheresis samples were shipped by overnight courier for testing at six centres to perform CD34+ enumeration by flow cytometry and clonogenic assays. The mean coefficient of variation and range for the following assays were: cell count 36% (2.6-148%), CFU-GM 82% (46-123%), CD34+ absolute/kg 60% (14-174%) and CD34+ per cent 42% (12-84%). The wide variation in cell count in this pilot study highlights the difficulties related to provision of samples for quality assessment programmes. Results showed poor interinstitutional reproducibility even among selected samples with similar cell counts for both CFC and CD34+ assays demonstrating the need for development and implementation of an interinstitutional quality assurance programme for haematopoietic stem cell assessment. Provision of a reliable source of testing material will be a necessary next step.

Antigens, CD34↗
PubMed2000

Feasibility of blinding in a randomized controlled trial comparing preoperative autologous blood donation and acute normovolemic hemodilution in adult cardiac surgery.

BACKGROUND: Acute normovolemic hemodilution and preoperative autologous donation have been shown to be effective techniques for decreasing the exposure of patients to allogeneic blood during cardiac surgery. They have not, however, been compared to each other, because of perceived difficulties in blinding in such a clinical study. The feasibility of blinding was tested in a pilot trial. STUDY DESIGN AND METHODS: Ten patients were randomly assigned to undergo preoperative autologous blood donation or acute normovolemic hemodilution during cardiac surgery. Patients were blinded during this process by shielding of the arm and by insertion of an intravenous line in each patient. Every attempt was made to blind the clinical staff during and after surgery. The effectiveness of this blinding was determined by using a questionnaire. RESULTS: In the 10 cases, six patients, four surgeons, and one anesthetist answered, "I do not know," with respect to whether preoperative autologous blood donation had occurred. The remaining people interviewed believed the blinding was unsuccessful. However, correct answers were given by 75 percent of the patients (95% CI, 19-99%), 83 percent of the surgeons (95% CI, 36-99.6%), and 66 percent of the anesthetists (95% CI, 29.9-92.5%). The frequency of correct answers did not differ significantly from the 50 percent expected by chance, but the CIs are wide. CONCLUSIONS: Blinding of patients and all members of the surgical team during both the preoperative donation process and acute normovolemic hemodilution in the operating theater was successful most of the time, as the frequency of correct answers did not differ significantly from the 50 percent expected by chance. However, more accurate estimates of the success of blinding require a study with a larger sample. It is possible that, with a larger series, the physician's ability to determine patient assignment would be significantly better than that by chance alone.

Adult↗
PubMed2000

An in vitro method for predicting the efficacy of WBC separation using different starch preparations and anticoagulant ratios.

BACKGROUND: Separation of blood components depends on a number of factors, including the viscosity of the plasma and the number and size of the various cellular elements. To enhance granulocyte collection, it is common practice to alter the plasma environment by the addition of sedimenting agents such as hydroxyethyl starch. Recently, because of its prolonged persistence in the circulation, the higher-molecular-weight form of hydroxyethyl starch, Hespan (HP), has been replaced by the lower-molecular-weight form, pentastarch (PS). However, the yield appears to be lower. A rapid in vitro approach was used to permit comparison of the efficiency of separation of WBCs by the use of PS and HP and different ratios of anticoagulants that also alter the sedimenting characteristics of blood. STUDY DESIGN AND METHOD: Blood from individual persons was collected into sodium citrate at ratios of 1:8, 1:12, and 1:16. Samples were evaluated either before or after the addition of PS or HP and after centrifugation. RESULTS: The addition of HP increased the sedimentation rate to at least four times that of plasma (10.9 vs. 47.9 mm); PS approximately doubled the rate. Viscosity was altered by the introduction of either starch. These changes (ranging from a rate of 4.2 in HP with a 1:16 anticoagulant to 3.6 in PS with a 1:8 ratio of anticoagulant) reflected the anticipated effects of anticoagulant dilution and carbohydrate addition. Granulocyte recovery was highest, with a 1:12 anticoagulant ratio in all tests with HP producing the greatest yield (HP, 101%; PS, 89%; control, 78%). CONCLUSION: HP is far more effective than its lower-molecular-weight substitute PS in the generation of granulocytes in the buffy coat of whole blood. This method provides a simple, rapid, in vitro approach to evaluating the separating efficiency of solutions.

Anticoagulants↗
PubMed2000

Thrombotic thrombocytopenic purpura treatment in year 2000.

BACKGROUND AND OBJECTIVE: For several decades clinicians worldwide considered TTP a severe and frustrating therapeutic problem. Fortunately, however, the prognosis of TTP patients has greatly benefited from the use of plasma manipulation techniques, particularly plasma-exchange (PE), so that the overall rate of complete responses currently ranges between 70-85% and may even exceed these figures. Despite this dramatic improvement, a number of questions remain concerning the best treatment for TTP patients. Analyzing acquired data and discussing future perspectives, this review will address the following key issues: is PE really the treatment of choice for TTP and what is the role of PE with cryosupernatant? what is the role of all the drugs which are commonly combined with PE, antiplatelet drugs and steroids in particular? what, if any, is the role of cytotoxic agents, especially vincristine? is there a treatment for PE-resistant patients? does secondary TTP need different treatments? DESIGN AND METHODS: The authors have been involved in the study and treatment of TTP for years; furthermore, they extensively searched the PubMed database of the National Library of Congress through the Internet. INTERPRETATION AND CONCLUSIONS: PE remains the treatment of choice for TTP. A large randomized trial now in progress will assess whether exchange with cryosupernatant plasma can improve treatment efficacy. The administration of antiplatelet drugs in combination with PE was fiercely debated over the past years but seems indicated both in acute TTP and as a prophylactic treatment to prevent relapses. It appears that steroids cannot be avoided, especially in light of the latest findings on TTP pathogenesis, but only specific trials will assess the optimal cortisone type and dose. Presently, different treatments can be suggested only to patients failing to respond to PE, while no specific therapy can be indicated for secondary TTP, which usually has a very poor prognosis. Finally, we would like to stress that only international co-operative (multicenter) trials on large series of patients will be able to shed light on a still obscure, if fascinating, disease. Our hope and wish is that the new century will see TTP among the diseases defeated by man's clever mind and heart.

Adrenal Cortex Hormones↗
PubMed1999

Treatment of Guillain-Barré syndrome: a cost-effectiveness analysis.

Acute Guillain-Barré syndrome is the most common cause of neuromuscular paralysis. Plasma exchange and intravenous immune globulin (IV IgG) are both effective treatments for this condition and the purpose of this report was to compare the cost-effectiveness of these two modalities. A MEDLINE search was performed to identify randomized studies that compared the use of IV IgG and plasma exchange for treatment of acute Guillain-Barré syndrome to determine if one modality was more effective and/or safer for the management of this condition. A decision analysis was structured around the alternatives facing neurologists who must choose a treatment regimen for patients diagnosed with acute Guillain-Barré syndrome who require active therapy. Cost information was obtained directly from product manufacturers and hospital sources. Two head-to-head trials comparing the effectiveness of plasma exchange and IV IgG for treatment of acute Guillain-Barré syndrome determined that there was insufficient evidence to suggest one therapy was more effective than the other; therefore, a cost minimization analysis was performed. The costs per patient of plasma exchange and IV IgG for the treatment of acute Guillain-Barré syndrome were $6,204 and $10,165, respectively. A sensitivity analysis determined the model was sensitive to the cost of IV IgG. The cost savings per patient treatment for the use of plasma exchange varied from $304 to $6,625 depending on the IV IgG product selected. Plasma exchange and IV IgG are both effective treatments for Guillain-Barré syndrome. However, our analysis determined plasma exchange on average was almost $4,000 less costly per patient than IV IgG. Further research is required to determine the impact of patient and physician preferences on the treatment of this disorder.

Canada↗
PubMed1999

Nutricel as an additive solution for neonatal transfusion.

Red cell concentrates stored in additive solutions have limitations for use in the pediatric population. Our survey of 10 pediatric institutions found that Nutricel supernatant was often removed prior to infusion. Examination of packed red cells showed a potassium concentration in excess of 15 mmol/l by day 7 in AS-3 and 40 mmol/l by day 35. Comparison with cells stored in CP2D and CPDA1 showed that the total mass of potassium was highest in AS-3 (5.6 mmol/l) as was the phosphate. The total mass of citrate and glucose was considerably increased in the AS-3 system at 1.73 mmoles and 3.23 mmoles. All had a pH less than 6.6 at day 35. The high concentration of potassium in AS-3 raises concern for the potential for hyperkalemic dysrhythmias during massive transfusion while the citrate load has clinical implications for divalent cation homeostasis during rapid infusion or exchange; the glucose may induce hyperglycemic sequelae.

Erythrocyte Transfusion↗
PubMed1999

Characterization of platelet glycoproteins and platelet/endothelial cell antibodies in patients with thrombotic thrombocytopenic purpura.

Platelets and sera from 12 patients with thrombotic thrombocytopenic purpura (TTP) and 12 healthy normal control subjects were examined. As determined by quantitative flow cytometry, prior to plasma exchange therapy platelet surface glycoprotein (GP) Ib levels were similar in TTP patients and normal controls (mean 20 188 and 20 226 molecules/platelet, respectively). Platelets from patients with TTP did, however, have significantly reduced levels of GPIIb/IIIa prior to plasmapheresis (mean 36 348 v 52 505 molecules/platelet in controls; P = 0.0004) and of GPIV (mean 13 321 v 26 212 molecules/platelet in controls; P = 0.0002). An increase in activated platelets, as determined by CD62 expression, was observed in 82% of patients. Increased platelet-associated immunoglobulins and/or complement was also seen in approximately 60% of the patients. In general, with return of platelet counts to normal levels following seven plasmaphereses, the above abnormalities were reversed, although often not to normal levels. Western blot analysis indicated the presence of antibodies reactive to platelet GPIV (88 kD) in 70% of pretreatment sera from patients with TTP; a similar band was observed in 80% of patient sera against microvascular endothelial cells. Immunofluorescence microscopic examination indicated the presence of antibody in pretreatment sera from patients with TTP to microvascular (73%) and large vessel (36%) endothelial cells. As measured by an indirect flow cytometric assay, pretreatment sera from 55% of patients with TTP were reactive with large vessel endothelial cells and 100% reacted with microvascular endothelial cells; reactivity was significantly greater against the microvascular endothelial cells (P = 0.0048) and was reduced following plasma exchange therapy. These results indicate abnormalities in platelet glycoprotein expression in TTP and suggest that anti-platelet and anti-endothelial cell antibodies play a role in the thrombocytopenia and vasculitis characteristic of this disorder.

Adult↗
PubMed1999

Clinical evaluation of a staphylococcal protein A immunoadsorption system in the treatment of myasthenia gravis patients.

BACKGROUND: The role of plasma exchange is well established in the management of myasthenia gravis, an autoimmune disorder characterized by muscle weakness and caused by circulating IgG antibodies with specificity against the acetylcholine receptor. Plasma antibody removal by conventional means, however, is nonselective and uses replacement fluids (chiefly, albumin solution) derived from human plasma. STUDY DESIGN AND METHODS: The Canadian Apheresis Group undertook a study at two Canadian apheresis centers to clinically evaluate a staphylococcal protein A immunoadsorption system (EXCORIM) in myasthenia gravis patients. RESULTS: The immunoadsorption system was safe and well tolerated. Ten of 12 patients had improvement in their neurologic status, as measured by a 20-point scoring system. The mean improvement in the weakness score was significant for the group (p = 0.0013). CONCLUSION: Patients with myasthenia gravis respond to treatment with plasma immunoadsorption. Further studies are required for a cost-benefit analysis.

Adult↗
PubMed1998

The Canadian experience using plasma exchange for immune thrombocytopenic purpura. Canadian Apheresis Group.

The effect of plasma exchange (PE) for the treatment of acute immune thrombocytopenic purpura (ITP) was assessed both through an analysis of the use of PE for ITP in Canada from 1980 to 1997, and in a study of 23 patients with acute ITP. Thirteen of these 23 patients were treated by PE (10 were exchanged with albumin and three with FFP) plus prednisone and 10 were treated with prednisone alone. At the 6 month follow-up, 11 of 19 patients were considered complete responders and six were considered partial responders. The difference in response rates between the PE and prednisone groups was not statistically significant. All patients had platelet specific antibodies at the time of entry into the study. Antibody concentration was reduced following PE in 10 of the 12 patients tested, and a response to PE was seen in all 10 patients who had a reduction in the level of platelet antibody. In contrast, antibody levels did not change in the patients who received steroid treatment only. This observation suggests that antibody removal may be of direct benefit in patients with ITP. Analysis of our results indicated that PE increased the length of time before splenectomy but did not alter the need for splenectomy. Short term benefits of PE were accomplished with no increase in morbidity or mortality which confirms that PE is a safe procedure in patients with ITP.

Acute Disease↗
PubMed1998

Laboratory abnormalities in thrombotic thrombocytopenic purpura. Canadian Apheresis Group.

Thrombotic thrombocytopenic purpura is an uncommon disorder that requires prompt recognition and intervention to prevent death. To date, information regarding the classic laboratory abnormalities in the disease has been derived from small numbers of patients whose laboratory tests have been done at many different sites. We report the laboratory findings in 135 patients who presented with thrombotic thrombocytopenic purpura to 17 Canadian centres. 50 men and 85 women had a mean platelet count of 25.3+/-19.4x10(9)/l. The initial platelet count correlated with mortality; 32% of patients with a platelet count of 20x10(9)/l or less died compared with 18% of patients with a platelet count >20x10(9)/l (P=0.058). The platelet-associated IgG was elevated in 88% at presentation whereas the indirect platelet suspension immunofluorescence test was positive in only 18%, 93% of the sera showed reactivity against platelets following protein blotting. All sera tested also showed reactivity against endothelial cells. Immune complexes were seen in all patients, whereas the platelet aggregating factor was detected in 59%. Although the von Willebrand factor was elevated in the majority of patients at entry, the multimer pattern was variable and showed no predictive pattern. Renal dysfunction was common (18%).

Adolescent↗