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Biomedical subjects

S B Raman

Publications and source records attributed to S B Raman.

11 recordsLinked to original sources
PubMed2001

Analysis of coagulation changes associated with supraceliac aortic crossclamping using thromboelastography.

INTRODUCTION: The etiology of the coagulation changes seen with supraceliac (SC) aortic crossclamping (AXC) remains controversial; both primary fibrinolysis and clotting factor consumption have been implicated. The cause of these changes was investigated with thromboelastography (TEG), a test that measures the viscoelastic properties of thrombus to dynamically assess coagulation and fibrinolysis. METHODS: Eight pigs underwent SC AXC for 30 min; 5 pigs undergoing 30 min of infrarenal (IR) aortic clamping served as controls. Blood was drawn before AXC, before unclamping, and 5 and 60 min after unclamping. Thromboelastography and standard coagulation tests [prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and platelet count] were performed. Measured TEG parameters included fibrinolytic index (a measure of fibrinolysis), r value (a reflection of intrinsic coagulation cascade activity), and the alpha angle and K values (measures of the speed of solid clot formation). Repeated measures ANOVA and t test were used for statistical analysis. RESULTS: There was no difference in the fibrinolytic index at any time point between the two groups. Increased activity of the intrinsic coagulation cascade during SC clamping was reflected by a lower R value just before unclamping (12.6 +/- 3.0 vs 20.0 +/- 3.0, P = 0.048) compared to IR AXC. Decreased speed of solid clot formation was noted 5 min after unclamping in the SC group but not the IR group [as defined by an increased K value (ANOVA, P = 0.010) and a decreased alpha angle value (ANOVA, P = 0.005)]. Fibrinogen levels were lower in the SC than in the IR group 5 (P = 0.013) and 60 min after unclamping (P = 0.02), but PT, PTT, and platelets did not differ between the groups at any time points. CONCLUSIONS: Thirty minutes of SC AXC does not result in fibrinolysis. There is increased clotting activity during SC clamping followed by decreased speed of clot formation and decreased fibrinogen levels after unclamping. These changes are consistent with clotting factor consumption.

Animals↗
PubMed1997

Transplantation in patients with multiple myeloma: a multicenter comparative analysis of peripheral blood stem cell and allogeneic transplant.

We performed a multicenter comparative analysis of autologous peripheral blood stem cell transplantation (PBSCT) and allogeneic bone marrow transplantation (alloBMT) in multiple myeloma. Forty-eight consecutive patients received either PBSCT (24 patients) or alloBMT (24 patients) at one of three institutions in the study group. Preparatory regimens consisted of melphalan and total body irradiation (TBI) or melphalan alone in the PBSCT group. The alloBMT group received one of four regimens: cyclophosphamide and TBI; cyclophosphamide, VP-16 and 1,3-bis(2-chloroethyl)-1-nitrosourea (CVB); busulfan and cyclophosphamide (BU/CY) and total marrow irradiation (TMI); or melphalan and TBI. Procedure-related mortality was 12.5% for the PBSCT group and 25% for the alloBMT group. With a median follow-up for survivors in the PBSCT and alloBMT groups of 11 months (range, 4-46) and 15 months (range, 2-84 months), respectively, there was no significant difference in median overall survival (33.5 versus 38.6 months, p = 0.7637) or event-free survival (16.7 versus 31 months, p = 0.8450). There was, however, a plateau in survival at 40% in the alloBMT group. No plateau in survival was seen in the PBSCT group. Clinical relapses occurred as late as 39 months posttransplant. Patients have survived up to 28 months postrelapse.

Adult↗
PubMed1997

A new rat model of thrombotic focal cerebral ischemia.

We developed a fibrin-rich thrombotic focal cerebral ischemic model with reproducible and predictable infarct volume in rats. In male Wistar rats (n = 77), a thrombus was induced at the origin of the middle cerebral artery (MCA) by injection of thrombin via an intraluminal catheter placed in the intracranial segment of the internal carotid artery (ICA). Thrombus induction and consequent ischemic cell damage were examined by histopathological analysis and neurological deficit scoring, and by measuring changes in cerebral blood flow (CBF) using laser-Doppler flowmetery (LDF), perfusion-weighted imaging (PWI), and by diffusion weighted imaging (DWI). Histopathology revealed that a fibrin-rich thrombus localized to the origin of the right MCA. Regional cerebral blood flow (rCBF) in the right parietal cortex was reduced by 34-58% of preinjection levels after injection of thrombin in rats administered 30 U of thrombin (n = 10). Magnetic resonance imaging (MRI) showed a reduction in CBF and a hyperintensity DWI encompassing the territory supplied by the right MCA. The infarct volume in rats administered 80 U of thrombin was 31.29 +/- 12.9% of the contralateral hemisphere at 24 h (n = 13), and 34.7 +/- 16.4% of the contralateral hemisphere at 168 h (n = 6). Rats administered 30 U of thrombin exhibited a hemispheric infarct volume of 34.0 +/- 14.5% (n = 9) at 24 h and 29.7 +/- 13.9% (n = 8) at 168 h. In addition, thrombotic rats (n = 3) treated with recombinant tissue plasminogen activator (rt-PA) (10 mg/kg) 2 h after thrombosis showed that CBF rapidly returned towards preischemic values as measured by PWI. This model of thrombotic ischemia is relevant to thromboembolic stroke in humans and may be useful in documenting the safety and efficacy of thrombolytic intervention as well as for investigating therapies complementary to antithrombotic therapy.

Animals↗
PubMed1994

Coagulation defects resulting from ambient temperature-induced hypothermia.

Ambient temperature-induced hypothermia noted in trauma patients is frequently accompanied by a bleeding diathesis despite "laboratory normal" coagulation values. To document this impression, the following experiment was conducted. Coagulation studies and platelet function studies were performed in ten minipigs during induced whole body hypothermia (40 degrees C to 34 degrees C) and rewarming. Cooling was achieved in 2 to 3 hours and rewarming took 4 to 5 hours. In addition, similar coagulation and platelet function studies were conducted on plasma samples from the same animals that were cooled and then rewarmed in a water bath. Platelet counts and function as measured by Sonoclot analysis and aggregation did not decrease significantly with hypothermia in either model. Plasma cooled in a water bath demonstrated abnormal PT and aPTT (p < 0.001). Whole body hypothermia demonstrated abnormal bleeding time and PT (p < 0.001). Ambient temperature-induced hypothermia produced significant coagulation defects in a porcine model. Some of the coagulation defects were most pronounced during rewarming.

Animals↗
PubMed1989

Primary fibrinolysis in acute monocytic leukemia.

We present the case of a young man with acute monocytic leukemia (French-American-British classification:M5) and systemic hyperfibrinolysis with severe bleeding. Although fibrinolysis is usually mild and secondary to disseminated intravascular coagulation, its role as a primary and dominant factor in rare cases of leukemia warrants that its presence be sought as a cause of abnormal bleeding. Decreased serum plasminogen and increased serum plasmin determined by synthetic substrate assay and a negative protamine paracoagulation test are crucial findings. Use of high-dose epsilon-aminocaproic acid was effective in treating this complication. A transient increase in fibrinolytic activity coincident with the early effect of antileukemic treatment suggested that plasminogen activator and/or fibrinolytic protease substances were released from leukemic cells. Fibrinolytic activity subsequently disappeared with reduction in the population of leukemic cells.

Adult↗
PubMed1983

Nature of intracytoplasmic crystalline inclusions in myeloma cells (morphologic, cytochemical, ultrastructural, and immunofluorescent studies).

The authors describe a 70-year-old woman with multiple myeloma and adult Fanconi syndrome. A monoclonal protein of IgA heavy-chain class and kappa light-chain class was demonstrable in the serum. Urine immunoelectrophoresis showed the presence of kappa light chains. Bone marrow aspirate showed increased plasma cells with large bundles of pink-staining Auer-rod-like crystals in their cytoplasm. These crystals failed to stain with Sudan black B, peroxidase, esterase, and PAS, but showed strong acid phosphatase and beta-glucuronidase positivity. Ultrastructural studies showed them to have a fibrillar and an unusual cross-striated pattern. Immunofluorescent studies showed strong IgA and kappa activity in the cytoplasm of the tumor cells, but the fluorescence was absent in the region of the crystals, which were identified easily by their negative birefringence. The authors interpret these observations to indicate that the intracytoplasmic crystals in this case are of lysosomal origin.

Aged↗
PubMed1981

Essential thrombocythemia with transition into acute leukemia.

A 57-year-old black man with sustained platelet count of 2 million/mm3 and evidence of intermittent gastrointestinal bleeding was diagnosed as having essential thrombocythemia. Studies of bone marrow morphology, platelet aggregation, and other variables were confirmatory of the disease. The patient was treated briefly with low doses of Myleran for less than three weeks. He was then lost to follow-up study. Approximately 16 months later he reappeared complaining of recurrent nose bleeds. He was found to be pancytopenic and diagnosis of acute leukemia was made on the basis of bone marrow aspiration.

Acute Disease↗