Search PubMed⌕ Search

Biomedical subjects

T L Simon

Publications and source records attributed to T L Simon.

At least 37 records · Page 2Linked to original sources
PubMed1992

Evolution in indications for blood component transfusion.

Indications for blood components are changing but continue to be based on a combination of clinical assessment and laboratory data. In the perioperative setting, some decisions must be made before laboratory data are available. To prevent the inappropriate usage of blood components, prophylactic or expectant treatment should be limited. In red cell transfusion, physiologic indices of oxygen utilization may soon supplement hemoglobin/hematocrit levels in clinical decision making. Less progress has been made in transfusion for hemostasis. Well-designed clinical studies are needed to answer remaining questions; in the interim, nationally accepted guidelines are available to assist clinicians in their decisions.

Adult↗
PubMed1992

The 1989 Comprehensive Blood Bank Survey of the College of American Pathologists.

The 1989 Comprehensive Blood Bank Survey included four additional samples for a total of eight antibody detection and identification challenges. The remainder of the survey was unchanged from prior years. Performance on the graded portions has remained good, with only occasional "problem" samples. For this survey year, the discrepant results were as follows: (1) a D-positive sample not reaching 95% consensus of D typing due to a strong positive direct antiglobulin test; (2) failure of 7% of extent 3 laboratories to identify anti-K in the presence of anti-c; and (3) continued, but lessened "identification" of anti-E, which was not present. The ungraded samples continued to provide educational challenges, and supplemental questions were used to survey current practices.

Blood Banks↗
PubMed1991

In vitro evaluation of a new dual screen microaggregate filter.

We compared a new second generation 40/150 mum dual screen microaggregate filter with a currently available 40 mum screen microaggregate filter. The evaluation included comparison of filter flow rate, capacity, degree of microaggregate removal, degree of leukocyte removal, and extent of filtration-induced hemolysis. We also studied the effect of both devices on filtration of stored platelet concentrates. The 40/150 mum dual screen microaggregate filter showed results comparable to that of the control screen filter following filtration of various types of units of red blood cells as well as units of stored platelet concentrates. Importantly, mean flow rates with the new 40/150 mum filter of 45 g/min after gravity filtration of 1600 mL of blood, make the filter suitable for use in trauma or other massive transfusion settings. We conclude that this new second generation microaggregate filter is suitable for use in clinical transfusion practice.

Evaluation Studies as Topic↗
PubMed1991

Collection of platelets with a new cell separator and their storage in a citrate-plasticized container.

A new apheresis device using microprocessor control for the collection of a high-purity single-donor platelet concentrate was evaluated, as was the storage of platelets for up to 5 days in a citrate-plasticized polyvinylchloride blood bag. The study was conducted in three phases: collection of platelets for in vitro studies and determination of donor safety; autologous transfusion of platelets in healthy volunteers; and transfusion of platelets in patients requiring platelet transfusion therapy. Donors had mild hypocalcemia and minimal changes in blood counts except for a platelet count reduction from 288 +/- 50 x 10(3) (288 +/- 50 x 10(9)/L) to 217 +/- 43 x 10(3) per microL (217 +/- 43 x 10(9)/L). A mean of 3.36 +/- 1.24 x 10(11) platelets was collected in the mean volume of 214 mL with red cell and white cell contamination in the range of 10(7). Morphology and aggregation were as described previously in stored platelets. Platelet survival data in eight subjects showed a mean recovery of 61 +/- 11 percent and mean survival of 5.03 +/- 1.07 days by a weighted-mean model. Patients transfused with platelets had mean increments of 23,000 immediately and of 8000 at 24 hours; corrected count increments were 6000 at 1 hour and 4000 at 24 hours. The platelets were successful in providing hemostasis to these patients. Clinically useful 5-day-stored platelets are obtained by using this apheresis technology with a functionally closed system and a citrate-plasticized blood bag.

Blood Component Removal↗
PubMed1991

A prospective study of blood donations in healthy elderly persons.

Iron stores were observed in 57 healthy elderly volunteers, between 63 and 77 years of age, who donated 5 units of blood over approximately 1 year. An equal number of nondonors who contributed approximately 7 mL of blood at each visit for iron status measurements only were seen at the same frequency as the donor population. At entrance to the study, iron stores in women and men averaged 724 and 875 mg, respectively. After five donations, mean iron stores dropped to 67 mg in women (n = 27) and 362 mg in men (n = 30); four women (15%) became iron deficient, while two (7%) developed iron deficiency anemia. Three men (10%) developed iron deficiency, but none were found to be anemic. Mean intakes of iron were 23.3 and 22.5 mg per day, respectively, for women and men. Iron intakes were adequate to meet iron requirements of nondonors, but they were not sufficient to halt the steady decrease in iron stores among the donor population, in whom iron absorption increased from approximately 5 percent at entrance to 14 percent at the time of the fifth donation. In summary, healthy elderly persons may contribute to the national blood resource; however, donations should probably be limited to less than five per year or donors should regularly take an iron supplement to preserve reasonable amounts of iron reserves.

Absorption↗
PubMed1991

Characteristics of elderly blood donors.

The aging of our society will result in an increased demand for blood components, but it also has the potential to produce a large group of blood donors, the elderly. To study the effects of regular donation by older persons, a randomized, controlled trial is being conducted among 244 healthy, elderly volunteers. This report focuses on the efficacy of the recruiting efforts for that study and describes the resultant population in terms of their demographics, medical status, and donation safety. Of 325 potential subjects, 18 percent were disqualified and 7 percent refused entry into the study. After medical evaluation, only 2 persons were disqualified for conditions not detected by the usual blood services screening protocols. The resultant elderly donor population (n = 244) was well-educated, middle-income, and, for the most part, married. The group reported more past and present medical conditions, past surgical procedures, and current medications than would be expected in a younger donor group. Reactions to donation were infrequent and mild. With current screening and donation procedures, blood donation by the elderly appears to be safe and practical.

Aged↗
PubMed1990

The 1988 comprehensive blood bank survey of the College of American Pathologists.

An average of 2211 laboratories reported results in this comprehensive blood bank survey. In general, the participant performance remains strong in ABO and D typing, unexpected antibody detection and identification, crossmatching, and antigen identification. However, certain samples achieved less than the usual performance levels. In one sample, anti-C, which was not present, was reported by many participants. In a third sample, only 90% of the participants correctly recorded that no antibody was detectable. Two cross-match challenges did not reach the required participant consensus for grading purposes. The ungraded samples and the supplementary questions provide mock clinical situations and are used to determine current practices and procedures in transfusion medicine. The results of these studies and the participant responses are included.

Blood Banks↗
PubMed1989

The issues in autologous transfusion.

Autologous transfusion should be recognized by patients and physicians as an important measure to provide safer transfusion therapy. This should be suggested to patients in general good health (who are not obviously frail) who have no significant medical problems and no likelihood of severe reaction, who can take iron supplements, and who have at least a 10% chance of using blood during surgery or are having surgery in which the average use is one or more units. Such patients should receive iron supplementation beginning 1 week before the first autologous donation, and should donate one to five units on a weekly basis, but no more frequently than every 72 hours, with their last unit donated 72 hours before surgery. Elderly individuals may donate if the risk of donor reaction seems low. In children and adults, the amount of blood removed should be reduced in proportion to the blood volume if the individual does not meet the standard weight of 50 kg for a 450-mL donation. "Fail-safe" identification systems should be used; these will insure that the correct donor/patient receives the transfusion. Processing of the units is preferred but still optional. Use of these units as homologous units should not be done unless the donor has a hematocrit level acceptable to an autologous donor, meets all the criteria for recipient safety, the unit is processed and negative for all viral markers, and the donor has recently (eg, within 3 years) participated in the volunteer donor program. The unit should be transfused to the patient in situations in which homologous blood would be indicated. Safeguards to prevent volume overload are needed when the unit is stored as whole blood. Future research objectives should include the use of recombinant erythropoietin to prevent donation-induced anemia, delineation of medical conditions which should contraindicate the donation, and determination of the real costs involved in autologous transfusion. Education of the general public, patients, and physicians about the desirability of autologous transfusion should proceed. Third-party carriers also need to be educated about the cost implications and the need to pay for this activity. However, such education should also stress that autologous units will only cover planned, elective surgery and that major blood needs for emergency surgery, trauma, and chronic transfusion will still need to be met by homologous blood from altruistic community blood donors.

Anemia↗
PubMed1988

Posttransfusion purpura associated with alloantibody specific for the platelet antigen, Pen(a).

Posttransfusion purpura (PTP) and severe thrombocytopenia occurred 9 days after transfusion of red blood cells to a 48-year-old, multiparous Navajo woman. The platelet count rose to hemostatic levels after treatment with prednisone and three plasma exchange transfusions. Serologic studies showed that the patient's serum contained the potent antibody reactive with platelets from nearly all normal subjects, but nonreactive with autologous platelets obtained after recovery. This antibody was found to be specific for a high-frequency, platelet-specific antigen, designated Pen(a),implicated previously as an immunogen in neonatal alloimmune thrombocytopenic purpura. An exchange of serum showed that Pena is identical with an alloantigen designated Yuk(b) by Japanese workers. We conclude that PTP can occur in association with alloimmunization against Pen(a) (Yuk(b).

Antibody Specificity↗
PubMed1988

The 1986 Comprehensive Blood Bank Survey of the College of American Pathologists.

In 1986, a total of 2781 laboratories subscribed to the Comprehensive Blood Bank Survey of the College of American Pathologists (CAP) (Skokie, Ill). Performance of these laboratories on the ABO and Rh challenges was good, with 99.7% to 99.9% of the participants reporting the correct response. Antibody identification showed less consistency (45.4% to 97.5%). These challenges consisted of two serum samples with multiple antibodies, one serum sample with antibody to a high-incidence antigen, and one serum sample with anti-M. Performance on the cross match ranged from 95.0% to 99.8% correct, with one exception. This exception was an intended incompatible cross match with the serum containing anti-M, which was reported as incompatible by 56.2% of participants. The antigen-typing challenges ranged from 98.3% to 100% correct, but three typings proved to be a problem. Two samples, when typed for the c antigen, were correctly typed 70.4% of the time and 50.1% of the time. One of these samples, when typed for the E antigen, was correctly typed only 30% of the time. This discrepancy proved to be the result of inadvertent pooling of units of different phenotypes in the sample preparation process.

ABO Blood-Group System↗
PubMed1986

Prevalence of HTLV-III antibody among New Mexico residents with hemophilia.

Persons with hemophilia who have received therapy since 1978 are at risk for the acquired immunodeficiency syndrome. Plasma and serum specimens collected from 1980 to 1985 from 73 New Mexico residents with hemophilia were tested by enzyme immunoassay for antibody to human T-cell lymphotropic virus type III (HTLV-III), and positive results were confirmed by Western blot. Antibody to HTLV-III was first detected in New Mexico residents with hemophilia in 1981. Among 49 persons tested in 1984-1985, seropositivity was found in 35%. Of these, 17 of 32 (53%) commercial concentrate versus 0 of 17 cryoprecipitate users were seropositive (P = .002). Of the 7 with hemophilia B, 3 (43%) were seropositive versus 14 of 42 (33%) with hemophilia A. Of 17 Albuquerque residents with hemophilia, 2(12%) were seropositive as compared with 15 of 32 (47%) persons with hemophilia who resided outside the city (P = .02). Compared with patients with hemophilia outside of Albuquerque, those living in Albuquerque tended to have milder disease and to use cryoprecipitate rather than commercial concentrate. Less frequent treatment (mild disease) and use of cryoprecipitate were associated with a decreased risk of HTLV-III infection.

Acquired Immunodeficiency Syndrome↗
PubMed1986

The 1983 Comprehensive Blood Bank Survey of the College of American Pathologists.

Approximately 2,800 laboratories participated in the 1983 Comprehensive Blood Bank Survey of the College of American Pathologists. Sixteen reference laboratories participated to validate the results and provide a referee consensus for grading of antibody studies. Participant consensus was used to evaluate ABO, Rh, and crossmatching results. Ungraded antigen typing results are included as well as discussions of the ungraded additional challenges and supplementary questions. Accuracy of participant results remains high on these surveys.

Blood Banks↗
PubMed1985

Comparison of the behaviour in vivo of two molecular forms of antithrombin III.

The distribution and rates of catabolism were determined for rabbit antithrombin III (AT) isoforms differing in affinity for heparin-agarose. After isolation from rabbit plasma by heparin-affinity chromatography, the very-high-affinity form, ATvh, was labelled with 131I, and its high-affinity congener, ATh, with 125I. The two forms were separated from free iodine by heparin-affinity chromatography, and then injected simultaneously into young recipient rabbits. The disappearance-of-plasma-AT-radioactivity data were fitted to three exponential equations, and the resulting constants were used to calculate fractional catabolic rates and the various pool sizes for ATh and ATvh. The fractions of plasma ATh and ATvh catabolized daily (j3) were 0.763 +/- 0.023 and 1.88 +/- 0.057 day-1 respectively. Average values of jT, the daily fractional catabolic rates for the total-body ATh and ATvh, were 0.2633 +/- 0.0113 and 0.3832 +/- 0.0211 day-1. The ratios, ATh/ATvh, of the sizes of the plasma, non-circulating vascular-associated and extra-vascular compartments were 0.593, 0.990 and 1.30. By using a previous estimate of a 9:1 ATh/ATvh ratio in rabbit plasma and the calculated compartment sizes, the calculated relative ratio of ATh to ATvh was 5.4:1 in the non-circulating vascular-associated compartment. The data fit a model of antithrombin III distribution and catabolism in which a pool of endothelial-cell heparin-like receptors is seen to mediate the transfer of the inhibitor from plasma to interstitium with catabolism serving as an alternative to this transport.

Animals↗
PubMed1985

In vivo behavior of human radioiodinated antithrombin III: distribution among three physiologic pools.

It has recently been shown that antithrombin III (AT) distributes between plasma, a noncirculating vascular-associated pool and an extravascular pool in rabbit. Study of the in vivo behavior of autologous human 131I-AT demonstrates that in humans AT also distributes among three pools that are analogous to those found in rabbit. From the in vivo kinetic behavior of the 131I-labeled AT, the fractions of total-body AT in the plasma, noncirculating vascular-associated, and extravascular pools were calculated to be 0.393 +/- 0.015, 0.109 +/- 0.016, and 0.496 +/- 0.014, respectively. From three-exponential plasma radioactivity disappearance curves, an average plasma fractional catabolic rate, j3, of 0.576 +/- 0.034 day-1 was obtained for five healthy young men. This is almost identical to the result obtained if plasma 131I-AT disappearance is assumed to fit a two-exponential curve (0.546 +/- 0.038), where the constant C2 from *Ap(t) = C1e-a1t + C2e-a2t is assumed to be equal to 1 - C1. The fraction of the total vascular AT catabolized daily, j3.5, was calculated to be 0.457 +/- 0.034, and the fractional catabolic rate of total-body AT, jT, averaged 0.2271 +/- 0.0176. The results give further support to a model of in vivo behavior in which the vascular AT distributes between plasma and an endothelial receptor. Thus, the latter may serve to mediate activation of AT for its reaction with coagulation proteases and to mediate its entrance into the endothelial cell, where it is either transported to the extravascular fluids or is catabolized.

Antithrombin III↗
PubMed1985

Pneumococcus-induced thrombocytopenia in rabbits.

Thrombocytopenia without other hemostatic changes is the most common coagulopathy associated with sepsis. We studied pneumococcus (PNC)-induced hemostatic changes, including thrombocytopenia, in rabbits. Nonviable PNC or saline solution was injected into rabbits preinfused with chromium 51-labeled platelets or iodine 125-fibrinogen. Blood was serially obtained for determination of platelet counts, 51Cr activity or 125I activity, and fibrinogen and fibrin degradation products. Lung, liver, and spleen tissues were counted for 51Cr or 125I activities per gram of wet tissue. PNC-challenged animals displayed profound thrombocytopenia from 0.5 to 48 hours with the mean nadir (-80% relative to the baseline) at 3 hours and a significantly (P less than 0.025) shortened 51Cr-platelet survival of 1.45 +/- 0.71 days vs. 2.72 +/- 1.09 days for saline-injected controls. Circulating fibrinogen level increased, whereas 125I-fibrinogen survival was unchanged (2.6 +/- 0.5 days in PNC-challenged vs. 2.8 +/- 1.0 days in saline-injected). No increased tissue deposition of either 51Cr-labeled platelets or 125I-fibrinogen was found. Rabbits infused with either serum, plasma, or saline solution after each was incubated with PNC all developed significant thrombocytopenia of less than 1 hour duration with maximal mean decreases relative to the baseline of -76% (P less than 0.001), -65% (P less than 0.0005), and -84% (P less than 0.0005), respectively. Inactivation of serum or plasma complement before PNC incubation or heat treatment after PNC incubation in serum or saline solution did not alter the thrombocytopenia. The thrombocytopenia-promoting activity was also trypsin resistant, did not require the presence of serum, plasma, or PNC capsular polysaccharide for its in vitro generation, and had a mol wt of 100,000 to 300,000. Therefore, PNC-induced thrombocytopenia, in the absence of other hemostatic changes, may be explained on the basis of the direct action of a PNC-derived substance(s) on circulating platelets.

Animals↗