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Biomedical subjects

R H Walker

Publications and source records attributed to R H Walker.

At least 55 records · Page 3Linked to original sources
PubMed1992

Reducing neonatal transfusions.

In an attempt to prevent blood transfusions from being ordered unnecessarily in our neonatal intensive care unit (NICU), we developed transfusion guidelines and prospectively evaluated their impact on our transfusion practices. Initially, 17% of our packed red blood cell transfusions (PRBCT) did not meet our guidelines. However, 6 months following development of the guidelines, this decreased to 9%, and 12 months later, it decreased to 1%. Although the guidelines are clearly arbitrary, they do provide for consistency within our NICU and a method of evaluating our own use of PRBCT.

Apnea↗
PubMed1992

Pilot surveys for proficiency testing of semen analysis. Comparison of dry-ice vs liquid nitrogen shipments.

Two pilot surveys involving routine semen analysis were provided to eight and nine selected laboratories. The laboratories were selected for expertise and geographic diversity. Manual and computer-assisted semen analysis were performed by the participating laboratories on pooled cryopreserved human semen samples following shipment either on dry-ice pellets or in liquid nitrogen (dry shippers). Coefficient of variation values obtained were 13% to 39% for concentration, 19% to 127% for motility, and 42% to 90% for viability. Motility was impaired for sperm shipped on dry ice. However, variances and performance criteria can be established for all analyses. A semen analysis survey is feasible but expensive owing to the shipping costs of cryopreserved semen.

Cell Survival↗
PubMed1992

Dissociation of modular hip arthroplasty components after dislocation. A report of three cases at differing dissociation levels.

Modular hip arthroplasty systems, currently widely employed, offer the advantage of increased intraoperative flexibility in component selection with reduced inventory, as well as the disadvantage of modular component dissociation. Dissociation during closed reduction for dislocation is reported in three patients at three different interface levels: (1) fixed acetabular shell-polyethylene linear interface, (2) bipolar acetabular component-femoral head interface, and (3) femoral head-neck interface. Subsequent open reduction was required in each case. Although this potential disadvantage of modular hip systems does not outweigh the benefits, it does warrant that certain precautions be taken when implanting modular components. The acetabular linear should lie flush within the metallic shell after impaction. The femoral head should be firmly impacted onto the neck. Both should resist reasonable manual force of disassembly. Should a modular hip arthroplasty component dislocate, gentle reduction under general anesthesia and fluoroscopic control is warranted. Careful inspection of pre- and postreduction roentgenograms for signs of modular component dissociation is mandatory.

Adult↗
PubMed1991

Postoperative use of continuous passive motion, transcutaneous electrical nerve stimulation, and continuous cooling pad following total knee arthroplasty.

Three rehabilitation modalities relating to in-hospital postoperative care following unilateral total knee arthroplasty (UTKA) were studied regarding their effect on pain management and UTKA outcome: (1) continuous passive motion (CPM); (2) CPM with transcutaneous electrical nerve stimulation (TENS); and (3) CPM with continuous cooling pad (CCP). Phase I: CPM. Twenty-two UTKA patients were randomized into two postoperative care groups: (1) 12 with CPM; and (2) 10 with no CPM. Total hospitalization pain medication consumption was significantly less for the CPM group (P less than .05). Phase II: CPM With TENS. Forty-eight UTKA patients were randomized into three postoperative care groups: (1) 18 with an ipsilateral thigh TENS unit delivering sensory threshold stimulation; (2) 18 with a subthreshold TENS unit; and (3) 12 with no TENS unit. All groups used CPM. No significant difference was found regarding pain medication consumption. Phase III: CPM With CCP. Thirty consecutive UTKA patients were divided into two postoperative care groups: (1) 15 with a CCP unit; and (2) 15 with no CCP unit. Both groups used CPM. No significant difference was found regarding total or intramuscular hospitalization pain medication consumption. However, oral hospitalization pain medication consumption was significantly less for the CCP group (P less than .01). This postoperative UTKA study demonstrates significantly decreased total in-hospital pain medication consumption when comparing CPM vs no CPM, significantly decreased oral in-hospital pain medication consumption when comparing CPM with CCP vs CPM without CCP, but no difference when comparing CPM with TENS vs CPM without TENS.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Steroid-related osteonecrosis of the knee. Two case reports and a literature review.

Steroid-related osteonecrosis of the knee has been only rarely reported, especially without concomitant hip involvement. Two such cases are documented with correlated roentgenographic and magnetic resonance imaging. A comprehensive review of the literature illustrates the diverse circumstances in which this rare condition may occur.

Adult↗
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

Electrophysiological and anatomical observations concerning the pallidostriatal pathway in the rat.

Anatomical studies in several species have demonstrated a pallidostriatal pathway. We employed electrophysiological and anatomical methods to distinguish the neurones of this pathway from the two pallidocortical groups reported in the rat. Injection of fluorescent retrograde tracers, combined with immunohistochemistry for choline acetyltransferase, provided anatomical evidence of the distinction between neurones of the cholinergic pallidocortical projection and pallidal cells retrogradely labelled from the striatum. Extracellular recordings made in the globus pallidus of halothane-anaesthetised rats provided an electrophysiological description of the pallidostriatal pathway. In some animals neurones of this pathway were distinguished from pallidocortical neurones as a stimulating electrode, situated in the crus cerebri, permitted identification of neurones which projected through this region as well as to the striatum. Neither pallidocortical pathway is reported to have descending axons travelling in the crus cerebri at this point. A preliminary electrophysiological study was carried out in rats in which the dopamine-containing cells of substantia nigra had been destroyed by injections of 6-hydroxydopamine at least 6 months prior to the recording. In the globus pallidus on the lesioned side the mean firing rate of neurones was increased compared with controls. No specific change in firing pattern was noted but the neurones were more responsive to striatal stimulation suggesting that long-term dopamine denervation alters the sensitivity of neurones of globus pallidus.

Action Potentials↗
PubMed1989

Paternity testing with an absent mother. The probability of exclusion of red cell surface antigen, Gm, Hp, and HLA systems in North American whites and blacks.

Blood tests in cases of disputed paternity can be extremely useful even when the mother's blood sample is not available. The mean probability of exclusion (A) of red cell surface antigen, Gm, Hp, and HLA systems was determined in this situation for North American whites and blacks by creating pairs of a man and an unrelated child. In whites, the most valuable of the systems investigated to indicate nonpaternity for false fathers were HLA, Rh, Fy, and MNSs, in that order. HLA, MNSs, and Gm were the most valuable systems in blacks. With all of the genetic systems used in this study, the combined probability of exclusion (CPE) of men falsely accused of paternity, in cases where the mother is absent, is approximately 95 percent for whites and 92 percent for blacks. Since only indirect exclusions are possible without the mother, the common test panel of HLA and red cell antigens may not always allow an adequate study. Extended testing is recommended to include additional genetic systems in order to achieve an average combined probability of exclusion of at least 95 percent.

Black People↗
PubMed1989

DNA probe technology in parentage testing.

Paternity tests involve laboratory procedures on blood samples obtained from the alleged father, mother, and child to determine if the alleged father is the true father. Conclusions are based on the principle that the child inherits half of the characteristics (markers) in his/her blood from each true parent. DNA probe analysis has emerged from the research laboratory and is currently being utilized by laboratories engaged in parentage testing to improve their efficiency in discriminating between fathers and nonfathers. This new technique provides a very powerful tool.

Journal Article↗
PubMed1989

Alloimmunization following blood transfusion.

Although it has been 20 years since Rh immunoglobulin (Rhlg) was widely introduced in the United States, anti-D still remains as a frequent alloantibody found in hospital patients. Currently, anti-D is second in frequency only to anti-K as an alloantibody of clinical significance. Estimation of alloantibody frequencies in hospital patients reveals a gradual decline in the frequencies of anti-D and anti-CD, whereas anti-K, anti-E and anti-Jka show increases in relative and absolute frequencies. This phenomenon probably reflects the optimum use of Rhlg and more aggressive transfusion treatment of patients as indicated by the red cell use factor: (Red cell transfusions -- autologous transfusions)/admissions. Such a practice may be the result of the increasing severity of illness observed in patients admitted to hospitals. Alloimmunization due to donor white blood cells, platelets, and serum proteins also frequently follows the transfusion of homologous blood. These problems, which may pose additional risks to the transfusion recipient, are reviewed.

Blood Group Antigens↗
PubMed1988

Laboratory determination of parentage.

By incorporating basic genetic concepts and assumptions, laboratories can determine if a man is excluded from paternity or, if not excluded, determine the likelihood of paternity. The concepts of exclusion and determination of likelihood of paternity are presented.

Accreditation↗
PubMed1987

Special report: transfusion risks.

The benefits of blood transfusion must be considered and evaluated in terms of risk factors relating to the adverse effects of transfusion. Transfusions may result in either serious or troublesome complications. Although the risk of transfusion-associated acquired immune deficiency syndrome (AIDS) is of paramount concern in the patient population, it has been virtually eliminated because of testing of donor units for antibody to human immunodeficiency virus. Serious and troublesome adverse effects of blood transfusion are listed and ranked in order of approximate frequency. About 20% of all transfusions result in some type of adverse effect. The major serious risk of blood transfusion today continues to be transfusion-associated viral hepatitis. This entity is usually subclinical but frequently results in serious chronic liver disease. Transfusions should be avoided unless patient care would be compromised if withheld.

Acquired Immunodeficiency Syndrome↗
PubMed1987

CAP comprehensive blood bank survey--1985.

Approximately 2800 laboratories participate in the voluntary Comprehensive Blood Bank Survey of the College of American Pathologists, including graded challenges relating to ABO and Rh typing, antibody detection and identification, and crossmatching. The Surveys have shown consistently good performance in these areas. Ungraded responses reporting results of antigen typing, other cell or serum challenges selected for educational value, and supplemental questions are reviewed. The supplemental questions are designed to elicit practice patterns and to present opportunities for educational comments in the critiques.

Antibodies↗
PubMed1987

CAP Comprehensive Blood Bank Survey--1984.

An average of 2750 laboratories participated in the 1984 Comprehensive Blood Bank Survey of the College of American Pathologists. Results from 16 laboratories were utilized to validate results and assure maintenance of specimen character during shipment. Results of ABO grouping, D typing, special antigen typing, antibody detection, and antibody identification by participants remained good and are discussed. Special ungraded samples were provided as additional challenges. The results of these studies and the responses to supplementary questions are discussed.

ABO Blood-Group System↗
PubMed1987

Progress report on the ASHI/CAP Histocompatibility Survey Program, 1981-1986.

Two histocompatibility testing surveys were conducted over a five-year period by the American Society for Histocompatibility and Immunogenetics and the College of American Pathologists. More than 200 laboratories participated in the HS survey, which consisted of four shipments of cells and serum samples to be tested for ABO type, HLA-A and -B types, antibody identification, and lymphocytotoxicity crossmatching. About 100 laboratories participated in the DR survey, which consisted of four annual shipments to be tested for HLA-DR and -DQ types, antibody identification, and crossmatching. The results of the analysis of the HLA-typing results showed high consistency (generally greater than 90%) among laboratories in the definition of most recognized HLA antigens. In contrast, the HLA antibody screening was generally less consistent between laboratories. On the basis of 90% or greater consensus among participants, it was possible to develop a performance grading system.

ABO Blood-Group System↗
PubMed1986

Autologous blood transfusion in total joint arthroplasty.

In 1974, an autologous blood transfusion program for total joint replacements was established at William Beaumont Hospital. From 1980 through 1984, 396 patients donated 1,619 units of blood. The patients' ages ranged from 23 to 89 years (median, 63 years) in men and 29 to 89 years (median, 67 years) in women. Blood was collected on a weekly basis, if the patient's hematocrit was greater than 34%. Blood collected within 49 days of surgery was maintained in a liquid state; otherwise, it was frozen. Patients with a history of cardiovascular disease received permission from their internist before donating blood. The cost per unit of frozen blood was much higher than that of liquid blood. Autologous blood transfusion is safe, there is no age limitation for blood donors, and blood can be collected at weekly intervals.

Adult↗