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Keith Allen

Publications and source records attributed to Keith Allen.

6 recordsLinked to original sources
PubMed2006

Autologous platelet gel: an in vitro analysis of platelet-rich plasma using multiple cycles.

Autologous platelet gel (APG) has become an expanding field for perfusionists. By mixing platelet-rich plasma (PRP) with thrombin and calcium, platelet gel is prepared and used in many surgical settings. There are many devices used to produce PRP. This study evaluates the Medtronic Magellan Autologous Platelet Separator. The purpose of this study was to show that processing two cycles of the same syringe could reduce the amount of blood required to produce a specific volume of PRP. Three 60-mL syringes of whole blood with anticoagulant were removed from 15 elective coronary artery bypass patients. Each syringe produced 9 mL of PRP and 1 mL was sent to the laboratory for analysis. The remaining whole blood in each syringe was processed a second time with a yield of 5 mL of PRP with 1 mL sent to the laboratory. With this data, the Magellan was assessed in three phases. The first phase focused on the consistency of the Magellan. Laboratory values of hematocrit, platelet count, white blood cell count, and fibrinogen were compared between each syringe processed by the device. The second phase dealt with the percentage of platelets in the PRP that the Magellan was able to capture. Finally, results of both cycles were combined and compared against baseline values. Most of the hematological factors evaluated between each syringe were consistent in both cycles. The Magellan was able to capture nearly 70% of all platelets in the PRP of the first cycle and 18.5% in the second cycle. By mathematically combining both cycles, platelet counts averaged 2.8 times baseline with a 3.3 times baseline increase when the volume of the two cycles was weighted. This weighted average was done to reflect a higher concentration of Cycle 1 platelets than Cycle 2 in each sample. This study proved that processing each syringe of whole blood twice could reduce blood requirements while maintaining an effective platelet yield and volume. It also showed that the Magellan does conform to benchmark testing done at Medtronic.

Blood Platelets↗
PubMed2004

Sustained-release devices in inner ear medical therapy.

Inner ear medical therapy has been gaining increasing popularity during the last 2 decades. Despite the increased use of this therapy,basic questions regarding this type of treatment have not been answered. The authors have used a variety of sustained-release devices in the laboratory to begin to answer some of these basic questions. This article discusses the results of this work and the application and use of sustained-release devices in patients.

Administration, Topical↗
PubMed2004

Self-monitoring as an intervention to decrease swimmers' stroke counts.

Self-monitoring of stroke count by swimmers is a common coaching strategy, it is but one that has little data to support it. Although research has demonstrated that self-monitoring can motivate behavior change, little research has focused on whether self-monitoring can enhance skill development. The purpose of the present set of studies was to examine the effects of self-monitoring on the improvement of a specific swimming skill (i.e., stroke count). Eight adult fitness swimmers and three college-level competitive swimmers participated in Study 1. In an A-B-A design, swimmers were observed to reduce stroke counts by about one stroke per lap when instructed to self-monitor and to verbally report strokes. In Study 2. swimmers self-monitored and visually reported strokes on a dry-erase board. A greater improvement was observed in five out of six swimmers. Across studies, stroke counts generally returned to baseline levels when self-monitoring was ended, and improvements during both self-monitoring phases were the greatest in the weakest swimmers. Limitations of the research, mechanisms of change, and implications for coaches are discussed.

Adult↗
PubMed2002

The early kinetics of gentamicin uptake into the inner ear.

Transtympanic gentamicin administration has become a popular modality in the treatment of Ménière's disease. This modality and other inner-ear medical therapy are gaining increased clinical and scientific attention. We previously described the kinetics and effects of gentamicin uptake into the inner ear after delivery of the medicine into the middle ear using a variety of different techniques and sustained-release modalities [1]. In our previous work, we reported an early peak perilymph concentration and the presence of intracellular gentamicin at the 4-hour time point. We also demonstrated the activation of inner-ear damage pathways at this early time point. In this report, we examine the kinetics of gentamicin at very early time points, 1 and 2 hours after administration. Healthy adult chinchillas underwent implantation of middle-ear sustained-release devices (one to each ear) containing gentamicin. The animals then were maintained in a neutral position and underwent perilymph gentamicin sampling at the two predetermined time points. This technique allowed us to assess accurately very early time point inner-ear gentamicin kinetics and to compare the activity. The samples then were run for concentration using mass spectrometry. The information gained from this study may increase our scientific understanding about the effects of gentamicin on the inner ear and may allow clinicians to treat patients more effectively for inner-ear disorders.

Animals↗
PubMedDate not supplied

Pharmacologic C5-complement suppression reduces blood loss during on-pump cardiac surgery.

BACKGROUND: Inflammation contributes to morbidity following on-pump cardiac surgery. Complement activation during cardiopulmonary bypass has been associated with the postoperative bleeding and tissue injury. This study examines the pharmacology and impact on blood loss of complement C5 suppression with pexelizumab in patients undergoing cardiac surgery with cardiopulmonary bypass. METHODS: Pexelizumab, a humanized monoclonal antibody single-chain fragment that binds to the human C5 complement component, was studied in a Phase II multicentered clinical trial. CABG (n = 800) and CABG with concomitant valve surgery (n = 114) patients were evaluated. Patients were randomized to either: pexelizumab bolus (2.0 mg/kg) + placebo infusion; pexelizumab bolus (2.0 mg/kg) + pexelizumab infusion (0.05 mg/kg/hour for 24 hours); or placebo bolus + placebo infusion. Pharmacology, chest tube drainage, and transfusion requirements were assessed. RESULTS: Mean maximum pexelizumab serum concentration was similar for bolus and bolus + infusion-treated patients. Complement-dependent serum hemolytic activity was completely suppressed within 1 hour following pexelizumab bolus, however, suppression was maintained for a longer duration in the bolus + infusion compared to the bolus-only treated patients. A reduction in chest tube drainage was observed for all pexelizumab-treated patients, although transfusion of blood products was similar across all study groups. CONCLUSION: Pexelizumab administration inhibits complement-dependent hemolytic activity and is associated with a reduction in postoperative chest tube drainage in patients undergoing cardiac surgery requiring cardiopulmonary bypass. Further, clinical studies are needed to assess the value of complement attenuation in this setting.

Aged↗