The act of measurement bridges the quantum and classical worlds by projecting a superposition of possible states into a single (probabilistic) outcome. The timescale of this 'instantaneous' process ...can be stretched using weak measurements, such that it takes the form of a gradual random walk towards a final state. Remarkably, the interim measurement record is sufficient to continuously track and steer the quantum state using feedback. Here we implement quantum feedback control in a solid-state system, namely a superconducting quantum bit (qubit) coupled to a microwave cavity. A weak measurement of the qubit is implemented by probing the cavity with microwave photons, maintaining its average occupation at less than one photon. These photons are then directed to a high-bandwidth, quantum-noise-limited amplifier, which allows real-time monitoring of the state of the cavity (and, hence, that of the qubit) with high fidelity. We demonstrate quantum feedback control by inhibiting the decay of Rabi oscillations, allowing them to persist indefinitely. Such an ability permits the active suppression of decoherence and enables a method of quantum error correction based on weak continuous measurements. Other applications include quantum state stabilization, entanglement generation using measurement, state purification and adaptive measurements.
A variety of patientand product-related factors influenced the outcome of 6379 transfusions given to 533 patients in the Trial to Reduce Alloimmunization to Platelets (TRAP). Responses measured were ...platelet increments, interval between platelet transfusions, and platelet refractoriness. Patient factors that improved platelet responses were splenectomy and increasing patient age. In contrast, at least 2 prior pregnancies, male gender, splenomegaly, bleeding, fever, infection, disseminated intravascular coagulation, increasing height and weight, lymphocytotoxic antibody positivity, an increasing number of platelet transfusions, or receiving heparin or amphotericin were associated with decreased posttransfusion platelet responses. Platelet factors that were associated with improved platelet responses were giving ABO-compatible platelets, platelets stored for 48 hours or less, and giving large doses of platelets while ultraviolet B (UV-B) or gamma irradiation decreased platelet responses. However, in alloimmunized lymphocytoxic antibody-positive patients, the immediate increment to UV-B-irradiated platelets was well maintained, whereas all other products showed substantial reductions. Refractoriness to platelet transfusions developed in 27% of the patients. Platelet refractoriness was associated with lymphocytotoxic antibody positivity, heparin administration, fever, bleeding, increasing number of platelet transfusions, increasing weight, at least 2 pregnancies, and male gender. The only factors that reduced platelet refractoriness rates were increasing the dose of platelets transfused or transfusing filtered apheresis platelets.
We observe the quantum Zeno effect-where the act of measurement slows the rate of quantum state transitions-in a superconducting qubit using linear circuit quantum electrodynamics readout and a ...near-quantum-limited following amplifier. Under simultaneous strong measurement and qubit drive, the qubit undergoes a series of quantum jumps between states. These jumps are visible in the experimental measurement record and are analyzed using maximum likelihood estimation to determine qubit transition rates. The observed rates agree with both analytical predictions and numerical simulations. The analysis methods are suitable for processing general noisy random telegraph signals.
Background and Objectives
Platelet alloimmunization and refractoriness to platelet transfusion are complications of platelet transfusion therapy. The platelet dose (PLADO) trial, as the largest ...prospective randomized trial of prophylactic platelet therapy to date, afforded an opportunity to analyse these two issues.
Materials and Methods
PLADO patient records were examined for evidence of platelet alloimmunization, defined as an increase in HLA Class I panel‐reactive antibodies (PRA) to ≥20%, and clinical refractoriness, defined as two consecutive ≤4 h posttransfusion corrected platelet count increments (CCI) of <5000. Multivariate logistic regression, restricted to platelet‐transfused subjects who received exclusively either in‐process leucoreduction apheresis or whole blood‐derived (WBD) leucocyte‐reduced platelets, compared the frequency of these outcomes by platelet unit and patient characteristics.
Results
Forty of 816 evaluable platelet‐transfused patients (5%) became alloimmunized during the trial. Prior pregnancy, chemotherapy only compared to progenitor cell transplant, and low platelet dose – all were associated with significantly higher rates of alloimmunization. Among 35 alloimmunized patients evaluated for refractoriness, 8 (23%) had two consecutive CCI < 5000/μl. Regardless of alloimmunization status, CCIs < 5000/μl were observed following 17% of platelet transfusions. Among 734 patients receiving at least two platelet transfusions, two consecutive CCIs of ≤5000 occurred in 102 (14%).
Conclusions
The incidence of new platelet alloimmunization was low in the PLADO study, but follow‐up was at most 30 days. Alloimmunization was present in only 8 of 102 (8%) of observed cases of refractoriness, suggesting that other causes of poor posttransfusion increments are frequent.
We report a transfusion trial of platelets photochemically treated for pathogen inactivation using the synthetic psoralen amotosalen HCl. Patients with thrombocytopenia were randomly assigned to ...receive either photochemically treated (PCT) or conventional (control) platelets for up to 28 days. The primary end point was the proportion of patients with World Health Organization (WHO) grade 2 bleeding during the period of platelet support. A total of 645 patients (318 PCT and 327 control) were evaluated. The primary end point, the incidence of grade 2 bleeding (58.5% PCT versus 57.5% control), and the secondary end point, the incidence of grade 3 or 4 bleeding (4.1% PCT versus 6.1% control), were equivalent between the 2 groups (P= .001 by noninferiority). The mean 1-hour posttransfusion platelet corrected count increment (CCI) (11.1 × 103PCT versus 16.0 × 103control), average number of days to next platelet transfusion (1.9 PCT versus 2.4 control), and number of platelet transfusions (8.4 PCT versus 6.2 control) were different (P< .001). Transfusion reactions were fewer following PCT platelets (3.0% PCT versus 4.4% control;P= .02). The incidence of grade 2 bleeding was equivalent for PCT and conventional platelets, although posttransfusion platelet count increments and days to next transfusion were decreased for PCT compared with conventional platelets.
Platelets are lost from circulation by 2 mechanisms: senescence and random loss. Approximately 7.1 × 10
3 platelets/μL/d are postulated to be randomly used in maintaining vascular integrity. Thus, in ...clinically stable patients, major bleeding is unusual unless the platelet count is ≤5 × 10
3/μL. Risk factors for bleeding at higher platelet counts are disseminated intravascular coagulation with contributory clotting factor deficiencies, structural lesions with loss of vascular integrity, and refractoriness to platelet transfusions. Several large studies have documented the safety of lowering the prophylactic platelet transfusion trigger from the previously used 20 × 10
3/μL to 10 × 10
3/μL. A few studies have even suggested that a 5 × 10
3/μL trigger is acceptable. Based on these results, the next step of giving just therapeutic platelet transfusions is being evaluated. In a large retrospective study, the most significant predictor of bleeding was not the patient’s platelet count but a history of bleeding in the prior 5 days. These data suggest that attention should be focused on providing aggressive platelet therapy for active bleeding rather than transfusing platelets prophylactically. Therapeutic platelet transfusions have been documented to control bleeding, and mortality rates are not increased when comparing patients receiving therapeutic to that seen in patients receiving prophylactic platelet transfusions.
We performed a prospective, randomized trial in CMV seronegative marrow recipients to determine if filtered blood products were as effective as CMV-seronegative blood products for the prevention of ...transfusion-transmitted CMV infection after marrow transplant. Before transplant, 502 patients were randomized to receive either filtered or seronegative blood products. Patients were monitored for the development of CMV infection and tissue-documented CMV disease between days 21 and 100 after transplant. Infections occurring after day 21 from transplant were considered related to the transfusion of study blood products and, thus, were considered evaluable infections for the purpose of this trial. In the primary analysis of evaluable infections, there were no significant differences between the probability of CMV infection (1.3% v2.4%, P = 1.00) or disease (0% v 2.4%, P = 1.00) between the seronegative and filtered arms, respectively, or probability of survival (P - .6). In a secondary analysis of all infections occurring from day 0 to 100 post-transplant, although the infection rates were similar, the probability of CMV disease in the filtered arm was greater (2.4% v 0% in the seronegative arm, P = .03). However, the disease rate was still within the prestudy clinically defined acceptable rate of ≤5%. We conclude that filtration is an effective alternative to the use of seronegative blood products for prevention of transfusion-associated CMV infection in marrow transplant patients.
Background and Objectives
The purpose of our studies was to determine the effects of extended platelet storage on poststorage platelet viability.
Materials and Methods
Normal subjects were recruited ...to donate platelets using two different apheresis systems: either the COBE Spectra (n = 58) or the Haemonetics MCS+ (n = 84). Platelet recovery and survival data from the two systems were compared with each other and with in vitro measurements of the stored platelets.
Results
There were no significant differences in either platelet recoveries or survivals between the two machines between 1 and 8 days of storage. Combining the data from both machines, platelet recoveries decreased by 2·6% and survivals by 0·3 days/storage day. In vitro assays did not predict either platelet recoveries or survivals during storage for 5–8 days. After 9 days of storage, pHs were unacceptable (≤ 6·1), suggesting that 8 days will be the longest possible storage time.
Conclusions
These data suggest that, if stored platelet bacterial contamination issues are resolved, significant extension of platelet storage times is possible.
BACKGROUND: A photochemical treatment (PCT) method utilizing a novel psoralen, amotosalen HCl, with ultraviolet A illumination has been developed to inactivate viruses, bacteria, protozoa, and white ...blood cells in platelet (PLT) concentrates. A randomized, controlled, double‐blind, Phase III trial (SPRINT) evaluated hemostatic efficacy and safety of PCT apheresis PLTs compared to untreated conventional (control) apheresis PLTs in 645 thrombocytopenic oncology patients requiring PLT transfusion support. Hemostatic equivalency was demonstrated. The proportion of patients with Grade 2 bleeding was not inferior for PCT PLTs.
STUDY DESIGN AND METHODS: To further assess the safety of PCT PLTs, the adverse event (AE) profile of PCT PLTs transfused in the SPRINT trial is reported. Safety assessments included transfusion reactions, AEs, and deaths in patients treated with PCT or control PLTs in the SPRINT trial.
RESULTS: A total of 4719 study PLT transfusions were given (2678 PCT and 2041 control). Transfusion reactions were significantly fewer following transfusion of PCT than control PLTs (3.0% vs. 4.1%; p = 0.02). Overall AEs (99.7% PCT vs. 98.2% control), Grade 3 or 4 AEs (79% PCT vs. 79% control), thrombotic AEs (3.8% PCT vs. 3.7% control), and deaths (3.5% PCT vs. 5.2% control) were comparable between treatment groups. Minor hemorrhagic AEs (petechiae 39% PCT vs. 29% control; p < 0.01 and fecal occult blood 33% PCT vs. 25% control; p = 0.03) and skin rashes (56% PCT vs. 42% control; p < 0.001) were significantly more frequent in the PCT group.
CONCLUSION: The overall safety profile of PCT PLTs was comparable to untreated PLTs.
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