Multifrequency Analysis of Single Inductive Coil Measurements Across a Gel Phantom Simulation of Internal Bleeding in the Brain.

The present study is part of an ongoing effort to develop a simple diagnostic technology for detecting internal bleeding in the brain, which can be used in lieu or in support of medical imaging and thereby reduce the cost of diagnostics in general, and in particular, would make diagnostics accessible to economically disadvantaged populations. The study deals with a single coil inductive device to be used for detecting cerebral hemorrhage. It presents a first-order experimental study that examines the predictions of our recently published theoretical study. The experimental model employs a homogeneous cylindrical phantom in which internal head bleeding was simulated by way of a fluid inclusion. We measured the changes in amplitude and phase across the coil with a network vector analyzer as a function of frequency (100-1,000 MHz), volume of blood simulating fluid, and the site of the fluid injection. We have developed a new mathematical model to statistically analyze the complex data produced in this experiment. We determined that the resolution for the fluid volume increase following fluid injection is strongly dependent on frequency as well as the location of liquid accumulation. The experimental data obtained in this study supports the predictions of our previous theoretical study, and the statistical analysis shows that the simple single coil device is sensitive enough to detect changes due to fluid volume alteration of two milliliters. Bioelectromagnetics. 2020;41:21-33 © 2019 Bioelectromagnetics Society.

Blood volume measurement using cardiovascular magnetic resonance and ferumoxytol: preclinical validation.

BACKGROUND: The hallmark of heart failure is increased blood volume. Quantitative blood volume measures are not conveniently available and are not tested in heart failure management. We assess ferumoxytol, a marketed parenteral iron supplement having a long intravascular half-life, to measure the blood volume with cardiovascular magnetic resonance (CMR). METHODS: Swine were administered 0.7 mg/kg ferumoxytol and blood pool T1 was measured repeatedly for an hour to characterize contrast agent extraction and subsequent effect on Vblood estimates. We compared CMR blood volume with a standard carbon monoxide rebreathing method. We then evaluated three abbreviated acquisition protocols for bias and precision. RESULTS: Mean plasma volume estimated by ferumoxytol was 61.9 ± 4.3 ml/kg. After adjustment for hematocrit the resultant mean blood volume was 88.1 ± 9.4 ml/kg, which agreed with carbon monoxide measures (91.1 ± 18.9 ml/kg). Repeated measurements yielded a coefficient of variation of 6.9%, and Bland-Altman repeatability coefficient of 14%. The blood volume estimates with abbreviated protocols yielded small biases (mean differences between 0.01-0.06 L) and strong correlations (r2 between 0.97-0.99) to the reference values indicating clinical feasibility. CONCLUSIONS: In this swine model, ferumoxytol CMR accurately measures plasma volume, and with correction for hematocrit, blood volume. Abbreviated protocols can be added to diagnostic CMR examination for heart failure within 8 min.

Using Hematology Data from Malaria Vaccine Research Trials in Humans and Rhesus Macaques (Macaca mulatta) To Guide Volume Limits for Blood Withdrawal.

Guidelines on safe volume limits for blood collection from research participants in both humans and laboratory animals vary widely between institutions. The main adverse event that may be encountered in large blood volume withdrawal is iron-deficiency anemia. Monitoring various parameters in a standard blood panel may help to prevent this outcome. To this end, we analyzed the Hgb and MCV values from 43 humans and 46 macaques in malaria vaccine research trials. Although the percentage of blood volume removed was greater for macaques than humans, macaques demonstrated an overall increase of MCV over time, indicating the ability to respond appropriately to frequent volume withdrawals. In contrast, humans showed a consistent declining trend in MCV. These declines in human MCV and Hgb were significant from the beginning to end of the study despite withdrawals that were smaller than recommended volume limits. Limiting the volume withdrawn to no more than 12.5% seemed to be sufficient for macaques, and at 14% or more individual animals tended to fail to respond appropriately to large-volume blood loss, as demonstrated by a decrease in MCV. The overall positive erythropoietic response seen in macaques was likely due to the controlled, iron-fortified diet they received. The lack of erythropoietic response in the human subjects may warrant iron supplementation or reconsideration of current blood volume withdrawal guidelines.

Rescue of cortical neurovascular functions during the hyperacute phase of ischemia by peripheral sensory stimulation.

To investigate the potential therapeutic effects of peripheral sensory stimulation during the hyperacute phase of stroke, the present study utilized electrophysiology and photoacoustic imaging techniques to evaluate neural and vascular responses of the rat cortex following ischemic insult. We employed a rat model of photothrombotic ischemia (PTI), which targeted the forelimb region of the primary somatosensory cortex (S1FL), due to its high reproducibility in creating localized ischemic injury. We also established a hybrid, dual-modality system, including six-channel electrocorticography (ECoG) and functional photoacoustic microscopy (fPAM), termed ECoG-fPAM, to image brain functional responses to peripheral sensory stimulation during the hyperacute phase of PTI. Our results showed that the evoked cerebral blood volume (CBV) and hemoglobin oxygen saturation (SO2) recovered to 84±7.4% and 79±6.2% of the baseline, respectively, when stimulation was delivered within 2.5 h following PTI induction. Moreover, neural activity significantly recovered, with 77±8.6%, 76±5.3% and 89±8.2% recovery for the resting-state inter-hemispheric coherence, alpha-to-delta ratio (ADR) and somatosensory evoked potential (SSEP), respectively. Additionally, we integrated the CBV or SO2 with ADR values as a recovery indicator (RI) to assess functional recovery after PTI. The RI indicated that 80±4.2% of neurovascular function was preserved when stimulation was delivered within 2.5h. Additionally, stimulation treatment within this optimal time window resulted in a minimal infarct volume in the ischemic hemisphere (4.6±2.1%). In contrast, the infarct volume comprised 13.7±1.7% of the ischemic hemisphere when no stimulation treatment was applied.

Ultrafiltration biofeedback guided by blood volume monitoring to reduce intradialytic hypotensive episodes in hemodialysis: study protocol for a randomized controlled trial.

BACKGROUND: Fluid removal during dialysis, also known as ultrafiltration (UF), leads to intradialytic hypotension (IDH) in a significant number of patients treated with hemodialysis (HD) and is associated with an increase in morbidity and mortality. At present, there are no accepted standards of practice for the prevention or treatment of IDH. Relative blood volume monitoring (BVM) is based on the concept that the hematocrit increases with UF, relative to the patient's baseline hematocrit. The use of BVM biofeedback, whereby the HD machine automatically adjusts the rate of UF based on the relative blood volume, has been proposed for the prevention of IDH. METHODS/DESIGN: This is a 22-week randomized crossover trial. Participants undergo a 4-week run-in phase to standardize medications and dialysis prescriptions. Subsequently, participants are randomized to standard HD or to BVM biofeedback for a period of 8 weeks followed by a 2-week washout phase before crossing over. The dialysis prescription remains identical for both arms. The primary outcome is the frequency of symptomatic IDH as defined by an abrupt drop in the systolic blood pressure of ≥ 20 mm Hg accompanied by headache, dizziness, loss of consciousness, thirst, dyspnea, angina, muscle cramps or vomiting. Secondary outcomes include the number of symptomatic IDH episodes and any reduction in IDH episodes, nursing interventions, dialysis adequacy, total body water, extra- and intracellular fluid volumes, brain natriuretic peptide and cardiac troponin levels, blood pressure, antihypertensive medication use, patient symptoms and quality of life. DISCUSSION: Our study will determine the impact of using BVM biofeedback to prevent IDH and other serious adverse events in susceptible patients. TRIAL REGISTRATION: Clinicaltrials.gov NCT01988181 (6 November 2013).

Control de calidad del volumen de hemocomponentes obtenidos mediante equipo fraccionador automatizado COMPOMAT en el Servicio de Hemoterapia y Banco de Sangre del HNDAC - 2011 / Quality control of the volume of blood components obtained by automated fractionator equipment Compomat in Service of Hemotherapy and Blood Bank at the HNDAC - 2011

OBJETIVO: El objetivo del presente Trabajo de Investigación ha sido realizar el Control de Calidad del Volumen de los diferentes hemocomponentes obtenidos mediante el Equipo Fraccionador Automatizado COMPOMAT en el Servicio de Hemoterapia y Banco de Sangre del Hospital Nacional Daniel A. Carrión durante el año 2011, el mismo que se ha desarrollado en forma individualizada, considerando exclusivamente el volumen y en el 100 por ciento de hemocomponentes producidos. MATERIALES Y METODOS: Para la realización del presente Trabajo de Investigación se ha utilizado el Equipo Automatizado COMPOMAT con el programa de fraccionamiento para Bolsas colectoras de sangre cuádruples con anticoagulante SAG Manitol y sistema de tubuladura superior e inferior (TOP and BOTTOM). Al realizar el procedimiento se registró todos los volúmenes de los hemocomponentes fraccionados como son 2140 unidades de paquete globular, 2093 unidades de plasma fresco congelado y 1851 concentrados de plaquetas. El trabajo se desarrolló en el área de fraccionamiento sanguíneo del Servicio de Hemoterapia y Banco de Sangre del Hospital Nacional Daniel A. Carrión de la Región Callao, durante el periodo comprendido desde el mes de Octubre del año 2010 al mes de Marzo del año 2011 en que los datos obtenidos fueron registrados manualmente en un programa Microsoft Excel 2007 para el procesamiento de los mismos y para la realización de Curvas de Control de Calidad de Levey Jennings. RESULTADOS: De los 2140 paquetes globulares procesados, un 77 por ciento cumple con los parámetros de calidad establecidos para volumen. De los 2092 plasmas frescos congelados, el 98 por ciento cumple con los parámetros de calidad establecidos para volumen. De los 1851 concentrados de plaquetas procesadas, el 95 por ciento cumple con los parámetros de calidad establecidos para volumen. CONCLUSIONES: Se concluye que el volumen de los hemocomponentes obtenidos, tanto Paquete Globular, como Plasma Fresco Congelado y Plaquetas, cumple...

[Mechanic reinfusion in emergency surgery].

The article highlights techniques and effects of intraoperative mechanic blood reinfusion in patients with trauma and intraabdominal bleeding in extend, exceeding the self circulating blood volume. The high efficacy of the self blood reinfusion during the emergency operation allowed the 2-fold decrease of the hospital and overall mortality. The mechanic blood reinfusion proved to be a safe and clinically effective method of the globular blood volume deficiency compensation, especially in emergency surgery.

Using time-frequency analysis of the photoplethysmographic waveform to detect the withdrawal of 900 mL of blood.

BACKGROUND: We designed this study to determine if 900 mL of blood withdrawal during spontaneous breathing in healthy volunteers could be detected by examining the time-varying spectral amplitude of the photoplethysmographic (PPG) waveform in the heart rate frequency band and/or in the breathing rate frequency band before significant changes occurred in heart rate or arterial blood pressure. We also identified the best PPG probe site for early detection of blood volume loss by testing ear, finger, and forehead sites. METHODS: Eight subjects had 900 mL of blood withdrawn followed by reinfusion of 900 mL of blood. Physiological monitoring included PPG waveforms from ear, finger, and forehead probe sites, standard electrocardiogram, and standard blood pressure cuff measurements. The time-varying amplitude sequences in the heart rate frequency band and breathing rate frequency band present in the PPG waveform were extracted from high-resolution time-frequency spectra. These amplitudes were used as a parameter for blood loss detection. RESULTS: Heart rate and arterial blood pressure did not significantly change during the protocol. Using time-frequency analysis of the PPG waveform from ear, finger, and forehead probe sites, the amplitude signal extracted at the frequency corresponding to the heart rate significantly decreased when 900 mL of blood was withdrawn, relative to baseline (all P < 0.05); for the ear, the corresponding signal decreased when only 300 mL of blood was withdrawn. The mean percent decrease in the amplitude of the heart rate component at 900 mL blood loss relative to baseline was 45.2% (38.2%), 42.0% (29.2%), and 42.3% (30.5%) for ear, finger, and forehead probe sites, respectively, with the lower 95% confidence limit shown in parentheses. After 900 mL blood reinfusion, the amplitude signal at the heart rate frequency showed a recovery towards baseline. There was a clear separation of amplitude values at the heart rate frequency between baseline and 900 mL blood withdrawal. Specificity and sensitivity were both found to be 87.5% with 95% confidence intervals (47.4%, 99.7%) for ear PPG signals for a chosen threshold value that was optimized to separate the 2 clusters of amplitude values (baseline and blood loss) at the heart rate frequency. Meanwhile, no significant changes in the spectral amplitude in the frequency band corresponding to respiration were found. CONCLUSION: A time-frequency spectral method detected blood loss in spontaneously breathing subjects before the onset of significant changes in heart rate or blood pressure. Spectral amplitudes at the heart rate frequency band were found to significantly decrease during blood loss in spontaneously breathing subjects, whereas those at the breathing rate frequency band did not significantly change. This technique may serve as a valuable tool in intraoperative and trauma settings to detect and monitor hemorrhage.

Relative blood volume based biofeedback during haemodialysis.

Intra-dialytic hypotension is the most frequently occurring complication during haemodialysis and can lead to serious complications. Devices that continuously and non-invasively monitor relative blood volume (RBV) changes during HD are being advocated as a tool to maintain an adequate volume of the intravascular compartment in order to avoid dialysis hypotension. Nowadays, most manufacturers have incorporated a RBV monitor in their dialysis apparatus and two manufacturers have designed biofeedback devices that control intra-dialytic RBV changes. The goal of RBV based biofeedback systems is to prevent a severe or abrupt decrease in blood volume in order to prevent the development of dialysis hypotension. Biofeedback technologies can diminish the severity and/or frequency of dialysis hypotension. At present, however, a completely symptom-free HD is not a reality. The major reasons for this are patient characteristics such as cardiovascular co-morbidity and high UF rates and a lack of understanding of the relation between RBV changes and blood pressure/cardiovascular stability.

Prediction of the effect of acute normovolemic hemodilution on the hematological constituents of sequestered autologous whole blood.

During acute normovolemic hemodilution (ANH), autologous whole blood is collected in a series of collection bags containing anticoagulant. The effect of hemodilution on the actual hematological constituents of this sequestered whole blood product has never been examined. We developed a mathematical model that predicts how whole blood bag constituents change during ANH to elucidate the theoretical basis for ANH efficacy. Formulas were derived to calculate the effect of ANH on [X], the blood constituent of interest. An exponential envelope was defined so that the projected impact of ANH on each constituent could be computed while initial blood volume and whole blood bag volume (WB(ANH)) were manipulated. Equivalency of autologous whole blood hemoglobin, platelets, and fibrinogen were determined by comparison with standard allogeneic blood products. We determined that the concentration of blood constituent X in a particular unit of collected blood ([X](n)) is provided as a fraction of the initial concentration ([X](0)). As WB(ANH) increases relative to estimated blood volume, the decrement in [X](n) increases in successive blood collection bags. Irrespective of initial blood volume, the equivalence of a 450-mL autologous whole blood bag to 1 U of packed red cells and 1 U of whole blood-derived platelet concentrate is 13.3 g/dL and 123 x 10(3)/microL, respectively. The impact of ANH on autologous whole blood constituents may be accurately predicted using this model. Conversion of WB(ANH) into equivalent allogeneic blood products could provide a useful method of comparing outcome in various ANH studies. The exponential envelope may be used to assess the actual ANH technique performed by the anesthesiologist, which in turn may impact quality assurance standards.

[Perioperative transfusion strategy]. / Stratégie transfusionnelle péri-opératoire.

Tactics in blood transfusion have evolved considerably during the last ten years. Awareness of infectious risks and economic considerations have lead legislators to draw the guidelines for a safer transfusion. Their aim is to promote a better transfusion in smaller quantities at a lower risk. The goal of perioperative blood replacement is to maintain hemoglobin, blood volume and coagulation factors at an adequate level. This can be carried out by either homologous or autologous transfusion. Fresh frozen plasma transfusion is only required in severe bleeding where coagulation factors are depleted. The plasma substitutes must be used according to their intrinsic properties and their cost. The choice of an autologous technique depends on the type of surgical procedure, the expected blood loss and the economic resources available. Autologous blood transfusion may be optimized by the association of various techniques. This transfusion strategy must be elaborated by all the medical protagonists implicated in transfusion procedures.

Blood volume changes in normal pregnancy.

The plasma volume and total red cell mass are controlled by different mechanisms and pregnancy provides the most dramatic example of the way in which that can happen. A healthy woman bearing a normal sized fetus, with an average birth weight of about 3.3 kg, will increase her plasma volume by an average of about 1250 ml, a little under 50% of the average non-pregnant volume for white European women of about 2600 ml. There is little increase during the first trimester, followed by a progressive rise to a maximum at about 34-36 weeks, after which little or no further increase occurs. It seems certain that the frequently observed fall in plasma volume in the last six weeks of pregnancy is an artefact of measurement due to poor mixing of tracer when the woman lies supine and obstructs the circulation to her lower limbs. The maximum increase depends largely on the size of the conceptus. It is somewhat increased, perhaps to a mean of 1300 ml, in association with the bigger baby of multiparae and increases still more with twins, triplets and quadruplets. Red cell mass increases by relatively much less, a rise of about 250 ml (some 18% of the non-pregnant volume) in women who take no supplemental iron, and between 400 and 450 ml when iron supplements are taken. The rise is probably linear from the end of the first trimester to term, and there is some evidence of a preliminary fall in red cell mass during the first trimester. As a result of the relatively much greater increase in plasma volume, red cells in the blood are 'diluted' and the venous haematocrit drops from a non-pregnant average of about 40 to about 33 during the last trimester. The differential changes are biologically plausible: red cell mass rises proportionately to the need to carry the extra oxygen taken up in pregnancy; the greater plasma volume increment is needed to cope with the very large increases in blood flow to organs which require little extra oxygen, the skin and the kidneys.

[History of blood circulation]. / Die Geschichte des Kreislaufs.

Until the beginning of the 17th century it was assumed that the arteries carried a subtle kind of air or spirit to the organs, and the veins the nutrient blood. No one seems to have seriously considered that a backflow was necessary. The circulation of the blood was discovered in 1628 by William Harvey. Blood pressure was first measured in animals by Hales (1733). Reliable blood pressure measurements in humans were rendered possible at the beginning of the 20th century through the efforts of Mahomed, von Basch, Potain, Riva-Rocci and Korotkoff. In 1903 electrocardiography was introduced by Einthoven. In 1941 the use of venous catheterization by Cournand initiated the giant forward strides of modern cardiovascular research, diagnosis and therapy.

Cephalic vasomotor feedback in the modification of migraine headache.

The effect of cephalic vasomotor response (CVMR) and frontalis electromyographic (EMG) feedback on control of temporal arterial vasoconstriction and frontalis muscle activity in migraine and muscle contraction headache patients was investigated. A single subject multiple baseline design (across subjects and responses) was introduced to evaluate (1) patterning in the two physiological systems and (2) the effects of CVMR and EMG feedback on headache activity. The data indicated that (a) all four patients demonstrated an ability to control CVMR activity during CVMR feedback and EMG during EMG feedback, (b) idiosyncratic patterns of physiological activity emerge during feedback training, and (c) learned control of the pain mechanism for muscle contraction and migraine headaches was related to reduced frequency and duration of these headaches.