Require Blood Sampling Research Articles

Chronic Hemodialysis: Kt/V or Solute Removal Index to Evaluate the Effective Delivered Dose?

A standard for quantifying the hemodialysis dose has not yet been defined. Many authors suggest the use of an alternative method to Kt/V: the solute removal index (SRI). We compared three methods based on blood-side urea determinations with the direct quantification method (DDQ) for estimating the delivered dialysis dose, expressed as SRI as well as Kt/V. Eight patients underwent three consecutive dialysis sessions, with the same dialytic efficiency. For each patient and each dialytic session the SRI and Kt/V were determined using the DDQ method and the single pool variable volume kinetic model, in its classical version (SPVV) as well by using the postdialysis urea value determined 30 min after the end of the session (eqSPVV). Double pool Kt/V was also estimated by the Daugirdas-Schneditz rate equation. Our results showed that the SPVV kinetic model significantly overestimated the delivered dialysis dose, the mean value of SRI and Kt/V were respectively 8.9% and 17% higher than those obtained by DDQ. The eqSPVV allowed the SRI to be estimated with a difference of -0.3% and Kt/V with a difference of -2% in comparison with DDQ. By using the Daugirdas-Schneditz rate of equation, which does not require blood samples to be drawn after the end of the session, the difference in Kt/V value was 3%. Therefore, both the eqSPVV kinetic model and the Daugirdas method allow quantification of the delivered dialysis dose with results similar to those determined by DDQ, which cannot be routinely applied. Kt/V seems the best marker for dialytic doses quantification.

Design, construction and six years' experience of an integrated system for automated handling of discrete blood samples.

The present paper describes the design of an integrated system to aid in the taking and measurement of manual blood samples during nuclear medical examinations requiring blood sampling. In contrast to previously published systems, the present system is not used in the actual sampling of the blood, but aims to aid in all other aspects of handling and measurement. It consists of two main parts. One part is a distributed software system running on the scanner host computer used to register sample times, to display information pertaining to the ongoing examination and to collect data from a number of well crystals. The other main part consists of an industrial robot used to perform the actual weighing, centrifugation, pipetting and measurement of the samples. The system has been operational for 6 years, during which time it has had an "up-time" in excess of 95% and has handled and measured the blood samples from more than 5000 examinations, each comprising an average of 15 blood samples. The throughput of the system is 50 whole blood samples or 21 plasma samples per hour. In addition it has to a large extent removed the "human factor" from the process, thereby increasing the reliability of the data.

In vitro assessment of platelet function.

With the realization that the skin bleeding time is often an unreliable measure of platelet function, efforts have been made to identify ways to assess qualitative platelet dysfunction. Currently available techniques measure platelet adhesion, platelet aggregation, the ability of platelets to retard or stop flow through fibers, and the contribution of platelets to in vitro clot formation. Glass bead adhesion, which continues to be performed in some laboratories, is gradually being replaced by measures of platelet adhesion to filters composed of glass fibers, Dacron fibers, or collagen. In each instance, anticoagulated platelet-rich plasma or whole blood flows through the filter under a regulated pressure gradient. The amount of blood flowing through the filter versus time and/or the time to filter occlusion are measured. Recent developments in platelet aggregation have focused on whole blood and stagnation point flow aggregation techniques. Whole blood aggregation does not require blood sample processing and accommodates blood obtained from citrated vacutainer tubes. Stagnation point flow measures both platelet adhesion and aggregation and may be able to detect pathologically-enhanced platelet function. Global measures of hemostasis attempt to simultaneously evaluate the adequacy of fluid phase coagulation and platelet function. Currently available techniques include Thromboelastography, SonoClot Analyzer, Hemodyne Hemostasis Analyzer, PITT, and Hemostatometry. Although each of these technologies have been shown to provide interesting data in the research setting, the ability of any of these techniques to detect abnormal or clinical inadequate platelet function remains to be established.

Optimization of sodium removal in paired filtration dialysis by single pool sodium and conductivity kinetic models.

Sodium removal is one of the main factors affecting intradialytic cardiovascular stability and interdialytic hypertension, and its removal should therefore be individualized. The aims of this study were: (1) to test the ability of a single-pool variable volume (SPVV) sodium kinetic model (NaKM) to optimize sodium removal in paired filtration dialysis (PFD), and (2) to test a SPVV conductivity kinetic model (CKM) in order to verify whether CKM can be used as an alternative for NaKM in estimating sodium balance. The mean difference between the NaKM-predicted and measured end-PFD plasma water ionized sodium concentrations was 0.00 +/- 0.55 mEq/l, which means that the model has an imprecision of < or = 1.1 mEq/ l. The mean difference between predicted and measured sodium removal was 0.21 +/- 16.86 mEq/session, which means a model overestimate of 0.21 mEq/session. The mean difference between the CKM-predicted and measured end-PFD ultrafiltrate conductivity was 0.01 +/- 0.05 mS/cm, which means an inaccuracy of the model of 0.01 mS/cm and an imprecision of < or = 0.1 mS/cm. The regression in the ionized sodium concentration measured in plasma or blood on the conductive values of the ultrafiltrate shows an error of < or = 2 mEq/l in the prediction of the ionized sodium concentration in blood by means of ultrafiltrate conductivity measurements. These results demonstrate that both models make it possible to obtain a level of dialytic sodium removal that is almost equivalent to interdialytic sodium loading. Moreover, given that it does not require blood sampling and the possibility of making repeated and inexpensive ultrafiltrate conductivity measurements, the CKM allows online monitoring of programmed sodium removal.

Effects of Rest and Exercise on Cardiac Blood Volume Determinations

The purpose of this study was to investigate the changes in blood activity during rest, exercise and recovery, and to assess its influence on left ventricular (LV) volume determination using the count-based method requiring blood sampling. Forty-four patients underwent rest-stress radionuclide ventriculography; Tc-99m-human serum albumin was used in 13 patients (Group I), red blood cells was labeled using Tc-99m in 17 patients (Group II) in vivo, and in 14 patients (Group Ill) by modified in vivo/in vitro method. LV volumes were determined by a count-based method using corrected count rate in blood samples obtained during rest, peak exercise and after recovery. In group I at stress, the blood activity decreased by 12.6 +/- 5.4%, p < 0.05, as compared to the rest level, and increased by 25.1 +/- 6.4%, p <0.001, and 12.8 +/- 4.5%, p < 0.05, above the resting level in group II and III, respectively. This had profound effects on LV volume determinations if only one rest blood aliquot was used: during exercise, the LV volumes significantly decreased by 22.1 +/- 9.6%, p < 0.05, in group I, whereas in groups II and III it was significantly overestimated by 32.1 +/- 10.3%, p < 0.001, and 10.7 +/- 6.4%, p < 0.05, respectively. The changes in blood activity between stress and recovery were not significantly different for any of the groups. The use of only a single blood sample as volume aliquot at rest in rest-stress studies leads to erroneous estimation of cardiac volumes due to significant changes in blood radioactivity during exercise and recovery.

Distribution volume ratios without blood sampling from graphical analysis of PET data.

The distribution volume ratio (DVR), which is a linear function of receptor availability, is widely used as a model parameter in imaging studies. The DVR corresponds to the ratio of the DV of a receptor-containing region to a nonreceptor region and generally requires the measurement of an arterial input function. Here we propose a graphical method for determining the DVR that does not require blood sampling. This method uses data from a nonreceptor region with an average tissue-to-plasma efflux constant k2 to approximate the plasma integral. Data from positron emission tomography studies with [11C]raclopride (n = 20) and [11C]d-threo-methylphenidate ([11C]dMP) (n = 8) in which plasma data were taken and used to compare results from two graphical methods, one that uses plasma data and one that does not. k2 was 0.163 and 0.051 min-1 for [11C]raclopride and [11C]dMP, respectively. Results from both methods were very similar, and the average percentage difference between the methods was -0.11% for [11C]raclopride and 0.46% for [11C]dMP for DVR of basal ganglia (BG) to cerebellum (CB). Good agreement between the two methods was also achieved for DVR images created by both methods. This technique provides an alternative method of analysis not requiring blood sampling that gives equivalent results for the two ligands studied. It requires initial studies with blood sampling to determine the average kinetic constant and to test applicability. In some cases, it may be possible to neglect the k2 term if the BG/CB ratio becomes reasonably constant for a sufficiently long period of time over the course of the experiment.

Telephone Reporting of Blood Analysis Results into the Operating Room

Telephone Reporting of Blood Analysis Results into the Operating Room

Inflammatory markers in childhood asthma.

The importance of airway inflammation in the pathogenesis of asthma is clearly established. Studies in adults as well as in children have led to the concept that asthma is a chronic inflammatory disease. Airway inflammation is found even in mild asthma. Bronchoconstriction and hyper-reactivity appear to be secondary to the release of inflammatory mediators. The changed view of the pathogenesis of asthma and current emphasis on anti-inflammatory treatment have raised a need for markers that reflect the inflammatory status in the airways. This is of special importance in paediatric practice because lung function tests are less easily performed in young children, and it is preferable to keep steroid doses as low as possible. The eosinophil granulocyte has a multitude of proinflammatory functions and plays a key role in the asthmatic inflammation. It secretes toxic proteins and produces cytokines, which have important roles in airway inflammation. Use of eosinophil granula proteins to monitor inflammation is now finding its place. Measurement of eosinophil cationic protein (ECP) seems to be a valuable complement to the recording of lung function. For paediatric use, measurement of urinary eosinophil protein X (EPX) is promising because it does not require blood sampling.

924-117 Cardiac Injury in the Critically III: A Surprisingly Common Finding

Medical intensive care unit (MICU) patients often are subjected to severe cardiovascular stress and thus may be at risk for myocardial ischemia/infarction. To determine the incidence of myocardial injury in such patients, we measured daily levels of cardiac troponin I (cTnl), a long-lived, sensitive and highly specific plasma marker of cardiac injury. Two hundred twenty-seven consecutive patients (242 admissions) were considered for the study; 18 were excluded due to either suspected infarction on admission or inability to obtain the required blood samples. The MICU staff evaluated 121 of the 209 patients (58%) for possible infarction; they were unaware of the cTnl results. Overall, 32 of the 209 patients (15%) had evidence of myocardial damage based on a cTnl value ≥ 3.1 ng/ml. Evidence of myocardial injury by cTnl was present on admission or day 1 in 29 of the 32 patients. Only 37.5% (12/32) of these patients were diagnosed as having acute infarction by the MICU staff. An additional 9 patients had elevated values of MBCK but were not thought to have suffered cardiac damage. Five of these patients met criteria for infarction with cTnl while 4 did not. Myocardial injury occurred in 21 patients without primary cardiac diagnoses. It was present in 6/71 patients with respiratory disease, 5/54 with GI bleeding, 5/16 with sepsis, 2/13 with ketoacidosis, 1/5 with electrolyte disturbances, 1/3 with neurologic disease and 1 with traumatic hemothorax. Mortality for patients with myocardial injury, whether recognized or not, was 41% compared to 15% for those without injury (p &lt; 0.001). Patients with cardiac injury also were more apt to be hypotensive (75% vs. 50%, P = 0.007) and require mechanical ventilation (66% vs. 27%, P &lt; 0.0001). These data indicate that myocardial injury is surprisingly common in critically ill MICU patients, difficult to recognize, and associated with increased morbidity and mortality.

A nonequilibrium radioimmunoassay for angiotensin II

A method for the measurement of angiotensin II levels in dog plasma is described. The method is similar to previously published assays in that it couples gradient high-performance liquid chromatography (HPLC) with radioimmunoassay (RIA) and requires blood sample collection and processing to plasma in the presence of protease inhibitors. The unique feature of the present method is that it utilized a commercially available angiotensin II RIA run under nonequilibrium conditions. Performing the angiotensin II RIA under nonequilibrium conditions increased RIA sensitivity to allow for a minimal detectable limit of 0.75 pg/mL, a limit of detection not achievable with current commercially available RIAs. This lower limit of detection will now allow for the measurement of circulating levels of angiotensin II. Quality control pools of dog plasma fortified with 4.59–50 pg/mL angiotensin II were assayed and analytical recoveries (ARs) and coefficients of variation (CV) of 72.2%–111% and 3.67%–19.0% were observed for the respective pools.

In Vivo Verification of an Automatic Noninvasive System for Real Time Kt Evaluation

It is generally accepted that morbidity and mortality of hemodialysis patients is related to dialysis quantitation. Currently available methods for the quantitation of dialysis require blood sampling or a continuous measurement of changes in urea concentration during treatment. These maneuvers are time consuming and expensive, and are generally performed, at most, once per month. The authors introduce an on-line, automated method for measurement of dialyzer electrolyte clearance comparable to urea clearance by using dialysate conductivity sensors placed pre and post dialyzer, and measuring conductivity at three different pre dialyzer levels. Conditions that reduce clearance, such as recirculation or fiber clotting, are automatically taken into account so that the method measures effective clearance rather than dialyzer clearance. In vitro and in vivo studies validate the method. Results are immediately available and can be used to address problems such as improper needle placement and access recirculation. In addition, repetitive electrolyte clearance data can serve to enhance quality assurance programs with respect to verifying the function of reused or new dialyzers. Appropriate algorithms can be used to calculate delivered Kt/V.

NSAIDs: New Approaches to Limiting Gastropathy

An extensive literature search on non-steroidal anti-inflammatory drug (NSAID)-induced gastropathy in rheumatic conditions has been carried out. A reduced incidence of gastropathy has been observed among newly developed NSAIDs such as etodolac and the non-acidic nabumetone. An alternative prophylactic therapy to avoid NSAID-induced gastroduodenal mucosal damage which has been successfully tested in several trials is co-medication with the prostaglandin analogue misoprostol. The cytoprotective agent sucralfate also appears to be effective. Recent observations of Campylobacter pylori infections in NSAID-induced gastropathy introduces the question as to whether simultaneous antibacterial medication should be routinely administered during NSAID therapy. At present the invasive technique of endoscopy is used to ascertain gastroduodenal mucosal damage. However, a new technique which merely requires blood sampling is being investigated. This involves measurement of serum levels of the precursor molecules for the gastric enzyme pepsin, pepsinogen I and II. In future this assay could constitute a non-invasive method for detecting gastroduodenal mucosal damage.

Correlation of Serum and Salivary Cortisol Levels in Prepubertal School-Aged Children

Abstract The dexamethasone suppression test (DST) is useful in assessing major depression in children, but it requires blood sampling, which is unpleasant. Two studies have demonstrated strong correlations between serum and salivary cortisol levels in combined samples of children and adolescents administered DSTs. The present study replicated these findings in 15 prepubertal children. Overall, serum and salivary samples were significantly correlated, as were those from specific time periods ( r = 0.86 to 0.97). A salivary cortisol level of 0.14 μg/dl separated DST nonsuppressors from suppressors. Salivary cortisol samples could be used in place of serum samples when performing the DST.

5 The impact of DNA analysis on fetal diagnosis

There has been rapid progress in mapping disease-specific gene loci to particular chromosomal regions and in cloning the relevant genes or DNA sequences that can act as genetic markers. These advances will have an impact on fetal diagnosis of monogenic disorders for a number of reasons, the most important being the ability to use chorionic villus DNA taken in the first trimester to make a fetal diagnosis, no matter how tissue-specific the gene defect. Diagnosis based on analysis of the protein gene product requires a tissue that is expressing that gene. In a few disorders the mutation within the gene can be detected directly, but more often an approach, termed gene tracking, will be required to predict the genotype of the fetus. This requires blood samples from a few family members and the analysis must be carried out prior to the chorion sampling and ideally before the pregnancy. This initial family study is required to determine whether gene tracking is possible in that particular family. A number of potential problems, both technical and in clinical management, highlight the need for close collaboration between clinical geneticists, molecular geneticists and obstetricians.

Platelet activation caused by cardiac catheter blood collection, and its prevention

The study of platelet changes occurring across the coronary circulation is important in the investigation of the platelet's role in ischemic heart disease. It requires blood sampling through cardiac catheters. This could activate platelets and alter the results of tests of platelet activation and reactivity. This study was designed to examine this problem and to devise satisfactory methods for obtaining blood for platelet studies through long catheters. Blood collected through catheters introduced with a guide-wire had a much higher plasma heparin neutralising activity(HNA), platelet factor 4(PF4)and beta-thromboglobulin(βTG) than peripheral venous blood, and lower platelet count(PC). Blood collected through catheters introduced via a sheath, and kept filled with anticoagulant/antiplatelet solution until blood sampling, gave results similar to peripheral venous blood for the PC, platelet aggregate ratio, platelet fluorescent granule count, and for plasma HNA, PF4 and βTG. It is concluded that platelets are activated during blood collection through cardiac catheters; however, with appropriate precautions, blood which is satisfactory for platelet studies can be obtained.

Assessment of the optimal anticoagulant solution for storage of whole blood samples prior to measurement of platelet-associated IgG.

The complexity of assays used to measure platelet-associated IgG (PAIgG) often requires blood samples to be sent to a central laboratory, In order to determine the optimal storage conditions, we measured PAIgG, platelet recovery, and platelet size serially over several days in whole blood samples obtained from healthy individuals. Blood was collected into EDTA, acid-citrate-dextrose (ACD) and citrate-phosphate-dextrose-adenine (CPD-A) with and without the fixative paraformaldehyde (P). The level of PAIgG remained with normal limits in all samples stored for up to six days in the ACD, the CPD-A and the CPD-A-P samples. The least drop in platelet count and change in platelet size occurred in the ACD and CPD-A samples. Blood collected into EDTA plus paraformaldehyde was less satisfactory, with PAIgG rising by day three in some samples, and a decline in the platelet count occurring by day two. Specimens collected into EDTA alone were least satisfactory, with a rise in PAIgG by 24 hours after collection. Collection of whole blood into either ACD or CPD-A and storage at 22 degrees C allows a good recovery of platelets whose level of PAIgG is unchanged for up to six days.

Continuous measurement of blood gas tensions in the fetal guinea pig by mass spectrometry.

Recent progress in the measurement of intravascular blood gas tensions by mass spectrometry [8, 13] is of potential interest in the study of placental gas exchange, because the mass spectrometer allows continuous measurement of both p02 and pC02. The determination of blood gases by conventional techniques, which mostly require blood sampling, has contributed significantly to the investigation of placental gas exchange [6, 11, 16]. Mass spectrometry, however, can give important additional Information about the kinetics of transplacental gas exchange. The guinea pig is an important model in placental research, because its discoid, haemomonochorial placenta resembles that of man [7]. Hitherto, the study of placental gas exchange in this species has been limited, because conventional methods of gas analysis require blood samples that are large in relation to the blood volume of the fetus. In the present study, we have investigated the feasibility of monitoring the blood gases of fetal guinea pigs by mass spectrometry, using an intravascular probe developed for this purpose [13]. Simultaneous and continuous measurements of p02 and pC02 in the right atrium of the fetuses were made before, during and after an acute change in maternal placental blood flow provoked by an infusion of noradrenaline. Curriculum vitae

Measurement of Red Blood Cell Life-Span

The life-span of the red blood cell (RBC) is difficult to estimate clinically, as hemolysis may exist in the presence of normal levels of hemoglobin and bilirubin, as well as normal reticulocyte counts. Clinically useful methods for quantification of the RBC life-span include isotope methods and measurement of endogenous carbon monoxide production. Chromium 51 is the isotope most widely used but has the disadvantage of requiring blood sampling for 30 days. Measurement of endogenous carbon monoxide production has the advantage of sensitivity to low-grade hemolysis and requires only three hours of the patient's time. It is potentially useful for demonstrating changing levels of hemolysis related to drug therapy or autoimmune states. (<i>JAMA</i>230:1304-1305, 1974)

Isotope dilution studies of the effect of insulin and diabetes on glucose transfer rates.

A review is presented of isotopic dilution and other techniques designed to study the effect of the diabetic state and insulin on glucose transfer rates. Since in man the required blood samples from the liver cannot be obtained, tracer methods remain the sole means of investigating glucose kinetics. A series of techniques involving administration of 14C-glucose has been devised for this purpose. Critical analysis of these procedures led to a revised concept of the exchangeable body glucose mass; an operational definition recognising delayed intermixing in principle was substituted for attempts to set up models of compartmental structure. Although each tracer technique is beset with certain limitations, methods using either tracer injection or infusion appear to be capable of yielding valid data, if properly selected according to the type of information desired.

Studies of cardiopulmonary blood volume. Measurement of left ventricular volume by dye dilution.

The measurement of ventricular end-diastolic volume from washout of an indicator requiring blood sampling was studied in a heart model and in dogs and applied to the left ventricle in 34 human subjects. The model, under the ideal conditions of constant ejection fraction, uniform cycle length, and complete or nearly complete mixing, demonstrated that dye dilution accurately measures chamber volumes if the distorting effects of catheter sampling are obviated by clearance of the sampling system at least once per two cardiac cycles. The studies in dogs and in human beings demonstrated that the required sampling conditions are achievable. In 11 normal human subjects, left ventricular end-diastolic volume ranged from 72 to 99 with a mean of 82 ± 12 ml/m, 2 end-systolic volume, from 22 to 60 with a mean of 37 ± 11 ml/m, 2 and ejection fraction, from 0.39 to 0.71 with a mean of 0.55 ± 0.08. These measurements are in substantial agreement with results by radiocardiography and thermal dilution and are systematically, but only slightly, higher than results by quantitative angiocardiography. In six considerably older patients with chronic pulmonary disease, cardiac output was normal for the age group but ejection from a ventricle of normal size was reduced. In 12 subjects with pure mitral stenosis and in five with atrial septal defect, end-diastolic volume and ejection fraction were significantly reduced. End-diastolic volume correlated with stroke volume in all groups and in the series as a whole, but a correlation between end-diastolic volume and cardiac output was demonstrated only in the patients with mitral stenosis or atrial septal defect. This suggests that chronic restriction to ventricular filling results in decreased end-diastolic volume. The absence of a significant correlation between end-diastolic volume and end-diastolic pressure indicates that variation in ventricular compliance precludes reliance on end-diastolic pressure as a valid index of end-diastolic fiber length.