Measured Potassium Concentration Research Articles

Pseudohyperkalemia Revisited: An Updated Review of a Foremost Preanalytical Error of Serum or Plasma Potassium Measurement in the Clinical Laboratory

Abstract Background: Potassium is one of the most abundant cations in the human body. Increased plasma potassium concentration (hyperkalemia) is one of the most common electrolyte abnormalities in contemporary clinical practice. Moderate and severe hyperkalemia are potentially life-threatening conditions and constitute medical emergencies. Measured hyperkalemia may be true hyperkalemia or false hyperkalemia (pseudohyperkalemia). Pseudohyperkalemia is due to false elevation of measured potassium concentration in vitro and it is a fairly common source of preanalytical error of potassium determination in the clinical laboratory. Objective: To review the general and recent concepts/mechanisms that underlie the phenomenon of pseudohyperkalemia in contemporary clinical practice. Methods: An up-to-date review of available literature and selected references on the phenomenon of pseudohyperkalemia, its causes, variants, mechanisms, clinical implications, identification, management, and prevention. Conclusion: Pseudohyperkalemia is a fairly common preanalytical error of potassium measurement in the clinical laboratory and a potential cause of misdiagnosis and unnecessary treatment of hyperkalemia. Exclusion of pseudohyperkalemia before the diagnosis of hyperkalemia (true hyperkalemia) is highly recommended.

Ion concentration measurement using synthetic microfluidic papers.

Non-invasive diagnosis on biological liquid samples, such as urine, sweat, saliva, and tears, may allow patients to evaluate their health by themselves. To obtain accurate diagnostic results, target liquid must be precisely sampled. Conventionally, urine sampling using filter paper can be given as an example sampling, but differences in the paper structure can cause variations in sampling volume. This paper describes precise liquid sampling using synthetic microfluidic papers, which are composed of obliquely combined micropillars. Sampling volume accuracy was investigated using different designs and collection methods to determine the optimal design and sample collecting method. The optimized protocol was followed to accurately measure potassium concentration using synthetic microfluidic paper and a commercially available densitometer, which verified the usefulness of the synthetic microfluidic papers for precision sampling.

Quantification of wastewater pollution load using potassium concentrations in karst spring discharges

Karst aquifers are highly vulnerable to pollution because of their unique and complex hydrogeological characteristics. Within this study, measured potassium concentrations in both, the Tanour and Rasoun spring discharges were employed to quantify the component of leaked wastewater either from local olive mills (Tanour spring) or domestic wastewater (Rasoun spring). Additionally, high-resolution physico-chemical data were recorded in both springs using an online automated telemetric station to investigate the response of the Tanour and Rasoun karst aquifer to pollution events. Measured potassium concentrations during spring discharge peaks were clearly indicative of pollution events in contrast to other ions and the Chloride-Bromide mass ratio. Undiluted leaked wastewater discharge rates from the olive mills and domestic wastewater during the whole monitoring period were estimated (mean/max) to be 6.4 m3 d−1 and 93.6 m3 d−1 for Tanour spring and 9.8 m3 d−1 and 52.3 m3 d−1 for Rasoun spring, respectively.

DEVELOPMENT OF A PORTABLE BLOOD POTASSIUM MONITORING DEVICE FOR DIALYSIS PATIENTS.

Approximately 500,000 dialysis patients in America are at a high risk of hyperkalemia, a condition where blood potassium becomes elevated above normal levels. Hyperkalemia is extremely dangerous, as it can result in severe cardiac complications if untreated. Hyperkalemia may be silent or present vague symptoms until those complications develop, at which point patients require emergency medical care. However, if patients have the ability to measure their potassium levels at home, they could detect hyperkalemia before it reaches a dangerous stage, and seek preventative medical care to avoid severe complications. Therefore, we have designed a novel device allowing patients to measure their blood potassium levels at home. The workflow of our solution is as follows: (1) patients obtain a blood sample from a finger prick, (2) potassium concentration is measured with an ion specific electrode (ISE), and (3) the device displays their potassium levels and a recommended course of action based on their hyperkalemic risk. We validate our solution with three major tests. First, our portable ISE technology must accurately measure potassium concentration in blood samples. Second, appropriate lancet parameters (gauge and depth) to minimize hemolysis in capillary blood samples must be found to minimize falsely elevated readings. Third, device portability and ease of use must be evaluated using patient input, as these factors will affect patient compliance. We have validated the use of portable ISE technology to feasibly measure potassium, and we continue to collect data for our second and third tests.

Microfluidic DNA-based potassium nanosensors for improved dialysis treatment

BackgroundPatients with end-stage renal disease (ESRD) have failed kidney function, and often must be treated with hemodialysis to extend the patient’s life by artificially removing excess fluid and toxins from the blood. However, life-threatening treatment complications can occur because hemodialysis protocols are adjusted infrequently, as opposed to the kidneys which filter blood continuously. Infrequent blood tests, about once per month on average, are used to adjust hemodialysis protocols and as a result, patients can experience electrolyte imbalances, which can contribute to premature patient deaths from treatment complications, such as sudden cardiac death. Since hemodialysis can lead to blood loss, drawing additional blood for tests to assess the patient’s kidney function and blood markers is limited. However, sampling multiple drops of blood per session using a microfluidic device has the potential to reduce not only the amount of blood drawn and avoid unnecessary venipuncture, but also reduce costs by limiting medical complications of hemodialysis and provide a more comprehensive assessment of the patient’s health status in real time.ResultWe present preliminary proof-of-concept results of a microfluidic device which uses DNA-based fluorescence nanosensors to measure potassium concentration in a flowing solution. In a matter of minutes, the flowing potassium solution reduced the fluorescence intensity of the nanosensors to a steady-state value.ConclusionsThese proof-of-concept results demonstrate the ability of our DNA-based nanosensors to measure potassium concentration in a microfluidic device. The long-term goal is to integrate this technology with a device to measure potassium and eventually other blood contents multiple times throughout a hemodialysis session, enabling protocol adjustment similar to a healthy kidney.

Establishing evidence-based thresholds and laboratory practices to reduce inappropriate treatment of pseudohyperkalemia

BackgroundUnrecognized pseudohyperkalemia (PHK), defined as an artificial increase in measured potassium concentration, due to thrombocytosis and leukocytosis can lead to inappropriate patient treatment. Understanding the laboratory and patient characteristics that increase risk of PHK is key to preventing diagnostic errors. MethodsSerum/plasma potassium results collected at 2 laboratories over 4years were selected based on blood cell counts collected within 24h and whole blood potassium concentrations determined within 2h of the serum/plasma sample. Differences between whole blood and serum or plasma potassium were compared as functions of platelet or leukocyte count, fit to linear models, and stratified based on leukemia diagnosis codes. Patients having a serum/plasma potassium concentration that was at least 1mEq/mL higher than the whole blood concentration were defined as having PHK. Based on this analysis, high-risk patients were prospectively identified and PHK risk was communicated to providers. Medication administration records were queried to compare rates of kayexalate use pre- and post-intervention. ResultsApproximately 14% of serum samples with platelet counts >500×109/L had a>1mEq/L increase relative to whole blood potassium. >25% of serum and plasma samples showed a>1mEq/L increase relative to whole blood potassium when leukocyte counts were >50×109/L. Patients with chronic lymphocytic leukemia and high WBC count demonstrated the highest rates of PHK. The rate of kayexalate administration prior to confirmatory testing decreased from 37% to 16% after the laboratory started verbally communicating the possibility of PHK to treating providers. ConclusionsAccording to our data, a leukocyte count threshold for plasma samples of 50×109/L is appropriate for indicating a high risk of PHK. Direct communication by the laboratory to the care team reduces inappropriate potassium lowering treatment in populations at high risk.

Validation of hemolysis index thresholds optimizes detection of clinically significant hemolysis.

Automated hemolysis index (HI) measurement has standardized the identification and gradation of sample hemolysis. This study evaluates whether clinically significant changes in the concentration of intracellular analytes occur at manufacturer-recommended automated HI thresholds (HI ≥3, >25 mg/dL hemoglobin). Adult outpatient results for serum potassium (K+), magnesium (Mg), lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) were analyzed. Mean ± SD analyte concentration and distribution within the reference interval (RI) were calculated for each HI group (1-7). Potassium results with an HI of 4 or more demonstrated clinically significant differences (≥0.5 mmol/L) in mean K+ concentration and RI classification compared with non-hemolyzed samples (HI = 1). LDH and AST showed clinically significant differences (+20%) for an HI of 3 or more. For Mg, only the group with an HI of 7 demonstrated a clinically significant difference (>25%); however, the number was low. Mean measured potassium concentrations are not clinically significantly affected by hemolysis at the manufacturer-recommended HI threshold, while AST and LDH are. Aligning reporting of sample hemolysis with clinically significant changes provides clinically meaningful alerts regarding this common pre-analytic error.

Studies on the use of BD Vacutainer® SST II™ and RST™ in general practice: investigation of artefactual hyperkalaemia

Current sampling and transport conditions of samples in general practice can result in pseudohyperkalaemia. This study was undertaken to determine, in a general practice setting, whether there is any difference in haemolysis obtained when using BD Vacutainer® Rapid Serum Tubes (BD RST) compared with using BD Vacutainer® SST™ II Advance Blood Collection Tubes (BD SSTII). Blood was collected from 353 patients requiring blood sampling who were attending 31 general practitioner practices in Belgium. For each patient, two BD SSTII tubes and two BD RST tubes were drawn in a randomized order. One of each pair of tubes was inverted five times, the other was not. Serum potassium concentration, serum LDH activity and haemolysis index were measured in each sample. There was no significant difference in measured potassium concentration according to tube type (P = 0.16). Measured LDH activities were 1.7% higher in serum collected into BD SSTII tubes compared to BD RST tubes (P = 0.02). When comparing serum from unmixed BD RST with BD SSTII tubes, there was a slight reduction in the haemolysis index but no significant difference in measured potassium concentration or LDH activity. Risk of hyperkalaemia was 4.8 times higher in serum from tubes that were incompletely filled compared to those that were filled with the correct amount of blood. Both types of blood tubes are suitable for the measurement of serum potassium and LDH in patients from general practice. Tube inversion does not improve the accuracy of either serum potassium or LDH measurement. Blood tubes should be filled to the level recommended by the manufacturer to avoid artefactual increases in measured serum potassium concentration and LDH activity.

In Vivo39K MR Imaging of Human Muscle and Brain

To implement potassium 39 ((39)K) magnetic resonance (MR) imaging with a 7-T MR imaging system and to evaluate its feasibility for in vivo imaging of human muscle and brain. Three healthy volunteers were examined with approval of the ethical review board of Heidelberg University. Written informed consent was obtained from all volunteers. Because the available 7-T MR imaging system did not support (39)K, a frequency conversion scheme was developed and connected to the imaging unit. The standard X-nucleus frequency of lithium 7 (115 MHz) was converted to the frequency of (39)K at 7 T (14 MHz). Relaxation times of healthy thigh muscle and brain tissue were estimated by using multiple-echo and inversion-recovery sequences. Data analysis was conducted with a nonlinear least squares curve fitting tool. In vivo (39)K MR imaging of healthy human thigh muscle and brain was performed. With use of the custom-built frequency conversion scheme, (39)K MR imaging is feasible with a commercially available 7-T MR imaging system. Nominal spatial resolutions of 8 × 8 × 16 mm(3) and 9.5 × 9.5 × 9.5 mm(3) were achieved for human thigh muscle and brain, respectively. Acquisition time was 30 minutes for both muscle and brain tissue. The measured potassium concentration (uncorrected for fat fraction) of thigh muscle tissue (112-124 mmol/L) lies within the expected range. In vivo (39)K MR imaging in humans can be performed in clinically feasible measurement times (approximately 30 minutes) with voxel sizes of approximately 1 mL.

What Is Your Guess? Hyperkalemia or Hypokalemia?

Consecutive laboratory results for a 6-year-old girl at a cancer clinic consistently showed contradictory potassium concentrations in her plasma and whole blood specimens. Consultation with the bedside nurse and repeat blood sampling ruled out the possibility of sample contamination. Electrocardiogram monitoring revealed normal cardiac function. 1. Which measured potassium concentration reflects the physiological potassium concentration? 2. What caused the discrepancy …

Correction factors for estimating potassium concentrations in samples with in vitro hemolysis: a detriment to patient safety.

Abstract Context.—Correction factors have been proposed for estimating true potassium concentrations in blood samples with evidence of in vitro hemolysis. Objective.—We used 2 different models of true (ie, nonsimulated) in vitro hemolysis to evaluate the clinical utility of correction factors for estimating potassium concentrations in samples with evidence of in vitro hemolysis. Design.—Potassium correction factors were derived using 2 different models. In model 1, potassium and plasma hemoglobin were measured with the Hitachi 747 analyzer in 132 paired blood samples, with each pair consisting of 1 sample with evidence of hemolysis and 1 without, collected during the same phlebotomy procedure. The change in measured potassium concentration was plotted versus the change in plasma hemoglobin concentration for each pair of samples. In model 2, the potassium levels of 142 784 blood samples and the corresponding hemolytic index values were measured with the Beckman LX20 analyzer. Potassium concentrations at th...

Correction Factors for Estimating Potassium Concentrations in Samples With In Vitro Hemolysis: A Detriment to Patient Safety

Correction factors have been proposed for estimating true potassium concentrations in blood samples with evidence of in vitro hemolysis. We used 2 different models of true (ie, nonsimulated) in vitro hemolysis to evaluate the clinical utility of correction factors for estimating potassium concentrations in samples with evidence of in vitro hemolysis. Potassium correction factors were derived using 2 different models. In model 1, potassium and plasma hemoglobin were measured with the Hitachi 747 analyzer in 132 paired blood samples, with each pair consisting of 1 sample with evidence of hemolysis and 1 without, collected during the same phlebotomy procedure. The change in measured potassium concentration was plotted versus the change in plasma hemoglobin concentration for each pair of samples. In model 2, the potassium levels of 142 784 blood samples and the corresponding hemolytic index values were measured with the Beckman LX20 analyzer. Potassium concentrations at the 10th, 25th, 50th, 75th, and 90th percentiles were calculated for each hemolysis index category. From our 2 models, we derived correction factors expressing an increase in potassium concentration of 0.51 and 0.40 mEq/L for every increase in plasma hemoglobin concentration of 0.1 g/dL. These correction factors are much higher than those reported in studies that simulated in vitro hemolysis by freeze-thaw lysis or osmotic disruption of whole blood. Use of correction factors for estimating the true potassium concentration in samples with evidence of in vitro hemolysis is not recommended. Derivation of correction factors by using samples with nonsimulated in vitro hemolysis suggests that the actual increase in potassium in hemolyzed samples is much higher than that reported in previous studies that produced hemolysis with artificial means.

Are your hands clean enough for point-of-care electrolyte analysis?

SummaryAimTo investigate clinically significant analytical interference in point-of-care electrolyte analysis caused by contamination of blood specimens with hand disinfectant.MethodsSix different hand hygiene products were added separately to heparinised blood samples in varying amounts as contaminant. The contaminated samples were analysed by three different blood gas and electrolyte analysers for assessing interference on measured whole blood sodium and potassium concentrations.ResultsThere were significant analytical interferences caused by hand hygiene product contamination that varied depending on the combination of disinfectant and analyser. Small amounts of Microshield Antibacterial Hand Gel contamination caused large increases in measured sodium concentration. Such effect was much greater compared with the other five products tested, and started to occur at much lower levels of contamination. There was a trend towards lower sodium results in blood samples contaminated with Hexol Antiseptic Lotion (Hexol), the hand hygiene product that we used initially. Apart from AiE Hand Sanitizer, all the other hand disinfectants, especially Hexol, significantly elevated the measured potassium concentration, particularly when a direct ion-selective electrode method was used for measurement.ConclusionHand disinfectant products can significantly interfere with blood electrolyte analysis. Proper precautions must be taken against contamination since the resultant errors can adversely affect the clinical management of patients.

A 1.3 mu m directional coupler polarization splitter by ion exchange

A glass waveguide polarization splitter for operation in the 1.3 mu m wavelength region is reported. The device, which has a symmetric directional coupler configuration, exploits the stress-induced birefringence in K/sup +/-Na/sup +/, ion-exchanged waveguides, giving rise to an adequate difference in the coupling lengths for the two polarizations. Starting from the measured potassium concentration (refractive index) profile of the structure and utilizing a combination of the multilayer stack theory and the effective-index method, the normal mode propagation constants and mode field profiles are calculated to determine the polarization splitting length and the extinction ratio, and the results are compared with the experimental data. It is shown that in a given coupler, the splitting occurs at several wavelengths in the 1.0-1.45 mu m range. A 25 mm-long coupler, fabricated by thermal diffusion of K/sup +/ ions in BK7 glass, exhibits an extinction ratio of 18.2 dB at 1.32 mu m, in excellent agreement with the simulation results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>