Comparison of Point-of-Care versus Central Laboratory Testing of Electrolytes, Hemoglobin, and Bilirubin in Neonates

Objective Electrolyte, hemoglobin, and bilirubin values are routinely reported with point-of-care (POC) testing for blood gases. Results are rapidly available and require a small blood volume. Yet, these results are underutilized due to noted discrepancies between central laboratory (CL) and POC testing. The study aimed to determine the correlation between POC and CL measurement of electrolytes, hemoglobin, and bilirubin in neonates. Study Design Electrolyte, hemoglobin, and bilirubin results obtained from capillary blood over a 4-month period were analyzed. Each CL value was matched with a POC value from the same sample or another sample less than 1-hour apart. Agreement was determined by measuring the mean difference (MD) between paired samples with 95% limits of agreement (LOA) and Lin's concordance correlation (LCC). Results There were 355-paired sodium/potassium, 139 paired hemoglobin, and 197 paired bilirubin values analyzed. POC sodium values were lower (133.5 ± 5.8 mmol/L) than CL (140.2 ± 5.8 mmol/L), p <0.00001 with poor agreement (LCC = 0.49; MD = 6.7; 95% LOA: −13.6 to 0.14). POC potassium values were lower (4.6 ± 0.98 mmol/L) than CL (4.98 ± 1.24mEq/L), p < 0.0001, but with better concordance and agreement. (LCC = 0.6; MD = 0.4; 95% LOA: −2.3 to 1.4). There were no differences in hemoglobin between POC (14.3 ± 3.2 g/dL) and CL (14.4 ± 3.1 g/dL), p = 0.2 with good LCC (0.93) and in bilirubin values between POC (6.0 ± 3.2 mg/dL) and CL (5.8 ± 3.0 mg/dL), MD = 0.18, and p = 0.07. Conclusion POC Sodium values are lower than CL. POC potassium levels are also lower, but the differences may not be clinically important while hemoglobin and bilirubin levels are similar between POC and CL. As POC potassium, hemoglobin, and bilirubin levels closely reflect CL values, these results can be relied upon to make clinical judgments in neonates. Key Points

A Micro-fluidic System for the Evaluation of Blood Compatibility of Polymers

We present a new technique for the evaluation of polymer blood compatibility that makes use of a microchannel array flow analyzer and we describe and characterize the flow dynamics of this instrument. The blood compatibility of four polymers is quantitatively and qualitatively assessed and the results discussed. The blood is allowed to flow through the channels of a polymer coated micro-fluidic chip under adjustable pressure. The chip surface is investigated using optical microscopy during the blood flow and by scanning electron microscopy afterwards. Polymers known for having good blood compatibility exhibited higher flow rate values. Platelets were observed adhering, aggregating and obstructing the channels of the chips coated with polymers known for having poor blood compatibility. This technique has remarkable qualities such as a small blood volume requirement for material tests (100 μL), tuneable flow regimes and the use of human blood.

Biosensor assay of neuropathy target esterase in whole blood as a new approach to OPIDN risk assessment: review of progress

Organophosphates (OPs) that inhibit neuropathy target esterase (NTE) with subsequent ageing can produce OP-induced delayed neuropathy (OPIDN). NTE inhibition in lymphocytes can be used as a biomarker of exposure to neuropathic OPs. An electrochemical method was developed to assay NTE in whole blood. The high sensitivity of the tyrosinase carbon-paste biosensors for the phenol produced by hydrolysis of the substrate, phenyl valerate, allowed NTE activity to be measured in diluted samples of whole blood, which cannot be done using the standard colorimetric assay. The biosensor was used to establish correlations of NTE inhibitions in blood with that in lymphocytes and brain after dosing hens with a neuropathic OP. The results of further studies demonstrated that whole blood NTE is a reliable biomarker of neuropathic OPs for up to 96 hours after exposure. These validation results suggest that the biosensor NTE assay for whole blood could be developed to measure human exposure to neuropathic OPs as a predictor of OPIDN. The small blood volume required (100 μL), simplicity of sample preparation and rapid analysis times indicate that the biosensor should be useful in biomonitoring and epidemiological studies. The present paper is an overview of our previous and ongoing work in this area. Human & Experimental Toxicology (2007) 26, 273-282

Therapeutic drug monitoring principles in the neonate

Therapeutic drug monitoring in the newborn infant is necessary because dose requirements differ greatly from those for older children. These differences stem from major changes in kinetic disposition at the absorption, distribution, and elimination phases. The small blood volume of neonates makes them sensitive to iatrogenic blood loss. Similarly, the small size of these patients means that medication errors frequently lead to morbidity and even mortality. The clinical laboratory must set up strict, high-standard, carefully updated guidelines to ensure the safety of infants who need drug therapy at this very vulnerable phase of their lives.

Simulated Capillary Blood Flow Measurement Using a Nonlinear Ultrasonic Contrast Agent

This paper proposes a system for measuring slow, small volume blood flow, such as that found in the capillary beds. The method relies on the injection of a strongly nonlinear echocardiographic contrast agent, whose echoes are then analyzed by a modified Doppler process. The contrast agent is necessary to increase the signal-to-clutter ratio from the small blood volume, and to distinguish the blood movement from other moving structures, such as vessel walls or surrounding tissue. The nonlinear properties of this saccharide-based contrast agent are described, as evidenced by experimental evaluation. The contrast agent and signal processing modality are then tested in a blood flow simulator, at velocities as low as 1.5 mm/s, with good results. In addition, an analysis for applying this technique in vivo is presented, accounting for the dynamic and acoustic parameters of the physiological environment. Finally, some specific applications for this method are discussed, including its limitations.

Measurement of blood O2 and CO2 concentrations using PO2 and PCO2 electrodes

Accurate dilution of a small blood volume with a carbon monoxide-saturated solution allows measurement of the whole blood O2 concentration as an increase in O2 tension in the solution. We have improved the method by simplifying both equipment and procedure. We also suggest an additional step in which the mixture is acidified, thereby allowing the measurement of CO2 concentration in the same solution with a CO2 electrode. The accuracy of both the O2 and CO2 determinations compares favorably with that obtained with other micromethods.