Current Issues in Blood Gas Analysis

Effect of Hemolysis on Routine Blood Gas and Whole Blood Analytes

BACKGROUND

Hemolysis is a major pre-analytical concern for many laboratory analytes; however, instruments utilized for whole blood chemistries and blood gas measurements lack the ability to detect and measure the degree of hemolysis. This study evaluated the effect of hemolysis on 13 routine whole blood and blood gas analytes and compared visual assessments of hemolysis to measured hemolysis (H-index).

METHODS

Remnant whole blood samples (n = 85) were split into 2 portions and aspirated through a syringe one or more times. To induce hemolysis, a needle was affixed to the end of the syringe to provide shear stress, and a mock procedure without syringe was used as a control. Samples were analyzed on a Radiometer ABL800 series instrument, centrifuged, and the H-index of the plasma portion was measured. Two medical technologists recorded a visual categorization of the specimens as slightly, moderately, or severely hemolyzed.

RESULTS

Hemolysis had a modest effect on metabolites and most cooximetry components, with percent bias within ±5% at all levels of hemolysis. Methemoglobin exhibited a larger overall negative bias, up to 13.3%. The absolute pH bias was fairly consistent (within 0.1 pH units) across all levels of hemolysis. As expected, potassium displayed a significant positive bias with increasing hemolysis. Sodium and ionized calcium displayed overall linear trends with a significant negative bias.

CONCLUSIONS

Hemolysis can falsely increase or decrease certain blood gas analytes and lead to misinterpretation of results. Therefore, hemolysis detection capabilities are crucial for mitigating this effect and ensuring accurate results for patient care.

Novel In-Line Hemolysis Detection on a Blood Gas Analyzer and Impact on Whole Blood Potassium Results

BACKGROUND

Preanalytical error due to hemolyzed blood samples is a common challenge in laboratory and point-of-care (POC) settings. Whole blood potassium (K+) measurements routinely measured on blood gas analyzers are particularly susceptible to hemolysis, which poses a risk for incorrect K+ results. The GEM Premier 7000 with IQM3 (GEM 7000) blood gas analyzer provides novel integrated hemolysis detection within the sample measurement process. Therefore, the GEM 7000 can detect and flag hemolyzed whole blood samples at the POC, warning the operator of potentially erroneous results.

METHODS

Heparinized venous or arterial whole blood samples were used for K+ interference studies and assessed for hemolysis agreement utilizing either a traditional volumetric method or chemistry analyzer serum index measurements with the Roche cobas c311 or Abbott Alinity c.

RESULTS

Hemolysis interference studies performed at 2 different K+ concentrations (3.8 and 5.3 mmol/L) identified that a plasma free hemoglobin ≥116 mg/dL can impact K+ results on the GEM 7000. Hemolysis agreement studies demonstrated an excellent agreement of >99% with the volumetric method, 98.8% with cobas H index, and 96.4% with Alinity H index. GEM 7000 K+ results were correctly flagged for both native and spiked samples.

CONCLUSION

GEM 7000 hemolysis detection provides a novel technology to detect hemolysis in whole blood samples. Moreover, the GEM 7000 demonstrates excellent agreement with traditional laboratory hemolysis detection methods and offers an integrated technological solution for assuring the quality of whole blood K+ results in POC settings.

Numerical and in vitro experimental studies for assessing the blood hematocrit and oxygenation with the dual-wavelength photoacoustics

Assessing the blood hematocrit (Hct) and oxygenation (SO2 ) levels are essential for diagnosing numerous blood-related diseases. This study examines the ability of the photoacoustic (PA) technique for quantitative evaluation of these parameters. We conducted the Monte Carlo and k-Wave simulations to compute PA signals at four different optical wavelengths from test blood samples followed by rigorous in vitro experiments. This method can estimate the Hct and SO2 levels faithfully with ≥ 95% and ≥ 93% accuracies, respectively in the physiologically relevant hematocrits utilizing PA signals generated at 700 and 1000 nm optical wavelengths. A 2% decrease in the scattering anisotropy factor demotes SO2 estimation by ≈ 27%. This study provides sufficient insight into how the opto-chemical parameters of blood impact PA emission and may help to develop a PA setup for in vitro characterization of human blood.

Effect of exogenous lipids contamination on blood gas analysis

Objectives

The purpose of this study was to investigate the effects of contamination of venous blood with a lipid-containing solution on parameters measured by a modern blood gas analyzer.

Methods

We collected venous blood from 17 healthcare workers (46 ± 11 years; 53 % women) into three blood gas syringes containing 0 , 5 and 10 % lipid-containing solution. Blood gas analysis was performed within 15 min from sample collection on GEM Premier 5000, while triglycerides and serum indices were assays on Roche COBAS C702.

Results

Triglycerides concentration increased from 1.0 ± 0.3 mmol/L in the uncontaminated blood gas syringe, to 39.4 ± 7.8 and 65.3 ± 14.4 mmol/L (both p<0.001) in syringes with 5 and 10 % final lipid contamination. The lipemic and hemolysis indices increased accordingly. Statistically significant variation was noted for all analytes except hematocrit and COHb in the syringe with 5 % lipids, while only COHb did not vary in the syringe with 10 % lipids. Significant increases were observed from 5 % lipid contamination for pO2, SO2 and lactate, while the values of pH, pCO2, sodium, potassium, chloride, ionized calcium, glucose, hematocrit (10 % contamination), hemoglobin and MetHB decreased. All these changes except lactate and CoHb exceeded their relative performance specifications.

Conclusions

Artifactual hyperlipidemia caused by contamination with exogenous lipids can have a clinically significant impact on blood gas analysis. Manufacturers of blood gas analyzers must be persuaded to develop new instruments equipped with serum indices.

Efecto de la contaminación por lípidos exógenos en la gasometría

Objetivos

El objetivo del presente estudio es investigar los efectos de la contaminación de sangre venosa por una solución de lípidos sobre diferentes parámetros, determinados en un moderno analizador de gases en sangre.

Métodos

Se extrajo sangre venosa de 17 profesionales sanitarios (46±11 años; 53 % mujeres) y se introdujo en tres jeringas de gasometría, que contenían una solución de lípidos al 0 %, 5 % y 10 %. En los 15 minutos siguientes a la extracción de la muestra, se realizó la gasometría con un analizador GEM Premier 5000. Los triglicéridos e índices séricos se analizaron en el dispositivo COBAS C702 de Roche.

Resultados

La concentración de triglicéridos aumentó de 1.0±0.3 mmol/L en la jeringa de gasometría no contaminada a 39,4±7,8 y 65,3±14,4 mmol/L (ambas p<0.001) en las jeringas con contaminación por lípidos al 5 % y al 10 %. Como consecuencia, los valores de los índices lipémico y hemolítico aumentaron. Observamos una variación estadísticamente significativa en todos los analitos, excepto en el hematocrito y la COHb en la jeringa con lípidos al 5 %, siendo COHb el único analito que no varió en la jeringa con lípidos al 10 %. Los valores de pO2, SO2 y lactato aumentaron significativamente a partir del 5 % de contaminación por lípidos, mientras que se produjo un descenso de los valores de pH, pCO2, sodio, potasio, cloruro, calcio ionizado, glucosa, hematocrito (contaminación al 10 %), hemoglobina y MetHB. Todas estas variaciones, excepto en el caso del lactato y la CoHb, superaron sus especificaciones de calidad relativa.

Conclusiones

La hiperlipidemia artefactual causada por la contaminación por lípidos exógenos podría tener un impacto clínicamente significativo en los resultados de la gasometría. Se debe instar a los fabricantes de analizadores de gases en sangre a que desarrollen nuevos instrumentos que incluyan la determinación de índices séricos.

The Predictive Role of Lactate in the Emergency Department in Patients with Severe Dyspnea

Objective

An accurate identification of patients at the need for prioritized diagnostics and care are crucial in the emergency department (ED). Blood gas (BG) analysis is a widely available laboratory test, which allows to measure vital parameters, including markers of ventilation and perfusion. The aim of our analysis was to assess whether blood gas parameters in patients with dyspnea at an increased risk of respiratory failure admitted to the ED can predict short-term outcomes.

Methods

The study group eventually consisted of 108 patients, with available BG analysis. The clinical and laboratory parameters were retrospectively evaluated, and three groups were distinguished-arterial blood gas (ABG), venous blood gas (VBG), and mixed blood gas. The primary endpoint was short-term, all-cause mortality during the follow-up of median (quartile 1-quartile 3) 2 (1-4) months. The independent risk factors for mortality that could be obtained from blood gas sampling were evaluated.

Results

The short-term mortality was 35.2% (38/108). Patients who died were more frequently initially assigned to the red triage risk group, more burdened with comorbidities, and the median SpO2 on admission was significantly lower than in patients who survived the follow-up period. In the multivariable analysis, lactate was the strongest independent predictor of death, with 1 mmol/L increasing all-cause mortality by 58% in ABG (95% CI: 1.01-2.47), by 80% in VBG (95% CI: 1.13-2.88), and by 68% in the mixed blood gas analysis (95% CI: 1.22-2.31), what remained significant in VBG and mixed group after correction for base excess. In each group, pH, pO2, and pCO2 did not predict short-term mortality.

Conclusions

In patients admitted to the ED due to dyspnea, at risk of respiratory failure, lactate levels in arterial, venous, and mixed blood samples are independent predictors of short-term mortality.