Estimation of Haemoglobin with Arterial Blood Gas Analyzer Compared to Conventional Laboratory Methods in Intensive Care Unit

A sample of the patient's blood may be sent to the laboratory which allows (Haemoglobin) Hb to be measured using various methods, or the Hb value may be obtained by Arterial blood gas (ABG) analysis in the operating room or Intensive care unit. Our aim was to compare haemoglobin level obtained by Arterial blood gas Analyzer with Conventional laboratory method. A Comparative observational study was designed, patients admitted for trauma to Intensive Care Unit from April 2015 to July 2015 of Tertiary care teaching Hospital and Research centre. Categorical data was represented in the form of Frequencies and proportions. Continuous data was represented as mean and standard deviation. Independent t test was used. A total of 80 consecutive paired analyses were conducted. T test showed the difference between the two methods was statistically significant. Using the method of Bland and Altman, the overall mean difference in Hb concentration between the coulter counter and the blood gas analyzer was -4.3 g/l (95% CI = -11.0 to 2.4). Of the 11 (5.4%) Hb measurements that extended beyond the upper and lower 95% CI, 10 (5.0%) were within ±3 g/l of these confidence limits. We concluded that, an arterial blood gas analyzer may provide a valid alternative method to the traditional coulter counter for the rapid assessment of Hb concentration among critically ill adults.

Critical care medicine department has to assess electrolytes accurately and quickly to initiate the treatment. Blood samples are analyzed in a matter of seconds by arterial blood gas analyzers (ABG), albeit their accuracy is still up for debate. The current study objectives were to estimate and compare the levels of electrolytes (sodium, potassium, and chloride) in hospitalized critical care patients as determined by automated biochemistry analysis and blood gas analyzer and to assess the degree of agreement between the two instruments and obtain information on whether these values can be interchanged. A prospective hospital based observational study was undertaken after obtaining institutional ethical committee clearance. The study included a total of 195 paired venous and arterial samples from the patients admitted to Critical Care Medicine Unit of NIMS Hospital, Jaipur, India in whom electrolytes were analysed on Arterial Blood Gas (ABG) analyzer and Automated Biochemistry Analyzer (ABA). Analysis was done on ABL555 blood gas analyzer located in the critical care medicine unit and vitros 5600, located in Clinical Biochemistry. Statistical analysis was done using Student’s t test and Pearson’s correlation coefficient test.A total of 195 samples were analyzed. The mean levels of sodium, potassium and chloride were 136.64 ± 5.44 mmol/L, 3.87 ± 0.523 mmol/L and 100.79 ± 6.65 mmol/L respectively analyzed by ABG analyzer. The mean levels of sodium, potassium and chloride were 136.65 ± 5.81mmol/L, 88 ± 0.543 mmol/L and 100.47 ± 6.41 mmol/L respectively analyzed by ABA. Student’s t test comparison p values for sodium, potassium and chloride were 0.458 (Not Significant), 0.1867 (Not Significant) and 0.0438 (Significant) between the two instruments. The strength of agreement between the two instruments for sodium, potassium and chloride were analyzed using pearsons correlation coefficient. There was strong agreement for all the three parameters between the two instruments and the p value was 0.00001 (highly significant) for all the three parameters.The results of this investigation showed no discernible differences between the automated biochemistry analyzer and arterial blood gas analyzer measurements of sodium, potassium, and chloride. Clinicians can make critically important decisions by relying on the results of arterial blood gas analysis.

ObjectiveTo investigate whether benchtop auto-analyzers (AAs) and arterial blood gas (ABG) analyzers, for measuring electrolyte levels of patients admitted to intensive care units (ICU), are equal and whether they can be used interchangeably.Materials and methodThis study was conducted on 98 patients admitted to the ICU of the Institute of Medicine, Kathmandu, Nepal between 15 October and 15 December 2016. The sample for AA was collected from the peripheral vein through venipuncture, and that for ABG analyzer was collected from radial artery simultaneously. Electrolyte levels were measured with ABG analyzer in the ICU itself, and with benchtop AA in the central clinical biochemistry laboratory.ResultsThe mean value for sodium by AA was 144.6 (standard deviation [SD] 7.63) and by ABG analyzer 140.1 (SD 7.58), which was significant (p-value <0.001). The mean value for potassium by AA was 3.6 (SD 0.52) and by ABG analyzer 3.58 (SD 0.66). The Bland-Altman analysis with the 95% limit of agreement between methods were −4.45 to 13.11 mmol/L for sodium and the mean difference was 4.3 mmol/L and −1.15 to 1.24 mmol/L for potassium and the mean difference was 0.04 mmol/L. The United States Clinical Laboratory Improvement Amendments accepts a 0.5 mmol/L difference in measured potassium levels and a 4 mmol/L difference in measured sodium levels, in the gold standard measure of the standard calibration solution. The passing and Bablok regression with 95% confidence interval has an intercept of zero and slope one for both sodium and potassium, and the 95% of random difference is −6.32 to 6.32 for sodium and −0.84 to 0.84 for potassium, showing no significant deviation from linearity.ConclusionIt can be concluded that AA and ABG analyzers may be used interchangeably for measurement of potassium in the Institute of Medicine, while the same cannot be concluded for the measurement of sodium, because of the significant difference in sodium measurement by the two instruments.

BackgroundElectrolyte values are measured both by arterial blood gas (ABG) analyzers and central laboratory auto-analyzers (AA), but a significant time gap exists between the availability of both these results, with the ABG giving faster results than the AA. The authors hypothesized that there is no difference between the results obtained after measurement of electrolytes by the blood gas and auto-analyzers.MethodsAfter approval by the ethics committee, an observational cohort study was conducted in which 200 paired venous and arterial samples from patients admitted to the Medical Intensive Care Unit (ICU) of Apollo Hospital, Hyderabad, India, were analyzed for electrolytes on the ABG machine and the AA. Analyses were done on the ABL555 blood gas analyzer and the Dade Dimension RxL Max, both located in the central laboratory. Statistical analyses were performed using paired Student’s t test.ResultsA total of 200 paired samples were analyzed. The mean ABG sodium value was 131.28 (SD 7.33), and the mean AA sodium value was 136.45 (SD 6.50) (p < 0.001). The mean ABG potassium value was 3.74 (SD 1.92), and the mean AA potassium value was 3.896 (SD 1.848) (p = 0.2679).ConclusionBased on the above analysis, the authors found no significant difference between the potassium values measured by the blood gas machine and the auto-analyzer. However, the difference between the measured sodium was found to be significant. We therefore conclude that critical decisions can be made by trusting the potassium values obtained from the arterial blood gas analysis.

Background:Accuracy of hemoglobin (Hb) measured by arterial blood gas (ABG) analyzer is considered inferior to laboratory (lab) measurements as it could overestimate Hb levels.Aim of the Study:The study aims to compare Hb measured using ABG versus conventional lab method at the time of major blood loss and in the preoperative and immediate postoperative periods.Settings and Design:It was a prospective, nonrandomized observational study conducted in a tertiary care center.Materials and Methods:The study was conducted in 24 patients undergoing major head-and-neck surgeries. Simultaneous blood samples were sent for Hb measurement by ABG analysis and lab method at induction of anesthesia, when intraoperative blood loss exceeded maximum allowable blood loss, and in the immediate postoperative period.Statistical Analysis Used:Chi-square test, independent sample's t-test, and paired t-test were used for statistical analysis.Results:Mean Hb values obtained by both techniques were significantly different at all time points. Hb obtained by ABG analysis was significantly higher than lab value preoperatively (12.78 ± 2.51 vs. 12.05 ± 2.2, P = 0.038), at maximum blood loss (11.00 ± 2.57 vs. 9.87 ± 2.06, P = 0.006), and in the immediate postoperative period (11.96 ± 2.00 vs. 10.96 ± 2.24 P < 0.001). ABG Hb values were found to be approximately 1 g.dL−1 greater than lab values.Conclusion:Hb measured by ABG analysis was significantly higher than that measured by lab method at the time of major blood loss, preoperatively, and at the immediate postoperative period in patients undergoing major head-and-neck surgeries, with a good correlation of values obtained by both the techniques.

In a critically ill patient, when an arterial blood sample is processed on an arterial blood gas (ABG) analyzer, it also measures electrolytes apart from analyzing the blood gases. The turnaround time for ABG analysis is way too less compared to the conventional electrolyte analysis with a serum sample. This study intends to investigate whether values of electrolytes estimated in arterial blood can substitute the routinely practiced method. This is a retrospective cross-sectional study. The source of data is patients' reports of serum electrolytes and ABG analysis from the Clinical Biochemistry laboratory, CIMS Teaching Hospital, Chamarajanagar between January and June 2021. The electrolytes report of 200 patients from whom both arterial and venous blood samples were sent to the Clinical Biochemistry laboratory on the same day and at the same time for analysis were selected. The data was compiled, compared, and correlated using a suitable statistical tool. The mean and standard deviation of sodium (135.62 ± 5.20 in venous vs 134.08 ± 8.49 in arterial blood), potassium (4.20 ± 0.64 vs 3.80 ± 0.75), and chloride (102.28 ± 4.99 vs 96.33 ± 8.11) were observed. However, when the concordance correlation coefficient and Bland-Altman plot analysis were made there was no agreement between electrolytes analyzed on serum in an autoanalyzer with that of ABG analyzer. We conclude that the electrolytes measured by a conventional autoanalyzer on a serum sample cannot be replaced by values analyzed on a blood gas analyzer. Devaki RN, Kasargod P, Roopa Urs AN, Chandrika N. A Retrospective Database Analysis to Investigate if Electrolytes in Venous Blood are Equivalent to the Levels in Arterial Blood. Indian J Crit Care Med 2024;28(5):442-446.

Background: Electrolytes imbalances can lead to critical life threatening events so immediate and accurate assessmentis needed. There is always a time delay in receiving results from the central laboratory auto analyzer (AA). To overcomethis drawback, arterial blood gas (ABG) analyzer can be used as an alternative to measure electrolytes where resultscan be obtained within two minutes, allowing for prompt management. Methods: This cross-sectional study was carried out on 384 intensive care unit (ICU) patients of Bangladesh Instituteof Research and Rehabilitation in Diabetes, Endocrine and Metabolic disorders (BIRDEM) General Hospital. Theaverage values of sodium and potassium in ABG analyzer and laboratory AA were calculated and then the meandifference or bias was obtained of sodium and potassium measurements analyzed by the two methods. Bland-Altmanplot and Lin’s concordance correlation coefficient (ρc) was used to measure the agreement between the two methods.Test results were considered reliable, if the bias was non-significant and within the United States Clinical LaboratoryImprovement Amendment (US CLIA) criteria (±4 mmol/l for sodium and ±0.5 mmol/l for potassium), 95% limits ofagreement (LOA) were narrow and ρc showed good concordance. Results: The mean difference or bias, 95% LOA and ρc for sodium was -1.2 mmol/l, -11 mmol/l to 8.6 mmol/l and 0.85respectively whereas for potassium this was 0.8 mmol/l, -0.39 to 1.98 mmol/l and 0.63 respectively. The bias for sodiumwas within the US CLIA criteria but not so for potassium. However, the 95% LOA was wide and there was poorconcordance for both the measurement. On account of these differences, correction factor was calculated for sodiumand potassium values. Serum sodium (in mmol/l) was 2.48 + 0.97 x ABG sodium (in mmol/l) and serum potassium (inmmol/l) was 1.18 + 0.89 x ABG potassium (in mmol/l). Conclusion: The sodium and potassium measurements obtained from the ABG analyzer was found to be unreliable.However, a correction factor to the ABG analyzer results could be applied to initiate treatment and then changing themanagement, if required, once laboratory AA reports become available. Bangladesh Crit Care J March 2023; 11 (1): 3-8

Objective To explore the accuracy of bedside arterial blood gas analyzer in detecting electrolytes and anionic gap (AG) in ICU patients, and compare it with auto-analyzer. Methods Results of blood sodium, potassium, chlorine, bicarbonate ions and AG measured by arterial blood gas analyzer and auto-analyzer of 376 ICU adult patients admitted to ICU were retrospectively analyzed. With the outcomes of auto-analyzer as standard, the correlation and difference of electrolytes and AG measured by 2 methods were analyzed. Results The sodium, potassium, chlorine and AG measured by auto-analyzer were 121 -183 mmol/L, 2.13 -6.77 mmol/L, 86 -146 mmol/L and 1 -62 mmol/L. The blood sodium, potassium, chlorine and AG measured by arterial blood gas analyzer were 114 -180 mmol/L, 1.78 -6.36 mmol/L, 94 -150 mmol/L, -7 -40 mmol/L. The blood sodium, potassium and AG measured by arterial blood gas analyzer were lower than those measured by auto-analyzer, but the blood chlorine was higher than that measured by auto-analyzer. There were statistical differences in the difference of low, normal and high electrolytes and AG between 2 methods (P <0.01). Conclusions The electrolytes and AG measured by arterial blood gas analyzer and auto-analyzer are significantly different, and the electrolytes measured by arterial blood gas analyzer are unreliable to calculate AG. Key words: Blood gas analysis; Electrolytes; Anions; Intensive care units; Retrospective studies

The study aims to assess the accuracy of the arterial blood gas (ABG) analysis in measuring hemoglobin, potassium, sodium, and glucose concentrations in comparison to standard venous blood analysis among patients diagnosed with chronic obstructive pulmonary disease (COPD). From January to March 2023, results of ABG analysis and simultaneous venous blood sampling among patients with COPD were retrospectively compared, without any intervention being applied between the two methods. The differences in hemoglobin, potassium, sodium, and glucose concentrations were assessed using a statistical software program (R software). There were significant differences in the mean concentrations of hemoglobin (p < 0.001), potassium (p < 0.001), and sodium (p = 0.001) between the results from ABG and standard venous blood analysis. However, the magnitude of the difference was within the total error allowance (TEa) of the United States of Clinical Laboratory Improvement Amendments (US-CLIA). As for the innovatively studied glucose concentrations, a statistically significant difference between the results obtained from ABG (7.8 ± 3.00) mmol·L−1 and venous blood (6.72 ± 2.44) mmol·L−1 was noted (p < 0.001), with the difference exceeding the TEa of US-CLIA. A linear relationship between venous blood glucose and ABG was obtained: venous blood glucose (mmol·L−1) = − 0.487 + 0.923 × ABG glucose (mmol·L−1), with R2 of 0.882. The hemoglobin, potassium, and sodium concentrations in ABG were reliable for guiding treatment in managing COPD emergencies. However, the ABG analysis of glucose was significantly higher as compared to venous blood glucose, and there was a positive correlation between the two methods. Thus, a linear regression equation in this study combined with ABG analysis could be helpful in quickly estimating venous blood glucose during COPD emergency treatment before the standard venous blood glucose was available from the medical laboratory.

IntroductionGlucose control to prevent both hyperglycemia and hypoglycemia is important in an intensive care unit. Arterial blood gas analyzers and glucose meters are commonly used to measure blood-glucose concentration in an intensive care unit; however, their accuracies are still unclear.MethodsWe performed a systematic literature search (January 1, 2001, to August 31, 2012) to find clinical studies comparing blood-glucose values measured with glucose meters and/or arterial blood gas analyzers with those simultaneously measured with a central laboratory machine in critically ill adult patients.ResultsWe reviewed 879 articles and found 21 studies in which the accuracy of blood-glucose monitoring by arterial blood gas analyzers and/or glucometers by using central laboratory methods as references was assessed in critically ill adult patients. Of those 21 studies, 11 studies in which International Organization for Standardization criteria, error-grid method, or percentage of values within 20% of the error of a reference were used were selected for evaluation. The accuracy of blood-glucose measurements by arterial blood gas analyzers and glucose meters by using arterial blood was significantly higher than that of measurements with glucose meters by using capillary blood (odds ratios for error: 0.04, P < 0.001; and 0.36, P < 0.001). The accuracy of blood-glucose measurements with arterial blood gas analyzers tended to be higher than that of measurements with glucose meters by using arterial blood (P = 0.20). In the hypoglycemic range (defined as < 81 mg/dl), the incidence of errors using these devices was higher than that in the nonhypoglycemic range (odds ratios for error: arterial blood gas analyzers, 1.86, P = 0.15; glucose meters with capillary blood, 1.84, P = 0.03; glucose meters with arterial blood, 2.33, P = 0.02). Unstable hemodynamics (edema and use of a vasopressor) and use of insulin were associated with increased error of blood glucose monitoring with glucose meters.ConclusionsOur literature review showed that the accuracy of blood-glucose measurements with arterial blood gas analyzers was significantly higher than that of measurements with glucose meters by using capillary blood and tended to be higher than that of measurements with glucose meters by using arterial blood. These results should be interpreted with caution because of the large variation of accuracy among devices. Because blood-glucose monitoring was less accurate within or near the hypoglycemic range, especially in patients with unstable hemodynamics or receiving insulin infusion, we should be aware that current blood glucose-monitoring technology has not reached a high enough degree of accuracy and reliability to lead to appropriate glucose control in critically ill patients.

Effect of intravenous vitamin C on arterial blood gas analyser and Accu-Chek point-of-care glucose monitoring in critically ill patients

Introduction: The Emergency Departments (ED) are equipped with Point-of-Care (POC) blood gas analysers (BGA) which deliver fast results on multiple parameters of arterial/venous blood. There is no consensus among ED physicians on the reliability of electrolyte results by POC Arterial Blood Gas (ABG) analysis compared to venous serum electrolyte from Central Laboratory Analyser/Auto-Analyser (CLA/AA). Aim: To compare the electrolyte(sodium and potassium) by POC arterial BGA (ABL800 Flex Radiometer) with venous electrolyte by CLA (Beckman Coulter AU 5800). Materials and Methods: This cross-sectional study was performed in the ED and Central Laboratory of the tertiary hospital from 1st July 2018 to 31st July 2019. A total of 254 critically ill adult patients with various etiologies, were enrolled in the study. The arterial and venous blood samples were collected for electrolyte measurement within a span of 15 minutes. The ABG samples, anticoagulated with liquid heparin, were processed in POC BGA. The venous samples collected in plain tubes were analysed in CLA. The results of sodium and potassium were compared by the mean, correlation coefficient, p-value, and Bland Altman Plots {95% Limit of agreement (LOA)}. Results: Out of 254 paired samples (mean age: 63±15 years), 157 (61.8%) were males and 97 (38.2%) females. The mean sodium values were 131.9±7.7 mmol/L in ABG and 132.3±7.1 mmol/L in CLA (p-value &lt;0.0001). The mean difference was 0.4 mmol/L. The mean potassium values were 3.9±1.0 mmol/L (ABG) and 4.2±0.9 mmol/L (CLA), {p-value&lt;0.0001}. The mean difference was 0.3 mmol/L. These differences were within the accepted range specified by the United States Clinical Laboratory Improvement Amendments. There were statistically significant strong positive correlations between the measurements of the two instruments r=0.78 for sodium and r=0.76 for potassium. The 95% LOA for sodium and potassium on both the instruments were -10.03 to 9.09 mmol/L and -1.49 to 0.97 mmol/L respectively, both wide and unacceptable. Conclusion: The arterial sodium and potassium measurements by BGA were not reliable in decision making in ED when compared to the venous serum by CLA as the 95% LOA was wide and unacceptable. Hence, sodium and potassium values by BGA alone might not be used as criteria for management without confirmation from venous serum values by CLA.

ARTERIAL VS SERUM LACTIC ACID DISCREPANCY

Oxygen saturation is essential for medical care and is closely regulated within the body. Arterial blood gas (ABG) analysis is used to evaluate critically ill individuals' ventilation, oxygenation, acid-base status, and metabolic condition. Pulse oximetry is an easy and non-invasive way to measure the status of oxygen saturation non-invasively in clinical settings and provides a quick and precise assessment of oxygenation and reduces medical errors. SpO2 may not always be a reliable predictor of arterial oxygen saturation (SaO2), and hypoxemic, hemodynamically compromised, and critically ill patients may have lower SpO2 accuracy. A study is needed to assess and compare various oxygen saturation methods. The study aimed to compare the oxygen saturation levels measured by pulse oximetry and ABG analysis in hypoxemic patients. The objectives were tocompare the values between SaO2, PaO2, and SpO2 values obtained from the patients, and correlate the study parameters among both techniques. The study was conducted from February 2021 to June 2022 among the 102 hypoxemic patients who were admitted to the emergency and surgical intensive care unit (ICU) of Sree Balaji Medical College and Hospital in Chennai. Primary data on ABGanalysis and pulse oximetry readings were collected from the study subjects. The patient and their past medical records, physical exam, chest x-ray findings, pulse oximetry, and ABG results were all reviewed. Each patient had their ABG, and pulse oximetry measured simultaneously. A comparison was made between SpO2 and partial pressure of oxygen (PaO2) and arterial oxygen saturation (SaO2) parameters using a paired t-test. The correlation was done against the SpO2 and ABG parameters and assessed for association using the correlation coefficient value; gender was also considered while correlating. An observational study was done among 102 study samples to comparatively analyze the oxygen saturation by two methods, namely pulse oximetry and ABG, in hypoxemic patients. While comparing the mean values of SaO2 and SpO2, they were 84.41 ± 4.24 and 80.58 ± 5.77, respectively, and this difference was statistically very significant (p< 0.001). While comparing the mean values of PaO2 and SaO2, they were 61.02 ± 5.01 and 84.41 ± 4.24, respectively, and this difference was statistically significant (p = 0.043). While comparing the mean values of PaO2 and SpO2, they were 61.02 ± 5.01 and 80.58 ± 5.77, respectively, and this difference was statistically significant (p = 0.054). Among the study population, with regard to the correlation factor, there is notably a very high and strong positive correlation between SaO2 and SpO2 and between SpO2 and PaO2. There was a negative correlation between SpO2 and finger abnormalities and between SpO2 and blood pressure. The ABGmethod is considered the gold standard. When SpO2 levels fall below 90%, pulse oximetry may not be accurate enough to reliably assess oxygenation. In such cases, where alveolar hypoventilation is suspected, it is recommended to complement pulse oximetry with ABG studies. This is because ABG analysis provides a more comprehensive assessment of oxygenation and acid-base status, which can aid in the diagnosis and management of respiratory conditions.

BackgroundElectrolyte values are measured in most critically ill intensive care unit (ICU) patients using both an arterial blood gas analyzer (ABG) and a central laboratory auto-analyzer (AA). The aim of the present study was to investigate whether electrolyte levels assessed using an ABG and an AA were equivalent; data on sodium and potassium ion concentrations were examined.MethodsWe retrospectively studied patients hospitalized in the ICU between July and August 2011. Of 1,105 test samples, we identified 84 instances of simultaneous sampling of arterial and venous blood, where both Na+ and K+ levels were measured using a pHOx Stat Profile Plus L blood gas analyzer (Nova Biomedical, Waltham MA, USA) and a Roche Modular P autoanalyzer (Roche Diagnostics, Mannheim, Germany). Statistical measures employed to compare the data included Spearman's correlation coefficients, paired Student’s t-tests, Deming regression analysis, and Bland-Altman plots.ResultsThe mean sodium concentration was 138.1 mmol/L (SD 10.2 mmol/L) using the ABG and 143.0 mmol/L (SD 10.5) using the AA (p < 0.001). The mean potassium level was 3.5 mmol/L (SD 0.9 mmol/L) using the ABG and 3.7 mmol/L (SD 1.0 mmol/L) using the AA (p < 0.001). The extent of inter-analyzer agreement was unacceptable for both K+ and Na+, with biases of 0.150-0.352 and −0.97-10.05 respectively; the associated correlation coefficients were 0.88 and 0.90.ConclusionsWe conclude that the ABG and AA do not yield equivalent Na+ and K+ data. Concordance between ABG and AA should be established prior to introduction of new ABG systems.