Istat blood gas instruction manual11/29/2023 ![]() A total of 71.5% of the K+ values obtained on the ABG was lower than the AA. The adjusted r 2 was within a 95% confidence interval of 0.42 to 0.62. The correlation coefficient (r) was 0.72. ![]() The maximum difference in measured potassium value was 2.4 mmol/l, and the minimum difference was 0 mmol/l. There was no significant difference (p = 0.2679, null hypothesis accepted) between K+ measured by the ABG (3.7 mmol/l, SD 1.9) and AA (mean 3.9 mmol/l, SD 1.8). In the group of patients with borderline hyponatremia (serum sodium 120–135 mmol/l) and hyponatremia (serum sodium <120 mmol/l), the mean difference between the two measurements was 7.4 mmol/l and 12.8 mmol/l (p < 0.0001 for both subgroups), effectively making the ABG measurements unreliable.Īnalysis of the potassium values (Table 4) obtained from the AA and the ABG gave a mean difference of 0.46 mmol/l with a standard error of 0.03 mmol/l. However, because of the small sample size (n = 5) in this subgroup, we were underpowered to detect a difference. There was no significant difference in sodium measurements by AA and ABG for patients with hypernatremia (mean difference 3.8 mmol/l p = 0.3847, null hypothesis accepted). However, the mean difference between the two measuring methods was 3.4 mmol/l, which was within the acceptable limit defined in the US CLIA 2006. The 200 paired samples included a venous blood sample for auto-analyzer electrolyte measurement and an arterial blood sample for blood gas analysis.ĭata were collected, and the values of sodium (Na+) and potassium (K+) from these measurements were compared using the paired t-test.Īnalysis of the sodium measurements in the group of patients with normal sodium revealed a significant difference between the two measures (p = 0.005 null hypothesis rejected). Operators drawing and handling blood samples did so with only latex gloves without using any hand disinfectants just prior to handling blood. Time of collection of samples was documented on both sample groups for reference. Both analyzers were calibrated according to the Joint Commission on Accreditation of Hospitals (JCAHO) requirements for hospital certification prior to each measurement cycle. Quality control was ensured by having the blood samples collected by trained staff of a single ICU unit in the hospital and analyzed in the two analyzers located in the central laboratory under similar environmental conditions, unlike in the previous studies where the analyzers were in different environments. Both of these are considered as benchmark top models in their respective technologies. All samples were analyzed on the ABL555 blood gas analyzer and the Dade Dimension RxL Max, both located in the central laboratory. Blood samples were collected simultaneously for ABG and AA for electrolyte analysis. The study period started in August 2005 and ended in May 2006. Paired blood samples from 200 consecutive adult patients admitted to the Medical ICU of Apollo Hospitals were included in the study. The study was designed to be an observational study of a consecutive cohort of patients admitted to the ICU. The study was approved by the ethics committee of Apollo Hospitals, Hyderabad, India. The arterial blood gas (ABG) machines and AA differ in several aspects as listed in Table 1. Electrolytes are also measured during arterial blood gas analysis, but are traditionally rarely trusted for clinical decision-making because of the dearth of published research about the same. The operational cost of iSTAT and other similar equipment is a major deterrent to their utilization in developing systems of health care. Point-of-care testing for electrolytes is available from specialized equipment such as the iSTAT or Stat Profile Critical Care Xpress analyzers. Quick decisions that need to be made depending on electrolyte values hence are often made either blindly or are delayed. Typically, a turnaround time of about 15 min is noted on average in acute care laboratories of most tertiary care hospitals for the above. Routinely, all electrolytes are measured from serum by the auto-analyzers (AA) available in central laboratories of hospitals however, this is time-consuming. Įlectrolyte values are conventionally measured for all critical patients who present to the emergency department, for patients receiving fluid therapy, and for patients admitted to intensive care units (ICU). Point-of-care testing enables clinicians to initiate appropriate treatment for emergent conditions, thereby benefitting the patient both clinically and economically.
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