The rise and fall of i-STAT point-of-care blood gas testing in an acute care hospital

Effect of Serum on Electrochemical Detection of Bioassays Having Ag Nanoparticle Labels

The effect of serum on electrochemical detection of bioassays having silver nanoparticle (AgNP) detection labels was investigated. Both a model assay and an antigen-specific sandwich bioassay for the heart failure marker NT-proBNP were examined. In both cases, the AgNP labels were conjugated to a detection antibody. Electrochemical detection was carried out using a galvanic exchange/anodic stripping voltammetry method in which Au3+ exchanges with AgNP labels. The assays were carried out using a paper-based electrode platform. The bioassays were exposed to different serum conditions prior to and during detection. There are three important outcomes reported in this article. First, both the model- and antigen-specific assays could be formed in undiluted serum with no detectable interferences from the serum components. Second, to achieve the maximum possible electrochemical signal, the highest percentage of serum that can remain in an assay buffer during electrochemical detection is 0.25% when no washing is performed. The assay results are rendered inaccurate when 0.50% or more of serum is present. Third, the factors inhibiting galvanic exchange in serum probably relate to surface adsorption of biomolecules onto the AgNP labels, chelation of Au3+ by serum components, or both. The results reported here provide general guidance for using metal NP labels for electrochemical assays in biofluids.

Assessing Performance of i-STAT at the Point of Care in the Emergency Room

Context:

Point-of-care testing (POCT) for blood gas and chemistries is widely adopted in the emergency department (ED) for fast turnaround and critical medical decisions.

Objective:

To assess performance of ED physicians compared to laboratory technologists carrying out i-STAT analysis. Impact of user skill on POCT performance was also studied.

Design:

Over a 3-month period, ED physicians performed tests with their i-STAT unit with parallel blood specimens (n=60) sent to the central laboratory to be tested on another i-STAT unit and laboratory analysers (blood gas and chemistries). Comparisons to laboratory results (obtained with ABL 520 and Beckman-Coulter LX20PRO) were carried out. Two operators from ED and central laboratory performed side by side, repeated tests on the i-STAT units. Their overall within-run imprecision were compared. The analytical performance of i-STAT was further assessed by another laboratory technologist to verify its capability to deliver good results.

Results:

Platform comparisons showed that ED physicians performed poorer compared to laboratory technologists, particularly with chloride and pO2 (Spearman coefficient of correlation — 0.49 and 0.54 respectively indicate wide scatter). This is also mirrored in the higher overall within-run imprecision for chemistries (sodium, chloride, potassium, glucose, urea and creatinine) by an ED physician (5.4%) compared to a laboratory technologist (3.7%). Including blood gas results showed an even wider gap in their testing skills. Except at a low creatinine of 67 μmol/L, the i-STAT analyser delivered precise measurements for the chemistries and blood gas parameters.

Conclusions:

Performances by medical staff with the i-STAT analyser did not adequately approach the same skill level as laboratory technologists.

Point-of-care blood analyzer during the interhospital transport of critically ill children

OBJECTIVES

To investigate the influence of point-of-care laboratory results (arterial blood gases, ionized calcium, potassium, sodium, glucose, hematocrit and hemoglobin) on therapeutic interventions during interhospital pediatric intensive care transport.

DESIGN

Prospective observational study.

SETTINGS

Specialist pediatric intensive care retrieval team of a university hospital.

PARTICIPANTS

Critically ill pediatric patients who were referred from a community hospital to a pediatric intensive care of a tertiary center. The retrieval team sampled arterial blood during the time of stabilization in the referring hospital and during transport. All results were recorded and for each result the physician of the specialist retrieval team wrote down the influence on the treatment (none, partly, only). The physician specified the kind of intervention.

RESULTS

Point-of-care blood analyses influenced the therapeutic management in 76.5% of all blood samples and in 86.2% of the referred patients. Of all interventions, 42.9% were based only on the laboratory results. The majority of interventions were adjustments of the mechanical ventilation. Point-of-care blood analyses reduced the delay in treatment of potentially life-threatening abnormalities of laboratory results (severe hypokalemia and low hematocrit).

CONCLUSIONS

During interhospital pediatric intensive care transport, point-of-care blood analyses frequently led to therapeutic interventions. Some abnormal blood results were potentially life threatening and could not have been discovered without point-of-care measurement. We therefore recommend the use of a point-of-care blood analyzer during interhospital intensive care transports, not only for blood gases but also for electrolytes, glucose and hematocrit.

Effects of duration of capture and sample handling on critical care blood analytes in free-ranging bottlenose dolphins

OBJECTIVE

To determine effects of duration of capture and sample-handling procedures on blood analytes in free-ranging bottlenose dolphins.

DESIGN

Cross-sectional study.

ANIMALS

154 free-ranging bottlenose dolphins of various ages and both sexes.

PROCEDURES

Blood samples were drawn from each dolphin within 10 minutes of capture and before release and analyzed by use of a portable analyzer with a single-use 8-analyte disposable cartridge. Analyte values were compared according to duration between sample acquisition and analysis (time to run [TTR]) and duration between net encirclement and sample acquisition (time to bleed [TTB]).

RESULTS

Neither TTB nor TTR significantly affected sodium or chloride concentration. Potassium concentration was not significantly affected by TTR, whereas the effect of TTB was significant. Glucose, total CO(2), HCO(3), Hct, and base excess of extracellular fluid values were significantly affected by TTR. Increased TTB resulted in significantly increased total CO(2), HCO(3), and base excess when TTR was kept within 10 minutes.

CONCLUSIONS AND CLINICAL RELEVANCE

The effect of TTB on certain acid-base and electrolyte values was readily measured in free-ranging bottlenose dolphins, and such values may provide a reference range for those variables.

The accuracy of the i-STAT portable analyser for measuring blood gases and pH in whole-blood samples from dogs

To assess the suitability of the i-STAT portable analyser for use by non-laboratory personnel, we measured blood gases and pH in venous blood samples from 100 dogs. Deming's regression and bias plots were used to compare i-STAT results with those obtained by laboratory professionals using two different autocalibrated benchtop analysers. Overall accuracy of the portable analyser proved excellent for pH, pO(2), and pCO(2) (r=0.978, 0.968 and 0.997, respectively), with Deming's regression slopes close to 1.00 (0.96, 0.97 and 1.08 for pH, pO(2), and pCO(2), respectively) and intercepts close to zero (0.28, 0.47 kPa and 0.46 kPa for pH, pO(2), and pCO(2), respectively). The accuracy of the i-STAT was also satisfactory for calculated parameters: bicarbonates, total CO(2), base excess and oxygen saturation. Our findings show this portable analyser to be a valid substitute for expensive benchtop analysers in situations requiring mobility, or when small numbers of tests are to be performed by users not specialized in laboratory techniques.