The GEM Premier 3000 analyser seems to be suitable for point-of-care testing of electrolytes, metabolites, and blood gases during cardiopulmonary bypass. However, its downward bias in hematocrit values below 30% suggests that using the GEM Premier 3000 as a transfusion trigger leads to overtreatment with packed red cells.

Conductivity-based POC hematocrit measurement suffers from biases due to changes of the plasma constituents. The downward bias in hematocrit as often seen during cardiopulmonary bypass is driven by changes of different electrolyte concentration rather than by colloids used per se.

Background: Deep sternal wound problems (DSWP) are a rare, but serious complication following cardiac surgery requiring extensive medical treatment and resulting in increased mortality. Cardiac surgery patients presenting with both obesity and diabetes mellitus type 2 (DM 2) showed an increased incidence of DSWP in our clinic. As platelets upon activation have been shown to excrete growth factors and attractants for tissue stem cells, thus potentially promoting tissue healing, we investigated whether activated platelets could reduce the incidence of DSWP. Methods: We applied activated autologous platelet rich plasma (PRP), forming a gel (PLG), between the sternal halves immediately prior to closure in obese [body mass index (BMI) >30] DM 2 cardiac surgery patients. The reference group constituted of all elective patients with a BMI >30 and DM 2 operated upon in the 2-year period before the application of PLG. Results: The PLG treated group (n=144) showed a significant decrease in DSWP compared to the reference group (n=118), 6 DSWP vs. 13 DSWP respectively, P=0.03. In these groups the application of PLG was associated with a risk reduction for DSWP from 11% to 4.2%. Conclusions: These results suggest PLG application could be beneficial to prevent DSWP following cardiac surgery in a high-risk population.

Most point-of-care testing analyzers use the conductivity method to measure hematocrit (hct). During open-heart surgery, blood-conductivity is influenced by shifts in electrolyte and colloid concentrations caused by infusion media used, and this may lead to considerable bias in the hct measurement. We evaluated to what extent different analyzers correcting for 0, 1, 2, or 3 factors, respectively, compensated for this electrolyte/colloid interference: (1) the conductivity method with no correction (IRMA), (2) with a [Na(+)]-correction (GEM Premier 3000), (3) with a [Na(+)]/[K(+)]-correction (i-STAT), and (4) with a [Na(+)]/[K(+)]-correction in combination with an algorithm that estimates the protein dilution [i-STAT in cardiopulmonary bypass (CPB)-mode]. Bias in hct was measured during three consecutive stages of a CPB procedure: (I) before CPB, (II) start of CPB and (III) after cardioplegia. In order of high to low electrolyte/colloid interference: the analyzer with no correction, [Na(+)]-correction, [Na(+)/]/[K(+)]-correction, and [Na(+)/]/[K(+)]/estimated protein-correction showed a change of bias from stage I to stage III of -3.9 ± 0.5, -3.4 ± 0.4, -2.1 ± 0.5, -0.3 ± 0.5%. We conclude that correcting for more parameters (Na(+), K(+), estimated protein) gives less bias, but residual bias remains even after [Na(+)/]/[K(+)]/estimated protein-correction. This suggests that a satisfactory algorithm should also correct for other colloidal factors than protein.

Point-of-care analyzers may benefit therapeutic decision making by reducing turn-around-time for samples. This is especially true when biochemical parameters exceed the clinical reference range, in which acute and effective treatment is essential. We therefore evaluated the analytical performance of the i-STAT point-of-care analyzer in two critically ill adult patient populations. During a 3-month period, 48 blood samples from patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) and 42 blood samples from non-cardiac patients who needed intensive care treatment were analyzed on both the i-STAT analyzer (CPB and non-CPB mode, respectively) and our laboratory analyzers (RapidLab 865/Sysmex XE-2100 instrument). The agreement analysis for quantitative data was used to compare i-STAT to RapidLab for blood gas/electrolytes and for hematocrit with the Sysmex instrument. Point-of-care electrolytes and blood gases had constant deviation, except for pH, pO2, and hematocrit. A clear linear trend in deviation of i-STAT from RapidLab was noticed for pH during CPB (r = 0.32, p = .03) and for pO2 > 10 kPa during CPB (r = −0.59, p < .0001 when 10 < pO2 <30 kPa) and in the intensive care unit (r = −0.61, p < .001 when 10 < pO2 <30 kPa). In the normal pO2 range (10.6 < pO2 <13.3 kPa), the performance of the i-STAT was comparable to the RapidLab. In contrast to hematocrit measured during CPB, hematocrit using the non-CPB mode in the non-cardiac intensive care population showed an underestimation up to 2.2% (p < .0001) in the hematocrit range below 25% (n = 11) using the i-STAT. The i-STAT analyzer is suitable for point-of-care testing of electrolytes and blood gases in critically ill patients, except for high pO2. However, the discrepancy in hematocrit bias shows that accuracy established in one patient population cannot be automatically extrapolated to other patient populations, thus stressing the need for separate evaluation.