Haematocrit measurements during cardiopulmonary bypass surgery: comparison of three stat methods with a blood cell counter

Abstract

Monitoring packed cell volume (PCV) is essential to safeguard oxygen delivery to the tissues during cardiopulmonary bypass (CPB). We compared the results obtained using a PCV monitor, a blood gas analyser and a microcentrifuge with those from a laboratory-based automated blood cell counter. PCV was measured in 221 samples of 40 patients undergoing open-heart surgery. The limits of agreement (mean difference +/- 2 SD) was unacceptably wide when the results obtained with the PCV monitor and the blood gas analyser were compared with those of the automated blood cell counter. This was most pronounced when PCV was measured in low concentration samples. The microcentrifuge showed good limits of agreement regardless of sample concentration. The data suggests that measurement of PCV by either continuous monitoring or by a blood gas analyser is not an accurate alternative to an established laboratory method. The microcentrifuge is the most accurate method of the ones investigated to measure haematocrit during CPB.

Reliability of point-of-care hematocrit, blood gas, electrolyte, lactate and glucose measurement during cardiopulmonary bypass

“…In addition, it should be pointed out that the Sysmex, which measures hematocrit via a pulsometric method, is not a golden standard for hematocrit measurement. The micro-centrifugal method is commonly accepted for this, 18,19 although it should be noted that hemodilution may also alter the viscosity and volume of packed red cells. 20 Undoubtedly, the Sysmex will have some bias with respect to the golden standard, but the magnitude of the bias of the GEM in comparison with the Sysmex suggests that the GEM will still have a substantial bias with respect to microcentrifugal hematocrit.…”

Where are we at with point‐ of‐ care testing in haematology?

“…As these dynamic changes are likely to occur during surgery or ICU, the conductivity‐based POCT results should be interpreted with caution in these circumstances (McMahon & Carpenter, ; Stott et al , ; McNulty et al , ; Hopfer et al , ; Stadlbauer et al , ). A downward bias has been demonstrated when the Hct is below 30% (al‐Odeh et al , ). In one study, for example, the use of arterial blood‐gas POCT (GEM Premier 3000) in patients undergoing cardio‐pulmonary bypass surgery could have resulted in over‐transfusion of more than two‐thirds of the 55 patients who had participated in the study (Steinfelder‐Visscher et al , ).…”

Investigation of Noninvasive in vivo Blood Hematocrit Measurement Using NIR Reflectance Spectroscopy and Partial Least-Squares Regression

“…It is reported that the accuracy of a continuous on-line monitor reads hematocrit between 3.7% lower and 6.2% higher than the standard blood cell counter method and always reads higher for diluted samples with the difference as high as 7.5%. 5 Laboratory studies indicate that hematocrit m easured by the ratio of two spectral intensities is affected by the blood oxygenation level. 6 The spectral intensities are also dependent upon temperature variations that occur during cardiac surgical procedures.…”