Point of care hematocrit and hemoglobin in cardiac surgery: a review
Bibliographic record
Abstract
The use of point-of-care blood gas analyzers in cardiac surgery has been on the increase over the past decade. The availability of these analyzers in the operating room and post-operative intensive care units eliminates the time delays to transport samples to the main laboratory and reduces the amount of blood sampled to measure such parameters as electrolytes, blood gases, lactates, glucose and hemoglobin/hematocrit. Point-of-care analyzers also lead to faster and more reliable clinical decisions while the patient is still on the heart lung machine. Point-of-care devices were designed to provide safe, appropriate and consistent care of those patients in need of rapid acid/base balance and electrolyte management in the clinical setting. As a result, clinicians rely on their values to make decisions regarding ventilation, acid/base management, transfusion and glucose management. Therefore, accuracy and reliability are an absolute must for these bedside analyzers in both the cardiac operating room and the post-op intensive care units. Clinicians have a choice of two types of technology to measure hemoglobin/hematocrit during bypass, which subsequently determines their patient's level of hemodilution, as well as their transfusion threshold. All modern point-of-care blood gas analyzers measure hematocrit using a technology called conductivity, while other similar devices measure hemoglobin using a technology called co-oximetry. The two methods are analyzed and compared in this review. The literature indicates that using conductivity to measure hematocrit during and after cardiac surgery could produce inaccurate results when hematocrits are less than 30%, and, therefore, result in unnecessary homologous red cell transfusions in some patients. These inaccuracies are influenced by several factors that are common and unique to cardiopulmonary bypass, and will also be reviewed here. It appears that the only accurate, consistent and reliable method to determine hemodilution and establish transfusion thresholds based on nadir hematocrits during cardiopulmonary bypass, and immediately post cardiac surgery, is with the use of co-oximetry.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.006 | 0.006 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".