Difference between revisions of "Transfusion thresholds"
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(Created page with "Find a better trigger for transfusion threshold. Hgb mass loss vs. qBL vs. EBL are all various ways of getting at how much blood was lost, but why do we even care? Is that eve...") |
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Find a better trigger for transfusion threshold. Hgb mass loss vs. qBL vs. EBL are all various ways of getting at how much blood was lost, but why do we even care? Is that even useful information? How much Hgb do you need? Is Hgb concentration even the right thing to measure for a transfusion threshold? What you really want to know is whether they lost so much blood that they require a transfusion to provide adequate tissue oxygenation. Are there other reasons to care? Is there an early marker of tissue hypoxia that would make a better laboratory marker for determining need for blood transfusion? | Find a better trigger for transfusion threshold. Hgb mass loss vs. qBL vs. EBL are all various ways of getting at how much blood was lost, but why do we even care? Is that even useful information? How much Hgb do you need? Is Hgb concentration even the right thing to measure for a transfusion threshold? What you really want to know is whether they lost so much blood that they require a transfusion to provide adequate tissue oxygenation. Are there other reasons to care? Is there an early marker of tissue hypoxia that would make a better laboratory marker for determining need for blood transfusion? | ||
| − | + | * Hgb mass loss (HML) takes the concentration of Hgb in the suction canister (including irrigation) and multiplies it by the volume to yield the total hemoglobin mass in the canister. This could then be divided by the starting Hgb concentration to determine the volume of blood lost. | |
| − | + | * Assuming the blood is lost acutely, there initially should be no change in the Hgb concentration. Over a sub-acute time frame two dilutional factors kick in, volume resuscitation with crystalloid and fluid shifts from the interstitial to the intravascular compartment. | |
| − | + | * Assuming 100% stayed intravascular and there were no fluid shifts between compartments to compensate, could you predict the new Hgb concentration after fluid administration based on how much volume was given? Probably not, given that you know C1 but not V1, and you are trying to solve for C2 but don't know V2. You do know the volume lost and the volume given back with concentration of 0, but I'm not sure if that is helpful. Assuming a standard blood volume based on patient averages may not be accurate because patients will come to surgery with unpredictable confounders like bleeding/dehydration. The starting blood volume could be measured (e.g. with nuclear medicine assay), but even then you won't know how much of the resuscitation fluid will stay intravascular or how much fluid is shifting between compartments. If you knew the starting blood volume, you could at least say what fraction of total Hgb was lost. | |
Latest revision as of 23:03, 5 August 2024
Find a better trigger for transfusion threshold. Hgb mass loss vs. qBL vs. EBL are all various ways of getting at how much blood was lost, but why do we even care? Is that even useful information? How much Hgb do you need? Is Hgb concentration even the right thing to measure for a transfusion threshold? What you really want to know is whether they lost so much blood that they require a transfusion to provide adequate tissue oxygenation. Are there other reasons to care? Is there an early marker of tissue hypoxia that would make a better laboratory marker for determining need for blood transfusion?
- Hgb mass loss (HML) takes the concentration of Hgb in the suction canister (including irrigation) and multiplies it by the volume to yield the total hemoglobin mass in the canister. This could then be divided by the starting Hgb concentration to determine the volume of blood lost.
- Assuming the blood is lost acutely, there initially should be no change in the Hgb concentration. Over a sub-acute time frame two dilutional factors kick in, volume resuscitation with crystalloid and fluid shifts from the interstitial to the intravascular compartment.
- Assuming 100% stayed intravascular and there were no fluid shifts between compartments to compensate, could you predict the new Hgb concentration after fluid administration based on how much volume was given? Probably not, given that you know C1 but not V1, and you are trying to solve for C2 but don't know V2. You do know the volume lost and the volume given back with concentration of 0, but I'm not sure if that is helpful. Assuming a standard blood volume based on patient averages may not be accurate because patients will come to surgery with unpredictable confounders like bleeding/dehydration. The starting blood volume could be measured (e.g. with nuclear medicine assay), but even then you won't know how much of the resuscitation fluid will stay intravascular or how much fluid is shifting between compartments. If you knew the starting blood volume, you could at least say what fraction of total Hgb was lost.