Hemoglobin level

Is there a standard regarding how much blood loss equals a decrease in hemoglobin by 1 unit?

The average adult blood volume is 70 ml/kg of body weight or 7% of body weight.

This means that a person weighing 70 kg would have an estimated blood volume of 70ml/kg * 70kg =4.900 ml or approximately 5 liters.

If this person has a hemoglobin of 120g/L (or 12.0g/dl for the US nurses) it means that the person has a total of 5L * 120g/L = 600 g hemoglobin.

I don't have a formula for you how to estimate drop in hemoglobin through measuring the blood loss but at least this gives you an approximate idea what would happen if a person lost a for example 1 L of blood and it wasn't replaced. They'd still have 120g/L but obviously a lower total amount of hemoglobin circulating in their body.

One piece of information that might be of interest. One transfused unit of packed red blood cells is expected to increase the hemoglobin concentration by about 10 g/L (or 1g/dl) in a person who's not still actively bleeding.

You can't directly compare/equate the volumes and the increase in hemoglobin through transfusions to the decrease of hemoglobin caused by blood loss. We transfuse RBCs, but that's not all we lose when we bleed.

My guess is that your patient's decreased hemoglobin is due to hemodilution. If a person loses blood during surgery and is given (aggressive) fluid replacement the result can be isovolemic anemia. The blood volume is normal/adequate but the blood has a decreased hemoglobin concentration.

I sincerely hope that I haven't messed any of my numbers up, I've been on call and have been awake for going on 36 hours

I've HEARD in passing that getting transfused one unit of PRBC is supposed to bump hemoglobin an average of 1 point, 2 units is 2 points, etc., absent any existing bleed of course. Not sure however if this unconfirmed ratio applies to blood loss.

One unit PRBC on average is @ 350cc I think.

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When you donate blood, they typically say that your hemoglobin will drop 1 point and your hematocrit by 3% post donation.

You know you're an Oncology nurse when you read the OP and think "what's wrong with a hemoglobin of 8.2 g/dL?" Our kids are not transfused until Hgb