SRNA Blood transfusion question

Nitecap · Jun 6, 2006

i know the formulas for figuring out the hgb drop to transfuse for a predetermined hgb, and texts also utilize the 20% loss from the ebv. i was talking to my crna preceptor the other day and he stated he had a post c-section that lost around 2000cc's of blood and he went ahead and transfused, or wanted to transfuse can't remember which. he stated he was talking to the anesthesiologist and he stated that only time a transfusion is warranted (from a board testing standpoint) is when a patient cannot maintain there o2 saturation with their current hemoglobin level (i am referring to a low hemoglobin level causing the sat drops and not another reason). i cannot find this in any text and all texts will give you different "parameters" and i don't know of any particular hospital policies at any clinical site i have been at. can someone clarify this for me i know it depends on the patient and what is going on but is a dropping sat really the only true reason to give blood? if so can you give me a reference?
also is there any way we can have a srna section like the pre-crna so those of us in school can ask questions in an appropriate area so you don't have to weed out through the other non srna questions?
like you said all pts are different. the calculation of mabl (max allowed blood loss) just gives a set number that tells you hey this pt has lost or is losing alot of blood. maybe i should be checking hbg, reasses the pt ect ect. many pts will die if you let them bleed to that max amt b/c they simply cant tolerate it. o2 carrying capacity is the only reason you should transfuse blood. if the hgb is fine and the pt is bleeding d/t coagulation issues you give ffp or platletes ect. if the pt is hypovolemic with a good hgb you give crystalloid of colloid b/c your issue is volume not o2 carrying capacity. you dont give blood soley for volume or coagulapathies ect though if the hgb is low and you transfuse it does help with your volume issue. i dont think you are going to find a transfusion cook book in any text on when to transfuse. its highly variable some pts good at a hgb of 7 while others crumping at 7. you have to assess the pt and decide when you need the blood. perhaps that crna made a judgement that the pt would tolerate the
2l blood loss and went ahead and transfused to stay ontop of things, who knows.
i dont think we need a seperate srna forum. ask questions here so you can get insite from crna's that have been practicing a while.

Nitecap · Jun 6, 2006

i know the formulas for figuring out the hgb drop to transfuse for a predetermined hgb, and texts also utilize the 20% loss from the ebv. i was talking to my crna preceptor the other day and he stated he had a post c-section that lost around 2000cc's of blood and he went ahead and transfused, or wanted to transfuse can't remember which. he stated he was talking to the anesthesiologist and he stated that only time a transfusion is warranted (from a board testing standpoint) is when a patient cannot maintain there o2 saturation with their current hemoglobin level (i am referring to a low hemoglobin level causing the sat drops and not another reason). i cannot find this in any text and all texts will give you different "parameters" and i don't know of any particular hospital policies at any clinical site i have been at. can someone clarify this for me i know it depends on the patient and what is going on but is a dropping sat really the only true reason to give blood? if so can you give me a reference?
also is there any way we can have a srna section like the pre-crna so those of us in school can ask questions in an appropriate area so you don't have to weed out through the other non srna questions?
thanks,
soliant

also you cant always assume that the sat will always drop in the presence of blood loss. spo2 measures the % of hbg saturated with o2. you can have a significant drop in hgb without the sat changing at all. in fact the sat may be even better. eg start out with hgb of 14 and hgb drops to 9. we are still delivering the same amt of o2, have no hemodynamic changes and pt is doing well yet we have less hgb. theoreically the sat can increase. many times you start seeing saturation changes on the lower end of hgb levels.

on a test if they ask about spo2, hgb and transfusion i would not at all pick decrease in sat=need to transfuse as your attending said. on the contrary they will put low sat in there as a distractor trying to get you to bite thinking you have the mentality low sat=transfusion without assessing the situation and taking into account other issues. the better answer may be assess the hgb though other interventions that are quicker may take priority depending on the question.

Nitecap · Jun 6, 2006

You also have to take account dyshemoglobinemias such as methb ect. In this case the Hgb may be normal but the Spo2 innaccurate.

Tranman · Jun 6, 2006

I definitely agree with Nitecap. I may be able to find a text to reference, but it's late and I'm lazy. sorry.

But a dropping sat d/t low hgb is definitely time to transfuse. You should have been transfusing already in preparation of that really. you shouldn't wait until a patient actually drops their sats d/t a low H/H.

For example, if an elderly patient just had a bloody Hip Sx and started out with an H&H of 10/30 (relatively normal values) and say you lost 800cc bld loss during the case. Let's say you gave plenty of crystalloid and decided not to give bld during the case and postop H&H is 8/28 (normovolemic). This patient is likely to continue to ooze and will likely be transfuse later on during the day anyway. I would go ahead and transfuse during the end of the case foreseeing the need for blood later and hoping to avoid problems later on. If not, I at least mention to the surgeon that the patient will likely need blood and it would be a good idea for him/her to order it.

You can probably find in varying texts to give blood when the Hbg is 10. this is controversial b/c many patients are stable at a Hgb of 10 while others are teetering on crumping. Ok so I went and looked it up. This here comes from "Clinical Anesthesiology" by Morgan and Mikhail 2nd edition page 548.

"Ideally, blood loss should be replaced with crystalloid or colloid solutions to maintain intravscular volume (normovolemia) until the danger of anemia outweighs the risk of transfusion....For most patients, that point corresponds to a hgb b/t 7-10g/dL. Below a hbg cnc of 7, the resting cardiac output has to increase greatly to maintain a normal oxygen delivery."

so somewhere b/t a hgb of 7-10 most patients maintain normal oxygen delivery. Below "this point" CO has to greatly increase to maintain perfusion (or normal sats) and a patient is now considered anemic. This is a good time to start replacing blood. At the point that a patient starts dropping their Sats b/c of a low Hbg, you are looking at a decompensating patient. The patient is now on the edge of crumping or is crumping. The ability to compensate for the lower Hgb is now approaching a critical point. Morgan and Mikhail says you should transfuse when the patient is compensating and not wait till the patient decompensates. Waiting for a Sat to drop is really waiting too long.

Tranman · Jun 6, 2006

You also have to take account dyshemoglobinemias such as methb ect. In this case the Hgb may be normal but the Spo2 innaccurate.

dyshemoblobinemias such as methhemoglobin is usually transient. I am assuming your're talking about when you give indigo carmen or methylene Blue. It's true, that here the Sat reading is not appropriated to pt's hgb, but this is usually transient , where as a low sat d/t low hgb is not transient.

Also factor to consider is N02. If you're running nitrous, your sats maybe 2-3 points lower than if you weren't running nitrous.

BeatOU · Jun 6, 2006

Also you cant always assume that the sat will always drop in the presence of blood loss. SpO2 measures the % of Hbg saturated with O2. You can have a significant drop in Hgb without the sat changing at all. In fact the sat may be even better. Eg start out with Hgb of 14 and hgb drops to 9. We are still delivering the same amt of O2, have no hemodynamic changes and pt is doing well yet we have less hgb. Theoreically the Sat can increase. Many times you start seeing saturation changes on the lower end of hgb levels."
Nitecap,
Based on your explanation above, which I agree with, why would the SpO2 ever drop during bleeding? I mean, if there were only 2 RBC's left, could not they still have good sats? Of course, I'm not a SRNA yet, but it seems like we give a lot of blood in the ICU for volume issues and low HgB--not because the patient's sats are dropping.
is this strictly an "in surgery" situation? I'm not arguing, just interested for my own edification.

Nitecap · Jun 6, 2006

Also you cant always assume that the sat will always drop in the presence of blood loss. SpO2 measures the % of Hbg saturated with O2. You can have a significant drop in Hgb without the sat changing at all. In fact the sat may be even better. Eg start out with Hgb of 14 and hgb drops to 9. We are still delivering the same amt of O2, have no hemodynamic changes and pt is doing well yet we have less hgb. Theoreically the Sat can increase. Many times you start seeing saturation changes on the lower end of hgb levels."
Nitecap,
Based on your explanation above, which I agree with, why would the SpO2 ever drop during bleeding? I mean, if there were only 2 RBC's left, could not they still have good sats? Of course, I'm not a SRNA yet, but it seems like we give a lot of blood in the ICU for volume issues and low HgB--not because the patient's sats are dropping.
is this strictly an "in surgery" situation? I'm not arguing, just interested for my own edification.
Eventually the tissues are going to extract more than the O2 carrying capacity of the low Hgb causing the sats to drop. Again you dont give blood b/c the sats are dropping, you give it for O2 carrying capacity. If the pt is actively bleeding or has lost alot the MDs are prob giving the blood and killing 2 birds with one stone replacing volume and O2 carrying capacity. Just think do you ever see them giving blood to a hypovolemic pt with a hemoglobin of 14. No they are transfusing when the Hgb is low. What does hgb do, it carrys O2 to the tissues with is vital for cellular function.

Focker, CRNA · Jun 6, 2006

I think a good example of what a pt. might do if their H/H is too low and they are lacking O2 carrying capacity is a pt. that is hypotensive and refractory to the usual treatments (like ephedrine, neo, fluids). In that case, you may see the patient BP rise to an acceptable level after transfusing them not because of the fluid volume from the colloid you just gave, but because of the extra O2 carrying capacity so that the heart now is recieving all the O2 it needs and can pump more efficiently.

athomas91 · Jun 6, 2006

i agree w/ nitecap... even if your hgb is 7 - that hgb could be 100% saturated. in terms of boards - and what you will study is that a normal healthy person will not show any sx or distress until your hgb hits 7 (some texts say 8) ... so i would transfuse based on patient presentation and lab values... if their sats are dropping- you have waited too long and i would worry about far worse things than anemia.

BeatOU · Jun 7, 2006

"Again you dont give blood b/c the sats are dropping, you give it for O2 carrying capacity."
Ok, i get it. So you are transfusing because of the expected distortion of the SVO2 caused by a drop in Hgb. I understand that. I thought you were saying that a person with low Hgb would present with desaturation on the pulse ox.

Tranman · Jun 7, 2006

"Again you dont give blood b/c the sats are dropping, you give it for O2 carrying capacity."
Ok, i get it. So you are transfusing because of the expected distortion of the SVO2 caused by a drop in Hgb. I understand that. I thought you were saying that a person with low Hgb would present with desaturation on the pulse ox.
What do mean by "the expected distortion of the Svo2"? It is either distorted (dropped) or it is not. You don't give blood b/c you are expecting the sat to drop from low hgb. You'll give blood 1st to keep the pt/VS stable. The BP is where you'll see the effects of low hgb 1st, then later you may see a drop in sats (due to low hgb or low o2 carrying capacity: same difference), then even later you'll definitely see a drop in sats. This point is really late in the game to be thinking about transfusing.
He is saying that a person with low Hgb doesn't necessarily present with desaturation. This is b/c the person can compensate by increasing HR or CO = Increase tissue perfusion = Sats are maintained. At the point that you see the sats dropping (due to blood loss i.e. low hgb), this is really late in the game and you need to give blood ASAP now. One may say that this is not the point to give blood, but what they mean to say is that you should've been giving blood already to avoid getting to this point.
Eventually the tissues are going to extract more than the O2 carrying capacity of the low Hgb causing the sats to drop. Again you dont give blood b/c the sats are dropping, you give it for O2 carrying capacity.
He is also saying you don't give blood for low Hbg but you give blood for loss of o2 carrying capacity 2nd to loss of bld (or low hgb). This is being a bit technical. Technically correct, but loss of o2 carrying capacity is due to loss of hgb. Initially a little loss of Hgb is compensated for by Inc HR/CO. Later, more loss of hgb leads to loss of O2 carrying capacity b/c the tissues extract more O2 than what is delivered ( = lowered sats).
So in the spirit of keeping it simple. loss of blood => loss hgb (don't necessary see drop in sats yet). More loss of hgb => loss of O2 carrying capicity => lowered sats.
Get it?