Giving O Positive Units to an Rh Negative patient

[Joanne P. Scannell]

Correct ... Immunomodulation.

The way I understand it is that you overwhelm the immune system . . . that was from a graduate Immunology course circa 1982.

[Joanne P. Scannell]

Careful about this ...

Can't recall off the top of my head (must be tucked away somewhere) ... but I do remember reading that it's dangerous to give Rh-Ig to a patient who has recieved greater than 20% of their blood volume ... you are inducing a 'passively acquired' extravascular hemolytic reaction.

It's pretty tough to give enough RhIG to counteract transfused RBC units. Most of would not have that as a protocol unless we were forced to give D+ blood to a young D- female. Then I think I would try to arrange for her to have an exchange transfusion with Rh neg blood, then estimate residual Rh pos cells and give RhIG to handle that amount. That said, I don't know that we really have the capability to exchange an adult and I know we don't have a good way to estimate the residual Rh pos cells in the patient. Fetal Screen would be pretty inaccurate. Kleihauer won't work since it detects fetal Hgb. I guess we could ship her to someplace they can do flow cytometry for Rh pos cells. Mostly we will save our Rh neg cells for her so we don't ever have to do that.

[Joanne P. Scannell]

Because of the issues written in these postings (and others), we try to switch to Rh-Pos as early as possible when we know there will likely be a large amount of blood needed for the case.

Yes, we require pathologist's approval (our Med Dir isn't always on call) and we document that approval.

We do NOT even think about Rh-Ig ... after a unit or two, it is too risky. If the patient were a woman under 50yrs, we'd consider it. Key word: 'Consider'.

Once a patient recieves Rh-Pos

Brenda,

I would like some more information on the idea of switching an O negative male to O positive during surgery. We had a situation this past weekend where we had an emergency heart surgery on an O negative male who ended up using several units. The OR took 4 and requested 4 more. Our normal O neg inventory is 12 units (if we can get that many!) At what point would advocate switching this patient to O positive? Should it require medical director approval? If we do switch to O pos, when do you offer RhIg and how much do you give?

Thanks, Amelia

[AMcCord]

Careful about this ...

Can't recall off the top of my head (must be tucked away somewhere) ... but I do remember reading that it's dangerous to give Rh-Ig to a patient who has recieved greater than 20% of their blood volume ... you are inducing a 'passively acquired' extravascular hemolytic reaction.

When treating ITP in Rh Positive individuals with Rhophylac, one of our hematologists stated that we should expect to see a 1 gram Hgb drop for every Rhophylac 'dose' administered and that a more severe hemolytic episode was possible. The suggested dose for ITP treatment is 250 IU (50 mcg) per kg body weight. Based on that tidbit of information, I would think that the potential for severe hemolysis if you dosed an Rh negative patient who had been transfused with multiple units of Rh positive red cells would be pretty high.

[Barbarakym]

It took me awhile to go through this great debate. I will say I agree and disagree. How is that for being consistent?

I believe in ONEG for Trauma until you get a blood type. Which should be a priority as most of these traumas are not going to be ONEG and then you don't have a problem. What does a blood type take 10 min post draw? Usual order I have seen is 6 untis.. You should have 6 units set aside for this in most blood banks.... we have minimum inventory of 12. Give 6 in a cooler and if it is going past 6 units that is the time to evaluate. Usually you have an hour.. sometimes not. Blood type..... most will be different blood type and you can safely switch to that blood type if only 6 units were given. Usually we get 3-4 of these units back once we send up type specific, XM (30 min if no antibody). Save the dicy stuff for those that truly need it. Hemmoraging... will we have transfused multiple bad antibodies (duffy/kidd/kell) in emergency to having nothing more than a positive coombs on eval. maybe shorter life. But nothing more on any hemmorage case. Trick is (as someone mentioned) to stay on top and give the 'bad blood' first while its all ending up on the floor. I even had a doctor ask me in a bad antibody hemmorage... " OK this is the bad blood right"? And I said yes... he transfused. He called back "OK slowing down.. We started with blood neg for bad antigens first, as they were closing we gave the 'really good compatible stuff'. She had positive DAT, No real drop of HGB and no hemolysis. Takes a team. Sometimes BB is the forgotten member of that team. Biggest problem to proper management in a bb transfusion crises. IMO.

[L106]

You have brought up many good points, Barbarakym. Thanks!

[Kimster]

It's pretty tough to give enough RhIG to counteract transfused RBC units. Most of would not have that as a protocol unless we were forced to give D+ blood to a young D- female. Then I think I would try to arrange for her to have an exchange transfusion with Rh neg blood, then estimate residual Rh pos cells and give RhIG to handle that amount. That said, I don't know that we really have the capability to exchange an adult and I know we don't have a good way to estimate the residual Rh pos cells in the patient. Fetal Screen would be pretty inaccurate. Kleihauer won't work since it detects fetal Hgb. I guess we could ship her to someplace they can do flow cytometry for Rh pos cells. Mostly we will save our Rh neg cells for her so we don't ever have to do that.

I have attached a case study from Ben Taub in Houston, Dr. Werch had 2 cases related to trauma and each were treated for the amount of infused RBC's. This was a poster presentation at AABB, then she submitted the study for publication.[ATTACH]630[/ATTACH]