Curious about Rhig dosing

[dcubed]

I am sure that many of us have seen when FMH testing indicates that a D neg Mom needs to get several vials of Rhig after delivery of a D pos infant. For example, a couple of years ago we had to give 6 vials of Rhig. Six vials of Rhig will protect against 180 ml bleed of D pos blood. That much of a bleed would seem to represent more than half the blood volume of an "average" sized normal newborn. You would expect the infant to be quite anemic, yet in fact the infant in this case and others like it have not been anemic. What is the explantion?

[AMcCord]

The fetomaternal bleed could have been occurring over time as a slow but steady blood loss, rather than one large bleed.

[L106]

Also, too, I'm under the impression that sometimes our quantitative tests may not really be as precise as we would like. If this is the case, a small variation in the quantitation can result in quite a variation in the final calculated "total bleed". (But, this isn't my expertise, so I may be off-base.....)

[John C. Staley]

I am really stretching the memory cells with this one but there is a condition where fetal hemoglobin continues on into adulthood. I'm not sure I remember what the percentage of HgbF is in these cases but that could explain a lot of HgbF in mom and a healthy nonanemic infant.

Also, the calculations for dosage was always, "figure out how much you need and then add one more just to be on the safe side". The other thing to consider was if K-B stain or Flow cytometry was used to determine the extent of the fetal bleed. Flow is much more accurate.

:writersbl

[David Saikin]

I have given 7 doses in the past . . . the MD commented that he had to manipulate the placenta more than usual - we felt he manipulated a lot of fetal cells into the mother.

[Deny Morlino]

WOW!!! Scary situation .

[dgibaud]

The problem is that the accuracy of tests like the KHB is NOT very good. You might get a more satisfactory answer if you used continuous flow cytometry, but not many places have the luxury of having flow cytometry.The good news is that overestimation of FMH is not harmful to anyone (one could argue that getting multiple vials of RhIG is painful, but not harmful). Kudos for realizing that a FMH that high should result in an anemic baby. Sometimes you have to see the entire picture. However, what physician would reduce the recommended Rhogam dose based on the baby's Hgb level? The KHB isn't a great test, but at the moment it's all we have.

[adiescast]

We had a situation at one hospital where I worked that the baby exsanguinated completely into the mother's system. It was very sad. Not only was the mother bereaved, but she had to have multiple RhIg shots in both hips. I don't remember how many vials, but it was a ridiculous amount. They even combined some of the vials so she got fewer sticks.

There is a risk to giving RhIg or any intramuscular shot. The patient could develop an abcess at the injection site (or sites). This could lead to infection.

[Fluffy agglutinates]

In the UK large doses are 'encouraged' to be given IV rather than IM. It also means you don't have to give as much & the mother doesn't have a throbbing shoulder! There is also discussion taking place over the benefits of the 28 week prophylaxis dose being given IV instead of IM.

[Malcolm Needs ☆]

In the UK large doses are 'encouraged' to be given IV rather than IM. It also means you don't have to give as much & the mother doesn't have a throbbing shoulder! There is also discussion taking place over the benefits of the 28 week prophylaxis dose being given IV instead of IM.

True, but you have to be a bit careful.

The IM anti-D always used to be made by fractionation using the Cohn cold ethanol method (I don't know if this is still true) and would have a yield of only about 35% of the anti-D and should NOT be given IV. Wherreas the true IV anti-D is made by ion exchange, has a much higher yield of between 85 and 90% (with no demonstrable IgA or IgM) and can be given either IM or IV.

This information, I should warn you, may well be out of date now!!!!!!!!!!!!!!

:confuse:

[Fluffy agglutinates]

This is where the package insert needs to be read most carefully - most of the products in use currently have specific instruction on how to use in cases for IM or IV (& if not suitable for IV will say so!). The major product in the UK at the moment is...

Rhophylac

®

Rh0(D) Immune Globulin Intravenous (Human)

1500 IU (300 mcg)

For Intravenous or Intramuscular Injection

Initial US Approval: 2004

I think for the US it's RhoGAM? (that insert handily instructs you not to inject the newborn baby!)

[Malcolm Needs ☆]

[quote=Fluffy agglutinates;

I think for the US it's RhoGAM? (that insert handily instructs you not to inject the newborn baby!)

[Deny Morlino]

You may laugh, but I have known this to happen, and, on occasions, the anti-D to be given to the lady's partner!

:eek::eek:

This just emphasizes the fact that many nurses do not understand the purpose and assumed mechanism of RhIg. Education is a bigger part of our jobs than many probably expected when going to school to become CLS's.

Rophylac is beginning to catch on in the US. CSL Behring began a big marketing push a couple of years ago. We have been satisfied with the product (and the overnight delivery).

[bcham]

In an earlier message someone spoke of placental manipulation. It is key to remember with some of these bleeds that the placenta contains a much larger volume of blood than the baby does and can contribute massive amounts of blood to maternal circulation.

[AMcCord]

In an earlier message someone spoke of placental manipulation. It is key to remember with some of these bleeds that the placenta contains a much larger volume of blood than the baby does and can contribute massive amounts of blood to maternal circulation.

Multiple births - twins, triplets, etc. - can result in the need for more RhoGAM.