Why O neg?

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I was wondering why when a patient comes into the Emergency Room and needs a transfusion he/she is given O negative blood.

I realize that O is a universal blood type, but being a female I also know that having negative blood has to be monitored during pregnancy. I'm not quite sure why, but I remember the doctors & nurses always asking me that.

So why wouldn't O positive be a better blood to use during an emergency procedure until the patient's been typed?

-- AmyE (roamyn@aol.com), March 11, 2000


The positive and negative of a blood type identifies the presence of antigens in the blood. If someone is positive, they have the antigens. If they are negative, then they don't. If you transfuse positive blood into someone that is negative, you can cause hemolysis of the erythrocytes. In layman's terms that means your red blood cells will break down.

They track the Rh factor in a pregnant woman because there is a chance that if a negative mother receives blood from a positive fetus, she and the fetus can be in great danger.

On the other hand, if negative blood is tranfused into someone with positive blood, nothing will happen. Antigens are not necessary, they just happen to exist in many people's blood.

-- Brett Champion (bchampion@home.com), March 11, 2000.

The last responce was mostly correct but.. if you transfuse Rh negative blood into and Rh positive person- nothing will happen in regards to the D antigen but there are many other antigens on the rbc and some of these are as strong as the Rh (D) antigen and can cause just as many problems. (c,c,E,e,Kell, Duffy etc) Any transfusion takes a risk of building antibodies by the recipient unless the blood is from the recipient himself. (Donation by the recipient before a surgery). And hemolysis is not the only problem if you give a unit of blood that the person has an antibody to. You also have the problem of the rbcs agglutinating in the circulatory system. Many of the body's main organs will shut down when this happens. This is usually prevented by doing an A,B,O typing on the recipient and a screening for atypical antibodies. When blood is just given without this, there is a much bigger risk of complications. Sorry for the run-on!

-- joan (joanofarc24@hotmail.com), March 12, 2000.

My Biology Teacher explained Blood Types to us in a very good way. A and B are the 2 types, while O is the lack of any antigens. Positive is having another antigen, while negative is the lack of the antigen. That means that O- is blood without any antigens. If you remember the episode with the nurse strike, Carol accidentally left some type specific blood on the Auto Transfuser and that caused the man to bleed out and die. You may want to know why not give an A+ person A- if it wont hurt them, but I THINK it will, and if you already know they are A, why not give them their specific blood...... hmmmmmm, well that is my knowledge about this topic, if anyone else out there knows more than that, please post it!

-- Steven Jacobson (steven@episodeguides.com), January 01, 2001.

When they "type and crossmatch" -- what exactly does crossmatching involve? Is this testing for the antibodies that have been mentioned, or do they mix samples of the donor's and recipient's blood to see if there is a bad reaction?

-- Driad (driad@mailcity.com), January 02, 2001.

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