Your Daily Meds - 5 November, 2021

Good morning and welcome to your Friday dose of Your Daily Meds.

Bonus Review: What are the major blood groups? How are they determined and why are they important?

Answer: ‘Blood groups’ is a term that is used to refer to the genetically determined antigens that are present in the membranes of red blood cells.

The importance of these ‘groups’ then, is related to the degree of antigenicity of these antigens in the membrane.

The ABO grouping system are the most important because they are the most antigenic. The Rhesus (Rh) grouping system also has significant antigenicity.

Then there are many other descriptors and systems of blood grouping which describe antigens of much lower clinical importance.

Case:

Which of the following patterns of serological test results indicates vaccination against hepatitis B virus infection?

* HBsAg negative; Anti-HBc positive; Anti-HBs positive

* HBsAg negative; Anti-HBc negative; Anti-HBs negative

* HBsAg negative; Anti-HBc negative; Anti-HBs positive

* HBsAg positive; Anti-HBc positive; Anti-HBs negative

* HBsAg positive; Anti-HBc negative; Anti-HBs positive

(Where: HBsAg = hepatitis B surface antigen; Anti-HBc = antibodies to hepatitis B core antigen; Anti-HBs = antibodies to hepatitis B surface antigen)

Pause for a moment.

Sift through this pile of acronyms.

And scroll for the chat.

Ward Call:

You have just arrived to start your evening shift when you receive a call from the maternity ward about a patient who is receiving a blood transfusion.

Hi Doctor, could you please come and review Mrs Smith in the maternity ward? We started a blood transfusion for her approximately 15 minutes ago and now she is a bit unsettled. She is a little bit warm at 37.9 degrees and looks a bit flushed across her chest. I am worried she is having a transfusion reaction.

While you have this nurse on the phone, what further questions could you ask to triage this concern?

Have a think.

More scroll for more chat.

The Big B:

The pattern of serological investigations in the patient vaccinated against hepatitis B virus infection is characterised by the patient testing negative for hepatitis B surface antigen (HBsAg), negative to antibodies to hepatitis B core antigen (anti-HBc) and positive for antibodies to hepatitis B surface antigen (anti-HBs). 

The patterns of serological test results for hepatitis B infection are given in the following table:

Hot and Bothered:

Alright. Some questions you could ask over the phone to triage your concern regarding a transfusion reaction include:

* What symptoms does the patient have?

* Fevers, chills, chest pain, back pain, diaphoresis and dyspnoea can all be manifestations of a transfusion reaction.

* What are the vital signs?

* Need to know as anaphylaxis will look very different to fever alone.

* Which blood product is being transfused?

* How long ago was it started?

* Instant anaphylaxis reaction versus effects of fluid overload etc.

* What was the reason for admission?

* Symptomatic anaemia post caesarean section versus ongoing haemorrhage etc

Most transfusion reactions are non-haemolytic febrile reactions, especially if this is a multi-transfused or multiparous patient, and are due to WBC antigen-antibody reactions or cytokines. The transfusion does not need to be stopped and she may just need some paracetamol and promethazine.

BUT

The reason you are asking some questions over the phone is because the major threats to life with transfusions include:

* Anaphylaxis = deadness

* Acute Haemolytic Reaction - can cause Disseminated Intravascular Coagulation (DIC) = deadness

* Transfusion-Related Acute Lung Injury (TRALI) - respiratory failure = deadness

* Transfusion-Associated Circulatory Overload (TACO) - circulatory failure = deadness

* Bacterial contamination - septic shock = deadness

Bonus: Consider a Rhesus (Rh) positive foetus being carried by a Rh negative mother in her first pregnancy. Would that foetus be affected by the mother’s antibodies against foetal red blood cells?

Answer in Monday’s dose.

Closing:

Thank you for taking your Meds and we will see you Monday for your MANE dose. As always, please contact us with any questions, concerns, tips or suggestions. Have a great day!

Luke.

Remember, you are free to rip these questions and answers and use them for your own flashcards, study and question banks.

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