What is Hemodialysis (Extracorporeal dialysis)?

Hemodialysis (haemodialysis), also called kidney dialysis or just dialysis, is a treatment for acute kidney failure. Patients need dialysis if their kidneys are not working properly, i.e. they are no longer removing enough waste (such as creatinine and urea) and fluid from the blood. This usually happens when around 85-90 percent of kidney function is lost.

In order to perform the hemodialytic treatment, the blood of the patient is put in an artificial kidney which, through the pumping machine, circulates the blood through a filter that cleans it, and returns it back to the patient. Therefore, the blood needs to be extracted from the patient.

In urgent cases this is implemented by putting a catheter inside a big blood vessel (central venous catheter). In case the treatment could be scheduled in advance, the substitutional treatment is performed by arteriovenous fistula, which is a junction created surgically (using local anesthetic) between a vein and an artery, most frequently at the level of the forearm.

At the beginning of the dialytic session, the patient is connected to the hemodialytic machine by central venous catheter or by the insertion of two needles at the level of the fistula.

Every treatment lasts approximately 4 hours, and is done 3 times per week. The duration of every treatment and the weekly frequency could vary, depending on physician’s discretion based on clinical necessity of the patient.

The main point of the treatment is “the dialytic filter”, an element with bio-compatible dual compartment. Blood extracted from the patient flows in the first compartment. In the second compartment flows aqueous solution, enriched with solutions essential for the blood. This solution is also low in (or deprived of) waste that needs to be extracted and it’s called “dialytic solution”. To allow an adequate depuration, the blood flow through the filter is maintained with the help of a pump, with a flow rate of around 250-300 ml/min.

The amount of fluid, that is extracted during a single treatment, depends on the quantity of liquid that the patient takes in the interval between two consecutive sessions. Fluid intake is measured by weighing the patient at the end of the dialytic treatment and at the beginning of the following one. The “ideal weight” of the patient, called “dry weight”, is defined according to the clinical and instrumental data of the nephrologist who practices the dialytic treatment.

The truth behind your blood groups

The truth behind your blood groups

We inherit blood group genes from our parents, with odds of receiving one A and one B gene lower than other possible combinations

65% of people donated blood at least once in their life and 80% of people know their blood group, so if you happen to be among those percentages and you found out you’re type AB, you’re pretty unique, in fact, you have the rarest blood type of all. So why are so few people categorized as AB?

 

“We inherit our blood groups on genes”

or to give it a more scientific formula “The blood group gene encodes for a protein that gets expressed on the surface of the red cell and that is what is detected in the laboratory. So what is expressed on the surface of the cell determines the type and which blood is compatible with which patient.”

 

Let’s take a step back to refresh the basics :

All blood contains the same basic components: red cells, white cells, platelets, and plasma, which is the liquid portion of blood holding the red and white blood cells along with the platelets in suspension.

 

Red Blood Cells

Red blood cells, manufactured in the bone marrow, perform the hard work of carrying oxygen around the body. In every two to three drops of blood, roughly one billion blood cells reside. Red cells far outnumber both the platelets, which stop bleeding by clotting blood vessel injuries, and white cells, which protect your body from pathogens and disease. For every 600 red blood cells there are a mere 40 platelets and just one solitary white blood cell.

 

On the surface of the red blood cells are proteins with attached carbohydrates, essentially markers that identify the blood cells as our own. These microscopic markers, known as antigens, are commonly grouped in eight basic blood types: A, B, AB, and O, each of which can be either “positive” or “negative.”

 

“Blood group A means you have at least one blood group A gene and as a consequence your blood expresses an enzyme that attaches a distinct sugar to the protein or lipid on the red blood cell surface,” or to be more simple “Blood group A has only A antigens.”

 

Similarly, blood group B has only B antigens, blood group AB has both, and blood group O has neither A nor B antigens on the surface of the red blood cells. These four groups are the most important because they indicate which blood type a patient can safely receive in a transfusion.

 

Patients receiving an incompatible blood type often experience a dangerous reaction; their immune system would recognize the unfamiliar antigen on the blood cell surface and attack. So if you were to give blood group A to a blood group B patient, their body would mount an immune response to destroy what it recognized as a foreign invader.

Meanwhile, your blood is either “positive,” meaning it contains the Rhesus D antigen, or “negative” meaning it lacks it. This is another inherited blood marker that also matters when it comes time for a transfusion.

Different blood groups are more and less common, with Stanford School of Medicine calculating the proportions in the general population as follows:

 

O-positive: 37.4 percent

O-negative: 6.6 percent

A-positive: 35.7 percent

A-negative: 6.3 percent

B-positive: 8.5 percent

B-negative: 1.5 percent

AB-positive: 3.4 percent

AB-negative: 0.6 percent

These are “not 100% accurate percentages” since they vary somewhat based on ethnic background. For example, blood group B is more prevalent in Asian specially in middle east individuals compared to Caucasians or Africans , while Group O is more common in Hispanics. Based on the population as a whole, though, these are the approximate proportions.

Rarest of All

Still, this chart makes it easier to see why blood type AB is so rare. Though you inherit one gene for blood type from each parent, there’s an unusual catch: whenever you inherit an O gene, it more or less has no impact on the other gene inherited. So A type people either inherited an A gene from both parents or an A gene from one parent and an O gene from the other. Same for B group people. O blood type people inherited two O genes.

 

People with AB blood inherited an A gene from one parent and a B gene from the other. Based on the underlying number of people in the A and B blood types, the odds of that particular combination happening are simply lower than any other possibility.

 

In the case of blood types, being the rare one offers one huge advantage: people who are AB positive can receive any blood type and so are known as “universal recipients.” If you’re more of a giver, though, you’d much rather have O negative blood. Known as the “universal donors,” these generous souls can give to, and be accepted by anyone in need.

 

Each year, 5 million Americans receive a necessary transfusion. No matter your type, please consider giving the gift of life sometime soon.

 

By : Ammar Yasir

3rd stage medical student at Alanbar University College of Medicine

for further details or questions : email : fleverguy.ammor@gmail.com

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