What is Acid-Base Status and Why is it Important?

 

Photo by Dr. Haus

Acid-Base Status

The acid-base status of a patient allows us to know the pH of the bloodstream and to determine if there are any abnormal changes to bloodstream's homeostasis.

 

The four (4) states of acid-base imbalances

1. Respiratory acidosis (acidic pH (low pH) due to accumulating carbon dioxide in the lungs)
2. Respiratory alkalosis (basic pH (high pH) due to expelling too much carbon dioxide in the lungs)
3. Metabolic acidosis (acidic pH (low pH) due to too much acid in the bloodstream that IS NOT due to the lungs)
4. Metabolic alkalosis (basic pH (low pH) due to too much base in the bloodstream that IS NOT due to the lungs)
   
   

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Why is Acid-Base Status Important?

Knowing the acid-base status of a patient is important to know the patient's overall health and to treat any conditions that are affecting the body's bloodstream pH.  Even slight changes in bloodstream pH can be fatal and these types of changes need to be known as quickly as possible to reverse them.

What is Anti-Diuretic Hormone and Why is it Important?

Photo by Dr. Haus

Anti-Diuretic Hormone

Anti-Diuretic Hormone, also called ADH or vasopressin, is a hormone that is produced in the hypothalamus and released by the posterior pituitary gland.  ADH causes the kidneys to reabsorb more water thus decreasing the amount of water lost in the urine and to create a more concentrated urine.

 

The steps of the release of ADH is written out below and followed by an infographic:

1. The hypothalamus senses increased osmolarity of the bloodstream (increased concentration of solutes)
   
2. The osmoreceptors in the hypothalamus shrink (due to a higher osmolarity in the bloodstream versus inside these cells)
   
3. The hypothalamus sends an electric signal via the neurons to the poster pituitary gland to release ADH
   
4. The ADH enters the bloodstream and arrives at the kidneys
5. The kidneys increase the number of aquaporins in the distal tubules and collecting ducts
   
6. More water is reabsorbed into the body and less water is urinated out
   
   
   
   
   
   
   

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Why is ADH Important?

ADH is extremely important because it allows the body to have the correct amount of water in the body.  Water is the basis of life and if there is not enough water in the body the body will not be able to survive very long.

As an aside, alcohol and caffeine are two substances that block the release of ADH from the posterior pituitary gland.  Due to this, the kidneys are not able to reabsorb water into the bloodstream which causes increased urination of very dilute urine.

Think about the last time you had an adult beverage or drank tea/coffee.  Did you have to pee shortly after?  Was your urine very light in color?  You can thank the blocking of the release of ADH for that change.  Cheers!

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What is Erythropoietin (EPO) and Why is it Important?

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Erythropoietin (EPO)

Erythropoietin, called EPO for short, is a hormone that is released by the kidneys that tells the bone marrow to increase erythropoiesis.  Erythropoiesis is the production of new red blood cells and this occurs in the bone marrow of the body.

 

The steps of the release of EPO is written out below and followed by an infographic:

1. The kidneys sense less oxygen arriving to the kidneys in the bloodstream
2. The kidneys release EPO from the peritubular cells
3. The EPO travels in the bloodstream to the bone marrow
4. The EPO signals the bone marrow to increase the rate of erythropoiesis
5. The bone marrow increase red blood cell synthesis
   
6. Once the oxygen levels in the bloodstream increase the amount of oxygen arriving in the bloodstream to the kidneys goes back to normal and the peritubular cells stop releasing EPO
   
   
   
   
   
   

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Why is Erythropoietin Important?

EPO is extremely important because it allows the body to have the correct amount of red blood cells.  The red blood cells are needed to bring oxygen to all the cells of the body to keep them alive.  Having too few (or too many) red blood cells is detrimental to the body.

As an aside, athletes can "dope" their blood with EPO (think Lance Armstrong here).  When athletes take EPO as a performance enhancement drug, they are increasing the number of red blood cells in their body which allows them to bring more oxygen to the cells of their body.  This allows these athletes to have more oxygen allowing them to fatigue less quickly.  This is obviously not legal and is cheating.

Now, you may also know that many athletes try to train at higher altitudes.  This is a strategic decision because at higher altitudes there is less oxygen in the air.  Due to this, people and animals that live at higher altitudes have more red blood cells in their body as their kidneys respond to having less oxygen in their system than a(n) person/animal at a lower altitude.  This is one way athletes strengthen their bodies for competition.  If you are working as a medical professional at a higher altitude it is important to know that the hematocrit (volume of red blood cells in the bloodstream) of patients at higher altitudes should be higher than at lower altitudes.

It is also unhealthy to have too many red blood cells in the bloodstream and this is called polycythemia.  This is dangerous because the blood becomes thicker, think sludge flowing through your body.  This puts a patient at risk for a blood clot, a fatal condition where blood flow is blocked causing no oxygen or nutrients from arriving to the body.

What is the RAAS and Why is it Important?

Photo by Dr. Haus

Renin-Angiotensin-Aldosterone System (RAAS)

The Renin-Angiotensin-Aldosterone System, also called RAAS, is a hormone system that helps maintain blood pressure and blood volume.  RAAS is one of the most important regulatory systems of the body and I always joke that it is the only information you need to know to be a doctor (it is both a joke and not a joke...).

 

The steps of the RAAS are written out below and followed by an infographic:

1. The kidneys release renin due to decreased blood flow to the kidneys, low sodium detected by the kidneys, and/or decreased blood pressure to the kidneys
   
2. The renin converts angiotensinogen to angiotensin 1 in the bloodstream
   
3. Angiotensin 1 arrives at the lungs where the Angiotensin Converting Enzyme (ACE) converts angiotensin 1 to angiotensin 2
   
4. Angiotensin 2 has two effects: systemic vasoconstriction and the release of aldosterone from the kidneys
   
5. Aldosterone increases sodium reabsorption and potassium secretion in the kidneys
   
6. More water is reabsorbed into the body and less water is urinated out
   
   
   
   
   
   

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Why is RAAS Important?

The RAAS is extremely important for maintaining blood pressure in the body.  If blood pressure gets too low, the organs of the body will not be able to get all the blood flow they need for oxygen and nutrients.

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Explaination of Case Flow

  

Photo taken by a friend of Dr. Haus's

The sharing of educational materials is a large inspiration for this blog and the case series I am developing is the first type of education materials I plan on creating for this blog.  I want to outline the format for the cases so everyone can take part in this great opportunity to try, learn, and grow!

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The goal for the cases is for everyone to practice and learn.  This will be done through spending 3 days of blog posts to work through cases.  I highly recommend working through the cases with friends, family, pets, frenemies, mortal enemies, the wall, your invisible friend, etc.  The more you talk through these cases the more you will learn and the more you will be able to practice important skills such as problem-solving, communicating science, and thinking like a clinician. 

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I will be creating these blog posts to be accessible to anyone regardless of their scientific background.  All materials will be presented for three different levels to accommodate any learner at any stage of their journey. 

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If you have any cases, topics, or concepts that you want covered please comment them on the blog for inspiration!  Got an upcoming physiology exam and you have no idea what is going on with the renal system?  Let me know and I will put together materials to help!

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Now, let's jump in to understand the Case Flow!

Test Case Tuesday

On test case Tuesday, the initial information related to the patient's case will be shared.  Keep in mind, the species are not what is important - the important part is understanding the science behind the condition.  Animals are not as different from each other or humans as you may think.  If you are interested in veterinary medicine that is great.  If you are interested in human medicine that is great too - our pathophysiology/physiology is not all that different (especially amongst mammals).

At the end of test case Tuesday, you will not know the diagnosis of the patient but can take the time to create your differentials list and get excited for the Thoughtful Thursday blog post.  This is a great time to talk about the case with other people/animals/inanimate objects.

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Thoughtful Thursday

On thoughtful Thursday, the diagnosis and basic pathophysiology of the disease will be shared along with questions for each of the different levels of learning.  This is another great time to talk through the questions and answers.  You should take the time to think about how you would communicate this information to people of different scientific backgrounds especially if you are a "science person".  The medicine is the easy part, the hard part is communicating.

I believe much of the distrust of medical/science folks comes from our history of feeling as if we don't need to explain anything and that people should just blindly trust us.  That is not what we need to be doing as a scientific field - we need to work hard to practice communicating scientific information to folks without a scientific background.

Think about the cases, think about your answers, and take the time to look up any information you need to better understand the case, the questions, and the concepts.

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Conclusion Caturday

On Conclusion Caturday I will post the answers to the questions and links to further information based on the different levels of learning.  Take advantage of this time to check your answers, look up further information, and discuss this information with others.  I firmly believe you truly understand something when you can explain it to someone who does not have a strong foundation in the subject.

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Enjoy these cases as much as I enjoy creating them!

 

Dr. Haus's Unsolicited Life Advice Levels

  

Photo by Dr. Haus

Dr. Haus's Unsolicited Life Advice Levels

For this blog, some information will be presented or explained based on three different levels.  These different levels will help anyone have the ability to try, learn, and grow from the educational blog posts.

Remember, your level doesn't matter, the fact you are here is what matters (and I am glad you are here)! 

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Level 1

Level 1 materials are for folks who do not have a science background.  Maybe you haven't take a science class since middle school, maybe you forgot everything from your blow off general science elective from college.  Either way, I am happy you are here because you know a LOT more than you think.

 

Level 2

Level 2 materials are for folks who have some undergraduate science training.  Maybe you are a pre-health student, maybe you are taking science courses out of interest, or maybe you love to read about science.  I plan to prove to you that you know way more than your classes make you think you do.

Level 3

Level 3 materials are for folks who have a strong science background.  Maybe you are in a post-undergraduate health professional program, maybe you are getting your master's in science, or maybe you are a full-fledged health professional.  You can still learn here too and practice with your knowledge-base!  I highly recommend for folks in this category to work through these materials with colleagues and friends to get the most out of it.