Emergency Pharmacology: A Highlight on Vasopressors (Dopamine)

Vasopressors are life-saving drugs that are commonly seen in an emergency setting. But what are vasopressors, and what are their mechanisms of action?

Vasopressors Defined

Vasopressors are types of medications that exert pressure on the veins, on the vascular beds to promote vasoconstriction. When this happens, there is an increase in blood flow to the heart, lungs, and the brain. Aside from these organs, the kidneys are also directly affected by vasopressors.

Upon administration of vasopressors, the kidneys are alerted to hold all the fluid in the body or what is also known as fluid retention, causing dilation in the renal cavity or arteries; this will be explained further as we go along.

Examples of Vasopressors

There are many examples of vasopressors available in the market, but there are only two that are commonly utilized inside the hospital, especially in emergency scenarios. These drugs are:

  • Norepinephrine (Levophed)
  • Dopamine

Between the two, we’ll focus our attention on dopamine.

Dopamine

Dopamine is usually the first line of drug given to anyone who is suffering from hypotension.

Much like any other vasopressors, the introduction of dopamine is going to prompt vasoconstriction, putting pressure on the vessels. The primary goal for the administration of dopamine is to increase blood pressure. Aside from boosting blood pressure, dopamine can also inadvertently increase heart rate.

As mentioned, the kidneys are also going to be affected through perfusion, holding the fluid in to retain blood and distribute it to the rest of the body.

Hypotensive Crisis

Vasopressors are given especially during a hypotensive crisis. A hypotensive crisis is a situation wherein the body is losing a lot of blood drastically, which can either be caused by the following:

  • Trauma, example: gunshot wound
  • Excessive vomiting
  • Diarrhea

Any of these events can lead to hypovolemic shock, which is a deficiency of blood or fluids within the vascular spaces. If there is the extremely low amount of blood perfusion, it will compromise the distribution of oxygen. Remember, without oxygen, the body will eventually expire.

The Function of the Kidneys

So, during a hypotensive crisis, the kidneys will swoop in to save what is left of the little blood in the body by ceasing the mechanism of urination. The kidneys will not allow pee to go out of the body, keeping it inside the vascular spaces until blood pressure will rise naturally.

Route of Dopamine

Dopamine is usually given with an intravenous infusion as a piggyback or slow infusion; this will help increase blood pressure and dilate the renal arteries. This is true during emergencies.

Dopamine and ARF

Dopamine is also given to clients who are suffering from acute renal failure (ARF). When the kidneys are failing, dopamine will ignite the opening up of the renal arteries, causing more perfusion by shunting blood down to the kidneys so the client won’t go into chronic renal failure, and potentially losing the kidneys.

How does one determine that there is low perfusion in the kidneys?

The mean arterial pressure (MAP) determines how much blood flow is getting around the body. Normally the MAP is from 85 – 100. However, if there are problems with the kidneys, the MAP will go below 65. If this happens, the perfusion becomes compromised. To prevent this, dopamine is given.

For our next lecture, we’ll be focusing on the second vasopressor we’ve mentioned – norepinephrine (Levophed). Check it out in Simple Nursing’s website and YouTube channel.

Renal Function and Pathophysiology

After going through the three things that the kidneys filter, we’ll head on to what the kidneys produce that helps in creating red blood cells within the bone marrow. We’ll also tackle some of the kidneys’ main functions, with a bit of pathophysiology.

Let’s start.

Kidney Malfunction

If the kidneys are not working properly or are malfunctioning, there are a couple of components that will immediately get affected, mainly:

  • Hydrogen ions
  • Urea nitrogen (BUN)
  • Creatinine

These three components with an acronym, HUC, are expected to increase dramatically. Aside from these elements, hemoglobin and hematocrit levels will then decrease due to the inability of the kidneys to create erythropoietin.

Erythropoietin Defined

Erythropoietin is the hormone responsible for initiating the creation of red blood cells inside the bone marrow.

As nurses caring for clients who have renal failure and is undergoing peritoneal dialysis or hemodialysis, you have to anticipate that hydrogen ions, blood urea nitrogen, and creatinine are relatively high. The kidneys, due to its condition, are unable to get rid of these elements because urine is not coming out of the body.

High Blood Pressure

When a client with kidney disorder has increased blood pressure, it’s difficult to get rid of the fluid from the body to lessen the pressure. For this reason, hemodialysis is done.

Aside from hemodialysis, the client needs to be on fluid restriction because the fluid will stay inside the body and will not be eliminated immediately.

Understanding Kidney Structure

To know the primary function of kidneys, we must first go through its physiology.

As the filtering system of the body, you can consider the kidneys as washer machines. This washer machine filters the blood and gets rid of toxins and wastes that are excreted from the body in the form of urine. The nephrons are the basic working unit of the kidneys that do the filtering.

Filtering is done with the presence of glomeruli found inside the nephrons. These glomeruli branch out to the ends of the nephrons and are somewhat similar with an apple tree or bouquet of flowers.

Glomerular Filtration Rate

Blood goes through the nephrons and enters the glomeruli where they will be filtered. This process is called the glomerular filtration rate (GFR). Remember, the normal filtration rate is between 85 ml/min to 105 ml/min which translates to a healthy kidney that’s constantly working to filter hydrogen, urea nitrogen, and creatinine.

Inside the hospital, the bare minimum is around 65 ml/min.

The Geriatric Community

When geriatric clients reach the ages of 65 – 70, they tend to lose 3% of functioning nephrons yearly. Therefore, by the time they reach the age of 85, retention of proper kidney function will only be at 50%. This is the reason why the geriatric community experiences chronic health issues related to the heart, skin, and even the eyes.

Hyperglycemia and Hypertension

Hyperglycemia due to diabetes and hypertension are factors that precipitate kidney malfunction or breakdown.  

With hyperglycemia, the blood becomes thick and syrupy, like mud. If this mud-like consistency is pushed inside the kidneys and into the nephrons, there is an increased possibility that the kidneys (washer machines) will eventually malfunction.

Chronic hypertension, on the other hand, causes a consistent and long-term heightened pressure that affects the kidneys which can also lead to acute kidney failure.

In our next lecture, we’ll tackle the causes of acute kidney injury which leads a client to go into acute renal failure instantly.

Chronic Renal Failure & End-Stage Renal Failure

When talking about a disease that’s diagnosed to be chronic, it’s something that has been known for a while and has gotten to the point of progression; this is exactly what happens in chronic renal failure.

Here, we will be discussing the stages of chronic renal failure, its development, and fundamentally, how it worsens to end-stage renal failure.

Kidney Breakdown

Think of your kidneys as the washer or laundry machines of your body. Now, what happens if the organs responsible for cleaning your blood malfunction due to certain elements? Eventually, your kidneys will break down. Putting too much workload on your washer machines causes too much pressure that will destroy its overall integrity.

What are the main reasons for your kidneys to break down?

  1. Hypertension
  2. Hyperglycemia

So, if your client is either hyperglycemic, which is a condition wherein there is too much glucose in your blood, or hypertensive, the kidneys will collapse due to exhaustion of filtering all unnecessary components from your blood.

Situations inside the hospital can be much worse if your client has chronic congested heart failure and has high blood pressure. If this happens, the kidneys will be deprived of oxygen which can lead to necrosis.

Hyperglycemia + Hypertension = kidney breakdown = necrosis

Stages of Chronic Renal Failure

The first thing that would come to mind once you’ve been diagnosed with chronic renal failure is asking how severe the condition is. So, you’re primarily interested in the level of severity. This is where your staging comes in.

When knowing the stage of chronic renal failure, you are assessing how much percentage of your glomerular filtration rates are still working in terms of cleaning the blood and filtering the body’s waste products.

The stages of chronic renal failure are just identifying how much of your glomerular filtration rate is still working. Therefore:

  • Phase 1: 60% – 89% of the kidneys are not affected

Here, your kidneys are still in good condition because there’s only a small part of your glomerular filtration that’s not working. And since you’re on the first phase, lifestyle changes can still be applied to prevent progression to the succeeding stage.

But you have to keep in mind that when it comes to kidney failure, what was lost or destroyed cannot be regenerated unlike other organs in the body. The moment the glomeruli die, they’re dead forever.

For this reason, lifestyle and dietary changes are advised so as not to impair the rest of the kidneys further. If increased blood pressure and blood sugar are not controlled, the affectation will continue until the rest of the kidneys are destroyed entirely.

Phase 1 = requires lifestyle changes to prevent further destruction of the remaining healthy areas

  • Phase 2: 30% – 60% of the kidneys are not affected
  • Phase 3: 15% – 30% of the kidneys are not affected
  • Phase 4: End-stage renal failure

End-stage Renal Failure (ESRF)

In end-stage renal failure, only 15% of the kidneys are working but they will eventually fail, and it won’t take long until they deteriorate. Complete destruction of your kidneys is due to overworking and overcompensating for the increased pressure and blood sugar that’s flooding your washer machines and has fried the units entirely.

What is going to happen with a client who has an end-stage renal failure?

  • Decrease urine output
  • Increased toxins inside the body
  • Fluid volume overload

Two Options to Consider

Clients who have end-stage renal failure have two options that they can consider:

  1. Dialysis – You can either choose from:
  • Hemodialysis – a procedure wherein a shunt is inserted in the arm
  • Peritoneal dialysis – placing fluid in the peritoneal space
  1. Kidney transplant

The problem with kidney transplants is that most of the time, it does not go well. There is a considerable possibility that the body will reject the transplanted kidneys which will is why clients are required to take immunosuppressant medications to prevent the client’s immune system from attacking the new organs. This is one of the primary side effects of getting a transplant.

On our next lecture, dialysis will be discussed thoroughly. For other essential nursing topics, visit simplenursing.com.

Until next time!

Renal Function Patho: Getting to Know Your Kidneys

Renal failure – an exam favorite and one of nursing students’ worst nightmare. If renal failure is making you anxious, let SimpleNursing.com make it stupidly simple for you.

But first, let’s go to the basics – kidney function and location.

Whenever you hear the word “kidneys” there should be a light bulb inside your head that immediately triggers you to think about the fundamental pathophysiology happening inside those two bean-shaped structures inside your body. Let’s break it down effortlessly.

The Washer Machines

As previously stated, the kidneys look like two beans which are connected to the aorta and have renal arteries. Now, think of your kidneys as washer machines. Never mind the glomerular filtration rates or nephrotic syndrome or those complicated terms that you’ve acquired from reading your nursing books. All you have to think about at this moment is how your kidneys are washer machines in your body.

The primary function of your washer machines is to wash (filter) your blood, making sure it’s clean before it goes into the different parts of the body. As clean blood is being distributed to the entire system, dirty blood becomes urine and is eliminated down the ureters to the bladder and finally, to the potty.

From the wise words of Mike’s instructor: “Into the potty and not the body.”

Get The HUC Out of Here

Basically, there are three main elements that kidneys filter and they go by the acronym: HUC. What does HUC stands for?

  • H – Hydrogen Ions
  • U – Urea
  • C – Creatinine

Hydrogen Ions

One word: very acidic. Hydrogen ions are the by-product of H2O (water) – two hydrogen and one oxygen atoms.

While the body utilizes oxygen, it needs to get rid of the hydrogen from the blood and into the potty. Why? Because if your washer machines are broken, hydrogen with not be properly filtered and will not be eliminated from the body. This will cause acid build-up that will lead to metabolic acidosis. Therefore:

  • Increased hydrogen = metabolic acidosis

Urea

How is urea created?

From the small intestines, specifically the duodenum, protein is broken down. Think of protein as a protein bar that comes in with a wrapper. The body absorbs the protein while the wrapper becomes ammonia. Ammonia goes into the liver and is broken down in the form of urea. Urea is then sent through the exit portals of the liver to the washer machines to be appropriately filtered and be excreted by the body.

If the washer machines are broken, there will be a build-up of urea (uric acid) and is evidenced by your blood urea nitrogen (BUN). Therefore:

  • Increased urea = increased BUN

Take note: When BUN is increased, it doesn’t automatically indicate renal failure. There is a high possibility that your client is just dehydrated. This happens when the person has been exposed to the scorching heat of the sun for quite some time; the person becomes hemo-concentrated which results to the very high BUN. You can remember that through “very burned BUNs.”

So you’re wondering what happens if BUN and creatinine are both elevated? Read on.

Creatinine

Creatinine is the by-product of muscle metabolism. This does not mean rhabdomyolysis or the rapid breakdown of your muscle. Having creatinine in the body only means that there is constant and healthy muscle tissue break down and the end-product is creatinine. When the washer machines are broken, creatinine level in the urine is low because it’s stranded inside the body.

Again, from the wise words of Mike’s instructor: “Into the body and not the potty.”

To answer what happens when both BUN and creatinine are elevated:

  • Increased BUN and creatinine = possible kidney failure

What are the stages of progression of kidney failure regarding acute renal failure? That will be discussed in our following video that’s mainly dedicated to the condition: acute renal failure.

See you in our next video!

Renal Labs: Uncomplicated BUN and Creatinine Interpretation

Today, Mike Linares will teach you about one of the favorite topics in nursing exams – BUN and creatinine.

Let’s begin.

The kidneys’ primary function is mainly to filter the following:

  1. Hydrogen ions
  2. Urea
  3. Creatinine

You can easily remember this because your kidneys look like a hook; so that’s HUC (pronounced as “hook”).

Hydrogen ions are acidic. Therefore, with clients who have renal failure, they will be experiencing metabolic acidosis because the kidneys have increased hydrogen ions.

Urea is the by-product or waste product of ammonia that is detoxified into the liver, then goes into a portion of the portal vein and is finally sent to the kidneys for filtering. Once filtered, urea is excreted out of the body in the form of urine. BUN (blood urea nitrogen) technically means the amount of urea concentration in the blood.

Creatinine is the by-product of muscle breakdown. Creatinine is filtered by the kidneys and is also passed out from the body as urine.

Normal Levels

Kidneys filter out creatinine and BUN; this is evident in a metabolic panel. What we want to see in our metabolic panel for creatinine and BUN is a good ratio. This means that normal laboratory values should show as:

  • Creatinine – 0.7 to 1.2 mg
  • BUN – less than 20 mg/dL

Acute Renal Failure

In acute renal failure you have to identify the following indicators:

  1. Urine output – how much pee the client has excreted
  2. Glomerular filtration rate (GFR) – how fast glomeruli (the little washer machines) in the kidneys wash blood milliliters per minute. Normal GFR should be between 85 to 110 mL/min. Acute renal failure clients will show a GFR of less than 60.
  3. BUN and creatinine ratio – if creatinine and BUN have increased ratio. A creatinine that shows more than 1.2 mg will equate to a BUN that’s thrice as much. Example, if you have a creatinine level of 3 mg, your BUN will be 60 mg/dL.

To explain further, the body filters typically creatinine and BUN. However, the most significant indicator for kidneys failing in its primary function (filtering), is the presence of high creatinine. This is because BUN can be high in the body but not in the potty. This could just mean that you are just dehydrated. To remember this, keep in mind that your “BUNs get burned” when you are dehydrated.

Now, if your BUN and creatinine are both increased, you have kidney involvement. If in case you are still confused with kidney involvement, just remember this by recalling that you have two kidneys, therefore, two lab values should both be increased. If you only have “burned BUNs,” then you’re probably just dehydrated.

In the other lectures, we will have a comprehensive discussion on the topics of:

  • Acute renal failure
  • Chronic renal failure
  • Creatinine ratios
  • Oliguric phase
  • Diuresis phase
  • Recovery phase from acute renal failure
  • Recovery phase from intrarenal and extrarenal
  • ABGs with renal failure (sodium, calcium, potassium phosphate)

If you want to check out other topics that commonly show up in nursing exams, visit SimpleNursing.com.