One of the cool things I get to do as an APPE pharmacy student at a primary care rotation is take blood pressures. I was never good at it in the past. I fumble with the cuff, always pick the wrong size, and usually make myself look like I just learned yesterday. Good news is, when you do something multiple times a day, every day, you start to get better. So it looks like I'm on my way to blood pressure pro status.

ANYWAY, today I decided to do a post about blood pressure. High blood pressure, or hypertension, is everywhere (in fact, one out of three Americans has high blood pressure!), and it complicates just about everything. I get a lot of questions from my non-medical friends about what blood pressure is, what it does, and how to prevent it. On the other side, the question for us in medicine usually is: what is the patient's goal, and which guideline!?


Pathophysiology
Overall, there are many mechanisms that go awry in patients with essential hypertension. It is first important to understand the different between your SYSTOLIC blood pressure (SBP) and your DIASTOLIC blood pressure (DBP). Both of these represent the pressure on the arterial wall when blood pumps through.

SBP: the pressure at the peak of heart contraction
DBP: the pressure after contraction when the chambers of the heart are filling with blood

During the whole cardiac cycle, we spend more time, 2/3 of the time, filling the heart (or in diastole) than in systole. SBP is usually determined by your cardiac output, or how much blood your heart is putting out into the body. DBP is usually determined by what is called systemic vascular resistance, a term used to define how difficult it is for your body to actually bump that blood out. Both CO and SVR are really important factors in the development of hypertension, because when things go wrong with them the body has a series of compensatory mechanisms it turns on to try to get CO and SVR back to normal.

When you have an increase in your CO, it makes sense that your blood pressure increases. More blood pumping out of your heart, more volume that has to fit through your arteries, and that leads to more pressure on the walls of those arteries! So what leads a person to have an increased CO?  One of the mechanisms is an increase in the blood in your heart's preload, or the amount of blood in the heart right before it contracts. More in = more out. This can happen due to an increase in your sodium intake, or problems with your kidney's ability to kick sodium out of the body. Where sodium goes, water follows, always! This one of the ways poor diet can result in high blood pressure. Poorer diets tend to be fully of salty foods, and eating all this salt attracts water, which affects your heart because suddenly theres a lot more blood than it is used to!

An increased CO can also happen when you have an increase in the constriction of your veins, the vessels bringing blood back to the heart. Remember I mentioned our bodies have compensatory mechanisms for when things get weird in the body? Well these are activated when our pressure is too low or too high. We have receptors and cells in our heart and kidneys that are meant to detect these changes, and get us back to our normal. After a while though, the increased stimulation of these pathways causes them to activate when they're not needed. The main two are the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system (which controls the release of norepinephrine). Both of these systems release hormones, angiotensin II and norepinephrine, whose goal is to increase the blood pressure. Now in a situation where you are severely dehydrated and have low blood volume, this is great! This keeps you alive! But when these are being inappropriately released and cause constriction and ultimately an increased CO, this is bad.

The inappropriate action of these two systems also causes increased SVR as well. These hormones increase constriction, increased constriction means trying to fit a whole lot of blood through a way tinier vessel than your body is used to, which means it is also way harder for your body to get it through. Thats increased SVR! These hormones also cause an increase in structural hypertrophy from repeated activation. This means the cells get larger and grow more. The vessels become rigid, and narrow. Because of this, they are less likely to respond appropriately to changes in blood pressure.

Risk factors
So how exactly does this all start? How do external factors and your every day life play a role? And more importantly, who is at risk?

• Age >45yo men and >65yo women
• Having diabetes
• Increased cholesterol
• Race (black or hispanic individuals especially)
• Family history
• Being overweight or obese
• Using tobacco
• Physical inactivity
• Diet (too much sodium, too little potassium)
• Drinking too much alcohol
• Stress

Source: CDC

Symptoms
Usually people don't have any! High blood pressure is often known as a silent killer because you usually don't experience any symptoms until it is too late, meaning until you already have organ damage. See below.

Complications
So what is the big deal about high blood pressure, right? Why do we care? We care because of the long term complications. Your body can only keep up with a state of high blood pressure for so long before your organs start to suffer the consequences:


Preventing high blood pressure
There are certain risk factors you can change, and ones you can't. You can't change your age, or your genetics, but you can change your diet and your physical activity! Eating a well-balanced diet is key, and that means keeping how much sodium you consume <2.4g. Processed and prepackaged foods are notorious for being full of salt, and while its hard to cut salt out at all, its important to be vigilant about how much you're consuming. Limiting alcohol is something you also have control over. It's recommended that men drink <2 drinks per day, and women <1. The AHA recommends 150 min of moderate-intensity exercise a week, so whether its parking a little farther away from work or going on post-dinner walks, it is important to try to get that in. Shedding 10 lbs and keeping up with consistent exercise is known to work magic on blood pressure.

Different goals
Now this is probably where every non-medical student tunes out. There are many guidelines and therefore blood pressure goals for individuals out there. How do you know which to use!? It really is patient specific.

JNC8
-Summary algorithm
-The guidelines

I typically gravitate toward JNC8 when I have a patient without any other conditions. So I use it for my patients who don't have heart disease, kidney disease, or diabetes, but do have hypertension.

The guideline goal recommendations: If you're greater than 60yo your goal is <150/90, if you're literally anyone else its <140/90. Look at the summary algorithm above for a great picture analysis, I have this printed and kept in my white coat pocket because it is so fantastic.

American Heart Association
-The guidelines

For my patients with heart disease as their primary problem, I use the AHA guidance for blood pressure goals. This includes patients with heart failure, coronary artery disease, and acute coronary syndrome.

The guideline recommendations: If you have CAD, ACS or HF your goal is <140/90, if you have CAD and are post-heart attack, stroke, TIA, have carotid artery disease, PAD or abdominal aortic aneurysm, your goal is <130/80.

American Diabetes Association
-The guidelines

This is becoming kind of obvious right? I go here for my patients with diabetes.

The guideline recommendations: If you just have plain 'ol diabetes it's <140/90, but if you have diabetes, protein leaking from your kidneys or you also have ASCVD risk factors, go with <130/80

KDIGO
-The guidelines

If your patient has chronic kidney disease, you want to go to KDIGO. If they have pretty simple CKD your goal is <140/90, and if you have protein in your urine its going to be <130/80.


The bottom line

So what if you have a patient with hypertension, diabetes AND chronic kidney disease!? That is the patient I see just about everyday. This is where professional judgement comes in. Right now there is no ultimate guideline that says "LOOK HERE" for your complicated patient. It really just depends on their clinical picture and what you think they can tolerate (remember, pushing too low can be dangerous!). Luckily, a lot of the recommendations do overlap and it makes it easier for those with a lot of complications from their disease states. JNC8 included a nice table summary in their guidelines of all the other guideline recommendations. I highly advise printing it and keeping it with you if you can:



Thats about it for my review! I hope this was helpful. It is so important for patient and provider to fully understand high blood pressure and the consequences it can have if left uncontrolled. It is a modifiable risk factor in many diseases and if controlled can lead to a lot better outcomes for our patients.

A final disclaimer: this is not supposed to be completely comprehensive and is just supposed to serve as a simple review. Feel free to leave any comments or suggestions below!