Blood Pressure Crash Course for nurses

Blood pressure is one of the 5 vital signs, and it is so important to understand what normal and abnormal blood pressures are, and how we manage them (don’t get me started on the “6th” vital sign…).

Within the hospital, vital signs are typically checked every 4 hours, and you will frequently run into both high and low blood pressures.

Low blood pressure is often much more worrisome, and you may want to call an RRT if the BP is significantly low, especially when the patient is altered or has significant symptoms.

High blood pressure is common, but often is not considered a big deal unless VERY high. In these cases, we want to slowly decrease the blood pressure instead of too quickly.

As we said above, systolic is the pressure during contraction of the heart, and diastolic is the pressure in-between beats. When looking at a blood pressure reading, there are two numbers: a numerator and a denominator. The numerator or top number is the systolic blood pressure. The denominator or the bottom number is the diastolic blood pressure.

Normal systolic blood pressures are between 100 – 120 mmHG. Normal diastolic pressures are between 60-80 mm Hg. Traditionally 120/80 mmHg was considered the “gold standard” for blood pressure, but now its recommended to be at most 120/80 mmHg. 

We check people’s blood pressures in the hospital, in the outpatient office setting, and pretty much every area of patient care. Nowadays, we have machines that do most of it for us. But machines aren’t perfect, and its an essential nursing skill to know how to check blood pressure.

In general, there are 3 main ways to check someone’s blood pressure:

If you’ve been working for a bit, or in clinicals, you may hear about the term “MAP”. While systolic blood pressure is often considered the most important part of the blood pressure, the actual important number is the MAP. 

The MAP stands for Mean Arterial Pressure. This is the average pressure in the arteries from one cardiac cycle (systolic + diastolic). This is measured by a calculation:

But don’t go busting out your calculators. The bedside monitors should automatically calculate this for you, or possibly your EMR. If you need to calculate it, there are plenty of good online calculators to quickly do it. 

MAP is a great indicator of tissue perfusion. If the MAP stays above 65 mmHg, then this should be enough pressure to provide essential tissue perfusion and prevent anoxic injury (injury from a lack of oxygen to the cells!).

Nurses and Providers in the ICU will care much more about MAP than systolic blood pressure, especially when looking at low blood pressures.

Hypertension can be chronic or acute. Its also important to know if the patient is having any symptoms such as chest pain, SOB, headache, etc.

3 main types of hypertension that we’ll talk about include:

Treatment of Hypertension:

Treatment of hypertension is often not aggressive, and is often made by slow gradual changes to outpatient medication regimens.

However, if the patient is symptomatic, blood pressure medications should be given. 

At home blood pressures should be checked, as patients BPs are often higher in emergency and urgent care settings, and “White coat hypertension” is common. 

Some oral medications used to lower BP include:

• ACE Inhibitors like Lisinopril
• ARBs like Losartan
• Calcium channel blockers like Amlodipine
• Beta-blockers like Labetalol
• Diuretics like Hydrochlorothiazide
• Alpha blockers like Clonidine

In hypertensive urgency and when in the hospital, sometimes IV medications may be required including:

• IV Hydralazine
• IV Cardizem or Nicardipine
• IV Labetalol
• IV Lopressor (metoprolol)

In general, blood pressure should never be lowered too fast. In severe cases, the goal should be to lower the MAP by 10-20% within the first hour, then another 5-15% over the next day. In many cases, this is less than 180/120 in the first hour, and less than 160/110 after 24 hours. 

Lowering the blood pressure too quickly can actually cause ischemic damage in patients who have had elevated blood pressure for a long time. Basically the body becomes used to that high pressure, and while it is dangerous to have high blood pressure in general, lowering it too quickly can cause damage as well.

Hypotension is when the blood pressure is too low. Low blood pressure is defined as any pressure less than 100/60 mmHg. However, this is often not considered true hypotension until below 90/50 mmHg.

Patients who are small in stature and thin may have borderline low blood pressures at baseline.

Remember if the MAP is less than 65 mmHg, this places the patient at risk for tissue ischemia and organ damage. 

Low blood pressure is often a serious sign, especially in the hospital setting. Common causes of hypotension include:

Treatment of Hypotension:

Treatment of hypotension will involve treating the underlying cause, but generally involves 2 steps:

• IV Fluid boluses: to increase the volume of the blood
• Vasopressors: To cause constriction of the blood vessels

If fluid boluses do not improve blood pressure, or if the BP drops back again once its done, then the patient may need vasopressors in the ICU.

Depending on the cause, the underlying cause should be addressed, including:

• Blood for blood loss
• Antibiotics and fluids for sepsis
• Steroids for adrenal crisis
• Steroids & Antihistamines for Anaphylaxis

You are going to run into TONS of patients who either have high blood pressure, or low blood pressure. Managing vital signs is a huge part of our jobs as nurses and doctors, and its so important to understand how to manage blood pressure!

Remember these important concepts when it comes to blood pressure: