Blood Pressure: A Crash Course for Nurses

William Kelly, MSN, FNP-C

Updated June 2026

12 min read

Blood pressure is one of the five vital signs, and knowing what's normal, what's not, and how we manage each is core to bedside nursing. In the hospital, vitals are usually checked every 4 hours, and you'll run into both high and low readings constantly.

Low blood pressure is often the more worrisome of the two, and you may want to call an RRT if it's significantly low, especially when the patient is altered or symptomatic. High blood pressure is common and usually not an emergency unless it's very high, where the goal is to bring it down slowly rather than too fast.

What Is Blood Pressure?

Blood pressure isn't the pressure of your blood — it's the pressure within your vascular system. When we talk about systemic blood pressure, we mean the pressure inside the arteries, which rises with each heartbeat and falls in between.

The pressure in the arteries while the heart contracts is the systolic pressure (the top number). When the heart relaxes between beats, the pressure settles to its baseline — the diastolic pressure (the bottom number). Systolic is always higher than diastolic, and diastolic should never read 0. Both are measured in millimeters of mercury (mmHg).

"Normal" Blood Pressure

A normal systolic runs roughly 100–120 mmHg and a normal diastolic 60–80 mmHg. The old "gold standard" of 120/80 is now framed as an upper limit — you want to be at or below 120/80.

How to Measure Blood Pressure

We check blood pressure everywhere — the hospital, the clinic, and just about every patient encounter. Machines do most of the work now, but they aren't perfect, and knowing how to do it yourself is an essential nursing skill. There are three main methods:

Manual Blood PressureSphygmomanometer + stethoscope

Place the stethoscope over the brachial artery and the cuff on the bicep. Pump the cuff to about 160–180 mmHg (higher if the BP is very high), then slowly release while you auscultate. The first Korotkoff sound is the systolic; the point where the sounds disappear is the diastolic.

Automated Blood PressureDinamap or bedside monitor

A machine essentially performs a manual BP on its own using oscillometry. A sensor detects tiny oscillations from your pulse — when the pulse vanishes, that's the systolic; when it returns, that's the diastolic.

Arterial LineMost accurate, ICU

An a-line measures pressure directly from inside the artery via a sensor, rather than indirectly like the methods above. It's the most accurate option and gives real-time changes, which is why it's common in the ICU for strict monitoring.

What Is the "MAP"?

Once you've been at the bedside a while, you'll hear about the MAP. While systolic gets most of the attention, the MAP is often the number that actually matters. MAP stands for Mean Arterial Pressure — the average pressure in the arteries across one cardiac cycle.

Don't reach for a calculator, though — the bedside monitor calculates MAP for you, as does most EMRs, and there are quick online calculators if you need one. MAP is a great marker of tissue perfusion: keeping it above 65 mmHg generally provides enough pressure to perfuse the organs and prevent anoxic injury. In the ICU especially, providers care far more about MAP than systolic when the pressure is low.

Hypertension

Hypertension — high blood pressure — is often dismissed as "no big deal," but it's a genuine silent killer. Over time it strains the heart, vasculature, and kidneys, raising the risk of heart disease, stroke, and kidney failure. It's called silent because it's usually asymptomatic, which doesn't make it any less dangerous in the long run.

The current ACC/AHA (2017) guideline classifies blood pressure into four categories:

Hypertension can be chronic or acute, and it's always worth asking about symptoms like chest pain, shortness of breath, or headache. Here are the three forms you'll hear about most:

Primary HypertensionFormerly "essential" HTN

Chronic high blood pressure with no single clear cause, thought to involve genetics, diet, and lifestyle. This is what most people with HTN are diagnosed with. Risk factors include:

• Older age
• Obesity
• Family history of HTN
• Black race
• High-sodium diet
• Excessive alcohol
• Sedentary lifestyle

Hypertensive Urgency> 180 / 120 mmHg, no organ damage

A very high pressure (> 180/120 mmHg) without evidence of organ damage — no concerning symptoms or lab abnormalities — but the patient is at risk for organ damage or stroke.

Hypertensive Emergency> 180 / 120 mmHg WITH organ damage

The same very high pressure (> 180/120 mmHg) but now there is evidence of end-organ damage. Look for at least one of:

• Chest pain or shortness of breath
• Pulmonary edema
• Severe headache, seizures, or confusion
• Elevated troponin
• Acute kidney injury (rising creatinine)

Treating Hypertension

Treatment is often not aggressive — usually slow, gradual adjustments to an outpatient regimen. If the patient is symptomatic, BP meds should be given. And because pressures run higher in urgent and emergency settings ("white coat hypertension" is common), home readings matter for the real picture.

Hypotension

Hypotension is when the blood pressure is too low — technically anything under 100/60 mmHg, though it's often not treated as true hypotension until below 90/50 mmHg. Patients who are small and thin may simply run borderline-low at baseline.

Remember, a MAP under 65 mmHg puts the patient at risk for tissue ischemia and organ damage. In the hospital, low blood pressure is often a serious sign. Common causes include:

Sepsis

Persistent hypotension despite a 30 mL/kg fluid bolus. Needs pressors, a central line, IV antibiotics, and the ICU.

Anaphylaxis

Distributive shock from a severe allergy — massive vasodilation and swelling. Treat with epinephrine, steroids, and antihistamines.

Hemorrhage

Enough blood loss drops the pressure. These patients need STAT blood, often uncrossmatched O negative.

Cardiogenic Shock

The heart can't keep up with demand — seen in severe CHF or bradyarrhythmias.

Medications

BP meds at the wrong dose (or toxic levels) can over-shoot. Others, like amiodarone, list hypotension as a side effect.

Adrenal Insufficiency

A history of adrenal insufficiency often calls for stress-dose steroids to hold the pressure up.

Severe Dehydration

Has to be severe before pressure drops — think DKA, diabetes insipidus, or anything causing major fluid loss.

Treating Hypotension

Treatment always means addressing the underlying cause, but it generally starts with two steps:

From there, match the treatment to the cause:

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