Hypertension: Nursing pathophysiology

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Content Reviewers

Elizabeth Lucas, EdD, RN, CNE,Lisa Miklush PhD, RN, CNS,Maria Pfrommer, Ph.D., DNP, FNP-BC, RN

Hypertension occurs when the force of the blood pushing against the artery walls is too high, causing damage to organs.

Okay, so, as the heart pumps blood throughout the body, it creates pressure against the walls of the arteries, which is referred to as blood pressure, or BP.

Blood pressure is expressed as a fraction, where the top number, called the systolic pressure, represents the pressure in the arteries when the heart is contracting and pumping blood; and the bottom number, called the diastolic pressure, represents the pressure in the arteries when the heart is relaxed and filling with blood. Normal blood pressure is less than 120 mmHg systolic and less than 80 mmHg diastolic.

Factors that impact blood pressure include cardiac output, or CO, and systemic vascular resistance, or SVR. First, cardiac output is the quantity of blood pumped by the heart and is measured in L/min. The two components of cardiac output are stroke volume, or SV, and heart rate, or HR. Stroke volume is the amount of blood leaving the heart with each contraction, and heart rate is the number of contractions in one minute.

The higher the stroke volume and heart rate, the higher the cardiac output.

Next, systemic vascular resistance is determined by the radius and elasticity of blood vessels. If blood vessels are narrow or stiff, systemic vascular resistance increases, which then increases blood pressure.

Now, blood pressure is regulated by short-term and long-term mechanisms. Short-term regulation is mainly controlled by the autonomic nervous system, or ANS. For example, when changing from a lying to a standing position, blood pressure tends to drop.

When this happens, baroreceptors, which are pressure-sensitive receptors located mostly in the aortic arch and carotid sinuses, respond by sending signals to the vasomotor center in the medulla. The medulla activates the sympathetic nervous branch of the autonomic nervous system, which increases heart rate, systemic vascular resistance, and cardiac contractility. Together, these actions increase blood pressure.