Hypertension and Blood Pressure Management

Blood pressure is defined as the force exerted by the blood against the walls of the blood vessels.
Blood pressure (BP) is represented by two specific numbers that correspond to the pressures exerted during different phases of the heart's activity:
- Systolic Pressure: The maximum pressure occurring during systole, or the phase of contraction, of the ventricles.
- Diastolic Pressure: The pressure occurring during diastole, which is the period of relaxation and filling of the ventricles.

BP is regulated through three primary physical systems:
- Autonomic Nervous System (ANS)
- Kidneys
- Endocrine System (hormonal control)
Autonomic Nervous System Regulation:
- Uses Baroreceptor-Initiated Reflexes: These receptors are located specifically in the Aortic Arch and the Carotid Arteries.
- Uses Chemoreceptor-Initiated Reflexes:
  - Peripheral Chemoreceptors: These are sensitive to hypoxemia. When stimulated, they cause systemic vasoconstriction and a subsequent increase in BP.
  - Central Chemoreceptors: These are located in the brain and are sensitive to hypercapnia. Their effect is notably strong, measured at approximately $10\times$ stronger than peripheral chemoreceptors.

Epinephrine and Norepinephrine:
- These hormones are secreted from the Adrenal Glands.
- They stimulate the Sympathetic Nervous System (SNS).
- Physical effects include an increase in heart rate ( $HR$ ) and peripheral vasoconstriction.
Acetylcholine:
- This neurotransmitter is associated with the Parasympathetic Nervous System (PNS).
- Its stimulation causes a decrease in heart rate ( $HR$ ) and triggers the vasodilation of the arteries.

The purpose of blood pressure guidelines is to decrease the overall risk of cardiovascular (CV) disease. Classification is based on the following thresholds:
Normal BP:
- Systolic BP ( $SBP$ ): < 120
- Diastolic BP ( $DBP$ ): < 80
Elevated BP:
- $SBP$ : $120$ to $129$
- AND
- $DBP$ : < 80
Stage 1 Hypertension:
- $SBP$ : $130$ to $139$
- OR
- $DBP$ : $80$ to $89$
Stage 2 Hypertension:
- $SBP$ : $\geq 140$
- OR
- $DBP$ : $\geq 90$
Hypertensive (Malignant) Crisis:
- Blood pressure values exceeding $\frac{180}{120}\,mmHg$

Systemic Vascular Resistance is defined as the force opposing the movement of blood within the blood vessels.
Factors determining vascular resistance:
- The primary determinant is the width or radius of the small arteries and arterioles.
- Vasoconstriction: If the vessels become smaller (radius decreases), the SVR increases.
- Vasodilation: If the vessels become larger (radius increases), the SVR decreases.

Primary (Essential) Hypertension Risk Factors:
- Age greater than $60$ years.
- Family history of hypertension.
- Overweight or obesity status.
- Physical inactivity.
- Excessive intake of alcohol.
- Hyperlipidemia.
- African-American ethnicity.
- High dietary intake of sodium or caffeine.
Secondary Hypertension Causes:
- Renal disease.
- Primary aldosteronism.
- Pheochromocytoma.
- Cushing's syndrome.
- Specific medications.

Comprehensive Patient Assessment:
- Patient medical history.
- Physical assessment.
- Psychological assessment.
- Diagnostic assessment.
Lifestyle Changes for HTN Management:
- Sodium restriction.
- Weight reduction.
- Moderation of alcohol intake.
- Regular exercise.
- Relaxation techniques and stress reduction.
- Smoking cessation.

Mechanism: All diuretics produce a decrease in blood volume through the excretion of water.
Specific Classes and Examples:
- Thiazide Diuretic: Hydrochlorothiazide.
- Potassium-Sparing Diuretic: Spironolactone (Aldactone).
- Loop Diuretic: Furosemide (Lasix).
Nursing Considerations:
- Monitor for hypotension.
- Monitor for hypokalemia (low potassium).
- Monitor uric acid levels.
- Administer medications early in the day to prevent nocturia.
- Monitor blood glucose levels.

Medication Examples:
- Diltiazem (Cardizem).
- Amlodipine (Norvasc).
- Verapamil (Calan).
- Nifedipine.
Mechanism of Action:
- They inhibit $Ca^{2+}$ from entering cells, which reduces muscular contraction.
- They relax smooth muscle, thereby lowering peripheral resistance.
- They decrease the demand for oxygen by the heart.
Side Effects and Alerts:
- Can cause decreased BP and bradycardia.
- May precipitate an A-V block.
- Side effects include headache, abdominal discomfort (constipation, nausea), and peripheral edema.
- Grapefruit juice must be avoided as it enhances the absorption of these drugs.

ACE Inhibitors:
- Drugs include Captopril (Capoten), Enalapril (Vasotec), Lisinopril (Zestril), and Benzapril (Lotensin).
- Mechanism: Prevents the conversion of Angiotensin I to Angiotensin II; reduces peripheral vascular resistance without significantly altering cardiac output, rate, or contractility.
- Side Effects: Common nonproductive dry cough, dizziness, orthostatic hypotension, gastrointestinal distress, and headache.
- Life-Threatening Risks: Angioedema, neutropenia, and hyperkalemia.
Angiotensin II Receptor Blockers (ARBs):
- Drugs include Losartan (Cozaar) and Valsartan (Diovan).
- Mechanism: Directly blocks the receptors for Angiotensin II.
- Side Effects: Very few side effects except for hypotension and hyperkalemia.

Medication Examples:
- Atenolol (Tenormin).
- Metoprolol (Lopressor, Toprol).
- Propranolol (Inderal).
- Carvedilol (Coreg).
Mechanism of Action:
- Work by decreasing heart rate ( $HR$ ) and contractility, which subsequently decreases cardiac output ( $CO$ ) and blood pressure ( $BP$ ).
- Eases the total workload on the heart by blocking beta receptors.
- Impacts: $\downarrow HR$ , $\downarrow \text{Force of Contraction}$ , and $\downarrow \text{Rate of A-V Conduction}$ .
Clinical Considerations:
- Monitor for bradycardia and orthostatic hypotension.
- Nursing Hold Rule: Hold the medication if SBP < 100 or HR < 60.
- Use with caution in patients with Diabetes Mellitus (DM).
- Side effects can include lethargy, GI disturbance, potential Congestive Heart Failure (CHF), and depression.
- Beta-1 blockers primarily affect the heart, while Beta-2 blockers affect the lungs.