Week 3 - Chapter 16: Alterations of Blood Pressure

Arterial Blood Pressure

• Blood pressure is the pressure difference between the left and right sides of the heart, creating a gradient for blood flow throughout the system.
• Arterial blood pressure is the force of left ventricular contraction overcoming the aorta's resistance, leading to aortic valve opening.
• Cardiac output (CO) is the product of stroke volume (SV) and heart rate (HR).
• End-diastolic volume (preload) is a determinant of CO.
• Systemic vascular resistance (afterload) depends on the arteries' radius and vessel compliance.
• Systolic blood pressure is the peak pressure during cardiac systole.
• Diastolic blood pressure is the lowest pressure during cardiac diastole.
• Stroke volume (SV) impacts systolic pressure.
• Systemic vascular resistance (SVR) is crucial for diastolic pressure.

Direct Measurement of Arterial Blood Pressure

• Intraarterial catheterization measures arterial blood pressure.
• Catheter is often in the radial artery.
• It's the most accurate method.
• Fluid pulsations are translated into electric signals (waveforms).

Indirect Measurement of Arterial Blood Pressure

• Common method is using a sphygmomanometer and stethoscope or an automated oscillometric system on the brachial artery.
• Techniques must be precise for accurate readings.
• Korotkoff sounds are crucial components of this method.

Mechanisms of Blood Pressure Regulation

• Neural, humoral, and renal factors affect blood pressure.
• Physiologic changes, like circadian rhythm, affect the fluctuations in blood pressure.

Short-Term Regulation of Systemic Blood Pressure

• The sympathetic nervous system mediates BP changes.
• Release of epinephrine and norepinephrine is a result.
• Baroreceptors indirectly stimulate the vasomotor center.
• α receptors in arteriolar smooth muscles are activated.
• β receptors in the heart are activated.

Long-Term Regulation of Systemic Blood Pressure

• The renin-angiotensin-aldosterone system is key.
• Angiotensinogen is converted to angiotensin I, then angiotensin II by renin and angiotensin-converting enzyme.
• Angiotensin II causes vasoconstriction and aldosterone release.
• Increased sodium and water retention leads to an increased blood volume.
• This ultimately increases blood pressure.

Hypertension

• It's the most common primary diagnosis in the U.S.
• It contributes to heart disease, kidney disease, peripheral vascular disease, and stroke.
• Globally, it causes 7 million deaths annually.

Definition and Classification of Hypertension

• The JNC 7 committee defines hypertension and prehypertension ranges.
• Prehypertension is used to catch the condition earlier than stage 1 hypertension.
• This gives individuals more time to initiate lifestyle or drug interventions.
• Classification is based on systolic and diastolic blood pressures.

Blood Pressure Classification in Adults

• A table gives ranges for normal, prehypertension, stage 1, and stage 2 hypertension.

Primary Hypertension

• It's the most common type, often idiopathic (no known cause).
• It rarely appears before age 10.
  • Subtypes: isolated systolic, isolated diastolic, and combined systolic/diastolic hypertension.

Risk Factors of Primary Hypertension

• Nonmodifiable: Family history, age
• Modifiable: Diet, sedentary lifestyle, obesity, metabolic syndrome

Outcomes of Primary Hypertension

• End-organ damage (e.g., heart failure, kidney failure).
• Potential for hemorrhage in the brain.
• Microcirculation damage in the eyes.

Hypertension-Atherosclerosis

• Increased myocardial work, left ventricular hypertrophy.
• Increased pressure and decreased blood flow in various parts of the body lead to related complications.
• Consequences of the disease can include stroke, ischemia, aneurysms.

Treatment Interventions for Primary Hypertension

• Lifestyle modifications are the initial and most important intervention.
• Drug therapy is further used to manage heart rate, systemic vascular resistance, and blood volume.

Lifestyle Modifications to Prevent and Treat Primary Hypertension

• Weight reduction, DASH diet, sodium reduction, regular exercise, and moderate alcohol consumption are recommended to manage the condition.

Secondary Hypertension

• It's linked to a specific underlying condition or pathology.
• Often evident in children under 10.
• Possible causes include renal disease, coarctation of the heart, pregnancy, obesity/obstructive sleep apnea, and endocrine disorders.

Hypertensive Emergencies and Urgency

• Emergency: A sudden significant increase in blood pressure with end-organ damage needing rapid, controlled reduction via parenteral antihypertensives under ICU monitoring.
• Urgency: Similar blood pressure elevation without evidence of end-organ damage. Oral medications are used for gradual normalization over 24-48 hours.

Low Blood Pressure

• Orthostatic (postural) hypotension is a decrease in systolic blood pressure by at least 20 mmHg (or 10 mmHg) in 3 minutes when moving to an upright position.
• Excessive tachycardia (20 to 30 beats per minute) can be diagnostic.
• Possible causes include vasomotor or baroreceptor problems, drug side effects, arterial stiffness, volume depletion, and secondary diseases.

Treatment for Low Blood Pressure

• Review current medications.
• Slow transitions between positions.
• Avoid hot environments.
• Avoid high carbohydrate and heavy meals.
• Position changes like squatting, bending or crossing legs may be helpful for symptom relief.