24.19: Blood Pressure Imbalances and Circulatory Shock
Disorders affecting blood volume, vascular tone, or vascular function can disrupt vascular homeostasis, including conditions like hypertension, hemorrhage, and shock.
Blood Pressure: Hypertension and Hypotension
Normal blood pressure is 120/80 mm Hg. Elevated blood pressure is 120-129/under 80 mm Hg. Hypertension, warranting treatment at 130/80 mm Hg, is often asymptomatic and can lead to severe cardiovascular events, aneurysms, peripheral arterial disease, chronic renal disease, or cardiac failure.
Conversely, hypotension is reduced blood pressure below 90/60 mmHg. This causes reduced blood flow to organs and tissues, causing symptoms such as dizziness, fainting, blurred vision, fatigue, and lack of concentration. While chronic low blood pressure without symptoms often isn't serious, acute hypotension can be a medical emergency requiring prompt attention to restore adequate circulation and prevent organ damage.
Hemorrhagic Event
Significant blood loss exceeds the body's hemostatic mechanisms. Immediate responses aim to elevate blood pressure and maintain perfusion. Baroreceptors activate sympathetic responses, increasing cardiac output and vasoconstriction. Hormones like epinephrine and norepinephrine further enhance these effects. If blood loss is less than 20% of total volume, these responses usually normalize blood pressure. The renin-angiotensin-aldosterone system and Erythropoietin (EPO) help restore blood volume through fluid intake, sodium and water reabsorption, and erythrocyte formation.
Circulatory Disturbance: Shock Syndrome
Shock is a life-threatening condition where the circulatory system fails to deliver adequate oxygen and nutrients to tissues. Symptoms include increased heart rate, low blood pressure, reduced urine output, confusion, or unconsciousness.
- • Hypovolemic Shock: Caused by hemorrhage in adults or severe fluid loss in children. Symptoms include tachycardia, weak pulse, cool skin, rapid breathing, hypothermia, thirst, and dry mouth. Treatment involves intravenous fluids and drugs to elevate blood pressure.
- • Cardiogenic Shock: Results from the heart's inability to maintain output, often due to myocardial infarction. Treatment focuses on addressing the heart's underlying issues.
- • Vascular Shock: Significant arteriole dilation caused by sepsis, neurogenic shock, or anaphylaxis. Treatment includes fluid replacement and drugs to restore vessel tone.
- • Obstructive Shock: Caused by vascular system obstruction, such as pulmonary embolism or cardiac tamponade. Treatment depends on the cause, often involving anticoagulants, fluid removal, or surgery.
Each form of shock requires specific interventions to restore vascular function and maintain blood flow.
