Lesson 3 – Perfusion Explored

Perfusion overview

Perfusion is the process of delivering oxygenated blood to body tissues. Understanding perfusion is crucial for assessing a patient’s condition and providing effective care. &&

Cardiovascular system anatomy

The heart has four chambers: two atria and two ventricles. Right side pumps deoxygenated blood to lungs; left side pumps oxygenated blood to body. Pulmonary arteries/veins manage lung circulation; aorta and major arteries manage systemic circulation. Coronary arteries supply the heart itself. &&

Importance of coronary arteries

Blockage can cause myocardial infarction, severely impairing the heart’s pumping ability and perfusion. &&

Cardiac cycle

Consists of systole (ventricles contract and eject blood) and diastole (ventricles relax and fill), generating pressure changes that drive blood flow. &&

Blood pressure during cardiac cycle

Left ventricle pressure ~120 mmHg during systole and ~80 mmHg during diastole in a healthy adult. Blood pressure reflects perfusion but is only one indicator. &&

Definition of cardiac output

Cardiac output = stroke volume × heart rate; typical resting value is 5-6 liters per minute in a healthy adult. &&

Factors affecting stroke volume

Preload (ventricular blood volume before contraction), afterload (resistance heart pumps against), and contractility (strength of contraction). &&

Preload influences

Determined by venous return, blood volume, and venous tone. &&

Afterload influences

Mainly systemic vascular resistance. &&

Contractility influences

Electrolyte imbalances, drugs, and ischemia can alter contractility. &&

Factors affecting perfusion

Blood volume, heart function (rate and strength), vascular tone (vasodilation or vasoconstriction), blood viscosity, and gravity. &&

Blood volume impact

Loss of ~15% blood volume can cause hypovolemic shock symptoms; loss up to 30% may not immediately drop blood pressure. &&

Vascular tone example

Septic shock causes widespread vasodilation leading to hypotension and poor tissue perfusion. &&

Blood viscosity impact

Conditions like dehydration or polycythemia increase viscosity, impairing microcirculation. &&

Gravity’s role

Elevating legs in shock promotes venous return; sitting upright helps respiratory distress; important to consider in trauma. &&

Common perfusion problems

Hypovolemia (blood loss/dehydration), heart failure (impaired pumping), distributive shock (e.g., sepsis-induced vasodilation). &&

Assessment of perfusion

Check skin color, temperature, condition; pale, cool, clammy skin indicates poor perfusion. &&

Capillary refill time

Should be

Pulse assessment

Rapid, thready pulse can indicate compensation for poor perfusion. &&

Blood pressure in perfusion

Hypotension is a late sign of shock; do not rely solely on it. &&

Level of consciousness

Altered mental status may indicate inadequate brain perfusion. &&

Importance of trending

Repeated assessments over time detect deterioration or improvement. &&

Interventions to support perfusion

Position patient supine with legs elevated in hypovolemic shock unless contraindicated by breathing issues or head injury. &&

Oxygen administration

Increases oxygen content in blood; raising saturation from 90% to 100% improves oxygen delivery by about 11%. &&

Bleeding control

Use direct pressure, wound packing, and tourniquets per protocol; modern hemostatic gauzes improve bleeding control in trauma. &&

Goal of perfusion support

Maximize oxygen delivery to tissues by maintaining circulation and controlling bleeding. &&

Summary

Understanding cardiovascular anatomy and physiology is critical; assess skin, pulses, blood pressure, and mental status; interventions can significantly impact outcomes. &&

Clinical correlation

Always correlate perfusion findings with overall clinical picture and reassess frequently due to rapid status changes. &&

Next lesson preview

Next, we’ll explore shock in detail, covering failure of compensatory mechanisms and importance of early recognition and intervention. &&