Perctérfogat

Perctérfogat, known in English as cardiac output, is the volume of blood the heart ejects per minute. It is typically expressed in liters per minute (L/min). Cardiac output equals heart rate times stroke volume: CO = HR × SV. In healthy adults at rest, CO is about 4 to 8 L/min, with an average around 5 L/min, depending on body size and fitness. Stroke volume—the amount of blood pumped with each heartbeat—is roughly 60–100 mL in a resting adult and can rise substantially with exercise.

CO is determined by several factors, including preload (venous return to the heart), afterload (the pressure the heart must overcome to eject blood), contractility, and heart rate. The autonomic nervous system and circulating hormones adjust these factors in response to needs such as physical activity, stress, or disease. Through these mechanisms, the heart can increase or decrease output to maintain adequate tissue perfusion.

Measurement of perctérfogat can be invasive or non-invasive. Common methods include the Fick principle, thermodilution with a pulmonary artery catheter, Doppler echocardiography, and impedance cardiography. MRI and CT can quantify CO in research settings. Non-invasive approaches are generally preferred for routine monitoring, while invasive techniques may be used in critical care or surgical settings.

Clinically, abnormal CO indicates altered perfusion. Low CO can arise from heart failure, cardiogenic shock, or severe dehydration, while high CO may occur in septic shock, hyperthyroidism, or pregnancy. CO values should be interpreted alongside heart rate, blood pressure, and overall clinical context, and they vary with age, body size, and physical conditioning.