From the Guidelines
Normal cardiac output in adults typically ranges from 4 to 6 liters per minute at rest, depending on body size. This represents the volume of blood pumped by the heart in one minute and is calculated by multiplying stroke volume (amount of blood pumped per heartbeat) by heart rate 1. Cardiac output varies based on several factors including body size, physical activity, and overall health status. During exercise, cardiac output can increase significantly, reaching up to 20-25 liters per minute in trained athletes.
Key Factors Influencing Cardiac Output
- Body size: larger individuals tend to have higher cardiac output
- Physical activity: exercise increases cardiac output to meet increased metabolic demands
- Overall health status: cardiac output can be decreased in heart failure or other cardiovascular disorders Cardiac output is an essential measurement of heart function and cardiovascular health, as it reflects the heart's ability to meet the body's metabolic demands by delivering adequate oxygen and nutrients to tissues. Decreased cardiac output may indicate heart failure or other cardiovascular disorders, while elevated cardiac output can occur in conditions like anemia, hyperthyroidism, or during pregnancy 1.
From the Research
Normal Cardiac Output Values
- The normal cardiac output (CO) values for adults were established in a study published in 2021 2, which found that CO normal limits were lower in females than in males (lower limit: 3.3 vs 3.5 L/min, upper limit: 7.3 vs 8.2 L/min).
- The same study also found that cardiac index (CI) normal limits were identical for both genders (lower limit: 1.9 L/min/m², upper limit: 4.3 L/min/m²).
- Another study published in 2019 3 compared cardiac output measurements via echocardiography versus thermodilution and found no significant differences between the two methods (mean difference [MD], -0.14; 95% confidence interval, -0.30 to 0.02; P = 0.08).
Factors Affecting Cardiac Output
- A study published in 2008 4 explained that cardiac output is dependent on the heart rate, contractility, preload, and afterload.
- The study published in 2021 2 also found that CO of obese patients was significantly greater than that of their nonobese counterparts, while CI of obese patients was not influenced by age and gender and was not significantly different than that of nonobese patients.
Measurement Techniques
- Thermodilution is a popular method used for measuring cardiac output (CO) in the clinical setting, as discussed in a review published in 2019 5.
- Echocardiography is also frequently used in the hemodynamic evaluation of critically ill patients, but its accuracy and interchangeability with thermodilution have been debated, as discussed in studies published in 2016 6 and 2019 3.