Fick Cardiac Output

How does it work?

To make the most of our Fick's Cardiac Output handout, follow the instructions below:

Step 1: Gather patient information

Begin by collecting essential patient information, including their name, age, sex, and relevant medical history. This information is vital for an accurate assessment.

Step 2: Solve for the tissue oxygen consumption (VO2)

To calculate oxygen consumption (VO2), multiply the constant for oxygen consumption (125 ml O2/min, or 110 ml O2/min if the patient is older than 70 years) by the patient's body surface area (BSA).

Step 3: Solve for arterial blood oxygen (Ca)

Solving for the arterial blood oxygen is as simple as multiplying the value of the saturation of the arterial oxygen (obtained through a peripheral ABG), the value of the hemoglobin (obtained through an HHH or CBC), and the constant of oxygen bound per gram of hemoglobin, or 1.34.

Step 4: Solve for the venous oxygen (Cv)

To calculate venous oxygen content (Cv), collect a venous blood sample (usually from the central venous line). This value substitutes for the mixed venous blood gas needed in the Fick equation. Ensure the sample is drawn alongside the ABG sample for accuracy.

Step 5: Cardiac output calculation

Now, use the Fick equation to calculate cardiac output (CO). Substitute the values for VO2, Ca, and Cv that you obtained in steps 2, 3, and 4 to determine cardiac output.

Step 6: Recording and analysis

Record the cardiac output value in the Fick Cardiac Output form. Analyze the result within the context of the patient's clinical condition, including any relevant cardiac goals or concerns.

Step 7: Interpretation and action

Interpret the obtained cardiac output value. Based on the result, clinical decisions may be necessary, such as adjusting medications or other interventions to optimize cardiac function.

Step 8: Document findings

Ensure accurate documentation of the Fick Cardiac Output measurement in the patient's medical record for future reference and continuity of care.

When would you use this?

The Fick Cardiac Output measurement is a powerful tool for healthcare practitioners, especially in specific clinical situations where it provides critical insights into cardiac function. Here are the key scenarios in which using the Fick Cardiac Output is most appropriate:

• Diagnosis of heart conditions: Fick Cardiac Output is essential for cardiologists when diagnosing heart diseases like congestive heart failure, valvular disorders, and congenital heart defects. It helps establish baseline cardiac function for accurate diagnosis.
• Open-heart surgery: Cardiac surgeons rely on it during open-heart surgeries, ensuring the heart functions optimally while the patient is on bypass. It guides them in making real-time adjustments during the procedure.
• Complex surgeries: Anesthesiologists use it to monitor cardiac performance during complex surgeries, particularly in high-risk cases. It assists in tailoring anesthesia and hemodynamic management.
• Critical care management: Intensive care specialists employ Fick Cardiac Output in ICUs, especially for critically ill patients with conditions like sepsis and shock. It provides essential data for hemodynamic assessment and guides treatment choices.
• Advanced lung diseases: Pulmonologists may utilize it when evaluating patients with progressive lung diseases that impact cardiac function. It aids in developing comprehensive treatment plans.
• Sports medicine: Sports medicine specialists use it to assess cardiac performance and oxygen delivery in athletes. It's crucial for optimizing training regimens and monitoring cardiovascular health.
• Clinical research: In clinical research, Fick Cardiac Output is applied to assess the effectiveness of new cardiovascular treatments and interventions. It provides an objective measure for evaluating therapeutic outcomes.

What do the results mean?

Interpreting the results of a Fick Cardiac Output measurement is crucial for healthcare practitioners to understand a patient's cardiac performance. The values obtained provide insights into how effectively the heart delivers oxygen to the body. By using this method to measure cardiac output, healthcare providers can assess the heart's efficiency and its ability to meet the body’s metabolic demands. Here, we present common results and their implications in the context of this assessment.

• Normal range: The normal cardiac output (CO) for a healthy adult at rest typically ranges from 4.0 to 8.0 liters per minute (L/min), with an average value of approximately 5.0 L/min (King & Lowery, 2023).  This measurement reflects the volume of blood the heart pumps per minute, indicating its efficiency in delivering oxygen to the body's tissues
• Low cardiac output: If the Fick Cardiac Output measurement falls below the normal range, it suggests reduced cardiac efficiency. Common causes include heart failure, severe heart valve disease, or cardiogenic shock. Low cardiac output can lead to symptoms such as fatigue, shortness of breath, and reduced exercise tolerance.
• High cardiac output: An elevated Fick Cardiac Output may indicate conditions like anemia, hyperthyroidism, or certain congenital heart defects. While high cardiac output can initially be compensatory, it may lead to long-term strain on the heart and an increased risk of heart failure.

The interpretation of Fick Cardiac Output results should always be considered in the context of the patient's clinical condition, medical history, and specific assessment goals. It is essential to correlate the findings with other diagnostic tests and clinical symptoms to determine the underlying cause and guide treatment decisions.

References

Arjun Basnet, & Rout, P. (2024, May 29). Calculating FICK cardiac output and input. Nih.gov; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK606091/

King, J., & Lowery, D. R. (2023). Physiology, cardiac output. National Library of Medicine; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK470455/