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Fluid Challenge

Quick testing of fluid responsiveness via fluid bolus, passive leg raise, or tilt table protocols




Fluid resuscitation is a routine procedure for many patients, especially those in shock (septic, cardiogenic, and hypovolemic).  A primary goal for shock patients is to optimize hemodynamics. However, before administering fluids, clinicians will often perform a dynamic fluid challenge to diagnosis fluid responsiveness. A fluid challenge can indicate whether a patient with compromised hemodynamics will benefit from additional fluid replacement . This fluid challenge, or dynamic fluid assessment, is completed by administering a small amount of fluid over a short period of time, to assess if the patient has a preload reserve that can be used to increase the stroke volume with additional fluids . By conducting a fluid challenge, a clinician can determine whether a patient is a candidate to receive fluids and, therefore, reduce the risk of fluid overload .


Currently there are two main protocols to perform a fluid challenge: a fluid bolus or passive leg raise (PLR). 

Fluid Bolus Protocol

Administer a 200 - 250cc fluid bolus over a 5-10 minute period, or 

Administer a 500cc fluid bolus over a 20-30 minutes period

Passive Leg Raise Protocol


1. Semi Recumbent Baseline - get a baseline of data with the patient's torso at a 45 degree angle

2. PLR Challenge - place the patient's torso in supine and their legs in at a 45 degree angle

3. Return to Semi Recumbent  - monitor change in SV and CO


A patient is considered fluid responsive if they show a ≥10% increase in stroke volume (SV) or cardiac output (CO)  from the fluid challenge. 

Existing Technology and Limitations

Currently there are 5 main techniques to monitor SV and CO:


Pulmonary Artery Catheter (PAC)

The PAC is an invasive catheter that was once considered the gold standard for CO and SV monitoring. With other monitoring systems now available, many consider PAC as risky and often unreliable. 

Doppler - Esophagael or Transthoracic Echocardiography

Transthoracic Echocardiography (TTE) is an accurate method for CO estimation, however it is highly operator dependent and requires precise placement. Often described as "sensitive" and "finicky" by some users. 

Pulse Pressure Analysis

A common, noninvasive or minimally invasive solution, however it often has accuracy limitations if there is hemodynamic instability, peripheral vascular compromise, or vasopressor influence.

Bioimpedance and Bioreactance

A noninvasive solution that looks at thoracic or body impedance variations. Often susceptible to electrical interference, and finding optimal sensor placement location can be challenging. 

Fick Principle

Highly accurate, most commonly used, and considered the gold standard method for calculating CO and SV. It looks at the proportional difference between arterial and venous oxygen saturation. Currently clinicians are drawing blood samples to manually calculate Fick   .


Our solution to provide a quick test for fluid responsiveness

The VenArt Cardiac Output monitoring system noninvasively obtains venous and arterial oxygen saturation values - and then performs a beat-by-beat Fick Principle calculation in order to derive cardiac output, cardiac index, stroke volume, and stroke volume variations. 

Advantages on using the VenArt Cardiac Output

Technologically Sound - a unique scientific approach which uses the gold standard Fick Principle, to provide a real time beat-by-beat calculation of SV and CO 

Superior Usability - any healthcare professional can place the sensors on the patient and obtain readings 

Low Cost - reusable sensors with low cost adhesives at a fraction of the cost compared to other technology


Quick Fluid Challenges  - 3 built in fluid challenge protocols; fluid bolus, PLR, and tilt table - which can be completed within a minute or two

Low Risk - uses near infrared spectroscopy (NIRS) and, therefore, completely noninvasive

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  2. Cecconi, M., Parsons, A.K., Rhodes, A. (2011) What is fluid challenge? Curr Opin Crit Care 17:290-205

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  5. Li T, Cai H, Pan H, Pu Q. Cardiac output measurement using a modified carbon dioxide Fick method: comparison analysis with pulmonary artery catheter method and pulse induced contour cardiac output method. Int J Clin Exp Med 2015;8(3):3530-3537

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  8. Winbroum AA, Biderman P, Soffer D, Klausner JM, Szold O. Reliability of cardiac output calculation by the fick principle and central venous oxygen saturation in emergency conditions. Journal of clinical monitoring and computing 2008;22:361-6

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