Thursday, June 26, 2014

Arterial Waveform Analysis Devices

Image 1: From PiCCO @ Bedside, iOS Mobile app [1]. 

Due to the results of the March 2014 "ProCess Trial" indicating that early goal directed therapy in septic shock did not improve outcomes [2] , there has been less interest in using pulse contour analysis devices to optimize fluid management in the critically ill patient. 

The main reason for this is that these devices, even though less invasive then the pulmonary artery catheter still require at the minimum an arterial line and in addition (depending on device) a central venous catheter

However, before letting these devices collect dust on a shelf, I believe this tool can be still be very beneficial in two patient populations.

One, is the high risk surgical patient to optimize fluid management.
This strategy is currently termed "Goal directed Intra-operative fluid administration".

Fluid overload during surgery has been associated with [3]:

-Increased length of stay
-Bowel wall edema
-Edema organ dysfunction
-Adverse outcomes

Additionally, patients receiving fluid and hemodynamic optimization during surgery are at an decreased risk of renal impairment. 

The second type of patient that may benefit from minimally invasive cardiac output monitoring is the critically ill cardiovascular patient.

 With these patients the ICU physician is always questioning [4]:

-"Is the patient's pre-load sufficient to obtain adequate Cardiac output"?
-"Does the patient need volume (fluids) or forced diuresis"?
-"What is the patient's cardiac function"?
-"Does the patient need inotropes or pressors"?

In these patients'  not optimizing fluid management can be detrimental. 


All devices calculate cardiac output based on the traditional equation:


CO = Cardiac Output
SV= Stroke volume
HR= Heart rate 

However, each device uses a proprietary method to calculate stroke volume or a modification of the Fick principle. Below is a table I created that compares and contrast three different pulse contour analysis devices.  

Image 2: Table comparing Pulse Contour Analysis Devices.

For more information on Arterial Waveform Analysis Devices one can visit the Society of Critical Care Medicine and take the online course "Less-Invasive Hemodynamic Monitoring" [5]. 


3. Optimization of the High Risk Surgical Patient. SCCM, lecture 2014

4. Transpulmonary Thermodilution. SCCM, lecture 2014.