September Clinical Insight

Here are a few summarizations of some clinical insight provided by different clinicians at Johns Hopkins Hospital over the last month, through both email and in-person interviews. Meetings with these clinical experts have helped validate our need and guide us to a better understanding of the problem at hand.

Kenton Zehr, MD – Cardiovascular Surgery

• At Hopkins, they put a swan in about 10 – 15% of patients.

• CO is useful to know before, after and during surgery. It is good to know for people who have heart failure.

• There are different types of heart failure patients in the ICU, but sometimes they can appear to be the same.

• Such a device would be useful when a patient (specifically heart failure patients) go to the floor after surgery. We should not focus on surgery since these patients can anyway just get a Swan put into them.

• There are currently no noninvasive cardiac output monitors that are reliable.

Kaushik Mandal, MD, MBBS – Cardiac Surgery

• Noninvasive CO monitoring is most useful for patients in the ICU who are being managed for chronic heart failure. It could also be useful for patients who have heart problems but are not getting cardiac surgery, rather a different type of surgery.

• A CO monitor is useful specifically when it is thought that there is low cardiac output and the peripheral arteries are vasoconstricted.

Steven Keller, MD, PHD – Critical Care Medicine and Pulmonology

• The current standard is a catheter placed into the pulmonary artery - so it's invasive and requires special skills. Central venous access is easier although still invasive but the measurement is less well mixed.

• Fick’s Principle should be used to get CO. In the equation there is a good way to get all the numbers except venous oxygen saturation.

• When it is known that there is a heart failure patient in the ICU, it is necessary to track their therapy.

• Right heart failure is a big sign of mortality.

• Neuro ICU at Hopkins uses the FloTrac but other ICUs do not.

• CO is thought of as a vital sign so people want to know if it is changing. There is always a bias for more information.

• Nurses in the ICU most likely would administer such a device.

Adam Sapirstein, MD, Chief - Division of Adult Critical Care Medicine and Surgical Intensive Care Unit

• There are a number of different CO monitors that are marketed. They have different levels of invasiveness, accuracy, and precision. These would be most helpful in the critically ill. Unfortunately, the truly non-invasive methods have not proved accurate or precise in the critically ill. They rely on static vascular compliance and resistance as well as other inputs.

Viachaslau Barodka, MD – Division of Cardiac Anesthesia

• In ICUs, CO is the gold standard. People normalize CO by dividing it based on numbers from height and weight to get cardiac index. This normalizes everyone.

• In situations like sepsis, CO becomes 2 to 3x its normal value

• CO will indicate that a patient is in a hyper dynamic state

• Everyone would use a real time noninvasive CO monitoring but it would be most useful in ICU specifically for cardiac patients.

• Gold standard of measurement is Fick’s principle but its not used by anything on the market.

• Many CO devices on the market test on normal patients, but in critically ill patients all the assumptions that were previously made are wrong so its not applicable.

Steven Tropello, MD – Critical Care

• Cardiac monitors, and even Swan Ganz in some cases are currently used. Methods that exist today though are unreliable and do not correlate well.

• There are different types of heart failure patients in the ICU, but sometimes they can appear to be the same.

• When the heart begins to fail, pressure backs up to the lungs and patients develop respiratory problems from hypoxia.

• Fluid balance and how well someone is doing in the ICU are directly related to cardiac output.

• There would be a value proposition in having to do minimal work to get CO.

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