The Problem
The current standard of care, the Swan-Ganz pulmonary artery catheter (PAC), uses invasive methods to measure cardiac output; the PAC is inserted into the internal jugular vein and enters into the right atrium and ventricle of the heart via the superior vena cava. The catheter is then secured into the pulmonary artery with a balloon. This can lead to complications like arrhythmia, excessive bleeding, vein tearing, embolism in the early stages, pneumothoraces, thrombosis, and pulmonary artery rupture, all of which increase risk of death.
PAC remains the clinical standard, but its invasiveness, slow response, and need for a skilled physician to insert often prevents its use, limiting clinicians from critical information about life sustaining therapy and patient prognosis.
Therefore, we are developing a minimally invasive cardiac output monitor to advance assessment and delivery of proper life sustaining therapy for critically ill patients in ICUs.
The Impact
Every year, more than 5 million patients are admitted to ICUs in the United States. Many of these patients are critically ill and at high risk for life-threatening health problems. Hemodynamic monitoring is crucial for the ICU patient population as the physiological response to critical illness is linked strongly to outcome. Proper monitoring can reduce the incidence of complications and lengths of hospital stays, saving lives and money.
Why Monitor Cardiac Output?
CO is considered the holy grail of hemodynamic monitoring for critically ill patients. Cardiac output (CO) is the volume of blood pumped by the heart every minute and is thus is a great indicator of the efficiency of the heart. The ultimate goal of any hemodynamic monitoring system is to provide clinicians with detailed information on a patient’s condition. Benefits of cardiac output monitoring include:
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Evaluate Patient Response to Treatments: CO monitoring can first establish a patient's initial hemodynamic status and then measure a patient's responsiveness to various treatments such as the use of inotropic and vasoactive drugs that support the heart and circulation.
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Calculate the Amount of Fluids a Patient Requires: Cardiac output is directly related to a patient's stroke volume (SV), which is the amount of blood pumped out of the heart during each contraction. Fluids are typically given to patients in order to increase their stroke volume. Hence, CO and SV provide powerful insight into the fluid status of a patient and their actual hemodynamic response to fluid administration.
Overall, cardiac output monitoring provides information on oxygen delivery to the body.
Case Study: CO Monitoring in Action
Sam is a patient in the ICU with acute heart failure. His heart rate is slightly elevated (91 bpm), and his blood pressure is slightly low (90/60 mmHg). Dr. Jay is continuously monitoring Sam’s vitals, along with cardiac output.
As Sam’s blood pressure starts to decrease, Dr. Jay needs to make a decision on how to treat his patient. Since cardiac output is being monitored, Dr. Jay can see that cardiac index is low. Because the heart rate is not low, Dr. Jay then decides that Sam’s cardiac output, and thus blood pressure is decreasing due to weak heart function.
Dr. Jay then proceeds to administer positive inotropic drugs that will increase the contractility of Sam’s heart. However, these drugs have negative long-term effects, so he wants to limit their use. Dr. Jay continues to monitor Sam’s cardiac output until it reaches a normal level at which time he can stop administering the drug.