Non-Invasive Blood Pressure Monitoring

Continuous invasive arterial line monitoring is the most accurate way to monitor a patient's hemodynamics. Being able to rapidly detect a spike or drop in blood pressure is crucial in the care of both surgical and critically ill patients. Major fluctuations in blood pressure have been associated with bleeding, cardiac damage, cognitive dysfunction, stroke, and acute kidney injury. The impact of poor blood pressure control on patient outcomes is influenced not only by how high or low the pressure gets, but how long it remains at those extremes. The alternative to continuous blood pressure monitoring is to use intermittent non-invasive blood pressure cuffs, which typically display a blood pressure measurement every 5 minutes when being used in the operating room. While this might be sufficient for routine, short surgeries and monitoring in stable patients, blood pressure cuffs are inadequate for patients who are unstable or undergoing extensive surgery.

An arterial line monitor involves the insertion of a catheter into the radial artery and allows for the beat by-beat monitoring of blood pressure. The insertion of this monitor is painful, time consuming, and puts the patient at risk of infection, bleeding, nerve injury, and damage to the artery. There are many factors that can complicate the insertion of the arterial line including the presence of peripheral vascular disease, small arteries, large body habitus, and poor patient cooperation. In view of these problems, researchers have investigated non-invasive monitoring systems as alternatives to invasive arterial cannulation, but these data are limited and inconsistent.

A alternative device called the ClearSight monitor, produced by Edwards LifeSciences, provides continuous noninvasive blood pressure monitoring. The ClearSight monitor connects to the patient by wrapping an inflatable cuff around their finger. It will detect the blood volume fluctuations in the finger that occur with each heartbeat. It then converts that volume change data into beat-by-beat hemodynamic information, including blood pressure, mean arterial pressure, cardiac output, stroke volume and stroke volume variation. The ClearSight monitor was developed to advance hemodynamic monitoring of moderate-to high-risk surgery patients, including elderly and obese patients.

Patients receiving elective cardiac or cerebrovascular disease are an ideal population to study. These patients require continuous blood pressure monitoring to prevent radical swings in blood pressure (either high or low), which can put the patient at risk of intracranial hemorrhage and increased intracranial pressure, or tissue ischemia, respectively. In addition, these patients frequently have many comorbid conditions including coronary artery disease, congestive heart failure, peripheral vascular disease, cerebrovascular disease, dementia, chronic obstructive pulmonary disease, hypertension, liver disease, renal disease, obesity, malignancy, and diabetes. Many of these health conditions may compromise and affect ClearSight system's ability to analyze blood pressure. For example, peripheral vascular disease, diabetes, and hypertension can cause arterial damage, arterial stenosis and reduced blood flow to the hands and feet. Consequently, it will be informative to test the ClearSight's accuracy in this medically challenging patient demographic.

The current standard of care for patients coming for elective cardiac or neurointerventional procedures at Royal University Hospital is an invasive arterial cannulation. The purpose of this study is to compare the systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure measured by the non-invasive blood pressure monitor (ClearSight) versus the invasive radial arterial cannulation in these patients.

Inclusion criteria

• written informed consent
• undergoing elective cardiac surgery OR elective neurointerventional surgery (with standard arterial radial line for continuous blood pressure monitoring)

Exclusion criteria

• undergoing emergent cardiac surgery OR emergent neurointerventional surgery