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Cardiac output and central blood volume during hemodialysis: methodology
1Transonic Systems Inc, Ithaca, NY 14850, USA. nikolai@transonic.com
Insights
A new method reliably measures cardiac output (CO) and central blood volume (CBV) in hemodialysis patients. This technique helps understand cardiac disease and predict patient morbid events during dialysis.
Area of Science:
- Cardiology
- Nephrology
- Medical Technology
Background:
- Cardiovascular disease is a primary cause of death in hemodialysis patients.
- Accurate monitoring of cardiac function is crucial for this population.
- Existing methods may not be suitable for hemodialysis settings.
Purpose of the Study:
- To develop and validate a method for measuring cardiac output (CO) and central blood volume (CBV) in hemodialysis patients.
- To identify and mitigate sources of error in CO and CBV measurements during hemodialysis.
- To assess the clinical utility and prognostic value of routine CO and CBV monitoring.
Main Methods:
- Developed a technique to measure CO and CBV in hemodialysis patients.
- Identified and addressed key error sources: access recirculation, indicator recirculation, and transit time.
- Validated measurement reproducibility and prospectively recorded morbid events during dialysis sessions.
Main Results:
- Achieved high reproducibility for CO (4.3%) and CBV (4.1%) measurements after error correction.
- Observed that central blood volume (CBV) was a more sensitive indicator of morbid events than CO in certain cases.
- Identified 28 morbid events across 98 dialysis sessions, with CBV showing higher sensitivity in 10 instances.
Conclusions:
- CO and CBV can be routinely and reliably measured during hemodialysis with appropriate error prevention.
- These measurements show potential for significant prognostic value in hemodialysis patients.
- Further studies are warranted to confirm the clinical utility of CO and CBV monitoring.
Abstract:
Cardiovascular disease is the leading cause of mortality in patients whose lives depend on hemodialysis. We developed a method for measuring cardiac output (CO) and central blood volume (CBV) in hemodialyzed patients that may help to elucidate the mechanisms and consequences of cardiac disease in this population. This report describes the technique, focusing on the main sources of error and how they can be prevented. Three principal sources of error were identified: (1) access recirculation (existing or induced during injection); (2) the second pass of the indicator through the cardiopulmonary system, exacerbated by prolonging the duration of intravenous injection; and (3) the transit time of the indicator through the dialysis blood lines. After the algorithms were adjusted to prevent the above errors, the reproducibility of CO and CBV, expressed as the absolute percent deviation from the average of duplicates (3,488 values duplicated within 5 minutes), was 4.3 +/- 3.8% for CO and 4.1 +/- 3.8% for CBV. To determine the clinical value of routine CO and CBV measurements, morbid events (nausea, vomiting, and/or muscle cramps) were prospectively recorded in 73 randomly selected hemodialysis patients. CO and CBV were measured near the beginning and near the end of 98 dialysis sessions during which 28 morbid events were identified. In 10 of these sessions, where morbid events took place within 30 minutes of the measurements, CBV appeared to be a more sensitive indicator of morbid events than CO. We conclude that CO and CBV can be routinely and reliably measured during hemodialysis if precautions are taken to avoid specifically identified sources of error. Preliminary studies suggest that these measurements may have significant prognostic value.