Non-Invasive Hemoglobin Monitoring in the Patient With Suspected Hemorrhage

Anemia and bleeding are major causes of morbidity and mortality in both surgical and nonsurgical patients. The current standard of care for monitoring patients at risk for bleeding is serial measurement of hemoglobin levels. At present, the photometric cyanmethemoglobin method is the most widely used technique for monitoring hemoglobin in the lab, and is currently the gold standard. However, this method has potential for delay before final results are obtained.

Immediate hemoglobin measurements are available with portable point-of-care devices such as the iSTAT, which can produce a measurement of hemoglobin concentration in less than 1 minute. Unfortunately, the accuracy of this device has been reported to vary with hemoglobin level, and as such may not be as accurate in detecting blood loss when compared with the gold standard of laboratory analysis.

Recently, a noninvasive, spectrophotometry-based monitoring technology has been developed. This novel technology measures the differential optical density of wavelengths of light passed through the finger in a method similar to conventional pulse oximetry. While some studies have reported that this device appears to be accurate in patients undergoing elective surgical procedures, more recent work suggests that this accuracy degrades with increased blood loss, lower oximeter signal quality and lower absolute Hgb values.

We will evaluate the accuracy of point-of-care and non-invasive SpHb measurements and utility of continuous hemoglobin monitoring in an intensive care unit setting. If these methods of rapid hemoglobin measurement can be validated in patients at risk for ongoing hemorrhage, use of this technology may result in earlier detection of ongoing hemorrhage, expedite appropriate treatment, and improve patient outcomes.