'Radical-7' Device Tracks Blood Oxygen Carrier with Fewer Blood Samples

Newswise — San Francisco, CA. (December 4, 2012) – For children undergoing brain surgery, a new technology allows noninvasive, continuous monitoring of blood hemoglobin levels, according to a study in the December issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

Spectrophotometric hemoglobin (SpHb) assessment using the Radical-7 Pulse CO-Oximeter can be a useful "trend monitor" for hemoglobin levels during neurosurgery in children, report Dr Yong-Hee Park of Seoul National University Hospital and colleagues. Within limitations, SpHb monitoring with the Radical-7 may help to reduce the number of blood samples needed during major surgery.

Noninvasive SpHb Assessments Are Accurate…The study included 40 children undergoing neurosurgery for brain tumors or other diseases. During surgery, all patients underwent continuous, noninvasive SpHb monitoring using the Radical-7 device.

Regular monitoring of hemoglobin—the oxygen-carrying compound in the blood—is important to avoid anemia (low hemoglobin levels). Conventionally, this is done by taking frequent blood samples for direct hemoglobin measurement. But frequent blood sampling can actually contribute to the development of anemia. Because of their smaller blood volume, this risk is particularly high in children.

Similar to the familiar "finger clip" pulse oximeter, the Radical-7 works by shining different light wavelengths through blood-perfused tissues. The SpHb assessments made by the Radical-7 were compared with direct measurements in blood samples obtained at the same time. The study included a total of 119 paired SpHb and direct hemoglobin measurements.

The results showed that SpHb was fairly accurate in estimating hemoglobin levels during surgery. Although the values weren't identical, they were significantly correlated with each other, including changes in hemoglobin between measurements. The average difference between SpHb and direct measurements was just under 1 gram per deciliter—normal hemoglobin in a child is no less than 11 g/dL.

The overall concordance (agreement) rate between the two measurements was over 90 percent. The correlations between SpHb and direct measurements remained significant even after fluid replacement—an important consideration, since giving fluids can contribute to the development of anemia

…But Less So at Lower Hemoglobin LevelsHowever, SpHb was less accurate at lower hemoglobin levels. The average difference was minimal (0.03 g/dL) in the normal range of hemoglobin. However, the difference increased to more than 1 g/dL at lower levels—in the range that might prompt doctors to consider blood transfusion.

Dr Park and coauthors write, "The Radical-7 Pulse CO-Oximeter can be useful as a trend monitor in children during surgery," even after fluids are given for volume replacement. However, because of the differences between SpHb and direct measurements, they believe that SpHb estimates need to be confirmed—particularly at lower-than-normal hemoglobin levels.

Despite that limitation, the Radical-7 may provide a useful new tool for monitoring hemoglobin levels during major surgery in children, with the potential to reduce the frequency of blood samples. The researchers call for further studies of SpHb monitoring in other groups of children at high risk of anemia, such as those with critical illness or massive bleeding.

Read the article in Anesthesia & Analgesia

About the IARSThe International Anesthesia Research Society is a nonpolitical, not-for-profit medical society founded in 1922 to advance and support scientific research and education related to anesthesia, and to improve patient care through basic research. The IARS contributes nearly $1 million annually to fund anesthesia research; provides a forum for anesthesiology leaders to share information and ideas; maintains a worldwide membership of more than 15,000 physicians, physician residents, and others with doctoral degrees, as well as health professionals in anesthesia related practice; sponsors the SmartTots initiative in partnership with the FDA; and publishes the monthly journal Anesthesia & Analgesia in print and online.

About Anesthesia & AnalgesiaAnesthesia & Analgesia was founded in 1922 and was issued bi-monthly until 1980, when it became a monthly publication. A&A is the leading journal for anesthesia clinicians and researchers and includes more than 500 articles annually in all areas related to anesthesia and analgesia, such as cardiovascular anesthesiology, patient safety, anesthetic pharmacology, and pain management. The journal is published on behalf of the IARS by Lippincott Williams & Wilkins (LWW), a division of Wolters Kluwer Health.

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