Noninvasive technique can help in monitoring hemoglobin during surgery in children

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 Levels

However, 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.