Noninvasive Blood Monitor Reduces Transfusions During Surgery

A noninvasive continuous blood monitor that measures hemoglobin (Hb) could reduce the number of blood transfusions that are given during surgery.

A device that that continuously monitors and measures Hb in patients undergoing surgery does not require a blood sample from the patient. Current methods rely on observation and laboratory tests, which can only be done intermittently, and can take 15 - 45 minutes to get the results back to the surgical team.

In a clinical trial carried out at the Vanderbilt University Medical Center, (Nashville, TN, USA), 327 elective orthopedic surgery patients scheduled for procedures such as hip replacement (31% of patients), knee replacement (29%), and spinal surgery (14%) were randomly assigned to groups. One group of 157 patients received standard care alone during their surgery where observation and laboratory tests were used to monitor hemoglobin levels. The other group of 150 patients received standard care plus monitoring the hemoglobin levels with the device (SpHb). SpHb monitoring counts surgical patients' red blood cell levels continuously in real time, without delays and it also does it without puncturing the skin.

The blood monitor used was the Radical-7 Pulse CO-Oximeter with a R1-25 Rainbow Adhesive Sensor, Revision E, manufactured by Masimo, (Irvine, CA, USA). The device measures hemoglobin levels using near infrared light of several different wavelengths to assess the relative quantity of circulating red blood cells. The frequency of transfusions was compared during operations and the mean number of blood units transfused, in the two groups, and they also compared the frequency of laboratory Hb testing and agreement between the SpHb counts and the laboratory Hb counts. More patients received blood transfusions and the mean number of units of blood used in the transfusions was significantly higher in the standard care group than the SpHb group during their operations. The values of Hb obtained by SpHb and standard laboratory tests showed good agreement.

Jesse Ehrenfeld, M.D., the lead author of the study, noted that because the standard Hb test took so long, surgeons in the absence of timely results often go for the safest option, contributing to the 1.9 million transfusions given during surgery every year in the US. He added, "The next stage will be to do a larger trial to see how the device affects transfusion rates in other groups of patients, including those undergoing trauma and cardiac surgery, where more blood is often needed.” A report of the trial was made on October 18, 2010, at the annual meeting of the American Society of Anesthesiologists, held in San Diego, CA, USA.

Related Links:
Vanderbilt University Medical Center
Masimo