Intraoperative Continuous Noninvasive Hemoglobin Monitoring in Patients Undergoing Thoracic Surgery
Conditions: Thoracic Anesthesia
Sponsor: Tanta University

 
OFFICIAL TITLE: 
"Intraoperative Continuous Noninvasive Hemoglobin Monitoring in Patients Undergoing 
Thoracic Surgery" 
 
NCT NUMBER: still not available 
 
DOCUMENT DATE: 
July 13, 2024  
 
 
 
 
 
 
 
 
 
 

 
Intraoperative continuous noninvasive hemoglobin monitoring in patients undergoing thoracic 
surgery. 
 
Background: hemoglobin levels similar to how a pulse oximeter provides continuous oxygen 
saturation. The spot check hemoglobin monitor works by the same principle as the continuous 
monitor but is a point-of-care device that calculates the serum hemoglobin level within 1 min of 
placement of the probe. The accuracy and reliability of both these monitors vary and the clinical 
applicability in trauma remains to be defined. Accuracy of continuous non-invasive hemoglobin 
monitoring.  
Methods: This observational study evaluated the correlation between noninvasive 
hemoglobin monitoring (SpHb) and invasive hemoglobin measurements (InvHb) in 
guiding blood transfusions during thoracic surgery. A total of 80 patients aged 18 years 
or older, all scheduled for thoracic procedures between July 2024 and July 2025, were 
enrolled. Continuous SpHb monitoring was performed throughout the surgeries, with 
simultaneous InvHb samples collected to validate the readings. The primary outcome 
will be the degree of correlation between SpHb and InvHb values. 

 
Introduction:  
 Technology has always been an essential component of patient care. As technology has 
advanced over the years, the way we have practiced medicine has evolved as well. Perhaps no 
field in medicine has been affected by technology as much as surgery. From operations being 
performed without any pain control to robotic surgery, technology has completely revamped our 
practice of surgical care and the field of trauma surgery and critical care remains no exception. 
One of the major influences of technology on patient care has been the shift in paradigm away 
from highly invasive diagnostic and therapeutic procedures to non-invasive procedures. This has 
resulted in reduced time for diagnosis, critical decisions making, andtreatment as well as 
improved patient satisfaction. Hemoglobin measurement is one of the most frequently performed 
laboratory tests after injury [1]. Non-invasive hemoglobin monitoring is a more recent 
introduction to the growing list of point-of-care testing capabilities that allows for the ability to 
monitor hemoglobin concentration in a continuous, accurate, and non-invasive fashion [2]. It is 
still growing in popularity and it is our impression that many trauma and critical care providers 
do not know about its utility nor the basic principles behind the mechanism of function. In this 
review, we will briefly discuss the basic principles of how non-invasive hemoglobin monitoring 
technology works, the different factors that affect its accuracy, and demonstrates how this 
technology may translate into added benefits to patient care. 
 
 

Invasive measurement, although accurate is time-consuming, costly, painful for the patient, and 
may have potential risk for exposure to biohazards. It can significantly delay patient care because 
of the time required for the phlebotomy, transport of the sample to the laboratory, time required 
for analysis and validation, and the reporting of results back to physician. Hemoglobin (Hgb) 
measurement is one of the most frequently ordered laboratory tests in the trauma settings; it can 
help guide therapeutic plan of management [1]. In trauma patients, these decisions range from 
blood transfusions to operative intervention. There has been a significant paradigm shift towards 
non-operative management in trauma patients and the rate of operative intervention in blunt 
abdominal and pelvic trauma has significantly declined. The majority of these patients are 
managed non-operatively and undergo surgical intervention only for ongoing bleeding or 
hemodynamic instability [3,4]. This approach however requires close monitoring in the Intensive 
Care Unit (ICU) and repeated phlebotomy for hemoglobin measurement to assess for ongoing 
hemorrhage [5]. The use of continuous or spot-check non-invasive hemoglobin monitoring 
provides the ability to monitor these patients in real time and react to changes in hemoglobin 
levels. A Cochrane review from ten trials reported outcomes on 1780 patients and found that a 
restrictive transfusion strategy is associated with 20% lower mortality, reduced hospital and ICU 
length of stay [6]. On the other hand, post operative anemia is also associated with increased post 
operative morbidity and mortality [7]. Accurate continuous measures of hemoglobin can help 
avoid the extremes of over or under transfusion. This is another avenue where a quick non-
invasive measurement of hemoglobin can help in the implementation of restrictive transfusion 
strategy. 3. Basics of function There is some variation in the basic principles that govern the 
functioning of most commercially available non-invasive devices. Most non-invasive 
hemoglobin measurement devices rely on spectrophotometry. Light is transmitted through or 
reflected from tissues and blood differentially depending on their biochemical variables. This 
difference in the degree of reflection allows for calculation of the hemoglobin and hematocrit 
using a mathematical model [8]. Other devices rely on photoplethsmography, which is the study 
of volume changes in the body. They detect the relative magnitude of the photoplethysmographic 
signal at different times of the cardiac cycle using different wavelengths of light. Separate 
photodetectors detect this signal and utilize it to determine the hemoglobin content and 
hematocrit of blood [9,10]. 4. Non-invasive hemoglobin monitors Masimo Corporation (Irvine 
Ca.) has developed a Pulse COoximeter capable of measuring hemoglobin concentration using a 
noninvasive, multi-wavelength sensor for spot check and continuous measurement: the Radical 7 
(Rad7) [11]. The technology emits multiple wavelengths of light and then calculates the 
hemoglobin concentration based on the adsorption of light in the blood [12]. The device uses a 
finger tip probe similar to a standard pulse oximeter sensor and determines the hemoglobin 
noninvasively. There are two types of hemoglobin measuring devices; continuous hemoglobin 
monitor and spot check hemoglobin monitor. The continuous non-invasive hemoglobin monitor, 
as the name suggests, monitors serum hemoglobin continuously and provides real time  
 
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