Resonance Raman spectroscopy: a new technology for tissue oxygenation monitoring.
OBJECTIVE
To evaluate resonance Raman spectroscopy for the detection of changes in sublingual mucosal hemoglobin oxygen saturation (Smo2) in response to hemorrhage and resuscitation, and to compare Smo2 with other indicators of tissue oxygenation including central venous oxygen saturation (Scvo2), lactate, base excess, and shed blood volume.


METHODS
Prospective single group pilot study.


METHODS
University laboratory.


METHODS
Five Sprague-Dawley rats.


METHODS
Animals were anesthetized and instrumented for measurement of arterial and central venous blood gases. Raman spectroscopy was performed using a krypton ion laser providing excitation at 406.7 nm (5 mW). A 1-mm2 region of the sublingual tongue surface was chosen for investigation. Animals were subjected to stepwise hemorrhage until approximately 50% of the blood volume was removed. At each hemorrhage and resuscitation interval, Raman spectroscopy was performed and corresponding arterial and central venous blood gas and lactate measurements were made. Smo2 was calculated as the ratio of the oxygenated heme spectral peak height to the sum of the oxy- and deoxyhemoglobin spectral peak heights. Raman spectroscopy-derived Smo2 measurements were compared with Scvo2 as well as with other indicators of oxygenation.


RESULTS
The mean difference between Smo2 and Scvo2 for all paired measurements was 5.8+/-11.7 absolute saturation points. Smo2 was significantly (p<.0001) correlated with Scvo2 (r=.80), lactate (r=-.78), base excess (r=.80), and shed blood volume (r=-.75). Smo2 and Scvo2 showed similar levels of precision for predicting elevated lactate and base deficit.


CONCLUSIONS
These studies demonstrate the ability of Raman spectroscopy to noninvasively track microvascular hemoglobin oxygenation in tissue and favorably correlate with other important indicators of tissue oxygenation such as Scvo2, lactate, base deficit, and shed blood volume. The technique shows promise as a method to noninvasively monitor tissue oxygenation.
Ward
Kevin R
KR
Department of Emergency Medicine, Virginia Commonwealth University Reanimation Engineering Shock Center, Richmond 23298, USA. krward@vcu.edu
Torres Filho
Ivo
I
Barbee
Robert W
RW
Torres
Luciana
L
Tiba
Mohamad H
MH
Reynolds
Penny S
PS
Pittman
Roland N
RN
Ivatury
Rao R
RR
Terner
James
J
D000818:Animals; D006454:Hemoglobins / Q000378:metabolism*; D016014:Linear Models; D008297:Male; D008833:Microcirculation; D008991:Monitoring, Physiologic / Q000379:methods*; D015999:Multivariate Analysis; D010100:Oxygen / Q000378:metabolism*; D010108:Oxyhemoglobins / Q000378:metabolism; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley; D012151:Resuscitation; D012769:Shock / Q000378:metabolism* / Q000628:therapy; D013059:Spectrum Analysis, Raman; D014059:Tongue / Q000098:blood supply
D006454:Hemoglobins; D010108:Oxyhemoglobins; D010100:Oxygen