Use of tissue oxygenation index and fractional tissue oxygen extraction as non-invasive parameters for cerebral oxygenation. A validation study in piglets.
OBJECTIVE
To evaluate the relation between cerebral tissue oxygenation index (TOI), measured with spatially resolved spectroscopy (SRS), and the different oxygenation parameters. To evaluate the relation between a new parameter named fractional tissue oxygen extraction (FTOE) and the cerebral fractional oxygen extraction (FOE).


METHODS
Six newborn piglets were measured at 33, 35, and 37 degrees C and in hypocapnia. Mean arterial blood pressure (MABP), haemoglobin (Hb), peripheral oxygen saturation (S(a)O(2)) and P(a)CO(2) were measured at each step. Cerebral blood flow (CBF) was measured by injection of coloured microspheres into the left atrium. Jugular bulb oxygen saturation (JVS), cerebral arterial and venous oxygen content (C(a)O(2) and C(v)O(2)) and FOE were calculated. TOI of the brain was calculated and FTOE was introduced as (S(a)O(2) - TOI)/S(a)O(2). The correlation was calculated with an ANCOVA test.


RESULTS
There was a positive correlation (R = 0.4 and p = 0.011) between TOI and JVS. No correlation was found with CBF, MABP or Hb. There was a positive correlation between P(a)CO(2) and cerebral TOI (R = 0.24 and p = 0.03). FTOE correlated well with FOE (R = 0.4 and p = 0.016) and there was a negative correlation between FTOE and P(a)CO(2) (R = 0.24, p = 0.03).


CONCLUSIONS
The measurement of TOI and FTOE by SRS correlated well with the cerebral venous saturation and FOE, respectively.
Naulaers
Gunnar
G
Department of Paediatrics, University Hospital Leuven, Leuven, Belgium. gunnar.naulaers@uz.kuleuven.ac.be
Meyns
Bart
B
Miserez
Marc
M
Leunens
Veerle
V
Van Huffel
Sabine
S
Casaer
Paul
P
Weindling
Michael
M
Devlieger
Hugo
H
D000818:Animals; D000831:Animals, Newborn; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D001923:Brain Chemistry; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D006454:Hemoglobins / Q000032:analysis; D016857:Hypocapnia / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D019265:Spectroscopy, Near-Infrared; D013552:Swine / Q000502:physiology*
D006454:Hemoglobins; D010100:Oxygen