Tissue oxygenation index is a useful monitor of histologic and neurologic outcome after cardiopulmonary bypass in piglets.
OBJECTIVE
Tissue oxygenation index is a novel monitoring indicator derived by near-infrared spectroscopy. We hypothesized that tissue oxygenation index could predict a minimum safe flow rate for specific bypass conditions.


METHODS
Thirty-six piglets (age, 43 +/- 5 days; weight, 9.0 +/- 1.1 kg) underwent cardiopulmonary bypass with cerebral near-infrared spectroscopy (NIRO-300; Hamamatsu Photonics K.K., Hamamatsu City, Japan). Animals were cooled for 40 minutes to 15 degrees C, 25 degrees C, or 34 degrees C (pH-stat, hematocrit value of 20% or 30%, and pump flow of 100 mL . kg -1 . min -1), followed by low-flow perfusion (10, 25, or 50 mL . kg -1 . min -1) for 2 hours. Neurologic and behavioral evaluations were determined for 4 days. The brain was then fixed for histologic assessment. Tissue oxygenation index was defined as the average signal during low-flow bypass.


RESULTS
Animals with an average tissue oxygenation index of less than 55% showed cerebral injury, whereas animals with an index of greater than 55% showed minimal or no evidence of injury. Correlations were found between average tissue oxygenation index and histologic score (Spearman rho = -0.65, P < .001) and neurologic deficit score (Pearson r = -0.50, P = .002) on the first postoperative day. Temperature (P < .001), flow rate (P < .001), and hematocrit value (P = .002) were multivariable predictors of tissue oxygenation index, as determined by means of multivariable analysis of variance.


CONCLUSIONS
Tissue oxygenation index is a useful monitor for defining the minimum safe flow rate during cardiopulmonary bypass. An index value of less than 55% is a strong predictor of neurologic injury.
Hagino
Ikuo
I
Department of Cardiovascular Surgery, Children's Hospital Boston, Harvard Medical School, MA, USA.
Anttila
Vesa
V
Zurakowski
David
D
Duebener
Lennart F
LF
Lidov
Hart G W
HG
Jonas
Richard A
RA
D000818:Animals; D002545:Brain Ischemia / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D007036:Hypothermia, Induced / Q000009:adverse effects; D002534:Hypoxia, Brain / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D023421:Models, Animal; D017063:Outcome Assessment, Health Care; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000032:analysis; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D013552:Swine
D010100:Oxygen