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RESEARCH PRODUCT

Effect of Supplemental Oxygen versus Dobutamine Administration on Liver Oxygen Tension in dPP-Guided Normovolemic Pigs

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<i>Background:</i> Difference in pulse pressure (dPP) confirms adequate intravascular filling as a prerequisite for tissue perfusion. We hypothesized that both oxygen and dobutamine increase liver tissue oxygen tension (pt<i>O</i><sub>2</sub>). <i>Methods:</i> Eight anesthetized pigs received dPP-guided fluid management. Hepatic p<i>O</i><sub>2</sub> was measured with Clark-type electrodes placed subcapsularly, and on the liver surface. Pigs received: (1) supplemental oxygen (F<sub>i</sub><i>O</i><sub>2</sub> 1.0); (2) dobutamine 2.5 μg/kg/min, and (3) dobutamine 5 μg/kg/min. Data were analyzed using repeated-measures ANOVA followed by a Tukey post-test for multiple comparisons. pt<i>O</i><sub>2 </sub>measured subcapsularly and at the liver surface were compared using the Bland-Altman plot. <i>Results:</i> Variation in F<sub>i</sub><i>O</i><sub>2</sub> changed local hepatic tissue pt<i>O</i><sub>2</sub> [subcapsular measurement: 39 ± 12 (F<sub>i</sub><i>O</i><sub>2</sub> 0.3), 89 ± 35 mm Hg (F<sub>i</sub><i>O</i><sub>2</sub> 1.0, p = 0.01 vs. F<sub>i</sub><i>O</i><sub>2</sub> 0.3), 44 ± 10 mm Hg (F<sub>i</sub><i>O</i><sub>2</sub> 0.3, p = 0.05 vs. F<sub>i</sub>O<sub>2</sub> 1.0); surface measurement: 52 ± 35 (F<sub>i</sub><i>O</i><sub>2</sub> 0.3), 112 ± 24 mm Hg (F<sub>i</sub><i>O</i><sub>2</sub> 1.0, p = 0.001 vs. F<sub>i</sub><i>O</i><sub>2</sub> 0.3), 54 ± 24 mm Hg (F<sub>i</sub><i>O</i><sub>2</sub> 0.3, p = 0.001 vs. F<sub>i</sub><i>O</i><sub>2</sub> 1.0)]. Surface measurements were widely scattered compared to subcapsular measurements (bias: –15 mm Hg, precision: 76.3 mm Hg). Dobutamine did not affect hepatic oxygenation. <i>Conclusion:</i> Supplemental oxygen increased hepatic tissue p<i>O</i><sub>2</sub> while dobutamine did not. Although less invasive, the use of surface measurements is discouraged.