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. 2013 Jun;39(6):501-6.
doi: 10.1097/SHK.0b013e3182934056.

Evaluation of Multiple Modes of Oximetry Monitoring as an Index of Splanchnic Blood Flow in a Newborn Lamb Model of Hypoxic, Ischemic, and Hemorrhagic Stress

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Free PMC article

Evaluation of Multiple Modes of Oximetry Monitoring as an Index of Splanchnic Blood Flow in a Newborn Lamb Model of Hypoxic, Ischemic, and Hemorrhagic Stress

Richard L Applegate 2nd et al. Shock. .
Free PMC article

Abstract

Early and aggressive treatment of circulatory failure is associated with increased survival, highlighting the need for monitoring methods capable of early detection. Vasoconstriction and decreased oxygenation of the splanchnic circulation are a sentinel response of the cardiovasculature during circulatory distress. Thus, we measured esophageal oxygenation as an index of decreased tissue oxygen delivery caused by three types of ischemic insult, occlusive decreases in mesenteric blood flow, and hemodynamic adaptations to systemic hypoxia and simulated hemorrhagic stress. Five anesthetized lambs were instrumented for monitoring of mean arterial pressure, mesenteric artery blood flow, central venous hemoglobin oxygen saturation, and esophageal and buccal microvascular hemoglobin oxygen saturation (StO2). The sensitivities of oximetry monitoring to detect cardiovascular insult were assessed by observing responses to graded occlusion of the descending aorta, systemic hypoxia due to decreased FIO2, and acute hemorrhage. Decreases in mesenteric artery flow during aortic occlusions were correlated with decreased esophageal StO2 (R = 0.41). During hypoxia, esophageal StO2 decreased significantly within 1 min of initiation, whereas buccal StO2 decreased within 3 min, and central venous saturation did not change significantly. All modes of oximetry monitoring and arterial blood pressure were correlated with mesenteric artery flow during acute hemorrhage. Esophageal StO2 demonstrated a greater decrease from baseline levels as well as a more rapid return to baseline levels during reinfusion of the withdrawn blood. These experiments suggest that monitoring esophageal StO2 may be useful in the detection of decreased mesenteric oxygen delivery as may occur in conditions associated with hypoperfusion or hypoxia.

Conflict of interest statement

None of the authors have any conflict of interest to report.

Figures

Fig 1
Fig 1
Time course of changes in mesenteric artery flow, mean brachial artery blood pressure, buccal StO2, ScvO2, and esophageal StO2 in response to 50% (A), 75% (B), and 100% (C) graded occlusion of the descending aorta (n = 5).
Fig 2
Fig 2. Effect of systemic hypoxia (shaded area, fractional inspired O2 = 0.10) on arterial blood pressure, mesenteric artery flow, and the three modes of oximetry monitoring
Esophageal StO2 decreased significantly within seconds of the onset of hypoxia (P < 0.05, one-way ANOVA); buccal StO2 decreased significantly near the end of the hypoxic insult (P< 0.05, one-way ANOVA), and ScvO2 did not change significantly during hypoxia (P > 0.05, one-way ANOVA, n = 5).
Fig 3
Fig 3. Effect of hemorrhage on mesenteric flow, brachial arterial pressure, and the three methods of oximetry
A, Results from a representative animal. Withdrawal of blood began at time 0 and ended when arterial blood pressure had decreased to ∼60% of baseline (arrow). B, Linear regression using data from five animals. Mesenteric flow changes in response to hemorrhage were directly related to changes in buccal StO2 (slope = 0.35 ± 0.01, R2 = 0.65), brachial arterial pressure (slope = 0.67 ± 0.01, R2 = 0.61), and esophageal StO2 (slope = 0.74 ± 0.02, R2 = 0.42) and weakly related to changes in ScvO2. Dashed lines represent 95% confidence intervals (n = 5). C, Absolute 95% confidence interval from the linear regressions plotted in B, from 25% to 175% of baseline mesenteric artery flow.
Fig 4
Fig 4. Effect of reinfusion of blood following hemorrhagic insult on mesenteric flow, brachial arterial pressure, and the three methods of oximetry
Reinfusion of blood was completed at time 0. There were no significant changes in mesenteric flow, mean arterial blood pressure, buccal StO2, or ScvO2, whereas esophageal StO2 had increased significantly within 4 min of reinfusion (*P < 0.05, one-way ANOVA, n = 5).

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