Maintaining oxygen delivery is crucial to prevent intestinal ischemia in critical ill patients

Abstract

Background: Intestinal ischemia is a common complication with obscure pathophysiology in critically ill patients. Since insufficient delivery of oxygen is discussed, we investigated the influence of oxygen delivery, hemoglobin, arterial oxygen saturation, cardiac index and the systemic vascular resistance index on the development of intestinal ischemia. Furthermore, we evaluated the predictive power of elevated lactate levels for the diagnosis of intestinal ischemia.

Methods: In a retrospective case-control study data (mean oxygen delivery, minimum oxygen delivery, systemic vascular resistance index) of critical ill patients from 02/2009-07/2017 were analyzed using a proportional hazard model. General model fit and linearity were tested by likelihood ratio tests. The components of oxygen delivery (hemoglobin, arterial oxygen saturation and cardiac index) were individually tested in models.

Results: 59 out of 874 patients developed intestinal ischemia. A mean oxygen delivery less than 250ml/min/m2 (LRT vs. null model: p = 0.018; LRT for non-linearity: p = 0.012) as well as a minimum oxygen delivery less than 400ml/min/m2 (LRT vs null model: p = 0.016; LRT for linearity: p = 0.019) were associated with increased risk of the development of intestinal ischemia. We found no significant influence of hemoglobin, arterial oxygen saturation, cardiac index or systemic vascular resistance index. Receiver operating characteristics analysis for elevated lactate levels, pH, CO2 and central venous saturation was poor with an area under the receiver operating characteristic of 0.5324, 0.52, 0.6017 and 0.6786.

Conclusion: There was a significant correlation for mean and minimum oxygen delivery with the incidence of intestinal ischemia for values below 250ml/min/m2 respectively 400ml/min/m2. Neither hemoglobin, arterial oxygen saturation, cardiac index, systemic vascular resistance index nor elevated lactate levels could be identified as individual risk factors.

Fig 1. Patient selection flow diagram.

II = intestinal ischemia, LOS = length of stay, h = hour.

Fig 2

A. Regressor plot of meanDO₂I within 72h. DO₂I = oxygen delivery index, h = hour, the solid line shows the regressor plot for meanDO₂I, dashed lines show the standard deviation, above the x-axis the 14.320 DO₂I calculations are plotted as single small lines. B. Relative ischemia risk compared to mean DO₂I within 72h before the onset of intestinal ischemia. Y-axis shows increasing relative ischemia risk with decreasing meanDO₂I values (x-axis, solid line) by DO₂I values below approximately 250ml/min/m² (highlighted by the red marked area), dashed lines show the standard deviation, above the x-axis the 14.320 DO₂I calculations are plotted as single small lines (critical DO₂I values are highlighted as a red line), DO₂I = oxygen delivery index, h = hours.

Fig 3. Relative ischemia risk compared to min DO₂I within 72h before the onset of intestinal ischemia.

Y-axis shows increasing relative ischemia risk with lower minDO₂I values (x-axis, solid line) by DO₂I values below approximately 400ml/min/m² (highlighted by the red marked area), dashed lines show the standard deviation, above the x-axis the 14.320 DO₂I calculations are plotted as single small lines (critical DO₂I values are highlighted as a red line), DO₂I = oxygen delivery index, h = hours.

Fig 4. Receiver operating characteristics analysis for lactate, pH, CO₂, ScvO₂ and the development of intestinal ischemia.

Panel A lactate: Area under the ROC curve: 0.5324; sensitivity 86.44% and specificity 16.2% for a cut-off value of lactate ≥ 2mmol/l; Panel B pH: Area under the ROC curve: 0.52; sensitivity 90% and specificity 21%; Panel C CO₂: Area under the ROC curve: 0.6017; sensitivity 83% and specificity 38%; Panel D ScvO₂: Area under the ROC curve: 06786.; sensitivity 77% and specificity 52%; ROC = Receiver operating characteristic.