Bronchial Microdialysis of Cytokines in the Epithelial Lining Fluid in Experimental Intestinal Ischemia and Reperfusion Before Onset of Manifest Lung Injury

Today, there is no continuous monitoring of the bronchial epithelial lining fluid. This study used microdialysis as a method of continuous monitoring of early lung cytokine response secondary to intestinal ischemia-reperfusion in pigs. The authors aimed to examine bronchial microdialysis for continuous monitoring of IL-1β, TNF-α, IL-8, and fluorescein isothiocyanate Dextran 4,000 Da (FD-4). The superior mesenteric artery was cross-clamped for 120 min followed by 240 min of reperfusion (ischemia group, n = 8). Four sham-operated pigs served as controls. The pigs were anesthetized and normoventilated (peak inspiratory pressure, <20 cm H2O; positive end-expiratory pressure, 7 cm H2O). Samples from bronchial and luminal intestinal and arterial microdialysis catheters (flow-rate of 1 μL/min) were collected during reperfusion in 60-min fractions. Samples were analyzed for TNF-α, IL-1β, IL-8, and FD-4. Data are presented as median (interquartile range). A lung biopsy was collected at the end of the experiment. During reperfusion, there was an increase in bronchial concentrations of both IL-8 (3.70 [1.47-8.93] ng/mL per h vs. controls, 0.61 [0.47-0.91] ng/mL per h; P < 0.001) and IL-1β (0.32 [0.05-0.56] ng/mL per h vs. controls, 0.07 [0.04-0.10] ng/mL per h; P = 0.008). In the intestinal lumen, IL-8 was increased in the ischemia group (6.33 [3.13-9.23] ng/mL per h vs. controls, 0.89 [0.21-1.86] ng/mL per h; P < 0.001). The FD-4 did not differ between groups. Pulmonary vascular resistance and pulmonary shunt increased versus controls. During reperfusion, PaO2/FiO2 ratio decreased in the ischemia group. Histology was normal in both groups. Bronchial microdialysis detects altered levels of cytokines in the epithelial lining fluid and can be used for continuous monitoring of the immediate local lung cytokine response secondary to intestinal ischemia-reperfusion.