No abstract

The level of IAP used in current practice (10-12 mmHg) appears to be safe with regard to hemodynamic variables and tissues blood flow; however, higher levels may induce a decrease in cardiac output and tissue blood flow.

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.

Background: Contents of the epithelial lining fluid (ELF) of the bronchi are of central interest in lung diseases, acute lung injury and pharmacology. The most commonly used technique broncheoalveolar lavage is invasive and may cause lung injury. Microdialysis (MD) is a method for continuous sampling of extracellular molecules in the immediate surroundings of the catheter. Urea is used as an endogenous marker of dilution in samples collected from the ELF. The aim of this study was to evaluate bronchial MD as a continuous monitor of the ELF.

Cardiac power (PWR) is the continuous product of flow and pressure in the proximal aorta. Our aim was to validate the PWR integral as a marker of left ventricular energy transfer to the aorta, by comparing it to stroke work (SW) under multiple different loading and contractility conditions in subjects without obstructions in the left ventricular outflow tract. Six pigs were under general anesthesia equipped with transit time flow probes on their proximal aortas and Millar micromanometer catheters in their descending aortas to measure PWR, and Leycom conductance catheters in their left ventricles to measure SW. The PWR integral was calculated as the time integral of PWR per cardiac cycle. SW was calculated as the area encompassed by the pressure–volume loop (PV loop). The relationship between the PWR integral and SW was tested during extensive mechanical and pharmacological interventions that affected the loading conditions and myocardial contractility. The PWR integral displayed a strong correlation with SW in all pigs (R2 > 0.95, P < 0.05) under all conditions, using a linear model. Regression analysis and Bland Altman plots also demonstrated a stable relationship. A mixed linear analysis indicated that the slope of the SW-to-PWR-integral relationship was similar among all six animals, whereas loading and contractility conditions tended to affect the slope. The PWR integral followed SW and appeared to be a promising parameter for monitoring the energy transferred from the left ventricle to the aorta. This conclusion motivates further studies to determine whether the PWR integral can be evaluated using less invasive methods, such as echocardiography combined with a radial artery catheter.