Introduction: We evaluate an innovative device consisting of an enteral feeding tube equipped with a\nphotoplethysmography (PPG) sensor in contact with the duodenal mucosa. This study aims to determine if the\nPPG signal, composed of a continuous (PDC) and a pulsatile part (PAC), is a reliable method to assess gut\nperfusion in a porcine model of septic shock.\nMethod: Fourteen piglets were anesthetized and mechanically ventilated. They were randomly assigned to two\ngroups: the nonseptic (NS) group received an infusion of Ringer�s lactate solution (RL) alone, the septic (S) group\nreceived in addition a suspension of live Pseudomonas aeruginosa. Heart rate (HR), pulse oximetry (SpO2), mean\narterial pressure (MAP), cardiac index (CI) and serum lactates were recorded and gut microcirculation (GM) was\nmonitored with a laser Doppler probe applied on the duodenal serosa. PDC and PAC were given by the PPG\nprobe inserted in the duodenum. Data was collected every 15 minutes (t0, t15�) during 150 minutes (t150).\nAfter administration of the bacteria suspension (t0), resuscitation maneuvers were performed following a defined\nalgorithm. GM PAC, and PDC were expressed as variation from baseline (GMvar, PACvar, PDCvar). Analysis of variance\n(ANOVA) with repeated measures was performed to compare hemodynamic variables, with Bonferroni correction\nas post hoc analysis on t0, t60 and t150.\nResults: One piglet was withdrawn from analysis due to a defective probe. S group (six piglets) received\nresuscitation therapy while NS group (seven piglets) did not. A significant group effect was found for the all\nparameters except HR. Post hoc analysis found a significant decrease for GM and PAC at t60. The correlation between\nPAC, PDC and microcirculatory parameters were as follows: rPACvar-GMvar = 0.496, P <0.001, rPDCvar-GMvar = 0.244; P = 0.002.\nIn the septic group, correlations were as follows: rPAC-lactate = ?0.772, P <0.001; rPDC-lactate = ?0.681, P <0.01). At the\nonset of shock, a decrease of PAC, PDC and GM occurred before the alteration of MAP.\nConclusions: PAC and PDC decreased at the onset of shock and were correlated with GM and lactate. These results\nconfirm that PPG signal reliably reflects the early perfusion alteration of the gut. Further studies should assess the\nclinical use of this device.
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