Continuous lactate monitoring in critically ill patients using microdialysis.

INTRODUCTION: Blood lactate is a strong predictor of mortality in critically ill patients. Its monitoring implies repeated measurements. The EIRUS™ system (Maquet Critical Care AB, 17154, Solna, Sweden) is a new device allowing continuous lactate monitoring by intravascular micro dialysis. The present study aimed at assessing the accuracy of the EIRUS™ system in critically ill patients with circulatory failure. METHODS: An observational cohort study was conducted in Nîmes University Hospital. Eligible patients were those with circulatory failure in which a specific central venous access was put in place by the physician in charge, allowing continuous lactate measurement by the EIRUS™ system. Lactate measurements obtained by the system were compared to lactate from arterial blood samples at H4 and H8 from the calibration, during the first 48hours of shock. RESULTS: In all, 28 patients were included providing 244 pairs of measures. The Bland-Altman analysis showed a bootstrapped mean bias at H4 of 0.05 and 95% limits of agreement of -0.9 to 1.0mmol/L. At H8 the mean bias was 0.06 and 95% limits of agreement -1.1 to 1.2mmol/L. The global trend agreement [95% CI] for a pre-specified arbitrary threshold of 1mmol/L, defining clinically significant variations, between H0 and H4 and H4 and H8 was 91.6% [85.1; 95.9] and 89.5% [82.3; 94.4], respectively. CONCLUSION: The EIRUS™ device provided an overall accurate measurement of lactate in critically ill patients with circulatory failure. Detection of lactate variations over time is less precise and technical issues may limit its clinical use.

Real-time continuous monitoring of injection pressure during peripheral nerve blocks in fresh cadavers.

BACKGROUND: The incidence of unintentional intraneural injection while performing peripheral nerve block has been estimated to be 15% under real-time ultrasound guidance. Injection pressure increase may detect an intraneural injection. Real-time injection pressure changes throughout an entire nerve block procedure in relationship with needle tip location have never been reported. METHODS: A new method was developed to precisely monitor the injection pressure curve during nerve blocks, based on a miniaturised Fabbri-Perrot pressure sensor. We tested in three fresh cadavers the ability of continuous pressure monitoring to discriminate between different tissues, as the injection pressure curve ascending slope, shape and plateau pressure value depend on tissue compliance. Injections of saline were performed by an electronic syringe pump with three different constant flow rates. Pressure was measured simultaneously at the tip and in the tubing of the needle. RESULTS: At 10 mL/min injection flow, median peak injection pressure in the intraneural group at the needle tip was 315 mmHg, while at the perineural location it was 100 mmHg (p < 0.05). Median injection pressure was 95 mmHg in the intramuscular locations group, and 819 mmHg when a muscular fascia was indented (p < 0.05). A significant difference was noted for pressure measurements between the proximal port of the needle and the tip, 625 and 417 respectively. CONCLUSIONS: Based on significant differences in injection pressure values and curve shapes, the system was able to discriminate between four needle tip locations. This may help with needle tracking while performing a peripheral nerve block.