BackgroundExpired gas (exhalome) analysis of ventilated critical ill patients can be used for drug monitoring and biomarker diagnostics. However, it remains unclear to what extent volatile organic compounds are present in gases from intensive care ventilators, gas cylinders, central hospital gas supplies, and ambient air. We therefore systematically evaluated background volatiles in inspired gas and their influence on the exhalome.MethodsWe used multi-capillary column ion-mobility spectrometry (MCC-IMS) breath analysis in five mechanically ventilated critical care patients, each over a period of 12 h. We also evaluated volatile organic compounds in inspired gas provided by intensive care ventilators, in compressed air and oxygen from the central gas supply and cylinders, and in the ambient air of an intensive care unit. Volatiles detectable in both inspired and exhaled gas with patient-to-inspired gas ratios < 5 were defined as contaminating compounds.ResultsA total of 76 unique MCC-IMS signals were detected, with 39 being identified volatile compounds: 73 signals were from the exhalome, 12 were identified in inspired gas from critical care ventilators, and 34 were from ambient air. Five volatile compounds were identified from the central gas supply, four from compressed air, and 17 from compressed oxygen. We observed seven contaminating volatiles with patient-to-inspired gas ratios < 5, thus representing exogenous signals of sufficient magnitude that might potentially be mistaken for exhaled biomarkers.ConclusionsVolatile organic compounds can be present in gas from central hospital supplies, compressed gas tanks, and ventilators. Accurate assessment of the exhalome in critical care patients thus requires frequent profiling of inspired gases and appropriate normalisation of the expired signals.
Lidocaine is commonly used for regional anesthesia and nerve blocks. However, recent clinical studies demonstrated that intravenous perioperative administration of lidocaine can lead to better postoperative analgesia, reduced opioid consumption and improved intestinal motility. It can therefore be used as an alternative when epidural analgesia is contraindicated, not possible or not feasible. Apart from the sodium channel blocking effects relevant for regional anesthesia, lidocaine also has anti-inflammatory properties. Lidocaine can obviously inhibit the priming of resting neutrophilic granulocytes, which, simplified, may reduce the liberation of superoxide anions, a common pathway of inflammation after multiple forms of tissue trauma. At the authors' institutions intravenous lidocaine is primarily used for postoperative pain relief following abdominal surgery and is given as a bolus dose of 1.5-2.0 mg/kg body weight (BW) injected over 5 min followed by an infusion of 1.5 mg/kg BW/h intraoperatively and 1.33 mg/kg BW/h postoperatively in the recovery room or in the intensive care unit (ICU). The lidocaine infusion is stopped in the recovery room 30 min before discharge or in the ICU at the latest after 24 h. Lidocaine is not used on normal wards. This overview summarizes the current evidence for the intravenous administration of lidocaine for patients undergoing different types of surgery and gives practical advice for its use.
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