State of the art: sedation concepts with volatile anesthetics in critically Ill patients.

The use of volatile anesthetics in the intensive care unit (ICU) has only been possible at great cost with the use of commercially available anesthesia systems. A new anesthetic-conserving device (AnaConDa) now facilitates, from a technical viewpoint, the routine use of volatile anesthetics in intensive care patients as part of prolonged sedation, using ICU ventilators. The volatile anesthetic is hereby applied continually via a syringe pump into a miniature vaporizer, which is integrated into the ventilator circuit in place of the usual respiratory filter. During expiration, the anesthetic exhaled by the patient enters the recirculation system, is predominantly stored in the active carbon layer of the anesthetic-conserving device, and redirected into the inspiratory air. At clinically relevant concentrations, more than 90% of the gas is recirculated in such a way. Aside from the possibility of using a central anesthetic gas scavenging system, the use of special passive residual gas filters, which can be connected to the expiratory outlet of the respirator machine, appears above all to be practical. The use of volatile anesthetics on the ICU could adopt a permanent position in various intensive care analgosedation concepts in future. It may be possible thereby to optimize the treatment process both in medical and economical terms.

Reliability of the NeuroTrend sensor system under hyperbaric conditions.

OBJECTIVE: The goal of this study was to investigate the reliability of the multi-parameter sensor NeuroTrend in a hyperbaric environment for up to 3bar absolute pressure. Measurement of brain tissue oxygenation (ptiO2) under hyperbaric conditions is supposed to elucidate whether hyperbaric oxygenation therapy has the potential to improve ptiO2 to a clinically significant degree in pathological altered brain tissue after traumatic brain injury. METHODS: The NeuroTrend sensor hose, filled with equilibrated plasma samples, was stored in a decompression chamber. The plasma samples were equilibrated with three different gas mixtures. After determination of the initial values for temperature, oxygen partial pressure (pO2), carbon dioxide partial pressure (pCO2) and hydrogen ion concentration (pH) in the plasma, the ambient pressure was stepwise increased from 0.1 to 3 bar. The same set-up was performed without increasing the ambient pressure. RESULTS: No significant difference in the mean values for all 23 measurement points and for all parameters (pO2, pCO2, pH) of all 10 NeuroTrend sensors was found, under both normobaric and hyperbaric conditions. CONCLUSION: The study demonstrated that an absolute ambient pressure up to 3 bar did not influence the measuring properties and the reliability of the NeuroTrend sensor.