SummaryOxygen delivery via a heat and moisture exchange filter with an attached T-shaped reservoir satisfies infection control requirements of high efficiency bacterial and viral filtration and low gas flows. In order to assess the performance of such a device in critically ill patients being weaned from mechanical ventilation, we simulated 16 patients using a human patient simulator, measuring fractional inspired oxygen and carbon dioxide concentrations and work of breathing at three oxygen flow rates. Oxygen concentration was dependent on peak inspiratory flow rate, tidal volume and oxygen flow rate. Rebreathing, as indicated by inspired carbon dioxide concentration, was greatest at high respiratory rates and low tidal volumes. Imposed inspiratory work of breathing was relatively high (mean 0.88 J.l )1[SD 0.30]). We conclude that this method of oxygen delivery is only suitable for patients in whom rapid extubation is anticipated.

Background. Clinical studies on the impact of dexmedetomidine on tourniquet-induced systemic effects have been inconsistent. We investigated the impact of dexmedetomidine on tourniquet-induced systemic effects in total knee arthroplasty. Methods. Eighty patients were randomly assigned to either control (CON) or dexmedetomidine (DEX) group. The DEX group received an intravenous loading dose of 0.5 μg/kg DEX over 10 minutes, followed by a continuous infusion of 0.5 μg/kg/h from 10 minutes before the start of surgery until completion. The CON group received the same calculated volume of normal saline. Pain outcomes and metabolic and coagulative changes after tourniquet application and after tourniquet release were investigated. Results. The frequency of fentanyl administration postoperatively, patient-controlled analgesia (PCA) volume at 24 hours postoperatively, total PCA volume consumed in 48 hours postoperatively, and VAS score for pain at 24 and 48 hours postoperatively were significantly lower in the DEX group than in the CON group. Ten minutes after the tourniquet release, the DEX group showed significantly higher pH and lower lactate level than those in the CON group. Antithrombin III activity and body temperature 10 minutes after tourniquet release were significantly lower in the DEX group than in the CON group. Ca2+, K+, HCO3-, base excess, and PCO2 levels 10 minutes after tourniquet release were not significantly different between the two groups. Conclusion. We showed that DEX attenuated pain and hemodynamic, metabolic, and coagulative effects induced by the tourniquet. However, these metabolic and coagulative changes were within normal limits. Therefore, DEX could be used as an analgesic adjuvant, but should not be considered for routine use to prevent the systemic effects induced by tourniquet use.

Background: Clinical studies on the impact of dexmedetomidine on tourniquet-induced systemic effects have been inconsistent. We investigated the impact of dexmedetomidine on tourniquet-induced systemic effects including pain outcomes in patients undergoing total knee arthroplasty under spinal anesthesia. Methods: Eighty patients were randomly assigned to either control (CON) or dexmedetomidine (DEX) group. DEX group received an intravenous loading dose of 0.5 µg/ kg DEX over 10 minutes, followed by a continuous infusion of 0.5 µg/ kg/h from 10 minutes before the start of surgery until completion. The CON group received the same calculated volume of normal saline. Pain outcomes and metabolic and coagulative changes after tourniquet application and after tourniquet release were investigated.Results: The frequency of fentanyl administration postoperatively, patient-controlled analgesia (PCA) volume at 24 hours postoperatively, total PCA volume consumed in 48 hours postoperatively, and VAS score for pain at 24 and 48 hours postoperatively were significantly lower in the DEX group than in the CON group.Ten minutes after tourniquet release, the DEX group showed significantly higher pH and lower lactate level than those in the CON group. Antithrombin III activity and body temperature 10 minutes after tourniquet release were significantly lower in the DEX group than in the CON group. Ca2+, K+, HCO3-, base excess, and PCO2 levels 10 minutes after tourniquet release were not significantly different between the two groups.Conclusion: We showed that DEX attenuated pain and hemodynamic, metabolic, and coagulative effects induced by tourniquet. However, these metabolic and coagulative changes were within normal limits. Therefore, DEX could be used as an analgesic adjuvant, but should not be considered for routine use to prevent the systemic effects induced by tourniquet use.