The Oxygen Reserve Index (ORi™) is a non-invasive variable that reflects oxygenation continuously. The aims of this study were to examine the relationship between arterial partial pressure of oxygen (PaO 2 ) and ORi during general anesthesia, and to investigate the usefulness of ORi as an indicator to avoid hyperoxia. Twenty adult patients who were scheduled for surgery under general anesthesia with arterial catheterization were enrolled. After induction of general anesthesia, inspired oxygen concentration (FiO 2 ) was set to 0.33, and arterial blood gas analysis was performed. The PaO 2 and ORi at the time of blood collection were recorded. After that, FiO 2 was changed to achieve an ORi around 0.5, 0.2, and 0, followed by arterial blood gas analysis. The relationship between ORi and PaO 2 was then investigated using the data obtained. Eighty datasets from the 20 patients were analyzed. When PaO 2 was less than 240 mmHg (n = 69), linear regression analysis showed a relatively strong positive correlation (r 2 = 0.706). The cut-off ORi value obtained from the receiver operating characteristic curve to detect PaO 2 ≥ 150 mmHg was 0.21 (sensitivity 0.950, specificity 0.755). Four-quadrant plot analysis showed that the ORi trending of PaO 2 was good (concordance rate was 100.0%). Hyperoxemia can be detected by observing ORi of patients under general anesthesia, and thus unnecessary administration of high concentration oxygen can possibly be avoided.
KeywordsOxygen reserve index (ORi) • Arterial partial pressure of oxygen (PaO 2 ) • Hyperoxia • Hyperoxemia
The oxygen reserve index (ORi™) is a new parameter for monitoring oxygen reserve noninvasively. The aim of this study was to examine the usefulness of ORi for rapid sequence induction (RSI). Twenty adult patients who were scheduled for surgical procedures under general anesthesia were enrolled. After attaching a sensor capable of measuring ORi, oxygen (6 L/min) and fentanyl (2 μg/kg) were administered. After 3 min, propofol 2 mg/kg and rocuronium 1 mg/kg were administered without ventilation. Regardless of changes in ORi, tracheal intubation was performed either 2 min after administration of propofol or when percutaneous oxygen saturation (SpO) reached 98%. Ventilation was then provided with oxygen at 6 L/min, and trends in ORi and SpO during RSI were observed. Data from 16 of the 20 patients were analyzed. Before oxygen administration, the median SpO was 98% [interquartile range (IQR) 97-98] and ORi was 0.00 in all patients. At 3 min after starting oxygen administration, the median SpO was 100% (IQR 100-100) and the median ORi was 0.50 (IQR 0.42-0.57). There was an SpO decline of 1% or more from the peak value after propofol administration in 13 patients, and 32.5 s (IQR 18.8-51.3) before the SpO decrease, ORi began to decline in 10 of the 13 (77%) patients. The ORi trends enable us to predict oxygenation reduction approximately 30 s before SpO starts to decline. By monitoring ORi, the incidence related to hypoxemia during RSI could be reduced.
Background: Status epilepticus requires immediate treatment because treatment delay can cause permanent neurologic complications. Dexmedetomidine may be an option for the treatment of status epilepticus although its effect remains unclear with conflicting reports. Case presentation: A 64-year-old woman with epilepsy with complex partial seizures underwent total knee arthroplasty. After emergence from general anesthesia, she developed status epilepticus and was transferred to the intensive care unit. Following initial treatment using benzodiazepines, phenytoin, and levetiracetam, dexmedetomidine (0.37 μg/kg loading in 10 min followed by 0.6 μg/kg/h) was administered and seizures terminated in 20 min. Color density spectral array using Root® with SedLine® (Masimo, Irvine, CA, USA) showed an increase in power in high frequency band of the electroencephalogram during the seizure attacks. Conclusion: We described a case of status epilepticus which was treated with dexmedetomidine and monitored using color density spectral array.
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