The seated or "beach chair" position during surgery and general anesthesia decreases brain oxygen levels and can result in stroke. As such, poor neurological outcome following beach chair positioning is a growing concern. In the proposed study the investigators test the hypothesis that changes in ventilation strategy and anesthetic technique can affect cerebral oxygenation in anesthetized patients in the beach chair position.
This is a prospective cohort study with randomized nested design. Patients presenting for shoulder surgery will be randomized to receive desflurane or total intravenous anesthesia with propofol. Regional cerebral oxygenation will be measured using the INVOS 5100C monitor (Covidien, Boulder, CO). Depth of anesthesia will be maintained within a Bispectral Index range of 40-60. Following positioning, inspired oxygen fraction and minute ventilation will be sequentially adjusted. At each set point, regional cerebral oxygenation will be recorded and venous blood gas analysis performed. Statistical analysis will be repeated measures analysis of variance in which ventilation strategy is the within-subjects factor and anesthetic technique is the between-subjects factor; post hoc Tukey's correction will be used for multiple comparisons. If simple maneuvers of ventilation and anesthetic technique can prevent low brain oxygen levels, patient outcome may be improved.
- Inspired oxygen fraction / end tidal carbon dioxide Other
Intervention Desc: Following induction of anesthesia, FIO2 and minute ventilation will be sequentially adjusted to achieve: FIO2 30% (70% nitrogen), PETCO2 30mmHg - supine position. FIO2 30% (70% nitrogen), PETCO2 30mmHg - beach chair position. FIO2 100%, PETCO2 30mmHg - beach chair position. FIO2 100%, PETCO2 45mmHg - beach chair position. FIO2 30% (70% nitrogen), PETCO2 30mmHg - beach chair position. ARM 1: Kind: Experimental Label: Sevoflurane Description: Patients will receive general anesthesia with sevoflurane. All 3 arms have rSO2 measured and undergo identical changes in ventilation strategy. ARM 2: Kind: Experimental Label: Desflurane Description: Patients will receive general anesthesia with desflurane. All 3 arms have rSO2 measured and undergo identical changes in ventilation strategy. ARM 3: Kind: Experimental Label: Propofol Description: Patients will receive total intravenous general anesthesia (TIVA) with propofol. All 3 arms have rSO2 measured and undergo identical changes in ventilation strategy.
- Allocation: Randomized
- Masking: Open Label
- Purpose: Prevention
- Endpoint: Efficacy Study
- Intervention: Parallel Assignment
|Type||Measure||Time Frame||Safety Issue|
|Primary||Change in regional cerebral oxygenation (rSO2) before and 5 minutes after each change in ventilation strategy||2 years.||Yes|