Ventilation Strategies, Anesthetic Techniques and Cerebral Oxygenation in the Beach Chair Position

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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The Influence of Basic Ventilation Strategies and Anesthetic Techniques on Cerebral Oxygenation in the Beach Chair Position

Conditions
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Stroke

Intervention / Treatment
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* Other: Inspired oxygen fraction / end tidal carbon dioxide


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: scheduled for elective arthroscopic shoulder surgery in the beach chair position under general anesthesia with supplemental interscalene block Exclusion Criteria: refusal to give consent ineligible for interscalene block history of cardiovascular disease history of cerebrovascular disease hypertension respiratory failure non-English speaker

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 85 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Desflurane<br>Patients will receive general anesthesia with desflurane. Both arms have rSO2 measured and undergo identical changes in ventilation strategy. | Other: Inspired oxygen fraction / end tidal carbon dioxide<br>* 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.<br>|
| Experimental: Propofol<br>Patients will receive total intravenous general anesthesia (TIVA) with propofol. Both have rSO2 measured and undergo identical changes in ventilation strategy. | Other: Inspired oxygen fraction / end tidal carbon dioxide<br>* 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.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Regional Cerebral Oxygenation (rSO2) Before and 5 Minutes After Each Change in Ventilation Strategy | rSO2 will be recorded as a snap shot. A mean value from right and left sides will be calculated for each patient at each study point. Set Point 1: FIO2 30% (70% nitrogen), PETCO2 30mmHg - supine position. Set Point 2: FIO2 30% (70% nitrogen), PETCO2 30mmHg - beach chair position. Set Point 3: FIO2 100%, PETCO2 30mmHg - beach chair position. Set Point 4: FIO2 100%, PETCO2 45mmHg - beach chair position. Set Point 5: FIO2 30% (70% nitrogen), PETCO2 30mmHg - beach chair position. With each set point, the value shown is the absolute change from baseline. | duration of surgery, generally no more than 90 minutes total | 
| Regional Cerebral Oxygenation (rSO2) Values | Regional cerebral oxygenation (rSO2) values at the set ventilatory points of the study for each anesthetic choice. Set Point 1: FIO2 30% (70% nitrogen), PETCO2 30mmHg - supine position. Set Point 2: FIO2 30% (70% nitrogen), PETCO2 30mmHg - beach chair position. Set Point 3: FIO2 100%, PETCO2 30mmHg - beach chair position. Set Point 4: FIO2 100%, PETCO2 45mmHg - beach chair position. Set Point 5: FIO2 30% (70% nitrogen), PETCO2 30mmHg - beach chair position. | duration of surgery, generally no more than 90 minutes total | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Cerebral oxygenation, Beach chair position, General anesthetic technique, Inspired oxygen fraction, End tidal carbon dioxide