CO2 (Carbon Dioxide) - Cerebral Oxygenation

Study Overview
=================
Brief Summary
-----------------
Several projects in high altitude research in environments with a low oxygen partial pressure (hypobaric hypoxia) leading to hypoxemia showed, that cerebral perfusion and cerebral performance could be improved by adding C02 (cabon dioxide). The investigators hypothesize that adding 5% C02 to 02 (Oxygen) also under normobaric conditions increases the time until a significant cerebral hyopxia is measured by near infrared spectroscopy (NIRS) compared to the administration of 95% 02. lf this hypothesis proves to be true, this approach might be used in situations in which individuals are prone to cerebral hypoxia. In bariatric surgery, patients that experience an apnea phase are more prone to (cerebral) hypoxia due to the fact, that they have a higher body mass index (BMI) leading to a reduced functional residual capacity (FRC), which serves as the oxygen reserve in the body.

Detailed Description
-----------------
On the day of surgery patients will be randomized. After induction of anesthesia and endotracheal intubation patients will be managed by the study team to perform the intervention and the measurements. According to randomization, investigational medical product (IMP) or comparator will be administrated by ventilator 1/ventilator 2. At time point 1 apnea will be performed by disconnecting the ventilator from the endotracheal tube until the NIRS value has dropped by 20% from baseline. After that, re-ventilation will be resumed immediately, until parameters have returned to baseline. During apnea time NIRS and vital signs will be recorded permanently, blood samples will be drawn at definite time points. Application of IMP (or comparator) will be performed in this cross-over study design in the same manner after the baseline level is reached again. At the end of the study procedure, after the baseline level of end-expiratory CO2 is reached again, patient will be taken over by the clinical anesthesia team and surgeons.

Official Title
-----------------
Anesthesia vs Aviation: Does Added Carbon Dioxide in Normobaric Hypoxia Have the Same Effect on Cerebral Oxygenation as in Hypobaric Hypoxia?

Conditions
-----------------
Hypoxia, Brain

Intervention / Treatment
-----------------
* Drug: Oxycarbon (5% CO2+ 95% O2)


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Patients who are designated for bariatric surgery at the University Hospital Zurich (USZ) Informed Consent as documented by signature BMI >35 kg/m2 Exclusion Criteria: Severe end-organ damage: chronic obstuctive pulmonary disease (COPD) GOLD (cassification) III and IV, known hepatic insufficiency or elevated liver enzymes, renal creatinine clearance <30ml/min Severe cardiovascular disease (NYHA classification III and IV) Known pulmonary Hypertension Cerebrovascular disease Pregnancy and lactation Cardiac dysrhythmias acidosis, chronic pulmonary disease Known or suspected non-compliance, drug or alcohol abuse

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Controlled, randomized, single blind, crossover
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Oxycarbon (5% CO2 + 95% O2)<br>Patients will be mechanical ventilated with Oxycarbon (5%CO2 +95% O2) after normocapnia is reached until FeO2 is stable for at least 1 min ≥ 80%. At timepoint 1 immediately prior apnea NIRS and vital parameters will be registered and an bloodsample will be drawn. | Drug: Oxycarbon (5% CO2+ 95% O2)<br>* Oxycarbon will be administered by mechanical ventilation<br>|
| Placebo Comparator: Control (95% O2)<br>Same procedure as arm active comparator | Drug: Oxycarbon (5% CO2+ 95% O2)<br>* Oxycarbon will be administered by mechanical ventilation<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time to decrease of tissue oxygenation index by 20 % | Parameter will be measured by NIRS | 1 Day | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| PaO2 (Oxygen partial pressure) | Parametere will be measured by arterial bloodgas | 1 Day | 
| SpO2 (oxygen saturation) | Parametere will be measured by arterial bloodgas | 1 Day | 
| PCO2 ( partial pressure of carbon) | Parametere will be measured by arterial bloodgas | 1Day | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
cerebral hypoxia, CO2, cerebral perfusion, hypoxia