Hyperoxia on Ventilation During Recovery From General Anesthesia

Study Overview
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Brief Summary
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In this preliminary, crossover investigation the investigators will examine the effect of oxygen supplementation on the recovery of breathing in the immediate post-anesthesia period.

Detailed Description
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In a pilot randomized-controlled trial (NCT04723433) the investigators found that, compared with standard O2 supplementation, hyperoxia enhanced ventilation, as estimated by the fraction of time at a transcutaneous PCO2 (TcPCO2) > 45 mmHg. More specifically, patients treated with hyperoxia (O2 titrated to: SpO2 > 96%, N=10; Liberal O2) for 90 minutes post-anesthesia, spent 61.2% of the time at TcPCO2 > 45 mmHg, compared with 80.6% of the time in those receiving standard O2 supplementation (O2 titrated to: SpO2 between 90-94%, N=9; Conservative O2 - between-group difference of 19.4% (95% Confidence Intervals: -18.7% to 57.6%), ANCOVA adjusted P = 0.140]. Results were consistent across the 90-min monitoring period. With an observed effect size of 0.73, it was estimated that 30 participants per group are required, to demonstrate this difference with a power of 80% at a two-sided alpha of 5%. In a follow-up RCT (IRB-63878, NCT05379673) in 18 patients the investigators found that over a 90-minute window, the average percentage of time spent at TcPCO2 > 45mmHg for patients in the Conservative O2 group (N=9) was 57.8% (52 ± 44 minutes), compared with a 45.6% (41 ± 46 minutes) for those in the Liberal O2 group (N=9), (P=0.6134; two-sided two sample t-test). In addition, during the same period, respiratory disturbance index (RDI; events per hour) was higher in the Conservative O2 [median (range): 23.9 (11.0-78.6)], compared with the Liberal O2 group [19.6 (2.8-40.4), Mann-Whitney test, P=0.1615]. Due to the high variability observed in the evaluated respiratory parameters (i.e., TcPCO2 and upper airway obstruction expressed by Respiratory Disturbance Index), the researchers believe that a crossover, rather than a randomized controlled trial, design would improve the power and efficiency of this investigation and also provide an opportunity to characterize better those patients who respond, and separate them from those who do not respond to hyperoxia treatment. This preliminary investigation will assess how ventilation during recovery from general anesthesia is affected by conservative (Conservative O2: 90% ≤ SpO2 ≤ 94%), compared with liberal (Liberal O2: SpO2 > 96%) O2 supplementation. Using a crossover study design, the investigators aim to: a) assess the breathing pattern and estimate and compare the number of apnea/hypopnea episodes between the two interventions, and b) estimate and compare the cumulative segment of time during which the transcutaneous partial pressure of carbon dioxide (TcPCO2) will exceed 45 mmHg, between the two interventions. Hypothesis: Conservative O2 will be associated with more unstable and obstructed breathing and less time spent with TcPCO2 > 45 mmHg, compared with Liberal O2 supplementation, during recovery from anesthesia.

Official Title
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The Effect of Hyperoxia on Ventilation During Recovery From General Anesthesia: A Crossover Preliminary Investigation

Conditions
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Ventilatory Depression, Postoperative Respiratory Failure

Intervention / Treatment
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* Other: Oxygen gas


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists (ASA) physical status I-III Body mass index (BMI) less than 35 kg/m2 Scheduled to undergo robotic-assisted radical laparoscopic nephrectomy. Exclusion Criteria: Patients with a diagnosis of chronic obstructive pulmonary disorder (COPD), severe neurological, cardiopulmonary, psychiatric, or untreated thyroid disorder Chronic pain condition that is being treated with opioids Patients with a hematocrit lower than 30% at the end of surgery, or those with an excessive blood loss, requiring transfusion of blood products during surgery.

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 90 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: Non-Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: With the patients' admission to the post-anesthesia care unit and after a 20-minute-long stabilization period, two 40-minute-long treatment sessions will be applied to the study patients, always in the same order, which will not be revealed to the participants before completing the study. In the first treatment session (Conservative O2), O2 supplementation will be titrated to an SpO2 between 90% and 94%, while in the second session (Liberal O2), O2 administration will be titrated to an SpO2 > 96%.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Conservative O2<br>During the first treatment session, which will last for 40 minutes, O2 supplementation will be titrated to an SpO2 between 90% and 94%. | Other: Oxygen gas<br>* Administration of Oxygen by inhalation<br>|
| Experimental: Liberal O2<br>During the second treatment session, which will last for 40 minutes, O2 supplementation will be titrated to an SpO2 > 96%. | Other: Oxygen gas<br>* Administration of Oxygen by inhalation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Respiratory disturbance index (RDI) | The number of apnea/hypopnea episodes detected using respiratory inductance plethysmography and nasal flow. | Forty minutes of monitoring for each treatment arm | 
| Transcutaneous carbon dioxide pressure (TcPCO2) | The cumulative segment of time during which the transcutaneous partial pressure of carbon dioxide will exceed an upper limit of 45 mmHg (i.e., TcPCO2 > 45 mmHg) | Forty minutes of monitoring for each treatment arm |