Hyperoxia Improves Some Respiratory Outcomes Post-Anesthesia in Small Study

HOUSTON — A liberal oxygen intervention to induce hyperoxia improved respiratory disturbances in post-operative patients during recovery from anesthesia, results from a small single-blind trial revealed.

In the 10-patient study, treating to an oxygen saturation of 96% or more roughly halved respiratory disturbance events compared with a conservative target of 90-94% oxygen saturation (median 22 vs 31 respiratory disturbance index events per hour, P=0.0156), reported Scott Kutscher, MD, of Stanford University School of Medicine in California, at the annual SLEEP meeting hosted jointly by the American Academy of Sleep Medicine and the Sleep Research Society.

This difference met the primary endpoint and remained significant following adjustments for the minimum effective analgesic concentration of the total amount of opioids administered to each patient (P=0.007).

The study’s other primary endpoint, transcutaneous PCO₂ (TcPCO₂), didn’t come out significantly different between the conservative and liberal groups (46.3 vs 45.7 mm Hg, P=0.3235).

Some secondary endpoints favored hyperoxia, including mean arterial pressure during intervention sessions (95 vs 92 mm Hg, P=0.0338), oxygen pressure (302 vs 89 mm Hg, P<0.0001), and oxyhemoglobin saturation (100% vs 95%, P=0.002).

Researchers suggested that these findings may be the result of changes to the loop gain of ventilatory control, alterations to the centrally mediated response to carbon dioxide, or both.

This intervention “can help us better control post-operative complications, and patients aren’t just desaturating,” Kutscher told MedPage Today. “The standard in the post-operative field has been to not do hyperoxia, [due to] concern that you can over-oxygenate and you can actually increase CO₂. So I think we’re saying that we can actually improve breathing stability.”

While conservative oxygenation targets have been shown to outperform liberal oxygenation targets in both COVID-19 and critically ill pediatric patients, less has been known about the impacts of liberal targets in patients coming out of anesthesia. Results from a 2022 pilot trial that preceded Kutscher’s study showed that hyperoxia raised time spent with a TcPCO₂ of greater than 45 mm Hg and decreased the apnea-hypopnea index.

Kutscher’s non-randomized crossover trial was small, featuring a total of 10 patients who were recovering from anesthesia. Over the course of two 40-minute long sessions, patients received either a liberal oxygen intervention targeting an SpO₂ of at least 96% or a conservative oxygen intervention targeting 90-94% SpO₂. The first six patients received conservative oxygen intervention during the first session, followed by liberal oxygen intervention during the second. The rest received the opposite order of interventions. Patients breathed through a non-rebreather mask, connected via a Y-piece to both the oxygen and air wall outlets.

During the sessions, all patients were monitored via a home sleep apnea test performed by a sleep physician who was blinded to patient intervention assignments.

“Patients in the post-op state are at risk for airway collapse, oxygen saturation from anesthesia … But the complicated part of that is, when we define sleep apnea, part of the definition is desaturation. So if you’re giving someone oxygen, you’re just taking that out of the equation,” said Kutscher.

In order to be included, patients needed to have a physical status of I-III as defined by the American Society of Anesthesiologists, a BMI under 35, and a scheduled robotic-assisted radical laparoscopic nephrectomy. Participants were excluded if they were previously diagnosed with chronic obstructive pulmonary disorder (COPD); severe neurological, cardiopulmonary, psychiatric, or untreated thyroid disorders; a chronic pain condition for which they were being treated with opioids; hematocrit below 30% when their surgery concluded; or surgical blood loss that required a transfusion.

The average patient age was 59 years (three women, seven men). Six patients were white, two were Latino, one was Asian, and one was Black. The mean patient BMI was 29, and the average body weight was 88 kg (194 lb).

Additionally, six patients had hypertension, five had obstructive sleep apnea, three had type 2 diabetes, two had coronary artery disease, and one had asthma. Of the five patients who had obstructive sleep apnea, two were currently using continuous positive airway pressure (CPAP) therapy.

In regards to medication, six participants were taking antihypertensives, three were taking antidiabetic drugs, one was taking bronchodilators, and one was taking aspirin.

The average arterial pressure of the patient population was 105 mm Hg, the average heart rate was 71 bpm, the mean hematocrit was 44%, and the mean oxyhemoglobin saturation measured by pulse oximetry was 97.

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