Hypoxemia
Conditions
Keywords
Hypoxemia, tavns
Brief summary
Hypoxemia is a common complication in the post-anesthesia care unit (PACU) and represents one of the most meaningful factors associated with poor patient prognosis. Obese patients have a relatively higher incidence of hypoxemia. This may be partly attributable to their unique physiological characteristics. In addition, surgical trauma triggers a systemic inflammatory response with the release of pro-inflammatory factors such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). These mediators increase pulmonary capillary permeability, induce pulmonary edema, and further impair gas exchange. Surgically-induced stress elevates sympathetic tone and reduces vagal activity, which alters bronchial tone and respiratory rhythm and consequently compromises pulmonary function.Postoperative hypoxemia not only prolongs recovery time and increases the likelihood of ICU admission, but severe episodes may also lead to arrhythmia, myocardial ischemia, long-term cognitive and psychiatric disorders, and even cardiac arrest and death. These outcomes impair postoperative recovery and long-term prognosis, prolong hospital stay, and raise healthcare costs. Although strategies such as postoperative semi-recumbent positioning and intraoperative protective ventilation have been explored, there are currently no preferred interventions or clear clinical guidelines for the prevention of postoperative hypoxemia. As a non-invasive technique, transcutaneous auricular vagus nerve stimulation (taVNS) activates the auricular branch of the vagus nerve by stimulating the cymba conchae. Vagal activation suppresses macrophage activity and reduces the release of pro-inflammatory cytokines including TNF-α, IL-1β, IL-6 and IL-18, thereby attenuating pulmonary inflammation and edema and improving oxygenation. Afferent vagal signals project to the nucleus tractus solitarius, modulating the medullary respiratory center, respiratory rate and ventilation efficiency. taVNS is easy to perform, safe, applicable in the perioperative period, and has shown promising effects in regulating inflammatory conditions. This study aims to investigate whether perioperative taVNS reduces the incidence of hypoxemia in the PACU by attenuating excessive sympathetic activation and mitigating pulmonary and systemic inflammatory responses.
Interventions
Intervention Timing of Transcutaneous Auricular Vagus Nerve Stimulator: The intervention will begin 30 minutes before anesthesia induction and continue until the end of the surgery, terminating after the removal of the endotracheal tube in the PACU. The stimulation parameters are set as follows: frequency 20 Hz, pulse width 200 μs, 30 seconds on / 30 seconds off, with the current intensity set to the maximum amplitude the patient can tolerate (just below the pain threshold).
Sponsors
Affiliated Hospital of Nantong University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
Age ≥18 years; Scheduled for elective bariatric surgery; Classified as American Society of Anesthesiologists (ASA) physical status I to III; Capable of understanding the study procedures and various assessment scales and able to effectively communicate with the researchers; Willing to participate in the study and provide written informed consent.
Exclusion criteria
Patients with severe underlying cardiopulmonary diseases (e.g., acute exacerbation of chronic obstructive pulmonary disease, acute myocardial infarction, NYHA class Ⅳ heart failure); Patients with resting SpO₂ \<90% before surgery; Patients with a preoperative heart rate below 50 beats per minute or severe arrhythmia; Patients with lesions of the auricular concha (e.g., inflammation, ulcer, deformity, implant) or vagus nerve dysfunction (e.g., diabetic peripheral neuropathy, vagus nerve injury due to prior neck surgery); Patients with a history of implanted stimulators (e.g., pacemakers, implanted vagus nerve stimulators, deep brain stimulators, spinal cord stimulators), cochlear implants, or metallic implants (excluding dental work); Patients with cognitive dysfunction (MMSE score \<20), psychiatric disorders, or unable to cooperate with study procedures; Patients who received vagus nerve stimulation or acupuncture within 1 month before the study; Patients with skin damage or dermatological conditions at the electrical stimulation site; Pregnant or lactating women; Patients requiring emergency surgery; Patients participating in other clinical trials.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Incidence of Postoperative Hypoxemia in the PACU | Within 30 minutes in the PACU postoperatively | Numerous clinical studies and consensus statements define hypoxemia as either peripheral oxygen saturation (SpO₂) less than 90% lasting for more than 10 seconds, or a partial pressure of arterial oxygen to fraction of inspired oxygen (PaO₂/FiO₂) ratio less than 300 mmHg during PACU stay. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Incidence and First Onset Time of Moderate Hypoxemia in the PACU | Within 30 minutes in the PACU postoperatively | Moderate hypoxemia is defined as SpO₂ less than 85% lasting for more than 10 seconds during PACU stay.The first onset time was defined as the time interval from extubation to the first onset of severe hypoxemia. |
| Incidence of Airway Rescue | Within 30 minutes in the PACU postoperatively | Airway rescue was defined as the implementation of non-invasive mask ventilation or re-intubation for respiratory support. |
| Time to Extubation and PACU Length of Stay | Within 30 minutes in the PACU postoperatively | The time interval from the end of surgical procedure to tracheal extubation. The time interval from PACU admission to PACU discharge. |
| Postoperative Respiratory Comfort Score | Within 30 minutes in the PACU postoperatively | Respiratory comfort was evaluated using a 0-10 numerical rating scale, with higher scores indicating better respiratory comfort and lower scores indicating more severe respiratory discomfort. |
| Incidence of Cough, Pulmonary Infection and Atelectasis within 24 hours after surgery | Within the first day post-surgery | — |
| Postoperative Visual Analogue Scale (VAS) pain score | Within the first day post-surgery | VAS scores were assessed at two states: resting state and coughing state, with scores ranging from 0 to 10 points. |
| Total Length of Hospital Stay | Up to 5 weeks postoperatively | The total length of hospital stay refers to the entire duration of the hospitalization from admission to diacharge |
| Incidence and Severity of Related Adverse Reactions | Up to 5 weeks postoperatively | Adverse reactions included ear skin erythema, local pain, dizziness, nausea, and bradycardia (heart rate \< 50 beats per minute). The severity of adverse reactions was graded according to the following standards: Grade 1, mild discomfort without the need for clinical intervention; Grade 2, symptoms relieved after symptomatic treatment; Grade 3, severe adverse reactions requiring termination of study intervention and formal clinical treatment. |
Outcome results
None listed