Objective: The term THRIVE refers to the delivery of 100% heated and humidified oxygen via a nasal cannula to maintain viable gas exchange during prolonged apnea. There are no reports of its application for Operative Hysteroscopy (OH) under general anesthesia (GA). The aim of the study is to investigate the success rate of THRIVE as unique airway management technique in this setting. The results will support the development of a randomized controlled trial (RCT) to demonstrate the non-inferiority of THRIVE compared to traditional techniques.
Patients and methods: Twenty consecutive ASA I-II women presenting for OH were enrolled. Standard anesthesia, as well as transcutaneous carbon dioxide (tcCO2) monitoring, was performed. After preoxygenation with 30 L∙min-1, GA was induced with propofol and fentanyl, then oxygen flow was increased to 70 L∙min-1 and anesthesia maintained with propofol infusion. The primary outcome was success rate of THRIVE defined as SpO2 > 94%, tcCO2 < 60 mmHg and no need for rescue airway intervention.
Results: Mean age was 47 ± 12 years. Mean duration of the procedure was 25 ± 9 minutes, and the success rate of the technique was 100%. Median SpO2 during the procedure was 100 (IQR 99-100) %. Mean maximum tcCO2 level was 51 ± 7 mmHg while mean tcCO2 level during the procedure was 45 ± 7 mmHg. At the end of the procedure, mean tcCO2 was 44 ± 5 mmHg.
Conclusions: THRIVE allowed adequate gas exchange during OH under GA, without additional rescue airway interventions. The application of THRIVE in this setting may allow minimal airway manipulation and optimal comfort for the patient with low failure rate. We calculated the sample size for the planned non-inferiority RCT investigating the effectiveness of THRIVE versus laryngeal mask ventilation in OH: 82 is the minimal number of patients per group to test a non-inferiority limit of 10%.