Ultrasound assessment of gastric insufflation in obese patients receiving transnasal humidified rapid-insufflation ventilatory exchange during general anesthesia induction

Abstract

To assess the effect of transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) on gastric insufflation during general anesthesia induction in obese patients. Ninety obese patients (BMI 30-39.9 kg/m2) undergoing laparoscopic cholecystectomy under general anesthesia were randomized into 3 groups (n=30) to receive facemask pre- oxygenation followed by face mask ventilation (FMV) after administration of anesthetics (Group M), oxygenation with THRIVE (Group T), or pre-oxygenation with facemask combined with THRIVE followed continuous oxygenation with both FMV and THRIVE after administration of anesthetics (Group M+T). The patients in the latter two groups received continuous oxygen via THRIVE during tracheal intubation. All the patients received real-time ultrasound monitoring of the gastric antrum, and positive gastric insufflation (GI+) was defined by the presence of comet-tail artifacts. The cross-sectional area of the gastic antrum (CSA-GA) was measured by ultrasound before and after pre-oxygenation and after intubation. The patients' SpO2, PaO2, and PaCO2 at admission (T1), 5 min after pre-oxygenation (T2), 5 min after medication (T3), and immediately after intubation (T4) were recorded, and the incidence of postoperative adverse events was assessed. The incidence of gastric insufflation was significantly higher in Group M and Group M+T than in Group T (P < 0.05). The CSA-GA was significantly greater at T4 than at T1 in Group M and Group M+T and in their GI+s ubgroups. The GI+ subgroups in Group M and Group M+ T had significantly larger CSA-GA at T4 than the GI- subgroups (P < 0.05). CSA-GA did not vary significantly during anesthesia induction in Group T (P>0.05). The incidence of grade Ⅰ gastric distension was lower but grade Ⅱ gastric distention was higher in Group M and Group M+T than in Group T (P < 0.05). Group M showed significantly greater variations of PaO2 at T3 and T4 than Group T and Group M+T (P < 0.05). Ultrasound monitoring of the comet tail sign and the changes of CSA-GA in the gastric antrum is feasible and reliable for detecting gastrointestinal airflow, and in obese patients, the application of THRIVE for induction of anesthesia can ensure the oxygenation level without further increasing gastric insufflation.