Gastric insufflation with and without an inserted gastric tube in second-generation laryngeal mask airways: A randomized controlled cross-over trial.

STUDY

OBJECTIVE

Second-generation laryngeal mask airways are equipped with an additional lumen for a gastric tube, with the intention to reduce the risk of aspiration by draining gastric content. However, the effect of an inserted gastric tube through the gastric channel on gastric insufflation, a substantial part of the pathomechanism of aspiration, during positive-pressure ventilation is not clear. We hypothesized, that an inserted gastric tube increases the risk of gastric insufflation.

DESIGN

Single center, prospective, randomized-controlled cross-over trial.

SETTING

Tertiary academic hospital in Germany.

PATIENTS: 152 patients, ASA I-III, scheduled for general anesthesia with a laryngeal mask airway.

INTERVENTIONS: Gastric insufflation was investigated during an incremental pressure trial up to a maximum airway pressure of 30 cmH2O and during oropharyngeal leak pressure measurement with and without an inserted gastric tube while one of two laryngeal mask airways with different cuff designs (inflatable or thermoelastic) was used.

MEASUREMENTS: Gastric insufflation was detected with real-time ultrasound.

MAIN

RESULTS

Frequency of gastric insufflation was higher with than without inserted gastric tube during the incremental pressure trial (10.9 % (16/147) vs. 2.7 % (4/147), p = 0.009) and during oropharyngeal leak pressure measurement (16.3 % (24/147) vs. 5.4 % (8/147), p = 0.004). Risk of gastric insufflation didn't differ between the two cuff-types (p = 0.100). Flow over the open gastric channel was associated with gastric insufflation during positive-pressure ventilation (p = 0.003) and during oropharyngeal leak pressure measurement (p = 0.049). Incidence of postoperative nausea and vomiting was higher in patients in which gastric insufflation was detected, compared to others (17.1 % (6/35) vs. 5.4 % (6/112), p = 0.037).

CONCLUSION

Placement of a gastric tube through the gastric channel of a second-generation laryngeal mask airway, independent of the cuff-type, increases the risk of gastric insufflation. Flow over the gastric channel indicate a higher risk of gastric insufflation and gastric insufflation may increase the risk of postoperative nausea and vomiting.