Hyomental distance measured ultrasonography versus weight-based criteria for laryngeal mask size selection in children: a randomized controlled trial

Typically, when choosing a size for a child’s laryngeal mask airway (LMA), weight is considered; however, this approach has limitations. This study evaluated the efficacy of ultrasonography (US) measured hyomental distance (HMD) compared to weight-based criteria for optimizing the selection of LMA size in pediatrics. This randomized controlled trial included 60 children aged 3–14 years scheduled for surgery requiring LMA. Patients were randomized equally to two groups. LMA size was selected based on either US-measured HMD [< 2 cm for size 2, 2–3 cm for size 2.5, and > 3 cm for size 3] in the HMD group or weight-based [size 2 for 10 to 20 kg, size 2.5 for 20 to 30 kg, and size 3 for 30 to 50 kg] in the control group (C Group). The success rate (the proportion of cases where the first-selected LMA size required no adjustment or alternative devices) was significantly higher in the HMD group compared to the control group (93.33 vs. 70%, p = 0.041). LMA placement five-point optimization scores (1: easiest insertion, 5: impossible) and a two-point scale (0: optimal cuff symmetry/esophageal alignment, 1: suboptimal) were significantly better in the HMD group (p < 0.05). The HMD method demonstrated superior predictive value for successful intubation with 98% sensitivity and 72.7% specificity, compared to weight-based criteria with 87.8% sensitivity and 9.1% specificity (p < 0.001). US-measured HMD in pediatrics provides a superior method for choosing LMA size in children than traditional weight-based criteria, resulting in improved intubation success rates, better optimization scores, and higher predictive accuracy, aligning with prior studies in neonates and adults. We recommend HMD as a more reliable metric for pediatric LMA sizing. The Pan African Clinical Trial Registry was notified about the trial before patient recruitment (PACTR202306740935710, registration date: 09 Jun 2023).