Background: Mask ventilation could improve after administration of muscle relaxants if there is a functional obstruction of the airway, such as laryngospasm, vocal cord closure or opioid-induced muscle rigidity. On the other hand, muscle relaxants could worsen mask ventilation because they induce upper airway collapse; however, clinical studies showed that rocuronium (Roc) improved mask ventilation or it remained unchanged. In most cases Roc 0.06 mg/kgBW was used.
Objective: The optimal dose of Roc has not been studied; therefore, we studied the quality of mask ventilation with three different doses of Roc (0.3, 0.6 and 0.9 mg/kgBW) and compared them with a control group receiving saline.
Material and methods: In this prospective clinical trial 200 patients were randomized into 4 groups: NaCl (saline), Roc03 (Roc 0.3 mg/kgBW), Roc06 (Roc 0.6 mg/kgBW) and Roc09 (Roc 0.9 mg/kgBW). Mask ventilation was performed to reach a tidal volume (TV) of >5.0 ml/kgBW; maximum ventilation peak pressure (ppeak) was limited to 25 mbar. If this TV was not reached, mask ventilation was improved by better mask position, head position or/and usage of a Guedel tube (oropharyngeal airway). During mask ventilation ppeak and TV were recorded and the quality of mask ventilation was assessed with the Han and Warters scores. The quality of mask ventilation between the four groups was compared for all patients and a subgroup analysis was performed for patients of the study groups, who had to be ventilated with a Guedel tube and for obese patients (body mass index ≥26 kg/m2). A sample size calculation revealed that at least 38 patients were necessary for each group to detect a statistically significant difference between groups; it was assumed that Roc improved the efficacy of mask ventilation by 20% compared to saline (α = 0.05, 1-β = 0.8).
Results: The administration of Roc significantly improved the TV/ppeak ratio compared to saline (p = 0.04); however, this effect was irrespective of the dose. In patients who were ventilated with the Guedel tube the TV/ppeak ratio increased after Roc03 (p ≤ 0.01) and after Roc06 (p < 0.02) compared to the saline group. In obese patients who were ventilated with the Guedel tube the TV/ppeak ratio increased after Roc03 (p ≤ 0.01), after Roc06 (p = 0.03) and after Roc09 (p = 0.02) compared to the saline group. There were no significant differences between the Roc groups; however, the effect was more pronounced in the Roc03 patients compared to the other Roc groups. The Han and Warters scores were not significantly different between the Roc groups and the saline group.
Conclusion: The efficacy of mask ventilation was equal or improved after administration of Roc but did not become worse. Patients who were ventilated with a Guedel tube had higher TV/ppeak ratios after Roc03 and Roc06 compared to saline. Higher dosages (>Roc06), however, had no advantages concerning quality of mask ventilation. In obese patients who had to be ventilated with a Guedel tube, Roc also improved the efficacy of mask ventilation. We conclude that administration of Roc is effective in improving mask ventilation and this effect was seen after 30-60 s even after Roc03.
Keywords: Airway; Complications; Obesity; Rocuronium; Tidal volume.