Utility of the auditory evoked potentials index as an indicator for endotracheal intubation

The A-line ARX Index (AAI) has been used as an indicator of depth of anesthesia. The study examined whether AAI-guided endotracheal intubation (EI), compared with experience guidance, could provide better hemodynamic stability during general anesthesia (GA).

One hundred and four patients were included in this study. In the control group, EI was performed based on the judgment of the anesthesiologist by clinical experience. In the study groups, EI was performed at an AAI value of either 15, 20, or 30. GA was induced with cisatracurium, lidocaine, fentanyl, thiamylal and succinylcholine. Heart rate (HR) and mean arterial pressure (MAP) were recorded at baseline, 1 min before and 1 and 3 min after intubation. The change of hemodynamics over 20% in the space between 1 min before and after intubation was defined as severe change.

The incidences of severe changes of HR and MAP in the AAI-15 and AAI-20 groups were significantly lower than those in the control group (19% and 39% vs. 68%, P < 0.01 and 0.05; 52% and 52% vs. 91%, P < 0.01, respectively). The induction time was significantly shorter in the control group than that in the study groups (183 +/- 47 vs. 366 +/- 151, 248 +/- 53, and 255 +/- 85 sec, P < 0.01). Highest dose of thiamylal and longest induction time were needed in the AAI-15 group.

Compared with the routine clinical practice, AAI monitoring helps to achieve better condition for EI during induction with less hemodynamic changes. The AAI value of 20 is suggested as an optimal indicator for EI.