The characteristics of the staircase phenomenon during the period of twitch stabilization in infants in TOF mode

Summary Background Acceleromyography used to monitor the neuromuscular transmission function is available in infants and children. However, information on the so‐called staircase phenomenon during the baseline stabilization period in this population is limited. Our objective was to assess the characteristics of such phenomenon in infants in acceleromyography. Methods Thirty infants were divided into three groups: group A (aged 1–5 months, n = 10), group B (aged 6–11 months, n = 10), and group C (aged 12–24 months, n = 10). Anesthesia was induced and maintained without neuromuscular blocking agents. Patients received a supramaximal stimulus followed by TOF measurements every 15 s over the course of 30 min with a TOF‐Watch® SX. All data were collected in a notebook computer using the TOF‐Watch® SX Monitor software through optical fibers. Results The evoked T1 responses in younger infants (group A) were significantly lower than those in older infants (groups B and C) from 0–20 min. In group A, the signals increased to the maximum value of 121 ± 15% that of the control at 7.25 min and decreased toward a plateau of 113 ± 18% at 30 min. In group B, the signal heights increased to the maximum value of 143 ± 14% at 9.5 min, then decreased slowly to 136 ± 10% at 19.5 min, finally reaching 116 ± 12% at 30 min. In group C, the mean values of T1 reached the maximum of 139 ± 19% that of control at 9.5 min and finally reached 126 ± 22% of control at 30 min. Conclusions The staircase effect presents in a shorter time course and at lower degrees in smaller infants. However, in older infants, staircase effect still presents in a long period and may influence the onset time and duration of twitch depression after muscle relaxants administration.