Influence of age on neuromuscular block effect of cisatracurium in myasthenia gravis patients

Objective To investigate the neuromuscular block effect of intravenous injection of cisatracurium in myasthenia gravis patients with different ages. Methods Fifteen geriatric patients defined as geriatric group(≥ 65 years old)with ASAⅠ-Ⅱscheduled for video-assisted thoracoscopic(VATS)thymectomy with Ⅱb MG and fifteen young-middle aged Ⅱb MG patients defined as young-middle aged group(20-50 years) with paired sex, clinical symptoms, duration of symptoms, preoperative treatment regimen, anesthesia management and surgical time were included. Neuromuscular block was monitored with TOF Watch acceleration instrument. After induction of intravenous anesthesia, 0.05mg/kg Cisatracurium was administrated intravenously, followed by increments of 0.015 mg/kg until T1/T0 was less than 5% for each patient. A double-lumen bronchial tube was intubated when T1/T0 was less than5%. 0.015 mg/kg cisatracurium was injected during the operation when T4/T1 was achieved to 25%. The dose of cisatracurium, the duration of blockade maintenance, duration of clinical action and neuromuscular block recovery index were obtained. Results There were no significant differences in tracheal doses of cisatracurium〔(0.058±0.013)mg/kg vs. (0.053±0.009)mg/kg〕and the duration of blockade〔(31.5±9.6)min vs.( 40.0±19.8)min〕between geriatric group and young-middle age group (P>0.05). The duration of clinical action of cisatracurium〔(21.6±6.7)min vs. (33.7±13.4)min〕and the time to achieve a TOFr of 25% were significantly shorter in geriatric MG group than those in young-middle aged MG group (P=0.045 , 0.037). The geriatric MG group were administrated more increments of ciastracurium than the young-middle aged MG group during surgery (P=0.025). There was no significant difference in the time to achieve a TOFr of 70%〔(49.3±16.4)min vs. (57.4±34.7)min〕and 90%〔(61.6±19.2)min vs. (64.3±35.9)min〕between geriatric MG group and young-middle aged MG group(P>0.05). Conclusions The duration of clinical action of cisatracurium in geriatric MG patients was shorted than that in young-middle aged MG patients which was different with neuromuscular block effect in normal patients. It is suggested to do more studies to estimate the influence of age on cisatracurium and other muscle relaxants in MG patients. Key words: Myasthenia gravis; Atracurium; Muscle relaxation