Objective To study the age difference of remifentanil in pharmacokinetics. Methods ASA class Ⅰ or Ⅱ patient,s undergoing selective operation under general anestesia were assigned into group A (65 to 82 years old) and group B(18 to 64 years old) with 60 cases each. Remifentanil 4 μg/kg was infused during induction. Arterial blood samples 1 ml were taken at 1,2,3,5,7,10,15,20,25,30,45,60 min after injection and the concentrations of remifentanil were detected using liquid-liquid extraction and capillary GC-MS-SIM. Results The values of elimination half-tirne(t_(1/2β)), volume distribution(Vd) and clearance(CL) were significantly higher in group A than those in group B[t_(1/2β), (18. 1±9. 2) min vs. (9. 4±4. 6) min, Vd, (60.7±18.2) L vs. (45.3±10.6)L, CL, (2.1±0.3) L/min vs. (3.8±0.4) L/min](P<0.05). Conclusion The t_(1/2β),Vd and CL are significantly higher in the elderly than those in the younger.

Objective To compare the pharmacokinetics of remifentanil during general anesthesia in children and adults.Methods Eight children(4 male,4 female)and 8 adults(4 male,4 female),undergoing elective operation under general anesthesia,were randomly divided into 2 groups(n=8 each):group adults(aged 19-60 yr,weighing 45-81 kg)and group children(aged 10 months-7 yr,weighins 7.2-21.0 kg).Remifentanil 5μg/kg was injected intravenously during induction of anesthesia.Arterial blood samples 1.0 ml were taken at 1,2,3,5,7,10,15,20,25,30,45 and 60 min after injection for determination of the plasma concentrations of remifentanil.The pharmacokinetic parameters were calculated using software 3P97.Results Elimination half-life was significantly shorter and apparent volume of distribution and clearance were significantly greater in children than in adults(P<0.05),while no significant change was found in the other pharmacokinetic parameters between the two groups(P>0.05).Conclusion There is difference in the pharmacokineties of remifentanil during general anesthesia between children and adults.The plasma concentration of remifentanil is lower in children than in adults after using the same dose,and the dose should be increased appropriately.

Objective To evaluate the effect of dexmedetomidine on autophagy in the hippocampal neurons of rats with traumatic brain injury (TBI).Methods Adult male Sprague-Dawley rats,aged 12-16 weeks,weighing 340-370 g,were randomly divided into 3 groups (n=80 each) using a random number table:sham operation group (group S),traumatic brain injury group (group TBI) and dexmedetomidine group (group Dex).The rats were subjected to a diffuse cortical impact injury caused by a modified weight-drop device to induce TBI.Dexmedetomidine 15 μg/kg was injected intravenously immediately after TBI in Dex group.At 24 and 48 h after TBI,neurological deficit score (NDS) was assessed,Morris water maze test was performed,and brains were removed for detection of brain water content in the brain tissue.At 6,12,24 and 48 h after TBI,the expression of hippocampal LC3]Ⅱ was determined using Western blot analysis.Results Compared with group S,brain water content and NDS were significantly increased at 24 and 48 h after TBI,the escape latency was prolonged,and the expression of hippocampal LC3 Ⅱ was upregulated at 6,12,24 and 48 h after TBI in TBI group.Compared with TBI group,brain water content and NDS were significantly decreased at 24 and 48 h after TBI,the escape latency was shortened,and the expression of hippocampal LC3 Ⅱ was down-regulated at 6,12,24 and 48 h after TBI in Dex group.Conclusion The mechanism by which dexmedetomidine reduces TBI is related to inhibition of autophagy in the hippocampal neurons of rats.