The Median Effective Dose(ED50) Of Dexmedetomidine For Geriatrics With Non Mechanical Ventilation In ICU

【OBJECTIVE】The primary objective was to assess the median effective dese(ED50=effective dese in 50% patients) of dexmedetomidine and 95% confidence interval for geriatrics with non mechanical ventilation,and whether has dose-sparing effect on hemodynamics,respiratory and safety.【METHODS】Prospective,randomized,sequential trial conducted in the first affiurted hospital of Soochow university between October 2014 and January 2015.The 48 geriatrics(ASA I-III,aged>65y) who were in ICU after general anesthesia operation,expected non mechanical ventilation for more than 12 h were included.They were divided into 2 groups.A group(66-79y) and B group(>80y),using Dixon sequential text.The experiment was divided into pre-experiment and sequential experiment.Pre-experiment:A experienced dose of dexmedetomidine were injected into 5 geriatrics for 20 min,then maintain volume to keep Ramsay II-III,recording Ramsay score,BIS.Calculate the required experimental target BIS range(BISM).Sequential experiment:group A:n=23,Dexmedetomidine infusion of 20 min loading dose followed by maintaining dose.Group B:n=25,method with the A.Both groups were observed wheather the lowest BIS in the 30-40 th min was in the range of BISM.If the BIS is higher than BISM,the next patient load up a grade(0.05μg/kg),otherwise the dose down a grade. BP、HR、SPO2、BIS、Ramsay Score 、respiration transmutation and adverse reactions(Beckoning bradycardia, hypotension, respiratory depression)are measured during 2h.The study was over until the presence of the BIS turning point higher than or equal to BISM at least 7 times.【RESULTS】The Ramsay Score of the two groups did not change significantly after administration dexmedetomidine 20 min,it was inceased significantly after 40 min.The A group were 1.4±0.5(before administration DEX)、1.5±0.5(after administration DEX 20 min)、2.3±0.5(after administration DEX 40 min).The B group were 1.3±0.4(before administration DEX)、1.3±0.5(after administration DEX 20 min)、2.0±0.4(after administration DEX 40 min)(P<0.05)。The BIS after administration drμgs of dexmedetomidine was decreased gradually in the A, B groups.The A group were 96.1±1.7(before administration DEX)、88.8±4.2(after administration DEX 20 min)、80.3±3.0(after administration DEX 40 min).The B group were 95.42±2.0(before administration DEX)、89.3±4.1(after administration DEX 20 min)、80.7±3.4(after administration DEX 40 min)(P<0.05)The dexmedetomidine of A group was higher than that of B group.The dose of A was 0.44±0.04 while the dose of B was 0.37±0.04(P<0.05).The ED50 and CI95% of dexmedetomidine when the BIS decreased to BISM of A group was 0.43μg/kg(0.41~0.46μg/kg)while B group was 0.37μg/kg(0.34~0.40μg/kg).The HR of both groups were significantly decreased after administration dexmedetomidine.The A group was 93.0±15.2(before administration DEX)、85.7±15.4(after administration DEX 20 min)、80.1±13.5(after administration DEX 40 min).The B group was 90.0±11.7(before administration DEX)、82.3±9.6(after administration DEX 20 min)、77.8±10.0(after administration DEX 40 min)(P<0.05).The SBP of both groups were significantly decreased after administration dexmedetomidine.The A group was 139.1±21.3(before administration DEX)、128.5±15.8(after administration DEX 20 min) 、 120.4 ± 14.5(after administration DEX 40 min).The B group was 148.0 ± 16.9(before administration DEX) 、 135.8 ± 21.3(after administration DEX 20 min)、124.8±16.2(after administration DEX 40 min)(P<0.05).【CONCLUSIONS】Dexmedetomidine has a significantly effect on sedation in geriatrics with non mechanical ventilation,and can decrease BIS.The ED50 and CI95% of geriatrics(aged 65~79y) with non mechanical ventilation is 0.43μg/kg(0.41~0.46μg/kg),while geriatrics(aged>80y) is 0.37μg/kg(0.34~0.40μg/kg).Dexmedetomidine can significantly decrease HR and SBP,but have no adverse effect on respiratory.