Background: Dexmedetomidine is a highly selective central a2-agonist with anesthetic and analgesic properties for\r\npatients in intensive care units. There is little information about the relationship between dosage and plasma\r\nconcentration during long drug infusions of dexmedetomidine in critically ill patients, especially in Asians. In\r\naddition, the administration of dexmedetomidine with a dosage of 0.2ââ?¬â??0.7 Ã?µg/kg/h in Japan is different from that\r\nwith a dosage of 0.2ââ?¬â??1.4 Ã?µg/kg/h in European countries and the USA. There has been concern about obtaining an\r\neffective concentration with a small dosage and estimating the relationship between dosage and plasma\r\nconcentration. We conducted a prospective, observational, cohort study measuring plasma dexmedetomidine\r\nconcentrations.\r\nMethods: Plasma dexmedetomidine concentrations of 67 samples from 34 patients in an intensive care unit for\r\n2 months were measured by ultra performance liquid chromatography coupled with tandem mass spectrometry\r\nusing single-blind method, and the correlation coefficient between dosages and plasma concentrations was\r\nestimated. Exclusion criteria included young patients (<16 years) and samples obtained from patients in which the\r\ndosage of dexmedetomidine was changed within 3 h.\r\nResults: Among the patients, 20 (58.8%) of the 34 received dexmedetomidine at 0.20ââ?¬â??0.83 Ã?µg/kg/h, and in 40 of\r\nthe 67 samples for which dexmedetomidine had been administered, this occurred for a median duration of 18.5 h\r\n(range, 3ââ?¬â??87 h). The range of the dexmedetomidine plasma concentration was 0.22ââ?¬â??2.50 ng/ml. By comparison\r\nwith other studies, with a dosage of 0.2ââ?¬â??0.7 Ã?µg/kg/h, the patients in this setting could obtain an effective\r\ndexmedetomidine concentration. The plasma dexmedetomidine concentration was moderately correlated with the\r\nadministered dosage (r = 0.653, P < 0.01). The approximate linear equation was y = 0.171x + 0.254. The range of\r\nRichmond Agitation-Sedation Scale was 0 to -5.\r\nConclusions: We concluded that, with a dosage of 0.2ââ?¬â??0.83 Ã?µg/kg/h, the patients in this setting could obtain an\r\neffective dexmedetomidine concentration of 0.22ââ?¬â??2.50 ng/ml. In addition, the plasma dexmedetomidine\r\nconcentration was moderately correlated with the administered dosage (r = 0.653, P < 0.01).
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