Thiopental Dexmedetomidine

Several drugs are used intravenously, alone or in combination with other drugs, to achieve an anesthetic state (as components of balanced anesthesia) or to sedate patients in intensive care units who must be mechanically ventilated. These drugs include the following (1) barbiturates (thiopental, methohexital) (2) benzodiazepines (midazolam, diazepam) (3) opioid analgesics (morphine, fentanyl, sufentanil, alfentanil, remifentanil) (4) propofol (5) ketamine and (6) miscellaneous drugs (droperidol, etomidate, dexmedetomidine). Figure 25-2 shows the structures of... 

Dexmedetomidine can reduce the dose requirements of thiopental, isoflurane, and other similar anaesthetics. 

A placebo-controlled study in women undergoing abdominal hysterectomy found that a dexmedetomidine infusion started 15 minutes before induction of anaesthesia caused a dose-dependent reduction in isoflurane MAC (by 35% and 47% with dexmedetomidine plasma levels maintained at 0.37 and 0.69 nanograms/mL, respectively). In another study, dexmedetomidine reduced the ED50 dose requirement ofisoflurane for anaesthesia (motor response) in 9 healthy subjects. Dexmedetomidine plasma levels of 0.35 and 0.75 nanograms/mL reduced the requirements for isoflurane by about 30% and 50%, respectively. Subjects who had received dexmedetomidine took longer to wake up. Dexmedetomidine has sedative, analgesic and anxiolytic effects and therefore, like other sedatives, may reduce the dose requirements of anaesthetics. However, it may also affect the distribution of thiopental and possibly other intravenous anaesthetics. 

Btlhrer H Mappes A, Lauber R, Stanski DR, Maitre PO Dexmedetomidine decreases thiopental dose requirement and alters distribution pharmacokinetics Ams iesiology (1994) 80, 1216-27. 

Myoclonus is observed in 50-80% of patients receiving induction of anesthesia with etomidate and is associated with postoperative discomfort. Pretreatment with an opioid, a benzodiazepine, and magnesium sulfate reduces the incidence of myoclonus but does not completely prevent it. The effect of pretreatment with dexmede-tomidine or sodium thiopental on etomidate-related myoclonus has been studied in 90 ASA I-II patients undergoing elective surgery, who were randomized to 0.9% saline (n=30), dexmedetomidine 0.5 micrograms/kg ( =30), or sodium thiopental 1 mg/kg ( =30) administered by infusion over 10 minutes and followed 1 minute later by etomidate 0.3 mg/kg over 60 seconds [24. There were fewer cases of myoclonus in those who received dexmedetomidine or sodium thiopental (68% and 64% versus 36% of controls). 

Mizrak A, Koruk S, Bilgi M, Kocamer B, Erkutlu I, Ganidagli S, Oner U. Pretreatment with dexmedetomidine or thiopental decreases myoclonus after etomidate a randomized, double-blind controlled trial. J Surg Res 2010 159 ell-6. 

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