"improving intensive care in Scotland"

Centrally acting alpha-adrenoreceptor agonists

  • Clonidine and dexmedetomidine are selective alpha-2-adrenoreceptor agonists.

  • Their centrally (within the CNS) mediated actions include: sedation, anxiolysisanalgesiareduced sympathetic output and an anti-sialogogue.

  • They have the benefits over other sedatives of providing both sedation and analgesia but with minimal respiratory depression.

  • They have the downside of bradycardia and hypotension from the reduced sympathetic output, but also do cause a transient initial increase in blood pressure on commencement from an initial stimulation of catecholamine release.

  • Rebound hypertension on the abrupt withdrawal of these agents has been described, necessitating its tapered withdrawal.

  • Their role in ICU sedation has not been clearly defined.

  • Potential roles are:

    • Managing drug withdrawal states

    • Rapid post-operative weaning

    • Managing sympathetic storms (e.g. head injuries)

  • Dosing:

    • Clonidine:

      • Loading dose: 1-2mcg/kg over 10 mins

      • Maintenance: Infusion of 0.1-2mcg/kg/hr

  • Clonidine is 50% metabolised to inactive metabolites in the liver but with the remaining 50% being excreted unchanged in the urine, accumulation will occur in renal dysfunction.

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