Test 1: Dexmedetomidine Flashcards
How does Dexmedetomidine compare to Clonidine in terms of alpha 2 agonism?
Clonidine α2:α1 = 220:1
Dexmetomidine α2:α1 = 1620:1
Dex is a highly specific α2-adrenergic agonist
Drug class: Imidozalines (alpha agonists)
Can Dex be used as a sole agent for patients with neuromuscular blockade?
No, limited amnestic effect.
Has sedative effects, but does not produce GA even at high doses.
-Patients tend to be easily arousable
-Minimal effects on respiratory drive
-Can continue infusions throughout emergence and during weaning from mechanical ventilation.
What are the analgesic qualities of Dex?
-Augments the effects of opioids
-Spinal and supraspinal (locus coeruleus) mechanism
-Hypnosis results from stimulation of Alpha 2 receptors in the locus coeruleus
-Analgesic effects originate at the level of the spinal cord.
What is the MOA of Dexmedetomidine?
The alpha 2A subtype mediates the majority of the analgesic and sedative effects on the CNS.
-HIGHLY selective, centrally acting alpha2 agonist
-Hyperpolarization due to efflux of K+ ions, which leads to a subsequent decrease in neuronal firing as well as reduced norepinephrine release mediated by inhibitory presynaptic autoreceptors.
-Stimulation of Alpha 2 receptors = decreased catechol release
-Inhibits Adenylyl Cyclase = decreased cAMP
Overall effects are r/t decreased sympathetic outflow.
What is important to know regarding the administration of Dex in a patient with cardiac disease?
The sympatholytic effects of Dex lead to decreased HR and BP.
-Decreased myocardial demand in response to painful stimuli (!!Blue Box!) Anti-anginal effect.
-Associated with a mortality benefit
What is important to know regarding the administration of Dex in a patient with Heart Block?
-Bradycardia can be dangerous in the setting of heart block. Use Dex with caution.
What is important to know regarding the administration of Dex in a patient with high sympathetic tone (Diabetes, elderly, or Hypovolemic)?
Significant hypotension is more likely in the setting of high sympathetic tone.
What is important to know with Loading Dose administration of Dex? (Blue box!)
Typically, Dex will lead to decreased HR and decreased BP due to sympatholytic effects.
However, direct effects on peripheral Alpha 2B and 2A receptors can lead to hypertension.
-This is seen during loading doses.
-Avoid administering as a bolus.
What are the CNS effects of Dexmedetomidine?
-Supraspinal analgesia
-Spinal analgesia
-Sedation, but patients tend to be arousable
-Decrease in CBF without changes in ICP and CMRO2
-Synergistic effect when combined with other sedative-hypnotics
-Does not interfere with electrophysiologic monitoring
What are the CV effects of Dexmedetomidine?
-Bradycardia (40% of patients)
-Variable HTN or HoTN
-Hypotension responds well to fluid and/or vasopressors
What are the Respiratory effects of Dexmedetomidine?
-Preserved respiratory drive
-Possible small to moderate decrease in Vt (no change in RR)
-Decreased salivation
-Possibly beneficial to decrease airway reactivity in patients with COPD/asthma
What are the Misc. effects of Dexmedetomidine?
-Decreased salivation (presents an advantage over Ketamine for fiberoptic intubation)
-Decreased shivering
-Infusions should not exceed 24 hours
-Can facilitate extubation in patients that become agitated when sedation is held.
-Diuretic effect
-Renal, gastroprotective, and anti-inflammatory effects
What is the onset time for Dexmedetomidine?
10-20 minutes
What are the pharmacokinetics of Dex?
-Onset = 5-10 minutes
-94% protein bound
-Metabolism: Hepatic CYPs & glucuronidation
-1/2 life = 2-3 hours
-DOA = 1-2 hours
What is the DOA of Dexmedetomidine?
60 - 120 minutes (1-2 hours)
