Dexmedetomidine (Precedex)

Anesthesia Implications

Classification: Central-acting alpha 2 agonist
Therapeutic Effects: Anxiolytic, Antisialogue, Sedation, Analgesia, Sympatholytic, Profoundly reduces plasma catecholamines
Time to Onset: IV: 5 minutes
IN: 26-28 minutes
Time to Peak: 15 minutes
Duration: Half life: 90 minutes

Contraindications

Increases the risk for hypotension and bradycardia, so contraindications would include any patient predisposed to these conditions or where these conditions would create otherwise dangerous circumstances.

Primary Considerations

Clinical highlights of this drug are placed on: The benefits of sedation (particularly in pediatric patients postoperatively) and the risks of hypotension/bradycardia as common side effects.  Precedex is also becoming a commonly utilized drug choice for conscious sedation.

Rapid administration can result in temporary vasoconstriction/hypertension.  Alpha 2 receptors are stimulated which actually cause vasoconstriction.  This is overcome by reduced sympathetic outflow (its other affect).  The point is, don’t administer too quickly if vasoconstriction/hypertension is a big concern.

Precedex should be used with caution or avoided in patients with AV blocks because of its antidromic effects on the AV node. Antidromic refers to the nerve impulse going in the opposite direction.

Side effects of hypotension and bradycardia can be effectively overcome with the use of phenylephrine or ephedrine in most cases.

Causes minimal respiratory depression, which is one of this drugs greatest benefits.

Maintains hypercapnic arousal response (in contrast to opioids which blunt this response).  This benefit combined with the last point make Precedex a drug that clinicians are comfortable administering at the end of a case (during phases of emergence) where postoperative anxiety or pain are anticipated.

Significant opioid sparing properties – reduced opioid requirements intraoperatively and postoperatively

Reduces the MAC for volatile anesthetics 35-50%

As a premedication, Precedex produces anxiolysis and sedation similar to midazolam (with greater risk of hypotension and bradycardia)

The majority of research suggests that Precedex does NOT interfere with motor or sensory evoked potentials (SSEPs or MEPs). However, some providers suggest by clinical observation that it does interfere. There are research articles that also suggest this, but they tend to be the outliers.

Attenuates the sympathetic responses to intubation.  It is noted that patients undergoing fiberoptic intubation while medicated with precedex remain comfortable and cooperative.

Reduces GI kinetics causing delayed gastric emptying and prolonging GI transit

Reduces cerebral blood flow directly by stimulating alpha-mediated vasoconstriction of cerebral vessels, and indirectly as a result of reducing blood pressure.  CMRO2 is also reduced by Precedex.

Minimal subhypnotic amnesia when compared to propofol or midazolam.  If amnesia is a desired clinical outcome, hypnosis should be achieved.

Effective as an agent to help wean patients from a ventilator with minimal respiratory depression

Neuroprotective in that it reduces postoperative delirium time and promotes a more physiologic sleep

broadens the range of temperatures which would trigger thermoregulatory responses (effective against shivering but promotes hypothermia)

Alpha 2 selectivity is 7 times that of clonadine

When used alone, the sedative effects of Precedex are slower for both onset and recovery when compared to propofol

Delayed emergence when used as an adjuvant to propofol (versus propofol alone)

Little to no pain on injection.

FDA approved for sedation for diagnostic procedures performed under monitored anesthesia care (MAC) and for short term sedation (less than 24 hours) of mechanically ventilated patients

Electroconvulsive Therapy (ECT):  Precedex has been shown to effectively lower blood pressure without affecting seizure duration

IV push dose

Common pediatric IV dose: 0.25 – 0.5 mcg/kg

IV infusion dose

loading dose of 1 ug/kg over >= 10 minutes. This is followed by an infusion of 0.2 – 0.7 ug/kg/hour

Method of Action

Central acting alpha-2 agonist. This inhibits the central release of norepinephrine which effectively produces sedation and analgesia.

Analgesic affects are via the descending spinal tracts.

Metabolism

Hepatic. Inactive metabolites

Additional Notes
Pediatric PO dose: 2-5 mcg/kg
Pediatric Intranasal Dose: 1-3 mcg/kg; If using exclusively, a dose of 2.5-3.0 mg/kg is recommended for sufficient sedation to tolerate procedures such as transthoracic echocardiography.