What is the role of ketamine in emergency department (ED) sedation?

Updated: Nov 06, 2018
  • Author: Arul M Lingappan, MD; Chief Editor: Erik D Schraga, MD  more...
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Answer

Answer

Ketamine is a dissociative anesthetic and analgesic with a short duration of action. It is unique in that it produces a state in which respiration and airway reflexes are maintained while patients are unaware of their surroundings. At lower doses, patients can respond to simple commands, but they seem to be unaware of painful stimuli. It rarely produces hemodynamic depression.

Ketamine is water soluble and lipophilic. Given intravenously, the onset of action is rapid (causing minimal pain at the injection site), and the duration of action is about 15-30 minutes. The dose recommended is 1-2 mg/kg IV, which typically produces a full dissociative state, though some data suggest that adequate sedation is possible with smaller doses. [17] The emergence reaction (ie, hallucinations developing during recovery from the dissociative state) is one adverse effect. It is more severe in adults and can be attenuated with the administration of a benzodiazepine (eg, midazolam) before recovery. [1]

Ketamine usage has a few adverse effects. Laryngospasm is arguably the most feared adverse reaction. Although laryngospasm usually is manageable with conservative techniques, expertise and equipment must be available to manage the airway in this situation. Ketamine also inhibits catecholamine reuptake at the neuromuscular junction, which leads to slight increases in the heart rate, blood pressure, and cardiac output. In children, ketamine can cause increased salivary and respiratory tract secretions; it can be given with atropine to mitigate this effect (0.01 mg/kg; not to exceed 0.5 mg/dose).

Because of the emergence phenomenon, much of the data on ketamine come from the pediatric population. It is a good choice in children when analgesia and unconsciousness are required (eg, for the repair of a complex facial laceration). [1] In a recent study surveying procedural sedation practices in pediatric EDs, ketamine was by far the most commonly chosen sedation agent for extremity reduction. [18] It is useful in adults, as well.

Ketamine causes bronchial smooth muscle relaxation, making it the preferred drug for sedation/analgesia in patients with asthma. [1] Also, since its cardiovascular effects are minimal, it is another agent to consider for use in hemodynamically unstable patients (eg, induction for intubation). [1] Moreover, it shows promise as a preferred drug in patients with traumatic brain injury, countering former claims of increased intracranial pressure with ketamine usage. [19, 20]

Ketamine has also been used at subdissociative doses (0.1-0.5 mg/kg) as an analgesic in conjunction with sedative-amnestic medications. One study comparing subdissociative-dose ketamine with fentanyl during sedation with propofol showed fewer episodes of hypoxia and hypoventilation with the former. [21]


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