What is the role of ketamine (Ketalar) in procedural sedation and analgesia (PSA)?

Updated: Sep 21, 2020
  • Author: Alma N Juels, MD; Chief Editor: Erik D Schraga, MD  more...
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Answer

Ketamine (Ketalar) elicits profound dissociative and amnestic actions. In doses typically used for PSA it does not affect pharyngeal-laryngeal reflexes and, thus, allows a patent airway as well as spontaneous respiration to maintain intact. This characteristic of the medication is particularly useful for emergency procedures when fasting is not assured. It should be mentioned, though, that reflexes may remain intact but cannot be assumed to be protective. [15] Cardiovascular and respiratory stimulation and normal or slightly enhanced skeletal muscle tone are observed following administration, although transient respiratory depression may occur if administered too rapidly or in high doses. The unique dissociative action and partial agonist at opiate mu-receptors permits painful procedures to be performed in a consistent state of sedation and patient comfort. Ketamine is contraindicated in patients who have underlying conditions in which increased blood pressure or heart rate would pose risk of complications. An increase in oropharyngeal secretions is often triggered and this can be prevented by premedication with glycopyrrolate. 

Onset of action for intravenous (IV) administration of ketamine is within 1 minute, and duration of action lasts about 10-15 minutes. The context sensitive half-life after administration is roughly 45 minutes and it does have an active metabolite with approximately 1/3 the activity of the parent compound. If administered intramuscularly (IM), the onset of action is observed in 3-5 minutes, and duration of procedural conditions lasts about 20-30 minutes.

Ketamine results in a dissociative state, and patients may not be able to speak or respond purposefully to verbal commands. Ketamine can cause vivid imagination, hallucinations, confusion, excitement, irrational behavior and severe anxiety. Emergence reactions are estimated to occur in approximately 12% of patients. Strayer and Nelson have estimated emergence phenomena to occur in between 10% and 20% of adults who have received ketamine. [16] Symptoms can be expected to last from 1-3 hours.

The incidence of emergence delirium may be reduced by decreasing the recommended dose of ketamine and using it in conjunction with a benzodiazepine. A small hypnotic dose of a short-acting benzodiazepine is recommended to terminate severe emergence reactions. Emergence delirium is not typical in children younger than 15 years. In a randomized controlled study of adult ED patients, Sener et al found that the incidence of recovery agitation was significantly reduced when midazolam was coadministered with ketamine for procedural sedation. [17]

A 1:1 mixture of ketamine with propofol can be used for procedural sedation and analgesia. This mixture has been associated with a reduced incidence of emergence delirium and may negate the need for concomitant benzodiazepine use. In a prospective case series study of 728 adults presenting to a trauma center for orthopedic procedures, the median dose of ketamine and propofol was 0.7 mg/kg. Bag-mask ventilation occurred in 21%, and recovery agitation occurred in 3.6% (50% of these patients required treatment for agitation). [18]

A double-blind, randomized trial compared ketamine (0.5 mg/kg) plus propofol with placebo plus propofol in 193 adults and children. Respiratory depression was similar between the groups but less propofol was needed when ketamine was administered, and there was trend toward better sedation quality. [12]

A prospective trial comparing ketamine plus propofol (ketofol) to midazolam plus fentanyl (MF) was conducted in the emergency setting by Nejati et al. Patients (n=62) requiring procedural sedation and analgesia for deep traumatic lacerations and reduction of bone fractures were included. No significant differences were observed for sedation time or physician satisfaction between the groups. Pain was significantly lower in the ketofol group compared with the MF group (p < 0.001). [13]

The use of ketamine and propofol is a potential alternative in adults requiring procedural sedation.


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