Ketamine and Midazolam for Procedures in Adults
abstract & commentary
Source: Chudnofsky CR, et al. A combination of midazolam and ketamine for procedural sedation and analgesia in adult emergency department patients. Acad Emerg Med 2000;7: 228-235.
Ketamine is used widely for pediatric conscious sedation and analgesia during painful ED procedures. Its use in adults, however, has been limited because of concerns regarding adverse and emergence reactions. In this prospective, observational study, the authors report their experience using ketamine with midazolam for procedural sedation in adult ED patients.
The investigators studied vital signs, adequacy of sedation using an alertness scale, adverse effects, emergence reactions, patient satisfaction, and time to attainment of discharge alertness. Data were collected prospectively by respiratory therapists who monitored patients during procedure and recovery, although physicians verified any adverse reactions. Severity of emergence reactions was graded based on retrospective chart review.
The authors report on 70 patients (ages 18-68 years) who received intravenous ketamine (2 mg/kg) after midazolam (0.07 mg/kg) for sedation prior to painful procedures (primarily incision and drainage or fracture/joint reduction). Adequacy of sedation was excellent, with mean ketamine doses of 159 mg and midazolam doses of 5.6 mg. Seven patients (10%) suffered adverse effects, including respiratory depression (4 patients), vomiting (2 patients), and myoclonia (1 patient). These effects were transient and easily treated (by oral airway or brief assisted bagging for respiratory depression) and did not affect disposition. Five patients (7%) experienced mild emergence reactions, including anxiety (2 patients), euphoria (2 patients), and calling out during recovery (1 patient). Eighteen patients (26%) recalled dreaming, but only five (7%) described the dreams as unpleasant. There was an increase in systolic blood pressure (mean increase of 26 mmHg), diastolic blood pressure (19 mmHg), and heart rate (21 bpm). All patients but one were satisfied and would choose the same sedation regimen. Mean time to discharge alertness was 64 minutes (range, 20 to 130 minutes). Based on their findings, the authors conclude this combination provides effective and safe procedural sedation and analgesia for adult ED patients.
Comment by Theodore C. Chan, MD, FACEP
Ketamine causes dissociation between the cortical and limbic systems, resulting in profound sedation and analgesia while maintaining respiratory reflexes. While its use in children has been successful, experience with adults in this country has been limited. This study provides one of the largest case reviews of the adult use of ketamine with midazolam and strongly suggests the combination is safe and effective for procedural sedation.
However, a few points of caution must be considered. First, by inhibiting catecholamine reuptake, ketamine acts as a sympathomimetic agent and should be used with caution in those with ischemic heart disease, hypertension, or other cardiac risk factors, as well as in those of older age. Second, while midazolam reduces the incidence of emergence reactions, the combination should be avoided in those with a history of psychosis (including drug-induced psychosis), who may be at higher risk for developing these types of adverse reactions. Finally, while respiratory compromise is rare with ketamine, excessive doses of midazolam may result in significant respiratory depression, as seen in 6% of patients in this series (all of whom weighed > 97 kg and received correspondingly large doses of midazolam). The authors’ cautionary note that such large doses of this medication in combination with ketamine should be avoided seems prudent.
Because of the risk of adverse reactions, ketamine should be avoided in:
a. infants.
b. women of childbearing age.
c. young adults with a family history of schizophrenia.
d. older adults with a history of coronary artery disease.
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