Ketamine
Ketalar
Ketamine is a rapid-acting general anesthetic producing an anesthetic state characterized by profound analgesia, normal pharyngeal-laryngeal reflexes, normal or slightly enhanced skeletal muscle tone, cardiovascular and respiratory stimulation, and occasionally a transient and minimal respiratory depression.
A patent airway is maintained partly by virtue of unimpaired pharyngeal and laryngeal reflexes. It is used as the sole anesthetic agent in procedures that do not require skeletal muscle relaxation. It can also be administered for anesthesia prior to the use of other anesthetic agents or to supplement low-potency agents such as nitrous oxide. Ketamine is used only rarely in gastrointestinal endoscopy .
Available in the following strengths: Injection 10 mg/mL; Injection 50mg/mL; Injection 100 mg/mL
Ketamine Dosing for Endoscopy Adult - Initial IV dose: 0.5 mg/kg
- Additional doses: Titrate to effect
- Onset of action: Less than 1 minute
- Peak effect: 1 minute
- Duration of effect: 10-15 minutes
Pediatric - Initial IV dose: 0.5-1 mg/kg (max bolus dose 70mg) via slow infusion (over 60 sec)
- Additional doses: 0.25-0.5 mg/kg as necessary to maximum of 2 mg/kg.
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Notes:
- The 100 mg/mL concentration of ketamine should not be injected intravenously without proper dilution. It is recommended the drug be diluted with an equal volume of either sterile water for injection, USP, normal saline, or 5% dextrose in water.
- It is recommended that ketamine administered slowly (over a period of 60 seconds).
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Ketamine has a wide margin of safety; several instances of unintentional administration of overdoses (up to ten times that usually required) have been followed by prolonged but complete recovery.
Respiratory depression may occur with overdosage or too rapid rate of administration of ketamine, in which case supportive ventilation should be employed. Mechanical support of respiration is preferred to administration of analeptics.
- Use in pregnancy: Since the safe use in pregnancy, including obstetrics (either vaginal or abdominal delivery), has not been established, such use is not recommended.
- Geriatric Use: Clinical studies of ketamine hydrochloride did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
- Pediatric Use: Safety and effectiveness in pediatric patients below the age of 16 undergoing gastrointestinal procedures have been described in several peer review publications
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- Cardiovascular: Blood pressure and pulse rate are frequently elevated following administration of ketamine alone. However, hypotension and bradycardia have been observed. Arrhythmia has also occurred.
- Respiration: Although respiration is frequently stimulated, severe depression of respiration or apnea may occur following rapid intravenous administration of high doses of ketamine. Laryngospasm and other forms of airway obstruction have occurred during ketamine anesthesia.
- Eye: Diplopia and nystagmus have been noted following ketamine administration. It also may cause a slight elevation in intraocular pressure measurement.
- Psychological: Manifestations vary in severity between pleasant dream-like states, vivid imagery, hallucinations, and emergence delirium. In some cases these states have been accompanied by confusion, excitement, and irrational behavior which a few patients recall as an unpleasant experience.
- Neurological: In some patients, enhanced skeletal muscle tone may be manifested by tonic and clonic movements sometimes resembling seizures.
- Gastrointestinal: Anorexia, nausea and vomiting have been observed; however, this is not usually severe and allows the great majority of patients to take liquids by mouth shortly after regaining consciousness.
- General: Anaphylaxis
- Skin: Local pain and exanthema at the injection site have infrequently been reported. Transient erythema and/or morbilliform rash have also been reported.
- Ketamine should be used by or under the direction of physicians experienced in administering general anesthetics and in maintenance of an airway and in the control of respiration. Therefore, its use by gastroenterologists in ambulatory settings is rare.
- Because pharyngeal and laryngeal reflexes are usually active, ketamine should not be used alone in surgery or diagnostic procedures of the pharynx, larynx, or bronchial tree. Mechanical stimulation of the pharynx should be avoided, whenever possible, if ketamine is used alone. Muscle relaxants, with proper attention to respiration, may be required in both of these instances.
- Resuscitative equipment should be ready for use.
- The incidence of emergence reactions may be reduced if verbal and tactile stimulation of the patient is minimized during the recovery period. This does not preclude the monitoring of vital signs
- Use with caution in the chronic alcoholic and the acutely alcohol-intoxicated patient.
- An increase in cerebrospinal fluid pressure has been reported following administration of ketamine. Use with extreme caution in patients with preanesthetic elevated cerebrospinal fluid pressure.
- Drug Interactions:
- Ketamine is clinically compatible with the commonly used general and local anesthetic agents when an adequate respiratory exchange is maintained.
- Prolonged recovery time may occur if the following drugs are used concurrently with ketamine:
- Barbiturates such as amobarbital, butabarbital, mephobarbital, secobarbital, or phenobarbital.
- Narcotic medications such as fentanyl, hydrocodone, hydromorphone, methadone, morphine, oxycodone, propoxyphene, and others.
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- Emergence reactions:
- At high doses , emergence reactions have occurred in approximately 12 percent of patients.
- The incidence of these emergence phenomena is least in the elderly (over 65 years of age) patient. Also, they are less frequent when the drug is given intramuscularly and the incidence is reduced as experience with the drug is gained.
- Psychological manifestations:
- The psychological manifestations vary in severity between pleasant dream-like states, vivid imagery, hallucinations, and emergence delirium. In some cases these states have been accompanied by confusion, excitement, and irrational behavior which a few patients recall as an unpleasant experience. The duration ordinarily is no more than a few hours; in a few cases, however, recurrences have taken place up to 24 hours postoperatively. No residual psychological effects are known to have resulted from use of ketamine.
- The incidence of psychological manifestations during emergence, particularly dream-like observations and emergence delirium, may be reduced by using lower recommended dosages of ketamine in conjunction with intravenous diazepam during induction and maintenance of anesthesia. Also, these reactions may be reduced if verbal, tactile and visual stimulation of the patient is minimized during the recovery period. This does not preclude the monitoring of vital signs.
- Management:
- In order to terminate a severe emergence reaction the use of a small hypnotic dose of a short-acting or ultrashort-acting barbiturate may be required.
- When ketamine is used on an outpatient basis, the patient should not be released until recovery from anesthesia is complete and then should be accompanied by a responsible adult.
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Ketamine hydrochloride is a nonbarbiturate anesthetic medication. Another anesthetic agent used for endoscopic sedation is propofol.
- Ketamine should not be used in those in whom a significant elevation of blood pressure would constitute a serious hazard. Elevation of blood pressure begins shortly after injection, reaches a maximum within a few minutes and usually returns to preanesthetic values within 15 minutes after injection. In the majority of cases, the systolic and diastolic blood pressure peaks from 10% to 50% above preanesthetic levels shortly after induction of anesthesia, but the elevation can be higher or longer in individual cases.
- Individuals who have shown hypersensitivity to ketamine should not use the drug.
SourcesBleiberg AH, Salvaggio CA, Roy LC et al. Low-dose ketamine: efficacy in pediatric sedation.
Pediatr Emerg Care. 2007 Mar;23(3):158-62.
Cohen LB, DeLegge MH, Aisenberg J, Brill JV, Inadomi JM, et al.
AGA Institute review of endoscopic sedation. Gastroenterology. 2007 Aug;133(2):675-701.
Ketalar. RxList.com.
http://www.rxlist.com/cgi/generic/ketamine.htm. 2008. Accessed February 28, 2008.
Ketamine Hydrochloride Injection [package insert]. Bedford Laboratories. October 2006.
http://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2145 Accessed April 20, 2008
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Last Updated October 9, 2008