A Comparison Study Between Ketamine

In: Health

16 Nov 2009

A Comparison Study Between Ketamine

Ketamine is a dissociative anesthetic agent that has been shown to be useful as a safe and effective oral sedative. The drug was first derived in 1961, and reports on human trials were begun in 1965. It is a chemical derivative of phencyclidine and cyclohexami-ne. Ketamine is unique in being effective for induction of anesthesia by either the intravenous or the intramuscular route; however, only recently has the drug been studied in subanesthetic sedative doses per oral administration. Patients who are given anesthetic doses of ketamine may appear to be awake with open eyes, yet are unaware of the environment and do not experience pain. This response is termed dissociative anesthesia, during which patients independently and continuously maintain their protective reflexes and may or may not respond appropriately to verbal or painful stimulation, depending on the level of dissociation. Patients often exhibit nonpurposeful movement independent of the stimulation. In the central nervous system, dissociative anesthesia is characterized by electroencephalographic evidence of dissociation between the limbic system and the thalamus. Ketamine also produces intense analgesia, which can be explained in part by specific suppression of the spinal cord activity necessary for transmission of pain to the higher brain centers. Anterograde amnesia is intense, which may be a beneficial effect in the consciously sedated patient. Nystagmus associated with ketamine often heralds the onset of dissociative sedation. Although nystagmus may preclude the use of the drug for operations or examinations of the eyes, this side effect is of little importance in the dental patient. Emergence delirium, including dreams and hallucinations, ranges from 5-30%, with an increased incidence reported in patients older than 16 years, female patients, patients taking high intravenous doses (>2 mgAg), and patients with a history of personality problems or frequent dreaming. Emergence delirium can also be attenuated with concomitant use of a benzodiazepine agent. Other central nervous system effects include an increase in cerebral blood flow and subsequent increase in intracranial pressure. This ketamine-induced activity is unlikely to precipitate convulsions in patients with seizure disorders and does not alter the seizure threshold in epileptic patients.

Ketamine produces cardiovascular effects that resemble a centrally mediated sympathetic stimulation. Although the mechanisms are complex, intravenous anesthetic induction doses show increases in systemic and pulmonary arterial blood pressure, heart rate, cardiac output, cardiac work, and myocardial oxygen requirement. The use of ketamine should probably be avoided in patients with severe hypertension, coronary disease, or congenital heart diseases that compromise cardiac function and reserve. However, this relative contraindication represents an insignificant portion of the pediatric dental population. Ketamine maintains an intact protective airway reflex, resulting in an incidence of aspiration that is minimal. Since ketamine causes both bronchodilation and maintenance of upper airway skeletal muscle tone, it is indicated for the asthmatic patient. Ketamine has not been shown to significantly alter hepatic or renal function, and since it does not stimulate the release of histamine, it rarely causes allergic reactions.

Advantages of using ketamine as an oral sedative agent for pediatric dental patients include a relatively fast onset (25 minutes) in part due to its extreme lipid solubility and rapid transfer across the blood-brain barrier, analgesia and sedative effects, minimal respiratory depression, a wide safety margin, and adequate operating time (36.4 minutes). The literature reports oral doses of ketamine ranging from 4-10 mgAg. However, the 10-mgAg oral dose in this study was selected after patients in trial runs at 8 mgAg did not reach the desired level of sedation. Promethazine is a potent antihistamine that is useful in dentistry as a sedative, an antiemetic, and an antisialagogue. Promethazine is widely used with meperidine as an adjunct to increase the sedative effect and to minimize the nausea frequently encountered with meperidine in pediatric dental patients. The antisialagogue effect of promethazine may also prove beneficial in avoiding the potential cough and laryngospasm associated with the excessive salivation sometimes seen with ketamine. The addition of pro methazine may also enhance the working time needed for longer operative procedures. Since nausea and vomiting have been implicated with ketamine use alone, this study will evaluate the frequency of vomiting using a ketamine-promethazine combination compared with ketamine alone.

The purposes of this study were to compare the sedative effectiveness of orally administered ketamine to a ketamine-promethazine combination to evaluate the incidence of vomiting and to determine if ketamine-promethazine is an effective combination in managing uncooperative pediatric dental patients. avodart 0.5 mg

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