General information
Ketamine is marketed under the trade name Ketanest-S® as an almost ideal emergency medicine. It provides exceptional pain relief by means of a so-called dissociative anesthesia, which puts the patient into a trance state while maintaining breathing and vital reflexes. For these reasons, it is often used to rescue patients who are difficult to reach, e.g. those who are trapped.
Mode of action
The NMDA receptor complex is not competitively blocked by ketamine, resulting in dissociative anesthesia (i.e., functional separation of the thalamocortical and limbic systems). In addition, marked pain relief, amnesia, cataplesia and superficial anesthesia with increased muscle tone and broncholysis. Beta blockers can be used to treat any circulatory reactions that may occur. Certain opiate receptors, which can cause respiratory depression and addiction when stimulated, are not occupied by ketamine.
Fields of application
Ketamine is used in emergency medicine for the most severe pain and is also successfully used in cases of polytrauma (multiple severe injuries). Ketamine can also be used to ensure respiratory function in patients who cannot be reached because they are trapped, or in acute asthma attacks.
Contraindications
Ketamine should not be used in the treatment of heart disease, high blood pressure, aortic aneurysm, pheochromocytoma, eclampsia, hyperthyroidism, perforating eye injuries, glaucoma (glaucoma, increased intraocular pressure), imminent uterine rupture, umbilical cord prolapse or psychiatric disorders.
Dosage
As an injectable narcotic with a duration of action of approx. 10 minutes, ketamine is used at a dosage of 1-2 mg/kg and starts working after approx. 30 seconds. If an analgosedation is to be performed, up to 0.25 mg/kg is administered and for anaesthetic induction up to 1 mg/kg, and for asthmaticus status up to 1.5 mg/kg. Intramuscular injections have also proven to be effective, even if the onset of action is delayed here to 5 minutes, but the effect lasts up to 30 minutes.
Side effects of ketamine
Both brain and heart need increased oxygen when taking ketamine. This can lead to an increase in intracranial pressure and heart rate and blood pressure rise regularly. These bodily reactions to ketamine can be beneficial and desirable in hypovolemic shock (i.e. after a large blood loss).
If there is an overdose of ketamine, myocardial depression and a drop in blood pressure, as well as an increase in lung resistance are possible. The patient experiences the unpleasant dreams associated with ketamine negatively during anesthesia, which can be intensified by acoustic stimuli during the induction phase of anesthesia. In children and elderly people these unpleasant dreams have been observed less or not at all.
Because of the psychologically very disturbing dreams, additional medication with midazolam or diazepam is strongly recommended. The side effect of increased salivary flow (hypersalivation), which is mainly observed in children, can be corrected by the administration of atropine. Aggressive individuals may experience increased psychomotor agitation with ketamine administration and alcoholics may need higher doses due to faster ketamine release.
Motor restlessness and aggression are also possible. Strict contraindications of ketamine:Absolute contraindications to ketamine are hypertension (high blood pressure), coronary heart disease (CHD), myocardial infarction (heart attack), and penetrating eye injury (tear, etc.).
