Ketamine: In the past thirty years and in the future
Introduction There are two isomers of ketamine: S(+)ketamine and R(-) ketamine. Effects of this drug are mediated by N-methyl-D-aspartate (NMDA), opioid and muscarinic receptors. Pharmacokinetics Due to its high lipid solubility and low protein binding, ketamine is extensively distributed in the body. Ketamine metabolism is mediated by hepatic microsomal enzymes. Effects on body systems Ketamine causes increased intracranial pressure, bronchodilation and stimulation of cardiovascular system. Clinical use Anesthesia It is used for premedication, sedation, induction and maintenance of general anesthesia. Ketamine is an ideal anesthetic agent for trauma victims, patients with hypovolemic and septic shock, patients with pulmonary diseases. Analgesia Even subanesthetic doses of ketamine have analgesic effects, so ketamine is also recommended for postoperative analgesia. Recent results show that ketamine is not always effective as an analgesic in treatment of chronic pain and that some side effects limit its use in patients with chronic pain. Intensive care Combination of ketamine and midazolam can be very useful and safe for sedation and pain relief in intensive care patients, especially during ventilator management. Ketamine may be the anesthetic of choice for painful procedures in intensive care units. Emergency medicine Ketamine is recommended for critically ill patients with sedative, inotropic and bronchodilatatory effects. New clinical use Future studies will reveal if ketamine can be used for outpatient anesthesia, intravenous regional anesthesia and in treatment of depression. S(+)ketamine is a more effective anesthetic with significantly less psychomotor effects which provides rapid recovery from anesthesia in regard to racemate or R(-)ketamine. Conclusion Increasing interest in use of ketamine has resulted from current knowledge. In the future we expect new clinical uses in treatment of acute and chronic pain, intensive care and emergency medicine.