[Case report: Treatment of burning pain and Post traumatic refractory allodynia in foot digits, with low dose of ketamine]

Frequent simulation and irritation of NMDA receptors by glutamate mediators can lead to burning pain, allodynia and hyperalgesia, even after stopping the irritant factor. Opioid-induced hyperalgesia and peripheral nerve injuries in lower extremities orthopedic surgeries can also make the same symptoms, which sometimes make it difficult to diagnose it from causalgia [type II complex regional pain syndrome]. Post-traumatic neuralgia is not so common, often does not respond well to usual medications and prolongs the patient's stay in hospital. Noting the anatomical and physiological aspects of pain transmission pathways and also role of pain transmission inhibitors via NMDA receptors in pain management, opens us a new window to the role of medicines such as ketamine in prevention and treatment of neuropathic or chronic postoperative pains. We report a case involving refractory neuropathic pain which is eventually controlled with low dose of ketamine

[ effects of adding ketamine to morphine in patient-controlled intravenous analgesia after orthopedic surgeries]

A routine method to control post-operative pain is patient-controlled intravenous analgesia [PCIA] using opioids. Regarding complications of opioids, it seems necessary to reduce their dosage and to improve the quality of analgesia using adjuvants. We aimed to assess the effect of adding ketamine to morphine in PCIA pumps for post-operative pain control in orthopedic patients. Sixty patients, being 20-60 years old [ASA class I-II] and undergoing orthopedic surgery in lower extremity, were enrolled They had no history of opioid addiction or epilepsy. Our patients were randomly allocated to three groups 20 mg morphine sulfate, 100 mg ketamine plus 20 mg morphine and 200 mg ketamine plus 10 mg morphine in their PCIA pump. The pain score was evaluated using VAS [0-10] and VRS [0-5]; besides the sedation score and the degree of nausea-vomiting were assessed with Ramsay scale [0-5] and N and V score [1-4], respectively. All these measurements were performed 2, 4, 12, 24, and 48 hours postoperatively. The incidence of adverse drug reactions was not different among the three groups [p>0.05], but pain control was significantly better in the second and third group [ketamine plus morphine] in comparison with the first one [p<0.05]. There was no difference in the quality of pain control between the second and the third groups. Also, the need for additional opioid was significantly reduced in the two latter groups compared with the first one [p<0.05]. Adding ketamine to morphine in PCIA pumps would result in better pain control and less need for additional break-through analgesic