A 32-year-old ex-heroin addict with hepatitis C requires an urgent laparotomy for Rx of a perforated duodenal ulcer. The patient is undergoing treatment with naltrexone. The results of pre-operative coagulation studies include an INR for the prothrombin time of 1.8 and a platelet count of 85,000/cubic mm. Given this scenario, which of the following post-operative analgesic techniques would be most appropriate?

Ketamine patient-controlled analgesia. The use of opiates in patients receiving naltrexone is likely to be ineffective and is probably also inappropriate. An epidural technique is contra-indicated given the presence of a coagulopathy. Given the options listed here, a Ketamine based analgesic technique would seem most appropriate (not withstanding the fact that some effects of Ketamine are mediated opiate mu and delta receptors).