Magnetic resonance spectroscopy detects biochemical changes in the brain associated with chronic low back pain: a preliminary report.

Magnetic resonance (MR) spectroscopy is a noninvasive technique that can be used to detect and measure the concentration of metabolites and neurotransmitters in the brain and other organs. We used in vivo (1)H MR spectroscopy in subjects with low back pain compared with control subjects to detect alterations in biochemistry in three brain regions associated with pain processing. A pattern recognition approach was used to determine whether it was possible to discriminate accurately subjects with low back pain from control subjects based on MR spectroscopy. MR spectra were obtained from the prefrontal cortex, anterior cingulate cortex, and thalamus of 32 subjects with low back pain and 33 control subjects without pain. Spectra were analyzed and compared between groups using a pattern recognition method (Statistical Classification Strategy). Using this approach, it was possible to discriminate between subjects with low back pain and control subjects with accuracies of 100%, 99%, and 97% using spectra obtained from the anterior cingulate cortex, thalamus, and prefrontal cortex, respectively. These results demonstrate that MR spectroscopy, in combination with an appropriate pattern recognition approach, is able to detect brain biochemical changes associated with chronic pain with a high degree of accuracy.

Intra-subject variability in post-operative patient-controlled analgesia (PCA): is the patient equally satisfied with morphine, pethidine and fentanyl?

Our previous study suggested that when compared between patients, morphine, pethidine and fentanyl were equally satisfactory for use in patient-controlled analgesia (PCA), although quantitative differences in their side-effect profiles were detectable. The present study evaluated whether individual patients could detect differences or express preferences for individual opioids when treated by PCA with all three in random sequence finishing with the first administered opioid. The main side effects were pruritus, nausea and vomiting. There were few differences in patients' responses to morphine, pethidine and fentanyl, or of satisfaction with these drugs, across patients, but individual patients' responses to the opioids could be highly variable. Some patients were able to tolerate all three opioids investigated, some were intolerant to all and some patients appeared to be sensitive to one or two of the opioids but show a preference for the remainder. These findings support the clinical practice of changing from one opioid to another (with good effect) in post-operative patients experiencing intolerable side-effects. The reasons for a patient responding differently to different opioids and even to the same opioid on separate occasions are not clear and appear inexplicable on the grounds of currently postulated receptor affinities or of physicochemical properties of the opioids studied. A plethora of factors will influence how an individual patient will respond to surgery and how he/she will recover. The physiological response to opioids is one variable which appears to be influenced by this complex set of factors and in turn will affect them. The findings of this study, like that of its predecessor, suggest that morphine, pethidine and fentanyl can be used successfully in PCA and that for some patients who are responding poorly, changing the opioid may be beneficial.

A comparison of morphine, pethidine and fentanyl in the postsurgical patient-controlled analgesia environment.

This study was designed to evaluate whether there is any scientific basis for clinicians' preferences for selecting opioids for use in patient-controlled analgesia (PCA) and to determine whether there are any patients' preferences for being treated with any of these opioids. Results were obtained for 55 postoperative patients recruited to investigate putatively equivalent doses of 3 commonly used opioids--morphine, pethidine and fentanyl--when self-administered postoperatively. No significant differences in the incidence of side effects between groups were found with the exception of more pruritus reported in the group given morphine. Patients who experienced vomiting or pruritus reported a greater intensity of these side effects if receiving morphine and fentanyl than if receiving pethidine. The majority of patients reported being very satisfied with their postoperative pain management and with PCA, with no differences in satisfaction between the 3 opioid-treated groups. A senior consultant anaesthetist, when asked to make a judgement, was not able to identify which agent each patient was receiving with a better than chance accuracy. These findings suggest that while there may be subtle differences in patient response to these 3 commonly used opioids, none was obviously superior when used for postoperative PCA.

Phantom limb sensation.

1. Phantom limb pain and sensations are common in amputees. The present paper defines phantom limb pain, stump pain and phantom limb sensation and then gives an overview of the incidence and characteristics of the phenomena. 2. Theories of phantoms are presented, including peripheral, central and supraspinal theories, with particular attention given to Melzack's neuromatrix. 3. Evidence of cortical reorganization following amputation is given and the extent to which cortical reorganization contributes to phantom limb pain is discussed.