Comparison of single-shot echo-planar and line scan protocols for diffusion tensor imaging

RATIONALE AND OBJECTIVES: Both single-shot diffusion-weighted echo-planar imaging (EPI) and line scan diffusion imaging (LSDI) can be used to obtain magnetic resonance diffusion tensor data and to calculate directionally invariant diffusion anisotropy indices, ie, indirect measures of the organization and coherence of white matter fibers in the brain. To date, there has been no comparison of EPI and LSDI. Because EPI is the most commonly used technique for acquiring diffusion tensor data, it is important to understand the limitations and advantages of LSDI relative to EPI. MATERIALS AND METHODS: Five healthy volunteers underwent EPI and LSDI diffusion on a 1.5 Tesla magnet (General Electric Medical Systems, Milwaukee, WI). Four-mm thick coronal sections, covering the entire brain, were obtained. In addition, one subject was tested with both sequences over four sessions. For each image voxel, eigenvectors and eigenvalues of the diffusion tensor were calculated, and fractional anisotropy (FA) was derived. Several regions of interest were delineated, and for each, mean FA and estimated mean standard deviation were calculated and compared. RESULTS: Results showed no significant differences between EPI and LSDI for mean FA for the five subjects. When intersession reproducibility for one subject was evaluated, there was a significant difference between EPI and LSDI in FA for the corpus callosum and the right uncinate fasciculus. Moreover, errors associated with each FA measure were larger for EPI than for LSDI. CONCLUSION: Results indicate that both EPI- and LSDI-derived FA measures are sufficiently robust. However, when higher accuracy is needed, LSDI provides smaller error and smaller inter-subject and inter-session variability than EPI.     

Reversal of an unintentional spinal anesthetic by cerebrospinal lavage

In this case report, we describe the use of cerebrospinal fluid lavage as a successful treatment of an inadvertent intrathecally placed epidural catheter in a 14-yr-old girl who underwent a combination of epidural anesthesia and general anesthesia for orthopedic surgery. In this case, a large amount of local anesthetic was injected (the total possible intrathecal injection was 200 mg of lidocaine and 61 mg of bupivacaine), resulting in apnea and fixed dilated pupils in the patient at the end of surgery. Twenty milliliters of cerebrospinal fluid was replaced with 10 mL of normal saline and 10 mL of lactated Ringer's solution from the "epidural" catheter. Spontaneous respiration returned 5 min later, and the patient was tracheally extubated after 30 min. No signs of neurological deficit or postdural puncture headache were noted after surgery. IMPLICATIONS: Cerebrospinal lavage may be a helpful adjunct to the conventional supportive management of patients in the event of an inadvertent total spinal.     

0.5% versus 1.0% 2-chloroprocaine for intravenous regional anesthesia: a prospective, randomized, double-blind trial

In this randomized prospective double-blind study we tested the hypothesis that compared with 40 mL chloroprocaine 0.5%, 40 mL chloroprocaine 1% results in an earlier onset to analgesia duration and improves distal tourniquet tolerance in 150 patients undergoing forearm surgery under IV regional anesthesia using a double-cuff technique, switching from the proximal to the distal cuff was performed if pain scores increased above 4 of 10. Switching to the distal cuff resulted in pain scores below 4 in 69% of patients in the 0.5% group and in 88% of patients in the 1% group (P = 0.047). In addition, both groups differed in the sustained effect on distal tourniquet pain (P = 0.020). Time between injection and onset to analgesia duration was 13 +/- 1 min in the 0.5% group and 11 +/- 1 min in the 1% group (P = 0.0006). On release of the tourniquet, signs of systemic local anesthetic toxicity occurred in 6 patients of the 0.5% group and 28 of the 1% group (P < 0.0001). We conclude that chloroprocaine 1% resulted in an earlier onset of analgesia and improved distal tourniquet tolerance. However, these beneficial effects must be weighed against a fourfold increase in side effects. IMPLICATIONS: Compared to a standard dose of 40 mL 0.5% chloroprocaine, 40 mL 1% chloroprocaine resulted in an earlier onset of analgesia duration and improved distal tourniquet tolerance during IV regional anesthesia. These beneficial effects must be weighed against a fourfold increase in signs of systemic local anesthetic toxicity.     

Measuring depth of sedation with auditory evoked potentials during controlled infusion of propofol and remifentanil in healthy volunteers

Avoiding excessively deep levels of sedation is a major problem in intensive care patients. We studied whether clinically relevant levels of sedation can be objectively assessed using long latency auditory evoked potentials. We measured the auditory evoked potentials at 100 ms after the stimulus (N100) in 10 healthy volunteers during stepwise increasing, clinically relevant levels of sedation (Ramsay score [RS] 2-4). The volunteers were studied on three separate occasions and received an infusion of either propofol or a combination of propofol and remifentanil. Effects of remifentanil infusion alone were tested during target controlled infusion (target plasma concentrations: 1, 2, and 3 ng/mL). Remifentanil did not affect evoked potential amplitudes and latencies. During both propofol-induced and propofol/remifentanil-induced sedation, the N100 amplitude decreased similarly without an effect on the latencies as the level of sedation increased from Ramsay score 2 to Ramsay score 4 (P < 0.01). At the same clinical level of sedation, propofol plasma concentrations were larger when sedation was achieved by propofol alone (propofol versus propofol/remifentanil, RS 3: 2.12 mug/mL +/- 0.51 versus 1.32 +/- 0.43, P < 0.01; RS 4: 3.37 +/- 0.47 versus 1.86 +/- 0.34, P < 0.01). Our results suggest that long latency auditory evoked potentials provide an objective electrophysiological analog to the clinical assessment of sedation independent of the sedation regime used.     

Small-dose intrathecal clonidine and isobaric bupivacaine for orthopedic surgery: a dose-response study

We examined the dose-response relationship of intrathecal clonidine at small doses (相似文献   

Chondrosarcoma of the hand: is a wide surgical resection necessary?

Chondrosarcomas of the hand are rare and generally treated with surgical resection. Thirteen patients with Grade 1 chondrosarcoma of the small bones of the hand were followed up for a mean of 99.8 months (range, 26-293 months). In eight patients (Group 1) curettage and reconstruction with cancellous bone was done and in five patients (Group 2) a wide resection was done. No patient experienced relapse in Group 2. In Group 1 one patient had a local relapse 18 months after intralesional resection. Using the Musculoskeletal Tumor Society score for evaluation, the clinical results showed an average of 98% and 95% of the normal function in Groups 1 and 2, respectively. None of the patients had evidence of systemic spread of the disease. With a relapse rate of 12.5% and no distant metastases after curettage, intralesional resection is the preferred method of treatment in Grade 1 chondrosarcoma of the hand, allowing the patient to avoid amputation and major loss of function.