Regional anesthesia and pain medicine
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Reg Anesth Pain Med · Jul 1999
In vivo diffusion-weighted magnetic resonance microscopy of rat spinal cord: effect of ischemia and intrathecal hyperbaric 5% lidocaine.
Pathophysiologic mechanisms underlying persistent neurologic deficits after continuous spinal anesthesia using hyperbaric 5% lidocaine are still not well understood. It has been suggested that high-dose intrathecal lidocaine induces irreversible conduction block and even ischemia in white matter tracts by breakdown of the blood-nerve barrier. In this study, we use diffusion-weighted magnetic resonance microscopy to characterize the effect of intrathecal hyperbaric 5% lidocaine in rat spinal cord. The parameter measured with DWM, is an "apparent diffusion coefficient," (ADC), which can be used to exclude the presence of ischemia. ⋯ Ischemia reduced the ADC in both spinal cord white and gray matter. Hyperbaric 5% lidocaine did not affect the spinal cord ADC during the first 1.5 hours. We suggest that 5% hyperbaric lidocaine does not induce irreversible neurologic deficits by causing spinal cord ischemia.
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Important issues regarding the spread of solutions in the epidural space and the anatomy of the site of action of spinal and epidural injections are unresolved. However, the detailed anatomy of the spinal canal has been incompletely determined. We therefore examined the microscopic anatomy of the spinal canal soft tissues, including relationships to the canal walls. ⋯ These features of the fat explain its semifluid consistency. Lack of substantial attachments to the dura facilitate movement of the dura relative to the canal wall and allow distribution of injected solution. Fibrous barriers are an unlikely explanation for asymmetric epidural anesthesia, but the midline fat could impede solution spread. Details of nerve-root structure and their envelope of pia-arachnoid membrane may be relevant to anesthetic action.
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Reg Anesth Pain Med · May 1999
Randomized Controlled Trial Comparative Study Clinical TrialPreoperative intra-articular morphine and bupivacaine for pain control after outpatient arthroscopic anterior cruciate ligament reconstruction.
The purpose of this study was to determine whether intra-articular injection of bupivacaine, morphine, or a combination prior to surgery provided pain control after arthroscopic anterior cruciate ligament (ACL) reconstruction. ⋯ Presurgical injection of a solution of 0.25 % bupivacaine, morphine, and epinephrine provided pain control and decreased opioid use in the PACU. Increasing the morphine dose did not improve the clinical result.
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Reg Anesth Pain Med · May 1999
ReviewIntrathecal lipophilic opioids as adjuncts to surgical spinal anesthesia.
Lipophilic opioids, especially fentanyl and sufentanil, are increasingly being administered intrathecally as adjuncts to spinal anesthesia. This review analyzes the efficacy of these opioids for subarachnoid anesthesia. ⋯ The anesthesia-enhancing properties and side-effect profile of lipophilic opioids administered intrathecally suggest significant roles for these agents as adjuncts to spinal anesthesia for obstetric and outpatient procedures.
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Reg Anesth Pain Med · May 1999
Randomized Controlled Trial Comparative Study Clinical TrialPhrenic nerve block caused by interscalene brachial plexus block: effects of digital pressure and a low volume of local anesthetic.
Interscalene brachial plexus block (ISB) is associated with phrenic block and diaphragmatic paralysis when high volumes (40-50 mL) of local anesthetic are injected. The goal of our study was to test if a low volume of local anesthetic administered while maintaining proximal digital pressure might more selectively block the brachial plexus and decrease the frequency of phrenic nerve block. ⋯ Decreasing the volume of local anesthetic and applying proximal digital pressure to the site of injection is not effective in reducing the cervical block spread and the frequency or intensity of diaphragmatic paralysis during interscalene ISB.