The injection of intrathecal normal saline reduces the severity of postdural puncture headache.

BACKGROUND AND OBJECTIVES: We investigated whether the injection of 10 mL of normal saline into the subarachnoid space following accidental dural puncture reduced the incidence of postdural puncture headache (PDPH) and the need for epidural blood patch (EBP). METHODS: Twenty-eight patients who experienced accidental dural puncture with an epidural needle had 10 mL of normal saline injected into the subarachnoid space. In 22 patients, the injection was performed immediately through the epidural needle. In 6 patients who had intrathecal catheters placed through the epidural needle, the saline was injected through the catheter before removal. All other patients who experienced wet taps during the same period that the study was in progress but did not receive the saline injection served as a control group, 26 in number. Patients with severe or persistent PDPHs were treated with EBP. RESULTS: Of those patients who received intrathecal normal saline immediately through the epidural needle, 32% developed a headache compared with 62% of controls. Of these, 1 patient who received saline required EBP compared with nine in the control group (P =.004). Of those patients who had intrathecal catheters placed, there were no headaches in the saline group of 6 compared with 3 in the control group of 5, 1 of whom was treated with EBP (P >.05). CONCLUSIONS: The immediate injection of 10 mL intrathecal normal saline after a wet tap significantly reduced the incidence of PDPH and the need for EBP. When an intrathecal catheter had been placed following a wet tap, injection of 10 mL of normal saline before its removal effectively prevented PDPH.

Neural blockade for neuropathic pain.

OBJECTIVE: This study reviews the available literature regarding the use of nerve blocks for the management of peripheral neuropathy. DESIGN: A MEDLINE literature review was carried out, examining the existing literature about the use of nerve blocks for the treatment of mononeuropathies and radiculopathy. INTERVENTIONS: The study encompassed the use of local anesthetic peripheral and sympathetic nerve blocks, perineural steroid injections, and neurolytic blocks. RESULTS: Local anesthetic peripheral and sympathetic blocks provide useful diagnostic information but tend to afford only temporary therapeutic benefits in patients with peripheral neuropathy. Perineural steroids provide lasting relief for some patients with radiculopathy and peripheral neuropathy, but in most studies, it is a minority of patients who experience long-term relief. Peripheral neurolytic blocks are helpful for some patients with peripheral mononeuropathy, particularly in the setting of cancer pain. Although there are the risks of exacerbating pain and serious complications, certain patients experience long-term relief. CONCLUSIONS: Most discussions on the management of peripheral neuropathy do not include the use of nerve blocks. Nevertheless, the nerve block procedures discussed here can play an important role in the management of these conditions.

Cranial nerve palsy and intracranial subdural hematoma following implantation of intrathecal drug delivery device.

BACKGROUND AND OBJECTIVES: Complications related to cerebrospinal fluid (CSF) leak and low CSF pressure can occur following placement of an intrathecal drug delivery device. METHODS: A 58-year-old man with chronic, intractable lower back pain underwent implantation of an intrathecal drug delivery device. On the fourth postoperative day, he developed a postural headache and diplopia with findings compatible with left sixth cranial nerve palsy. The headache subsequently became constant and nonpostural. Cranial magnetic resonance imaging was obtained that showed the presence of a posterior subdural intracranial hematoma. Conservative treatment for postdural puncture headache did not improve the symptomatology. Therefore, an epidural blood patch was performed that produced rapid improvement and eventual resolution of symptoms. CONCLUSIONS: Intrathecal catheter implantation can result in CSF loss that might not resolve promptly with conservative therapy. In this case, epidural blood patch proved to be a safe and effective form of treatment.

Assessment of the potency and intrinsic activity of systemic versus intrathecal opioids in rats.

BACKGROUND: One measure of an opioid's efficacy is its ability to retain its analgesic effect as the intensity of a noxious stimulus is increased. A few studies have assessed the ability of either spinal or systemic opioids to produce analgesia using low- and high-intensity stimulation. There are little data available to show whether there are differences in efficacy between systemic and intrathecal opioid administration. The purpose of this study was to assess the relative efficacy of several clinically useful opioids systemically and spinally and to determine whether intrathecal administration resulted in greater efficacy than systemic administration. METHODS: Groups of rats were administered multiple doses of meperidine, morphine, hydromorphone, fentanyl, sufentanil, or buprenorphine either subcutaneously or intrathecally via implanted catheters. Noxious radiant heat was applied sequentially to each hindpaw, one at low intensity (adjusted to a mean withdrawal latency of 10 s) and one at high intensity (adjusted to a mean withdrawal latency of 5 s). Paw withdrawal latencies were recorded; dose-response curves for each intensity and each route of administration were graphically recorded, and ED50s were calculated. Ratios of high-to low-stimulus intensity ED50s were calculated for both routes of administration for each drug, and the ratios of subcutaneous-to-intrathecal ED50s for low-intensity stimulation were calculated to assess the relative systemic versus spinal potencies for each drug. RESULTS: The ratios of the high-to-low intensity ED50s were meperidine, 11.8, morphine, 6.1, hydromorphone, 2.6, fentanyl, 2.3, sufentanil, 1.8, and buprenorphine, 24.0. For intrathecal administration, there was uniformity of the high- to low-intensity ED50 ratios for the agonist drugs (meperidine, 2.1; morphine, 2.1; hydromorphone, 1.9; fentanyl, 1.8; sufentanil, 1.6). For morphine and hydromorphone, the systemic ED50 doses were several hundred times the intrathecal ED50s whereas the systemic-to-spinal ED50 ratios for the other drugs were 20 or less. CONCLUSIONS: As intensity of noxious stimulation is increased, the more potent opioid agonists, administered systemically, produce antinociception with lesser increases in dose compared with lower potency drugs such as meperidine or morphine. When given spinally all opioid agonists tested, including morphine and meperidine, demonstrated good efficacy, as measured by their ability to provide antinociception for high versus low intensity stimulation.

Neural blockade for diagnosis and prognosis. A review.

On the basis of the published material reviewed above, we conclude that there are many limitations that weaken the theoretic basis for neural blockade as a diagnostic or prognostic tool. In addition, these procedures in general lack thorough documentation of clinical usefulness. Reasonable employment of diagnostic neural blockade, therefore, requires not only care in technique and confirmation of effects, but also caution in interpretation and application of the results. This critical evaluation needs to be tempered, however, by two further observations. Experienced and observant clinicians have found these procedures may, on certain occasions, provide information that is helpful in guiding subsequent therapy, so we should not be in haste to dismiss the accumulated judgment of practitioners. Finally, the confusion and complexity that typifies diagnosis in chronic pain may justify the selective use of diagnostic blocks that make anatomic and physiologic sense, even if their validity is incompletely proved.

Epidural steroid injections for the treatment of lumbosacral radiculopathy.

OBJECTIVE: While there is an extensive body of literature concerning the use of epidural steroid injections in the treatment of sciatica, most of the literature is descriptive or anecdotal. There are few controlled studies regarding efficacy of this treatment modality. While there are few published reports of serious complications of this therapy, warnings about the hazards of epidural steroid injections occasionally appear in both medical and lay literature. It is the purpose of this review to assess the existing evidence for efficacy of epidural steroid injections for sciatica and to assess the risks of this procedure. DATA SOURCES: Peer reviewed medical literature from 1930 to the present was reviewed in order to survey reports regarding pathophysiology of radiculopathy, mechanism of action of epidural corticosteroids, controlled efficacy studies, reports on series of epidural steroid injections for sciatica, reports of adverse effects of epidural and intrathecal steroid injections, review articles of epidural and intrathecal steroid injections, and studies of the behavioral and histological effects of epidural steroids and their vehicle in animals. STUDY SELECTION: Studies and review articles were selected from Medline search and from the author's files of older literature. DATA SYNTHESIS: RESULTS of this review are qualitative. It was felt that there was insufficient controlled data to analyze efficacy or safety studies in a quantitative fashion. RESULTS: Radiculopathy following disc herniation appears to produce either mechanical or chemical nerve root inflammation. Epidurally injected corticosteroids most likely exert a beneficial effect through anti-inflammatory rather than direct analgesic mechanisms. Most descriptive studies report beneficial effects of epidural steroids in the majority of cases of radiculopathy, but not for other causes of low back pain. Most of the few controlled studies report epidural steroids to be more efficacious than placebo or epidural local anesthetic alone. Most patients who respond favorably continue to show improvement for many months. Several neurologic complications have been reported after intrathecal steroid injections, most following multiple intrathecal injections. Four cases of epidural abscess, one case of bacterial meningitis, and one case of aseptic meningitis have been reported following epidural steroid injections. CONCLUSIONS: The majority of the published literature supports the notion that epidural steroids provide relief of pain from lumbosacral radiculopathy. There is anecdotal evidence that multiple intrathecal steroid injections may be associated with neurological dysfunction, but there is very little evidence that epidural steroids are neurotoxic.

Neural blockade for upper-extremity pain.

Carefully performed and interpreted neural blockade can be a useful adjunct in both the diagnosis and treatment of painful syndromes of the upper extremity. Pain is a very difficult entity to quantify and diagnose specifically because of its subjective nature, vast differences between patients and their response to pain, and largely because of our inexact understanding of its physiology. Best results of block therapy require thorough understanding of these complexities and limitations, and a rational, careful examination of the data it provides.

Peroneal afferent nerve discharges underlying the behavioral response to the formalin test.

BACKGROUND AND OBJECTIVES: Subcutaneous injection of formalin into the hindpaw of the rat results in a biphasic behavioral response consisting of flinching of the injected paw. It is postulated that the second-phase response is related to sensitization of spinal cord neurons rather than to resumption of peripheral nociceptor activity. METHODS: On removal from anesthesia with 3% halothane, 10 rats were given a subcutaneous injection of formalin (5%, 50 microL) into the dorsum of the hindpaw. Behavioral response to the formalin test were observed for the subsequent hour. In five sodium pentobarbital-anesthetized rats, peroneal afferent nerve activity was recorded for 1 hour following similar subcutaneous injection of formalin. RESULTS: During standard formalin testing in unanesthetized rats, flinching peaked between 1 and 2 minutes following injection (phase 1 response), ceased between 5 and 10 minutes, and recommenced after 15 minutes with a second peak at 45 minutes (phase 2). In sodium pentobarbital-anesthetized rats, peroneal afferent nerve activity increased transiently during the time course of the phase 1 behavioral response but showed no subsequent increase in activity during the ensuing 55 minutes. CONCLUSIONS: The results are consistent with the hypothesis that the initial behavioral response to formalin injection is mediated by high peripheral nerve activity, while the second phase is mediated by sensitization of dorsal horn neurons in conjunction with low persistent levels of afferent activity.