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At least 739 records · Page 41Linked to original sources
PubMed1999

Supraspinal and spinal delta(2) opioid receptor-mediated antinociceptive synergy is mediated by spinal alpha(2) adrenoceptors.

Concurrent administration of low doses of [D-Ala(2), Glu(4)]deltorphin (DELT) in the spinal cord and rostral ventromedial medulla of the rat produces a synergistic antinociception in the tail-flick test. It was postulated that the synergistic antinociception results from an interaction of the intrathecally-administered DELT with norepinephrine released in the spinal cord as a result of the microinjection of DELT in the rostral ventromedial medulla. Three approaches were taken to test this hypothesis. The first experiment determined that microinjection of DELT in the rostral ventromedial medulla produced an increase in tail-flick latency that was partially attenuated by intrathecal administration of the alpha(2)-adrenoceptor antagonist yohimbine. These data indicated that microinjection of DELT in the medulla causes a release of norepinephrine in the spinal cord. The second experiment determined that intrathecal co-administration of DELT with the alpha(2)-adrenoceptor agonist dexmedetomidine in a 2:1 fixed dose ratio produced a synergistic antinociception in the tail-flick test. The final experiment determined that the antinociception produced by concurrent medullary and intrathecal administration of DELT was completely antagonized by intrathecal administration of yohimbine. Taken together, these findings support the hypothesis that the synergistic antinociception produced by concurrent activation of medullary and spinal delta(2) opioid receptors is mediated, in part, by endogenous norepinephrine release in the spinal cord. The norepinephrine, acting at alpha(2)-adrenoceptors, interacts in a synergistic manner with intrathecally administered DELT, acting at spinal delta(2) opioid receptors, to produce antinociception.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Comparative toxicity of glucose and lidocaine administered intrathecally in the rat.

BACKGROUND AND OBJECTIVES: Glucose is a common component of anesthetic solutions used for spinal anesthesia. However, its possible contribution to recent injuries occurring with spinal anesthesia has not been adequately addressed. Accordingly, the present studies compare the functional and morphologic effects of intrathecally administered glucose with those of lidocaine. METHODS: Twenty rats, implanted with intrathecal catheters, were divided into three groups to receive a 1-hour infusion of 5% lidocaine (n = 6), 10% glucose (n = 7), or normal saline (n = 7). Four days after infusion, animals were evaluated for persistent sensory impairment using the tail-flick test. Three days later, the animals were sacrificed, and the spinal cord and nerve roots were examined by a neuropathologist blinded to the solution received and the results of sensory testing. RESULTS: Lidocaine-treated animals exhibited persistent sensory impairment, whereas glucose- and saline-treated animals did not. Neuropathologic evaluation revealed moderate to severe nerve root injury in lidocaine-treated animals. Histologic changes in glucose- and saline-treated animals were minimal, similar, and restricted to the area adjacent to the catheter. Morphologic damage associated with lidocaine preferentially affected the nerve roots, with relative sparing of the spinal cord and dorsal root ganglia. CONCLUSIONS: These results suggest that, at clinically relevant concentrations, glucose does not induce neurologic injury, providing indirect evidence that recent clinical injuries occurring after spinal anesthesia resulted from a neurotoxic effect of the local anesthetic. Additionally, the present studies suggest that deficits resulting from neurotoxicity of intrathecally administered anesthetic result from injury to the axon.

Anesthesia, Spinal↗
PubMedDate not supplied

Effects of levobupivacaine, bupivacaine, and ropivacaine on tail-flick response and motor function in rats following epidural or intrathecal administration.

BACKGROUND AND OBJECTIVES: Commercially available bupivacaine is a racemic mixture of S (-)- and R(+)-enantiomers. Although the S(-)-enantiomers levobupivacaine and ropivacaine are less toxic to the cardiovascular and central nervous systems than bupivacaine, their relative efficacy has not been determined. This study directly compares the dose response of levobupivacaine, ropivacaine, and bupivacaine following epidural and intrathecal administration in the rat. METHODS: The time course of change in tail-flick latency and qualitative motor function was studied in rats following epidural or intrathecal administration of 0.25-0.75% levobupivacaine, ropivacaine, or bupivacaine in blinded, randomized fashion. RESULTS: Levobupivacaine and bupivacaine produced comparable and significantly enduring antinociceptive effects compared with ropivacaine at all test concentrations following both epidural and intrathecal administrations. Duration of motor block at lower local anesthetic concentrations (epidurally and intrathecally) was comparable with levobupivacaine and ropivacaine but significantly shorter than with bupivacaine. Epidural 0.75% levobupivacaine and bupivacaine showed more enduring motor block than ropivacaine. CONCLUSIONS: Levobupivacaine, given epidurally or intrathecally, produces longer lasting antinociceptive action than ropivacaine at equivalent concentrations and similar motor blocking effect at lower concentrations in both epidural and intrathecal administrations. Levobupivacaine-induced prolongation of the tail-flick latency is comparable to that of bupivacaine, as is motor blocking effect at higher concentrations. The possibility of significant differential block with levobupivacaine compared with bupivacaine warrants further study.

Amides↗
PubMed2003

Neurotoxicity of intrathecal local anaesthetics and transient neurological symptoms.

Local anaesthetics have been placed in the intrathecal space for approximately 100 years. Currently used intrathecal local anaesthetics appear to be relatively benign on the basis of the low incidence of permanent neurological deficits. In large retrospective surveys of 4000-10 000 patients, the incidence of persistent neurological sequelae after subarachnoid anaesthesia varies between 0.01 and 0.7%. Since its introduction in 1948, hyperbaric 5% lidocaine has been used for millions of spinal anaesthetics. The predictable onset and limited duration of action have made lidocaine one of the most popular spinal anaesthetics currently available. Concern about the use of spinal lidocaine began in 1991 with published reports of cauda equina syndrome after continuous spinal anaesthesia. In 1993, Schneider published a case report of four patients undergoing spinal anaesthesia who postoperatively experienced aching and pain in the buttocks and lower extremities. This chapter reviews the neurotoxicity of spinal local anaesthetics, as well as the incidence, possible aetiology, and treatment of transient neurological symptoms after lidocaine spinal anaesthesia.

Anesthesia, Spinal↗
PubMedDate not supplied

Single needle approach for multiple medial branch blocks: a new technique.

BACKGROUND AND OBJECTIVES: Medial branch blocks are an important tool for the diagnosis of facet joint arthropathy. The most commonly used technique involves multiple needle placements, one for each nerve blocked. This multiple needle technique may require a large amount of local anesthetic for anesthetizing the skin, thereby increasing the rate of false-positive blocks. TECHNIQUE: Diagnostic lumbar medial branch blocks are usually performed using multiple needles, one for each branch. The authors describe a different technique using a single needle for all levels. Initially, the needle is directed toward the medial branch located at the level of the affected facet joint in the antero-posterior view. After anesthetizing this nerve with local anesthetic, the same needle is withdrawn to the skin with the tip still in the subcutaneous tissue and repositioned to block the medial branch above, and thereafter below, while continuing to use only the antero-posterior view, thereby using only one entry site. CONCLUSIONS: When performed correctly, the single needle technique provides accuracy similar to the more conventional multiple needle approach during the performance of diagnostic facet joint nerve blocks. Because only one skin entry point is needed, however, this technique may afford several advantages over the multiple needle approach. These may include less patient discomfort, less time required and less radiation exposure since only one C-arm position is used, a smaller volume of local anesthetic, and possibly a lower incidence of false-positive blocks.

Anesthesia, Spinal↗
PubMedDate not supplied

Delayed remyelination in rat spinal cord following ethidium bromide injection.

Areas of demyelination were produced by injecting ethidium bromide into the white matter of the lumbar spinal cord of rats. There was variation in the nature of the process of demyelination and a difference in the speed with which Schwann cells remyelinated the demyelinated axons. In some lesions, or areas within lesions, myelin debris was rapidly processed by macrophages and axons were rapidly remyelinated by Schwann cells, while in other lesions of similar duration, or in areas within the same lesion, the myelin was transformed into lattices of membranous profiles which persisted around axons for long periods of time. In the lesions containing such myelin derived membranes, there were few macrophages and remyelination by Schwann cells was delayed compared to that seen in the more rapidly resolving lesions. It was concluded that the slow resolution of some lesions resulted from the delay between intoxication and cell disintegration (7-10 days) which meant that the cell responses to demyelination took place in a glial free area which could not support cell movement needed for removal of myelin debris and remyelination. This study indicates that the tempo and results of demyelination can be altered by the cellular events which accompany degeneration of oligodendrocytes.

Animals↗
PubMed2005

Intrathecal clonidine does not reduce post-spinal shivering.

BACKGROUND: After general or epidural anesthesia, clonidine is known to be effective in suppressing established shivering. The aim of this study was to assess the preventive effect of intrathecal clonidine on post-spinal shivering compared with intravenous (i.v.) clonidine. METHODS: One hundred and fifty patients scheduled for orthopedic surgery were randomly allocated into three groups to receive either 1 microg/kg clonidine i.v. (IV group) or the same volume of isotonic saline (control and IT groups) at 5 min before spinal anesthesia. Spinal anesthesia was performed with 12-15 mg hyperbaric bupivacaine 0.5% plus either 1 ml of saline (control and IV groups) or 150 microg clonidine (IT group). Shivering was evaluated for a period of 90 min and graded as none, mild, moderate, and severe. RESULTS: Twenty patients (40%) in the control group and 17 patients (34%) in the IT group showed shivering compared with four (8%) in the IV group. Patients with moderate-to-severe shivering were only seen in the control and IT group, and the maximal intensity of shivering was not different between the two groups. Patients in the IV group were significantly more sedated than the other groups. CONCLUSIONS: The intrathecal administration of clonidine 150 microg fails to prevent post-spinal shivering; by contrast, we have confirmed that i.v. clonidine 1 microg/kg is an effective method to prevent shivering in patients undergoing spinal anesthesia for orthopedic surgery.

Adolescent↗
PubMed1974

Antagonism of the spinal action of diazepam by semicarbazide.

In spinal unanaesthetized cats, pretreatment with semicarbazide (200 mg/kg) 2-4.5 h prior to the administration of diazepam (1-4 mg/kg) completely blocked the enhancement of the segmental dorsal root reflex by the latter compound. Pyridoxine hydrochloride (200 mg/kg), given 3.5 h after semicarbazide, restored the spinal effect of diazepam administered 1 h later. The possibility of a link between diazepam and spinal gamma-aminobutyric acid is suggested and discussed.

Aminobutyrates↗
PubMed1992

Supersensitivity to the antinociceptive effect of a 5-HT1 receptor agonist after lesion of raphe-spinal serotonergic neurones.

The actions of the 5-hydroxytryptamine type-1B (5-HT1) receptor agonist 1(m-chlorophenyl)piperazine (mCPP) on response latencies in the tail-flick test and tail skin temperature were examined in mice after pretreatment with the 5-HT neurotoxin, 5,6-dihydroxytryptamine (5,6-DHT). All the compounds were given intrathecally. The level of 5-HT in spinal cord was reduced by 79% 4 days after intrathecal injection of 5,6-DHT (10 micrograms). There was a significant relationship between the tail-flick latency and tail skin temperature, and the reduced baseline tail-flick latencies induced by 5,6-DHT were non-significant after the change in skin temperature was taken into account. Intrathecal mCPP (5 micrograms) significantly increased the tail-flick latency and significantly reduced the tail skin temperature in 5,6-DHT pretreated animals when compared to control animals. These differences in tail-flick latencies could not be explained by alterations in skin temperature. The results provide evidence that neurotoxic lesion of descending 5-HT pathways induces supersensitivity to the antinociceptive effect of 5-HT1 receptor stimulation.

5,6-Dihydroxytryptamine↗