[Spinal cord toxicity of lysine acetylsalicylate and ketamine hydrochloride administered intrathecally in the rat]

Efficacy and adverse effects of ketamine as an additive for paediatric caudal anaesthesia: a quantitative systematic review of randomized controlled trials

BACKGROUND

The aim of this quantitative systematic review was to assess the efficacy and adverse effects of ketamine added to caudal local anaesthetics in comparison with local anaesthetics alone in children undergoing urological, lower abdominal, or lower limb surgery.

METHODS

The systematic search, data extraction, critical appraisal, and pooled data analysis were performed according to the PRISMA statement. All randomized controlled trials (RCTs) were included in this meta-analysis and relative risk (RR), mean difference (MD), and the corresponding 95% confidence intervals (CIs) were calculated using the Revman(®) statistical software for dichotomous and continuous outcomes.

RESULTS

Thirteen RCTs (published between 1991 and 2008) including 584 patients met the inclusion criteria. There was a significant longer time to first analgesic requirements in patients receiving ketamine in addition to a local anaesthetic compared with a local anaesthetic alone (MD: 5.60 h; 95% CI: 5.45-5.76; P<0.00001). There was a lower RR for the need of rescue analgesia in children receiving a caudal regional anaesthesia with ketamine in addition to local anaesthetics (RR: 0.71; 95% CI: 0.44-1.15; P=0.16).

CONCLUSIONS

Caudally administered ketamine, in addition to a local anaesthetic, provides prolonged postoperative analgesia with few adverse effects compared with local anaesthetics alone. There is a clear benefit of caudal ketamine, but the uncertainties about neurotoxicity relating to the dose of ketamine, single vs repeated doses and the child's age, still need to be clarified for use in clinical practice.

Ketamine in chronic pain management: an evidence-based review

Ketamine has diverse effects that may be of relevance to chronic pain including: N-methyl-D-aspartic acid, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, gamma-aminobutyric acid(A) receptors; inhibition of voltage gated Na(+) and K(+) channels and serotonin, dopamine re-uptake. Ketamine has been in clinical practice for over 30 yr; however, there has been little formal research on the effectiveness of ketamine for chronic pain management. In this review we evaluate the available clinical data as a basis for defining the potential use of ketamine for chronic pain. Literature referenced in this review was obtained from a computer search of EMBASE and MEDLINE from 1966 through August, 2002. Search terms included ketamine, ketalar, pain, painful, analgesic, and analgesia. Abstracts were screened for relevance and publications relating to chronic pain use were obtained. Levels of evidence were stratified according to accepted guidelines (level I-IV). For central pain, there is level II and level IV evidence of efficacy for parenteral and oral ketamine. For complex regional pain syndromes, there is only level IV evidence of efficacy of epidural ketamine. For fibromyalgia, there is level II evidence of pain relief, reduced tenderness at trigger points, and increased endurance. For ischemic pain, a level II study reported a potent dose-dependent analgesic effect, but with a narrow therapeutic window. For nonspecific neuropathic pain, level II and level IV studies reported divergent results with questionable long-term effects on pain. For phantom limb pain and postherpetic neuralgia, level II and level II studies provided objective evidence of reduced hyperpathia and pain relief was usually substantial either after parenteral or oral ketamine. Acute on chronic episodes of severe neuropathic pain represented the most frequent use of ketamine as a "third line analgesic," often by IV or subcutaneous infusion (level IV). In conclusion, the evidence for efficacy of ketamine for treatment of chronic pain is moderate to weak. However, in situations where standard analgesic options have failed ketamine is a reasonable "third line" option. Further controlled studies are needed.

The Epidural and Intrathecal Administration of Ketamine

An overview of the spinal administration of ketamine is presented. Ketamine acts as a noncompetitive antagonist of the NMDA receptor Ca(++ channel pore. This effect provides interesting possibilities in pain therapy. However, there are still contrasting results that seem to be due to a lack of comparative controlled studies. The presence of systemic and neurotoxic effects presently limits clinical use).

Evidence-based review of the literature on intrathecal delivery of pain medication

Evidence-based medicine depends on the existence of controlled clinical trials that establish the safety and efficacy of specific therapeutic techniques. Many interventions in clinical practice have achieved widespread acceptance despite little evidence to support them in the scientific literature; the critical appraisal of these interventions based on accumulating experience is a goal of medicine. To clarify the current state of knowledge concerning the use of various drugs for intraspinal infusion in pain management, an expert panel conducted a thorough review of the published literature. The exhaustive review included 5 different groups of compounds, with morphine and bupivacaine yielding the most citations in the literature. The need for additional large published controlled studies was highlighted by this review, especially for promising agents that have been shown to be safe and efficacious in recent clinical studies.

Spinal coadministration of ketamine reduces the development of tolerance to visceral as well as somatic antinociception during spinal morphine infusion

This study was designed to investigate the effects of ketamine, an N-methyl-D-aspartate receptor antagonist, on the development of tolerance to morphine and morphine antinociception during intrathecal infusion. Two intrathecal catheters were implanted in the subarachnoid space in male rats under pentobarbital anesthesia. One catheter was used for the intrathecal infusion with the following solutions: morphine 1 microg x kg(-1) x hr(-1)(M1) and 5 microg x kg(-1) x hr(-1) (M5);ketamine 250 microg x kg(-1) x hr(-1) (K250); morphine plus ketamine, 1 microg x kg(-1) x hr(-1) plus 250 microg x kg(-1) x hr(-1) (M1 + K250) and 5 microg x kg(-1) x hr(-1) + 250 microg x kg(-1) x hr(-1) (M5 + K250); or saline. The other catheter was used for morphine challenge tests. The responses to noxious somatic and visceral stimuli were measured by tail flick (TF) and colorectal distension (CD) tests, respectively. Measurements were performed once a day for 7 days. Challenge tests with intrathecal morphine were performed to assess the magnitude of tolerance on Day 5 and Day 7. The antinociceptive effect was evaluated by using the percent of maximal possible effect (%MPE). Morphine infusion produced significant increases in %MPEs in TF and CD tests, while the saline and K250 infusions did not show any changes. The M1 + K250 infusion significantly increased the %MPEs in TF and CD tests, although the M1 and K250 infusions alone showed no changes. M5 + K250 enhanced the increases of %MPEs in TF and CD tests compared with the M5 infusion alone. In the challenge tests, the M1 + K250 infusion showed no significant decrease in %MPEs and TF and CD tests. The M5 + K250 infusion significantly inhibited those decreases in %MPEs, although the M5 infusion showed significant decreases in TF and CD tests. We concluded that ketamine attenuated the development of morphine tolerance to antinociceptive effects and increased the somatic and visceral antinociception of morphine.

IMPLICATIONS

Intrathecally coinfused ketamine attenuated morphine tolerance to somatic and visceral antinociception and increased morphine antinociception at the spinal level. These results suggest that a combination of morphine with ketamine may have an advantage in long-term use of opioids for controlling visceral as well as somatic pain.

Histological findings after long-term infusion of intrathecal ketamine for chronic pain: a case report

Ketamine, a selective, noncompetitive N-methyl-D-aspartate (NMDA)-receptor antagonist, is able to alter pain perception at the spinal level. Little clinical data exist on the intrathecal and epidural use of ketamine in chronic pain. Histopathologic findings after intrathecal injection of ketamine with and without preservatives are rarely reported. This outcome was evaluated in a 72-year-old woman with abdominal pain due to cancer who was treated with the intrathecal application of bupivacaine, clonidine, and morphine. We reached satisfactory pain relief with the addition of ketamine to the mixture for 7 days. On postmortem, focal lymphocytic vasculitis close to the catheter injection site was found. This finding has not been described previously after long-term application of ketamine intrathecally. The intrathecal infusion of ketamine with preservative, or the mixture of ketamine, clonidine, morphine, and bupivacaine resulted in isolated lymphocytic vasculitis of the spinal cord and leptomeninges without any clinical signs of neurological deficit.

The neurotoxicity of drugs given intrathecally (spinal)

Overall, most spinal drugs in clinical use have been poorly studied for spinal cord and nerve root toxicity. Laboratory studies indicate that all local anesthetics are neurotoxic in high concentrations and that lidocaine and tetracaine have neurotoxic potential in clinically used concentrations. However, spinal anesthesia (including lidocaine and tetracaine) has a long and enviable history of safety. Spinal analgesics such as morphine, fentanyl, sufentanil, clonidine, and neostigmine seem to have a low potential for neurotoxicity based on laboratory and extensive clinical use. Most antioxidants, preservatives, and excipients used in commercial formulations seem to have a low potential for neurotoxicity. In addition to summarizing current information, we hope that this review stimulates future research on spinal drugs to follow a systematic approach to determining potential neurotoxicity. Such an approach would examine histologic, physiologic, and behavioral testing in several species, followed by cautious histologic, physiologic, and clinical testing in human volunteers and patients with terminal cancer refractory to conventional therapy.

[Neurotoxicity of intrathecally administrated agents]

Spinal anaesthetics can induce histopathologic lesions and regional haemodynamic alterations in the spinal cord. There are numerous causes of neurologic lesions, including direct trauma of the spinal cord and nerve roots during puncture or catheter insertion, compromised spinal cord perfusion and direct neurotoxic effect. Histopathologic lesions are localized either in meninges (meningitis or arachnoiditis) or in neuraxis (myelitis or axonal degeneration). Neurotoxicity can result from decrease in neuronal blood supply, elicited by high concentrations of the solutions, long duration exposure to local anaesthetics, and the use of adjuvants. They have been implicated in the occurrence of cauda equina syndrome after continuous spinal anaesthesia using hyperbaric solution of lidocaine and tetracaine given through small diameter catheters. Selective spinal analgesia is induced by spinal opioids without motor blockade except for meperidine. Complications occurred in patients after high doses of morphine, which were related to one of its metabolites, morphine-3-glucuronide. Preservative-free opioid solutions are to be preferred for spinal anaesthesia. There is no report of neurotoxicity neither in animal studies, nor in humans, using spinal clonidine. In order to reduce the incidence of neurotoxicity, some safety rules should be followed. The lowest efficient dose of local anaesthetics must be given. Incomplete blockade should not necessarily lead to a reinjection. Large volume of hyperbaric lidocaine or repeated injections of such solutions must be avoided as well as preservative-containing solutions. The administration of new compounds by the spinal route must be supported by data of spinal neuropharmacology and the lack of neurotoxicity must have been previously checked with animal studies.