[Neurotoxicity of intrathecally administrated agents]

Association between perioperative neuraxial local anesthetic neurotoxicity and arachnoiditis: a narrative review of published reports

BACKGROUND/IMPORTANCE

Arachnoiditis is a rare but devastating disorder caused by various insults, one of which is purported to be local anesthetic neurotoxicity following neuraxial blockade. However, the relationship between local anesthetics administered into the neuraxis and the development of arachnoiditis has not been clearly elucidated.

OBJECTIVE

We aimed to summarize the existing complex body of literature and characterize both the essential features and strength of any association between neuraxial local anesthetic neurotoxicity and arachnoiditis with a view toward mitigating risk, enhancing prevention, and refining informed consent discussions.

EVIDENCE REVIEW

We reviewed all published reports of arachnoiditis attributed to local anesthetic neurotoxicity following perioperative neuraxial anesthesia. This narrative review was based on a systematic search methodology, which included articles published up until December 2022.

FINDINGS

Thirty-eight articles were included, comprising 130 patients, over one-half of which were published prior to this century and inconsistent with modern practice. Neuraxial techniques included 78 epidurals, 48 spinals, and 5 combined spinal-epidurals, mostly for obstetrics. Reporting of essential procedural data was generally incomplete. Overall, at least 57% of patients experienced complicated needle/catheter insertion, including paresthesia, pain, or multiple attempts, irrespective of technique. The onset of neurological symptoms ranged from immediate to 8 years after neuraxial blockade, while the pathophysiology of arachnoiditis, if described, was heterogeneous.

CONCLUSIONS

The existing literature attributing arachnoiditis to local anesthetic neurotoxicity is largely outdated, incomplete, and/or confounded by other potential causes, and thus insufficient to characterize the features and strength of any association.

Dexmedetomidine and Bupivacaine Association in Caudal Epidural Injection in Mares

The objective of the study was to compare the effects of caudal epidural bupivacaine and dexmedetomidine (DEX) combination, with bupivacaine or DEX plain for perineal analgesia in mares. Six healthy saddle mares weighing 330-370 kg and aged 10-15 years were used in this study. Each mare was assigned to receive three treatments: 0.04 mg/kg 0.25% bupivacaine (BP), 2 μg/kg DEX (DX), or 0.02 mg/kg bupivacaine and 1 μg/kg DEX (BPDX). The order of treatments was randomized. All drugs were injected into the caudal epidural space (Co1-Co2) through a 16-G Tuohy epidural needle. After the epidural injections, heart rate, respiratory rate, arterial blood pressures (systolic, diastolic, and mean), and rectal temperature were measured at 5, 10, 15, 30, 60, 90, and 120 minutes, and after this time, every 60 minutes until the end of the experiments. A subjective score system was used to assess analgesia, behavioral and motor blockade at the same time points. The BPDX treatment produced analgesic action with twice the duration (200 minutes) of the BP treatment (97 minutes), but with an analgesic duration shorter than the DX treatment (240 minutes) in the regions of the tail, perineum, and upper hind limbs in mares. All treatments showed mild motor blockade. No behavioral changes were observed in any of the animals. There was hemodynamic stability without significant changes in respiratory rate for all treatments. Epidural analgesia using DEX alone or the combination of DEX and bupivacaine may be an option for painful obstetric and gynecological procedures in mares.

Comparison of analgesic and systemic effects of bupivacaine, methadone, or bupivacaine/methadone administered epidurally in conscious sheep

OBJECTIVE

The aim of this study was to evaluate the combination of bupivacaine and methadone administered epidurally in sheep.

METHODS

Six healthy female mixed-breed sheep weighing 35-46 kg and aged 12-18 months were included. Each sheep was assigned to receive three treatments: 0.5 mg/kg 0.25% bupivacaine (BP), 0.3 mg/kg 1% methadone (MT) or 0.25 mg/kg bupivacaine and 0.15 mg/kg methadone (BPMT). All drugs were injected into the lumbosacral space through an epidural catheter. Each animal received each treatment at random. Heart rate, arterial blood pressure (systolic, diastolic and mean), respiratory rate, rectal temperature, analgesia, sedation and motor block were determined before treatment and at predetermined intervals.

RESULTS

The duration of analgesia was 240, 220, and 180 min for BP, MT and BPMT, respectively (P < 0.05). Motor block for all agents was mild to moderate. None or the treatments significantly altered the heart rate, blood pressure or respiratory rate.

CONCLUSION

Our findings suggest that lumbosacral epidural administration of bupivacaine, methadone or a combination of the two drugs can provide perioperative analgesia in sheep as part of their management for surgical procedures in the flank and hindlimbs.

Evaluation of the clinical and analgesic effects of subarachnoid ketamine-lidocaine administration in goats undergoing mastectomy

Twenty adult female goats affected with chronic mastitis were subjected to mastectomy or hemimastectomy under subarachnoid regional analgesia using a ketamine-lidocaine combination. Ketamine at 1.5 mg/kg and lidocaine hydrochloride at 1.25 mg/kg were administered intrathecally at the lumbosacral intervertebral space. Goats were then subjected to a 120-minute observation period for systemic or neurotoxic symptoms such as agitation, restlessness, hind limb paralysis, or seizures. In addition, analgesia of the caudal abdominal region and signs of systemic sedation were scored on a scale of 0–3. Heart rate, respiratory rate, and rectal temperature were also recorded prior to (baseline values) and at 5, 15, 30, 60, 90, and 120 minutes after administration. Mastectomy or hemimastectomy operation was carried out after full assurance of the analgesic effect on the udder and caudal abdominal region. Time of onset of surgical analgesia (score 3) was achieved at 15 minutes and lasted for 60 minutes. Maximal sedation score was recorded at 15 minutes and lasted for 60 minutes, then decreased thereafter, with the lowest sedation score recorded at 120 minutes. There was a significant (P<0.05) rise in heart rate at some point between 5–90 minutes, while the respiratory rate and rectal temperature did not change significantly from baseline values. Postoperatively, animals did not show any signs of pain or discomfort. Follow-up on the operated goats showed that all wounds were fully healed without any significant complications. In goats, intrathecal administration of ketamine-lidocaine combination resulted in a safe and effective analgesia of the caudal abdominal and udder region sufficient to perform mastectomy or hemimastectomy.

Evaluation of segmental dorsolumbar epidural analgesia with ketamine hydrochloride administered by use of nonstyletted multiple-port catheters via the caudal approach in cattle

OBJECTIVE

To evaluate use of nonstyletted multiple-port catheters for epidural administration of ketamine hydrochloride via the caudal approach to induce analgesia of the paralumbar fossa (flank) in cattle.

ANIMALS

6 healthy bulls.

PROCEDURES

1 week before experiments began, a multiple-port catheter was inserted by use of a Tuohy needle in all cattle via the caudal approach (between the first and second coccygeal vertebrae); the tip was threaded approximately 48 cm cranial into the dorsolumbar region. Each bull was administered ketamine (0.3, 0.5, or 0.7 mg/kg) at time 0. Heart rate, blood pressures, respiratory rate, rectal temperature, analgesia, sedation, and ataxia were determined before treatment (baseline [time 0]); at 5, 10, 15, 30, 45, 60, 75, and 90 minutes; and every 30 minutes thereafter until end of analgesia.

RESULTS

All multiple-port catheters were threaded with negligible resistance into the dorsolumbar region in all bulls. All doses of ketamine were effective for inducing analgesia of the flank region of bulls in a standing position. Total analgesia time was dose dependent (35, 50, and 80 minutes for 0.3, 0.5, and 0.7 mg/kg, respectively). All doses of ketamine induced mild or moderate ataxia. Heart rate changes were within acceptable limits.

CONCLUSIONS AND CLINICAL RELEVANCE

Segmental dorsolumbar epidural analgesia with ketamine administered via multiple-port catheters by use of the caudal approach in cattle was feasible, and the cattle remained standing with minimal adverse effects. Further studies are necessary to determine whether this technique provides optimal conditions to allow surgery in standing cattle.

Optimizing pain control through the use of implantable pumps

Intrathecal therapy represents an effective and well established treatment of nonmalignant as well as malignant pain. Devices available include mechanical constant flow pumps as well as electronic variable flow pumps with patient-controlled bolus release. The latter provide faster dose finding, individual pain control, and good acceptance by patients. New technologies such as membrane pumps and rechargeable devices are expected to be developed to clinical perfection. The available drugs for intrathecal therapy are listed according to the polyanalgesic consensus on intrathecal therapy. The integration of remote patient-controlled analgesia into electronic implantable devices, and the peptide analgesic ziconotide, have significantly improved intrathecal therapy. Complications include infections, catheter ruptures or disconnections, catheter granulomas, and technical dysfunctions. Further possibilities for optimizing intrathecal therapy include development of new drugs, drug side effects, catheter and pump technologies, and surgical techniques.

Exacerbation of preexisting neurological deficits by neuraxial anesthesia: report of 7 cases

We undertook this case series to determine if preexisting neurological disease is exacerbated by either spinal or epidural anesthesia. In the website of the Arachnoiditis Foundation, we posted an offer to advise anesthesiologists in cases of neurological problems after either of these techniques was used. Contacts were made first by way of the Internet, confirmed by telephone, and maintained by fax, e-mail, or by special mail. Patients here described were cared for and observed by one of the authors, in a hospital, in Argentina or in Mexico. A total of 7 adult, ASA physical status I and II patients, including 3 men and 4 women, with subtle symptoms of neurological disease before anesthesia, are described. Two patients had continuous lumbar epidural anesthesia, 3 had spinals; in 2 more, attempted epidural blocks led to accidental dural puncture and were converted to subarachnoid anesthetics. All patients accepted neuraxial anesthesia without informing the anesthesiologists that they had mild neurological symptoms before surgery. Because anesthesiologists did not specifically inquire about subclinical neurological symptoms or prior neurological disease, anesthesiologists are advised to carefully inquire about prior neurological disease whether neuraxial anesthesia techniques are considered.

Toxic effects of epidural analgesia with ropivacaine 0.2% in a diabetic patient

A 51-year-old ASA physical status II, non-insulin-dependent diabetic male patient manifested lower limb nerve injury after receiving postoperative epidural analgesia with ropivacaine 0.2%. The case is presented, including a discussion of the relation between local anesthetic toxicity and diabetic neuropathy.

Spinal cord lesion after long-term intrathecal clonidine and bupivacaine treatment for the management of intractable pain

Long-term intrathecal drug administration using implanted pumps is increasingly used in the treatment of chronic refractory pain [Anderson and Burchiel 1999, Neurosurgery 44 (1999) 289; Krames 2002, Best Pract Res Clin Anaesthesiol 16 (2002) 619; Wallace 2002, Neurology 59 (2002) S18]. Extensive clinical experience over the last 15 years suggests that in selected cases the technique is safe, although infections, system malfunction and drug-related complications have been reported. In most cases, drug-related spinal cord injuries have resulted from the compression of a spinal inflammatory mass or abcess rather than from a direct neurotoxic effect. We report on a case of toxic spinal cord lesion occurring after more than 3 years of uneventful continuous infusion of a mixture of bupivacaine and clonidine.

Neurologic deficits and arachnoiditis following neuroaxial anesthesia

Of late, regional anesthesia has enjoyed unprecedented popularity; this increase in cases has brought a higher frequency of instances of neurological deficit and arachnoiditis that may appear as transient nerve root irritation, cauda equina, and conus medullaris syndromes, and later as radiculitis, clumped nerve roots, fibrosis, scarring dural sac deformities, pachymeningitis, pseudomeningocele, and syringomyelia, etc., all associated with arachnoiditis. Arachnoiditis may be caused by infections, myelograms (mostly from oil-based dyes), blood in the intrathecal space, neuroirritant, neurotoxic and/or neurolytic substances, surgical interventions in the spine, intrathecal corticosteroids, and trauma. Regarding regional anesthesia in the neuroaxis, arachnoiditis has resulted from epidural abscesses, traumatic punctures (blood), local anesthetics, detergents, antiseptics or other substances unintentionally injected into the spinal canal. Direct trauma to nerve roots or the spinal cord may be manifested as paraesthesia that has not been considered an injurious event; however, it usually implies dural penetration, as there are no nerve roots in the epidural space posteriorly. Sudden severe headache while or shortly after an epidural block using the loss of resistance to air approach usually suggests pneumocephalus from an intradural injection of air. Burning severe pain in the lower back and lower extremities, dysesthesia and numbness not following the usual dermatome distribution, along with bladder, bowel and/or sexual dysfunction, are the most common symptoms of direct trauma to the spinal cord. Such patients should be subjected to a neurological examination followed by an MRI of the effected area. Further spinal procedures are best avoided and the prompt administration of IV corticosteroids and NSAIDs need to be considered in the hope of preventing the inflammatory response from evolving into the proliferative phase of arachnoiditis.

The epidural and intrathecal administration of somatotrophin-release inhibiting factor: native and synthetic analogues

It is well-known that morphine is the king of analgesics. It is widely used, and administered in various ways for the control of acute and chronic pain states. There are, however, certain types of pain and certain clinical conditions in which morphine cannot be used due to the risk of possible complications. These are usually pain states associated with intracranial hypertension, the presence of serious respiratory problems, the onset of major opioid tolerance, persistent vomiting, and so on. The search for "alternative analgesics" has been in progress for a decade, alternatives that could be used alone or in combination for spinal administration in the treatment of complex chronic pain states and with a low incidence of secondary effects. Today, research is carefully assessing the clinical effectiveness and the side effects of a series of drugs for spinal administration, that is, epidural or intrathecal, such as the new narcotics, alpha-2 agonists, central muscle relaxants, calcitonin, and local anesthetics. In this alternative analgesic category we have to mention the somatotrophin-release inhibiting factor (SRIF), which is an ubiquitous native hormone with widespread, predominantly inhibitory actions, and octreotide, its synthetic analogue. In this article we review the literature on the natural drug and its synthetic analogue, paying particular attention to the problems connected with intraspinal administration and analgesic properties.

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).