Spinal nerve blockade

Central neural blockade. The anesthetic is injected within the spaces surrounding the spinal cord10 (Fig. 12-2). Specifically, the term epidural nerve blockade refers to injection of the drug into the epidural space—that is, the space between the bony vertebral column and the dura mater. A variation of epidural administration known as a caudal block is sometimes performed by injecting the local anesthetic into the lumbar epidural space via the sacral hiatus (see Fig. 12-2). Spinal nerve blockade refers to injection within the subarachnoid space— that is, the space between the arachnoid membrane and the pia mater. Spinal blockade is also referred to as intrathecal anesthesia because the drug is injected within the tissue sheaths surrounding the spinal cord (intrathecal means within a sheath see Chapter 2). 

During spinal anesthesia, motor paralysis may impair respiratory activity, and residual autonomic nerve blockade can lead to hypotension upon ambulation. Residual autonomic blockade also interferes with bladder function, resulting in urinary retention and the need for bladder catheterization. 

The choice of local anesthetic for infiltration, peripheral nerve blocks, and central neuraxis (spinal/epidural) blockade is usually based on the duration of action required. Procaine and chloroprocaine are short-acting lidocaine, mepivacaine, and prilocaine have an intermediate duration of action and tetracaine, bupivacaine, levobupivacaine, and ropivacaine are long-... 

Chung model (spinal nerve ligation) SNX-111 0. 03, 0.1 and 0.3 pg 1. t. Dose-dependent blockade of mechan. allodynia in neuropathy rats Bowersox et al. (1998)... 

Subarachnoid (intrathecal) block (spinal anaesthesia). By using a solution of appropriate specific gravity and tilting the patient the drug can be kept at an appropriate level. Sympathetic nerve blockade causes hypotension. Headache due to CSF leakage is virtually eliminated by using very narrow atraumatic penal point needles. 

The applications of computer tomography (CT)-guided interventions range from precise neurolytic block (neurolysis) of somatic spinal nerves and neurolytic sympathetic blockade to tumor alcoholization and percutaneous cementoplasty (Kanpolat et al. 1990 Gangi et al. 1994a Quinn et al. 1988). 

Lee DH, Chang L, Sorkin LS, Chaplan SR (2005) Hyperpolaiization-activated, cation-nonselective, cyclic nucleotide-modulated channel blockade alleviates mechanical allodynia and suppresses ectopic discharge in spinal nerve ligated rats. J Pain Off J Am Pain Soc 6 417-424... 

At peripheral nerves the reduction in sodium influx leads to a decrement in action potential formation and propagation. In animal studies a reduction in action potential by 50% is necessary for observable loss of neuronal function and exposure length of the nerve fiber is important in conduction blockade [41]. At central neuraxial administration of LA similar mechanisms to those previously discussed occur at the level of the spinal nerve roots. Additionally, at the dorsal horn, LA possibly exert action at sodium and potassium chaimels in ventral and dorsal horn neurons [41]. Furthermore local anesthetics may exert action at neurotransmitters or neuropeptides such as substance P or y-aminobutyric acid (GABA) by either directly binding to receptors or by altering local pharmacokinetics of endogenous agonists [41 ]. 

Local anesthetics are used for topical anesthesia, local infiltration, peripheral nerve block, paravertebral anesthesia, intravenous block also known as regional anesthesia, epidural block, and spinal i.e. subarachnoid blockade. The local anesthetics may be divided into two main groups, the esters and the amide-type agents. 

Regional block, a form of anesthesia that includes spinal and epidural anesthesia, involves injection near a nerve or nerve plexus proximal to the surgical site. It provides excellent anesthesia for a variety of procedures. Brachial plexus block is commonly used for the upper extremity. Individual blocks of the sciatic, femoral, and obturator nerves can be used for the lower extremity. An amount that is close to the maximally tolerated dose is required to produce blockade of a major extremity. 

Application to the nerve cell ending would result only in topical anesthesia, and blockade of the neuromuscular junction could produce respiratory failure. Administration to the spinal cord is too general an answer. The injection must be near a nerve or nerve plexus proximal to the surgical site. 

Schematic diagram of the typical sites of injection of local anesthetics in and around the spinal canal. When local anesthetics are injected extradurally, it is known as epidural (or caudal) blockade. Injections around peripheral nerves are known as perineural blocks (eg, paravertebral block). Finally, injection into the subarachnoid space (ie, cerebrospinal fluid), is known as spinal blockade.

Moreover, duration of central NKi receptor blockade is a critical point, as anesthetic-like nerve block caused by non-specific effects on ion channels in peripheral tissues could mask the selective antinociceptive effects of blocking NKi receptors in the spinal cord. The long-acting NKi antagonist L-733,060 maintained blockade of central NKi receptors at a time when peak plasma drug levels had subsided. Therefore, in paw licking experiments, the inhibitory effect of L-733,060 appeared to be due to central NKi receptor blockade (Rupniak et al., 1996). 

The concentration of local anesthetic used determines the type of nerve fibers blocked The highest concentrations are used when sympathetic, somatic sensory, and somatic motor blockade are required. Intermediate concentrations allow somatic sensory anesthesia without muscle relaxation. Low concentrations will block only preganglionic sympathetic fibers. A significant difference between epidural and spinal anesthesia is that the dose of local anesthetic used can produce high concentrations in blood following absorption from the epidural space. 

A. Toxicity owing to local anesthetic effects includes prolonged anesthesia and, rarely, permanent sensory or motor deficits. Spinal anesthesia may block nerves to the muscles of respiration, causing respiratory arrest, or may cause sympathetic blockade, resulting in hypotension. 

Since the preparation of the earlier review, new interest in the molecular compound picrotoxin has hinged upon its influence on the learning process [921] and its exact mode of action in the CNS. Like strychnine, picrotoxin diminishes inhibition within the CNS, but in contrast to strychnine it has no effect on post-s5maptic inhibition in the spinal cord [873, 885]. Instead, it would appear to interfere with pre-synaptic inhibition, itself a complex process which reduces the amount of excitatory transmitter released from pre-synaptic nerve endings [942-951], but since even very large doses of picrotoxin fail to block pre-synaptic inhibition as effectively as small doses of strychnine block post-synaptic inhibition, interpretation simply in terms of blockade of pre-synaptic inhibition may not be a fully vahd explanation of the central effects of picrotoxin. 

When systemic or topical pharmacotherapy and other non-invasive approaches provide inadequate relief in patients with NP, interventional approaches may be used, including sympathetic blockade with local anesthetics, intraspinal drug delivery, spinal cord stimulation, peripheral subcutaneous nerve stimulation, or stimulation of specific central nervous system structures, and various neuroablative procedures (e.g. dorsal rhizotomy, neurolytic nerve block, intracranial lesioning). Neuroablative procedures are not reversible and should be reserved for carefully and properly selected patients with intractable pain. 

Meperidine reversibly blocks voltage-gated Na currents with a half-maximum inhibiting concentration (ICjg) of 112 pM. Clinically, meperidine shows a dose-dependent blockade of both the sensory and motor fibers of the ulnar nerve after infiltration. Two percent meperidine blocks both sensory and motor activity at the hypothenar muscle. Intrathecal doses of meperidine 50 mg can provide short-duration spinal anesthesia. 

Surgical acute pain bupivacaine is indicated as a local anesthetic and used for infiltration, peripheral nerve block, nerve plexus blockade, epidural, and intrathecal (spinal) anesthesia and analgesia. It can be used as a single-shot injection or administered through a catheter for prolonged anesthesia and/or analgesia. 

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