Caudal block

A conduction block is a type of regional anesthesia produced by injection of a local anesthetic drug into or near a nerve trunk. Examples of a conduction block include an epidural block (injection of a local anesthetic into the space surrounding the dura of the spinal cord) a trails sacral (caudal) block (injection of a local anesthetic into the epidural space at the level of the sacrococcygeal notch) and brachial plexus block (injection of a local anesdietic into the brachial plexus). Epidural, especially, and trailssacral blocks are often used in obstetrics. A brachial plexus block may be used for surgery of the arm or hand. 

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). 

FIGURE 12-2 Sites of epidural and spinal administration of a local anesthetic. Caudal block represents epidural administration via the sacral hiatus. (From Clark JB, Queener SF, Karb VB. Pharmacological Basis of Nursing Practice. 4th ed. St Louis C V Mosby 1993 688. Reproduced with permission.]... 

Mepivacaine, which is ineffective topically, is used for infiltration plus nerve, epidural, and caudal block. Its potency and speed of action are similar to those of lidocaine. 

Constant I, Gall O, Gouyet L, Chauvin M, Murat I. Addition of clonidine or fentanyl to local anaesthetics prolongs the duration of surgical analgesia after single shot caudal block in children. Br J Anaesth 1998 80(3) 294-8. 

In a study in 60 anesthetized children undergoing minor subumbilical surgery caudal blocks, 0.2% ropivacaine, 0.25% racemic bupivacaine, and 0.25% levobupivacaine (all 1 ml/kg) were compared (81). All the blocks were successful in terms of intraoperative and early postoperative analgesia. Ropivacaine, but not levobupivacaine, was associated with less motor block during the first postoperative hour compared with racemic bupivacaine. However, the lower concentration of ropivacaine will have biased this result. 

Caudal block with bupivacaine in children provides adequate analgesia in the early postoperative period, but additional analgesia is often required as the block wears off. Two studies have looked at adjuvants to prolong the analgesic effect. 

Thirty children (1-5 years old) in an open, controlled study were randomly given caudal block with 0.25% bupivacaine 0.8 mg/kg or tramadol 0.8 or 2 mg/kg (5). The duration of analgesia was longer (9.1 hours) in those given tramadol but the incidences of opioid-related... 

Mepivacaine is indicated in production of local or regional analgesia and anesthesia by local infiltration, peripheral nerve block techniques, and central neural techniques including epidural and caudal blocks (see also Figure 31). 

Mepivacaine hydrochloride [N-(2, 6-dimethylphenyl)-1-methyl 2-piperidinecarboxamide monohydrochloride] is an amino amide-type local anesthetic agent widely used to provide regional analgesia and anesthesia by local infiltration, peripheral nerve block, and epidural and caudal blocks. The pharmacological and toxicological profile of mepivacaine is quite similar to that of lidocaine, except that mepivacaine has a slightly longer duration of action and lacks the vasodilator activity of lidocaine. For this reason, it serves as an alternate choice for lidocaine when addition of epinephrine is not recommended in patients with hypertensive vascular disease. 

Severe hypotension and bradycardia have been seen in patients taking captopril or verapamii when they were given epidurai anaesthesia with bupivacaine. Acute hypotension aiso occurred in a man taking prazosin when he was given epidurai anaesthesia with bupivacaine. Cionidine may increase the duration of caudal block with bupivacaine, aithough there are reports of reduced plasma levels of lidocaine with concurrent cionidine. Verapamil does not appear to interact with epidural lidocaine. 

A study in 35 children undergoing ureteroneocystostomy found that the addition of clonidine 1 microgram/kg increased the duration of caudal block with bupivacaine 0.125% (with adrenaline (epinephrine) 1 400 000) and reduced the postoperative morphine requirements. A study in animals found that clonidine inereased the levels of bupivacaine and decreased its clearance. However, another study in children found that oral clonidine premedication reduced the plasma levels of lidocaine by 25 to 50%. Similar findings are reported in another study in which clonidine was given with epidural lidocaine. ... 

A study in 20 children aged 2 to 7 years receiving caudal block with 1 mL/kg of a solution containing 0.5% lidocaine and 0.125% bupi-... 

Khalil SN, Matuszczak ME, Maposa D, Bolos ME, Lingadevaru HS, Chuang AZ. Presurgical fentanyl vs caudal block and the incidence of adverse respiratory events in children after orchidopexy. Paediatr Anaesth 2009 19(12) 1220-5. 

The first clinical uses of a local anesthetic agent occurred in 1884, when cocaine was employed as a topical agent for eye surgery and to produce a nerve block. These events inaugurated a new era, that of regional anesthesia. New applications were developed, including spinal, epidural, and caudal anesthesia. The search for a better local anesthetic led to chemical synthesis of a number of other compounds that have more selective local anesthetic properties and few systemic side effects. 

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.

In theory, epidural and spinal blocks can be done at any level of the cord, but they are usually administered at the L3-4 or L4-5 vertebral interspace (i.e., caudal to the L-2 vertebral body, which is the point where the spinal cord ends). Epidural anesthesia is somewhat easier to perform than spinal blockade because the epidural space is larger and more accessible than the subarachnoid space. However, spinal anesthesia is... 

Lidocaine is effective in producing analgesia when administered by infiltration, or by nerve, epidural, caudal, and spinal block. In addition, it is effective when applied topically, with an onset of action of 5 min and a duration of action of 15 to 30 min. Lidocaine (1.5 pg/ml) is the agent of choice for the acute suppression of most ventricular arrhythmias. 

Etidocaine is a long-acting derivative of lidocaine but is far more potent. It is effective for infiltration anesthesia, peripheral nerve block, and epidural and caudal blockade. 

In an abaxial sessamoid local anaesthetic model, the highest no-effect dose for the local anaesthetic effect of lidocaine was 4 mg (Harkins et al 1998). For caudal epidural anesthesia, dose rates of lidocaine alone of 0.25 (Csik-Salmon et al 1996) or 0.35mg/kg (Pikes et al 1989) have been proposed (i.e. 6-10 ml of a 2% solution). A maximum of 200 ml should be used for field blocks. The dose rates quoted for i.v. administration of either a 1% or 2% solution of lidocaine (without epinephrine (adrenaline)) are for loading doses of 0.65-5 mg/kg followed by a constant i.v. infusion of 25-100 gg/kg/min (Brianceau et al 2002, Doherty Frazier 1998). 

Fig. 164. The nucleo-olivary projection in the rat. Data from Ruigrok and Voogd (1990). Upper and lower block diagrams represent the cerebellar and vestibular nuclei, and the subdivisions of the inferior olive respectively. According to Ruigrok and Voogd (1990) the cerebellar nuclei and their olivary target nuclei can be considered as a continuum, stretching from the rostral medial cerebellar nucleus, projecting to caudal MAO, to the lateral vestibular nucleus, projecting to the dorsal fold of the DAO. DL = dorsolateral protuberance of the medial cerebellar nucleus DMC = dorsomedial cell column IntA = anterior interposed nucleus IntDL = dorsolateral hump IntP = posterior interposed nucleus lOD = dorsal accessory olive lODM = dorsomedial cell column lOM = medial accessory olive lOP = principal olive Lat = lateral cerebellar nucleus LVe = lateral vestibular nucleus Med = medial cerebellar nucleus VL = ventrolateral outgrowth.

Lumsden, 2001 Wendling et al., 2001). Blocking retinoid signaling therefore results in a caudal truncation of the hindbrain, with hindbrain disruptions being progressively more severe the earlier the treatment. In the most extreme form of retinoid deprivation elicited by antagonist treatments, the caudal hindbrain becomes truncated below r4, while the remaining rhombomeres are expanded. 

Chloroprocaine (1 to 2% injection with methylparaben as a preservative) is indicated in the production of local anesthesia by infiltration and peripheral nerve block. Chloroprocaine without methylparaben is indicated in peripheral and central nerve block, including lumbar and caudal epidural blocks. Chloroprocaine has an onset of action of 6 to 12 minutes. 

Lidocaine hydrochloride is a local anesthetic/vasopressor preparation. Lidocaine stabilizes neuronal membranes by inhibiting the ionic fluxes required for the initiation and conduction of impulses, thereby effecting local anesthetic action. Epinephrine stimulates both alpha and beta receptors within sympathetic nervous system relaxes smooth muscle of bronchi and iris and is an antagonist of histamine. They are indicated for production of local or regional anesthesia by infiltration techniques such as percutaneous injection, by peripheral nerve block techniques such as brachial plexus and intercostals, and by central neural techniques such as lumbar and caudal epidural blocks. 

Lidocaine is indicated for production of local or regional anesthesia by the infiltration technique, and by central neural techniques such as lumbar and caudal epidural blocks. 

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