Epidural 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. 

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. 

Bupivacaine is used for most types of regional, spinal and epidural block. It is not suitable for... 

Lidocaine is used for all forms of infiltration anaesthesia, in addition to peripheral, regional, spinal and epidural block. Unlike bupivacaine, it is suitable for use in intravenous regional anaesthesia. Duration of anaesthesia is about 1 hour but this can be prolonged to 2 hours by the addition of adrenaline. The maximum doses are shown in Table 5.2. 

When used for spinal anaesthesia, 0.75% ropivacaine produces less intense sensory and motor block than 0.5% bupivacaine. It is suitable for regional, spinal and epidural block but not for regional intravenous anaesthesia. The addition of adrenaline (epinephrine) does not prolong the duration of anaesthesia in brachial plexus or epidural block. Ropivacaine is indistinguishable from bupivacaine when used in obstetric anaesthesia. Its direct myocardial toxicity is somewhat less than that of bupivacaine. 

Portnoy D, Vadhera RB. Mechanisms and management of an incomplete epidural block for cesarean section. Anesthesiol Clin North America. 2003 21 39-57. 

Monedero P, Hess P. High epidural block with chloroprocaine in a parturient with low pseudocholinesterase activity. Can J Anaesth 2001 48(3) 318-19. 

Respiratory depression was noted in 0.24% of patients in a Chinese series of 10 978 epidural blocks (SED-12, 254) (126). Direct paralysis of respiration probably plays an important role. Respiratory depression with adverse cardiovascular effects after miscalculated dose requirements or a misplaced catheter has also been described (SEDA-22, 136). 

Horner s syndrome has been reported after lumbar epidural block in two other patients who were having lumbar epidural anesthesia for chronic pain treatment (144). The authors suggested that this complication had probably occurred through anatomical changes in the epidural space, leading to a high degree of sympathetic blockade. 

Hogagard JT, Djurhuus H. Two cases of reiterated Horner s syndrome after lumbar epidural block. Acta Anaesthesiol Scand 2000 44(8) 1021-3. 

Epidural block The injection is into the outer covering (dura mater) of the spinal cord near the sacrum. 

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. 

It is one of the least toxic and most commonly used local anaesthetics. The salient features for its wide popularity may be attributed due to its lack of local irritation, minimal systemic toxicity, longer duration of action, and low cost. It can be effectively used for causing anaesthesia by infiltration, nerve block, epidural block or spinal anaesthesia. In usual practice it is used in a solution containing adrenaline (1 50,000) which exerts and modifies the local anaesthetic activity through retarded absorption, and the duration of action is considerably prolonged. 

It is a long-acting local anaesthetic of the amide type, similar to mepivacaine and lidocaine but about four times more potent. The effects of bupivacaine last longer to lidocaine hydrochloride. It is mainly employed for regional nerve block, specifically epidural block, when a prolonged effect is required. 

Bupivacaine (e.g., Marcaine) Infiltration, spinal, epidural, and nerve block anesthesia. Long duration increases utility for epidural block during labor. Similar to lidocaine. IV administration may induce ventricular arrhythmias. 

Chloroprocaine (N,N -diethylaminoethyl 4-amino-2-chlorobenzoate) is a very short-acting, amino ester-type local anesthetic used to provide regional anesthesia by infiltration as well as by peripheral and central nerve block, including lumbar and caudal epidural blocks. The presence of a chlorine atom ortho to the carbonyl of the ester function increases its rate of hydrolysis by plasma cholinesterase at least threefold compared to procaine and benzocaine. Thus, chloroprocaine may be used in maternal and neonatal patients with minimal placental passage of chloroprocaine. The lower plasma cholinesterase activity in the maternal epidural space must still have sufficient activity for degrading chloroprocaine and, thus, not allowing it to cross the placenta barrier. 

Cardiovascular Successful resuscitation of a 5-week-old neonate with cardiac depression after a ropivacaine dose error has been reported [77" ]. The authors point out that experience of the use of Intralipid in neonates is so far limited, but another report of bupivacaine-induced cardiotoxicity in a neonate following caudal epidural block for urologic surgery resulted in a good outcome (see above). Prompt recognition of... 

Mepivacaine HCl 1 %, 2 % injection solution in sterile package Local infiltration anesthesia, epidural block... 

A smaller needle is used to perform a spinal block compared to an epidural block. 

With the spinal technique the medicines are injected into the cerebrospinal fluid that bathes the spinal cord with an epidural block, the medicines are delivered outside the dura, in the epidural space. 

Philip, J. H. and Brown W. U. (1976) Total spinal anesthesia late in the course of obstetric bupivacaine epidural block. Anesthesiology, 44, 340. 

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