Nerve block anaesthesia

Nerve block anaesthesia in general practice mostly concerns finger or toe blocks. Lidocaine or prilocaine, 10 mg/ml without adrenaline (norepinephrine), is used and is injected on each side of the finger or toe, in two portions by the four nerve branches. Injection of larger volumes than 1-2 ml/side carries a risk of ischaemia because of the firm tissue. The transport through the nerve sheath takes a few minutes, and for a satisfactory result one should wait 5-10 minutes before the planned intervention starts. 

This is a special type of nerve block anaesthesia in which the drug is injected into the epidural space. It is technically a more difficult procedure. The roots of the spinal nerves are anaesthetized. 

Dose For infiltration anaesthesia 1% for nerve block anaesthesia 1 and 2% solution andfor topical application to skin and mucous membranes 1 to 5%. 

It is a local anaesthetic of the amide type which is employed for surface, infiltration and nerve block anaesthesia. Its duration of action is in between the shorter-acting lidocaine and longer-acting mepivacaine. It possesses less vaso-dilator activity than lidocaine and hence may be used without adrenaline. Therefore, solutions of prilocaine hydrochloride are specifically beneficial for such patients who cannot tolerate vasopressor agents patients having cardiovascular disorders, diabetes, hypertension and thyrotoxicosis. 

Danelli G, Eanelli A, Ghisi D, Moschini M, Ortu A, Baciarello M, and Eanelli G (2009) Ultrasound vs nerve stimulation multiple injection technique for posterior popliteal sciatic nerve block. Anaesthesia 64 638-642. 

The use of local anaesthetics outside specialized surgical or anaesthetical practice is usually limited to infiltration anaesthesia, different surface anaesthetic methods, and (nerve) block of fingers and toes. Lo-... 

Lignocaine injections are indicated for production of local or regional anaesthesia by infiltration techniques such as percutaneous injection, peripheral nerve block, spinal or subarachnoid block. 

It is a potent and long acting local anaesthetic used for spinal, infiltration, epidural anaesthesia and nerve block. 

Adrenaline along with local anaesthetics may be used for infiltration, nerve block and spinal anaesthesia for prolonging the action and to reduce the systemic toxicity of local anaesthetics. 

Bupivacaine is long-acting 3 h) (see Table 18.1) and is used for peripheral nerve blocks, and epidural and spinal anaesthesia. Whilst onset of effect is comparable to lidocaine, peak effect occurs later (30 min). 

FaneUi G, Casati A, Magistris L, Berti M, Albertin A, Scarioni M, Torri G. Fentanyl does not improve the nerve block characteristics of axillary brachial plexus anaesthesia performed with ropivacaine. Acta Anaesthesiol Scand 2001 45(5) 590-4. 

It has a slow onset of action, up to 30 minutes, and a long duration of action, up to eight hours when used for nerve block. Bupivacaine can also be used with adrenaline. Bupivacaine is often used to produce continuous epidural anaesthesia during labour. 

The nerve poisons, or neurotoxins, are wonderfully well designed to act quickly to immobilise the snake s prey or attacker. They inhibit the formation or conduction of nerve impulses and so prevent movement. This is a particularly sinister approach to securing prey, because the unfortunate animal is immobilised while not being killed. Indeed, it is likely that in some cases the prey is conscious and aware, but simply unable to move because the venom acts as a motor nerve block (a similar approach is used in anaesthesia to facilitate muscle relaxation, particularly in abdominal surgery and one hears of horror stories of immobilised, helpless patients being subjected to surgery while not properly anaesthetised — this is how the snake s prey might feel ). 

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 local anaesthetic used for infiltration, peridural, nerve block, and caudal anaesthesia. It is found to be twiee as potent as procaine. It has been reported that its duration of action is significantly longer than that of lidocaine, even without adrenaline. Henee, it is of particular importance in subjects showing contraindication to adrenaline. 

Neuromuscular blocking agents (curare alkaloids and certain synthetic compounds), which interfere with transmission from motor nerve endings to the membrane of the skeletal muscle, are of great practical interest. They are used in anaesthesia (to reduce the muscle tonus) and in psychiatric electroshock therapy (to reduce the intensity of... 

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 presenee of the anaesthesiophoric moiety in cocaine, discovered in the year 1880, employed profusely as a vital loeal anaesthetie in various surgical procedures by virtue of its ability to cause anaesthesia by blocking nerve conductance, ultimately paved the way for the synthesis of thousands of new compounds known as local anaesthetics . However, about twenty such compounds have gained recognition and congnizance as local anaesthetics in the therapeutic armamentarium. 

Techniques range from inhltraiion of anac-sthctic around a single nerve (e.g. dental anaesthesia) to epidural and spinal anaesthesia. In. spinal anaesthesia (intrathecal block) a drug is injected into the ccrebrospina) fluid in the subarachnoid space. In epidural anaesthesia the anaesthetic is injected outside the dura. Spinal anaesthesia is technically far easier to produce than cpidural anaesthesia, but the latter technique virtually eliminates the postanaesihetic complications such as headache. 

No stimulant drugs are known in this class which consists mainly of the local anaesthetics, much used in dental and spinal anaesthesia. These preferentially block the smaller fibres with the result that sensory nerves are affected more than motor nerves. What local anaesthetics do is to elevate the threshold for excitation and thus they block propagation of the nervous impulse without depolarizing the fibre. 

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