Pain impulses are formed by the irritation of the free nerve endings. Their specificity is limited. Nerve fibres running from them, combine to form nerve trunks, then included with the posterior roots of the spinal cord. Having made the crossing by tractus spinotalamicus lateralis, pulses rise in the thalamus, where they are switching to other parts of the brain. The path of pain impulses can be interrupted in different places.
In accordance with the block level there are following kinds of local anesthesia: a terminal (blockade of receptors by), irrigate mucous membranes with a solution of local anesthetic – which leads to interruption of the pulses at the beginning of the reflex arc; infiltration (blockade of receptors and small nerves), conduction (nerve blockage and other plexuses). Epidural and spinal anesthesia are a special type of regional anesthesia, where the blockade is carried out at the level of the posterior roots of the spinal cord.
Indications for local anesthesia determined by its advantages:
simplicity of technical implementation, minimal toxicity, sufficient efficacy, the use of when contraindication to anesthesia
Contraindications: intolerance patients anaesthetics, due to increased individual sensitivity, age less than 10 years, a patient of mental illness, the presence of inflammatory or cicatricial changes in the tissues. In addition, a local anesthetic is contraindicated as the main type in a lengthy and traumatic surgical procedures, as well as during operations requiring mechanical ventilation.
The mechanism of action of anesthetics: having lepidocephalus, anesthetic molecule is concentrated in the membranes of nerve fibers, while they block the function of sodium channels, preventing the spread of the action potential. When exposed to anesthetic receptors lose their ability to perceive stimuli and becomes impossible a nerve impulse.
Local anesthetics block conduction in the following order: small myelinated axons (e.g. those carrying nociceptive impulses), non-myelinated axons, then large myelinated axons. Thus, a differential block can be achieved (i.e. pain sensation is blocked more readily than other sensory modalities).
Depending on the chemical structure of local anesthetics are divided into 2 groups: ether-derivatives of procaine (novocaine), and chloroprocaine tetracaine (tetracaine) or amide - type derivatives of lidocaine (prilocain, mepivacaine, bupivacaine or marcain). Local anesthetics ether undergo rapid hydrolytic degradation in the tissues, and after a certain period of time lose their effectiveness - there is a valid repeated injections of the drug. Allergic reactions are possible.
Local anesthetics of the amide type does not undergo hydrolytic destruction in the tissues, and excreted from the body unchanged or undergo partial decomposition in the liver. Re-introductions should take into account the maximum permissible dose. Allergic reactions do not cause.
Anesthetics ether:1. Novocaine (procaine, penguin)- low toxicity. For infiltration anesthesia is used 0.25% solution; wiring for epidural and spinal anesthesia use more concentrated solutions (0,5%,1,0% and 2.0%). During the operation under m\and you should not spend more than 1000 ml of 0.25% R-RA novocaine for 1 hour operation.
2. Dicain (pontocaine)- well absorbed through mucous membranes and therefore used to produce surface anaesthesia of mucous membranes (0,5; 1;2;3% solutions); and for the conduct of epidural anesthesia. For infiltration anesthesia it is not suitable, as in 10 times more toxic than procaine.
Anesthetics: amide having the structure (lidocaine group)
1. Lidocaine - does not cause irritation in the tissues. The analgesic effect is 2 times higher than that of procaine. When the surface anesthetic action was 4 times higher than that of tetracaine. Anesthesia (infiltration, conduction) occurs within 1 minute. The advantage of lidocaine before novocaine (Pro-Cain) is that it has all the performance, as with infiltration introduction and surface applications.
2. Piromekain- 0,5-1-2% solution in ampoules. Maximum dose of 1000mg. Used mainly for surface anesthesia of the mucous membranes of the respiratory tract and in ophthalmology.
3. Bupivacaine (marcain) - one of the most common modern drugs for infiltration and block anesthesia (spinal – 0,5-1%. The maximum dose of 2 mg per 1 kg of body weight. 2-3 times stronger than lidocaine.
4. Trimekain (masakan)- 0,25; 0,5; 1,2% solutions. The maximum daily dose Exceeds 2R. novocaine anesthetic effect, longer. Used in all kinds of local anesthesia, but often with epidural and regional anesthesia. Depending on the level anesthesia and how to achieve it, taking into account the place of anesthetic effects on the nervous system there are different kinds of local anesthesia.
1.Terminal anaesthesia. Used only for anesthesia of mucous membranes, most often in clinics-ear, nose and throat, ophthalmology, as well as during endoscopy. Mucous cover anesthetic drugs by smearing, spraying or drip the introduction of anesthetics. The most suitable for these purposes tetracaine 0.5% -2% lidocaine solution.
Local anesthesia by A. Vishnevsky, which he called the method of "creeping infiltration", is provided by layer-by-layer by the introduction under pressure of 0.25% solution of novocaine in anatomical cases of the human body. Spreading them in the anesthetic solution, washes nerve branches and the end, causing immediate pain relief. A precondition of this type of anesthesia is tight lamellar tissue infiltration anesthetic solution during the surgical incision, with frequent changes of the scalpel and syringe with novocaine solution: infiltration - section.
The method of block anesthesia is based on interruption of conduction of nerve fibers anesthetic. Anesthetic solution is injected into a nerve or perineural tissue. The nerve is surrounded by shells all over, so I use more concentrated solutions (1-2%) novocaine, lidocaine, trimecaine.
When stem regional anesthesia the anesthetic solution is injected endoneural (directly into the nerve trunk) or perineural - in the tissue surrounding the nerve. In outpatient practice in operations on the fingers of the most frequently used method of Oberst-Lukashevich. Anesthesia is performed by the side surfaces of the finger, preferably under the harness ; after 5-10 minutes comes the anaesthesia of the entire finger. Trauma with multiple fractures of the ribs hold the intercostal nerve blockade, injecting 10-15 ml of 1% solution of novocaine under the lower edge of the ribs.
Slaid 20 Plexus Blockade
Injection of local anesthetic adjacent to a plexus, e.g cervical, brachial or lumbar plexus
surgical anesthesia or post-operative analgesia in the distribution of the plexus
large area of anesthesia with relatively small dose of agent
technically complex, potential for toxicity and neuropathy.
Epidural anesthesia is a type of regional anesthesia. The analgesic effect is achieved by blockade of sensory and motor roots of the spinal cord anesthetic drug injected into the epidural space between the outer and inner leaflets of the Dura mater of the spinal cord. Anesthesia of the boundary nodes of the trunk in the propagation of anesthetic through the intervertebral foramen, leading to the blockade, reversible paralysis vasomotoric fibers and consequently the expansion of arterioles and reduce blood pressure due to blood redistribution.
Technique of puncture of the epidural space. The injection should be carried out on the medial line at the level of III-IV lumbar vertebra. The spinal cord ends at the level II lumbar vertebra. The patient is in position either lying on your side, or sitting. To increase the gaps between the spinous processes, maximum patient leans forward. The line formed by the crests of the iliac bones, intersects with the body of the vertebra IV, start here anesthesia of the skin. Then the needle Bira with mandrin in a strictly sagittal plane pierce the skin, subcutaneous tissue and underlying ligaments. The stylet is removed, the needle attached to the syringe filled with saline with air bubbles, the needle is advanced to the yellow ligament and then through it. At the same time to enter the anesthetic solution is not possible, an air bubble in the syringe is compressed. After the passage of the ligament, the bubble expands, and the solution begins to flow easily inside. This loss of resistance (Symptom of Tolyatti). The main sign of penetration into the epidural space , which is administered 5 ml of the anesthetic solution. The anesthetic may be entered once, but can also be used to insert a catheter through the lumen of the needle fractional introduction of anesthetic, during, and after surgery.
Complications of epidural anesthesia:
1. Vascular collapse - as a result of paralysis of the vasoconstrictors innervated by the sympathetic nervous system in anestesiology region is a redistribution of blood (deposition), accompanied by pressure drop.
2. Total spinal block in case of accidental puncture of the Dura mater and the introduction of the anesthetic solution, with its subsequent distribution in the cerebrospinal fluid, as when an epidural anesthetic dosage of the substance is 10 times higher than in spinal cord, resulting in its rapid spread to the medulla oblongata develops collapse and respiratory paralysis (total spinal block.)
Definition Anesthesia following local anesthetic injection into lumbar subarachnoid space
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