Anesthesia spinal

The advantages of spinal anesthesia are the ease of administration, rapid onset of anesthesia, and good muscular relaxation, plus it allows patients to remain awake. 

The disadvantages of spinal anesthesia are hypotension (ephedrine and methoxamine may prevent this), nausea and vomiting (avoided by thiopental), respiratory depression (treated by artificial respiration), and postoperative headache (treated by increasing the CSF pressure). 

FIGURE 23.6 Administration of anesthetics into subarachnoid space. T12 = 12th thoracic nerves L1( L2, L3, L4, Ls = first, second, third, fourth, and fifth lumbar nerves Sl5 S2 = first and second sacral nerves. 

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Tetracaine (20, X = H, R = R = is primarily used in spinal anesthesia providing a slow onset, high potency, and a long duration of... 

Lidocaine hydrochloride [73-78-9] (Xylocaine), is the most versatile local anesthetic agent because of its moderate potency and duration of action, rapid onset, topical activity, and low toxicity. Its main indications are for infiltration, peripheral nerve blocks, extradural anesthesia, and in spinal anesthesia where a duration of 30 to 60 min is desirable. Because of its vasodilator activity, addition of the vasoconstrictor, epinephrine, increases the duration of action of Hdocaine markedly. It is also available in ointment or aerosol preparations for a variety of topical appHcations. 

Occurs as a result of circulatory insufficiency associated with overwhelming infection Occurs when obstruction of blood flow results in inadequate tissue perfusion. Examples include a severe reduction of blood flow as the result of massive pulmonary embolism, pericardial tamponade, restrictive pericarditis, and severe cardiac valve dysfunction Occurs as a result of blockade of neurohum oral outflow. Examples include from a pharmacological source (ie, spinal anesthesia) or direct injury to the spinal cord. This type of shock is rare. 

Spinal anesthesia is a type of regional anesthesia that involves the injection of a local anesthetic drug into the subarachnoid space of die spinal cord, usually at the level of the second lumbar vertebra There is a loss of feeling (anesdiesia) and movement in the lower extremities, lower abdomen, and perineum. 

Discuss the mechanisms by which spinal anesthesia and epidural anesthesia exert their effects... 

Injecting a local form of anesthetic into the cerebrospinal fluid surrounding the spinal cord causes spinal anesthesia. This injection is made below the level of the second lumbar vertebra in order to minimize direct nerve trauma. Spinal anesthesia is... 

The primary site of action of epidurally administered agents is on the spinal nerve roots. As with spinal anesthesia, the choice of drug to be used is determined primarily by the duration of anesthesia desired. However, when a catheter has been placed, short-acting drugs can be administered repeatedly. Bupivacaine is typically used when a long duration of surgical block is needed. Lidocaine is used most often for intermediate length procedures chloroprocaine is used when only a very short duration of anesthesia is required. 

An important difference between epidural anesthesia and spinal anesthesia is that agents injected into the epidural space may readily enter the blood due to the presence of a rich venous plexus... 

Forms of local anesthesia. Local anesthetics are applied via different routes, including infiltration of the tissue (infiltration anesthesia] or injection next to the nerve branch carrying fibers from the region to be anesthetized (conduction anesthesia of the nerve, spinal anesthesia of segmental dorsal roots), or by application to the surface of the skin or mucosa (surface anesthesia]. In each case, the local anesthetic drug is required to diffuse to the nerves concerned from a depot placed in the tissue or on the skin. 

In regional anesthesia (spinal anesthesia) with a local anesthetic (p. 204), nociception is eliminated, while consciousness is preserved. This procedure, therefore, does not fall under the definition of general anesthesia... 

Spinal anesthesia Spinal anesthesia is the introduction of local anesthetics directly into the spinal fluid, which causes a sympathetic blockage, or loss of feeling as well as muscle relaxation resulting from the interaction of anesthetic with every spinal nerve tract. This method is used during major surgical interventions. As a rule, lidocaine, mepivacaine, and bupivacaine are used for this purpose. 

Lidocaine is the most widely used local anesthetic. Its excellent therapeutic activity is fast-acting and lasts sufficiently long to make it suitable for practically any clinical use. It stabilizes cell membranes, blocks sodium channels, facilitates the secretion of potassium ions out of the cell, and speeds up the repolarization process in the cell membrane. It is used for terminal infiltration, block, epidural, and spinal anesthesia during operational interventions in dentistry, otolaryngology, obstetrics, and gynecology. It is also used for premature ventricular extrasystole and tachycardia, especially in the acute phase of cardiac infarction. Synonyms for this drug are xylocaine, neflurane, and many others. 

It is used in hypotensive shock for the purpose of elevating blood pressure, which can result from spinal anesthesia, surgical complications, and head trauma. Synonyms of metaraminol are aramine, isophenylephrin, metaradine, and others. 

When neuraxial anesthesia (epidural/spinal anesthesia) or spinal puncture is employed, patients who are anticoagulated or scheduled to be anticoagulated with low molecular weight heparins (LMWHs) or heparinoids for prevention of thromboembolic complications are at risk of developing an epidural or spinal hematoma, which can result in long-term or permanent paralysis. 

CNS- During and immediately following spinal tap, spinal anesthesia, or major surgery, especially of the brain, spinal cord, or eye. 

Concomitant anesthesia - Certain forms of conduction anesthesia, such as spinal anesthesia and some peridural anesthetics, can alter respiration by blocking intercostal nerves. Fentanyl can also alter respiration through other mechanisms. 

The vasoconstrictor actions of epinephrine and norepinephrine have been used to prolong the action of local anesthetics by reducing local blood flow in the region of the injection. Epinephrine has been used as a topical hemostatic agent for the control of local hemorrhage. Norepinephrine is infused intravenously to combat systemic hypotension during spinal anesthesia or other hypotensive conditions in which peripheral resistance is low, but it is not used to combat the hypotension due to most types of shock. In shock, marked sympathetic activity is already present, and perfusion of organs, such as the kidneys, may be jeopardized by norepinephrine administration. 

The clinical uses of these drugs are associated with their potent vasoconstrictor action. They are used to restore or maintain blood pressure during spinal anesthesia and certain other hypotensive states. The reflex bradycardia induced by their rapid intravenous injection has been used to terminate attacks of paroxysmal atrial tachycardia. Phenylephrine is commonly used as a nasal decongestant, although occasional nasal mucosal... 

Lumbar epidural anesthesia affects the same area of the body as does spinal anesthesia. As the name implies, the... 

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