Local anesthesia, pharmacology

Diazepam, lorazepam, and midazolam are used for preanesthetic medication and as adjuvants during surgical procedures performed under local anesthesia. As a result of their sedative, anxiolytic, and amnestic properties, and their ability to control acute agitation, these compounds are considered to be the drugs of choice for premedication. (The basic pharmacology of benzodiazepines is discussed in Chapter 22.) Diazepam and lorazepam are not water-soluble, and their intravenous use necessitates nonaqueous vehicles, which cause pain and local irritation. Midazolam is water-soluble and is the benzodiazepine of choice for parenteral administration. It is important that the drug becomes lipid-soluble at physiologic pH and can readily cross the blood-brain barrier to produce its central effects. 

Local anesthetics are drugs that produce reversible conduction blockage of nerve impulses. Autonomic system blockade followed by sensory anesthesia and skeletal muscle paralysis occur when local anesthetic concentration is increased. The effects of local anesthetics are completely reversible, with no evidence of structural damage to the nerve fibers. Another prominent clinical feature of local anesthesia is that loss of sensation occurs without loss of consciousness. This property makes local anesthetics highly useful for many office procedures and for eye surgery. This chapter considers the pharmacologic properties of anesthetics cmrently used for ophthalmic procedures. 

Liljestrand G. The historical development of local anesthesia in local anesthetics. In Lechat P, ed. International Encyclopedia of Pharmacology and Therapeutics. Oxford Pergamon Press, 1971 1-38. 

Vandam LD. Some aspects of the history of local anesthesia. In Strichartz GR. ed. Local Anesthetics. Handbook of Experimental Pharmacology. Berlin Springer, 1987 81 1-19. 

Local Anesthesia Temporary pharmacological inhibition of nerve impulses to a specific body part, typically used to treat small lacerations or perform minor surgery. 

The useful pharmacological properties of PSTs for medical treatment have been recognized for over three decades, and motivated the development of a variety of patented medical and cosmetic treatments (Table 3.5). They include local injection of PSTs to treat chronic anal fissures [263-267], tension headaches [268], and local anesthesia [269-271]. A major advantage in using site 1 sodium channel blocking toxins is that they lack central nervous system, cardiac, and... 

A large-diameter multihole urethral catheter should be inserted to facilitate saline lavage and evacuation of blood clots. Surgical removal of blood clots under anesthesia may be required if saline lavage is ineffective. Active bleeding from isolated areas may be cauterized with an electrode or laser. In severe cases that are unresponsive to local or systemic pharmacologic intervention,... 

Denson DD and Mazoit JX. Physiology, pharmacology and toxicity of local anesthetics Adult and pediatric considerations. In P Prithvi Raj P (ed.). Clinical Practice of Regional Anesthesia. New York Churchill Livingstone, 1991. 

Pharmacological Profile. The profile of the ideal local anesthetic agent depends largely on the type and length of the surgical procedure for which it is applied. Procedures could include neuraxial (spinal and epidural) anesthesia, nerve and plexus blocks, or field blocks (local infiltration). In general, tine ideal agent should have a short onset of anesthesia and be useful for multiple indications such as infiltration, nerve blocks. 

PURPOSE AND RATIONALE Surface anesthesia is used to anesthetize the cornea and conjunctiva of the eye and the mucous membranes in the mouth. The classical pharmacological test is the blockade of the rabbit corneal reflex as described by Regnier (1923) that has become a standard test method for evaluating local anesthetics (FuBganger and Schaumann 1931 Ther 1953a Quevauviller 1971 Muschaweck et al. 1986). These pharmacological methods are only partially suitable to determine the irritancy potential of local anesthetic on mucus membranes. Luduena et al. (1960) compared the mucus membrane irritancy of mepivacaine and lidocaine by the eye irritation method according to Hoppe (1950) and Draize et al. (1944). 

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. 

---