Anesthetics disadvantages

An anesthetic gas, cyclopropane has a rapid onset of action and may be used for induction and maintenance of anesthesia Skeletal muscle relaxation is produced with full anesthetic doses. Cyclopropane is supplied in orange cylinders. Disadvantages of cyclopropane are difficulty in detecting the planes of anesthesia, occasional laryngospasm, cardiac arrhythmias, and postanesthesia nausea, vomiting, and headache Cyclopropane and oxygen mixtures are explosive, which limits the use of this gas anesthetic. 

Ethylene is an anesthetic gas with a rapid onset of action and a rapid recovery from its anesthetic effects. It provides adequate analgesia but has poor muscle-relaxant properties. The advantages of ethylene include minimal bronchospasm, laryngospasm, and postanesthesia vomiting. A disadvantage of ethylene is hypoxia. This gas is supplied in red cylinders. Mixtures of ethylene and oxygen are flammable and explosive. 

Methoxyflurane is an extremely powerful inhalation anesthetic that is an excellent skeletal muscle relaxant. However, its use is somewhat limited by its relatively high solubility, which causes the patient to make a slow transition back into consciousness. Another disadvantage of methoxyflurane is that fluorine ions are the product of its biotransformation, which may lead to the development of renal failure. Therefore, it is recommended to use methoxyflurane for anesthesia during interventions of no more than 2 h. A very common synonym for methoxyflurane is penthrane. 

Nitrous oxide is the only inhalation anesthetic that is a gas. It is chemically inert. Nitrous oxide has little effect on overall cardiovascular function. Disadvantages are that it has no muscle relaxing effect and that it cannot be used on its own because of high Minimal Alveolar Concentration values needed for adequate anesthesia. During recovery there is a risk for hypoxia and anesthesia should be slowly tapered off to prevent this event. 

HRT implants are another means of achieving constant hormone levels while removing the responsibility of the patient to take or apply a daily dose of HRT. Implants are inserted in the fat under the skin (usually in the lower abdomen) by a simple surgical procedure involving a local anesthetic and a few stitches. However, this type of HRT has the major disadvantage that if the therapy does not suit then it is almost impossible to remove the implants. 

This involves considerable art, which must be learned in the clinic. It falls into two divisions (1) surface application to the mucous membranes, especially of the eye, nose, throat, and urethra and (2) injections about nerves, in different parts of their course and distribution, from their spinal roots to their ultimate fibrils. The advantages and disadvantages in comparison with general anesthesia and the selection of the local anesthetic agent also depend on clinical discrimination. Nervous, fearful, and excitable patients often suffer severely from apprehension, which also disposes toward accidents. They may be at least somewhat quieted by sedatives, morphine (0.015 g hypodermically) half an hour before the operation, or by barbiturates. The latter also tend to prevent convulsions. 

The rapid-acting barbiturates, such as methohexital (Brevital), are used as intravenous anesthetics/induction agents. Advantages are rapid anesthesia and short duration of action. A disadvantage is respiratory suppression with higher doses. 

Therapeutic disadvantages and advantages of some anesthetic agents. 

Some therapeutic advantages and disadvantages of the anesthetic agents are summarized in Figure 11.9. 

Clinically used local anesthetics are either esters or amides. Even drugs containing a methylene bridge, such as chlorpromazine (p.233) or imipramine (p.229) would exert a local anesthetic effect with appropriate application. Ester-type local anesthetics are subject to inactivation by tissue esterases. This is advantageous because of the diminished danger of systemic intoxication. On the other hand, the high rate of bioinactivation and, therefore, shortened duration of action is a disadvantage. 

Use of a solution of benoxinate-sodium fluorescein (Fluress) or proparacaine-sodium fluorescein allows simultaneous application of the required anesthetic and sodium fluorescein dye. This method increases the efficiency of the procedure by eliminating the need for separate applications of the anesthetic and dye, but it has the disadvantages of irritation from the benoxinate and excessive instillation of dye. On occasion, a few seconds must elapse to allow tears and excess dye to dissipate before accurate tonometry can be performed. Notably, the differences in the results of tonometry using either benoxinate or proparacaine are not clinically significant. 

When inhaled it produces unconsciousness (loss of awareness of the environment) and anesthesia (loss of feeling and sensation). It is a good anesthetic agent, except for one disadvantage its mixtures with air may explode if ignited by an electrostatic spark and thus cause the death of the patient. Accidents of this sort are, however, rare. 

Disadvantage Local anesthetic injection itself is associated with pain and burning sensation... 

The advantage of infiltration anesthesia and other regional anesthetic techniques is that it can provide satisfactory anesthesia without disrupting normal bodily functions. The chief disadvantage of infiltration anesthesia is that relatively large amounts of drug must be used to anesthetize relatively small areas. 

Fentanyl [437-38-7] (Subhmaze, Leptanal), C22H2gN20, (9) has been extensively used since its introduction into clinical practice in the 1960s (119). Because of its potency, which is 50—100 times that of morphine, a rapid onset of action and a short duration, its use as an iv anesthetic is widespread The short duration results from redistribution from the brain to other tissues, rather than elimination. It does, however, have the usual opiate disadvantages respiratory depression, chest wall rigidity, nausea, and bradycardia. Fentanyl has an extremely wide therapeutic ratio. The size of the dose influences its duration of action which, after iv administration, may last from approximately 30 min to 2 to 3 h (120,121). In cardiac surgery fentanji is administered in very laige doses to produce profound analgesia and suppress cardiovascular reflex responses. This technique is particulady useful for patients with compromised circulation where any increase in cardiac demand could precipitate myocardial ischemia (122). 

Local anesthetic activity Local anesthetic activity ( membrane stabilizing activity ) is a disadvantage when beta-blockers are used topically in the eye because it decreases protective reflexes and increases the risk of corneal ulceration. Local anesthetic effects are absent from timolol and several other beta-blockers. 

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