Surface anaesthesia

III.b.8.1. Skin. Surface anaesthesia of the skin can be produced with help of a cream containing a eutectic mixture of local anaesthetics (EMLA), which is a water/oil emulsion of equal parts of prilocaine and lidocaine with particularly good penetration capacity. EMLA is applied under occlusion, around 40-60 minutes before the planned intervention. This is an effective way of producing anaesthesia before needle punctures and minor, painful, procedures. The method is excellent, particularly in paediatrics, to reduce fear and pain. 

III.b.8.3. Eye. When removing foreign bodies from the eye a short acting surface anaesthesia can be produced by lidocaine 40 mg/ml, oxybuprocaine 4 mg/ml or tetracaine (amethocaine) 5 mg/ml. Welding flash burns or corneal injuries can be treated with cinchocaine cream. 

It is another local anaesthetic with longer action but most toxic. It is used for surface anaesthesia. 

Dose. 5 to 20 mg of amethocaine hydrochloride (0.5% solution) is injected for spinal anaesthesia 0.5 to 2% solutions have been used for surface anaesthesia. 

Use. A 2% solution of butacaine sulphate has been used for surface anaesthesia. 

Surface anaesthesia, as solution, jelly, cream or lozenge. 

It is a potent surface anaesthetic mainly used in ophthalmology and induces no initial irritation. Beeause of its rapid onset of aetion it is useful for most occular procedures that require topical anaesthesia such as tonometry, removal of foreign particles, gonioscopy and various short operative procedures which may involve the conjunctiva and cornea. It has also been reported to be employed frequently as a surface anaesthesia in glaucoma surgery and in cataract operations. 

It is a local anaesthetic formerly used for surface anaesthesia. Its anaesthetie property is fairly comparable to that of cocaine. 

Ckyst. powder. M.p. 100°. Local anaesthetic, particularly for surface anaesthesia. i... 

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-... 

It is a surface anaesthetic used in eye for producing corneal anaesthesia for tonometry and does not cause mydriasis or any corneal damage. 

The induction of unconsciousness may be the result of exposure to excessive concentrations of toxic solvents such as carbon tetrachloride or vinyl chloride, as occasionally occurs in industrial situations (solvent narcosis). Also, volatile and non-volatile anaesthetic drugs such as halothane and thiopental, respectively, cause the same physiological effect. The mechanism(s) underlying anaesthesia are not fully understood, although various theories have been proposed. Many of these have centred on the correlation between certain physicochemical properties and anaesthetic potency. Thus the oil water partition coefficient, the ability to reduce surface tension and the ability to induce the formation of... 

According to one eoneept the decrease in surface tension caused by an anaesthetic is directly related to its potency. Another possible explanation may suggest a relationship between the anaesthetic action and the funetion and strueture of membrane. However, many of these theories converge to a point indieating that the lipid portion of membranes is the site of anaesthesia. 

It is an all-purpose local anaesthetic drug used frequently in surface infiltration, block, caudal and spinal anaesthesia. It is reported to be 10 times more toxic and potent than procaine, whereas its duration of action is twice than that of procaine. 

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. 

Administration usually creates pain, anxiety and phobia, and requires professionally trained staff. Topical anaesthesia (creams, gels, patches or simply cold to numb the area) is usually performed to help to manage the pain and associated fears, as well as to distract the child. There is no taste issue with the parenteral routes but the excipients used must be biodegradable imder the available metabolic processes. This can be a problem in neonates as not all pathways have fully matured. Moreover, formulation composition is critical as some excipients can be toxic. This includes vehicles, preservatives or even the antiseptic used to disinfect the surface of the skin prior to injection (e.g. iodine-containing antiseptic that can be absorbed through the skin). 

Fig. 167. Type A epithelioid cells with much rough surfaced endoplamic reticulum and type B epithelioid cells showing vesicles of different sizes from a Marbagelan -induced (7 days) resorption granuloma (block 171) of a male Sprague-Dawley rat (No. 10). Animal treated for 14 days with intra-gastric application of 15 mg carbocromene per kg body weighty day. Perfused under pentobarbital anaesthesia (30 mg g) from the abdominal aorta with 2.5 % glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.4). Postfixation with 1 % osmium tetroxide in cacodylate buffer. Embedded in Epon 812 and sectioned at 50 nm. Lead citrate and uranyl acetate. Plate 2850...

Fig. 2.1.7. a The metastases from a breast cancer, subcapsular located in the left liver lobe, were treated via an oblique access route with the skin entry point at the epigastrium (former selective internal radiation therapy i.e. SIRT caused the parenchymal irregularities in the right liver lobe where active metastases could no longer be appreciated). Note the gas within the treated lesion and gas bubbles along the electrode s pathway. Extensive capsular anaesthesia caused the soft-tissue swelling between peritoneal wall and hepatic surface, b Due to an insulation defect, a grade 3 burn occurred at the skin entry point, about 5 cm distant from the electrode s tip. The burn was not appreciated until the end of the procedure because the entry point was draped with a swab and the patient did not feel the burn due to local anaesthesia... 

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