Local anesthetics refer to drugs for local anesthesia, which act around local nerve endings and can temporarily disappear local pain and other sensations when conscious. Local anesthetics can effectively temporarily and completely block the patient's nerve conduction, so that the patient loses local consciousness, and the nerve function can be completely restored after anesthesia without causing damage to the tissue. Local anesthetics are composed of three parts: aromatic ring, amine group and intermediate chain in chemical structure. Procaine and tetracaine are both esters. Topical anesthesia is to apply a penetrating local anesthetic to the mucosal surface as needed to anesthetize the submucosal nerve endings. Tetracaine, also known as dicaine, has a chemical structure similar to that of procaine. It is an ester-based local anesthetic. Its advantage lies in its rapid action, which is effective in 1 to 3 minutes, the duration of action is 2 to 3 hours, and the intensity of anesthesia is Procaine is 10 times more toxic and 10-12 times more toxic. Because of its strong toxicity, it is generally not used for infiltration anesthesia.
Local anesthetics have a good blocking effect on the local periph
eral nerves, and can also increase the threshold potential of the patient’s nerves, and have a good inhibitory effect on the rising speed of action potential depolarization, so that the refractory period of the action potential is prolonged, and the dose is too high. At large, nerve cells can lose conduction and excitement. Local anesthetics have lipophilic properties. They enter nerve cells in a non-dissociated form, while their intracellular effects are in a dissociated form. They can bind to specific sites of sodium ions, thereby removing sodium ions. Blocked. Therefore, the lipophilicity and dissociation effects of local anesthetics are very important, and they are transformed into charged cations after entering the nerve through dissociation.
It can play its blocking role. Different local anesthetics have different ratios of dissociation and non-dissociation. Procaine hydrochloride is 2.5%, and tetracaine is 25%. However, the toxic reaction caused by tetracaine should not be underestimated. When the dose or concentration of anesthetic is too high, or when the drug is injected into the blood vessel, it will cause systemic adverse reactions. Commonly, the central nervous system and cardiovascular system produce toxicity.
Initially after the toxic effect, patients will have neurological manifestations such as dizziness, panic, talk, tremor, and anxiety. In severe cases, convulsions and confusion will occur. Tetracaine can obviously cause euphoria and a certain degree of emotional and behavioral effects. For the cardiovascular system, local anesthetics have a membrane stabilizing effect on myocardial cells. After the myocardium absorbs local anesthetics, it can inhibit the excitability of the myocardium, weaken its myocardial contractility, slow down the conduction, and prolong the refractory period. When applying tetracaine, you should master the drug concentration and the allowable amount at a time, and use the method of divided small-dose injections.