Anesthesia means a temporary condition induced to make a patient insensitive to pain during an operation. Technically, however, it has a broader meaning that denotes loss or decrease in any feeling or sensation from any cause. In this sense, anesthesia may be temporary or chronic, and may be the result of injury or disease of a sense organ, of a sensory nerve, or of a nerve center in the brain.
Thus, tactile anesthesia is loss of the sense of touch; a person suffering from thermal anesthesia cannot feel heat or cold; while one with facial anesthesia has no feeling in the parts of the face, ear, palate, and tongue supplied by the facial nerve.
Anesthesia is essential for surgical procedures without pain and releases physiological reflexes in the body. Anesthesia must be distinguished from analgesia , which means pain relief; either partially or completely, with or without blocking of other sensory qualities.
Various drugs and techniques have been developed to induce anesthesia for surgery The drugs used are called anesthetics. Those that affect the central nervous system are called general anesthetics. Those that have a direct action on sensory nerves or nerve tracts of a limited area are called local anesthetics.
In general anesthesia, which is the state produced by general anesthetics, the patient becomes unconscious and loses feeling in all parts of the body. This state is produced by an inhaled anesthetic, such as Ether. Nttrovs Oxide. Ethylene, Cyclopropane, and others. Such anesthetics arc usually mixed with oxygen to prevent asphyxia. Helium is often added to the mixture.
Stages of General Anesthesia
Four stages of general anesthesia are recognized. In the first, or analgesic stage, the patient loses the sense of pain, but is still conscious and is sensitive to touch. This is followed by a period of excitement or delirium, during which the patient usually dreams. In most cases, the last sense to be lost is the sense of hearing. The third stage is called surgical anesthesia; during this, the patient sleeps quietly without dreams and is insensitive to stimuli that would normally produce acute pain. In the fourth stage, the respiratory center in the medulla becomes paralyzed, so that the patient stops breathing. Thu stage provides a means of bringing painless death to pets and injured animals.
Types of Anesthesia
In local anesthesia, which is the state produced by anesthetics that act directly on sensory nerves, the patient remains conscious but loses all sense of feeling in a part of the body. This, too, may be accomplished in several ways. In block anesthesia, also called nerve blocking, the anesthetic, such as procaine, is injected into or near the nerve trunk supplying the part. For field block, injections are made in such a way that the part is completely surrounded by desensitized (ancsthetized) tissue, which blocks the transmission of nerve impulses.
In infiltration anesthesia, the anesthetic is injected just under the skin covering the part. Local anesthetics are sometimes applied directly to a mucous membrane, as Cocaink in operations on the eye. Another technique, called spinal anesthesia, involves injections into the spinal cord. When the injection is made into the caudal or sacral canal it is called caudal anesthesia.
For continuous caudal anesthesia, the needle is left in place so that the drug can be given in repeated doses Also called continuous caudal analgesia, this b sometimes used in childbirth. Many drugs useful as local anesthetics have undesirable effects when rapidly absorbed into the general circulation. I’o aid in confining them to the urea immediately around the injection, and to minimize bleeding, epinephrine (Adrenalin*.) is often added. Local anesthesia may also be produced by thorough chilling of the part Called refrigeration anesthesia, this has been found useful for certain difficult amputations found for certain difficult amputation*.
Mixed or balanced anesthesia is used In such a case, the patient may first be given in injection of Morphine and Atrqpim to induce tranquility. It may be followed after a short time by an enema. This produces a state called basal anesthesia, in which the patient goes into such a deep sleep that only a small amount of an inhalation anesthetic u needed to bring on surgical anesthesia.
For this he may be given a mixture of cyclopropane and Oxygen bubbled through ether. Anesthetists (experts who administer anesthesia] are trained to judge from the patient’s condition and the nature of the operation what drugs are best suited to his particular needs. No one drug or technique can be said to be best for .ill cases. Each is dangerous if misused, but each has characteristics that may make it safest in a given situation.
Anesthesia, effects and side effects
The choice of anesthesia method is done in each case by the operator (surgeon) and anesthetically based on the type of procedure, the patient’s general health and the patient’s own wishes. Local anesthesia is usually chosen for more limited and superficial interventions. Large doses of local anesthetic can cause severe side effects (cramps, heart rhythm disturbance) if they get swiftly into the bloodstream; Therefore there are limitations related to quantity that can be used.
Regional anesthesia can be used in conjunction with the eye, the extremities and the lower part of the abdominal wall and the step. In spinal or epidural anesthesia, patients may experience blood pressure and nausea when the anesthesia expands the blood vessels in the legs. Rarely, small rifles in the sack around the spinal fluid can cause transient headache. Common to all anesthetic requiring injection via needles is that these rarely occasionally give rise to nerve damage, either by direct needle injury, high tissue pressure after injection, or accidental injection of substances that can damage the nerve.
Unconsciousness in general anesthesia means that blood pressure drops and breathing capacity decreases or expires, so breathing apparatus ( respirator ) often needs to be used . Even though modern anesthetics go out quickly and provide quick awakening at the end of surgery, patients will feel tired and ever drunk just after the anesthesia has ended. Nausea was previously a frequent complication, but is now less common. The surgery that has been performed will most often cause pain afterwards, so the use of effective painkillers and methods is important to get in place before and during the awakening.