Anesthesia enables the painless performance of medical procedures that would cause severe or intolerable pain to an unanesthetized patient. A patient under regional or local anesthesia remains conscious, unless general anaesthesia or sedation is administered at the same time. Central, or neuraxial, blockade administers the anesthetic in the region of the mcgraw hill’s 5 teas practice tests free pdf nervous system itself, suppressing incoming sensation from outside the area of the block.
In preparing for a medical procedure, the health care provider giving anesthesia chooses and determines the doses of one or more drugs to achieve the types and degree of anesthesia characteristics appropriate for the type of procedure and the particular patient. There are both major and minor risks of anesthesia. Patients typically wake within minutes of an anesthetic being terminated and regain their senses within hours. The goal of anesthesia is to achieve the endpoints required for the given surgical procedure with the least risk to the patient.
To achieve the goals of anesthesia, drugs act on different but interconnected parts of the nervous system. Each anesthetic produces amnesia through unique effects on memory formation at variable doses. Consciousness is the higher order process that synthesizes information. Anesthesia is unique, in that it is not a direct means of treatment, rather it allows others to do things that may treat, diagnose, or cure an ailment which would otherwise be painful or complicated. The best anesthetic, therefore is the one with the lowest risk to the patient that still achieves the endpoints required to complete the procedure.
Diagnosing a person’s pre-operative physical status allows the clinician to minimize anesthetic risks. The scale assesses a high-order of risk as the patient’s general health relates to an anesthetic. Aside from the generalities of the patients health assessment, an evaluation of the specific factors as they relate to the surgery also need to be considered for anesthesia. After determining the health of the person undergoing anesthetic and the endpoints that are required to complete the procedure, the type of anesthetic can be selected.
In the early days of anesthesia, anesthetics could reliably achieve the first two, allowing surgeons to perform necessary procedures, but many patients died because the extremes of blood pressure and pulse caused by the surgical insult were ultimately harmful. Each has its own potency which is correlated to its solubility in oil. Inhalational anesthetics are thought to exact their effects on different parts of the central nervous system. The higher the MAC, generally, the less potent the anesthetic.
The ideal anesthetic drug would provide hypnosis, amnesia, analgesia, and muscle relaxation without undesirable changes in blood pressure, pulse or breathing. The drugs used in combination offered a better risk profile to the person under anesthesia and a quicker recovery. A combination of drugs was later shown to result in lower odds of dying in the first 7 days after anesthetic. More recently, several intravenous drugs have been developed which, if desired, allow inhaled general anesthetics to be avoided completely. The purpose of the anesthetic machine is to provide anesthetic gas at a constant pressure, oxygen for breathing and to remove carbon dioxide or other waste anesthetic gases. Since inhalational anaesthetics are flammable, various checklists have been developed to confirm that the machine is ready for use, that the safety features are active and the electrical hazards are removed.
In addition, the operating room environment must be monitored for ambient temperature and humidity, as well as for accumulation of exhaled inhalational anesthetic agents, which might be deleterious to the health of operating room personnel. From the perspective of the person giving the sedation, the patient will appear sleepy, relaxed and forgetful, allowing unpleasant procedures to be more easily completed. There are many types of regional anesthesia either by injecting into the tissue itself, a vein that feeds the area or around a nerve trunk that supplies sensation to the area. The latter are called nerve blocks and are divided into peripheral or central nerve blocks. The effect is almost immediate. The use of ultrasound may reduce complication rates and improve quality, performance time, and time to onset of blocks.