The use of anesthesia to prevent pain during surgery began in the United States in the 1800s. Surgeons turned to the nurses with whom they worked to administer the anesthetic. Anesthesia is now a recognized specialty of nursing and medicine.
Three different types of anesthesia are provided for surgical and diagnostic procedures: sedation, regional anesthesia, and general anesthesia.
Sedative drugs depress the central nervous system, causing a decrease in awareness and reducing anxiety. Some sedative drugs also cause amnesia. Sedation is most often administered prior to surgery to relieve anxiety, during unpleasant diagnostic procedures, or during regional anesthesia and surgery. Most people do not easily accept the idea of being awake during surgery. Sedation allows patients to feel as if they are asleep during a regional or local anesthetic and often prevents memory of the surgical experience.
The type and amount of sedation administered are based on the procedure being performed and the patient's physical condition, weight, and level of anxiety. Sedation necessitates close observation of the patient. Sedation and general anesthesia exist on a continuum. At some point, as more medication is administered, sedation becomes general anesthesia. Oversedation results in respiratory depression. All but the lightest sedation should be administered by an anesthetist or other health care provider skilled and experienced in airway management and the assessment of oxygenation and breathing.
Local anesthetic drugs temporarily disable the function of nerves. Regional anesthesia can be used to numb a small area of skin, a single nerve, or a large region of the body. Regional anesthesia can be used for minor procedures as well as some types of major surgery. Local anesthesia is commonly used around a wound edge before stitches are sewn in. A common nerve block is used by dentists to numb a large area of the mouth with a single injection. Epidural blocks are commonly used to anesthetize a large area of the body during labor pains or cesarean section.
Regional blocks wear off gradually; sensations such as touch, pressure, and pain, and the ability to use muscles in the anesthetized area, return to normal at different speeds.
The individual will usually experience a pins-and-needles feeling before normal sensation completely returns.
General anesthetics temporarily depress brain function and result in a loss of consciousness. This produces insensibility to pain, prevents awareness, and relaxes or paralyzes voluntary muscles. A general anesthetic diminishes the brain's ability to regulate essential functions like breathing and body temperature. In addition to administering an anesthetic, the anesthetist monitors, supports, and, when necessary, controls these vital functions.
Although the initiation of general anesthesia is quick, it is a time when many critical tasks are performed. For adults, anesthetic drugs are usually injected into an intravenous line to put the patient to sleep, and then anesthetic vapor is inhaled through a breathing circuit. For infants and young children, the anesthetic vapor is often inhaled first and an intravenous line started after the child is asleep.
Many surgeries benefit from relaxation of skeletal muscles. In these cases drugs are administered that paralyze voluntary muscles. Such drugs make it impossible for patients to breathe on their own, but anesthetists are very skilled at ventilating patients. Paralysis is eliminated prior to the end of anesthesia either by allowing paralyzing drugs to wear off or by administering other drugs to counter their effects.
Awaking from general anesthesia occurs when anesthetic drugs are allowed to wear off. Anesthetists carefully control the drugs given in order that the patient emerges from general anesthesia at but not before the desired time. This takes experience and a detailed understanding of the drugs used and the patient's response to those drugs. If the patient must be left on a ventilator with a breathing tube in place, the anesthetist may take the patient to an intensive care unit asleep rather than awaking him or her from the anesthetic.
Recovery from general anesthesia continues after the patient awakens. Inhaled anesthetics are eliminated through the lungs. Small amounts are exhaled for amounts of time ranging from hours to days. Patients commonly remain amnestic for minutes or hours after awaking. Some difficulty with complex mental tasks may last several days.
In addition to administering anesthesia, anesthetists provide emergency airway management and establish circulatory access with arterial and intravenous lines. Anesthetists are skilled at placing and using artificial airway devices and ventilating patients. When patients outside the operating suite experience life-threatening breathing problems, anesthetists are often summoned to establish an airway.
Pain management is provided by physicians, surgeons, and anesthetists. Patient-controlled analgesia (PCA) allows patients to push a button that injects pain medicine into their intravenous line. The PCA pump is programmed to deliver a set dose when the patient pushes the button. A preset time interval must pass between each dose. Once the total dose given for an hour reaches the programmed limit, the PCA pump will not give any more until the next hour.
PCA allows the patient control over when pain medicine is received, which helps reduce anxiety. PCA also results in better pain relief than intermittent injections.
When a regional block is produced, whether it completely eliminates sensation and muscle tone from an area (anesthetic) or simply reduces pain sensation in that area (analgesia) depends upon the drug(s) used, as well as dose and strength. Regional anesthesia can be used for pain relief after surgery in many cases. Local anesthetics, either alone or combined with opioids, are commonly used for pain relief. When regional pain blocks affect the legs, patients are usually confined to bed. Even dilute concentrations of local anesthetic affect muscle strength enough to increase the risk of falling.
When opioids are added to a spinal or epidural anesthetic they provide pain relief that persists after the anesthetic block has stopped working. Some opioids provide hours of postoperative pain relief when used in this way. Regional analgesia often provides better pain relief than injections or PCA.
Michael A. Fiedler Samford University
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