Anesthesia recovery

Narcotic or antianxiety drug—to decrease anxiety and apprehension immediately before surgery. The patient who is calm and relaxed can be anesthetized more quickly, usually requires a smaller dose of an induction drug, may require less anesthesia during surgery, and may have a smoother anesthesia recovery period (awakening from anesthesia). 

Inhalation of concentrations in the range of 5000-20,OOOppm have been used to produce light anesthesia. Recovery from unconsciousness is usually uneventful, but ventricular arrhythmias and death from cardiac arrest have occurred rarely. Exposure of volunteers to 500-1000 ppm has resulted in some symptoms of CNS disturbance such as dizziness, lightheadedness, lethargy, and impairment in visual-motor response tests. In general, no significant signs of toxicity or impaired performance have been noted in subjects acutely exposed to 300 ppm or less. 

Inhaled anesthetics that are relatively insoluble in blood (low blood gas partition coefficient) and brain are eliminated at faster rates than more soluble anesthetics. The washout of nitrous oxide, desflurane, and sevoflurane occurs at a rapid rate, which leads to a more rapid recovery from their anesthetic effects compared to halothane and isoflurane. Halothane is approximately twice as soluble in brain tissue and five times more soluble in blood than nitrous oxide and desflurane its elimination therefore takes place more slowly, and recovery from halothane anesthesia is predictably less rapid. The duration of exposure to the anesthetic can also have a marked effect on the time of recovery, especially in the case of more soluble anesthetics. Accumulation of anesthetics in tissues, including muscle, skin, and fat, increases with continuous inhalation (especially in obese patients), and blood tension may decline slowly during recovery as the anesthetic is gradually eliminated from these tissues. Thus, if exposure to the anesthetic is short, recovery may be rapid even with the more soluble agents. However, after prolonged anesthesia, recovery may be delayed even with anesthetics of moderate solubility such as isoflurane. 

Anesthesia can be divided into three stages induction, maintenance, and recovery. Induction is defined as the period of time from onset of administration of the anesthetic to the development of effective surgical anesthesia in the patient. Maintenance provides a sustained surgical anesthesia. Recovery is the time from discontinuation of administration of anesthesia until consciousness is regained. Induction of anesthesia depends on how fast effective concentrations of the anesthetic drug reach the brain recovery is the reverse of induction and depends on how fast the anesthetic drug is removed from the brain. 

The agent should be odorless, nonflammable at concentrations which are likely to be used in the operating room, and stable both on storage and to soda lime, which is used as the CO2 absorber in the anesthetic circuit. Induction of, and recovery from, anesthesia should be rapid, and minimal side effects... 

Historical Inhalation Agents. Diethyl ether produces excellent surgical anesthesia, but it is flammable (see Ethers). Chloroform is a nonflammable, sweet smelling, colorless Hquid which provides analgesia at nonanesthetic doses and can provide potent anesthesia at 1% (see Chlorocarbons AND CHLOROHYDROCARBONs). However, a metabohte causes hepatic cell necrosis. Tdlene, a nonflammable colorless Hquid, has a slower onset and recovery and a higher toxicity and chemical reactivity than desirable. Cyclopropane is a colorless gas which has rapid induction (2 —3 min) and recovery characteristics and analgesia is obtained in the range of 3—5% with adequate skeletal muscle relaxation (see Hydrocarbons). The use of cyclopropane has ceased, however, because of its flammabiHty and marked predisposition to cause arrhythmias. 

Sevoflurane. Sevoflurane, l,l,l,3,3,3-hexafluoro-2-propyl fluromethyl ether [28523-86-6] is nonpungent, suggesting use in induction of anesthesia. The blood/gas partition coefficient is less than other marketed products (Table 1) yet similar to nitrous oxide, suggesting fast onset and recovery. In animal studies, recovery was faster for sevoflurane than for isoflurane, enflurane, or halothane (76). Sevoflurane is stable to light, oxygen, and metals (28). However, the agent does degrade in soda lime (77). 

Methohexital [18652-93-2] (Brevital), C 4H gN202, (2) is a barbiturate iv anesthetic iaduction agent that has a slightly faster onset than thiopentone and less accumulation. The recovery from anesthesia is also slightly faster and better. However, iaduction is associated with an iacreased iacidence of excitatory phenomena. Methohexital also causes respiratory and cardiovascular depression and is unstable ia solution, necessitating reconstitution before use (99). 

Clinical evaluation is underway to test transvenous electrodes. Transvenous leads permit pacemakers to be implanted under local anesthesia while the patient is awake, greatly reducing recovery time and risk. As of 1996, the generation of implantable defibrillators requires a thoracotomy, a surgical opening of the chest, in order to attach electrodes to the outside of the heart. Transvenous electrodes would allow cardiologists to perform pacemaker procedures without a hospital or the use of general anesthesia. 

Another injectable anesthetic widely used in feline and primate practice is ketamine hydrochloride [1867-66-9]. Ketamine, a derivative of phencychdine, can be chemically classified as a cyclohexamine and pharmacologically as a dissociative agent. Analgesia is produced along with a state that resembles anesthesia but in humans has been associated with hallucinations and confusion. For these reasons, ketamine is often combined with a tranquilizer. The product is safe when used in accordance with label directions, but the recovery period may be as long as 12—24 h. 

Anesthetics. Ethyl amiaobenzoate [94-09-7] (benzocaiae), C2H22NO2, is the only anesthetic candidate that might allow spawned-out broodstock carcasses to be used for pet or human food. Studies are still required to determine which residues remain ia the carcasses (9). Electronarcosis is an alternative to chemical anesthesia that uses varying electrical frequencies to rapidly anesthetize fishes and allow gentie recovery. Electronarcosis has been used effectively on tilapia (Oreochromis sp.) and the common carp Cyprinus carpid) and the technique is being tested with other fishes (23,24). 

These drug have a rapid onset and a short duration of action. They depress the central nervous system (CNS) to produce hypnosis and anesthesia but do not produce analgesia. Recovery after a small dose is rapid. 

Enflurane (Ethrane) is a volatile liquid anesthetic that is delivered by inhalation. Induction and recovery from anesthesia are rapid. Muscle relaxation for abdominal surgery is adequate, but greater relaxation may be necessary and may require the use of a skeletal muscle relaxant. Enflurane may produce mild stimulation of respiratory and bronchial secretions when used alone Hypotension may occur when anesthesia deepens. 

Halothane (Fluothane) is a volatile liquid given by inhalation for induction and maintenance of anesthesia Induction and recovery from anesthesia are rapid, and the depth of anesthesia can be rapidly altered. Halothane does not irritate the respiratory tract, and an increase in tracheobronchial secretions usually does not occur. Halothane produces moderate muscle relaxation, but skeletal muscle relaxants may be used in certain types of surgeries. This anesthetic may be given with a mixture of nitrous oxide and oxygen. 

Discuss the most important responsibilities of the nurse in the recovery room after a patient has undergone general anesthesia. 

Ketamine has analgesic activity that persists beyond the period of unconsciousness up to 1 h after injection. On regaining consciousness, the patient may experience a disconnection between outside reality and inner mental state (dissociative anesthesia). Frequently there is memory loss for the duration of the recovery period however, adults in particular complain about dis-Ltillmann, Color Atlas of Pharmacology... 

Pain - For analgesic action of short duration during anesthesia (premediaction, induction, maintenance) and in the immediate postoperative period (recovery room) as needed. 

Concomitant narcotic administration - The respiratory depressant effect of fentanyl may persist longer than the analgesic effect. Consider the total dose of all opioid analgesics used before ordering narcotic analgesics during recovery from anesthesia. Use opioids in reduced doses initially, %to 1/3 those usually recommended. 

Scopolamine inhibits excessive motility and hypertonus of the Gl tract in irritable colon syndrome, mild dysentery, diverticulitis, pylorospasm, and cardiospasm. Transdermal patch Prevention of nausea and vomiting associated with motion sickness and recovery from anesthesia and surgery in adults. 

Usually various anesthetic agents are combined to increase efficacy and at the same time decrease toxicity and shorten the time to recovery. For example induction of anesthesia is obtained with an intravenous agent with a rapid onset of action like thiopentone and then anesthesia is maintained with a nitrous oxide/oxygen mixture in combination with halothane or a comparable volatile anesthetic. 

Injectable anesthetics act faster and are therefore best suited for induction of anesthesia and for short operative procedures. However recovery from injectable anesthetics is generally slower than with inhalation anesthetics. The high blood flow to the brain leads to rapid delivery of the anesthetics to their site... 

Propofol can be used for induction as well as maintenance of anesthesia. It is very lipophilic and induction of anesthesia takes place within 30 seconds. After a single dose the patient awakes in approximately 5 minutes and after anesthesia by continuous intravenous administration of longer duration recovery may take 10-15 minutes. It can be used in combination with the usual range of premedications, analgesics, muscle relaxants and inhalation anesthetic agents. 

Nitrous oxide is the only inhalation anesthetic that is a gas. It is chemically inert. Nitrous oxide has little effect on overall cardiovascular function. Disadvantages are that it has no muscle relaxing effect and that it cannot be used on its own because of high Minimal Alveolar Concentration values needed for adequate anesthesia. During recovery there is a risk for hypoxia and anesthesia should be slowly tapered off to prevent this event. 

Propofol (Diprivan) is rapidly acting, has a short recovery time, and possesses antiemetic properties. A rapid onset of anesthesia (50 seconds) is achieved, and if no other drug is administered, recovery will take place in 4 to 8 minutes. The recovery is attributed to redistribution of the drug and rapid metabolism to glucuronide and sulfate conjugates by the liver and extrahepatic tissues, such as intestine and kidney. 

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