McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 2 7 General and local anaesthetic agents

A naesthetics are drugs that are used to cause complete or partial loss of sensation. The anaesthetics can be sub- divided into general and local anaesthetics, depending on their site of action. General anaesthetics are central nervous system (CNS) depressants used to produce loss of pain sensation and consciousness. Local anaesthetics are drugs used to cause loss of pain sensation and feeling in a designated area of the body without the systemic effects associated with severe CNS depression. This chapter discusses various general and local anaesthetics. Box 27.1 highlights information about using anaesthet- ics with various age groups. GENERAL ANAESTHESIA General anaesthesia involves the administration of a combination of several different general anaesthetic agents to achieve the following goals: analgesia , or loss of pain perception; unconsciousness , or loss of CHILDREN Children are at greater risk for complications after anaesthesia—laryngospasm, bronchospasm, aspiration and even death.They require very careful monitoring and support, and the anaesthetist needs to be very skilled at calculating dosage and balance during the procedure. Propofol is widely used for diagnostic tests and short procedures in children older than 3 years of age because of its rapid onset and metabolism and generally smooth recovery. Sevoflurane has a minimal impact on intracranial pressure and allows a very rapid induction and recovery with minimal sympathetic reaction. It is still quite expensive, however, which may limit its use.The dosage of anaesthetics may need to be higher in children, and that factor will be considered by the anaesthetist. Care after general anaesthesia should include support and reassurance; assessment of the child for any skin breakdown related to immobility, and safety precautions until full recovery has occurred. Local anaesthetics are used in children in much the same way that they are used in adults. Bupivacaine does not have established doses for children younger than 12 years of age. Benzocaine should not be used in children younger than 1 year of age. When topically applying a local anaesthetic, it is important to remember that there is greater risk of systemic absorption and toxicity with infants. Tight nappies can act like occlusive dressings and increase systemic absorption. Children need to be cautioned not to bite themselves when receiving dental anaesthesia. ADULTS Adults require a considerable amount of teaching and support when receiving anaesthetics, including what will BOX 27.1 Anaesthetic agents

awareness of one’s surroundings; and amnesia , or ina- bility to recall what took place. Ideally, the drugs are combined to achieve the best effects with the fewest adverse effects. In addition, general anaesthesia also blocks the body reflexes. Blockage of autonomic reflexes prevents involuntary reflex response to body injury that might compromise a person’s cardiac, respiratory, gastrointestinal (GI) and immune status. Blockage of muscle reflexes prevents jerking movements that might interfere with the success of the surgical procedure. Risk factors associated with general anaesthesia Widespread CNS depression, which is not without risks, occurs with general anaesthesia. In addition, all other body systems are affected. Because of the wide systemic effects, people must be evaluated for factors that may increase their risk. These factors include the following: • CNS factors : Underlying neurological disease (e.g. epilepsy, stroke, myasthenia gravis) that presents happen, what they will feel, how it will feel when they recover and the approximate time to recovery. Adults should be monitored closely until fully recovered from general anaesthetics and should be cautioned to prevent injury when receiving local anaesthetics. It is important to remember to reassure and talk to adults who may be aware of their surroundings yet unable to speak. PREGNANCY AND BREASTFEEDING Most of the general anaesthetics are not recommended for use during pregnancy because of the potential risk to the fetus. Short-onset and local anaesthetics are frequently used at delivery. Use of a regional or other local anaesthetic is usually preferred if surgery is needed during pregnancy. During breastfeeding, it is recommended that the mother wait 4 to 6 hours to feed the baby after the anaesthetic is used. OLDER ADULTS Older people are more likely to experience the adverse effects associated with these drugs, including central nervous system, cardiovascular and dermatological effects.Thinner skin and the possibility of decreased perfusion to the skin makes them especially susceptible to skin breakdown during immobility. Because older people often also have renal or hepatic impairment, they are also more likely to have toxic levels of the drug related to changes in metabolism and excretion.The older person should have safety measures in effect, such as siderails, a call bell and assistance to ambulate; special efforts to provide skin care to prevent skin breakdown are especially important with older skin.The older person may require longer monitoring and regular orienting and reassuring. After general anaesthesia, it is very important to promote vigorous deep breathing and coughing to decrease the risk of pneumonia.

Drug therapy across the lifespan