Anethesia.docx

AL-Warith University Nursing Faculty Pharmachology II // Prepared by Dr. Nassim Samir Ali Saker 2019 Introduction: Aesthesia means loss of sensation with or without loss of consciousness. Anesthetic drugs are given to prevent pain and promote relaxation during surgery, childbirth, some diagnostic te...

AL-Warith University Nursing Faculty Pharmachology II // Prepared by Dr. Nassim Samir Ali Saker 2019 Introduction: Aesthesia means loss of sensation with or without loss of consciousness. Anesthetic drugs are given to prevent pain and promote relaxation during surgery, childbirth, some diagnostic tests, and some treatments. They interrupt the conduction of painful nerve impulses from a site of injury to the brain. The two basic types of anesthesia are general and regional. Group Drugs Ex General Inhalation Anesthetics Isoflurane, Desflurane , Halothane, Nitrous oxide General Intravenous Anesthetics Fentanyl, Ketamine, Propofol, Thiopental sodium Neuromuscular Blocking Agents (Skeletal Muscle Relaxants) Adjunct to general anesthesia Type 1 Succinylcholine used in All types of surgery and brief procedures, such as endoscopy and endotracheal intubation. No antidote Type 2 Atracurium: intermediate acting Type 2 Pancuronium: long acting: Adjunct to general anesthesia; recommended only for procedures expected to last 90 minutes or longer Neostigmine is antidote Local Anesthetics Benzocaine: Topical anesthesia of skin and mucous membrane to relieve pain and itching of sunburn, other minor burns and wounds, skin abrasions, earache, hemorrhoids, sore throat, Bupivacaine Regional anesthesia by infiltration, nerve block, and epidural anesthesia during childbirth. It is not used for spinal anesthesia. Lidocaine Topical anesthesia and regional anesthesia by local infiltration, nerve block, spinal, and epidural anesthesia Intravenously to prevent or treat cardiac dysrhythmias General anesthesia is a state of profound central nervous system (CNS) depression, during which there is complete loss of sensation, consciousness, pain perception, and memory. It has three components: hypnosis, analgesia, and muscle relaxation. Several different drugs are usually combined to produce desired levels of these components without excessive CNS depression. General anesthesia is usually induced with a fast-acting drug (eg, propofol or thiopental) given intravenously and is maintained with a gas mixture of an anesthetic agent and oxygen given by inhalation. The intravenous (IV) agent produces rapid loss of consciousness and provides a pleasant induction and recovery. Its rapid onset of action is attributed to rapid circulation to the brain and accumulation in the neuronal tissue of the cerebral cortex. An anesthetic barbiturate or Propofol may be used alone for anesthesia during brief diagnostic tests or surgical procedures. Preanesthetic Medications Principles for using preanesthetic drugs (antianxiety agents, anticholinergics, opioid analgesics) are the same when these drugs are given before surgery as at other times. The choice of a particular drug depends on several factors. Some client-related factors include age; the specific procedure to be performed and its anticipated duration; the client’s physical condition, including severity of illness, presence of chronic diseases, and any other drugs being given; and the client’s mental status. Severe anxiety, for example, may be a contraindication to regional anesthesia, and the client may require larger doses of preanesthetic sedative-type medication. Anticholinergics Anticholinergic drugs are given to prevent vagal effects associated with general anesthesia and surgery (eg, bradycardia, hypotension). Vagal stimulation occurs with some inhalation anesthetics; with succinylcholine, a muscle relaxant; and with surgical procedures in which there is manipulation of the pharynx, trachea, peritoneum, stomach, intestine, or other viscera and procedures in which pressure is exerted on the eyeball. Useful drugs are atropine Neuromuscular Blocking Agents Neuromuscular blocking agents cause muscle relaxation, the third component of general anesthesia, and allow the use of smaller amounts of anesthetic agent. Artificial ventilation is necessary because these drugs paralyze muscles of respiration as well as other skeletal muscles. The drugs do not cause sedation; therefore, unless the recipients are unconscious, they can see and hear environmental activities and conversations. Note: Muscle paralysis is preceded by muscle spasms, which may damage muscles. Injury to muscle cells may cause postoperative muscle pain and release potassium into the circulation. If hyperkalemia develops, it is usually mild and insignificant but may cause cardiac dysrhythmias or even cardiac arrest in some situations. II- Regional and Local Anesthesia Regional or local anesthesia is usually safer than general anesthesia because it produces fewer systemic effects. For example, spinal anesthesia is often the anesthesia of choice for surgery involving the lower abdomen and lower extremities, especially in people who are elderly or have chronic lung disease. A major advantage of spinal anesthesia is that it causes less CNS and respiratory depression. Except with IV lidocaine for cardiac dysrhythmias, local anesthetic solutions must not be injected into blood vessels because of the high risk of serious adverse reactions involving the cardiovascular system and CNS. Epinephrine is often added to local anesthetic solutions to prolong anesthetic effects. Special considerations: Halothane has been commonly used. It causes bronchodilation and does not irritate respiratory mucosa, features that make it especially useful for children with asthma, cystic fibrosis, or other bronchospastic disorders. However, the drug dilates blood vessels in the brain and increases intracranial pressure, so it may not be indicated in clients who already have increased intracranial pressure or mass lesions. Propofol is approved for use in children 3 years of age and older. It has a rapid onset; a rapid metabolism rate; with little mental confusion, sedation, or nausea. It also decreases cerebral blood flow and intracranial pressure, making it useful in neurosurgery. Most inhalation general anesthetic agents can be used in clients with renal impairment because they are eliminated mainly by exhalation from the lungs. Propofol is an anesthetic used in subanesthetic doses for short-term sedation of clients who are intubated and mechanically ventilated.