Pharmacology for Nurses: A Pathophysiologic Approach Adams Holland Urban Fourth Edition

Transcription

1 Pharmacology for Nurses: A Pathophysiologic Approach Adams Holland Urban Fourth Edition

2 Pearson Education Limited Edinburgh Gate Harlow Essex M20 2JE England and Associated ompanies throughout the world Visit us on the World Wide Web at: Pearson Education Limited 2014 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a licence permitting restricted copying in the United Kingdom issued by the opyright Licensing Agency Ltd, Saffron House, 6 10 Kirby Street, London E1N 8TS. All trademarks used herein are the property of their respective owners. The use of any trademark in this text does not vest in the author or publisher any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of this book by such owners. ISBN 10: ISBN 10: ISBN 13: ISBN 13: British Library ataloguing-in-publication Data A catalogue record for this book is available from the British Library Printed in the United States of America

3 PharmFacts LiFesPan considerations: Geriatric Anesthesia and Anesthetics ognitive Dysfunction After Surgery More than 20 million people receive general anesthetics each year in the United States. About half of all general anesthetics are administered by a nurse anesthetist. The first medical applications of anesthetics were in 1842, using ether, and in 1846, using nitrous oxide. Herbal products may interact with anesthetics; St. John s wort may intensify or prolong the effects of some opioids and anesthetics. epinephrine to lidocaine (Xylocaine), for example, increases the duration of its local anesthetic effect from 20 minutes to as long as 60 minutes. This is important for surgical or dental procedures that take longer than 20 minutes; otherwise, a second injection of the anesthetic would be necessary. Sodium hydroxide is sometimes added to anesthetic solutions to increase the effectiveness of the anesthetic in regions that have extensive local infection or abscesses. Bacteria tend to acidify an infected site, and local anesthetics are less effective in this type of environment. Adding alkaline substances such as sodium hydroxide or sodium bicarbonate neutralizes the region and creates a more favorable environment for the anesthetic. 3 lassification of Local Anesthetics Local anesthetics are classified by their chemical structures; the two major classes are amides and esters ( Table 2). A small number of miscellaneous agents are neither amides TAblE 2 Postoperative cognitive dysfunction has been noted after cardiac as well as other surgeries. Periods of confusion and declines in cognitive skills such as word recall and memory impairment may occur, although not always long lasting. In a study across several age groups, it was noted that the older adult, age 60 years or older, had significantly higher rates of postoperative cognitive dysfunction than did middle-age (40 59 years) or younger (18 39 years) adults. It was also noted that the mortality rate was higher at 3 months and at 1 year postoperatively for patients with such cognitive dysfunction, although no conclusive link was found (Monk et al., 2008). Nurses should observe for any period of cognitive dysfunction such as delirium, confusion, or memory impairment, even if transitory, in postoperative patients and refer them to their health care provider for appropriate monitoring beyond the immediate postoperative period. nor esters. As illustrated in Figure 2, the terms ester and amide refer to types of chemical linkages found within the anesthetic molecules. Esters ocaine was the first local anesthetic widely used for medical procedures. ocaine is a natural ester, found in the leaves of the plant Erythroxylon coca, native to the Andes Mountains of Peru. As late as the 1880s, cocaine was routinely used for eye surgery, nerve blocks, and spinal anesthesia. Although still available for local anesthesia, cocaine is a Schedule II drug and rarely used therapeutically in the United States. Another ester, procaine (Novocain), was the drug of choice for dental procedures from the mid-1900s until the 1960s, Selected Local Anesthetics hemical lassification Drug General Adverse Effects Amides articaine (Septocaine, Zorcaine) Burning, stinging and redness at topical application sites bupivacaine (Marcaine, Sensorcaine) Difficulty breathing or swallowing, respiratory depression and arrest, convulsions, anaphylactoid reaction, burning, contact dermatitis dibucaine (Nupercainal) lidocaine (Anestacon, Dilocaine, Xylocaine, others) mepivacaine (arbocaine, Isocaine, Polocaine) prilocaine ropivacaine (Naropin) Esters benzocaine (Americaine, Anbesol, Solarcaine, others) NS depression and burning, stinging and redness at topical application sites chloroprocaine (Nesacaine) espiratory arrest, circulatory failure, anaphylactoid reaction procaine (Novocain) proparacaine (Alcaine, phthetic) tetracaine (Pontocaine) Miscellaneous drugs dyclonine (Dyclone) Burning, stinging, sensation at application site ethyl chloride or chloroethane espiratory or cardiac arrest pramoxine (Tronothane) Note: Italics indicate common adverse effects; underlining indicates serious adverse effects. 276

4 General formula Example Ester H2N 2H2 N 2H5 2H5 Procaine H3 Amide NH NH H3 H2 N 2H5 2H5 Lidocaine Animation: Mechanism of Action: lidocaine Type Figure 2 hemical structures of ester and amide local anesthetics until the development of the amide anesthetics led to a significant decline in the use of the drug. ne ester, benzocaine (Solarcaine, others), is used as a topical (T) agent for treating a large number of painful conditions, including sunburn, insect bites, hemorrhoids, sore throat, and minor wounds. Tetracaine is often sprayed on the skin or mucous membranes to cause loss of feeling before and during surgery or endoscopic procedures. For example, a topical anesthetic comprising a combination of benzocaine, butamben, and tetracaine (etacaine) is used in examinations of the esophagus or colon. Proparacaine Prototype Drug (Alcaine, phthetic) is a drug used for short-term anesthesia in ocular procedures. Amides Amides have largely replaced the esters because they produce fewer side effects and generally have a longer duration of action. Lidocaine (Xylocaine) is the most widely used amide for short surgical procedures requiring local anesthesia. Ethyl chloride or chloroethane is a mild topical miscellaneous drug supplied as a liquid in a spray bottle. It Lidocaine (Xylocaine) Therapeutic lass: Anesthetic (local/topical); antidysrhythmic (class Ib) Pharmacologic lass: Sodium channel blocker; amide AtIonS AnD USeS lidocaine, the most frequently used injectable local anesthetic, acts by blocking neuronal pain impulses. It may be injected as a nerve block for spinal and epidural anesthesia. It acts by blocking sodium channels located within the membranes of neurons. lidocaine may be given IV, IM, or subcutaneously to treat dysrhythmias. A topical form is also available. ADverSe effets When lidocaine is used for anesthesia, side effects are uncommon. An early symptom of toxicity is NS excitement, leading to irritability and confusion. Serious adverse effects include convulsions, respiratory depression, and cardiac arrest. Until the effect of the anesthetic diminishes, patients may injure themselves by biting or chewing areas of the mouth that have no sensation following a dental procedure. ADMInIStrAtIon ALertS Solutions of lidocaine containing preservatives or epinephrine are intended for local anesthesia only and must never be given parenterally for dysrhythmias. Do not apply topical lidocaine to large skin areas or to broken or abraded areas, because significant absorption may occur. Do not allow it to come into contact with the eyes. For spinal or epidural block, use only preparations specifically labeled for IV use. Pregnancy category b. ontraindications: lidocaine should be avoided in cases of sensitivity to amide-type local anesthetics. Application or injection of lidocaine anesthetic is also contraindicated in the presence of severe trauma or sepsis, blood dyscrasias, dysrhythmias, sinus bradycardia, and severe degrees of heart block. PHArMAoKInetIS nset Peak Duration sec IV; 5 15 min IM; 2 5 min topical less than 30 min min IV; min IM; min topical; more than 100 min injected for anesthesia InterAtIonS Drug Drug: barbiturates may decrease the activity of lidocaine. Increased effects of lidocaine occur if taken concurrently with cimetidine, quinidine, and beta blockers. If lidocaine is used on a regular basis, its effectiveness may diminish when used with other medications. Lab Tests: Increased PK. Herbal/Food: Unknown. Treatment of verdose: Emergency medical attention is needed because of the many associated substantive symptoms such as breathing difficulty, swelling of the lips, chest pain, irregular heartbeat, nausea, vomiting, tremors, and seizure activity. 277

5 Nursing Process Focus Assessment Baseline assessment prior to administration: btain a complete health history including cardiovascular, hepatic, renal, respiratory, or neurologic disease; pregnancy; or breast-feeding. btain a drug history including allergies, current prescription and T drugs, herbal preparations, caffeine, nicotine, and alcohol use. If the patient reports an allergy to caine drugs, note the specific reactions the patient experienced. be alert to possible drug interactions. btain baseline vital signs and weight. Assess for areas of broken skin, abrasions, burns, or other wounds in the area to be treated with local anesthetic. Evaluate laboratory findings appropriate to the procedure (e.g., complete blood count [b], electrolytes, hepatic or renal function studies). Assess the patient s ability to receive and understand instruction. Include the family and caregivers as needed. Assessment throughout administration: Assess for desired therapeutic effects (e.g., local or regional area numbness). Assess vital signs, especially blood pressure (bp) and pulse, if regional block is used. eport a bp less than 90/60, pulse above 100, or per parameters as ordered by the health care provider. Assess the local or regional area blocked. Expect blanching in a localized area if the local anesthetic contained epinephrine. If a regional area was blocked, periodically assess the ability to move limbs distal to the block. Assess the level of consciousness if a large regional block was given. eport any increasing drowsiness, dizziness, light-headedness, confusion, or agitation immediately. Assess for and promptly report adverse effects: bradycardia or tachycardia, hypotension or hypertension, and dyspnea. The patient will: PAtIentS reeiving LoAL AneStHeSIA Acute Pain PotentiAL nursing DiAGnoses Deficient Knowledge (drug therapy) isk for Aspiration isk for Infection isk for Injury PLAnninG: PAtient GoALs AnD expected outcomes Experience therapeutic effects (e.g., numbness in the local or regional area). be free from, or experience minimal, adverse effects. Verbalize an understanding of the drug s use, adverse effects, and required precautions. Demonstrate proper self-administration of the medication (e.g., dose, timing, when to notify provider). Interventions and (rationales) Ensuring therapeutic effects: ontinue assessments as described earlier for therapeutic effects. Assess the localized area for numbness and blanching if the local anesthetic included epinephrine. Assess the ability to move limbs distal to the regional anesthetic. (The duration of anesthetic action will depend on the solution used and whether epinephrine is included in the solution. Epinephrine in the anesthetic solution will constrict localized blood vessels and result in blanching of the area.) implementation Patient-entered are Teach the patient that the area may be numb for several hours after the procedure is completed. Teach the patient that it is normal that a slight pressure sensation may remain during anesthesia (e.g., sensation of tugging during suturing) but that no pain should be felt. Have the patient alert the health care provider if more than a slight pressure sensation or any pain is noticed during anesthesia. Teach the patient that it is normal to regain some ability to move limbs (e.g., after epidural anesthetic) and movement may return before the ability to feel the movement. 278

6 Nursing Process Focus PAtIentS reeiving LoAL AneStHeSIA (ontinued) implementation Interventions and (rationales) Patient-entered are Minimizing adverse effects: ontinue to monitor vital signs, especially blood pressure and pulse, for patients given regional anesthesia. Immediately report a bp below 90/60 or per parameters as ordered by the health care provider, tachycardia or bradycardia, changes in level of consciousness, or dyspnea or decrease in respiratory rate. (Adverse effects of local anesthesia are rare. egional blocks may cause hypotension with the possibility of reflex tachycardia. bradycardia, hypotension, decreased level of consciousness, decreased respiratory rate, and dyspnea may signal that the anesthesia has entered the systemic circulation and is acting as a general anesthetic.) aution the patient not to eat, chew gum, or drink until the mouth sensation has returned if local (dental) or oral/throat anesthesia has been used. If throat anesthesia was used, assess the gag reflex before eating. (local anesthetics are effective for up to 3 hours or more. biting injuries to oral mucous membranes may occur while tissue is numb. Aspiration of food or liquids is possible until swallowing sensation and gag reflex returns.) Ensure patient safety; monitor motor coordination and/or ambulation post regional block until certain motor movement is unaffected. be particularly cautious with older adults who are at an increased risk for falls. (Numbness or effects on motor ability post regional anesthetic may impair movement and increase the risk of falls or injuries.) Assess areas of abrasion, burns, or open wounds if a local anesthetic was applied to the area. (large, open, or denuded areas may increase the amount of drug absorption into the general circulation. Use sterile technique to apply the drug to open areas.) ead all labels carefully before using parenteral solutions. (Solutions containing epinephrine must never be used IV or for local anesthesia in areas of decreased circulation [e.g., fingertips, toes, earlobes] due to vasoconstrictive effects.) Monitor pain relief in patients post regional block (e.g., epidural). (Pain sensation will increase as the regional block wears off. Additional pain relief may be required.) Patient understanding of drug therapy: Use opportunities during administration of medications and during assessments to provide patient education. (Using time during nursing care helps to optimize and reinforce key teaching areas.) Patient self-administration of drug therapy: When administering the medication, instruct the patient, family, or caregiver in proper self-administration of the drug (e.g., take the drug as prescribed when needed). (Using time during nurse administration of these drugs helps to reinforce teaching.) Instruct the patient to report any increasing nausea, drowsiness, dizziness, light-headedness, confusion, or anxiety immediately. Instruct the patient to refrain from eating or drinking for 1 hour or more postanesthesia or until sensation has completely returned to the oral cavity or throat. Instruct the patient to call for assistance prior to getting out of bed or attempting to walk alone post epidural block, and to avoid driving or other activities requiring physical coordination (e.g., regional upper limb block) until the residual effects of the drug are known. Instruct the patient to report increased redness, swelling, or drainage from open areas under treatment. Provide an explanation of desired effects of the local anesthetic and the need for postprocedure monitoring. Teach the patient to report any discomfort or pain as the anesthesia wears off. The patient should be able to state the reason for the drug, anticipated sensations, and adverse effects to observe for and when to report them. Teach the patient to take oral medication (e.g., lidocaine viscous) by swishing and spitting if used for oral cavity or by gargling, and do not swallow unless directed by the health care provider. Apply topical medication in a thin layer to the skin area as directed. evaluation of outcome criteria Evaluate the effectiveness of drug therapy by confirming that patient goals and expected outcomes have been met (see Planning ). See Table 2 for a list of drugs to which these nursing actions apply. Source: Potential Nursing Diagnoses: NANDA-I 2012 is used for basic procedures such as removing splinters or small debris from the skin s surface. Adverse effects of local anesthetics are not common. Allergy is rare. When it does occur, it is often due to sulfites, which are added as preservatives to prolong the shelf life of the anesthetic, or to methylparaben, which may be added to retard bacterial growth in anesthetic solutions. Early signs of adverse effects of local anesthetics include symptoms of central nervous system (NS) stimulation such as restlessness or anxiety. Later effects, such as drowsiness and unresponsiveness, are due to NS depression. ardiovascular effects, including hypotension and dysrhythmias, are 279

7 Weblink: American Society of Anesthesiologists possible. Patients with a history of cardiovascular disease are often given forms of local anesthetics that contain no epinephrine to reduce the potential effects of this sympathomimetic on the heart and blood pressure. NS and cardiovascular side effects are not expected unless the local anesthetic is absorbed rapidly or is accidentally injected directly into a blood vessel. TAblE 3 Stage GeneraL anesthesia General anesthesia is loss of sensation throughout the entire body, accompanied by loss of consciousness. General anesthetics are applied when it is necessary for patients to remain still and without pain for a longer time than could be achieved with local anesthetics. 4 haracteristics of General Anesthesia The goal of general anesthesia is to provide a rapid and complete loss of sensation. Signs of general anesthesia include total analgesia and loss of consciousness, memory, and body movement. Although these signs are similar to those of sleeping, general anesthesia and sleep are not exactly the same. General anesthetics depress most nervous activity in the brain, whereas sleeping depresses only very specific areas. In fact, some brain activity actually increases during sleep. General anesthesia is rarely achieved with a single drug. Instead, multiple medications are used to rapidly induce unconsciousness, cause muscle relaxation, and maintain deep anesthesia. This approach, called balanced anesthesia, allows a lower dose of inhalation anesthetic, thus making the procedure safer for the patient. General anesthesia is a progressive process that occurs in distinct phases. The most efficacious medications can quickly induce all four stages, whereas others are able to induce only stage 1. Stage 3 is where most major surgery occurs; thus, it is called surgical anesthesia. When seeking surgical anesthesia, it is desirable to progress through stage 2 as rapidly as possible because this stage produces distressing symptoms. These stages are listed in Table 3. There are two primary methods of inducing general anesthesia. Intravenous drugs are usually administered first TAblE 4 Type Gas Stages of general Anesthesia haracteristics 1 loss of pain: The patient loses general sensation but may be awake. This stage proceeds until the patient loses consciousness. 2 Excitement and hyperactivity: The patient may be delirious and try to resist treatment. Heart rate and breathing may become irregular and blood pressure can increase. IV agents are administered here to calm the patient. 3 Surgical anesthesia: Skeletal muscles become paralyzed. ardiovascular and breathing activities stabilize. Eye movements slow and the patient becomes still. 4 Paralysis of the medulla region in the brain (responsible for controlling respiratory and cardiovascular activity): If breathing or the heart stops, death could result. This stage is usually avoided during general anesthesia. because they act within a few seconds. After the patient loses consciousness, inhaled drugs may be used to maintain the anesthesia. During short surgical procedures or those procedures requiring a lower level of anesthesia, IV drugs may be used alone. GeneraL anesthetics General anesthetics are drugs that rapidly produce unconsciousness and total analgesia. To supplement the effects of a general anesthetic, adjunct drugs are given before, during, and after surgery. Inhalation Agents 5 Pharmacotherapy with Inhaled General Anesthetics Inhaled general anesthetics, listed in Table 4, are gases and volatile liquids. These drugs produce their effects by preventing the flow of sodium into neurons in the NS, thus delaying nerve impulses and producing a dramatic reduction in neural activity. The exact mechanism is not exactly known, although it is likely that gamma-aminobutyric acid (GABA) receptors in the brain are activated. It is not the same mechanism as is known for local anesthetics. There is Inhaled general Anesthetics Drug nitrous oxide General Adverse Effects Dizziness, drowsiness, nausea, euphoria, vomiting Malignant hyperthermia, apnea, cyanosis Volatile liquid desflurane (Suprane) Drowsiness, nausea, vomiting enflurane (Ethrane) Myocardial depression, marked hypotension, pulmonary vasoconstriction, hepatotoxicity isoflurane (Forane) sevoflurane (Ultane) Note: Italics indicate common adverse effects; underlining indicates serious adverse effects. 280