Anesthetics and its side affect Mechanism of action

It's is for care of preoperative patient

1. ANESTHETICS DRUGS

2. By the completion of this section the learners will be able to: Define the term anesthesia and anesthetic agents Differentiate between different types of anesthesia Identify the stages of general anesthesia Describe Characteristics of general and local anesthetic agents. Identify most commonly used anesthetic agents Discuss factors considered when choosing anesthetic agents. Compare general and local anesthesia in terms of administration, client’s safety and nursing care. Discuss the rationale for using adjunctive drugs before and during surgical procedures. Describe the nursing role in related to anesthetics and adjunctive drugs. Discuss the action, indication and side effects of neuro-muscular blocking agent Calculate the drug dosage of injectable anesthetic agent OBJECTIVES

3. Anesthesia The word anesthesia is coined from two Greek words: "an" meaning "without" and " aesthesis“ meaning "sensation". Anesthesia refers to the practice of administering medications either by injection or by inhalation (breathing in) that block the feeling of pain and other sensations , or that produce a deep state of unconsciousness that eliminates all sensations, which allows medical and surgical procedures to be undertaken without causing undue distress or discomfort.

4. Anesthesia It is a pharmacologically induced and reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes or decreased stress response, or all simultaneously. The pre-existing word anesthesia was suggested by Oliver Wendell Holmes, Sr. in 1846 as a word to use to describe this state. Anesthesiology is a special branch of medicine. Clinically – What an Anaesthetist wants ??? Triad of GA

5. Anesthetic Agents Anesthetic drugs are the agents that produces anesthesia or bring a bout reversible loss of sensation . Two types a) General Anesthetics b) L ocal or R egional Anesthesia

6. General Anesthetics General anesthesia refers to inhibition of sensory, motor and sympathetic nerve transmission at the level of the brain , resulting in unconsciousness and lack of sensation . General anesthesia – for surgical procedure to make the patient unaware / unresponsive to the painful stimuli Drugs producing General Anesthesia – are called General Anesthetics

7. Local Anesthesia Local anesthesia - reversible inhibition of impulse generation and propagation in nerves. In sensory nerves, such an effect is desired when painful procedures must be performed, e.g., surgical or dental operations Drugs producing Local Anesthesia – are called Local Anesthetics e.g. Procaine, Lidocaine and Bupivacaine etc. Local anesthesia inhibits sensory perception within a specific location on the body, such as a tooth or the urinary bladder

8. Regional Anesthesia Regional Anesthesia : Regional anesthesia renders a larger area of the body insensate by blocking transmission of nerve impulses between a part of the body and the spinal cord. Two frequently used types of regional anesthesia are spinal anesthesia and epidural anesthesia .

9. Spinal Anesthesia Spinal Anesthesia: It is achieved by injection 1.8 ml of 5% lignocaine solution into the subarachnoid space through a lumber puncture. Other drugs which can be used are cinchocaine, procaine and amethocaine . It can cause serious hypotension.

10. Epidural Anesthesia Epidural Anesthesia : It is achieved by injection 1 to 2 % of lignocaine solution in the epidural space. It blocks the nerves which traverse the epidural space. It can cause hypotension , which is less severe than with spinal analgesia. For prolonged operations, a catheter may be passed into the epidural space for intermittent administration of local anesthesia .

11. Stages General Anesthesia Four stages of anesthesia Stage I Analgesia Stage II Excitement Stage III Surgical anesthesia Stage IV Medullary paralysis

12. Stages cont.... Stage I Analgesia Loss of pain sensation Drowsiness Amnesia and reduced awareness of pain Stage II Excitement Delirium Rise and irregularity in blood pressure and respiration Risk of laryngospasm To shorten this period a rapid acting anesthetic like propofol is administered IV before inhaled anesthetic

13. Stages cont.... Stage III: Surgical anesthesia Loss of muscle tone and reflexes Ideal stage for surgery Requires careful monitoring Stage IV: Medullary paralysis Severe depression of the respiratory and vasomotor centers Death can occur unless respiration and circulation are maintained

14. Drugs use as GA (Classification) Inhalation: Gas : Nitrous Oxide Volatile Liquid : Ether Halothane Enflurane Isoflurane Desflurane Sevoflurane Intravenous : Inducing agents: Thiopentone, Methohexitone sodium, propofol and etomidate 2. Benzodiazepines (slower acting): Diazepam, Lorazepam, Midazolam 3. Other drugs Ketamine Fentanyl

15. Local Anesthetics Ester Linkage Amide Linkage (2 Eyes!!) PROCAINE procaine (Novocaine) tetracaine (Pontocaine) benzocaine cocaine LIDOCAINE (lignocaine) lidocaine (Xylocaine) mepivacaine (Carbocaine) bupivacaine (Marcaine) etidocaine (Duranest) ropivacaine (Naropin)

16. Factors consider when choosing anesthetics drugs Choice of anesthetic drugs are made to provide safe and efficient anesthesia based on the nature of the surgical or diagnostic procedures and patient’s physiologic, pathologic and pharmacologic state

17. Patients factors in selection of anesthetics 2 factors are important Status of organ system Cardiovascular system Respiratory system Liver and kidney Nervous system Pregnancy Concomitant use of drugs Multiple adjunct agents Non-anesthetic drugs

18. Status of the organ Cardiovascular system: Anesthetic agents suppress cardiovascular functions. Ischemic injury to tissues may follow reduced perfusion pressure if a hypotensive episode occurs during anesthesia, treatment with vasoactive substances may be necessary Some anesthetics like halothane sensitize the heart to arrhythmogenic effects of sympathomimetics

19. Status of organs system cont.... Respiratory system Asthma may complicate control of inhalation anesthetic Inhaled anesthetics depress the respiratory system IV anesthetics and opioids suppress respiration These effects may influence the ability to provide adequate ventilation and oxygenation

20. Status of the organ system cont.... Liver and kidneys Affect distribution and clearance of anesthetics, and might be affected by anesthetic toxic effects Their physiology must be considered Nervous system Presence of neurologic disorders like epilepsy, myasthenia gravis, problems in cerebral circulation Pregnancy Effects of anesthetic agents on the fetus Nitric oxide causes aplastic anemia in the unborn child Benzodiazepines might cause oral clefts in the fetus

21. Concomitent use of drugs Multiple adjunct agents Multiple agents are administered before anesthesia, these agents facilitate induction of anesthesia and lower the needed dose of anesthetics They may enhance adverse effects of anesthesia like hypoventilation

22. Adjunctive drugs or Pre-anesthetic drugs Serve to calm the patient, relieve the pain and protect against undesirable effects of anesthetics or the surgical procedure Antacids (neutralize stomach acidity) H2 blockers like famotidine (Reduce gastric acidity) Anticholinergics like atropine and glycopyrrolate (Prevent bradycardia and secretion of fluids) Antiemetics like ondansetron (Prevent aspiration of stomach contents and postsurgical nausea and vomiting and) Antihistamine (Prevent allergic reactions) Benzodiazepines like diazepam (Relieve anxiety) Opioids like fentanyl (Provide analgesia) Neuromuscular blockers (Facilitate intubation and relaxation)

23. Rationals for using adjunctive drugs before and during Surgical procedure For patients undergoing surgical and other medical procedures anesthesia provides these benefits: Sedation and reduction of anxiety Lack of awareness and amnesia Skeletal muscle relaxation Suppression of undesirable reflexes Analgesia Because no single agent can provide all those benefits, several drugs are used in combination to produce optimal anesthesia

24. Characteristics of general and local anesthetic agents

25. Anesthetics Potent general anesthetics are delivered via inhalation or IV injection Inhaled general anesthetics Intravenous general anesthetics Local anesthetics

26. Inhaled anesthetics Halothane Isoflurane Sevoflurane Nitrous oxide Desflurane

27. Inhaled anesthetics

28. Inhaled anesthesia cont.... Used for maintenance of anesthesia after administration of an IV agent The depth of anesthesia can be altered rapidly by changing inhaled concentration of the drug

29. Inhaled anesthetic cont.... No specific receptor has been identified as the locus of general anesthetic action Anesthetics increase the sensitivity of GABA receptors to the neurotransmitter GABA prolonging the inhibitory chloride ion current after GABA release, reducing the postsynaptic neurons excitability Anesthetics increase the activity of the inhibitory glycine receptors in the spinal motor neuron Anesthetics block excitatory postsynaptic nicotinic currents The mechanism by which the anesthetics perform these modulatory roles is not understood Mechanism of action

30. Halothan Potent anesthetic, weak analgesic. Administered with nitrous oxide, opioids or local anesthetics Being replaced by other agents due to its adverse effects like Malignant Hyperthermia

31. Halothan cont.... Cardiac effects: Vagomimetic effects, bradycardia, can cause cardiac arrhythmias Malignant hyperthermia: Rare and life threatening condition Uncontrolled increase in skeletal muscle oxidative metabolism, which overwhelms the body’s capacity to supply oxygen, remove carbon dioxide, and regulate body temperature If untreated would cause circulatory collapse and death Treatment: Dantrolene administration Adverse effect

32. Nitrous oxide Non irritating and potent analgesic but a weak general anesthetic Nitrous oxide is frequently employed at concentration of 30-50% in combination with oxygen for analgesia Nitrous oxide at 80% (without adjunct agents) cannaot produce surgical anesthesia Combine with other , more potent agents to attain pain-free anesthesia Mechanism of action is unresolved, might involve activity of GABA and NMDA receptors Least hepatotoxic of all inhaled anesthetic

33. Intravenous Anesthesia Used in situations that require short duration anesthesia (outpatient surgery) Primarily used as adjuncts to inhalationals Administered first Rapidly induce unconsciousness In lower doses, they may be used to provide sedation

34. IV Anesthetics cont.... Induction After entering the blood stream, a percentage of the drug binds to the p lasma proteins, and the rest remains unbound (free) The drug is carried by venous blood to the heart The majority of the CO (70%) flows to the brain, liver, and kidney Once the drug has penetrated the CNS tissue, it exerts its effects The exact mechanism of action of IV anesthetics is unknown Recovery Recovery from IV anesthetics is due to redistribution from sites in the CNS

35. IV Anesthetics cont.... Propofol Fospropofol Barbiturates Benzodiazepines Opioids Ketamine

36. Propofol IV sedative/hypnotic used in the induction or maintenance of anesthesia Widely used and has replaced thiopental as first choice for anesthesia induction and sedation, because it does not cause postanesthetic nausea and vomiting The induction of anesthesia occurs within 30–40 seconds of administration Supplementation with narcotics for analgesia is required Propofol decreases blood pressure without depressing the myocardium It also reduces intracranial pressure due to systemic vasodilation

37. Opioids Commonly used with anesthetics due to their analgesic property The choice of opioid used perioperatively is based primarily on the duration of action needed Fentanyl, R emifentanil Induce analgesia more rapidly than morphine Administered intravenously, epidurally, intrathecally Can cause hypotension, respiratory depression, muscle rigidity and postanesthetic nausea and vomiting Opioid effects can be antagonized by naloxone

38. Local Anesthetics Amides (lidocaine) and esters (procaine) Cause loss of sensation ( in higher concentrations ), and motor activity ( in a limited area of the body ) Applied or injected to block nerve conduction of sensory impulses from the periphery to the CNS

39. Local Anesthetics cont.... Local anesthesia is induced when propagation of action potentials is prevented, so that sensation cannot be transmitted from the source of stimulation to the brain Mechanism of action Work by blocking sodium ion channels to prevent the transient increase in permeability of the nerve membrane to sodium that is required for an action potential to occur

40. Local Anesthetics cont.... Lidocaine Bupivacaine Procaine Ropivacaine Tetracaine Mepivacaine Not used in obstetric anesthesia due to its increased toxicity to the neonate

41. Local Anesthetics cont.... Local anesthetics cause vasodilation, which leads to rapid diffusion away from the site of action and results in a short duration of action Adding the vasoconstrictor epinephrine to the local anesthetic, the rate of local anesthetic diffusion and absorption is decreased This both minimizes systemic toxicity and increases the duration of action

42. Topical Anesthetics They are applied directly to the skin or mucous membranes Benzocaine is the major drug in this group Lidocaine and tetracaine ca n be used topically They are used to relieve or prevent pain from minor burns, irritation, itching They are also used to numb an area before an injection is given. Expected adverse effects involve skin irritation and hypersensitivity reactions

43. Comparison of general vs local anesthesia

44. Advantages of General Anesthetics Reduces intra-operative patient awareness and recall. Allows proper muscle relaxation for prolonged periods of time. Facilitates complete control of the airway, breathing, and circulation. Can be used in cases of sensitivity to local anesthetic agent. Can be administered rapidly and is reversible.

45. Disadvantages of General Anesthetics Requires increased complexity of care and associated costs. Requires some degree of preoperative patient preparation. Can induce physiologic fluctuations that require active intervention. Associated with malignant hyperthermia

46. Nursing role in GA Assessment : Prescription, non-prescription or any other Drug History Allergies Other risk factors – smoking, obesity, alcoholism, CVS/renal/respiratory diseases Vital signs and laboratory data Interventions : Explain preoperative and post operative recovery Postoperative requirements – early ambulation, deep breathing, coughing, leg exercises, fluid balance and urine output Monitor vital signs Response to pain medication

47. Advantages of Local Anesthetics During local anesthesia the patient remains conscious. Patient maintains own airway. Aspiration of gastric contents unlikely. Recovery is smooth as it requires less skilled nursing care as compared to other anesthesia like general anesthesia. Postoperative analgesia. There is reduction surgical stress. Earlier discharge for outpatients. Expenses are less.

48. Disatvanages of Loca Anesthetics Very rare allergies Bruises Temporary tingling sensation or burning in the area

49. Nursing role of Local Anesthetics Assess for the mentioned cautions and contraindications (e.g. drug allergies, hepatic and renal impairment, etc.) to prevent any untoward complications. Inspect site for local anesthetic application to ensure integrity of the skin and to prevent inadvertent systemic absorption of the drug. Ensure that patients receiving spinal anesthesia or epidural anesthesia are well hydrated and remain lying down for up to 12 hours after the anesthesia to minimize headache. Provide skin care to site of administration to reduce risk of skin breakdown. Provide safety measures (e.g. adequate lighting, raised side rails, etc.) to prevent injuries .

50. References Karch , A. M., & Karch . (2011).  Focus on  nursing pharmacology . Wolters Kluwer Health/Lippincott Williams & Wilkins. [ Link ] Katzung , B. G. (2017).  Basic and clinical pharmacology . McGraw-Hill Education. Lehne , R. A., Moore, L. A., Crosby, L. J., & Hamilton, D. B. (2004). Pharmacology for nursing care. Smeltzer , S. C., & Bare, B. G. (1992).  Brunner & Suddarth’s textbook of medical-surgical nursing . Philadelphia: JB Lippincott.