General Anesthesia Drugs & Types PDF

 Introducti on Drugs used to induce loss of pain sensation, loss of consciousness, skeletal muscle relaxation, analgesia, amnesia and inhibitions of undesirable autonomic reflexes.  General anesthesia Local anesthesia  Stage I (analgesia) - Lo...

 Introducti on Drugs used to induce loss of pain sensation, loss of consciousness, skeletal muscle relaxation, analgesia, amnesia and inhibitions of undesirable autonomic reflexes.  General anesthesia Local anesthesia  Stage I (analgesia) - Loss of pain sensation. - The patient is conscious and conversational. Stage II (Excitement) - Increased respiratory rate. - Increased, irregular blood pressure. - Patient may experience delirium & violent behavior. - Eye dilated & reactive.  Stage III (Surgical anesthesia) - Regular respiration & relaxation of sk. muscles. - Eye reflexes decrease until the pupil is fixed. Stage IV (coma and death) - Medullary paralysis. -Severe depression of vasomotor -Depression of respiratory centers. - Death may occur. 1. Smooth and rapid induction. 2. Rapid recovery. 3. Wide safety margin. 4. Minimal side effects. Is the use of more than one drug in combination to fulfil the patient needs. Beneficial effects Adverse effects Balanced anaesthesia is achieved by a combination of Pre-anaesthetic medications, I.V anaesthetics and inhaled anaesthetics.  Calm the patient, relieve pain  Protect against undesirable effects of the administered anesthetics or the surgical procedure.  Facilitate smooth induction of anaesthesia  Lowered the dose of anaesthetic required Opiates: induce analgesia e.g. morphine Anticholinergics: prevent secretion of fluids into the respiratory tract e.g. hyoscine  Sedatives & anxiolytics: relieve anxiety. e.g. diazepam  Antihistaminics: allergic reactions. e.g. diphenhydramine  Antiemetics : post surgical N&V. e.g. metoclopramide, prochlorperazine  H2-receptor blockers: reduce gastric acidity e.g. ranitidine Thiopental: smooth induction   Pre-anesthetic medication.  Neuromuscular blocking agents  e.g. succinylcholine, vecuronium, atracurium  Facilitate intubation  Suppress muscle tone. Disruption of the function of ionic channels Disruption of lipids associated with ionic channels Receptors Inhibitory : GABA , glycine Excitatory : nAch, NMDA Enhance the action of GABA and glycine on receptors leading to greater entrance of chloride ion hyperpolarization thus decrease neuronal excitability. 10/16/24 2017  Are halogenated hydrocarbons, end with suffix “flurane”  Methoxyflurane  Halothane  Enflurane  Isoflurane  Desflurane  Sevoflurane  Nitrous oxide Structures Inhalational Sevoflurane Halothane Isoflurane  Rate of induction  Depth of anesthesia and recovery. Induction Time elapsed between onset of administration of anesthetic and development of effective surgical anesthesia. Maintenance Time during which the patient is surgically anesthetized. Recovery The time from discontinuation of anesthetic drug until consciousness is regained. Factors controlling induction & recovery  The anesthetic concentration in the inspired air: (Direct).  Rate and depth of ventilation (Direct). Blood solubility: Blood: gas partition coefficient (It is inversely related to induction rate). Drugs Solubility Induction & Recovery (Blood : gas partition coefficient ) Methoxyflurane 12 Slow Halothane 2.3 Slow Enflurane 1.8 Medium Isoflurane 1.4 Medium Sevoflurane 0.69 Rapid Desflurane 0.42 poor & Rapid Nitrous Oxide 0.47 Rapid  It is the concentration of inhalation anesthetic that produce immobility in 50 % patients in response to surgical incision. Potency of anesthetic agents. Oil: gas partition coefficient (Direct with potency). The lower the MAC value the more potent the drug (inverse). Decreased by CNS depressants, old people. Increased by CNS stimulants. Drugs MAC POTENCY Methoxyflurane 0.16 Halothane 0.75 Isoflurane 1.4 Enflurane 1.7 Sevoflurane 2 Desflurane 6-7 Nitrous oxide >100  POTENCY & INDUCTION & VELOCITY Drugs Methoxyflurane: The most potent, low MAC value, slow induction& recovery Halothane: Potent, slow induction & recovery (pleasant odor) Enflurane: less potent, medium induction & recovery (pungent odor) Isoflurane: less potent, medium induction & recovery Sevoflurane : less potent, rapid induction & recovery (better smell) Desflurane: Rapid induction & rapid recovery (pungent odor) Nitrous oxide: The least potent, high MAC value, rapid induction & recovery  CNS -  metabolic rate. -  ICP (due to cerebral vasodilatation) # in head injuries. - Dose -dependent EEG changes (Enflurane). CVS - Hypotension - Bradycardia Except (Isoflurane & Desflurane ). - Myocardial depression (Halothane – Enflurane). -Sensitize heart to catecholamines (Halothane)  Respiratory - All respiratory depressants -Airway irritation (Desflurane-Enflurane) Liver Decrease hepatic flow - - Hepatotoxicity (Only halothane) Uterus & Skeletal Muscles -Uterine relaxation - Nitrous oxide has minimal relaxant effect (labor). - All are skeletal muscle relaxants.  Halothane Potent anesthetic, slow induction and recovery Weak analgesic, weak skeletal muscle relaxant. Metabolized to toxic metabolites (trifluroethanol) hepatotoxic. CVS depression Hypotension, bradycardia (vagomimetic action)  Myocardial contractility,  Cardiac output Adverse Effects 1.Hepatotoxicity (repeated use). 2.Malignant hyperthermia. 3.Cardiac arrhythmias. 4.Sensitizes heart to action of catechalamines arrhythmias.  Enflurane Less potent than halothane. Better muscle relaxation, Better analgesic properties. is metabolized to fluoride (8%), excreted in the kidney More rapid induction and recovery than halothane. Disadvantages Pungent (Less induction -Not for pediatrics). CNS stimulation (Epilepsy-like seizure- abnormal EEG). Contraindication patients with seizure disorders. Not for renal failures.  Isoflurane (Forane)  More rapid induction & recovery than halothane  Stable compound (2%).  Low biotransformation (Less fluoride).  No nephrotoxicity - No hepatotoxicity.  Good analgesic action.  No sensitization of the heart.  No cardiac arrythmias. Disadvantages Pungent (Not for pediatrics).  Desflurane  Less potent than halothane.  Pungent odor (irritation - Cough)  Rapid induction & fast recovery (Low solubility).  Less metabolized (0.05 %).  Low boiling point (special equipment).  Sevoflurane Better smell Less potent than halothane Rapid onset and recovery (Low solubility) Less metabolized (3- 5% fluoride) Little effect on HR No airway irritation (preferable for children)  Nitrous Oxide (N2O) Weak anesthetic (Low potency, combined). Rapid induction & Recovery (the lowest blood: gas partition coefiicient). Potent analgesic. No muscle relaxation, No respiratory depression. Not hepatotoxic, minimal CVS adverse effects. Adverse Effects 1.Diffusion Hypoxia: (respiratory diseases). 2. Nausea and vomiting. 3. Inactivation of B 12  megaloblastic anemia. 4. Bone marrow depression-Leukopenia (chronic use). 5. Abortion - Congenital anomalies  Therapeutic Uses 1. Outpatient anesthesia (Dental procedures). 2. Balanced anesthesia. 3. Neuroleptanalgesia. 4. Delivery Contraindications 1. Pregnancy. 2. Pernicious anemia. 3. Immunosuppression. Anesthetic Characters drugs Methoxyfluran For veterinary use only e Halothane Non irritant - Potent anesthetic, Weak analgesic. Can be used in children Isoflurane Stable compound (2%), Low biotransformation (Less fluoride). No nephrotoxicity - No hepatotoxicity. Enflurane is metabolized to fluoride (8%) Contraindicated in patients with seizure disorders. Not for renal failures. Desflurane Less metabolized (0.05 %), low boiling point (special equipment) Sevoflurane Better smell, little effect on HR, No airway irritation (children) Nitrous oxide 10/16/24 Potent analgesics, weak anesthetic, Minimal CVS adverse effects, Anesthetic Side effects drugs Methoxyfluran Slow induction, nephrotoxicity e Halothane Slow induction and recovery Sensitization of heart to catecholamines Hepatotoxicity, Malignant hyperthermia Desflurane Pungent odor, Airway irritation Enflurane Pungent (less induction -Not for pediatrics). Airway irritation CNS stimulation (Epilepsy-like seizure- abnormal EEG). Nitrous oxide Weak anesthetic (low potency, combined). Diffusion hypoxia, Nausea and vomiting. Inactivation of B 12  megaloblastic anemia, congenital anomalies   Ultra short acting barbiturates e.g. thiopental, methohexital  Benzodiazepines (diazepam, lorazepam, midazolam)  Opioids (fentanyl)  Ketamine  Propofol  Etomidate Structures Intravenous Thiopental Ketamine Propofol Etomidate   NO need for special equipments.  Rapid induction & recovery EXCEPT benzodiazepines  Injected slowly (rapid induction).  Recovery is due to redistribution from CNS.  Analgesic activity: Opioids & ketamine  Amnesic action: benzodiazepines & ketamine.  Can be used alone in short operation & Outpatients anesthesia.  Drug Induction and recovery Thiopental Fast onset, slow recovery, hangover Etomidate Fast onset, fairly fast recovery, less hangover Propofol Fast onset, rapidly metabolized, very fast recovery Ketamine Slow onset, Dissociative anesthesia Produces good analgesia and amnesia. Fentanyl Slow onset Midazolam Slower onset than other agents, has amnesic effect e.g. Thiopental, Methohexital Rapid onset of action 1 min (high lipid solubility). Ultra short duration of action 15 - 20 min Metabolized slowly by the liver (slow recovery) Potent anesthetic. CNS:  ICP (Used in head injuries). CVS collapse & respiratory depression, precipitate porphyria attack, hypersensitivity reaction. Used for induction in major surgery and alone in minor surgery.   Hypnotic (Non Barbiturate).  Rapid onset, short duration of action, Faster recovery than thiopental  Rapidly metabolized in liver (10 times - Elimination ½ = 30 – 60 min).  Decreases  ICP  Has Antiemetic action. Side Effects  Hypotension (PVR).  Excitation (involuntary movements), Pain at site of injection  Expensive, Clinical infections due to bacterial contamination e.g. Midazolam, Diazepam , Lorazepam  No pain, have anxiolytic and amnesic action  Slow induction & recovery.  Cause respiratory depression.  Used in induction of general anesthesia.  Alone in minor procedure (endoscopy).  In balanced anesthesia (Midazolam).   Ultrashort acting hypnotic (Non Barbiturates).  Rapid onset of action, short duration of action.  Rapidly metabolized in liver (less hangover).  Minimal CVS and respiratory depressant effects.  Involuntary movements during induction (diazepam).  Postoperative nausea & vomiting.  Pain at sit of injection.  Adrenal suppression  Dissociative anesthesia (Analgesic activity, amnesic action, immobility, complete separation from the surrounding environment).  Rapid onset of action, short duration, is given IV, IM (Children).   BP & cardiac output (central sympathetic activity).   Increases plasma catecholamine levels,  ICP  Potent bronchodilator (asthmatics).  Used in (hypovolemic, shock & elderly) patients.  Post operative hallucination vivid dreams & disorientation &illusions  Risk of hypertension & cerebral hemorrhage,  ICP  Fentanyl, Alfentanil, Sufentanil, Remifentanil Rapid onset, Short duration of action, Potent analgesia. Uses Neuroleptanalgesia (Fentanyl + Droperidol ). Neuroleptanesthesia (Fentanyl+Droperidol+ nitrous oxide). Side Effects Respiratory depression, bronchospasm (wooden rigidity). Hypotension, nausea & vomiting  Contraindication 1. Head injuries. 2. Pregnancy. 3. Bronchial asthma. 4. Chronic obstructive lung diseases. 5. Hypovolemic shock (Large dose only).  Neuroleptanalgesia  A state of analgesia, sedation and muscle relaxation without loss of consciousness. used for diagnostic procedures that require cooperation of the patient. Innovar (Fentanyl + Droperidol ). Contraindicated in parkinsonism. Neuroleptanesthesia A combination of (Fentanyl + Droperidol + nitrous oxide).  EFFECTS OF INTRAVENOUS DRUGS ON CVS SYSTEM Drug Systemic BP Heart rate Propofol ↓ ↓ Thiopental Etomidate No change or slight ↓ No change Ketamine ↑ ↑  Drug Main side effects Thiopental CVS collapse and respiratory depression (Laryngospasm, bronchospasm), porphyria Etomidate Adrenocortical suppression, Excitatory effects during induction pain at site of injection, Post-operative NV Propofol CVS and respiratory depression, Excitation (involuntary movements) Pain at injection site, expensive. Ketamine Psychotomimetic effects following recovery (vivid dreams, hallucination) Postoperative nausea, vomiting ， salivation Risk of hypertension and cerebral hemorrhage Midazolam Slow induction & recovery Minimal CVS and respiratory depression Opioids Respiratory depression, Bronchospasm (wooden rigidity). Hypotension, Nausea & vomiting, Increase in ICP, Urinary retention. Fentanyl Prolongation of labor & fetal distress.  Drug Contraindications Thiopental Porphyria, severe hypotension (hypovolemic & shock patient) Chronic obstructive lung disease. Propofol CVS and respiratory depression Fentanyl Head injuries, Pregnancy, Bronchial asthma, Chronic obstructive lung diseases. Hypovolemic shock (Large dose only). Ketamine CV diseases (hypertension-stroke). Head injuries. Midazolam Respiratory patients Thank you