General Anesthesia

صفحه 1:
General -. Anesthesia Anesthesiology Lecture Series Surgery Module Level III 

صفحه 2:
Lecture Outline Principles of General Anesthesia Pharmacology in General Anesthesia Conduct of General Anesthesia iv. Complications of General Anesthesia 

صفحه 3:
General Anesthesia “General Anesthesia is a drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function maybe inpaired ‏همم‎ CEOERPL PVECTLEEI POD LECELE OF CEOOPOV/POELEEC IP. Ppproved by PO Worer of Debrries ot Ortber 2, 1999, cand exceed ‏و مه‎ OOP PRINCIPLES 

صفحه 4:
CONTINUUM OF DEPTH OF SEDATION: DEFINITION OF GENERAL ANESTHESIA AND LEVELS OF SEDATION/ANALGESIA* ero meet) ) ‏صهناد0ع5‎ CLC eee ‏رت یت‎ | Sedation) ‏رت بای‎ Purposeful Purposeful Unarousable response to _ response even with verbal or following painful tactile repeated or stimulus stimulation _painful stimulation No Intervention may Intervention intervention _be required often required required Adequate May be Frequently inadequate inadequate Usually Usually May be maintained maintained impaired Tinned) Percy errr) a Normal response to verbal stimulation Unaffected Unaffected Unaffected Responsiven ess Airway Respiratory Function Cardiovascul ar Function Opproved by BOO owe oP Dekepacs oa Oricber 12, (O08, ord cxreuded 2a Oceber 22 2 

صفحه 5:
Stages of General Anesthesia © Stage 1 (amnesia) From induction of anesthesia to loss of consciousness (loss of eyelid reflex) Pain perception threshold is not lowered. © Stage 2 (delirium/excitement) Characterized with uninhibited excitation, agitation, delirium, irregular respiration and breath holding Pupils are dilated and eyes are divergent Responses to noxious stimuli: vomiting, laryngospasm, hypertension, tachycardia, and uncontrolled movements PRINCIPLES 

صفحه 6:
Stages of General Anesthesia © Stage 3 (surgical anesthesia) characterized by central gaze, constricted pupils, and regular respirations Painful stimulation does not elicit somatic reflexes or deleterious autonomic responses. © Stage 4 (impending death/overdose) characterized by onset of apnea, dilated and nonreactive pupils, and hypotension may progress to circulatory failure PRINCIPLES 

صفحه 7:
Principles of General Anesthesia ® Minimum Alveolar Concentration (MAC) the minimum concentration necessary to prevent movement in 50% of patients in response to a surgical skin incision The lower the MAC, the more potent the agent Summary of physical properties of volatile anesthetics Sevoflura| ne 200 58.5 157 2.05 3-5 0.6 Desfluran| e 168 228 669 <0.1 0.45 Enflurane 184 56.5 175 1.8 2 lisoflurane| 184 48.5 238 1.15 0.2 1.36 lHalothane| 197 50.2 243 0.75 20 212 ۳۱۵۱۱3: ۴ [Boiling point (°C) aturated vapor ressure at 20°O IMAC in 100% 2 Po iotransformatio [Blood / gas PRINCIPLES 

صفحه 8:
Minimum Alveolar Concentration concentrations required to prevent eye opening on verbal command (50% MAC) Concentrations required to prevent movement and coughing in response to endotracheal intubation (130% MAC) Concentrations required to prevent adrenergic response to skin incision (Blockade of autonomic response) (150% MAC) concentration that blocks anterograde memory in 50% of awake patients (25% MAC) MAC awake MAC Endotrachea I Intubation MAC BAR MAC Amnesia PRINCIPLES 

صفحه 9:
Minimum Alveolar Concentration © Factor that increase/decrease PRINCIPLES 

صفحه 10:
Meyer-Overton Hypothesis © The MAC of a volatile ‏تسا‎ ‎substance is inversely proportional ‏سس‎ ‎to its lipid solubility epee + (oil:gas coefficient) a or nitrous ode موتأواع کرت یت ۱۶ High MAC equals low ii 4 lipid solubility iT Witrogen Backtrack: seat MAC is inversely related to potency (high MAC equals low potency) 

صفحه 11:
Meyer-Overton Hypothesis © Correlation between lipi solubility with potency onset of anesthesia occt when sufficient molecule of the agent have dissolved in the cell's lip membranes High lipid solubility eque high potency (and low Summary of physical properties of volatile anesthetics Sevoflura| ne 200 38.5) 157 2.05 0.66 3-5 06 Desfluran| e 168 22.8 669 6 25 201 0.45 Halothan|Isofluran|Enfluran e e e 197 121 184 502 48.5) 565 243 238 175 075 9 18 0.29 0.56 0.57 20 0.2 2 3 1.36 Tor Molecular weight Boiling point (“C) at'd vapor pressure 0 IMAC in 100% 0, IMAC in 70% N20 Biotransformation Blood / gas PRINCIPLES 

صفحه 12:
Meyer-Overton Hypothesis Factors Affecting the Meyer - Overton Hypothesis Convulsant properties Halogenation results in decreased anesthetic potency and appearance of convulsant activity Specific Receptors e.g. opioid receptors there is reduction of MAC by opioids » 0 ‏عمل ممع لع مراع‎ an alpha-2- agonist, results in marked reduction in MAC Hydrophilic site of action correlation between ability to form clathrates and anesthetic potency Clathrates (of water) are postulized to alter membrane ion transport 

صفحه 13:
il. OVERVIEW OF PHARMACOLOGIC AGENTS USED IN GENERAL ANESTHESIA Inhaled Anesthetics Intravenous induction Agents Neuromuscular Blocking Agents Opioids Benzodiazepines Anticholinergic agents Anticholinesterases 

صفحه 14:
Inhalational Agents © Used in the induction and maintenance of anesthesia Halogenated alkane or ether- derived compounds Nitrous oxide (N,O; laughing gas) is the only inorganic anesthetic gas in clinical use Produce dose-dependent systemic effects Associated with Malignant Hyperthermia 

صفحه 15:
Inhalational Agents ‏الست‎ eo 1 Nitrous Oxide Alters methionine synthetase production; polyneuropathy, teratogenic effects Chloroform Hepatic toxicity; fatal cardiac arrhythmia Halothane Associated in hepatitis, malignant hyperthermia Methoxyflura Fluoride nephrotoxicity ne Enflurane Induce epileptiform EEG changes Isoflurane Coronary steal Sevoflurane Compound A found to be nephrotoxic Desflurane Produces more Carbon monoxide with ۲ ‏رب‎ _.«eagtion to CO2 absorbent ‎of Derotevetry, ODDS‏ طح لعا ‎oP Crary, OP ed. DOE‏ | ‎PHARMACOLOGIC AGENTS 

صفحه 16:
Intravenous Induction Agents © Used as premedications, sedatives, intravenous induction agents and in the maintenance of anesthesia. © Total intravenous anesthesia (TIVA) 

صفحه 17:
Intravenous Induction Agents ® Thiopental REVIEW: Redistribution Hepatic elimination Can cause hypotension, vasodilation and cardiac depression Can precipitate bronchospasm in patients with reactive airway disease Decreases CMRO, in neuroanesthesia ۳۳ \ PHARMACOLOGIC AGENTS © ses Hs ‏عد‎ ۰ ory seh Chard Orerdeedrg 6“ ‏لب‎ 0006 acl wel downs Paluch Carer tel OD 

صفحه 18:
Intravenous Induction Agents ® Ketamine Produces dissociative state of anesthesia Only IV induction agent that increases blood pressure and heart rate Decreases bronchomotor tone May be used as sole anesthetic for ‏يت‎ ‎short procedures Produces profound amnesia and analgesia Increases intracranial pressure Produces emergence delirium and bad dreams 1 \ PHARMACOLOGIC AGENTS 

صفحه 19:
Intravenous Induction Agents © Propofol, (2,6- diisopropylphenol) Short-acting induction agent Available as oil-in-water emulsion containing soybean oil, glycerol, and egg lecithin Ideal for ambulatory surgery Can decrease blood pressure in susceptible patients Produces bronchodilatation Associated injection pain ۳۳ \ PHARMACOLOGIC AGENTS 

صفحه 20:
Intravenous Induction Agents ° Etomidate Imidazole compound Produces minimal hemodynamic changes (ideal for patients with cardiovascular disease) Produces pain on injection, abnormal muscular movements and adrenal suppression ° Midazolam A benzodiazepine (Other BZD: Diazepam, Lorazepam) 1 Because of minimal cardiovascular effects, a used for anesthesia induction ۱ Produces anxiolysis and profound amnesia Also used as a premedicant ۳۳ \ PHARMACOLOGIC AGENTS 

صفحه 21:
Opioids © Used as part of general anesthesia, and in patients receiving regional anesthesia © Produces profound analgesia and minimal cardiac depression © Cause ventilatory depression © Examples: Agonists: Morphine, Fentanyl, Meperidine Antagonists: Naloxone Agonist-Antagonist: Nalbuphine, Butorphanol 1 \ PHARMACOLOGIC AGENTS 

صفحه 22:
Opioids © Uses in General Anesthesia Reduces MAC of potent inhalational agents Blunt the sympathetic response (increase in BP and HR) to direct laryngoscopy, intubation and surgical incision Provide analgesia extending into postoperative period May be used as complete anesthetics (may provide analgesia, hypnosis and analgesia) May be added in local anesthetic solutions in regional anesthesia to improve quality of analgesia PHARMACOLOGIC AGENTS 

صفحه 23:
Neuromuscular Blocking Agents ® Uses in anesthesia: Facilitates endotracheal intubation Provides muscle relaxation necessary for the conduct of surgery Types: (Review Pharmacology) DEPOLARIZING (non-competitive) AGENTS “ Succinylcholine: mimics the action of acetylcholine by depolarizing the postsynaptic membrane at the neuromuscular junction (non-competitive antagonism) NON-DEPOLARIZING | Produces reversible competitive antagonism of Ach | Maybe aminosteroid or benzylisoquinoline compounds i \ PHARMACOLOGIC AGENTS 

صفحه 24:
Neuromuscular Blocking Agents Advantages of Succinylcholine Rapid onset, short duration of action Used in rapid-sequence induction Adverse effects of Succinylcholine Bradycardia (esp. in pediatrics) Life-threatening hyperkalemia in burn patients May trigger malignant hyperthermia Myalgia (from fasciculations) and myoglobinuria Increased ICP, CBF, IOP Increased intragastric pressure Prolonged blockade in susceptible individuals (in decreased plasma cholinesterase activity, myopathies) 1 PHARMACOLOGIC AGENTS 

صفحه 25:
Neuromuscular Blocking Agents Nondepolarizing Agents Used when succinylcholine is contraindicated Choice of agent » Based on mode of excretion Hoffman degradation (atracurium, cis-atracurium) Renal Hepatic Based on duration of action Short acting: Mivacurium Intermediate: Atracurium, Rocuronium Long-acting: Pancuronium i \ PHARMACOLOGIC AGENTS 

صفحه 26:
Neuromuscular Blocking Agents Concerns in anesthesia Paralysis can mask signs of inadequate anesthesia Higher doses required for intubation than for surgical relaxation Other drugs can potentiate effects of non- depolarizing agents Variable individual responses Residual blockade may result to postoperative problems TOF monitoring Clinical assessment i \ PHARMACOLOGIC AGENTS 

صفحه 27:
Anticholinergics ® competitively inhibits the action of acetylcholine at muscarinic receptors with little or no effect at nicotinic receptors. © Examples: Atropine*, Scopolamines, Glycopyrrolate* * Uses in anesthesia: Amnesia and Sedation’ Antisialogogue effect s** Tachycardia* Bronchodilation* PHARMACOLOGIC AGI 19 

صفحه 28:
Anticholinesterases Inactivate acetylcholinesterase by reversibly binding to the enzyme increasing the amount of acetylcholine available to compete with the nondepolarizing agent Increases acetylcholine at both nicotinic and muscarinic receptors Muscarinic side effects can be blocked by administration of atropine or glycopyrrolate Examples: edrophonium, neostigmine, pyridostigmine, physostigmine Use in anesthesia: reversal of neuromuscular PHARMACOLOGIC AGENTS 

صفحه 29:
GENERAL ANESTHESIA Induction Techniques Intubation Maintenance Emergence and Extubation CONDUCT OF GENERAL ANESTHESIA 

صفحه 30:
Patient Monitoring in Anesthesia CONDUCT OF GENERAL ANESTHESIA Routine ‏کیت‎ © Pulse oximetry ©» Foley catheter © Automated BP ® Arterial catheter ‎Ventral venous catheter‏ ® ی ‎® Capnography © Pulmonary artery ‎© Oxygen analyzer catheter ‎» Ventilator pressure ® Precordial doppler monitor © Transesophageal ‎© Thermometry Echocardiography ‎© Esophageal Doppler ‎Esophageal and Precordial Stethoscope 

صفحه 31:
Airway Examination ® Mallampati Score The patient is asked to maximally open his mouth and protrude his tongue while in the sitting position Sa Chee 0 (Pavetd plore, ‏ا‎ sero Okes O Qiads coushed by torque boo Okes 9 Ody 20 Pt ced hard poate viewatzed Chess P| Oud hard poke: 

صفحه 32:
Airway Examination ®@ /nterdental Distance (3) Measures the distance between the 2 incisors, with the mouth fully opened ® Thyromental Distance (3) Measures the distance between the chin (mentum) and the thyroid cartilage °® Thyrohyoid Distance (2) Measures the distance between the hyoid and the thyroid cartilage 2 a uy 5 ‏اك‎ ‎5 ‎5 ‎3 ‎= | 0 

صفحه 33:
Airway Examination ® Bellhouse-Dore © maximal flexion and extension of the neck will identify limitations that might prevent optimal alignment of the OPL axes. Normal atlanto-occipital joint: 35 degrees of extension CONDUCT OF GENERAL ANESTHESIA 

صفحه 34:
Strategies in General Anesthesia ® Questions to ask prior to conduct of anesthesia: Is the patient's condition or scheduled surgery require additional monitoring techniques? Does the patient have conditions that contraindicate certain drugs ‎endotracheal intubation required?‏ وا ‎Are there anticipated difficulties in oral translaryngeal intubation? ‎Are NMBs required during surgery? ‎Are there special surgical requirements that mandate use of or avoidance of specific interventions? (e.g. NMBs) ‎Is substantial blood loss or fluid shifts anticipated? ‎CONDUCT OF GENERAL ANESTHESIA ‎1 ‎( 

صفحه 35:
Induction of Anesthesia ® Sequence of interventions during induction vary depending on the patient and type of surgery ® Concerns Loss of consciousness Inability to maintain a natural airway Reduction or cessation of spontaneous ventilation Use of drugs that may depress the myocardium and change vascular tone CONDUCT OF GENERAL ANESTHESIA 1 

صفحه 36:
Awake Intubation © May be supplemented with sedatives, opioids, and topical or local anesthesia ® Accomplished via “blind” nasal, fiberoptic bronchoscopy, and direct visualization CONDUCT OF GENERAL / 

صفحه 37:
Awake Intubation ©» Nasal Intubation Endotracheal tube (ET) is inserted through the nose and guided into the tracheal by listening to the transmitted breath sound © Fiberoptic intubation Passing an ET through the nose or _ mouth into the pharynx, then passing a bronchoscope through the tube. The larynx and the trachea are visualized and the ET is thread over the bronchoscope 1 CONDUCT OF GENERAL ANESTHESIA 

صفحه 38:
06 لاب و۳ +|- 10 ‏بصن‎ or BLO 1 اه سل Orestes reuse ped oot ] ‏صمحم لام حي‎ Yee? Patent & quea DOO یه له مها بسا CONDUCT OF GENERAL ANESTHESIA 

صفحه 39:
Intravenous Induction ® Disadvantages Spontaneous ventilation is abolished without certainty that patient can be manually ventilated Endotracheal intubation is performed while the patient is lightly anesthetized, precipitating hypertension, tachycardia, or bronchospasm CONDUCT OF GENERAL ANESTHESIA ( 

صفحه 40:
Inhalational Induction va Pace Ook + la obfures (ikea) +4 poteaty of severe rk oP browkespew + Ghent Primaxhery + OPPrad oni Prevareutos (IDO% Og) 41-10 operd or BLO 8 + Onkale ‏جات سم( من نمی‎ ممت 7 وی ‎Orestevelyst‏ ‏حول بای سا 1۳ Yer? Puted & wea DOO T a ‏ال‎ ‎oad Tetbatod‏ مورا با ‎ ‎ ‎Option ‎ ‎ ‎۳۳ ‎CONDUCT OF GENERAL ANESTHESIA ‎( ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ 

صفحه 41:
x B inhalational Induction © May be used in children and cooperative adults ° Disadvantages Depending on the induction agent, patients progress from the awake state to surgical level of anesthesia. Stage 2 anesthesia prodispose the patient to laryngospasm, vomiting and aspiration © Agents used for Inhalational induction: Sevoflurane Halothane 5 i & 0 9 ۲ > 5 0 

صفحه 42:
Rapid Sequence Induction © Indicated for patients at high risk for acid aspiration © Examples Obese patients Pregnant patients History of gastroesophageal reflux disease Patients with bowel ae Golick's Qacewer: ‎i‏ اه له با مه حور و ساره با لاو ‎Prov thee savers‏ مهم صرح و رون ‎to the‏ ‎ ‎STHESIA ‎3 ‎CONDUCT OF GENERAL Af 

صفحه 43:
Lt = Rapid Sequence Induction ‎3-person*‏ (0 100096) يم ‎technique |‏ ‎ ‎Oxkonietratos P rapid-artory TO ‏سل‎ acpi” ‎ ‎ae ‎ ‎ ‎CONDUCT OF GENERAL 4 1 ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ 

صفحه 44:
Combined intravenous and inhalational anesthesia ©» Agents are combined to gain advantage of smooth and rapid hypnosis but still permit establishment of deep level of inhalational anesthesia prior to airway instrumentation 1 CONDUCT OF GENERAL ANESTHESIA 

صفحه 45:
Combined Intravenous and Inhalational Anesthesia Prevareadios (IDO% Oo) 41-10 ‏ممه‎ or BLO 0 سلاو <ن مس وه سل قممیت وی سوق مان 1 Yor? Puted & wea OOO vy /ESTHESIA ee | CONDUCT OF GENERAL Ag Vv Overt Larxnpecopy ond Tetibatos 

صفحه 46:
Lt | A : ۰ ۲7... ۲6۵0۳۱۳۱0۷6۵۵ ۱0 Managing = Airway Obstruction © Chin tilt ©» Extension of neck | © Anterior displacement of mandible © Use of airway adjuncts (oral and nasal airway) af CONDUCT OF GENERAL Review 2” Year Airway ent Lectures 1 

صفحه 47:
Orotracheal Intubation Technique (Posiics the Patient Sniffing Position a SF Pads and Pillows Opa te a ose he Gweep daira ‏سوم‎ Prow nh ohh ‏ساملا را‎ ره و اج موه لس لا ‎Otnrdize‏ ا CONDUCT OF GENERAL ANESTHESIA 

صفحه 48:
Orotracheal Intubation Technique (esert the eadotcacked tube Pro ‏مه با‎ of the wou: طنط سس ‎he tbe‏ مه CONDUCT OF GENER. 

صفحه 49:
Confirmation of Successful Endotracheal Intubatio Direct visualization of the ET tube passing though the vocal cords. Carbon dioxide in exhaled gases (documentation of end-tidal CO?in at least three consecutive breaths). Maintenance of arterial oxygenation. Bilateral breath sounds. Absence of air movement during epigastric auscultation. Condensation (fogging) of water vapor in the tube during exhalation. Refilling of reservoir bag during exhalation. Chest x-ray: the tip of ET tube should be between the carina and thoracic inlet or approximately at the level of the aortic notch or at the level of TS. ESTHESIA CONDUCT OF GENERAL 0 

صفحه 50:
Maintenance of Anesthesia ® Goals Facilitate surgical exposure Ensure adequate amnesia Ensure adequate analgesia © Parameters used in assuring adequacy of anesthesia: Autonomic signs (BP, HR, RR) Monitoring of Neuromuscular Blockade BIS Monitoring (for awareness) ۳ CONDUCT OF GENERAL ANESTHESIA 

صفحه 51:
Maintenance of Aneacthacia © PTROTCOLE ۵00۵0100۵71۵0۵ 06: *IV opioids (e.g. fentanyl) “IV sedative-hypnotics (e.g. midazolam) + 02+volatile agent + Nitrous oxide © 0۲۱۵۵۵۵0۵0۵00110 ۵۵: ۰۱۷ opioids ۰۱۷ sedative-hypnotics ٠ 02+ Nitrous oxide © TOTO ۵۵۵ ۵۵۵16: )10©( ۰۱۷ sedative-hypnotics (e.g. propofol) via infucian ar TCH + WOOs (a prtetts requires Rivbutcad omer rekmvcio) CONDUCT OF GENERAL ANESTHESIA 

صفحه 52:
Emergence and Extubation “ Emergence and extubation requires the knowledge and experience with the pharmacokinetic and pharmacodynamic principles that underlie the elimination of inhalational and intravenous agents and that govern the reversal of neuromuscular blockade.” CONDUCT OF GENERAL ANESTHESIA 1 

صفحه 53:
Emergence and Extubation ° Parameters for Extubation: Patient follows commands Active spontaneous respiration Ability to protect the airway (reflexes) ©» Deep extubation Used in patients at risk for bronchospasm with stimulation of the trachea during emergence from anesthesia CONDUCT OF GENERAL ANESTHESIA 

صفحه 54:
Criteria for Extubation awake and responsive patient stable vital signs reversal of paralysis good hand grip sustained head lift for five seconds Negative inspiratory force > -20 mmHg vital capacity >15 ml/kg Oter Oowerw: ‏عاص مهب‎ | Orury vars CONDUCT OF GENERA 

صفحه 55:
© Subjective Clinical Criteria: Follows commands Clear oropharynx/hypopharynx (e.g. no active bleeding, secretions cleared) Intact gag reflex Sustained head lift for 5 seconds, sustained hand grasp Adequate pain control Minimal end-expiratory concentration of inhaled anesthetics ۰ Objective Criteria: Vital capacity: 210 mL/kg Peak voluntary negative inspiratory pressure: >20 em H20 Tidal volume >6 ec/kg ‘Sustained tetanic contraction (5 sec) T1774 ratio >0.7 Alveolar-Arterial Pac2 gradient (on F102 of 2.0): <350 mm Hga Dead space to tidal volume ratio: <0.6a 

صفحه 56:
>» COMPLICATIONS OF GENERAL ANESTHESIA 

صفحه 57:
Complications of General Anesthesia INDUCTION derdvidval variable respoase to deuce Depression of he COG | respiratory | LL (OF GA. COMPLICATIONS ( 

صفحه 58:
موب بوسه ۱ امس لت مت ما *Posttotubatica koorseuess ced sore trot “OP Picul totubotion Drocked Tube Prstioctey *adobrouchtd Iotubatica ‏مها لوط‎ ‏ار مس علطم‎ INTUBATION ۳ OF, COMPLIC. ۱710/۷5 6 

صفحه 59:
سوم ططلبو() الم ۱ ‎Qepressio of the COG | respirciory |‏ وت متس هت ماس ۶اه او ‎Jeadequate‏ عجمجوب؟) MAINTENANCE SSIES) TIONS(OF GA. COMPLICA 

صفحه 60:


General Anesthesia Anesthesiology Lecture Series Surgery Module Level III Lecture Outline I. II. III. IV. Principles of General Anesthesia Pharmacology in General Anesthesia Conduct of General Anesthesia Complications of General Anesthesia PRINCIPLES General Anesthesia “General Anesthesia is a drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function OF may beOFimpaired.” CONTINUUM DEPTH SEDATION: DEFINITION OF GENERAL ANESTHESIA AND LEVELS OF SEDATION/ANALGESIA*. Approved by ASA House of Delegates on October 13, 1999, and amended on October 27, 2004 CONTINUUM OF DEPTH OF SEDATION: DEFINITION OF GENERAL ANESTHESIA AND LEVELS OF SEDATION/ANALGESIA* Minimal Sedation Analgesi a Moderate Sedation (Conscious Sedation) Deep Sedation General Anesthesia / Analgesia Responsiven ess Normal response to verbal stimulation Purposeful response to verbal or tactile stimulation Purposeful response following repeated or painful stimulation Unarousable even with painful stimulus Airway Unaffected No intervention required Intervention may be required Intervention often required Respiratory Function Unaffected Adequate May be inadequate Frequently inadequate (Anxiolysis) Cardiovascul Unaffected Usually Usually May be ar Function maintained maintained impaired Approved by ASA House of Delegates on October 13, 1999, and amended on October 27, 2004 Stages of General Anesthesia  Stage 1 (amnesia) PRINCIPLES ◦ From induction of anesthesia to loss of consciousness (loss of eyelid reflex) ◦ Pain perception threshold is not lowered.  Stage 2 (delirium/excitement) ◦ Characterized with uninhibited excitation, agitation, delirium, irregular respiration and breath holding ◦ Pupils are dilated and eyes are divergent ◦ Responses to noxious stimuli: vomiting, laryngospasm, hypertension, tachycardia, and uncontrolled movements Morgan, et al. Clinical Anesthesiology, 4 th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Stages of General Anesthesia  Stage 3 (surgical anesthesia) PRINCIPLES ◦ characterized by central gaze, constricted pupils, and regular respirations ◦ Painful stimulation does not elicit somatic reflexes or deleterious autonomic responses.  Stage 4 (impending death/overdose) ◦ characterized by onset of apnea, dilated and nonreactive pupils, and hypotension ◦ may progress to circulatory failure Morgan, et al. Clinical Anesthesiology, 4 th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Principles of General Anesthesia  Minimum Alveolar Concentration (MAC) PRINCIPLES ◦ the minimum concentration necessary to prevent movement in 50% of patients in response to a surgical skin incision ◦ The lower the MAC, the more potent the agent Summary of physical properties of volatile anesthetics Halothane Isoflurane Enflurane Desfluran Sevoflura e ne Molecular weight 197 184 184 168 200 Boiling point (°C) 50.2 48.5 56.5 22.8 58.5 Saturated vapor 243 238 175 669 157 pressure at 20°C MAC in 100% O2 0.75 1.15 % 20 0.2 Biotransformatio Morgan, et al. Clinical Anesthesiology, 4 th ed. 2006 n Ezekiel. Handbook of Anesthesiology, 2005 AnesthesiaUK.com Blood / gas 2.2 1.36 1.8 6 2.05 2 <0.1 3-5 1.91 0.45 0.6 Minimum Alveolar Concentration MAC awake concentrations required to prevent eye opening on verbal command (50% MAC) PRINCIPLES MAC Concentrations required to prevent Endotrachea movement and coughing in response l Intubation to endotracheal intubation (130% MAC) MAC BAR Concentrations required to prevent adrenergic response to skin incision (Blockade of autonomic response) (150% MAC) MAC Amnesia concentration that blocks anterograde memory in 50% of awake patients (25% MAC) Morgan, et al. Clinical Anesthesiology, 4 th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Minimum Alveolar Concentration PRINCIPLES Factor that increase/decrease Meyer-Overton Hypothesis  The MAC of a volatile substance is inversely proportional to its lipid solubility (oil:gas coefficient) PRINCIPLES ◦ High MAC equals low lipid solubility Backtrack: ◦ MAC is inversely related to potency (high MAC equals low potency) Meyer-Overton Hypothesis  Correlation between lipid solubility with potency PRINCIPLES ◦ onset of anesthesia occurs when sufficient molecules of the agent have dissolved in the cell's lipid membranes ◦ High lipid solubility equals high potency (and low MAC) of physical properties of volatile anesthetics Summary Halothan Isofluran Enfluran Desfluran Sevoflura e e e e ne Molecular weight Boiling point (°C) Sat’d vapor pressure 20°C 197 50.2 243 184 48.5 238 184 56.5 175 168 22.8 669 200 58.5 157 MAC in 100% O2 0.75 1.15 1.8 6 2.05 MAC in 70% N2O % Biotransformation Blood / gas 0.29 20 2.2 0.56 0.2 1.36 0.57 2 1.91 2.5 <0.1 0.45 0.66 3-5 0.6 Meyer-Overton Hypothesis Factors Affecting the Meyer - Overton Hypothesis  Convulsant properties ◦ Halogenation results in decreased anesthetic potency and appearance of convulsant activity  Specific Receptors ◦ e.g. opioid receptors ◦ there is reduction of MAC by opioids  Dexmedetomidine ◦ an alpha-2- agonist, results in marked reduction in MAC  Hydrophilic site of action ◦ correlation between ability to form clathrates and anesthetic potency ◦ Clathrates (of water) are postulized to alter membrane ion transport II. OVERVIEW OF PHARMACOLOGIC AGENTS USED IN GENERAL ANESTHESIA • • • • • • • Inhaled Anesthetics Intravenous induction Agents Neuromuscular Blocking Agents Opioids Benzodiazepines Anticholinergic agents Anticholinesterases PHARMACOLOGIC AGENTS Inhalational Agents      Used in the induction and maintenance of anesthesia Halogenated alkane or etherderived compounds Nitrous oxide (N2O; laughing gas) is the only inorganic anesthetic gas in clinical use Produce dose-dependent systemic effects Associated with Malignant Hyperthermia Examples: Ether Halothane Methoxyflurane Enflurane Isoflurane Sevoflurane Desflurane Nitrous Oxide Xenon PHARMACOLOGIC AGENTS Inhalational Agents Agent Adverse Systemic Effects Nitrous Oxide Alters methionine synthetase production; polyneuropathy, teratogenic effects Chloroform Hepatic toxicity; fatal cardiac arrhythmia Halothane Associated in hepatitis, malignant hyperthermia Methoxyflura ne Fluoride nephrotoxicity Enflurane Induce epileptiform EEG changes Isoflurane Coronary steal Sevoflurane Compound A found to be nephrotoxic Desflurane Produces more Carbon monoxide with reaction to CO2 absorbent Morgan, et al. Clinical Anesthesiology, 4 ed. 2006 th Ezekiel. Handbook of Anesthesiology, 2005 Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 PHARMACOLOGIC AGENTS Intravenous Induction Agents  Used as premedications, sedatives, intravenous induction agents and in the maintenance of anesthesia.  Total intravenous anesthesia (TIVA) Examples: Barbiturates (Thiopental) Benzodiazepines (Midazolam) Ketamine Etomidate Propofol Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 PHARMACOLOGIC AGENTS Intravenous Induction Agents Thiopental ◦ REVIEW: Redistribution ◦ Hepatic elimination ◦ Can cause hypotension, vasodilation and cardiac depression ◦ Can precipitate bronchospasm in patients with reactive airway disease ◦ Decreases CMRO2 in neuroanesthesia www.3dchem.com Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004 Ketamine ◦ Produces dissociative state of anesthesia ◦ Only IV induction agent that increases blood pressure and heart rate ◦ Decreases bronchomotor tone ◦ May be used as sole anesthetic for short procedures ◦ Produces profound amnesia and analgesia ◦ Increases intracranial pressure ◦ Produces emergence delirium and bad dreams Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004 www.3dchem.com www.bedfordlabs.com PHARMACOLOGIC AGENTS Intravenous Induction Agents Propofol, (2,6diisopropylphenol) ◦ Short-acting induction agent ◦ Available as oil-in-water emulsion containing soybean oil, glycerol, and egg lecithin ◦ Ideal for ambulatory surgery ◦ Can decrease blood pressure in susceptible patients ◦ Produces bronchodilatation ◦ Associated injection pain Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004 jchemed.chem.wisc.edu www.psimeds.com PHARMACOLOGIC AGENTS Intravenous Induction Agents PHARMACOLOGIC AGENTS Intravenous Induction Agents  Etomidate ◦ Imidazole compound ◦ Produces minimal hemodynamic changes (ideal for patients with cardiovascular disease) ◦ Produces pain on injection, abnormal muscular movements and adrenal suppression  www.bedfordlabs.com Midazolam ◦ A benzodiazepine (Other BZD: Diazepam, Lorazepam) ◦ Because of minimal cardiovascular effects, used for anesthesia induction ◦ Produces anxiolysis and profound amnesia ◦ Also used as a premedicant Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Townsend, et al. Sabiston’s Textbook of Surgery, 17 th ed. 2004 www.bedfordlabs.com PHARMACOLOGIC AGENTS Opioids  Used as part of general anesthesia, and in patients receiving regional anesthesia  Produces profound analgesia and minimal cardiac depression  Cause ventilatory depression  Examples: (REVIEW CLASSIFICATION OF OPIOIDS AND RECEPTORS) ◦ Agonists: Morphine, Fentanyl, Meperidine ◦ Antagonists: Naloxone ◦ Agonist-Antagonist: Nalbuphine, Butorphanol Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Townsend, et al. Sabiston’s Textbook of Surgery, 17 th ed. 2004 PHARMACOLOGIC AGENTS Opioids  Uses in General Anesthesia ◦ Reduces MAC of potent inhalational agents ◦ Blunt the sympathetic response (increase in BP and HR) to direct laryngoscopy, intubation and surgical incision ◦ Provide analgesia extending into postoperative period ◦ May be used as complete anesthetics (may provide analgesia, hypnosis and analgesia) ◦ May be added in local anesthetic solutions in regional anesthesia to improve quality of analgesia Townsend, et al. Sabiston’s Textbook of Surgery, 17 th ed. 2004 PHARMACOLOGIC AGENTS Neuromuscular Blocking Agents  Uses in anesthesia:  Facilitates endotracheal intubation  Provides muscle relaxation necessary for the conduct of surgery ◦ Types: (Review Pharmacology)  DEPOLARIZING (non-competitive) AGENTS  Succinylcholine: mimics the action of acetylcholine by depolarizing the postsynaptic membrane at the neuromuscular junction (non-competitive antagonism)  NON-DEPOLARIZING  Produces reversible competitive antagonism of Ach  Maybe aminosteroid or benzylisoquinoline compounds Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Townsend, et al. Sabiston’s Textbook of Surgery, 17 th ed. 2004 PHARMACOLOGIC AGENTS Neuromuscular Blocking Agents ◦ Advantages of Succinylcholine ◦ Rapid onset, short duration of action ◦ Used in rapid-sequence induction ◦ Adverse effects of Succinylcholine ◦ ◦ ◦     www.buyemp.com Bradycardia (esp. in pediatrics) Life-threatening hyperkalemia in burn patients May trigger malignant hyperthermia Myalgia (from fasciculations) and myoglobinuria Increased ICP, CBF, IOP Increased intragastric pressure Prolonged blockade in susceptible individuals (in decreased plasma cholinesterase activity, myopathies) th Morgan, et al. Clinical Anesthesiology, 4 ed. 2006 Townsend, et al. Sabiston’s Textbook of Surgery, 17 th ed. 2004 PHARMACOLOGIC AGENTS Neuromuscular Blocking Agents ◦ Nondepolarizing Agents ◦ Used when succinylcholine is contraindicated ◦ Choice of agent ◦ Based on mode of excretion ◦ Hoffman degradation (atracurium, cis-atracurium) ◦ Renal ◦ Hepatic ◦ Based on duration of action ◦ Short acting: Mivacurium ◦ Intermediate: Atracurium, Rocuronium ◦ Long-acting: Pancuronium Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 PHARMACOLOGIC AGENTS Neuromuscular Blocking Agents ◦ Concerns in anesthesia ◦ Paralysis can mask signs of inadequate anesthesia ◦ Higher doses required for intubation than for surgical relaxation ◦ Other drugs can potentiate effects of nondepolarizing agents ◦ Variable individual responses ◦ Residual blockade may result to postoperative problems ◦ TOF monitoring ◦ Clinical assessment Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 PHARMACOLOGIC AGENTS Anticholinergics  competitively inhibits the action of acetylcholine at muscarinic receptors with little or no effect at nicotinic receptors.  Examples: ◦ Atropine*, Scopolamine§, Glycopyrrolate¤  Uses ◦ ◦ ◦ ◦ in anesthesia: Amnesia and Sedation§ Antisialogogue effect §*¤ Tachycardia* Bronchodilation* Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 www.ci.springfield.or.us PHARMACOLOGIC AGENTS Anticholinesterases      Inactivate acetylcholinesterase by reversibly binding to the enzyme increasing the amount of acetylcholine available to compete with the nondepolarizing agent Increases acetylcholine at both nicotinic and muscarinic receptors Muscarinic side effects can be blocked by administration of atropine or glycopyrrolate Examples: edrophonium, neostigmine, pyridostigmine, physostigmine Use in anesthesia: reversal of neuromuscular blockade www.comparestoreprices.co.uk Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA GENERAL ANESTHESIA • • • • Induction Techniques Intubation Maintenance Emergence and Extubation CONDUCT OF GENERAL ANESTHESIA Patient Monitoring in Anesthesia Routine Specialized  Pulse oximetry  Foley catheter  Automated BP ECG Capnography Oxygen analyzer Ventilator pressure monitor Thermometry  Arterial catheter Ventral venous catheter Pulmonary artery catheter            Precordial doppler Transesophageal Echocardiography Esophageal Doppler Esophageal and Precordial Stethoscope Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Airway Examination  Mallampati Score ◦ The patient is asked to maximally open his mouth and protrude his tongue while in the sitting position www.acilveilkyardim.com Class 1 Faucial pillars, uvula, soft palate seen Class 2 Uvula masked by tongue base Class 3 Only soft and hard palate visualized Class 4 Only hard palate CONDUCT OF GENERAL ANESTHESIA Airway Examination  Interdental Distance (3) ◦ Measures the distance between the 2 incisors, with the mouth fully opened  Thyromental www.unige.ch Distance (3) ◦ Measures the distance between the chin (mentum) and the thyroid cartilage www.emedicine.com  Thyrohyoid Distance (2) ◦ Measures the distance between the hyoid and the thyroid cartilage kvyouth.blogspot.com CONDUCT OF GENERAL ANESTHESIA Airway Examination Bellhouse-Dore ◦ maximal flexion and extension of the neck will identify limitations that might prevent optimal alignment of the OPL axes. www.emedicine.com Normal atlanto-occipital joint: 35 degrees of extension CONDUCT OF GENERAL ANESTHESIA Strategies in General Anesthesia  Questions to ask prior to conduct of anesthesia: ◦ Is the patient’s condition or scheduled surgery require additional monitoring techniques? ◦ Does the patient have conditions that contraindicate certain drugs ◦ Is endotracheal intubation required? ◦ Are there anticipated difficulties in oral translaryngeal intubation? ◦ Are NMBs required during surgery? ◦ Are there special surgical requirements that mandate use of or avoidance of specific interventions? (e.g. NMBs) ◦ Is substantial blood loss or fluid shifts anticipated? Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Induction of Anesthesia  Sequence of interventions during induction vary depending on the patient and type of surgery  Concerns ◦ ◦ ◦ ◦ Loss of consciousness Inability to maintain a natural airway Reduction or cessation of spontaneous ventilation Use of drugs that may depress the myocardium and change vascular tone Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Awake Intubation  May be supplemented with sedatives, opioids, and topical or local anesthesia  Accomplished via “blind” nasal, fiberoptic bronchoscopy, and direct visualization Indications: •inadequate mouth opening •facial trauma •cervical spine injury •chronic cervical spine disease •lesions in the upper airway www.pbase.com picasaweb.google.com Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Awake Intubation  Nasal Intubation ◦ Endotracheal tube (ET) is inserted through the nose and guided into the tracheal by listening to the transmitted breath sound groups.msn.com  Fiberoptic intubation ◦ Passing an ET through the nose or mouth into the pharynx, then passing a bronchoscope through the tube. The larynx and the trachea are visualized and the ET is thread over the bronchoscope www.ispub.com Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Intravenous Induction Preoxygenation with 100% oxygen +/- IV opioid or BZD Administration of rapid-acting IV induction agents Anesthesiologist ensures patient can be manually ventilated Yes? Patient is given NMB Direct Laryngoscopy and Intubation tumj.tums.ac.ir Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Intravenous Induction  Disadvantages ◦ Spontaneous ventilation is abolished without certainty that patient can be manually ventilated ◦ Endotracheal intubation is performed while the patient is lightly anesthetized, precipitating hypertension, tachycardia, or bronchospasm Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Inhalational Induction Preoxygenation (100% O2) +/- IV opioid or BZD O2 + Volatile agent via face mask Anesthesiologist ensures patient can be manually ventilated Option Option  Yes? Patient is given NMB Direct Laryngoscopy and Intubation General Anesthesia via Face Mask  In children (induction) In patients at severe risk of bronchospasm • Short Procedures • Difficult airway • • Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Inhalational Induction   May be used in children and cooperative adults Disadvantages ◦ Depending on the induction agent, patients progress from the awake state to surgical level of anesthesia. ◦ Stage 2 anesthesia prodispose the patient to laryngospasm, vomiting and aspiration  www.cuhk.edu.hk Agents used for Inhalational induction: ◦ Sevoflurane ◦ Halothane Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Rapid Sequence Induction   Indicated for patients at high risk for acid aspiration Examples ◦ Obese patients ◦ Pregnant patients ◦ History of gastroesophageal reflux disease ◦ Patients with bowel obstruction www.johnshopkins.org Sellick’s Maneuver: pressure on the cricoid cartilage to occlude the esophagus, thus preventing passive regurgitation from the stomach to the pharynx Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Rapid Sequence Induction Preoxygenation (100% O2) Administration of rapid-acting IV induction agents* 3-person* technique SELLICK’S MANEUVER* Succinylcholine IV www.ispub.com Patient is NOT ventilated Direct Laryngoscopy and Intubation* Other concerns: Consequences of difficult intubation and hypoxia Confirm ET placement Cricoid Pressure Removed Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Combined intravenous and inhalational anesthesia  Agents are combined to gain advantage of smooth and rapid hypnosis but still permit establishment of deep level of inhalational anesthesia prior to airway instrumentation Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Combined Intravenous and Inhalational Anesthesia Preoxygenation (100% O2) +/- IV opioid or BZD Administration of rapid-acting IV induction agents Anesthesiologist deepens anesthesia with O2 + Volatile agent (+ N2O) via face mask Anesthesiologist ensures manual ventilation Yes? Patient is given NMB Direct Laryngoscopy and Intubation Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Techniques in Managing Airway Obstruction     Chin tilt Extension of neck Anterior displacement of mandible Use of airway adjuncts (oral and nasal airway) Use of supraglottic airway (e.g. Review LMA)2nd Year Airway Management Lectures  www.mdconsult.com www.charlydmiller.com www.cuhk.udu www.shilog.com medical-dictionary.thefreedictionary.com CONDUCT OF GENERAL ANESTHESIA Orotracheal Intubation Technique Position the Patient Sniffing Position Pads and Pillows Open the mouth Insert the laryngoscope blade Sweep the tongue from right to left Identify landmarks www.medgear.org Advance the laryngoscope blade Macintosh blade: vallecula Miller blade: epiglottis Identify and elevate the epiglottis Visualize the vocal cords and glottic opening Barash, et al. Clinical Enesthesiology,2006 www.emedicine.com emsresponder.com CONDUCT OF GENERAL ANESTHESIA Orotracheal Intubation Technique Insert the endotracheal tube from the corner of the mouth Advance the tube into the glottic opening services.epnet.com Withdraw laryngoscope blade Ventilate Confirm tube placement Inflate ET balloon cuff Secure the endotracheal tube Periodically check tube www.dhmc.org CONDUCT OF GENERAL ANESTHESIA Confirmation of Successful Endotracheal Intubation  Direct visualization of the ET tube passing though the vocal cords.  Carbon dioxide in exhaled gases (documentation of end-tidal CO2 in at least three consecutive breaths).  Maintenance of arterial oxygenation.  Bilateral breath sounds.  Absence of air movement during epigastric auscultation.  Condensation (fogging) of water vapor in the tube during exhalation.  Refilling of reservoir bag during exhalation.  Chest x-ray: the tip of ET tube should be between the carina and thoracic inlet or approximately at the level of the aortic notch or at the level of T5. Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 Ezekiel. Handbook of Anesthesiology, 2005 www.vet.uga.edu www.capnography.com www.chmeds.ac.nz www.sai.net.in www.ispub.com CONDUCT OF GENERAL ANESTHESIA Maintenance of Anesthesia  Goals ◦ Facilitate surgical exposure ◦ Ensure adequate amnesia ◦ Ensure adequate analgesia  Parameters used in assuring adequacy of anesthesia: ◦ Autonomic signs (BP, HR, RR) ◦ Monitoring of Neuromuscular Blockade ◦ BIS Monitoring (for awareness) Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004  TITRATABLE COMBINATION OF: •IV opioids (e.g. fentanyl) •IV sedative-hypnotics (e.g. midazolam) • O2+volatile agent • Nitrous oxide  NITROUS-NARCOTIC TECHNIQUE: •IV opioids •IV sedative-hypnotics • O2+ Nitrous oxide  TOTAL INTRAVENOUS ANESTHESIA: (TIVA) •IV sedative-hypnotics (e.g. propofol) via infusion or TCI + NMBs (in patients requiring intubation/muscle relaxation) • IV short-acting opioids Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Maintenance of Anesthesia CONDUCT OF GENERAL ANESTHESIA Emergence and Extubation “ Emergence and extubation requires the knowledge and experience with the pharmacokinetic and pharmacodynamic principles that underlie the elimination of inhalational and intravenous agents and that govern the reversal of neuromuscular blockade.” Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Emergence and Extubation Parameters for Extubation: ◦ Patient follows commands ◦ Active spontaneous respiration ◦ Ability to protect the airway (reflexes) Deep extubation ◦ Used in patients at risk for bronchospasm with stimulation of the trachea during emergence from anesthesia Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004 CONDUCT OF GENERAL ANESTHESIA Criteria for Extubation        awake and responsive patient stable vital signs reversal of paralysis good hand grip sustained head lift for five seconds Negative inspiratory force > -20 mmHg vital capacity >15 ml/kg Other Concerns: Aspiration risk Airway patency Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 www.pbase.com  Subjective Clinical Criteria: ◦ Follows commands ◦ Clear oropharynx/hypopharynx (e.g., no active bleeding, secretions cleared) ◦ Intact gag reflex ◦ Sustained head lift for 5 seconds, sustained hand grasp ◦ Adequate pain control ◦ Minimal end-expiratory concentration of inhaled anesthetics  Objective Criteria: ◦ Vital capacity: ≥10 mL/kg ◦ Peak voluntary negative inspiratory pressure: >20 cm H2O ◦ Tidal volume >6 cc/kg ◦ Sustained tetanic contraction (5 sec) ◦ T1/T4 ratio >0.7 ◦ Alveolar-Arterial Pao2 gradient (on FIO2 of 1.0): <350 mm Hga ◦ Dead space to tidal volume ratio: ≤0.6a Barash, Clinical Anesthesiology, 2006 COMPLICATIONS OF GENERAL ANESTHESIA COMPLICATIONS OF GA Complications of General Anesthesia INDUCTION www.achi.com Individual variable response to drugs Depression of the CNS / respiratory / cardiovascular systems Hypersensitivity reactions Problems in Ventilation: •Hypoxemia •Hypercarbia •Obstruction •Difficult ventilation Aspiration www.medvarsity.com COMPLICATIONS OF GA INTUBATION Physiologic Responses •Hypertension, Tachycardia •Laryngospasm •Bronchospasm www.resuscitations.in www.studioshanks.com Airway Trauma •Injury to teeth and airway tissues •Tracheal and laryngeal trauma •Post-intubation hoarseness and sore throat •Difficult intubation www.worldsmiles.com www.telemedi.net Tracheal Tube Positioning •Endobronchial Intubation •Esophageal Intubation •Inadequate insertion depth www.learningradiology.com COMPLICATIONS OF GA MAINTENANCE www.introtoccnursing.com www.flatrock.org.nz Individual Variable response Hypersensitivity reactions Depression of the CNS / respiratory / cardiovascular systems Inadequate depth of anesthesia Awareness EXTUBATION Aspiration Laryngospasm Airway trauma Residual Neuromuscular Blockade Delayed Emergence www.pbase.com www.wilyoth.com Others Peripheral Nerve Palsies Corneal Abrasions Good Day!