general anesthesia anesthesiology lecture series surgery module level iii
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General General AnesthesiaAnesthesiaAnesthesiology Lecture SeriesSurgery Module Level III
Lecture OutlineLecture Outline
I. Principles of General AnesthesiaII. Pharmacology in General
AnesthesiaIII. Conduct of General AnesthesiaIV. Complications of General
Anesthesia
General AnesthesiaGeneral 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 may be impaired.”
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CONTINUUM OF DEPTH OF 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
Minimal SedationAnalgesia
Moderate Sedation (Conscious Sedation)
Deep Sedation
(Anxiolysis)
General Anesthesia / Analgesia
Responsiveness 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
Cardiovascular Function
Unaffected Usually maintained Usually maintained May be impaired
CONTINUUM OF DEPTH OF SEDATION: CONTINUUM OF DEPTH OF SEDATION: DEFINITION OF GENERAL ANESTHESIA AND DEFINITION OF GENERAL ANESTHESIA AND LEVELS OF SEDATION/ANALGESIA* LEVELS OF SEDATION/ANALGESIA*
Approved by ASA House of Delegates on October 13, 1999, and amended on October 27, 2004
Stages of General Stages of General AnesthesiaAnesthesiaStage 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005
Stages of General Stages of General AnesthesiaAnesthesiaStage 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005
Principles of General Principles of General AnesthesiaAnesthesiaMinimum 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005AnesthesiaUK.com
Summary of physical properties of volatile anestheticsHalothane Isoflurane Enflurane Desfluran
eSevoflura
neMolecular weight 197 184 184 168 200 Boiling point (°C) 50.2 48.5 56.5 22.8 58.5 Saturated vapor pressure at 20°C
243 238 175 669 157
MAC in 100% O2
0.75 1.15 1.8 6 2.05
% Biotransformation
20 0.2 2 <0.1 3 - 5
Blood / gas 2.2 1.36 1.91 0.45 0.6 Oil / gas 224 98 98.5 28 47
Minimum Alveolar Minimum Alveolar ConcentrationConcentrationMAC awake
concentrations required to prevent eye opening on verbal command (50% MAC)
MAC Endotracheal Intubation
Concentrations required to prevent movement and coughing in response 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)
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005
Minimum Alveolar Minimum Alveolar ConcentrationConcentrationFactor that increase/decrease
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Meyer-Overton HypothesisMeyer-Overton Hypothesis The MAC of a volatile
substance is inversely proportional to its lipid solubility (oil:gas coefficient)◦ High MAC equals low
lipid solubility
Backtrack: ◦ MAC is inversely related
to potency (high MAC equals low potency)
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Meyer-Overton HypothesisMeyer-Overton Hypothesis Correlation between lipid
solubility with potency ◦ 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)
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Summary of physical properties of volatile anestheticsHalothan
eIsofluran
eEnfluran
e Desfluran
eSevoflura
neMolecular weight 197 184 184 168 200 Boiling point (°C) 50.2 48.5 56.5 22.8 58.5 Sat’d vapor pressure 20°C
243 238 175 669 157
MAC in 100% O2 0.75 1.15 1.8 6 2.05 MAC in 70% N2O 0.29 0.56 0.57 2.5 0.66 % Biotransformation 20 0.2 2 <0.1 3 - 5Blood / gas 2.2 1.36 1.91 0.45 0.6
Oil / gas 224 98 98.5 28 47
Meyer-Overton HypothesisMeyer-Overton HypothesisFactors 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 II. OVERVIEW OF PHARMACOLOGIC AGENTS PHARMACOLOGIC AGENTS USED IN GENERAL USED IN GENERAL ANESTHESIA ANESTHESIA
• Inhaled Anesthetics• Intravenous induction Agents• Neuromuscular Blocking Agents• Opioids• Benzodiazepines• Anticholinergic agents • Anticholinesterases
Inhalational AgentsInhalational Agents Used in the induction and
maintenance of anesthesia Halogenated alkane or ether-
derived compounds Nitrous oxide (N2O; laughing gas)
is the only inorganic anesthetic gas in clinical use
Produce dose-dependent systemic effects
Associated with Malignant Hyperthermia
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Examples:Ether HalothaneMethoxyfluraneEnfluraneIsofluraneSevofluraneDesfluraneNitrous OxideXenon
Inhalational AgentsInhalational AgentsAgent Adverse Systemic EffectsNitrous Oxide Alters methionine synthetase production;
polyneuropathy, teratogenic effects
Chloroform Hepatic toxicity; fatal cardiac arrhythmia
Halothane Associated in hepatitis, malignant hyperthermia
Methoxyflurane
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 absorbentP
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
Intravenous Induction Intravenous Induction AgentsAgentsUsed as premedications, sedatives,
intravenous induction agents and in the maintenance of anesthesia.
Total intravenous anesthesia (TIVA)
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
Examples:Barbiturates (Thiopental)Benzodiazepines (Midazolam)KetamineEtomidatePropofol
Intravenous Induction Intravenous Induction AgentsAgentsThiopental
◦ REVIEW: Redistribution◦ Hepatic elimination◦ Can cause hypotension, vasodilation and cardiac
depression ◦ Can precipitate bronchospasm in patients with
reactive airway disease
◦ Decreases CMRO2 in neuroanesthesia
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004www.3dchem.com
www.3dchem.com
Intravenous Induction Intravenous Induction AgentsAgentsKetamine
◦ 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004
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Intravenous Induction Intravenous Induction AgentsAgentsPropofol, (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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004
jchemed.chem.wisc.edu
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Intravenous Induction Intravenous Induction AgentsAgents 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)◦ Because of minimal cardiovascular effects,
used for anesthesia induction◦ Produces anxiolysis and profound amnesia◦ Also used as a premedicant
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004
www.bedfordlabs.com
www.bedfordlabs.com
OpioidsOpioidsUsed as part of general anesthesia, and in
patients receiving regional anesthesiaProduces profound analgesia and minimal
cardiac depressionCause ventilatory depressionExamples: (REVIEW CLASSIFICATION OF OPIOIDS AND
RECEPTORS)
◦ Agonists: Morphine, Fentanyl, Meperidine◦ Antagonists: Naloxone ◦ Agonist-Antagonist: Nalbuphine, Butorphanol
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004
OpioidsOpioidsUses 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
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Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004
Neuromuscular Blocking Neuromuscular Blocking AgentsAgents
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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004
Neuromuscular Blocking Neuromuscular Blocking AgentsAgents
◦ 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)
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Townsend, et al. Sabiston’s Textbook of Surgery, 17th ed. 2004
www.buyemp.com
Neuromuscular Blocking Neuromuscular Blocking AgentsAgents◦ 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
Neuromuscular Blocking Neuromuscular Blocking AgentsAgents◦ 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
AnticholinergicsAnticholinergicscompetitively 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*
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
www.ci.springfield.or.us
AnticholinesterasesAnticholinesterases 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005Townsend, et al. Sabiston, Textbook of Surgery, 17 th ed. 2004
www.comparestoreprices.co.uk
GENERAL GENERAL ANESTHESIAANESTHESIA
• Induction Techniques• Intubation• Maintenance• Emergence and Extubation
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Patient Monitoring in Patient Monitoring in AnesthesiaAnesthesiaRoutine Pulse oximetry Automated BP ECG Capnography Oxygen analyzer Ventilator pressure
monitor Thermometry
Specialized Foley catheter Arterial catheter Ventral venous catheter Pulmonary artery
catheter Precordial doppler Transesophageal
Echocardiography Esophageal Doppler Esophageal and
Precordial Stethoscope
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Airway ExaminationAirway ExaminationMallampati Score
◦ The patient is asked to maximally open his mouth and protrude his tongue while in the sitting position
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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
Airway ExaminationAirway Examination Interdental 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
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Airway ExaminationAirway ExaminationBellhouse-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
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Strategies in General Strategies in General AnesthesiaAnesthesia 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?
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Induction of AnesthesiaInduction of AnesthesiaSequence 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
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Awake IntubationAwake Intubation May be supplemented with
sedatives, opioids, and topical or local anesthesia
Accomplished via “blind” nasal, fiberoptic bronchoscopy, and direct visualization
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Indications:•inadequate mouth opening•facial trauma•cervical spine injury•chronic cervical spine disease•lesions in the upper airway
Awake IntubationAwake IntubationNasal 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
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Intravenous InductionIntravenous InductionPreoxygenation 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
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Intravenous InductionIntravenous InductionDisadvantages
◦ 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
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Inhalational InductionInhalational InductionPreoxygenation (100% O2)
O2 + Volatile agent via face mask
Anesthesiologist ensures patient can be manually
ventilated
Direct Laryngoscopy and Intubation
General Anesthesia via Face Mask
• In children (induction)• In patients at severe risk
of bronchospasm• Short Procedures• Difficult airway
Yes? Patient is given NMB
+/- IV opioid or BZD
OptionOption
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Inhalational InductionInhalational 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
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Rapid Sequence InductionRapid 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
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Sellick’s Maneuver: pressure on the cricoid cartilage to occlude the esophagus, thus preventing passive regurgitation from the stomach to the pharynx
www.johnshopkins.org
Rapid Sequence InductionRapid Sequence InductionPreoxygenation (100% O2)
Administration of rapid-acting IV induction agents*
Succinylcholine IV
Direct Laryngoscopy and Intubation*
SELLICK’S MANEUVER*
Patient is NOT ventilated
Confirm ET placement
Cricoid Pressure Removed
Other concerns: Consequences of difficult intubation and hypoxia
3-person* technique
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Combined intravenous and Combined intravenous and inhalational anesthesiainhalational 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
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Combined Intravenous and Combined Intravenous and Inhalational AnesthesiaInhalational Anesthesia
Preoxygenation (100% O2)
+/- IV opioid or BZD
Administration of rapid-acting IV induction agents
Anesthesiologist ensures manual ventilation
Direct Laryngoscopy and Intubation
Anesthesiologist deepens anesthesia with O2 + Volatile agent (+ N2O) via face mask
Yes? Patient is given NMB
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Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
Techniques in Managing Techniques in Managing Airway ObstructionAirway Obstruction Chin tilt Extension of neck Anterior displacement of
mandible Use of airway adjuncts (oral and
nasal airway) Use of supraglottic airway (e.g.
LMA)
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www.charlydmiller.com
www.mdconsult.com
Review 2nd Year Airway Management Lectures
www.shilog.com
medical-dictionary.thefreedictionary.comwww.cuhk.udu
Orotracheal Intubation Orotracheal Intubation TechniqueTechnique
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Barash, et al. Clinical Enesthesiology,2006www.emedicine.com
Position the Patient
Open the mouthInsert the laryngoscope bladeSweep the tongue from right to left
Identify landmarks
Advance the laryngoscope blade
www.medgear.org
Identify and elevate the epiglottis
Visualize the vocal cords and glottic openingemsresponder.com
Sniffing PositionPads and Pillows
Macintosh blade: valleculaMiller blade: epiglottis
Orotracheal Intubation Orotracheal Intubation TechniqueTechnique
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Insert the endotracheal tube from the corner of the mouth
Advance the tube into the glottic opening
Withdraw laryngoscope bladeVentilateConfirm tube placement
Inflate ET balloon cuff
Secure the endotracheal tube
www.dhmc.org
services.epnet.com
Periodically check tube
Confirmation of Successful Confirmation of Successful Endotracheal IntubationEndotracheal 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.
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006Ezekiel. Handbook of Anesthesiology, 2005
www.vet.uga.edu
www.capnography.comwww.chmeds.ac.nzwww.sai.net.inwww.ispub.com
Maintenance of Maintenance of AnesthesiaAnesthesiaGoals
◦ 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)
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Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
Maintenance of Maintenance of AnesthesiaAnesthesia
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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• IV short-acting opioids+ NMBs (in patients requiring intubation/muscle relaxation)
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Emergence and Emergence and ExtubationExtubation“ 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.”
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Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
Emergence and Emergence and ExtubationExtubationParameters 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
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Townsend, et al. Sabiston, Textbook of Surgery, 17th ed. 2004
Criteria for ExtubationCriteria 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
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Morgan, et al. Clinical Anesthesiology, 4th ed. 2006 www.pbase.com
Other Concerns: Aspiration riskAirway patency
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 COMPLICATIONS OF GENERAL GENERAL ANESTHESIAANESTHESIA
Complications of General Complications of General AnesthesiaAnesthesia
INDUCTION Individual variable response to drugsDepression of the CNS / respiratory / cardiovascular systemsHypersensitivity reactions
Problems in Ventilation:•Hypoxemia•Hypercarbia•Obstruction •Difficult ventilation
Aspiration
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INTUBATION
Tracheal Tube Positioning•Endobronchial Intubation•Esophageal Intubation•Inadequate insertion depth
Physiologic Responses•Hypertension, Tachycardia•Laryngospasm•Bronchospasm
Airway Trauma•Injury to teeth and airway tissues•Tracheal and laryngeal trauma•Post-intubation hoarseness and sore throat•Difficult intubation
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www.resuscitations.in
www.telemedi.net
www.studioshanks.com
www.learningradiology.com
www.worldsmiles.com
MAINTENANCE Individual Variable responseHypersensitivity reactionsDepression of the CNS / respiratory / cardiovascular systemsInadequate depth of anesthesiaAwareness
EXTUBATION
AspirationLaryngospasmAirway traumaResidual Neuromuscular BlockadeDelayed Emergence
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www.wilyoth.comwww.pbase.com
Others Peripheral Nerve PalsiesCorneal Abrasions
Good Day!