motor anatomy airway management


Published on

Published in: Health & Medicine
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

motor anatomy airway management

  1. 1. Motor system Spinal cord
  2. 2. Components of spinal motor control system • Spinal neurons • Motor unit • Muscle spindles • Golgi tendon organs
  3. 3. Upper motor neuron of extrapyramidal tract Upper motor Dorsal root neuron of ganglion cell corticospinal tract α-motor neuron in the spinal cord Neuro muscular junction α-mn is directly Muscle responsible for spindle generation of force by muscle muscle Golgi Tendon organ
  4. 4. 50 muscles of the Figure 5.28 arm innervated from spinal segments C3-T1 Page 173 Cervical Cervical cord nerves Vertebrae Muscles of the leg innervated from spinal segments L1-S3 Thoracic Thoracic nerves cord Lumbar Lumbar nerves Cauda cord equina Sacral Sacral nerves cord Coccygeal nerve
  5. 5. Cell body of White matter Gray matter efferent neuron Interneuron Cell body of afferent neuron Dorsal root Dorsal root Efferent fiber ganglion From receptors To effectors Ventral root Spinal nerve Figure 5.29 Page 174
  6. 6. Figure 5.31 Page 176 Dorsal horn (cell bodies of interneurons on which afferent neurons terminate) Central Lateral horn (cell bodies of autonomic canal efferent nerve fibers) Ventral horn (cell bodies of somatic efferent neurons)
  7. 7. Motor neuron pool of a muscle. • Those motor neurons innervating a single muscle • The motor neuron pools are segregated into longitudinal columns extending through two to four spinal segments. • The longitudinal orientation of motor neurons and their dendrites matches that of primary afferent terminals in that zone. • Thus impulses in a given afferent axon tend to be distributed to motor neurons innervating the same muscle or muscles with similar function.
  8. 8. Figure 8.15 Page 269 Spinal cord = Motor unit 1 A motor unit is one motor = Motor unit 2 neuron and the muscle = Motor unit 3 fibers it innervates
  9. 9. The size principle: the orderly recruitment of motor units • The first motor units to be activated are those with smallest motor axons; – these motor units generate the smallest contractile forces – and allow the initial contraction to be finely graded. • As more motor units are recruited, – the alpha motor neurons with progressively larger axons become involved – and generate progressively larger amounts of tension
  10. 10. Motor unit and motor neuron pool
  11. 11. Dorsal root Dorsal root ganglion Ventral root Figure 5.29 Page 174
  12. 12. Whole muscle tension depends on  • the size of the muscle,  • the extent of motor unit recruitment, • the size of each motor unit. • The number of muscle fibers varies among  different motor units. – Muscles performing refined, delicate movements  have few muscle fibers per motor unit.  – Muscles performing coarse, controlled movements  have a large number of fibers per motor unit. – The asynchronous recruitment of motor units  delays or prevents muscle fatigue.
  13. 13. • One group of motor neuron pools is located in the medial part of the ventral horn, and the other much larger group lies more laterally.
  14. 14. Somatotopic organization of spinal cord motor neuron trunk extremities α-mn: the flexors final common pathway extensor The ventral root s
  15. 15. Functional rule • The motor neurons located medially project to axial muscles (muscles of the neck and back): those located more laterally project to limb muscles (arms and legs). • Within the lateral group the most medial motor neuron pools tend to innervate the muscles of the shoulder and pelvic girdles, while motor neurons located more laterally project to distal muscles of the extremities and digits. • In addition the motor neurons innervating the extensor muscles tend to lie ventral to those innervating flexors.
  16. 16. Descending tracts Dorsal surface Lateral corticospinal Gray matter Rubrospinal Ventral corticospinal Vestibulospinal Ventral surface Figure 5.30 (1) Page 174
  17. 17. Motor neurons • Alpha motor neuron – Thick myelinated fast conducting axons – Motor end plate of extrafusal skeletal muscle fibers • Gamma motor neuron – Thin myelinated slower conducting axons – Supply the intrafusal fibers of Muscle spindles in skeletal muscles γ-static γ-dynamic
  18. 18. Spinal interneurons • Points of convergence for – most of the input of the brain descending tracts – Sensory afferents & collaterals of LMN axons • Intersegmental; same side of spinal cord • Commissural: cross midline
  19. 19. Spinal reflexes • Contribute to • Muscle tone • Body posture • Locomotion
  20. 20. Muscle spindles • Lie parallel to regular muscle fibers • contain nuclear bag and nuclear chain intrafusal muscle fibers.
  21. 21. Capsule Alpha motor neuron axon Intrafusal (spindle) muscle fibers Gamma motor neuron axon Contractile end portions of intrafusal fiber Noncontractile Secondary (flower-spray) central portion endings of afferent of intrafusal fibers fiber Primary (annulospiral) Extrafusal (“ordinary”) endings of afferent fibers muscle fibers
  22. 22. Muscle spindles • Can be stimulated by 2 ways • Stretching the entire muscle • Causing contraction of intrafusal fibers while extrafusal fibers remain at the same length.
  23. 23. Muscle spindles • Group Ia afferent fibers form primary endings on nuclear bag and chain fibers, • Group II fibers form secondary endings on nuclear chain fibers. • Dynamic motor axons end on nuclear bag fibers and static motor axons on nuclear chain fibers.
  24. 24. Muscle spindles • Primary endings demonstrate both static and dynamic responses, which signal muscle length and rate of change in muscle length. • Secondary endings demonstrate only static responses and signal only muscle length. • Motor neurons cause muscle spindles to shorten, which prevents the unloading effect of muscle contraction.
  25. 25. Golgi tendon organs • Located in the tendons of muscles and are arranged in series. • They are supplied by group Ib afferent fibers and are excited both by stretch and by contraction of the muscle (very sensitive to changes in muscle tension)
  26. 26. Extrafusal skeletal muscle fiber Spinal cord Intrafusal muscle spindle fiber Afferent input from sensory endings of muscle spindle fiber Alpha motor neuron output to regular skeletal-muscle fiber Stretch reflex pathway γ motor-neuron output to contractile end portions of spindle fiber Descending pathways coactivating α and γ motor neurons Figure 8.26 (1) Page 287
  27. 27. Relaxed muscle; spindle Contracted muscle in Contracted muscle in fiber sensitive to stretch hypothetical situation of normal situation of of muscle no spindle coactivation; spindle coactivation; slackened spindle fiber contracted spindle fiber not sensitive to stretch sensitive to stretch of of muscle muscle
  28. 28. • Nuclear bag fibers • Nuclear chain fibers • Ia fibers • Ia fibers • Show a dynamic • Show a Static response: response – Discharge most rapidly – Discharge at an while the muscle is increased rate being stretched & less throughout the period rapidly during when a muscle is sustained contraction stretched • Signal the amount of displacement Primary endings Signal Velocity and amount of change in muscle length
  29. 29. Alpha-gamma linkage  Enhancement of voluntary muscle contraction by co-activation of gamma and alpha motor neurons
  30. 30. The stretch reflex includes • a monosynaptic excitatory pathway from group Ia (and II) muscle spindle afferent fibers to a motor neurons that supply the same and synergistic muscles and • a disynaptic inhibitory pathway to antagonistic motor neurons.
  31. 31. Myotatic stretch reflex • The simplest reflex • Monosynaptic • Physiological significance: – Resting muscle tone and thus A key reflex in maintenance of posture
  32. 32. The tonic stretch reflex • Physiological significance: Resting muscle tone – Judged by the resistance that a joint offers to bending – Receptors: Ia & II from muscle spindle – Triggered by the static responses of group Ia and II afferents. – Any slight extension or flexion (during standing) will elicit a tonic stretch reflex in muscles required to oppose the movement, thus helping an individual to stand upright.
  33. 33. Phasic stretch reflex • Physiological significance: • Receptors: Ia from muscle spindle • Triggered by the dynamic responses of group Ia fibers • Enhancement of voluntary muscle contraction by co-activation of gamma and alpha motor neurons
  34. 34. Myotatic stretch reflex • Clinical significance in diagnosis of diseases – tendon jerks – muscle tone
  35. 35. Muscle stretch reflex
  36. 36. Extensor muscle of knee Muscle (quadriceps femoris) spindle Patellar tendon Alpha motor neuron Figure 8.27 Page 288
  37. 37. Inverse stretch reflex • Disynaptic (inhibitory interneuron+ α-mn ) • Inhibition of α-mn of same muscle • Receptor: Golgi tendon organ (in series with muscle fibers) • Stimulus: increase in muscle tension by – excessive stretch – excessive active muscle contraction • Result: relaxation (sudden stop in contraction) • Safety: – regulates muscle tension – protects the tendon from tearing
  38. 38. Withdrawal reflex • Polysynaptic • Protective • Painful stimulation of skin, subcutaneous tissue or muscle • Stimulation of flexorscontraction • Reciprocal innervation • Simultaneous inhibition of antagonists relaxation
  39. 39. = Inhibitory interneuron Components of a Figure 5.33 = Excitatory interneuron = Synapse reflex arc Receptor = Inhibits Page 178 = Stimulates Afferent pathway Integrating center Efferent pathway Effector organs Thermal pain receptor in finger Ascending pathway to brain Afferent Pathway Stimulus Biceps Efferent pathway (flexor) Integrating center contracts Triceps (spinal cord) (extensor) Hand relaxes withdrawn Effector organs Response
  40. 40. Crossed extensor reflex • Supporting reflex, serves to maintain posture • Polysynaptic • Irradiation of stimulation • Reciprocal innervation • Flexion and withdrawal of the painfully stimulated limb • + extension of the other limb
  41. 41. Figure 5.34 Page 179 Afferent pathway Efferent pathway Efferent pathway Integrating center Flexor (spinal cord) Extensor Extensor muscle Flexor muscle muscle contracts muscle relaxes contracts relaxes Pain Injured extremity receptor (effector organ) in heel Response Response Stimulus Opposite extremity (effector organ)
  42. 42. Upper motor Dorsal root neuron of ganglion cell Interneuron in corticospinal tract the spinal cord S Y α-motor neuron in the spinal cord Effector W U X V Receptor Z T
  43. 43. The motor control system Overview
  44. 44. The Motor system 1 • Cortex • The Corticospinal tract • Alpha motor neuron • Muscles
  45. 45. Motor Control Motor Cortex UMN Corticospinal Alpha motor tract (UMN) neuron axon, LMN Alpha motor neuron, LMN Muscle
  46. 46. Four Hierarchical Components that Control Movements • Motor systems consist of separate neural circuits that are linked. • Ultimately, whether directly or indirectly distributed, all motor processing is focused on a single target ‘the motor neuron’ constituting the ‘final common pathway’ of motor system.
  47. 47. Four Hierarchical Components that Control Movements  Spinal cord  Brainstem  Subcortical (basal nuclei, thalamus, cerebellum)  Cortical –(primary motor cortex, premotor and supplementary motor areas)
  48. 48. Motor system 2 • Cortex • corticospinal tract • Alpha motor neuron • Muscles • Two control circuits that influence the activity of corticospinal tract – Cerebellum – Basal Ganglia
  49. 49. Motor system 2 two control circuits
  50. 50. Motor system 3 • Cortex • corticospinal tract • Alpha motor neuron • Muscles • + two control circuits influence the corticospinal tract • Cerebellum and BG • The Indirect brainstem motor control centers and pathways which tonically activate the Lower Motor Neurons especially those that innervate the Axial and Antigravity muscles
  51. 51. Motor system 3
  52. 52. Upper Motor Neuron • The corticospinal tract has its main influence on LMN that innervate the muscles of the distal extremities, i.e., the hand and the foot • The corticospinal tract has collaterals that modulate the control of indirect brainstem motor centers, so that we are not as a statue opposing gravity and can move at will and have the right amount of supporting tone • When there is lesion of UMN, clinical findings are a combination of both direct + indirect effects
  53. 53. Premotor and supplementary motor Figur areas Cortical e level 8.24 Sensory areas of Primary motor cortex Page cortex 285 Subcortical level Basal nuclei Thalamus Cerebellum Brain stem Brain stem level nuclei Spinal cord level Afferent Motor neuron terminals neurons Muscle fibers Periphery Movement
  54. 54. “To move things is all that mankind can do… for such the sole executant is muscle, whether in whispering a syllable or in felling a forest”.. Charles Sherrington • The spinal cord contains certain motor programs for the generation of coordinated movements and that these programs are accessed, executed, and modified by descending commands from the brain.
  55. 55. Types of Movements • Involuntary motor acts – Reflex: the most automatic behaviors (such as reflexes-organized at spinal cord level) • Voluntary motor acts – The maintenance of position (posture) – Goal directed movements- skilled voluntary movements- organized at higher centers
  56. 56. Somatic musculature in relation to the joint they act on • Axial muscles: – For movements of the trunk • Proximal muscles (or girdle muscles) – For movements of the shoulder, elbow, pelvis and knee • Distal muscles – That move the hands, feet, and digits (fingers and toes)
  57. 57. Important aspects of hierarchical organization: • Somatotopic maps – preserved in interconnections at different levels • each hierarchical level receives information from periphery so that sensory input can modify the action of descending commands • The higher levels have capacity to control the information that reaches them, allowing or suppressing the transmission of afferent volleys through sensory relays.
  58. 58. Important aspects of hierarchical organization: • The various motor control levels are also organized in parallel: so that each level can act independently on the final common pathway. • This allows commands from higher levels either to modify or to supersede lower order reflex behavior.
  59. 59. Upper Motor Neuron Lesion
  60. 60. UMNL  loss of direct effect of UMN
  61. 61. UMNL  loss of indirect effect of UMN
  62. 62. UMNL is a combination of Loss of regulation of indirect brainstem motor control centers Loss of direct CST control of LM neurons
  63. 63. Upper Motor Neuron Lesion • Loss of distal extremity strength Loss of • Loss of distal extremity dexterity direct • Babinski sign effect • Increased tone Loss of • Hyperreflexia indirect • Clasp-knife phenomenon effect
  64. 64. UMNL on opposite side of clinical findings if lesion is above the decussation
  65. 65. UMNL on same side of clinical findings if lesion in the spinal cord after decussation
  66. 66. Figure 9: The brain of a recovered stroke patient relies on a compensatory neural pathway (dark blue) as substitution for the damaged neuralpathway (blue dashed). The cerebello-thalamo -cortical pathway (green) is “teaching” the supplementary motor area its new function, which is indicated by abnormal activity in the cerebellum and thalamus. (Freely adapted from Azari & Seitz, 2000)
  67. 67. Airway Management in the Emergency Department and ICU Mehdi Khosravi, MD Pulmonary/CCM Fellow Giuditta Angelini, MD Assistant Professor Jonathan T. Ketzler, MD Associate Professor Douglas B. Coursin, MD Professor Departments of Anesthesiology & Medicine University of Wisconsin, Madison
  68. 68. Global Assessment Assess underlying need for airway control • Duration of intubation - Nasal intubation less advantageous for potentially prolonged ventilator requirements • Permanent support - Underlying advanced intrinsic lung or neuromuscular disease • Temporary support • Anesthesia • Presence of reversible intrinsic lung or neuromuscular disease • Protection of the airway due to depressed mental status • Presence of reversible upper airway pathology • Patient care needs (e.g., transport, CT scan, etc.) • Significant comorbidities  Aspiration potential or increased respiratory secretions  Hemodynamic issues such as cardiac disease or sepsis  Renal or liver failure
  69. 69. Global Assessment Pathophysiology of the respiratory failure • Hypoxic respiratory failure - In case of hypoxic respiratory failure, different noninvasive oxygen delivery devices can be used. - The severity of hypoxia and presence or absence of underlying disease (such as COPD) will dictate the device of choice. • Hypercapnic respiratory failure - The noninvasive device of choice for hypercapnic respiratory failure is BIPAP. Assessment of above mentioned patient characteristics in conjunction with the mechanism of respiratory distress leads the clinician to proper choice and duration of invasive or noninvasive options for airway management. Code status should be clarified prior to proceeding.
  70. 70. Global Assessment Oxygenation • Respiratory rate and use of accessory muscles - Is the patient in respiratory distress? • Amount of supplemental oxygen - What is the patient’s oxygen demand? • Pulse oximeter or arterial blood gas - Is the patient physiologically capable of providing appropriate supply? Airway • Anatomy - Will this patient be difficult to intubate? • Patency - Is there a reversible anatomical cause of respiratory failure as opposed to intrinsic lung dysfunction? • Airway device in place - Is there a nasopharyngeal airway or combitube in place?
  71. 71. Oxygen Delivery Devices (In order of degree of support) Nasal Cannula • 4% increase in FiO2 for each 1 L of flow (e.g., 4 L flow = 37% or 6 L flow = 45%) Face tent • At most delivers 40% at 10-15 L flow Ventimask • Small amount of rebreathing • 8 L flow = 40%, 15 L flow = 60% Nonrebreather mask • Attached reservoir bag allows 100% oxygen to enter mask with inlet/outlet ports to allow exhalation to escape - does not guarantee 100% delivery.
  72. 72. Oxygen Delivery Devices Noninvasive Positive Pressure CPAP is a continuous positive pressure • Indicated in hypoxic respiratory failure and obstructive sleep apnea BiPAP allows for an inspiratory and expiratory pressure to support and improve spontaneous ventilation • Mainly indicated in hypercapnic respiratory failure and obstructive sleep apnea If use of noninvasive modes of ventilation does not result in improved ventilation or oxygenation in two to three hours, intubation should be considered These devices can be used if following conditions are met: • Patient is cooperative with appropriate level of consciousness • Patient does not have increased respiratory secretions or aspiration potential • Concurrent enteral feeding is contraindicated. Facilitates early extubation, especially in COPD patients Some devices allow respiratory rate to be set. Up to 10 L of oxygen can be delivered into the mask for 100% oxygen delivery. Nasal or oral (full face) mask can be used; less aspiration potential with nasal.
  73. 73. Degree of Respiratory Distress Respiratory pattern • Accessory muscle use is an indication of distress. • Rate > 30 can indicate need for more support by noninvasive positive pressure or intubation Need for artificial airway • Tongue and epiglottis fall back against posterior pharyngeal wall • Nasopharyngeal airway better tolerated Pulse oximetry • O2 saturation less than 92% on 60 - 100% oxygen can suggest the need for intubation based on whether there is anything immediately reversible which could improve ventilation. Arterial blood gas • pH < 7.3 can indicate need for more support by noninvasive positive pressure or intubation.
  74. 74. Temporizing Measures Naloxone for narcotic overdose • 40 mcg every minute up to 200 mcg with: - 45 minutes to one hour duration of action • 0.4 - 2 mg of naloxone is indicated in patients with respiratory arrest and history suggestive of narcotic overdose - There is a potential for pulmonary edema, so large dose is reserved for known overdose and respiratory arrest • Caution in patients with history of narcotic dependence • Naloxone drip can be titrated starting at half the bolus dose used to obtain an effect - Manufacturer recommended 2 mg in 500 ml of normal saline or D5 gives 0.004 mg/ml concentration
  75. 75. Temporizing Measures (cont'd) Flumazenil for benzodiazepine overdose • 0.2 mg every minute up to 1 mg • Caution in patients with history of benzodiazepine or alcohol dependence • Caution in patients with history of seizure disorder as it will decrease the seizure threshold Artificial airway for upper airway obstruction in patients with oversedation • May be necessary in patients with sleep apnea despite judicious sedation 100% oxygen and maintenance of spontaneous ventilation in patients with pneumothorax • Washout of nitrogen may decrease size of pneumothorax • Positive pressure may cause conversion to tension pneumothorax
  76. 76. Oral/Nasal Airways
  77. 77. Indications for Intubation Depressed mental status • Head trauma patients with GCS 8 or less is an indication for intubation - Associated with increased intracranial pressure - Associated with need for operative intervention - Avoid hypoxemia and hypercarbia which can increase morbidity and mortality • Drug overdose patients may require 24 - 48 hours airway control. Upper airway edema • Inhalation injuries • Ludwig’s angina • Epiglottitis
  78. 78. Underlying Lung Disease Chronic obstructive lung disease • Application of controlled ventilation may interfere with complete exhalation, overdistend alveoli, and impair right heart and pulmonary venous return. Pulmonary embolus • Pulmonary artery and right ventricle already have high pressure and dependent on preload • Application of controlled ventilation may deteriorate oxygenation and systemic pressure. Restrictive lung disease • May require less than 6 cc/kg Vt to prevent elevated intrapulmonary pressure • Application of positive pressure may result in barotrauma in addition to impaired preload.
  79. 79. Airway Anatomy Suggesting Difficult Intubation Length of upper incisors and overriding maxillary teeth Interincisor (between front teeth) distance < 3 cm (two finger tips) Thyromental distance < 7 cm • tip of mandible to hyoid bone (three finger breaths) Neck extension < 35 degrees Sternomental distance < 12.5 cm • With the head fully extended and mouth closed Narrow palate (less than three finger breaths) Mallampati score class III or IV Stiff joint syndrome Prayer Sign • About one third of diabetics characterized by short stature, joint rigidity, and tight waxy skin • Positive prayer sign with an inability to oppose fingers No sign is foolproof to indicate intubation difficulty Erden V, et al. Brit J Anesth. 2003;91:159-160.
  80. 80. Mallampati Score Class I: Uvula/tonsillar pillars visible Class II: Tip of uvula/pillars hidden by tongue Class III: Only soft palate visible Class IV: Only hard palate visible Den Herder, et al. Laryngoscope. 2005;115(4):735-739.
  81. 81. Comorbidities Potential for aspiration requires rapid sequence intubation with cricoid pressure • Clear liquids < 4 hours • Particulate or solids < 8 hours • Acute injury with sympathetic stimulation and diabetics may have prolonged gastric emptying time. Potential for hypotension • Cardiac dysfunction, hypovolemia, and sepsis • May need to consider awake intubation with topical anesthesia (aerosolized lidocaine) as sedation may precipitate hemodynamic compromise and even arrest. Organ failure • Renal and hepatic failure will limit medication used. • Potential for preexisting pulmonary edema and airway bleeding from manipulation
  82. 82. Induction Agents Sodium Thiopental • 3 - 5 mg/kg IV • Profound hypotension in patients with hypovolemia, histamine release, arteritis • Dose should be decreased in both renal and hepatic failure. Etomidate • 0.1 - 0.3 mg/kg IV • Lower dose range for elderly and hypovolemic patients • Hemodynamic stability, myoclonus • Caution should be exercised as even one dose causes adrenal suppression due to similar steroid hormone structure. • Unlikely to have prolonged effect in organ failure
  83. 83. Induction Agents (cont'd) Propofol • 2 - 3 mg/kg IV • Hypotension, especially in patients with systolic heart dysfunction, bradycardia, and even heart block • Unlikely to have prolonged effect in organ failure Ketamine • 1 - 4 mg/kg IV, 5 - 10 mg/kg IM • Stimulates sympathetic nervous system • Requires atropine due to stimulated salivation and midazolam for potential of dysphoria • Avoid in patients with loss of autoregulation and closed head injury
  84. 84. Neuromuscular Blockers Succinylcholine • 1 - 2 mg/kg IV, 4 mg/kg IM • Avoid in patients with malignant hyperthermia, > 24 hours out from burn or trauma injury, upper motor neuron injury, and preexisting hyperkalemia Rocuronium • 0.6 - 1.2 mg/kg, highest dose required for rapid sequence • Hemodynamically stable, 10% renal elimination Vecuronium • 0.1 mg/kg • Hemodynamically stable, 10% renal elimination Cisatricurium • 0.2 mg/kg • Mild histamine release, Hoffman degradation, not prolonged in renal or hepatic failure
  85. 85. Rapid Sequence Intubation Preoxygenate for three to five minutes prior to induction • Wash out nitrogen to avoid premature desaturation during intubation. Crycoid pressure should be applied from prior to induction until confirmation of appropriate placement. Succinylcholine 1 - 2 mg/kg IV will achieve intubation conditions in 30 seconds; Rocuronium 1.2 mg/kg IV will achieve intubation conditions in 45 seconds. • Other muscle relaxants do not produce intubation conditions in less than 60 seconds. Avoid mask ventilation after induction. • Potentially can inflate stomach • Use only if necessary to ensure appropriate oxygenation during prolonged intubation.
  86. 86. Y BAG PEOPLE (Reference #6)
  87. 87. Cricoid Pressure Cricoid is circumferential cartilage Pressure obstructs esophagus to prevent escape of gastric contents Maintains airway patency Koziol C, et al. AORN. 2000;72(6):1018-1030.
  88. 88. Sniffing Position Align oral, pharyngeal, and laryngeal axes to bring epiglottis and vocal cords into view. Hirsch N, et al. Anesthesiology. 2000;93(5):1366.
  89. 89. Mask Ventilation Mask ventilation crucial, especially in patients who are difficult to intubate Sniffing position with tight mask fit optimal May require two hands Mask ventilation crucial, especially in patients who are difficult to intubate Sniffing position with tight mask fit optimal May require two hands
  90. 90. Laryngoscope Blades and Endotracheal Tubes Mac blade: End of blade should be placed in front of epiglottis in valecula ETT for Fastrach LMA Pediatric uncuffed ETT ETT for blind nasal Standard ETT Miller blade: End of blade should be under epiglottis
  91. 91. Graded Views on Intubation Grade 1: Full glottis visible Grade 2: Only posterior commissure Grade 3: Only epiglottis Grade 4: No glottis structures are visible Yarnamoto K, et al. Anesthesiology. 1997;86(2):316.
  92. 92. Confirmation of Placement Direct visualization Humidity fogging the endotracheal tube End tidal CO2 which is maintained after > 5 breaths • Low cardiac output results in decreased delivery of CO2 Refill in 5 seconds of self-inflating bulb at the end of the endotracheal tube Symmetrical chest wall movement Bilateral breath sounds Maintenance of oxygenation by pulse oximetry Absence of epigastric auscultation during ventilation
  93. 93. Additional Considerations Always have additional personnel and an experienced provider as backup available for potential failed intubation Always have suction available Never give a muscle relaxant if difficult mask ventilation is demonstrated or expected Awake intubation should be considered in the following: • If patient is so hemodynamically unstable that induction drugs cannot be tolerated (topicalize airway) • If patient has a history or an exam which suggests difficult mask ventilation and/or direct laryngoscopy
  94. 94. American Society of Anesthesiologists
  95. 95. Alternative Methods Blind nasal intubation • Bleeding may cause problems with subsequent attempts. • Contraindicated in patients with facial trauma due to cribiform plate disruption or CSF leak • Avoid in immune suppressed (i.e., bone marrow transplant) Eschmann stylet Fiber optic bronchoscopic intubation • Awake vs. asleep Laryngeal mask airway • Allows ventilation while bridging to more definitive airway Light wand Retrograde intubation • Through cricothyrotomy Surgical tracheostomy Combitube
  96. 96. Eschman Stylet Use especially if Grade III view achieved Direct laryngoscopy is performed Place Eschman where trachea is anticipated May feel tracheal rings against stiffness of stylet Thread 7.0 or 7.5 ETT over stylet with the laryngoscope still in place
  97. 97. Fiberoptic Scope Essentially what is used to do a bronchoscopy Can be used to thread an endotracheal tube into the trachea either while the patient is asleep or on an awake patient with a topicalized airway Via laryngeal mask airway in place due to inability to intubate with DL: • Aintree (airway exchange catheter) can be threaded over the FOB to be placed into trachea upon visualization • Wire-guided airway exchange catheter can also be used with one more step
  98. 98. The Laryngeal Mask Airway (LMA)
  99. 99. LMA Placement Guide the LMA along the palate Eventual position should be underneath the epiglottis, in front of the tracheal opening, with the tip in the esophagus FOB placement through LMA positions in front of trachea Martin S, et al. J Trauma Injury, Infection Crit Care. 1999;47(2):352-357.
  100. 100. The FastrachTM Laryngeal Mask Airway Reinforced LMA allows for passage of ETT without visualization of trachea. 10% failure rate in experienced hands 20% failure rate in inexperienced
  101. 101. The Light Wand Transillumination of trachea with light at distal end Trachea not visualized directly Should not be used with tumors, trauma, or foreign bodies of upper airway Minimal complication except for mucosal bleed 10% failure rate on first attempt in experienced hands
  102. 102. Retrograde Intubation Puncture of the cricothyroid membrane with retrograde passage of a wire to the trachea Endotracheal tube guided endoscopically over the wire through the trachea Catheter through the cricothyroid can be used for jet ventilation if necessary. Wesler N, et al. Acta Anaes Scan. 2004;48(4):412-416.
  103. 103. Combitube Emergency airway used mostly by paramedics and emergency physicians for failed endotracheal intubation Ventilation confirmed through blind blue tube • Combitube is in the esophagus and salem sump can be placed through white tube Ventilation confirmed through white (clear) tube with patent distal end • Combitube is in the trachea and salem sump should be placed outside of combitube into esophagus • Fiber optic exchange can be accomplished through combitube
  104. 104. Combitube (cont'd) Should be changed to endotracheal tube (ETT) or tracheostomy to prevent progressive airway edema If in esophagus, take down pharyngeal cuff and attempt direct laryngoscopy (DL) or fiber optic bronchoscope (FOB) placement around combitube Failed exchange attempt can be solved with operative tracheostomy Placement of combitube can produce significant airway trauma • Removal prior to DL or FOB should be done with caution after thorough airway evaluation • Cricoid pressure should be maintained and emergency tracheostomy equipment available
  105. 105. Tracheostomy Surgical airway through the cervical trachea Emergent procedure carries risk of bleeding due to proximity of innominate artery Can be difficult and time consuming in emergent situations Sharpe M, et al. Laryngoscope. 2003;113(3):530-536.
  106. 106. Case Scenario #1 The patient is 70 kg with a 20-year history of diabetes. On exam, the patient has intercisor distance of 4 cm, thyromental distance is 8 cm, neck extension is 45 degrees, and mallampati score is 1. Your staff wants to use thiopental and pancuronium. Do you have any further questions for this patient or would you proceed with your staff?
  107. 107. Case Scenario #1 - Answer A diabetic for 20 years needs assessment for stiff joint syndrome. You should have the patient demonstrate the prayer sign. If the patient is unable to oppose their fingers, you should not give pancuronium. You may want to proceed with an LMA and FOB at your disposal. If the patient has a history of gastroparesis, you may want to consider an awake FOB.
  108. 108. Case Scenario #2 43-year-old patient with HIV, likely PCP pneumonia who had been prophylaxed with dapsone RR is 38, oxygen saturation is 90% on 100% NRB mask The patient is on his way to get a CT scan. Is it appropriate to proceed without intubation?
  109. 109. Case Scenario #2 - Answer Dapsone will produce some degree of methemoglobinemia. Therefore, some degree of desaturation may not be overcome. The patient is in significant respiratory distress and will be confined in an area without easy access. Intubation should be considered as an extra measure of safety, especially as this patient is likely to get worse.
  110. 110. Case Scenario #3 40-year-old, 182-kg man has a history of sleep apnea and systolic ejection fraction of 25%. He has a Strep pneumonia in his left lower lobe and progressive respiratory insufficiency. He extends his neck to 50 degrees and has a mallampati score of 2. Would you proceed with an awake FOB?
  111. 111. Case Scenario #3 - Answer The patient’s airway anatomy is not suggestive of difficulty. However, with supine position, subcutaneous tissue may impair your ability to visualize or ventilate. Use of gravity, including a shoulder roll, extreme sniffing position, and reverse trendelenburg may be helpful with asleep DL. Prudent to have some accessory equipment, including an LMA and FOB, for back up
  112. 112. References 1. Caplan RA, et al. Practice guidelines for management of the difficult airway. Anesthesiology. 1993;78:597-602. 2. Langeron O, et al. Predictors of difficult mask ventilation. Anesthesiology. 2000;92:1229-36. 3. Frerk CM, et al. Predicting difficult intubation. Anaesthesia. 1991;46:1005-08. 4. Tse JC, et al. Predicting difficult endotracheal intubation in surgical patients scheduled for general anesthesia. Anesthesia & Analgesia. 1995;81:254-8. 5. Benumof JL, et al. LMA and the ASA difficult airway algorithm. Anesthesiology. 1996;84:686-99. 6. Reynolds S, Heffner J. Airway management of the critically ill patient. Chest. 2005;127:1397-1412.