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A20 Anesthesia
Maintenance Toronto Notes 2019 Maintenance
• generalanesthesiaismaintainedusingvolatileinhalationagentsand/orIVagents(i.e.propofolinfusion) • analgesia(usuallyIVopioids)andmusclerelaxantsarealsogivenasneeded
Extubation
• criteria:patientmustnolongerhaveintubationrequirements ■ patency: airway must be patent
■ protection: airway reflexes intact
■ patient must be oxygenating and ventilating spontaneously
• generalguidelines
■ ensure patient has normal neuromuscular function (peripheral nerve stimulator monitoring) and
hemodynamic status
■ ensure patient is breathing spontaneously with adequate rate and tidal volume
■ allow ventilation (spontaneous or controlled) with 100% O2 for 3-5 min
■ suction secretions from pharynx, deflate cuff, remove ETT on inspiration (vocal cords abducted)
■ ensure patient is breathing adequately after extubation
■ ensure face mask for O2 delivery available
■ proper positioning of patient during transfer to recovery room (supine, head elevated)
Complications of Extubation
• earlyextubation:aspiration,laryngospasm
• lateextubation:transientvocalcordincompetence,edema(glottic,subglottic),pharyngitis,tracheitis
Laryngospasm
• definedasforcefulinvoluntaryspasmoflaryngealmusclescausedbystimulationofsuperiorlaryngeal nerve (by oropharyngeal secretions, blood, extubation)
• causespartialortotalairwayobstruction
• morelikelytooccurinsemi-consciouspatients
• prevention:extubatewhilepatientisstilldeeplyunderanesthesiaorfullyawake
• treatment:applysustainedpositivepressurewithbag-maskventilationwith100%oxygen,low-dose
propofol (0.5-1.0 mg/kg) optional, low-dose succinylcholine (approximately 0.25 mg/kg) and reintubate if hypoxia develops
Regional Anesthesia
• localanestheticagent(LA)appliedaroundaperipheralnerveatanypointalongthelengthofthenerve (from spinal cord up to, but not including, the nerve endings) for the purpose of reducing or preventing impulse transmission
• no CNS depression (unless overdose of local anesthetic); patient remains conscious • regionalanesthetictechniquescategorizedasfollows:
■ epidural and spinal anesthesia (neuraxial anesthesia) ■ peripheral nerve blocks
■ IV regional anesthesia (e.g. Bier block)
Patient Preparation
• sedationand/oranxiolysismaybeindicatedbeforeblock
• monitoringshouldbeasextensiveasforgeneralanesthesia
Epidural and Spinal Anesthesia
• mostcommonforsurgeriesperformedbelowlevelofumbilicusbutcanbeextendedtoanylevel(useful in thoracic, abdominal and lower extremity surgeries. Typically placed in thoracic or lumbar spine)
Anatomy of Spinal/Epidural Area
• spinalcordextendstoL2,duralsactoS2inadults
• nerveroots(caudaequina)fromL2toS2
• needleinsertedbelowL2shouldnotencountercord,thusL3-L4,L4-L5interspacecommonlyused • structurespenetrated(outsidetoinside)
■ skin
■ subcutaneous fat
■ supraspinous ligament
■ interspinous ligament
■ ligamentum flavum (last layer before epidural space) ■ dura + arachnoid for spinal anesthesia
Benefits of Regional Anesthesia
• Reduced perioperative pulmonary complications
• Reduced perioperative analgesia requirements
• Decreased PONV
• Reduced perioperative blood loss
• Ability to monitor CNS status during
procedure
• Improved perfusion
• Lower incidence of VTE
• Shorter recovery and improved
rehabilitation
• Pain blockade with preserved motor
function
Landmarking Epidural/Spinal Anesthesia
• Spinous processes should be maximally flexed
• L4 spinous processes found between iliac crests
• T7 landmark at the tip of the scapula
Classic Presentation of Dural Puncture Headache
• Onset 6 h-3 d after dural puncture
• Postural component (worse when sitting) • Occipital or frontal localization
• ± tinnitus, diplopia