Anesthesia for Neuroskeletal and Spinal Cord Surgery – Flashcards
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1. Sensory and motor function: paresthesias, weakness, numbness 2. Factors that exacerbate symptoms: neck ROM, UE & LE numbness or tingling, presence of weakness 3. Amount of pain, cause, & treatment modes for pain
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Things to assess pre-operatively for neuroskeletal and spinal cord surgery
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1. Mobility of neck (flexion, extension) 2. RA? May have atlantoaxial subluxation 3. Mouth opening, especially with c-collar
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Pre-op assessment for cervical cases
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Lateral flexion and extension X-rays
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If they have atlantoaxial subluxation, what tests should be ordered?
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> 5 mm
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What amount of instability (in mm) requires inline neck stabilization and/or awake fiberoptic intubation?
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1. Use in-line stabilization and jaw thrust technique for established airway 2. Sniffing position is CONTRAINDICATED
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For a trauma patient, how should the airway be manipulated?
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1. Clinically 2. Radiographically
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Two ways that a trauma patient need to be cleared
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When spinal cord transection is above T5-T6
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When do you see autonomic dysreflexia?
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Can occur anytime post-injury, most often after spinal shock phase has passed
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When does autonomic dysreflexia usually occur?
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HA
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What is a classic sign of autonomic dysreflexia?
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Normal inhibitory impulses are interrupted.
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Explain the pathophysiology behind autonomic dysreflexia?
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1. Paroxysmal HTN (episodic high BP) 2. Throbbing HAs 3. Profuse sweating 4. Nasal stuffiness 5. Flushing of skin above the level of the lesion 6. Bradycardia (secondary to baroreceptor reflex) 7. Apprehension 8. Anxiety 9. Vasodilation above the level of transection
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SIgns and symptoms of autonomic dysreflexia
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General anesthetic or regional **epidural not as effective**
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What type of anesthetic should you use to try to avoid autonomic dysreflexia?
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Direct arterial dilators and alpha blockers, i.e., hydralazine, cardene, nipride,
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Types of drugs to use to get BP down in autonomic dysreflexia
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1. Remove the stimulus 2. Deepen the anesthetic 3. Give direct acting vasodilators
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If autonomic dysreflexia occurs, what should you do?
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1. Seizure 2. Intracranial hemorrhage 3. MI
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What can autonomic dysreflexia lead to if it goes untreated?
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1. Prevent occlusion of venous outflow!
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What to avoid when in the prone position
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1. Use Jackson table or wilson frame to minimize pressure on thoracic and abdominal areas (may impede ventilation, engorge epidural veins, leading to increase bleeding) 2. Maintain neck in neutral position
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Ways to prevent occlusion of venous outflow
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1. Eyes, face, and ears pressure free 2. Arms abducted less than 90 degrees to prevent thoracic outlet syndrome = compression of brachial plexus 3. Post-operative vision loss
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Other considerations to be aware of when the patient is in the prone position
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T1-T4
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INjury to what level on the spinal cord may result in bradycardia?
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Decrease in vital capacity up to 60%
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What happens to respiratory function when lesions occur between C5-T7?
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Ischemic optic neuropathy
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What is the most common form of POVL?
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No! Can occur in cases not in prone position
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Does ischemic optic neuropathy occur due to trauma or pressure on the eyes?
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Unilateral or bilateral, no ligh perception to color vision deficits
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What vision deficits are seen with ischemic optic neuropathy?
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ASA I and ASA II at any age
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What ASA class had most cases of POVL?
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Central retinal artery occlusion
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What form of POVL does occur due to trauma or pressure on the eyes?
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1. Hemoglobin < 8 2. Hematocrit 6 hours in duration 6. EBL mean = 2.3 L 7. Labetolol used to treat BP 8. Decrease venous outflow 9. Chronic disease, obesity, HTN, DM, glaucoma, smoking
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Risk factors for Ischemic Optic Neuropathy
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1. Use of a-line to assess BP, keep within 20% of pre-op baseline, shift higher in HTNive patients 2. Reconsider controlled hypotension 3. Use colloids in conjunction with crystalloids 4. Position head at or above level of the heart to allow venous drainage 5. Transfuse earlier or not let hemoglobin go as low 6. Consider staging the surgical procedure to cut down on duration < 6 hours **If occurs, aggressive BP elevation, restore blood volume**
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What interventions can you do to decrease the risk of ischemic optic neuropathy?
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Electric potentials that are measured in response to a type of stimulus
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What are evoked potentials?
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To preserve or improve neurological function and prevent injury
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Why are evoked potentials performed?
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1. Hypothermia 2. Hypotension 3. Positioning (can kink nerve with position changes) 4. Anesthetic agents
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What are evoked potentials affected by?
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Persistent obliteration of Eps
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What is predictive of post-operative neurological deficit?
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Voltage versus Time
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What are EP waveforms plotting?
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Latency - time between stimulation and detection Amplitude - SIze or intensity of neurologic response
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What do EPs measure?
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A brief electrical current is delivered to sensory or mixed nerve; if pathway is intact, an action potential will exist
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How are somatosensory potentials measured?
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Detection of spinal cord ischemia
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What are SSEPs used for?
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No. They only detect posterior spinal cord ischemia.
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Do SSEPs detect ischemia both anteriorly and posteriorly?
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To monitor the auditory pathway to investigate patients with... 1. Possible multiple sclerosis 2. Structural lesions of the brainstem and posterior fossa 3. Intraoperatively to monitor integrity of the auditory pathways during neurosurgical excision of posterior fossa tumors
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What are brain auditory evoked potentials used for?
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To monitor the integrity of the motor tracts only
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What are motor evoked potentials used for?
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Involves stimulating a motor nerve and measuring the involved muscle response. Similar to train of four
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What are active electromyography? (EMGs)
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Paralytics
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What pharmacologic agents should be avoided when monitoring EMGs?
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1. Stretching, torsion or retraction of spinal cord 2. HOTN, decreased blood flow to spinal cord 3. Hypoxia, hypercarbia 4. Anemia (POVL) 5. Dislodgement of probes 6. Hypothermia 7. Electrical interference (cautery, OR equipment)
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What kinds of things can affect SSEPs?
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Increase latency, decrease amplitude **exception: ketamine, etomidate, narcotics; these agents don't cause as much of a change**
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What do most anesthetic drugs do to latency and amplitude?
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< 1 MAC May need TIVA and avoid N2O as it potentiates anesthetic gases
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What MAC do you want your gas at if monitoring SSEPs?
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Yes, just not with motor Eps
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Can you use paralytics with SSEP monitoring?
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1. Notify surgeon 2. Increase O2 concentration 3. CHeck positioning of patient in affected area 4. Ensure adequate blood pressure 5. Assess for anemia 6. Have monitoring tech check lead/probe placement
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What to do if SSEPs are affected
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- cervical disc herniation can be removed through anterior approach through front of neck to relieve spinal cord or nerve root pressure and alleviate corresponding pain, weakness, numbness, and tingling - fusion surgery almost always done at the same time as the discectomy in order to stabilize the cervical segment - together, the combined surgery is commonly referred to as an ACDF surgery
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Describe anterior cervical disc fusion (ACDF).
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Sniffing position, depending on what type of injury (traumatic vs. chronic vs. symptomatic)
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When establishing the airway for ACDF, what should you avoid?
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1. Arms tucked, 2 IVs 2. Ask if there will be EP monitoring 3. Usually minimal blood loss 4. Minimize fluids to decrease risk of swelling of neck structures 5. Avoid glucose containing solutions (for periods of neuronal ischemia)
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Anesthetic considerations for ACDF
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Neurogenic shock
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If acute injury in ACDF, what should you assess for?
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Carotid or large veins of neck
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What is a risk during ACDF surgery (think vessels and bleeding)?
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1. Inspect with fiberoptic scope 2. Cuff leak test 3. Extubate over Cook catheter 4. Leave intubated for 24 hours if edema suspected
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What can you do before extubation to assess for tracheal edema or fluid accumulation?
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Tension pneumothorax from access to thoracic cavity, may get chest tube
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What complication can arise during posterior spinal fusion?
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With a single level, minimal blood loss With multiple levels, increases blood loss
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How much blood loss is expected during posterior spinal fusion?
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General with ETT 2 large bore IVs Aline Possibly cell-saver if multiple levels are involved
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What type of anesthetic and vascular access is appropriate for posterior spinal fusion?
