Test 1: Anesthesia for Orthopedic Surgery Spine Anesthesia Management Flashcards
For pre-op evaluations, airway management issues occur more often in what type of spine cases?
- Cervical
- Thoracic
Spinal deformities may cause _________ respiratory patterns
- Restrictive
May need PFT and ABG
Pre-op cardiac evaluations for spine surgery
- Cardiovascular compromise resulting from pathology requiring spine surgery (ie: severe kyphoscoliosis)
Pre-op musculoskeletal evaluation for spine surgery
- ROM
- Surgical positioning
Pre-op neuro evaluation for spine surgery
- Document pre-existing sensory and motor deficits (flaccid deltoid and biceps → cervical spine fx)
- 6 P’s of Neurovascular assessment (Pain, Pallor, Pulselessness, Paresthesia, Paralysis, Poikilothermia)
- Castillo’s 6 P’s (Proper Planning Prevents Piss Poor Performance)
Anesthesia option for spine procedures
- General Endotracheal Anesthesia (GETA) - most common
- Consider neurophysiological monitoring (SSEP/ MEP, EMG)
- Voltailes vs. TIVA
- Succinylcholine vs NDMR
When can regional/ neuraxial anesthesia be used for spine surgery?
- Lumbar laminectomy (1-2 levels)
- Disc surgery
- Surgeon can supplement block under direct visualization of spinal cord
What are the goals of positioning in spine surgery?
- Avoid injury to the eyes
- Avoid injury to peripheral nerves
- Avoid injury to bony prominences
- Maintain low venous pressure to the surgical site
Cervical Spine anterior positioning
- Patient lies supine
- Arms tucked in neutral position
- Head on padded headrest
Cervical Spine posterior approach positioning
- Patient lies prone
- Arms tucked in the neutral position
- Head in Mayfield device (pins) stimulating (Give 5-10 mL bolus of propofol)
What surgical position will have the most significant risk for venous air embolism?
- Sitting position
- This position is uncommon for cervical procedures
Thoracic Spine anterior approach positioning
- Requires DLT or bronchial blocker
- Lateral position w/ bean bag
Thoracic Spine posterior approach positioning
- Prone position
- Single lumen ETT
- Gel headrest/ proneview
- Arms tucked neutral or less than 90 degrees abduction
Airway considerations for prone patients
- Consider antisialogoue in preop (glycopyrrolate 0.2 mg)
- Add corrugated adapter
- Risk of ETT kinking
- Assess for bilateral breath sounds after turning
- Unintentional extubations
- Airway edema (be mindful of IV fluids)
What is the incidence of postoperative visual loss (POVL)? Causes?
- Less than/ equal to 0.1%
- Ischemic optic neuropathy (ION)
- Retinal artery/ vein occlusion
- Cortical brain ischemia (hypotension)
Kneel directly on the floor and get visualization that eyes are not being compressed when the patient is prone
Describe ischemic optic neuropathy.
- Ischemia d/t decrease blood flow or O2 delivery
- Can occur in both anterior or posterior spinal approaches
- Occurs without pressure to the eyes
- Onset can occur 24-48 hours post op
Risk factors of Ischemic Optic Neuropathy
- Male gender
- Obesity
- Use of Wilson frame
- Surgery > 6 hours
- Decrease colloid use
- Blood loss > 1000 mL
Symptoms of Ischemic Optic Neuropathy
- Unilateral or Bilateral painless visual loss
- Nonreactive pupils
- No light perception
Treatment for Ischemic Optic Neuropathy
- Azetazolamide
- Diuretics
- Corticosteroids
- Increase BP or HgB
- Hyperbaric Oxygen
- Neuro consult
What are ways to minimize or avoid ischemic optic neuropathy?
- Head neutral/ midline
- Blood transfusion or colloids
- Minimize intentional hypotension
- Maintain MAP autoregulation level
Central Retinal Artery Occlusion
- Decrease blood supply to the ENTIRE retina
Retinal Arterial Branch Occlusion
- Decrease blood supply to PART of the retina
What is the name of this device indicated by the yellow arrow?
- Wilson frame
- Used to maintain the neutrality of the thoracic and lumbar spine
- Be mindful of breast and male genitals when using the Wilson frame
What is the name of this table?
- Jackson Spine Table
- Very compatible with C-arm use
Describe the use of the prone pillows.
- Face protection
- Prevent pressure on the nose and mouth
- Make sure there is no pressure to the ears
- There is a hole on the side for the ETT to exit
Head and Neck Positioning for prone patients
- Alignment of axis
- Avoid excessive flexion and extension
- Avoid lateral rotation of head
Excessive neck flexion can shorten the neck of the patient, ETT can hit the carina.
Excessive neck extension can elongate the neck of the patient, ETT can be extubated.
Arm Position for prone patients
- Superman/ surrender
- Less than 90 degrees of abduction
- Consider tension on shoulder musculature (padded and support)
Illiac crest and genitalia position for prone patients
- Avoid compression
- Someone must check
Hips and Knees for prone patients
- Slightly flexed
- Pillow/pads
- No pressure on fibular heads
What happens to the abdominal pressure in the prone position?
- ↑ Intraabdominal pressure
What will result from increased intrathoracic pressure when the patient is prone?
- ↓ FRC and ↓ Pulmonary Compliance
- ↓ Venous Return
- ↑ Bleeding from Epidural Veins
Position Device Chart to memorize
- Mayfield Tongs
Cardiac effect in prone positioning
- Pooling of blood in extremities
- Compression of abdominal muscles may decrease preload, CO, and BP
Respiratory effect in prone positioning
- Compression of the abdomen and thorax will decrease total lung compliance and increase work of breathing
Neuro effect in prone positioning
- Extreme head rotation may decrease cerebral venous drainage and cerebral blood flow
What factors will increase blood loss for spine surgery?
- Number of levels included in surgery
- Age > 50 years
- Obesity
- Surgery for tumors
- ↑ Intraabdominal pressure
- Transpedicular osteotomy
Transfusion consideration for spine surgery
- Should always be considered for spine surgery
- Establish 2 large bore IVs, 2 units of blood ready to go
- Consider comorbidities
- Higher allowable blood loss (30% of total blood volume)
- Hemodynamic profile
- Hgb 7-8 g/dL
- Cell saver ($$$)
What antifibrinolytics is used for spine surgery?
- Transexamic acid (TXA)
- Aminocarproic acid (Amicar)
Dose for TXA
- 10 mg/kg IV
- Infusion: 2 mg/kg/hr (d/c end of procedure)
Dose for Amicar
- 100 mg/kg IV
- Infusion: 10-15 mg/kg/hr (d/c end of procedure)
What is the standard threshold amount for crystalloid?
- No more than 3 Liters
- Varies by patient and facility
Intraoperative hemodilution process
- Removal of 450-500 mL of blood after anesthesia induction
- Maintain normovolemia with crystalloid or colloids
- Reinfusion after surgery
This minimizes the need for allogeneic blood transfusions.
This is also a very RARE practice.
What is the risk of intentional/ deliberate hypotension?
- Risk of end-organ ischemia
- Not recommended in spine surgery, but is often requested by surgeons
What is the purpose of Neurophysiologic Monitoring?
- Evaluate gross movements of upper and lower extremities
What are the complications of Neurophysiologic Monitoring?
- Inadvertent extubation
- Air Embolism
- Violent movements → movement of instruments
What is Somatosensory Evokes Potential (SSEP)
- Assessment of the dorsal column pathways of proprioception and vibration
- SSEPs are generated by stimulating peripheral nerves (usually sensory nerves) and recording the electrical responses along the sensory pathways
- Impulse from peripheral nerve measured centrally
SSEP: Assess integrity of the sensory pathways in the nervous system.
What is Motor Evoke Potential (MEP)
- Assessment of the anterior/ motor portion of the spinal cord
- MEPs are generated by stimulating the motor cortex of the brain, usually using transcranial electrical stimulation, and recording the electrical responses along the motor pathways, including the spinal cord and peripheral muscles.
- Impulse triggered in brain → monitored in specific muscle groups
MEP: Assess integrity of the motor pathways in the nervous system.
What is Electromyography?
- EMG stands for Electromyography, which is a diagnostic procedure used to assess the health of muscles and the nerve cells (motor neurons) that control them.
- Monitor nerve root injury during pedicle screw placement and nerve decompression
What are the adverse effects of MEP?
- Cognitive defects
- Seizures (contraindicated)
- Intraop awareness
- Scalp burns
- Cardiac arrhythmias
- Bite Injuries (use bite blocks)
When would you avoid using MEP?
- Patients with active seizures
- Vascular clips in the brain
- Cochlear implants
In neurophysiologic monitoring, what is amplitude?
- Signal strength
In neurophysiologic monitoring, what is latency?
- Time it takes for the signal to travel through the spinal cord
What are the factors that can affect amplitude and latency?
- Hypotension
- Hypothermia
- Hypocarbia
- Hypoxia
- Anemia
- Anesthetics
How do Volatile Agents affect the amplitude and latency of neurophysiological monitoring?
- Decrease in amplitude
- Increase in latency
How much VA should be used during Neurophysiologic Monitoring
- Volatile agents at 0.5 MAC
Effects of N2O on Neurophysiologic Monitoring
- Using N2O decreases amplitude
- Eliminate N2O during MEP monitoring
MEPS are least affected by what drugs?
- Opioids
- Midazolam
- Ketamine
Propofol’s effect on MEP
- Depresses MEP
What are post-op complications with spine surgery?
- Surgery time > 4 hours → Facial/Laryngeal Edema
- Thoracic cavity invasion
- EBL > 30 mL/kg or > 2000 mL
What type of peripheral nerve block can be used post-op for spine surgery?
- Erector spinae block
What spine surgery poses the highest risk of VAE?
- Laminectomy d/t large amount of exposed bone
- Surgical site above the heart
Symptoms of VAE?
- Unexplained hypotension
- Increase in ET Nitrogen
- Decrease ETCO2
