Spinal Surgery Anesthesia Flashcards
What is scoliosis?
Lateral rotation of the spine > 10° with vertebral rotation.
What are the effects of thoracic spine scoliosis?
- ↓ Chest wall compliance
- Restrictive lung disease
- ↓ exercise tolerance
Get PFTs!
What EKG/cardiac findings might one suspect to find on a scoliosis patient? (Select all that apply)
a. RVH
b. RAE
c. LVH
d. Bi-atrial enlargement
a & b
The increased pulmonary vascular resistance of chronic, significant scoliosis can lead to ___ _______.
cor pulmonale
Enlarged RV due to lung disease.
What muscles would you expect to be effected from a C5 injury?
- Partial diaphragmatic paralaysis
Flaccid Muscles (sensory & motor)
- Deltoids
- Biceps
- Brachialis
- Brachio-radialis
What are the hemodynamic consequences of injuries T5 and higher?
Physiologic Sympathectomy
- ↓BP
- ↓HR
TX: Midodrine
- if higher then T1-T4 treat with EPI (atropine wont work)
Autonomic Hyperreflexia is most often seen with cord transection above the ____ level.
T5/T6
What s/s are seen with autonomic hyperreflexia?
- Severe, transient HTN
- Bradycardia
- Dysrhythmias
- Cutaneous dilation and constriction
In autonomic hyperreflexia, cutaneous vasodilation is seen _____ the site of injury, whilst cutaneous vasoconstriction is seen ____ the site of injury.
above ; below
What is the basic pathophysiology of Autonomic Dysreflexia?
What are the most common causes of Autonomic Dysreflexia?
- Distended bladder/bowel
- Noxious stimuli (think surgical pain)
What is the treatment for Autonomic Dysreflexia?
- Removal of stimulus
- Deepen anesthetic
- Direct-acting Vasodilators
Injury to C3-C5 results in….
Diaphragmatic respiratory failure
Is respiratory function affected by injury to C5-C7?
Yes; impairment of abdominal and intercostal respiratory support
Why is there an increased risk of pulmonary infection with cervical spine injuries?
- Inability to cough/ clear secretions
- Atelectasis
What is poikilothermia?
Inability to maintain constant core temp
What is the pathophysiology of poikilothermia?
- SNS disruption
- Temperature sensation disruption
- Inability to vasoconstrict below spinal cord injury
Spinal deformities are associated with _______ respiratory patterns, often necessitating PFT’s and an ABG.
Restrictive
Flaccidity in which two muscles would indicated possible cervical spine fracture?
- Deltoids
- Biceps
What is the greatest risk with a total sitting position?
VAE (Venous Air Embolism)
An anterior approach for a thoracic spine procedure requires what position and equipment?
- Lateral position with bag
- Double Lumen ETT or bronchial blocker
May have to drop lung for access.
A posterior approach for a thoracic spine procedure requires what position and equipment?
- Prone with arms tucked or 90° abduction
- Single lumen ETT.
What are the three causes of postoperative vision loss secondary to prone positioning?
- Ischemic Optic Neuropathy (ION)
- Retinal vessel occlusion
- Cortical brain ischemia
T/F. Ischemic optic neuropathy occurrence requires direct pressure placed on the eyes?
False. Can occur without direct pressure.
*Occurs due to ↓ blood flow or O₂ delivery.
What are risk factors for ION?
- Male
- Obesity
- Wilson Frame Use
- > 6 hour surgery
- ↓ colloid usage
- Blood loss > 1000 mL
What is the typical onset of ION?
24 - 48 hours
What are the symptoms of ION?
Bilateral
- Painless vision loss
- Non-reactive pupils
- No light perception
What are the treatments for ION?
- Acetazolamide (Diamox)
- Corticosteroids
- Increase BP or Hgb
- Hyperbaric O₂
What type of frame pictured below?
Wilson Frame
What are the respiratory effects of prone positioning?
↓ FRC
↓ compliance
Due to ↑ intrabdominal pressures → ↑ intrathoracic pressures.
Does venous return increase or decrease in prone positioning?
decrease
Which of the following positioning devices is the most stable?
Mayfield Tongs
What cardiac consequences are there to prone positioning?
Why?
- ↓ preload
- ↓ CO
- ↓ BP
Due to pooling of blood in extremities and compression of abdominal contents and muscles.
What neurological consequences occur due to prone positioning?
Extreme head rotation
↓ cerebral venous drainage and ↓ CBF
What risk factors are there for increased blood loss during spinal surgery?
- Number of vertebrae
- > 50 yo
- Obesity
- Tumor surgery (angiogenesis)
- ↑ intrabdominal pressure
- Transpedicular osteotomy
When is autologous blood donation contraindicated in spinal surgery?
- Significant cardiac disease
- Infection
What is the push dose of TXA?
- 10 mg/kg IV
What is the infusion dose of TXA?
2 mg/kg/hr
What is the push dose of aminocaproic acid?
Infusion dose?
Push dose: 100 mg/kg IV
Infusion: 10 - 15 mg/kg/hr
Somatosensory Evoked Potentials (SSEPs) are associated with what spinal column and sensations?
Dorsal column pathways
- Proprioception
- Vibration
Motor Evoked Potentials (MEPs) are associated with what spinal column and sensations?
Anterior/ Motor Column
During spinal surgery, electromyogram (EMG) is used to monitor for what during pedicle screw placement and nerve decompression?
Monitor for nerve root injury.
What is an SSEP?
Impulse from a peripheral nerve that is measured centrally.
What are Motor Evoked Potentials (MEPs)?
Impulse triggered in the brain (centrally) and monitored in specific muscle groups.
What are possible adverse effects associated with MEPs?
- Cognitive defects
- Seizures
- Intraoperative awareness
- Scalp burns
- Cardiac arrythmias
- Bite injuries (bite block necessary)
In what patients should MEPs be avoided?
- Patients w/ active seizures
- Patients w/ vascular clips in brain
- Patients w/ cochlear implants
Differentiate amplitude and latency in regards to neurophysiologic monitoring.
Amplitude: signal strength
Latency: time for signal to travel through spinal cord.
What physiologic factors commonly can affect amplitude and latency of neurophysiologic monitoring?
- Hypothermia
- Hypotension
- Hypocarbia
- Hypoxia
- Anemia
- VAAs
How do VAAs affect neurophysiologic agents?
Dose dependent
- ↓ amplitude
- ↑ latency
Out of the following drugs, which affects our MEPs the most?
- Opioids
- Midazolam
- Ketamine
- Propofol
Propofol depresses MEPs.
The others have little effect on MEPs.
How much does muscle relaxant requirement increase when using MEPs?
Trick question. No muscle relaxants after intubation.
What type of nerve block might be used for spinal surgery?
Erector Spinae block
During what surgery is venous air embolism at its greatest risk of happening?
Laminectomies
- Large amount of exposed bone
- Surgical site above the heart
What are some s/s of VAE?
- Unexplained ↓BP
- ↑ EtN₂
- ↓ EtCO₂
