Spinal Surgery Anesthesia Unit 1 Module 3 Flashcards
What is scoliosis?
Lateral rotation of the spine > 10° with vertebral rotation.
symptoms of adult scoliosis
back pain: arthritis, disc degeneration, spinal stenosis (worse standing)
radiculopathy: pinching of the nerve root at the spinal column
sciatica
What are the effects of thoracic spine scoliosis?
- ↓ Chest wall compliance
- Restrictive lung disease
- ↓ exercise tolerance
Get PFTs!
With thoracic scoliosis, what preop exam can you do to assess for pulmonary HTN
Echo
Normal Values:
○Vt:
○Minute ventilation:
○Functional residual capacity :
○Forced vital capacity
○Forced expiratory volume FEV1:
○Peak Expiratory flow rate :
○Vt: 500 ml
○Minute ventilation: Vt x (# of breaths) 5-10 L
○Functional residual capacity : 3L
○Forced vital capacity 4.5 L
○Forced expiratory volume FEV1: 0.8 or 80&
○Peak Expiratory flow rate : 400-700 L/min
Thoracic scoliosis can lead to chronic _____ secondary to V/Q mismatch
chronic hypoxemia
Increased ____ is common in Thoracic scoliosis, especially with the occurrence of Cor Pulmonale.
pulmonary vascular resistance (PVR)
____ _____ is a condition in which the right side of the heart becomes enlarged and weakened due to increased pressure in the pulmonary arteries.
Cor Pulmonale
What changes to you see on an EKG with an enlarged right ventricle and an enlarged right atrium
right axis deviation:
a large R wave in the right precordial leads (V1 and V2)
and a deep S wave in the left precordial leads: (V5 and V6)
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
Corrective surgery for thoracic scholiosis, you expect large blood loss r/t (7)
● Surgical technique
● Operative time
● Number of vertebral levels fused
● Mean arterial pressure (MAP)
○Will be using surgical
hypotension technique
● Platelet abnormalities
● Dilutional coagulopathy
● Primary fibrinolysis
Spinal cord injury:
What muscles would you expect to be affected by a C5 injury?
- Partial diaphragmatic paralaysis
- Deltoids
- Biceps
- Brachialis
- Brachio-radialis
Innervation from (___ - ___) keep the diaphragm alive
C3-C5
What are the hemodynamic consequences of injuries T5 and higher?
Physiologic Sympathectomy
- ↓BP
- ↓HR
- tx midodrine
____ - ____ are the cardiac accelerators
T1-T4
Injuries are higher than T1-T4 and the pt has bradycardia. What medications will you give?
jump straight to epinephrine
anticholinergics like atropine and glycopyrrolate will not work
Autonomic Hyperreflexia is most often seen with complete cord transection above the ____ level.
T5/T6
With automonic hyperreflexia:
below the injury, there is ____
&
above the injury, there is ___
below the injury there is vasoconstriction –> severe transient HTN –> bradycardia & dysrhtyhmias
&
above the injury, there is cutaneous vasodilation
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?
● Cranial nerve 9 (glossopharyngeal nerve) contributes to bradycardia in autonomic hyperreflexia by carrying sensory information from the carotid sinus baroreceptors to the brainstem, which then triggers a parasympathetic response via the vagus nerve (cranial nerve 10), leading to a decreased heart rate as a compensatory mechanism to the sudden rise in blood pressure associated with autonomic hyperreflexia.
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
- impairment of expiration
Why is there an increased risk of pulmonary infection with cervical spine injuries (C5-C7)?
- Inability to cough/ clear secretions
- Atelectasis
What is poikilothermia?
Inability to maintain constant core temp
What is the pathophysiology of poikilothermia?
- disruption of sympathetic pathways
- 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
There can be CV compromise in severe ____ requiring spine surgery
kyphoscoliosis
With spinal surgeries, you should assess/evaluate these 6 things
respiratory
cardiac
musculoskeletal (ROM/surgical positioning)
Neuro: sensor and motor deficits
Labs
cervical spine:
○C-collar: pre-op C-spine clearance
○Halo
○Cervical Spine Traction
○Assess and Document neuro deficits
○Atlanto-axial instability (C1&C2 stability)
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)
Do you commonly use NMBD in spinal surgery?
Not if you need to monitor SSEP/MEP/EMG
GETA most common
Spinal surgery:
Goals:
-avoid injury to (3)
Eyes
peripheral nerves
bony prominences
and maintain low venous pressure to surgical site
Cervical spine anterior approach position
supine
arms tucked/neutral position
head on a padded headrest
Cervical spine posterior approach positioning
prone
arms tucked neurtrally
head in mayfield device (pins)
*very stimulating make sure the pt is deep enough
what is a prone table called
Jackson table
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.
-gel headrest/prone view
if you patient will be in the prone position for a period of time, what drug class should you consider giving in preop
anti-sialogogue
Once you flip your patient to prone, what can you do to prevent accidental extubation and tube placement
add corrugated adaptor and asses for _ BL breath sounds
What are the three causes of postoperative vision loss secondary to prone positioning?
- Ischemic Optic Neuropathy (ION)**
- Retinal artery/vein 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
about how long does crystalloids stay in the vascular space?
20-40 mins
What is castillo’s rule of thumb as to when you should switch from a crystalloid to a colloid
3L
What is the typical onset of ION?
24 - 48 hours
What are the symptoms of ischemic optic neuropathy (ION)?
Bilateral
- Painless vision loss
- Non-reactive pupils
- No light perception
** make sure to assess pupils in preop so you know if there has been a change
What are the treatments for ION?
- Acetazolamide: diuretic
-diuretic (loop) - Corticosteroids
- increasing BP or Hgb
-Hyperbaric O₂
What is it called when blood supply to the entire retina is decreased or an occlusion of the retinal arterial branch
Central Retinal Artery Occlusion
What time of frame pictured below?
Wilson Frame
What is this prone table called
Jackson spine table
What are the respiratory effects of prone positioning?
↓ FRC
↓ compliance
increased WOB
Due to ↑ intrabdominal pressures → ↑ intrathoracic pressures.
With prone position what happens to epidural veins?
increased intrathoracic pressure –> increased bleeding from epidural veins
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 if there is extreme head rotation?
↓ cerebral venous drainage and ↓ CBF
memorize this chart
What risk factors are there for increased blood loss during spinal surgery? (6)
- Number of vertebrae
- > 50 yo
- Obesity
- Tumor surgery
- ↑ intrabdominal pressure
- Transpedicular osteotomy
What should you consider when deciding to transfuse spinal surgery patients? (4)
■ Consider comorbidities
■ Hemodynamic profile
■ Higher allowable blood loss
■ Hgb 7-8g/dL
A cell saver can be used in the OR. What is it?
cell saver is a medical device that collects, processes, and returns a patient’s own blood during surgery or other procedures.
When is autologous blood donation contraindicated in spinal surgery?
- Significant cardiac disease
- Infection
When is autologous blood donation considered in spinal surgery?
when anticipated EBL 500-1000 mL
What is the push dose of TXA?
What is the max of TXA?
- 10 mg/kg IV
-2.5 g
What is the infusion dose of TXA?
2 mg/kg/hr
*d/c infusion at the end of the procedure
What is the push dose of aminocaproic acid (antifibrinolytic)?
Infusion dose?
Push dose: 100 mg/kg IV
Infusion: 10 - 15 mg/kg/hr (d/c at the end of the procedure)
What is intraoperative hemodilution?
■Removal of 450-500mL blood after anesthesia induction
■Maintain normovolemia w/ crystalloid or colloid
■Then transfuse the blood back at the end of the procedures
Neurophysiologic monitoring used in corrective surgery
-intraop wake-up test following completion of instrumentation to evaluate gross motor movement of UE & LE
complications include: (3)
○Inadvertent extubation
○Air embolism
○Violent movements → movement of instrumentation
Somatosensory Evoked Potentials (SSEPs) are associated with what spinal column and sensations?
Dorsal column pathways (afferent)
- Proprioception
- Vibration
*impulse from peripheral nerve measured centrally
Motor Evoked Potentials (MEPs) are associated with what spinal column and sensations?
Anterior/ Motor Column
*impulse triggered in brain –> monitored in specific muscle group (UE & LE)
Adverse effects for MEP include: (6)
● Cognitive defects
● Seizures
● Intra-op awareness
● Scalp burns
● Cardiac arrhythmias
● Bite injuries:
○Soft bite block b/w molars
○Prevents tongue biting/dental injury
MEP monitoring is contraindicated if (3)
patients with…
-active seizures
-vascular clips in the brain
-cochlear implants
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.
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 - Volatile agents
How do VAAs affect neurophysiologic agents?
Dose dependent
- ↓ amplitude
- ↑ latency
** can avoid this by using TIVA
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.
If you have to use VAA at what dose do you run them at for MEP monitoring
@ 0.5 MAC
- avoid N2O: decreased amplitude; eliminate during MEP monitoring
How much does muscle relaxant requirements increase when using MEPs?
Trick question. No muscle relaxants after intubation.
if there are acute changes in amplitude/latency during monitoring what are the 3 things you should consider
d/c surgery
check BP –> (normal to 20% baseline)
decrease or d/c volatile agents
4 things that may signal that you need post-op ventilation after spinal surgery
■Prolonged procedures
● > 4 hrs → assess for edema
○Leak test
●Consider extubating over tube
exchanger
■Thoracic cavity invasion
■EBL > 30 mL/kg or > 2000mL
■Facial/laryngeal edema
Multimodal approach for pain management for postop pain w/ spinal surgeries include…
-PCA pumps
-wound local anesthetic infiltration
-intrathecal morphine
-epidural
-peripheral nerve block
** avoid NSAIDS (ex: ketorolac)
Continuous epidural infusion for postop pain management includes what considerations
○Double epidural techniques for multiple levels
○Consider initial dose of opioids rather than local anesthetic
○Hydromorphone PF (preservative free) 0.5-1 mg
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
