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AP 1 > Test 1 part IX (P) > Flashcards

Test 1 part IX (P) Flashcards

1
Q

What are the 3 primary mechanisms of nerve injury r/t surgical positioning?

A
  1. transection (surgery)
  2. compression (against a bony prominence/hard surface)
  3. stretch (long course across many structures like the brachial plexus)

Common component is ischemia (!!) & compromised intraneural blood flow

During GA, early warning signs such as pain are absent!

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2
Q

-Peripheral nerves are composed of bundles of nerve fibers (fascicles)
-Individual nerve fiber composed of one/more axons sheathed in Schwann cells
-Covered in loose connective tissue: Endoneurium (cover axons & neurolemma), Perineurium (binds fascicles), Epineurium (supports the fascicles & covers the external nerve surface)

A

Nerve Anatomy

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3
Q

What are perioperative risk factors associated with the development of nerve injuries?

A

Positioning devices, prolonged surgical procedures >4 hrs, anesthetic technique

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4
Q

What are patient related factors associated with the development of nerve injuries?

A

Gender (M), advanced age, extremes of body habitus, pre-existing conditions (DM, HTN, tobacco!!!)

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5
Q

What are intraoperative occurrences associated with the development of nerve injury?

A

Hypovolemia, hypotension, hypothermia, hypoxia, electrolyte disturbances

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6
Q

What is the 2nd most frequent etiology of liability claims?

A

Nerve Damage: ulnar nerve, brachial plexus, lumbosacral nerve, spinal cord

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7
Q

Occurs with direct pressure on the cubital tunnel. When elbow is flexed, the cubital tunnel stretches, which increases pressure on the nerve.
-Results in claw-hand contracture (inability to abduct/oppose 5th finger, decreased sensation to 4th/5th fingers, atrophy of intrinsic hand muscles)

A

Ulnar Nerve Injury

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8
Q

At high risk for stretch and compression injuries due to long, superficial course (neck to axilla).
-Abduction of the arms >90 stretches plexus at the humerus & lateral head turning stretches/compresses the contralateral plexus beneath the clavicle
-Associated with the use of positioning devices: unsecured arm slipping off armboard, armboard falls from OR table, shoulder braces, sternal retractors

A

Brachial Plexus Injury

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9
Q

How do you prevent a brachial plexus injury?

A

-Head neutral position
-Arms <90 abduction
-Use of straps to secure arms to armboards
-Proper use of positioning devices/ equipment/braces
-Axillary roll in the lateral position
-Use of ultrasound for RA & venous access

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10
Q

What is the result of injury to the Median Nerve?

A

Thenar Atrophy

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11
Q

What is the result of injury to the Radial nerve?

A

Wrist Drop

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12
Q

Primarily associated with neuraxial blocks in anticoagulated patients.
-Avoid extreme cervical flexion or extension in any position.
-Prevent with proper padding!

A

Spinal cord injury

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13
Q

How do you avoid a spinal cord injury in the Sitting & Prone positions?

A

Watch mid-cervical flexion (continue use of SSEPs), Avoid straight leg position (use of pillows under knees to prevent stretching of lumbar spine)

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14
Q

How do you avoid a spinal cord injury in Lithotomy?

A

Minimize excessive hip flexion, knee extension, torsion of spine
Watch pressure to peroneal nerve at fibula
Move both legs into/out of position simultaneously
-Risk for compression between fibula head & lithotomy stirrup/leg holder or OR table

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15
Q

The most common type of perioperative eye injury. Due to loss of protective eye reflexes under GA, associated with direct trauma to cornea.

A

Corneal Abrasion

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16
Q

Transient symptoms: decreased tear production, swelling, complaints of foreign body sensation

Treatment with supportive care, antibiotic ointment

A

Corneal Abrasion

17
Q

How do you prevent a corneal abrasion?

A

Early & careful taping of eyes after induction, Caution when leaning over patients, Close observation during emergence to prevent rubbing of the eyes

18
Q

The optic nerve is susceptible to hypoperfusion; this accounts for 89% of POVL cases.

A

Ischemic Optic Neuropathy (ION)

19
Q

POVL occurs due to decreased blood supply to the entire retina

A

Central Retinal Artery Occlusion (CRAO)

20
Q

What are factors associated with the development of POVL?

A

-Periop factors: long surgical procedure, prone or steep trendelenburg position, significant blood loss, hypotension
-Patient factors: HTN, DM, vascular, obesity, tobacco

21
Q

How to reduce the risk of POVL?

A

1.Avoid direct pressure on eye
2. Perform & document periodic eye checks throughout perioperative period
3. Minimize venous pressure & congestion in the head (keep head in a neutral position at or above heart level)
4. Minimize bleeding (avoid coagulopathy)
5. Decrease duration of prone position
6. Avoid significant hemodynamic changes

22
Q

May occur in any position if negative pressure gradient exists between heart and operative site, however, most common in the sitting position.

A

Venous Air Embolism (VAE)

23
Q

Occurs when air enters the right heart, limiting gas exchange in lungs as blood is displaced in pulmonary vasculature.
-Complications are dependent on the rate and volume of air entrainment.

A

Venous Air Embolism (VAE)

24
Q

There is a paradoxical air embolism associated with PFO in about ____ of the population.

A

35%

25
Q

What are the physiologic effects of VAE?

A

No effect, hypotension, arrhythmias, micro-air embolism resulting in MI/CVA, cardiac arrest, death

26
Q

What is the gold standard for detection of VAE?

A

TEE

27
Q

The most sensitive non-invasive monitor, Placed over 3rd to 6th intercostal space to right of sternum.

A

Precordial Doppler

28
Q

Presence of a sudden drop or no EtCO2 & presence of EtN2 on capnography can indicate:

A

VAE

29
Q

Distinctive sound heard through the esophageal or precordial stethoscope that indicates VAE.

A

Mill-Wheel Murmur (!!)

30
Q

What is the treatment for a VAE?

A
  1. Notify the surgeon to flood the surgical field with NS!
  2. FiO2 1.0 and hemodynamic support
  3. Consider CVC placement to allow aspiration of air
  4. Put patient on left side so then air rises and can suck the air out with CVC
31
Q

What positioning/preventative steps do you take to prevent Ulnar Nerve Injury? (!!)

A
  1. Use of padding
  2. Arms in a supinated/neutral position (palms facing up & in)
  3. Abduction of arms <90 degrees on armboard
  4. If the patient’s arms are tucked at the side of the body, they should be in a neutral position with the palms facing inward.
  5. Assess arms - do they feel tense?
32
Q

Factors that significantly and independently increase the risk of ION associated with spine surgery in the prone position include: (!!)

A
  1. Male sex
  2. Obesity
  3. Use of Wilson frame
  4. Longer surgical duration
  5. Larger blood loss
  6. A lower percentage of colloid in the non-blood fluid administration.

AP 1 (32 decks)

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