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Scientific Principles > Week 11 - OR Positioning > Flashcards

Week 11 - OR Positioning Flashcards

1
Q

What causes nerve injury with patient positioning?

A 
Stretch
Compression
Ischemia
Metabolic derangement
Direct trauma/laceration during surgery

Predisposing factors (pre-existing peripheral neuropathy – diabetes, PVD)

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2
Q

What is a neutral position?

A

Position that has the least strain and stretch on joints, muscles, and nerves

  • put yourself in that position – is it comfortable?
  • assess pre-op position tolerance
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3
Q

What are the major types of positions used in the OR?

A

Supine: Trendelenburg, reverse Trendelenburg, lawn chair

Prone: jack knife

Lithotomy

Sitting: fowlers (HOB 45-60 degrees, high, low semi), beach chair

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4
Q

What reflexes respond to position changes?

A

Baroreceptor Reflexes

Mechanoreceptors (atrium, ventricle)

Atrial Reflexes

*GA can interfere with these reflexes – vasodilation, decreased venous return, contractility

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5
Q

What position are GA patients particularly prone to hypotension? How do you combat it?

A

Sitting Position because of the pooling of blood into the lower body

  • incremental positioning
  • use IV fluids
  • vasopressors
  • appropriate adjustments of anesthetic depth
  • keep MAP at the patients baseline
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6
Q

In the Beach Chair sitting position where do you level the a-line?

A

at the EAC

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7
Q

How does FRC change from upright to supine position?

A

FRC decreases by 0.5-1.0 L

  • especially in obesity and pregnancy
  • increases aspiration risk
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8
Q

What are the physiologic changes when in Trendelenburg?

A

Increased venous return and aspiration risk (place OG)

Increased intracranial and intraocular pressure, as well as increased facial/laryngeal edema which can lead to post-op airway obstruction

FRC and pulmonary compliance are reduced by the dislocated viscera (pressure control volume guarantee mode is good for this)

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9
Q

What are the physiologic changes when in Reverse Trendelenburg?

A

Hypotension

Decreased venous return

Pressure areas on feet if foot table in place

Improves respiratory mechanics

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10
Q

Why are knees and hips slightly flexed in the lawn chair position?

A

to reduce stress on the lower back, hips, and knees

*better tolerated by patients who are awake or undergoing a MAC

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11
Q

What are the possible risk factors for perioperative visual loss?

A
  • Vascular risk factors increase the risk
  • Preoperative presence of anemia
  • Prone position
  • Prolonged procedures (exceed an avg of 6.5 hours duration)
  • Substantial blood loss (when loss reaches an avg of 44.7% of estimated blood volume)

*Prolonged procedures combined with substantial blood loss all increase the risk of perioperative visual loss

Perioperative visual loss = ischemic optic neuropathy – NOT reversible

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12
Q

What are the ASA advisory’s specific positioning strategies for the upper extremities?

A
  • Arm abduction in supine patients should be limited to 90*
  • Patients who are positioned prone may comfortably tolerate arm abduction greater than 90*
  • Supine patient with arm on an arm board: upper extremity should be positioned to decrease pressure on the postcondylar groove of the humerus (ulnar groove) – either supination or the neutral forearm positions facilitates this action
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13
Q

What is the ASA advisory’s summary of positioning for supine patient with arms tucked at side?

A
  • Forearm should be in a neutral position
  • Flexion of the elbow may increase the risk of ulnar neuropathy, but there is no consensus on an acceptable degree of flexion during periop period
  • Prolonged pressure on the radial nerve in the spiral groove of humerus should be avoided
  • Extension of the elbow beyond the range that is comfortable during preop assessment may stretch the median nerve
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14
Q

What are the ASA advisory’s specific positioning strategies for the lower extremities?

A

Hip Flexion of 120* or less laterally — prevents sciatic neuropathy from stretching of the hamstring muscle beyond a comfortable range of motion

Hip Flexion of 90* or less — prevent femoral neuropathy

Avoidance of contact with hard surfaces or supports that apply direct pressure on the fibular head or lateral tibia — prevent peroneal (fibular) neuropathy

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15
Q

What is the most frequently damaged nerve in the lower extremity due to positioning?

A

Common peroneal nerve (common fibular nerve)

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16
Q

According to the ASA advisory, where should protective padding be placed for the upper extremity?

A
  • Padded arm boards
  • Specific padding (foam or gel pads) at the elbow
  • For patient in a lateral position, use a chest roll positioned under the chest to protect the brachial plexus
  • Avoidance of padding that is excessively tight or restrictive
17
Q

According to the ASA advisory, where should protective padding be placed for the lower extremity?

A
  • Specific padding between the outside of the leg below the knee to prevent contact of the peroneal nerve (at the fibular head) with a hard surface
  • Avoidance of padding that is excessively tight or restrictive
18
Q

What risk factors make a patient high-risk for pressure ulcer development in the OR?

A
  • Procedures lasting >3 hours
  • Cardiac, vascular, trauma, transplants, bariatric procedures
  • BMI <19 or >40
  • Impaired sensation
  • History of pressure ulcer/existing skin breakdown
19
Q

In supine position where are the areas of increased risk for pressure ulcers?

A

Scapula

Occiput

Elbows

Sacrum

Coccyx

Heels

20
Q

In lateral position where are the areas of increased risk for pressure ulcers?

A

Ear

Acromion process

Trochanter

Medial/Lateral Condyles of knee

21
Q

In prone/jackknife position where are the areas of increased risk for pressure ulcers?

A 
Nose
Forehead
Chest
Acromion Process
Genitalia
Breasts
Iliac Crests
Patella
Foot edge and toes
22
Q

In Trendelenburg/Reverse Trendelenburg position where are the areas of increased risk for pressure ulcers?

A

Risk for shear injuries when changing from supine to trendelenberg

take measures to prevent patient from sliding

shoulder bars and foot boards may cause pressure injuries

23
Q

How often do you document checking of pressure points and reposition the patient?

A

At least every 2 hours

24
Q

Describe classic supine position

A

Head, neck, and spine all retain neutrality

One or both arms can be abducted or adducted alongside the patient (abduction <90 degrees)

Hands/Forearms either supinated or kept neutral with palm toward the body

*Pad all bony prominences and stopcocks/IV lines

25
Q

What are complications of the supine position?

A

Backache – normal lumbar lordotic curvature is lost

Beware of the direction the patient is placed on the table – if reversed the majority of their weight is over the open side of the table

26
Q

Describe lithotomy position

A

Legs are abducted 30-45 degrees from midline

Knees are flexed and legs are held by supports

Hips are flexed to varying degrees depending on procedure (standard, low, or high lithotomy)

Position hands far away from the break in the table to prevent them from getting pinched

  • raise and lower legs simultaneously – prevents spine torsion
  • pad lower extremities to prevent compression against leg rests
27
Q

What are physiologic changes in the lithotomy position?

A

When legs are elevated – preload increases (transient increase in CO)

Abdominal viscera displaces the diaphragm – reduces lung compliance (possible decrease in tidal volume)

28
Q

What are complications of the lithotomy position?

A

Lower back pain

Lower extremity compartment syndrome (rare) – due to decreased perfusion

29
Q

Describe the lateral decubitus position

A

Patient lies on the non-operative side – beanbag/bed rolls used to keep pt on their side

Dependent leg should be somewhat flexed

Dependent arm is placed in front of pt on a padded arm board

Non-dependent arm is supported over folded bedding or suspended in an armrest

Place chest (axillary) roll under the patient just below the axilla on the chest

Keep head in neutral position

30
Q

How does lateral decubitus position change pulmonary function in a mechanically ventilated patient?

A

the combo of the lateral weight of the mediastinum and disproportionate cephalad pressure of abdominal contents on the dependent diaphragm decreases compliance of the dependent lung and favors ventilation of the nondependent lung

Pulmonary blood flow to dependent lung increases – V/Q mismatching (can affect alveolar ventilation and gas exchange)

31
Q

Describe prone position

A

Head is maintained in a neutral position with use of special pillows

Legs should be padded and flexed slightly at knees and hips

Both arms may be at the patient’s sides, tucked in the neutral position or placed next to the head on arm boards – don’t exceed 90*
–absolute contraindication to having arms next to head is if pt has pain or numbness in arms when lifting above his head

Thorax should be supported by firm rolls or bolsters placed along each side from clavicle to iliac crest – abdomen should hand relatively freely

32
Q

What are the physiologic changes in prone position?

A

Hemodynamics are well maintained

Pulmonary function is superior to the supine position – FRC is increased improving oxygenation
*obese pts - compliance is improved with abd hanging freely

33
Q

Describe the sitting position

A

Head must be adequately fixed – use head strap, tape, or rigid fixation

Arms supported and padded – ensure shoulders are even

Knees are slightly flexed – reduce stretching of sciatic nerve

Feet are supported and padded

34
Q

What is the most significant complication from the sitting position?

A

Venous air embolism (VAE)

  • during intracranial procedures, a significant amount of air can be entrained through open dural venous sinuses
  • low venous pressure in the operative field creates gradient for air entry into venous system

*patient should be evaluated to rule-out anatomic intracardiac shunts via TEE – if present VAE could result in a stroke or MI

35
Q

Define Neurapraxia, Axonotmesis, and Neurotmesis

A

Types of Compression injuries due to positioning

Neurapraxia: caused by a relatively short ischemia time and usually causes only a transient dysfunction

Axonotmesis: demyelinating injury

Neurotmesis: due to a severed or disrupted nerve and usually deficits are permanent

36
Q

What are the perioperative factors associated with an increased risk of intra-ocular ischemia?

A 
Prolonged hypotension
Long duration of surgery
Large blood loss
Large crystalloid use
Anemia or hemodilution
Increased intraocular or venous pressure from prone position

Patient risk factors = HTN, DM, atherosclerosis, morbid obesity, tobacco use

37
Q

How long does it take positional related motor neuropathies to recover?

A

Most take 4 to 6 weeks to recover

Scientific Principles (16 decks)

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