Week 11 - OR Positioning Flashcards
What causes nerve injury with patient positioning?
Stretch Compression Ischemia Metabolic derangement Direct trauma/laceration during surgery
Predisposing factors (pre-existing peripheral neuropathy – diabetes, PVD)
What is a neutral position?
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
What are the major types of positions used in the OR?
Supine: Trendelenburg, reverse Trendelenburg, lawn chair
Prone: jack knife
Lithotomy
Sitting: fowlers (HOB 45-60 degrees, high, low semi), beach chair
What reflexes respond to position changes?
Baroreceptor Reflexes
Mechanoreceptors (atrium, ventricle)
Atrial Reflexes
*GA can interfere with these reflexes – vasodilation, decreased venous return, contractility
What position are GA patients particularly prone to hypotension? How do you combat it?
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
In the Beach Chair sitting position where do you level the a-line?
at the EAC
How does FRC change from upright to supine position?
FRC decreases by 0.5-1.0 L
- especially in obesity and pregnancy
- increases aspiration risk
What are the physiologic changes when in Trendelenburg?
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)
What are the physiologic changes when in Reverse Trendelenburg?
Hypotension
Decreased venous return
Pressure areas on feet if foot table in place
Improves respiratory mechanics
Why are knees and hips slightly flexed in the lawn chair position?
to reduce stress on the lower back, hips, and knees
*better tolerated by patients who are awake or undergoing a MAC
What are the possible risk factors for perioperative visual loss?
- 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
What are the ASA advisory’s specific positioning strategies for the upper extremities?
- 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
What is the ASA advisory’s summary of positioning for supine patient with arms tucked at side?
- 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
What are the ASA advisory’s specific positioning strategies for the lower extremities?
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
What is the most frequently damaged nerve in the lower extremity due to positioning?
Common peroneal nerve (common fibular nerve)
According to the ASA advisory, where should protective padding be placed for the upper extremity?
- 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
According to the ASA advisory, where should protective padding be placed for the lower extremity?
- 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
What risk factors make a patient high-risk for pressure ulcer development in the OR?
- Procedures lasting >3 hours
- Cardiac, vascular, trauma, transplants, bariatric procedures
- BMI <19 or >40
- Impaired sensation
- History of pressure ulcer/existing skin breakdown
In supine position where are the areas of increased risk for pressure ulcers?
Scapula
Occiput
Elbows
Sacrum
Coccyx
Heels
In lateral position where are the areas of increased risk for pressure ulcers?
Ear
Acromion process
Trochanter
Medial/Lateral Condyles of knee
In prone/jackknife position where are the areas of increased risk for pressure ulcers?
Nose Forehead Chest Acromion Process Genitalia Breasts Iliac Crests Patella Foot edge and toes
In Trendelenburg/Reverse Trendelenburg position where are the areas of increased risk for pressure ulcers?
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
How often do you document checking of pressure points and reposition the patient?
At least every 2 hours
Describe classic supine position
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
What are complications of the supine position?
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
Describe lithotomy position
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
What are physiologic changes in the lithotomy position?
When legs are elevated – preload increases (transient increase in CO)
Abdominal viscera displaces the diaphragm – reduces lung compliance (possible decrease in tidal volume)
What are complications of the lithotomy position?
Lower back pain
Lower extremity compartment syndrome (rare) – due to decreased perfusion
Describe the lateral decubitus position
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
How does lateral decubitus position change pulmonary function in a mechanically ventilated patient?
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)
Describe prone position
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
What are the physiologic changes in prone position?
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
Describe the sitting position
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
What is the most significant complication from the sitting position?
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
Define Neurapraxia, Axonotmesis, and Neurotmesis
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
What are the perioperative factors associated with an increased risk of intra-ocular ischemia?
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
How long does it take positional related motor neuropathies to recover?
Most take 4 to 6 weeks to recover
