Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
153 Cards in this Set
- Front
- Back
|
Primary mechanisms of nerve injury (4)
|
A. Transection
B. Compression C. Stretch/Traction D. Kinking |
|
|
A Transection nerve injury is caused by?
|
surgical maneuvers or trauma
|
|
|
A Compression nerve injury is caused when?
|
when a nerve is pressed against a bone or hard surface
|
|
|
A Stretch/Traction nerve injury is caused when?
|
when a nerve (i.e. brachial plexus) has a long course across multiple structures.
|
|
|
A Kinking nerve injury is caused when?
|
when a peripheral nerve is pinched between 2 immovable structures
|
|
|
What is a common component of injury related to positioning?
|
ISCHEMIA
|
|
|
Intraneural blood flow can be compromised by: (3)
|
stretch, compression or disruption of the nerve.
|
|
|
Occlusion of major vessels, emboli, tissue edema, or inhibition of perfusion at the capillary level can also lead to:
|
ischemia
|
|
|
A vicious cycle of ischemia results as tissue pressures __ preventing the movement of fluid & nutrients from capillaries into cells
|
increase (edema)
|
|
|
Susceptibility of positioning related nerve injury lies in:
|
the Structure of the Nerve Fiber
|
|
|
Each nerve fiber is composed of one or more ____
|
Axons
|
|
|
AXONS sheathed by ___, which can be ___ or ___
|
1. Schwann cells (neurolemma) – 2. myleinated or non-myleinated.
|
|
|
The endoneurium covers what? (2)
|
Axons and Neurolemma
|
|
|
What is the endoneurium made out of?
|
loose connective tissue
|
|
|
How many layers does the Epineurium have?
|
2
|
|
|
What is the function of the inner & outer layer of the epineurium?
|
Inner: supports fascicles
Outer: covers the external surface of the nerve |
|
|
What supplies the Epineurium and Endoneurium?
|
an extensive microvascular supply
|
|
|
Connections of the microvascular epi/endoneurium supply run ___ b/n the ___&___ capillaries
|
obliquely b/n the Perineurium & Endoneurial capillaries
|
|
|
What makes the perineurium and endoneurium more at risk for compression?
|
b/c their capillaries run obliquely b/n the perineurium & endoneurial capillaries
|
|
|
Patient Factors Contributing to Nerve Damage (11)
|
obesity, malnutrition, big muscles, anemia, DM, PVD, liver disease, periph neuropathies, ETOH, limited joint mobility, & smoking.
|
|
|
Positioning Devices that contribute to nerve injury (7)
|
ax-roll, tight straps, leg holders/stirrups, bolsters, shoulder braces, ether screen, headrests, & positioning frames
|
|
|
A length of procedure lasting more than ___-___hrs may contribute to nerve injury
|
4-5 hours
|
|
|
What Anesthetic Techniques may contribute to nerve injury? why? (3)
|
GA (can't respond to pain of position), NM blockade (unnatural stretching), & Hypotensive techniques (ischemia)
|
|
|
One of the most frequently reported neuropathies is?
|
Ulnar
|
|
|
Ulnar neuropathy is more common in ___ than ___
|
men than women
|
|
|
Ulnar neuropathy is seen more in what kind of hospitals?
|
long term hospitals
|
|
|
What type of nerve injury is a common complication of cardiac surgery?
|
ulnar nerve
|
|
|
What nerve is sheathed in the cubital tunnel of the olecranon? What is this risk for?
|
Ulnar-a potential area for compression b/c the canal changes shape w/ flexion/ extension of the forearm.
|
|
|
Flexion of the elbow may cause?
|
increased risk of ulnar nerve damage
|
|
|
How should you position a pt to prevent ulnar nerve damage? (4)
|
use padding, arms in supinated position, & abducting arms <90* on arm boards.
|
|
|
The Brachial plexus arises from what nerve roots? (6) which divide into what?
|
(C4, 5, 6, 7, 8, & T1), which divide into TRUNKS
|
|
|
How is the brachial plexus arranged? (5)
|
Nerve roots ->Trunks-> Divisions ->Cords ->Terminal Branches
|
|
|
Brachial plexus TRUNKS: (3) which breaks into what?
|
(Superior, Middle, & Inferior),
which pass over the ribs & breaks into DIVISIONS |
|
|
Brachial Plexus DIVISIONS:
As the divisions pass into the infraclavicular region, the divisions separate into: |
(3-Ventral & 3-Dorsal)
CORDS |
|
|
The brachial plexus cords each divide into:
|
terminal branches
|
|
|
What are the terminal branches of the brachial plexus? (3)
|
(Lateral, Medial, Posterior)
|
|
|
The brachial plexus Lateral terminal branch goes to what nerves? (2)
|
Musculocutaneous & Median nerves
|
|
|
The brachial plexus Medial terminal branch goes to what nerves? (3)
|
Ulnar, Median, & Median Cutaneous
|
|
|
The brachial plexus Posterior terminal branch goes to what nerves?
|
Axillary & Radial
|
|
|
What nerves is at high risk for a STRETCH injury?
|
the nerves of the Brachial plexus
|
|
|
Why is the brachial plexus at a high risk for a STRETCH injury? (2 reasons)
|
1. It's fixed b/n its origins at the vertebral foramina & the terminal branches
2. b/c the clavicle, 1st rib, & humeral head may compress or stretch the plexus as it passes by. |
|
|
What structure is at risk of damage in nearly all pt positions?
|
the brachial plexus
|
|
|
What positions pose the greatest risk for brachial plexus injury? (4)
|
arms abducted, shoulders depressed, head rotated, or sternal retraction for cardiac surgery
|
|
|
Any surgery where there's potential for interrupting blood supply to the spinal cord can lead to? (2)
|
quadriplegia & paraplegia
|
|
|
What surgeries may lead to quadriplegia or paraplegia?
|
Any surgery where there's potential for interrupting blood supply to the spinal cord
|
|
|
When the head is flexed, the spinal cord moves __ & may be ___
|
moves anteriorly & may be compressed
|
|
|
Why is the spinal cord at risk for decreased blood supply when it's flexed or stretched? This may lead to?
|
B/c it's like a rubber band, when stretched in a flexed position, the size of the blood vessels supplying the cord can decrease – leading to ischemia.
|
|
|
Increased vertebral Venous pressure leads to:
|
postop spinal cord injury
|
|
|
Are there valves in the central or epidural venous systems?
|
No
|
|
|
B/c there are no valves b/n the central & epidural venous systems, any change in intrathoracic or abdominal pressure directs to:
|
the vertebral venous system
|
|
|
What might happen if there's congestion in the veins draining the spinal cord, or hypotension? (2)
|
decreased spinal cord perfusion & neuro defects.
|
|
|
Post-op vision loss is (common or rare)?
|
Rare
|
|
|
Post-op vision loss can range from?
|
Decreased visual acuity to total blindness (in one or both
eyes) |
|
|
The retina and optic nerves are supplied by: (2)
|
The central retinal artery &
long/short posterior ciliary arteries |
|
|
The central retinal artery &
long/short posterior ciliary arteries that arise from: |
The internal carotid artery
|
|
|
Blood flow is (lower/higher) in the posterior optic nerves?
|
lower
|
|
|
Why is blood flow is lower in the posterior optic nerves? What risk does this cause?
|
These arteries lack autoregulation – making them susceptible to hypoperfusion in times of hypoTn.
|
|
|
Any diseases that disrupt visual autoregulatory mechanisms can contribute to: 1 (2 ex:)
|
ischemia (ex: HTN, DM)
|
|
|
Generally postop visual loss is due to: (5)
|
1. Ischemic optic neuropathy (ION)
2. Central retinal artery occlusion (CRAO) 3. Central retinal vein occlusion 4. Cortical blindness 5. Glycine toxicity |
|
|
Ischemic Optic Neuropathy is commonly due to:
|
decreased perfusion & increased intraocular pressure
|
|
|
Ocular perfusion pressure (OPP) =
|
(OPP) = MAP – Intraocular pressure (IOP)
|
|
|
(OPP) = MAP – Intraocular pressure (IOP), therefore event that reduce MAP cause what?
|
events that reduce MAP (anesthesia, hypotension, hypovolemia, hemorrhage) reduce OPP.
|
|
|
An increase in ocular venous pressure can:
|
In increase in venous pressure occlude aqueous humor outflow from the eye, causing a rise in IOP.
|
|
|
As IOP rises toward MAP, OPP will____leading to?
|
OPP will decrease leading to ischemia/visual damage
|
|
|
Central Retinal Artery Occlusion (CRAO) is (more/less) common than ION?
|
less
|
|
|
Emboli from the internal carotid can migrate where in ocular system and cause what?
|
the central retinal artery & cause blindness.
|
|
|
What may cause Central Retinal Artery Occlusion (CRAO) include: (3)
|
cardiopulmonary bypass, hypotension, & increased extraocular pressure
|
|
|
Central Vein Occlusion risk factors: (5)
|
HTN, CV disease, increased BMI, open angle glaucoma, & sickle cell anemia.
|
|
|
During a procedure, what may cause Central Vein Occlusion?
|
external pressure on the globe
|
|
|
Cortical Blindness results from: (2)
|
ischemia or trauma & a subsequent infarction of the visual pathways in the parietal or occipital lobes
|
|
|
Operative causes of Cortical Blindness: (3)
|
air/particulate emboli, cardiopulmonary bypass,
hypoperfusion (d/t hemorrhage/hypotension) |
|
|
How common is Glycine Toxicity?
|
Rare
|
|
|
Glycine Toxicity is a syndrome seen in patients with:
|
L-arginine deficiency (the
enzyme needed to metabolize ammonia) |
|
|
What is L-arginin?
|
the enzyme needed to metabolize ammonia
|
|
|
How is vision restored in patients with glycine toxicity?
|
Vision loss is temporary, vision returns when blood ammonia levels decrease
|
|
|
Compartment Syndrome is a life-threatening complication that causes damage to:
|
neural and vascular
structures from swelling of tissues within a muscular compartment. |
|
|
What may cause compartment Syndrome intraoperatively? (6)
|
long procedures, positions, elevated extremities, intraoperative hypoTn, inc'd age, & extremes of body habitus
|
|
|
Treatment of Compartment Syndrome:
|
fasciotomy to release the constricted compartments
|
|
|
What causes Compartment Syndrome?
|
increased pressures & decreased tissue perfusion in muscles with tight fascial borders
|
|
|
What results from Compartment Syndrome?
|
arterial supply becomes compromised and results in ischemia & nerve infarction
|
|
|
Causes (non-intraoperative) of Compartment Syndrome: (7)
|
trauma, embolic phenomenon, tumors, vascular insufficiency, tight wound closure, expanding hematoma, & external compression
|
|
|
What positions are pts at greatest risk for venous air embolism (VAE)?
|
Sitting -OR- any position in which a (-) pressure gradient exists b/n the R. atrium and the veins at the operative site.
|
|
|
Complications of VAE: (1+5)
|
- proportional to the volume & rapidity of air entrainment.
- Range from no effect to hypoTn, arrhythmias, cardiac arrest, & death |
|
|
PAE (paradoxical air embolism) can occur with: (2)
|
a PFO or when right atrial pressures > left atrial pressures.
|
|
|
Detection of air embolism: (whats the gold standard +1)
|
TEE is gold standard
Doppler *listen for “mill-wheel murmur” |
|
|
Where do you place the doppler when monitoring for VAE?
|
probe is placed over the 3rd-6th intercostals spaces to the right of the sternum
|
|
|
ETT moves (up/down) with flexion, and (up/down) with extension?
|
downward w/ flextion
upward w/ extension |
|
|
When pts are in steep head down position, ETT can move where?
|
right mainstem
|
|
|
3 ETT Complications of Surgical positions
|
1. Move with flexion/extension
2. Right mainstem 3. Kink |
|
|
ETT can become kinked and cause:
|
postop supraglottic edema
|
|
|
Supine position is used for which types of procedures? (5)
|
abdominal, head, neck, chest, & extremities
|
|
|
How should the head be positioned when pt in the supine position? why?
|
Head should be neutral on pad/ pillow/ donut (prevents brachial plexus injury)
|
|
|
What other interventions should you do when the pt is in the supine position? (3)
|
1. Support lumbar spine (IV bag)
2. Pad heels 3. legs uncrossed |
|
|
How should you position the arms when they are tucked at pts side?
|
hands parallel to legs & trunk, or abducted <90* on padded armboards w/ hands supinated.
|
|
|
What surgical procedures are pts placed in the prone position? (3)
|
Spinal procedures, intracranial, buttocks
|
|
|
How should the torso be supported when the pt is in the prone position? (3)
|
Supported on a frame, rolls extending from shoulders to iliac crest, or supports placed crosswise at shoulders & pelvis as well
|
|
|
How should the Legs be positioned with pts in the prone position?
|
legs should be supported with pillows
|
|
|
How should the Arms be positioned with a pt in the prone position? (2)
|
tucked at sides, or on armboards w/ arms flexed at shoulders & elbows.
|
|
|
What should especially be padded when the pt is in the prone position? (5)
|
elbows, knees, ankles, genitalia, & underneath shoulders (to prevent brachial plexus injury)
|
|
|
How should the Head be positioned with a pt in the prone position? (2)what should be protected? (2)
|
neutral position, supported midline – (protect eyes, nose from pressure)
|
|
|
What consideration for the abdomen should you have when a pt is prone? why?
|
Avoid pressure over the abdomen (b/c can impede venous return, increase venous pressures, & interfere w/ ventilation)
|
|
|
What procedures are pts placed in the Lithotomy position?
|
procedures where access to perineal structures is needed
|
|
|
How are legs positioned?
|
Legs are held in flexion & abduction above the level of the torso w/ a device.
|
|
|
What are 3 different Lithotomy positions?
|
low, standard, or exaggerated lithotomy
|
|
|
How should arms be positioned when pt in Lithotomy position? (2)
|
tucked at sides or on armboards (same as supine)
|
|
|
What consideration should be made when actually positioning pt legs for Lithotomy position? why?
|
Raise the legs together (b/c raising them separately can cause hip dislocation or postop back/hip pain).
|
|
|
When in lithotomy position, avoid flexion >___.* why?
|
90*
-can kink or compress femoral neurovascular structures. |
|
|
Extreme flexion of the knee when in Lithotomy position can: (adverse rxn)
|
occlude the popliteal vein
|
|
|
When in Lithotomy position, when nerve is susceptible to injury at the knee? how should you protect it?
|
Peroneal nerve – pad carefully
|
|
|
Lateral Decubitus Position is for surgeries involving the: (4)
|
thorax, kidneys, lateral spine, or cranium
|
|
|
What positioning device may be used to support the pt in the Lateral position?
|
Beanbags
|
|
|
What is a very important consideration when a pt is in the Lateral position?
|
Body alignment very important – (shoulders, hips, head, & legs
maintained in the same plane) |
|
|
When adjusting a pt in the Lateral position, what should be done to prevent twisting?
|
shoulders, hips, head, and legs
maintained in the same plane & turned simultaneously |
|
|
How should the head be positioned in a pt in the Lateral position?
|
Head and neck neutral – pillow, donut, etc
|
|
|
Angulation of neck of a pt in the Lateral position can cause: (4-adv. rxn)
|
occlusion of vertebral or carotid arteries, impair perfusion to the head, impair jugular venous drainage, & increase intracranial pressure
|
|
|
When positioning a pt in the Lateral position, what can be done to stabilize the pt?
|
Flex the dependent knee & hip to stabilize position - pillow b/n legs
|
|
|
How should the arms be positioned with a pt in the Lateral position?
|
Dependent arm on armboard, <90*, nondependent arm usually parallel at the level of the shoulder.
|
|
|
When pt in Lateral position, must check _(4)_ for perfusion
|
radial pulses, eyes, ears, & nose carefully
|
|
|
What is essential when placing a pt in the Lateral position to prevent injury?
|
Axillary roll
|
|
|
How should an Axillary roll be placed? whats the fxn of the ax roll? (3)
|
caudal but not directly under the axilla
(helps to decompress the shoulder, axillary vessels, & brachial plexus). |
|
|
What are the most common nerve injuries of a pt in the Lateral position? (3)
|
Ulnar, Brachial Plexus, & Peroneal
|
|
|
When is a pt positioned in the Sitting position? (5)
|
posterior fossa, cervical spine, mammoplasty, breast reconstruction, shoulder arthroplasty.
|
|
|
A pt is considered to be in the sitting position when?
|
Pt in any position in which the torso is elevated from the supine position & is higher than the legs
|
|
|
What may be used to stabilize the head when a pt is in the sitting position for a neuro procedure?
|
3-pin head holder (mayfield tongs)
|
|
|
When a pt in 3-pin head holder (mayfield) what should be assessed to prevent jugular obstruction?
|
assure 2 fingerbreadths of space b/n neck & mandible to prevent jugular venous obstruction.
|
|
|
What other device may be used to stabilize the head in a pt in the Sitting position?
|
Horseshoe headrests are used for other procedures with a head strap
|
|
|
What reflex may be activated during profound hypoTn or brady in a pt in the Sitting position?
|
Benzold-Jarish reflex
|
|
|
When might the Benzold-Jarish reflex occur?
|
occurs when shoulder surgery is done with interscalene blocks.
|
|
|
What is the Benzold-Jarish reflex?
|
responds to noxious ventricular stimuli sensed by chemo/ mechano-receptors within the LV wall (during shoulder surg w/ interscalene block)
|
|
|
What triad of symptoms occurs with the stimulation of the Benzold-Jarish reflex?
|
A triad of hypoTn, bradycardia, & coronary artery dilatation.
|
|
|
Complications of the Sitting position: (4)
|
VAE, pneumocephalus, quadriplegia, & peripheral
nerve injuries. |
|
|
What is the Trendelenberg position?
|
Head-down – any position where the head is lower than the rest of the body
|
|
|
Complications od the Trendelenberg position: 1(2)
|
d/t positioning tools most often. Shoulder braces (cause brachial plexus damage), Wrist restraints (cause traction on the arm)
|
|
|
Arms in ___position are at risk for nerve injury d/t pinching,
hyperextension, etc. |
Any
|
|
|
Hemodynamic effects of positioning on CO & BP:
|
Both decreased w/ GA – therefore blood pools in dependent areas which reduces preload & decreases stroke vol.
|
|
|
(Hemodynamic effects of positioning) Neuromuscular blocking agents further contribute to:
|
decreased venous return
|
|
|
Hemodynamic effects of positioning & Opioids/volatile agents, will see _ HR → _ CO → _BP.
|
decrease HR → decreased CO → decreased BP.
|
|
|
Hemodynamic effects of positioning on MAP: +(1 exception)
|
Normally, MAP is maintained by increases in HR and SVR – (elderly pts are less adaptive)
|
|
|
Hemodynamic changes are minimal in __ & __ positions
|
supine & lateral positions
|
|
|
__, __, & __ positions lead to decreased CO and BP
|
Sitting, Prone, & Flexed lateral positions
|
|
|
In the sitting position, MAP decreases by __mmHg for each cm change in ht. b/n heart & body region
|
MAP decreases by 0.75mmHg
|
|
|
(Resp effect of positioning) Any postural changes can alter: (4)
|
compliance, lung volumes, distribution of ventilation, & pulmonary blood flow
|
|
|
(Resp effect of positioning) In both awake and anesthetized patients, gravitational forces create:
|
a gradient that favors perfusion in dependent portions of the lung & ventilation in nondependent regions.
|
|
|
(Resp effect of positioning) What is better in the prone position? (2)
|
Ventilation is more uniform -&- V/Q matching is better
|
|
|
(Resp effect of positioning) How is ventilation effected in the Lateral position with the pt awake?
|
ventilation & perfusion are greater in the dependent lung than non-dependent lung in awake patients.
|
|
|
Resp effect of an anesthetized pt in the Lithotomy position?
|
Can cause decreased ventilation perfusion ratios & lung aeration
|
|
|
HPV in the unventilated lung distributes blood flow to: what is a benefit of this?
|
the dependent lung (improves ventilation in procedures involving the lateral position & one-lung ventilation).
|
|
|
What can be done with vent to compensate for decreases in oxygenation when in lateral position? (2)
|
Adjust TV's to 5-7ml/kg & increase respiratory rate
|
|
|
What happens to abd contents, diaphram, & ventilation in anesthetized lateral pt?
|
abd contents shift Cephalad, moving the hemidiaphragm of the dep. lung upward & dec'ing ventilation in the dept lung, reducing compliance.
|
|
|
In an anesthetized lateral pt, Ventilation in the nondependent lung is ___ along with compliance. why?
|
Increased (b/c the caudal shift of the upper hemidiaphragm allows unrestricted lung excursion).
|
|
|
What respiratory effect may happen as a result of being in the extreme Lithotomy?
|
can compress the abd, shift the viscera cephalad, & limit diaphragmatic mvmt – therefore decreasing compliance & TVs.
|
|
|
How does being in the Trendelenberg position effect FRC?
|
causes decreased FRC w/ each * of trendelenberg
|
|
|
What happens in the resp system if there is mvmt of the mediastinum towards the head?
|
moves the carina closer to the ETT & can cause one lung (right-mainstem) ventilation.
|
