Positioning - Exam 3 Flashcards
CVP (preload) and SV will _ in response to blood pooling dependently
decrease
BP effects from NMBD:
decreases venous return due to abolished muscle tone
Under normal circumstances in healthy pt, low BP is compensated for by increased _ and _
HR and SV
GA blocks which compensatory mech for low BP
increased HR
Hemodynamic changes are LEAST likely to be seen as a result from which position/s?
lateral and supine
Which positions are likely to decrease CO and BP
sitting
prone
FLEXED lateral when LE are DEPENDENT
In the prone position what happens to CVP and LV volume?
CVP increases
LV volume decreases
-decreased venous return and increased intrathoracic pressure
Opioids can decreased CO and BP because they can decrease _
HR
GA blunts HR when hypoTN happens, making it more reliant on _ for venous return
gravity
What impact does the prone position have on CI?
can possibly reduce
What can cause BP to APPEAR normal of higher in the lithotomy position?
autotransfusion from gravity redistributing blood in dependent structures more centrally (raising CVP)
Acute issues/ comorbidities contributing to risk for positioning injury:
-body habitus extremes
-preexisting neurological issues
-Arthritis/ joint mobility issues
-DM - neuropathy
-ETOH / liver disease(malnourished)
-PVD
-HTN/HoTN
-anemia
-smoking
-temperature extremes
-old, male
-Anticoags (hematoma risk)
Intraop (equipment) factors influencing positioning injury risk
-table straps
-leg holders/stirrups
-axillary rolls
-bolsters
-shoulder braces
-fracture table post
-positioning frames
-headrests
-ether screen
-case length > 4-5hr
-GA
-HoTN technique
-NMBD
-tourniquette >3hrs
Peripheral nerves consist of a cell body and an _
axon
Axons of peripheral nerves are wrapped in _ _ which form the myelin sheath and this is all surrounded by _ protecting the individual nerve cell
SchwannCells
endoneurium
Collections of nerve fibers (endoneurium) are surrounded by a layer called _
perineurium
The perineurium is encapsulated with other perineuria and blood vessels by a layer called the _, forming the peripheral nerve
epineurium
Injury to the myelin sheath or axon of a nerve can lead to:
-focal conduction block
-degeneration
-demyelination
Arteries inside nerves are called _ _ and they supply the internal nerve and its outside layer
vasa nervorum
Most common cause of nerve injury is ISCHEMIA from _ or _ of the neural vasa nervorum
stretching or compression
MAP increases or decreases by approximately __ mmHg per inch each change in height between the heart and a body region
2
Gravity favors perfusion of ______ portion and ventilation in ________ region
Dependent; Nondependent
In relation to the respiratory system, what is the preferred position and why?
Sitting Position
Forced vital capacity and FRC are within normal parameters. Sitting causes less change in distribution, ventilation and perfusion
What is the most detrimental positions for the respiratory system and why?
Prone Positioning:
-GOOD for ARDS: posterior lung segments better
ventilated and alleviation of pressure of anterior mass
-BAD for Healthy: diaphragmatic excursion limited by
abdominal viscera (free-hanging belly increases FRC)
Lateral Position:
-abdomen displaces diaphragm up, decreasing
ventilation in dependent lung (reducing its compliance) but
increasing ventilation in nondependent lung (increasing comp)
Lithotomy or Trendelenburg Positioning:
-shift in abdomen limits diaphragmatic movement
Worse in obese individuals
May shift ETT right mainstem
What is the common component of all peripheral nerve injuries?
Ischemia (occlusion, emboli, edema)
What may augment development of ischemia?
Low MAP
What are the primary mechanisms for nerve injuries?
Transection, compression, and stretch
What are the patient related factors of PPNI?
Gender, Advanced age, extremes in body habitus
Lung capacities are typically _ in most positions
reduced
What preexisting conditions contribute to development of PPNI?
DM, hypertension, and tobacco use
What intraoperative occurrences contribute to PPNI risk?
Hypothermia, hypoxia, and electrolyte imbalances
Arm abduction should be limited to __ degrees while in a supine position
90
Arm abduction may tolerate more than 90 degrees while in what position
Prone
Stretching of hamstring muscle group beyond range may stretch what nerve resulting in limited hep flexion?
Sciatic Nerve
While in Trendelenburg, what increases the risk of periop neuropathies?
Shoulder braces
What should be assessed after surgery relating to this positioning lecture?
Extremity Nerve Function
In supine, trendelenburg, and lithotomy positions, what are some potential causes of brachial plexus injury?
Supine:
Arm abuducted >90 degrees on board
Arm falls off table edge
Arm abduction and lateral flexion of the head to the opposite side
Trendelenburg:
Shoulder braces placed too medial or lateral
Lateral: thorax pressure exertion on dependent shoulder and axilla
What are the positioning recommendations to protect the brachial plexus while in supine, trendelenburg, and lithotomy?
Do not abduct arm >90 degrees
Ensure arms are adequately secured
Support head in neutral alignment
To protect the brachial plexus, how should the shoulder brace be placed while in Trendelenburg?
Over the acromioclavicular joint, but avoid if possible.
To protect the brachial plexus, how should a roll be placed while in lateral position?
Place roll caudad to axilla supporting the upper part of the thorax
What is a frequent cause of ulnar nerve injury?
Arm pronated on arm board
What are the positioning recommendations to protect the ulnar nerve?
Supinate/neutral forearm on padded arm board
do not flex elbows more than 90 degrees
Pad elbows
Draw sheet should extended avoid elbow and be tucked between patient and mattress
Tucked arms in neutral position with palms facing inward
To protect the sciatic nerve, what are the positioning recommendations?
Minimal external rotation of legs
knees should be flexed
Recommendation to protect obturator nerve?
minimal hip flexion
What is the most frequently reported injury after surgery and anesthesia that is more frequently associated with males?
Ulnar neuropathy
What is ulnar neuropathy characterized by?
Inability to oppose/A the fifth finger and diminished sensation to fourth and fifth finger
Claw like contracture with atrophy
What is typically the site of injury for ulnar n injury? Why?
Cubital tunnel retinaculum(CTR)
-results from nerve compression/direct pressure on CTR from unpadded surface
T/F: Ulnar Neuropathy is from increased pressure with arm extension
False - flexion
When elbow is flexed, the distance between the olecranon and medial epicondyle increases, stretching the CTR, decreasing the size of the tunnel and can result in increased pressure on the nerve
In a supine position, why does abduction of the arms beyond 90 degrees put the brachial plexus at risk?
It stretches the plexus around the humeral head. Turning head to the side with arms abducted can cause stretching and compression of the contralateral brachial plexus beneath the clavicle
In a lateral position, the weight of the chest and compress the lower shoulder and axilla. Why is this an issue?
This puts pressure on the axillary neurovascular bundle aka brachial plexus
In a lateral decubitus position, what are the 4 reasons for brachial plexus injury?
arm abduction >90
external rotation
extension of lateral flexion of the head
posterior shoulder displacement
Shoulder braces placed too close to the base of the neck results in this injury (in reverse trendelenburg)
Compress structures resulting in brachial plexus neuropathy. Shoulder braces should be placed at distal end of clavicle over AC joint, but ARE BEST AVOIDED*
during cardiac surgery, what causes the first rib to rotate up pinching the plexus?
Sternal retractors
To prevent injury, caudal placement of the sternal retractor and avoidance of excessive prolonged asymmetric chest wall retraction are recommended
Mammary dissection requires this and may predispose to brachial plexus neuropathy
Wider asymmetric chest retraction
How can hyperflexion of the head on the neck be avoided in any position
Allow a minimum of 2 fingerbreadths between the sternum and mandible
Increased vertebral venous pressure can cause what type of injury?
spinal cord injury :((
Transcranial electric motor evoked potential is recommended for the detection of what 3 injuries?
Spinal cord, brachial plexus, and ulnar nerve injury due to positioning
What are the 5 main causes of Postoperative visual loss (POVL)
Ischemic optic neuropathy
central retinal artery occlusion
Central retinal vein occlusion
Cortical blindness
Glycine toxicity
What makes up 89% of prone injuries?
Ischemic optic nerve
What is the difference between anterior ION and posterior ION?
Anterior to lamina cribrosa
Posterior to lamina cribrosa
What is an anatomical cause of increased hypoperfusion of the optic nerves?
Supplied by central retinal and posterior ciliary arteries that are end arteries. This means that blood supply is from a “watershed region” indicating the region receives blood supply from the most distal branches of two arteries
Name the two factors that disrupt autoregulatory mechanisms and may contribute to ischemia of the optic nerve during hypotension
DM and hypertension
T/F: treatment for POVL can result in full recovery of vision and generally has a positive prognosis.
False! usually results in perminent visual loss and has a poor prognosis
What therapy has the highest chance of improvement in visual acuity when treatment is started within 6 hours of symptom onset?
Hyperbaric oxygen therapy
Name the 7 significant factors for POVL
Obesity
Sex
Wilson frame
Long operative times
Greater blood loss
Lower colloid:crystalloid ratio in the nonblood fluid loss
Colloid: albumin
Crystalloid: .9NS, LR, D5 ect
T/F: ION does not seem to be associated with pressure injury on the globe while CRAO does
True!
Define ocular perfusion pressure OPP
OPP = MAP - IOP
avoid increased IOP
avoid decreased OPP
T/F: venous pressure, IOP, and OPP all have a direct relationship
False, venous pressure and IOP have a direct relationship, but have an inverse relationship in OPP
Intraoperative events that decrease MAP and reduce OPP are (4)
GA
Hypotension
Hemorrhage
Hypovolemia
What is characterized by severe unilateral vision loss immediately following surgery?
CARO
What is the most common cause of CARO?
External pressure on the eyes due to improper head position
Because of this, CRAO is characterized by unilateral blindness
Emboli (hypercoagulation) migrating to CRA
What are the 3 perioperative risk factors for CRAO?
Prone spinal surgery
cardiopulmonary bypass surgery
Head/Neck procedures where injections are performed around nose and eyes
Name 6 strategies to reduce risk of CRAO
Avoid direct pressure on eye (head foam cut out is preferred)
Perform an document periodic eye checks when pt alert
Minimize venous pressure and congestion in the head
Minimize bleeding
Decrease duration of prone positioning (head in neutral position and at level or slightly above heart. 10 degree head up tilt)
Avoid significant hemodynamic changes
Name the potential position related injuries for EENT
Corneal Abrasion
Postop vision loss
Facial edema
Vocal cord edema
Name the potential position related injuries for cardiovascular
Vascular occlusion
deep vein thrombosis
Ischemic injuries
Name the potential position related injuries for respiratory
Atelectasis
Endobronchial intubation
Name the potential position related injuries for Neurologic
Peripheral neuropathy
Quadriplegia
Decreased cerebral blood flow
Increased intracranial pressure
Name the potential position related injuries for genitourinary
Myoglobinuria
acute renal failure
Name the potential position related injuries for MSK
amputation
back pain
compartment syndrome
Rhabdomyolysis
Name the potential position related injuries for Integumentary
Abrasion
Alopecia
Decubiti
What is compartment syndrome?
Reperfusion injury. Damage to neural and vascular structure d/t increased pressures and decreased tissue perfusion in muscle w/ tight boarders
Hypotension in conjunction with ____ results in compartment syndrome
Leg elevation
Compartment pressures increase over time in what position?
Lithotomy
Legs should be periodically lowered if surgery is longer than __-__ hours
2-3
What is the treatment for compartment syndrome?
Fasciotomy
Venous air embolism is a consequence of surgery being performed in what position?
Sitting position
If air emerges through the LV, disruption of BF to the heart and brain from micro air emboli can result in ___ or ___
MI or CVA
What can occur in the patient with a PFO (35% of population)
Paradoxical air embolism (PAE)
What is the gold standard to detect PFO in pts scheduled for surgery in the sitting position?
pre op TEE w/ contrast
What are the disadvantages of TEE?
expensive w/ potential for rare but serious complications.
Requires specialized training and time
Risk to pt and may not provide a continuous monitor of CV events
What is used to monitor for VAE when patients are in the sitting position?
Precordial Doppler.
** most sensitive noninvasive monitor**
Where should the precordial doppler be placed?
over the 3rd ICS to the 6th ICS to the right of the sternum
T/F: clinical sx occur later than changes detected by TEE, doppler, or capnography
True!
- Capnography: drop in ETCO2 (increased dead space) and the presence of ETN2
- Mill-wheel murmur via esophageal or precordial stethoscope
- Air in coronaries: ischemic electrocardiographic changes
- Air in pulmonary vessels: increase in PAP and hypoxia
What is the treatment for VAE?
Aspiration via CVC, but has little success
What are the main airway complications of surgical patients relating to positioning?
Vulnerable to ET tube displacement, airway edema, and passive regurgitation
What may occur from flexion of the neck or steep trendelenburg?
Right mainstem intubation
Extensive edema of face, tongue, oropharyngeal structures has been seen in prone, head down, and sitting positions. Why is this?
Prone: Increase in hydrostatic pressure restricts venous return from the head
Sitting position: excessive flexion of the head on the neck with patients may
obstruct jugular venous return resulting in macroglossia / airway edema
If an ET tube becomes kinked with extreme degrees of flexion, how can the CRNA keep the patient safe when preparing to extubate?
Verify an air leak around ET tube or visualize larynx via DL
What are the complications of Trendelenburg and reverse Trendelenburg?
Complications are mainly from positioning devices
- Too tight of table straps can result in lower
extremity neuropathies & pressure ulcers
- Foot board should be used instead of
overzealous tightening of the table strap
Shoulder braces: NOT be used with arm boards
- Too medially positioned: depression of bony
structure (compression of plexus)
- Too lateral: stretch injury of brachial plexus
Should be placed over acromioclavicular joint!
Avoid to prevent brachial plexus compression injuries
Axillary blocks are associated with the highest incidence of ____ ____ ____
Permanent nerve damage
Sneddon’s classification of nerve injury
-4 axonal reactions to nerve injury
-Transient Ischemic Nerve Block
-Neurapraxia
-Axonotmesis
-Neurotmesis
What occurs with neurotmesis nerve injury?
complete nerve disruption
-surg repair can only produce partial recovery
What occurs with Axonotmesis nerve injury
There is complete disruption of axon but sheath is intact
-recovery depends on regeneration of distal nerve at 1mm/day
What occurs with Neurapraxia nerve injury?
Demyelination of peripheral fibers of nerve trunk
-recovery is 4-6 wks
What occurs with a transient ischemic nerve block?
No structural damage
-recovery comes in minutes
Where should shoulder brace go?
-what happens if too medial?
-too lateral?
When using, place over Acromiomandibular joint
-medial: compresses brach plex between clavicle and rib
-lateral: stretches brach plex between clavicle and humeral head
T/F Ulnar nerve injuries will have symptoms immediately
false,
takes 48-72 hrs to see
Ulnar n injury deficits
-motor
-sensory
M: claw hand, inability to ABDuct/oppose pinky
S: impaired sensation digit 4-5 (medial 1.5 digits)
Brachial plexus can be injured in all positions except:
sitting
Median n injury deficits
-Motor
-Sensory
M: Ape hand, can’t oppose thumb and little finger
S: reduced in PALMAR surface of thumb, index, middle, lateral ring finger (lateral 3.5)
Radial n injury deficits
-motor
-sensory
M: Wrist drop, inability to extend hand at wrist, thumb weakness
S: decreased feeling in lateral 3.5 digits of DORSAL surface
Suprascapular n injury can cause dull pain in
shoulder
Obturator n injury deficits
-motor
-sensory
M: inability to ADduct leg
S: reduced sensation over MEDIAL aspect of thigh
Femoral n injury deficits
-motor
-sensory
M: knee extension and hip flexion
S: reduced feeling over the ANTERIOR aspect of thig hand ANTEROMEDIAL aspect of leg
Post Tib n injury deficits
-motor
-sensory
M: Foot drop; weakened toe extension
S: pain/numbness in plantar region
Sciatic n injury can occur at - and if pt is _
L4-L5
malnourished
Sciatic n injury deficits
-motor
-sensory
M: weakened areas below knee
S: reduced feeling over LATERAL half of lower legs and almost all of foot except arch
Saphenous n injury deficits
-motor
-sensory
M: no issue
S: reduced feeling over ANTEROMEDIAL aspect of leg
Most common lower extremity nerve injury
Common Peroneal n (branch of sciatic)
Common Peroneal n injury deficits
-motor
-sensory
M: Foot drop; inability to EVERT foot and extend toes dorsally
S: no issue
Pudendal n injury deficits
-motor
-sensory
M: …..sorry buddy
S: loss of penile sensation
4 main types of nerve injury
-compression
-traction
-stretch
-transection
-all 4 involve some level of ischemia
Ulnar n injury
-cause
-position
C: External compression; elbow flexion, forearm pronation
P: supine
Brachial plexus injury
-cause
-position
C: stretch (ext. hand rotation), compression (shoulder brace/ axillary roll), shoulder sag (posterior)
P: supine, trend, lateral, lith, prone (NOT SITTING)
Median n injury
-cause
-position
C: IV in AC, carpal tunnel, elbow hyperextension (after MR)
P: -
Radial n injury
-cause
-position
C: External compression (BP cuff, IV pole, tourniquet, sheets)
P: -
Suprascapular n injury
-causes
-position
C: stretch (shoulder circumduction)
P: lateral
Obturator n injury
-cause
-position
C: Flexion (thigh-groin), excessive traction, forceps delivery
P: lith
Femoral n injury
-causes
-position
C: Excessive traction, compression by retractors
P: lith
Sciatic n injury
-causes
-positions
C: Hip flexion, Ext. leg rotation, straight legs, compression (piriform_
P: lith, sitting, supine
Post. Tib n injury
-cause
-position
C: external compression (POSTERIOR aspect of knee from knee crutch stirrups)
P: lith, sitting, prone
Saphenous n injury
-cause
-position
C: external compression (MEDIAL leg from knee cructh)
P: lith
Common peroneal n injury
-cause
-position
C: lateral compression (stirrup and fibular neck), knees extended, legs externally rotated, pressure on dependent leg
P: lith, lateral
Pudendal n injury
-cause
-position
C: crush injury to genitals
P: orthopedic fracture table
Ulnar n injury is thought to occur from _ nerve compression or stretch caused by _ during the intraop period.
external
malpositioning
-ulnar n is superficial on proximal arm
-pt may not notice signs of injury for >48hr postop
Ulnar n injury could be likely due to it being susceptible to compression from the _ on the proximal _ process
tubercle
coronoid
3 factors possible contributing to ulnar n injury
-male (tubercle of coronoid process is 1.5x size of women, have less body fat for padding, and thicker cubital tunnel could compress n more easily)
-BMI >38
-prolonged best rest postop
Face mask injuries occur from which areas:
-outer 1/3 eyebrow hair loss (from straps)
-paresis of orbicularis oris muscle (from presure on buccal branch of facial n, will have issues opening/closing lips)
-necrosis on nose bridge (mask)
What could happen if you place fingers on the soft tissue instead of the ramus of the mandible when masking a pt?
laryngospasm
Axillary roll correct placement?
-slightly CAUDAL to axilla to prevent compression of brach plex
-dependent shoulder and upper arm are susceptible to compression in lateral position
5 main types of eye injury from positioning?
-Ischemic optic neuropathy (ION)
-Central retinal artery occlusion (CRAO)
-Central retinal vein occlusion
-cortical blindness
-glycine toxicity
Why is the optic nerve susceptible to hypoperfusion?
it’s in a “water shed” region, receives dual supply of 2 different arteries, if one is ischemic, optic n is at risk too
6 significant risk factors for ION:
-male
-obese
-Wilson Frame use
-longer case
-greater blood loss
-low colloid-crystalloid ratio in non-blood fluids
-other important ones: anemia from BL >1L , DM, HTN, smoking, vasc disease, intraop HoTN
ION
-prevention
Goal: avoiding increased IOP and avoiding decreased optic n perfusion
-avoid letting MAP drop (anesthetics, hypovolemia, ,etc)
-avoid increasing venous pressure (can impede aqueous humor outflow)
-avoiding positions that tilt head down, increase abd and RA pressure, or obstruct jug venous return (steep trend and wilson frame beds do this)
The orientation (anterior or posterior) of the ION depends on injury location in regards to which structure?
lamina cribrosa
Which is more common, ION or CRAO injury?
ION
CRAO injury is due to:
reduced perfusion to retina
Most common cause of CRAO:
poor positioning of head causing direct pressure on eyes
-other causes: emboli migrating (UL blindness)
CRAO
-risk factors
-prone spine positions
-CABG
-head/neck cases with injections around eyes/nose
Pt wakes up and immediately reports severe blindness in one eye postop. Which injury is the likely culprit?
CRAO
Central retinal VEIN occlusion
-risk factors
-HTN
-CV disease
-high BMI
-open angle glaucoma
-sickle cell anemia
-prone cases for head/neck (using a horseshoe headrest increases risk- use 3 pin rest instead)
When prone, pt’s head should be in _ position with head at (or a little above) level of _
neutral
heart
Risk reduction strategies for preventing POVL
-avoid pressure on eyes
-avoid horseshoe head rest
-check and document eyes periodically
-check vision when pt alert
-minimize venous pressure/congestion around head (avoid wilson frame if poss)
-minimize bleeding
-decrease duration of prone position
-avoid hemodynamic changes if poss (use colloid and crystalloid when giving fluids)
Which nerve injuries are more transient, sensory or motor?
sensory
-if persisting by postop day 5, get neurologist consult (if motor, get immediately)
When awake and in lateral position, the _ lung will have better FRC and when anesthetized, the _ lung will have better FRC
awake: dependent lung, better FRC
asleep: nondependent lung, better FRC
-this can cause a VQ mismatch, but hypoxic pulmonary vasoconstriction corrects this
Which positions increase total lung capacity?
Anesthetized lateral
Prone
Factors influencing BP intraop
-GA reduces CO and BP, CVP and SV reduced (myocard depression, vaso dilation)
-MR (reduce venous return, poor musc tone)
-Opioids decrease HR (further drop CO,BP)
-Large Vt and PEEP (increase intrathor pressure, causing less venous return, RA filling and CO)
T/F Pt is at greater risk of compartment syndrome when limbs are below heart
false, above!
Hemodynamic changes
-supine
-minimal if HOB is <45* ; preferred
Hemodynamic changes
-sitting
CO-reduced
VR-reduced
SV-reduced
CVP-reduced
PAP-reduced
SVR- increased
errthang reduced EXCEPT SVR
-opposite of trend
Hemodynamic changes
-lateral (awake)
minimal! preferred
-if kidney is elevated, vena cava could be compressed, then CO and VR would be reduced
Hemodynamic changes
-lateral (asleep)
minimal -preferred
–if kidney is elevated, vena cava could be compressed, then CO and VR would be reduced
Hemodynamic changes
-lithotomy
CO-reduced
VR- reduced
SV- increased
CVP-increased
PAP-increased
SVR- n/a
Hemodynamic changes
-trend
CO-increased
VR-increased
SV-increased
CVP-increased
PAP-increased
SVR-decreased
errthang increased EXCEPT SVR
-opposite of sitting
Hemodynamic changes
-Steep Trend
CO-reduced
VR-increased
SV-increased
CVP-increased
PAP-increased
SVR-decreased
errthang but CO and SVR increased
Hemodynamic changes
-prone
CO-reduced
VR-reduced
SV-reduced
CVP-increased
SV-decreased
SVR-increased
weight compressing heart so SV, CO, and VR wont be as much but everything else will be higher
Pts with normal heart function will have increased CO, SVR, and CVP in trend position but those with impaired function may have _ VR and _ CO due to increased workload
increased
reduced
Nerves at risk
-supine
-brach plex
-ulnar
-radial/circumflex (arm pressed against retractor)
Nerves at risk
-prone
-brach plexus
-ulnar
-tibial
-retina
Nerves at risk
-lateral
-brach plex
-axillary
-suprascapular
-common peroneal (dependent leg)
Nerves at risk
-lithotomy
ALOT
-brach plex
-sciatic
-common peroneal
-post tib
-saphenous
-obturator
most common LE n injury is common peroneal!
Nerves at risk
-trend
-brach plex (acromioclavicular joint)
Nerves at risk
-reverse trend
-LE neuropathies, pressure ulcers
Nerves at risk
-sitting
sciatic n
How many fingers between chin and sternum in sitting position?
2
When neck is flexed, what is ETT risk? What about extended?
Flex: deeper into R mainstem
Extend: possible extubation
Factors increasing risk of n injury
-positioning devices
-table strap
-leg holder/stirrups
-axillary roll
-bolster
-fracture table post
-shoulder brace
-head rests
-ether screen
Factors increasing risk of n injury
-length of case
> 4-5hr
Factors increasing risk of n injury
-body habitus
-obese
-malnourished
-bulky muscles
Factors increasing risk of n injury
-pre-exisiting patho
-anemia
-DM
-PVD
-liver disease
-periph neuropathy
-alcoholism
-limited joint mobility
-smoking
Factors increasing risk of n injury
-anesthetic techniques
-GA
-hypotension
-NM blockade
Local arterial pressure decreases by _ mmHg / cm change in height ABOVE the RA
0.75mmHg
