Week 11 - Positioning Flashcards
Problems arising from positioning such as peripheral neuropathies injuries fall under the doctrine “_____________” “the thing speaks for itself”
Res ispa loquitur
What does Res ispa loquitur imply?
This implies the injury sustained is so evident that it would not have occurred without negligence from someone else
- Patient only has to prove that there was an injury . . .
T/F: Positioning problems can result in significant injuries and successful
lawsuits.
True
The goal of the Anesthesia Closed Claims Project is to:
identify major safety concerns, patterns of injury and strategies for prevention to improve patient safety
by anesthesiologists working in pain management, operating rooms, labor floor, remote locations and critical care.
Tissue _______ and ________ are most commonly associated with positioning-related problems in anesthetized or sedated patients
Stretch and Compression
Stretch (especially ______ of normal resting length) can cause: (3)
> 5%
- Kinks or decreases lumens feeding arterioles and draining venules
- Direct Ischemia from reduced arteriole blood flow
- Indirect ischemia from venous congestion
Compression: (________ or ________)
neuropraxia ; axonotmesis
Compression: (neuropraxia or axonotmesis) can cause and result in:
- Direct pressure reduces local blood flow and disrupts cellular integrity
Results in:
- tissue edema,
- ischemia and
- possibly necrosis
T/F: Padding can create compression injury’
T
The MOA of positioning injury is not clear (T/F)
True :)
What can increase the risk of Positioning Injury (6)?
Perioperative inflammatory Responses:
- Inflammatory neuropathy
- Microvascular neuropathies
- Autoimmune disease/Viruses/immunosuppression
- Radiation-induced
- Systemic inflammation from drugs, or
- Transfusions of blood products.
I-SMART
Goals of Proper Positioning (7):
- clear view of the surgical site.
- Provides the best access to the surgical site
- best position for the optimal administration of drugs
- Can reduce bleeding before/during/after the surgery.
- Decreases the risk of pressure and nerve-related injuries
- Can prevent or reduce the risk of respiratory problems.
- Prevents/reduces risks associated with circulatory issues
Team Member Responsibilities
Surgeon:
Optimal procedural exposure
Team Member Responsibilities
Anesthesia:
- Physiologic requirements (ABC’s)
- Ongoingassessment
- Ensure patient safety
Team Member Responsibilities
Nursing:
- Safe transfer
- Use of adequate padding and positioning aids
- Ongoing assessment
A thorough assessment of risk factors for complications related to positioning should be an integral part of the :
preoperative evaluation
A history of which surgeries may need special positioning considerations:
- Knee
- Back
- Hip
- Neck
ask them how they feel comfy before putting to sleep
Positioning is a Shared Responsibility.
You MUST document every _______ _____, and how you protected the patient.
- position change.
is the biggest physiologic consequence of position changes
Hypotension
If _____, ______, or ________ moves you must recheck and document breath sounds.
head, neck, or whole body.
Patients are unconscious and relaxed and can often be placed in positions not normally tolerated (T/F)
True
Common Perioperative Neuropathies:
- Ulnar Neuropathies
- Brachial Plexopathies
- Median Neuropathies
- Radial Neuropathies
- Lower Extremity Neuropathies
Most COMMON perioperative neuropathy
Ulnar Neuropathy
- Key factors associated with ulnar neuropathy: (3)
- Direct extrinsic nerve compression (often medial aspect of elbow)
- Intrinsic nerve compression (associated with prolonged elbow flexion)
- Inflammation
Patients at risk of Ulnar Neuropathy (4):
- Male,
- high BMI,
- older,
- prolonged postop bed rest
Ulnar nerve passes behind ________ and under the_______ that holds the two muscle bodies of the ___________ together.
medial epicondyle;
aponeurosis
flexor carpi ulnaris
Elbow: Proximal edge of aponeurosis (______ ______ ______) is thick, especially in men
This structure stretches from the ____ to the ______.
cubital tunnel retinaculum
medial epicondyle to the olecranon.
Flexion of the elbow stretches the ________ and puts a lot of stress on the ______ nerve as it passes underneath
retinaculum
ulnar
T/F: Ulnar nerve is the only major peripheral nerve in the body that always passes on the flexor side of a joint…….. the elbow!
All other major peripheral nerves primarily pass on the extension side
False :(
Ulnar nerve is the only major peripheral nerve in the body that always passes on the extensor side of a joint…….. the elbow!
All other major peripheral nerves primarily pass on the flexion side
Peripheral nerves start to lose function and can develop ischemia when stretched:
> 5% of their resting length
________ degree elbow flexion stretches the ulnar nerve
> 90 (110)
Ulnar nerve injury can occur by:
a compression at nerve between the table and medial epicondyle
Ulnar nerve injury can be prevented by:
- supination,
- avoid hypotension and hypoperfusion.
- Pad arms properly
Ulnar nerve injury Manifested by:
- Inability to abduct the 5th finger.
- Weakness
- Atrophy of hand muscles “claw-hand”
- Numbness, tingling or pain in the lateral aspect of the hand on the side of the ulnar nerve injury
Other contributing factors for Ulnar Neuropathy (4)
- Patient characteristics
- Abnormal ulnar nerves before surgery (Contralateral neuropathy)
- Poorly formed fibrotendinous roof of the cubital tunnel
- External compression in the absence of stretch
Patient characteristics that contribute to ulnar neuropathy:
- prolonged bedrest
- high body mass index
Men:
- 1.5 times larger tubercle of the coronoid process
- less adipose tissue,
- thicker cubital tunnel retinaculum
(elderly also at risk of these).
Outcomes of Ulnar Neuropathy
- Sensory Only Neuropathy:
- Sensory and Motor Ulnar Neuropathy:
Sensory Only Neuropathy:
* 40% resolve within 5 days
* 80% resolve within 6 month.
Sensory and Motor Ulnar Neuropathy:
* 20% resolve within 6 months
* Many have permanent pain and dysfunction
Many patients don’t notice or complain until up to ______ hours later about nerve injury.
48
What to do about
Sensory-only neuropathy:
&
If both motor and sensory neuropathy:
- Observe patient as most resolve within 5 days
- If it persists for longer then a neurologist consult
- Consult a neurologist as soon as possible
Most common is patients undergoing sternotomy(especially those with internal mammary artery mobilization)
Brachial Plexus Injury
Two of these patients have a higher risk of Brachial Plexus Injury than the other one:
a. Patient in prone
b. Patient supine
c. patient lateral
A & C - Patients in prone and lateral have a higher risk than supine
- Things to think about with Brachial Plexus Injury:
- Brachial plexus
entrapment - Prone positioning
- Anatomy of shoulder abduction
In prone and lateral position patients what can happen to the brachial plexus:
Brachial plexus can become entrapped between compressed clavicles and rib cage
To prevent Brachial Plexus Entrapment it is better if a prone patient has: _______________.
Their arms tucked.
Some patients can have somatosensory-evoked potential changes when their arms are ________ (surrender position).
abducted
Shoulder braces may compress nerve roots and stretch the brachial plexus. (T/F)
True :)
Turning the head (unconscious patient) may stretch the:
Brachial plexus
What can a sternal retractor to do the nerves??
Spreading the sternal retractor causes the clavicle and rib to pinch the brachial plexus.
Unilateral retraction may cause stretching of the nerves.
Shoulder abduction:
Abduction _______ degrees places the distal plexus on the extensor side of the joint and the possibility of stretching the _________.
What is the goal?
> 90
Brachial plexus
Goal is to avoid abduction >90
What can cause Brachial plexus injury?
Excessive external rotation or abduction of the arm.
How to prevent a Brachial plexus injury?
- Avoid > 90 degree abduction
- Avoid arm falling off of table!
- Watch lateral head rotation
- If prone watch flexion and abduction of arms overhead
- Lateral position requires a chest roll
(inaccurately called an axillary roll) which avoids compression of humerus into axilla
Chest roll
Brachial plexus injury manifestations depend on which nerves are injured in the plexus (T/F)
True
Median nerve injury manifestations:
- “Ape hand” deformity, -
- inability to oppose thumb.
Axillary nerve injury manifestations
inability to abduct the arm
Ulnar nerve injury manifestations
“Claw hand” deformity
Musculocutaneous nerve injury manifestations
inability to flex forearm
Radial nerve injury manifestations
Wrist drop
Someone with scapular winging might have:
Long Thoracic Nerve Dysfunction
Long thoracic nerve palsy allows the dorsal protrusion of the scapula
Traumatic in nature
The serratus anterior muscle is supplied by the long thoracic nerve that branches immediately from _________, sometimes _____.
C5-C7; C8
Besides positioning; what else can cause Long Thoracic Nerve Dysfunction?
Virus or Inflammation
What can cause Axillary Neurovascular Injury:
- Abduction of the arm on the arm board > 90 degrees.
- Head of the humerus into the axillary neurovascular bundle.
- Compression and/or stretch injury.
- Compression or occlusion of vessels with decreased perfusion.
- Mastectomy (any breast surgery).
Muscular men with large biceps are susceptible to ______ nerve injury if the arm is fully ________ during surgery.
median;
extended
Median Neuropathies occur mostly in: (2)
- Mostly in men between 20 and 40 years old
- Men with large biceps and decreased flexibility
What are the consequences of a big JUICY bicep haha?
- Prevents complete extension at the elbow
- Creates a shortening of the median nerve over time
Median Neuropathies are usually what type of dysfunction?
and how long does it last?
motor dysfunction and don’t readily resolve.
Around 80% with motor dysfunction are still there 2 years after initial onset.
IVs in the antecubital fossa area can cause?
Median Neuropathies
Things to think about with Median Neuropathies
Stretch of the nerve: nerves become ischemia if stretched >5% of their resting length which can kink penetrating arterioles and exiting venules decreasing perfusion pressure
- When muscular men are anesthetized, their arms are fully extended at the elbow and placed on armboards
Full extension of the elbow stretches the chronically contracted median nerves and promotes ischemia (at the level of the elbow).
What should you do to prevent this ?
Support/pad the forearm and hand to prevent full extension.
Radial Neuropathies are more common than median neuropathies. (T/F)
T R U E
U>R>M
Radial nerve injury is usually compression of the nerve in the __________ area (arising from roots ________ and __________)
mid-humerus;
C6-8; T1
Some of the things that can cause Radial Neuropathies:
- Surgical retractors: compression of the radial nerve by bars used to hold abdominal retraction holders
- Lateral position (impinged by overhead arm boards)
- Unsupported arms/ poles/ repeated cycling of the BP cuff
The radial nerve can be injured if
compressed against spiral groove of humerus and other object (i.e. ether screen or excessive cycling of NIBP).
Radial Nerve Injury symptoms include:
- wrist drop,
- weakness of abduction of the thumb, and
- loss of sensation in web space between thumb and index finger.
DR CUMA
Drop = Radial nerve
Claw = Ulnar Nerve
Median Nerve = Ape hand
Lower Extremity Neuropathies include
- Common peroneal
- Sciatic nerve
- Obturator nerve
- Lateral femoral cutaneous nerve
- Femoral nerve
Great care must be exercised when placing the hip in unusual positions.
Excessive flexion or abduction can injure the ________ and _________ nerves respectively.
lateral femoral cutaneous or obturator
What can cause obturator neuropathy?
- Hip abduction >30 degrees can cause strain on the obturator nerve.
- Excessive hip flexion of the thigh can cause compression
- Excessive traction in abdominal Sx
Obturator passes through the _____ and out the _________.
pelvis;
obturator foremen
What types of dysfunctions do you see with Obturator Neuropathy?
Injury to which one is most common? (Sensory/motor)
Inability to adduct the leg with decreased sensation over the medial side of the thigh
Motor dysfunction is common
What can cause Lateral Femoral Cutaneous Nerve injury?
and how?
- Prolonged hip flexion >90 degrees can cause ischemia
- Hip flexion >90 degrees causes lateral displacement of the anterior superior iliac spine and stretch of the inguinal ligament.
- Nerve fibers are compressed by the stretch and can become ischemic and dysfunctional.
The Lateral Femoral Cutaneous Nerve injury can result in sensory and motor disabilities. (T/F)
False!!
This nerve carries only sensory fibers so no motor disability occurs.
Although the Lateral Femoral Cutaneous Nerve only has sensory fibers it can have disabling pain and dysesthesias of the medial thigh. (T/F)
F:
can have disabling pain and dysesthesias of the lateral thigh.
(*obturator nerve has effects on the medial thigh).
Lateral Femoral Cutaneous Nerve
One third of the nerve’s fibers pass through the __________ as it passes through the thigh (originates at ________)
inguinal ligament
L2-3
The sciatic nerve can be stretched by :
- external rotation of the leg.
Sciatic and its branches (common peroneal and tibial nerves) cross the hip and knee joints and are stretched by:
hyperflexion of the hips and extension of the knees
Peroneal Neuropathy is Usually associated with direct pressure of the _________, just below the ________, where the peroneal wraps around head of the _______.
lateral leg,
knee
fibula
Common Peroneal nerve can be injured by:
Injured by leg holders (candy cane) that hold the leg and foot
It can impinge the nerve around the head of the fibula
Peroneal neuropathy can cause:
prolonged foot drop and trouble ambulating.
Saphenous Nerve injury can occur :
- when the medial tibial condyle is compressed by leg supports.
- during difficult forceps delivery
- or by excessive flexion of the thigh to the groin.
Physiological changes related to change in body position
Most changes are related to gravitational effects on the cardiovascular and respiratory systems.
- Changes in position redistribute blood within the venous, arterial, and pulmonary vasculature
- Pulmonary mechanics also change with varying body positions
Changing from erect to supine does what?
Increases venous return and stroke volume
Parasympathetic stimulation regulate heart rate and contractility to adjust to increased preload
What three things can reduce venous return (preload) when in the supine procedure?
- Obesity
- Pregnancy
- Abdominal tumors
In the supine position, what happens to the lungs?
this is exaggerated in what patients and with which meds?
functional residual capacity and total lung capacity are reduced due to changes to the diaphragm.
This is exaggerated in obese patients
Anesthesia and muscle relaxants further reduce these volumes due to diaphragm position with relaxation
T/F: Trandelenburg position increases lung volumes.
False:
- it reduces lung volumes
Any position that limits movement of the diaphragm, chest wall or abdomen may increase _______ and ________.
atelectasis and intrapulmonary shunt
Four basic surgical positions:
Variations:
- Supine
- Prone
- Lithotomy
- ## Lateral
- Trendelenburg
- Reverse Trendelenburg
- Fowlers
- Jackknife
- High and low Lithotomy
A describe patient on supine position:
- Patient on back with pillow/donut under head
- Arms on arm boards or tucked
- Arms < 90
degrees - Arm is supinated (palm up)
- Place additional padding under elbow if able
- Check fingers
- Check IV lines and SaO2 probe
During the supine position, what are some of the pulmonary changes?
FRC is decreased by 20%
- Abdominal contents limit the movement of
the diaphragm
- Decreased muscle tone from GA
Small airways close sooner –> hypoxia
VQ changes cause shunting –> hypoxia
when in a supine position what can happen to the head?
Alopecia —> Pressure on occiput
- Prolonged compression of hair follicles produce
hair loss - Pain and swelling where the occiput has been supporting weight in the head-down position
- Associated with tight face mask straps, hypotension, and hypothermia
Pad back of the head. Check often in long cases
When is supine position how should the hips, knees, and legs be?
- Keep hips and knees slightly flexed
- Blanket/ pillow under knees.
- Legs uncrossed
- Heels, occiput, and elbows padded
In the supine position Cervical, thoracic, and lumbar spines should be in
straight alignment
Complications of Supine position:
- Peripheral neuropathies - can occur in any position.
- Backache.
- Ischemic pressure injuries.
- Pressure Alopecia.
- Pressure-Point issues:
– Hypothermia and vasoconstrictive hypotension.
– Heels, sacrum, and elbows.
When Arm Restraints are too tight, pressure can compress the:
the anterior interosseous nerve (branch of the median nerve) in the upper forearm.
Can resemble compartment syndrome in the lower extremity
watch out for patient armbands.
Nerve Injury that can occur from Supine Position (9)
- Brachial plexus neuropathy
- Sternal retraction
- Long Thoracic Nerve Injury
- Axillary trauma from the humeral head
- Radial nerve compression
- Median Nerve Dysfunction
- Ulnar Nerve Neuropathy
- Back pain
- Compartment syndrome
Steps to place someone in a lateral decubitus position?
- Positioned on the side often with the assistance of supports or bean bag.
- Arms parallel and padded.
- Maintain good anatomical alignment.
- Pillow between legs and feet
- Keep the bottom leg flexed to stabilize the trunk
- Chest roll placed
- Check radial pulse of dependent arm
During lateral decubitus positioning what nerve injury could happen from pulling?
Stretching of the Suprascapular Nerve
How is a chest roll placed? and what is it good for?
Support placed caudad to the downside axilla.
Lifts the thorax enough to relieve pressure on the axillary neurovascular bundle
Helps prevent decreases in blood flow to the hand and arm.
Decrease shoulder pain after postop
What type of nerve injury can occur in a lateral position?
Common Peroneal Injury
Steps for Flexed Lateral Decubitus
- Flexion should be under the iliac crest
- Chest roll
- Neck neutral
- Pillow between knees and flexed
- Padding under ankles/feet
- Flip the table so the flank and thorax are horizontal
What physical effects can occur when pt. is in flexed lateral position?
- Feet/legs below the atria causing pooling of blood.
- Lumbar stress.
When in flexed lateral position used?
not very common.
- Thoracotomy
- For kidney surgery: lateral jackknife with elevated kidney rest.
In a lateral decubitus position, VQ mismatching can occur.
Describe what happens to the
Dependent lung:
Nondependent lung:
Dependent lung:
* Underventilated
* More perfusion
Nondependent lung:
* Overventilated
* Less perfusion
** Causes increase VQ mismatching –> hypoxia**
describe Lithotomy position:
- Patient is supine with arms extended laterally <90 degrees
- Each lower extremity is flexed at the hip (about 90 degrees) and knees bent parallel to the floor
Extremities should be elevated and lowered slowly and together
When is lithotomy position most often used?
Seen most often in GYN and Urology cases.
In a lithotomy position hip flexion above >90 degrees can:
increase stretch of the inguinal ligaments
Lithotomy Stirrups
* Various types of stirrups:
- Candy cane
- Allen stirrups
- Knee cradles
Move legs at same time when positioning patient in and out of lithotomy
Tell me everything about-
Lithotomy Positions
Low:
- About 30-45 degrees
- Reduces perfusion gradients
Tell me everything about-
Lithotomy Positions
High:
- Suspend the patient’s feet high with stirrups
- Patient’s legs almost fully extended on the thighs flexed 90 degrees or more on the trunk
- Significant uphill gradient for arterial perfusion to the feet.
- Avoid hypotension
- Stretch of the sciatic nerve can occur
- Compression of the femoral canal by the inguinal ligament.
Tell me everything about-
Lithotomy Positions
Exaggerated Lithotomy is associated with:
- Pelvis flexed ventrally on the spine, thighs forcibly
flexed on trunk and lower legs aimed skyward
Associated with compartment syndrome
Lithotomy can auto-transfuse up to ______ of blood.
500 mL
Remember this will shift back when legs go down and can cause a decrease in BP
T/F the lithotomy position can impair ventilation due to downward pressure. More prominent in obese patients.
False!
The lithotomy position can impair ventilation due to upward pressure. More prominent in obese patients.
What injuries can occur in lithotomy position?
Nerve injuries:
- Sciatic,
- Common peroneal,
- Femoral,
- Saphenous and
- Obturator
And Hand injury.
Common peroneal nerve damage occurs from? what does it cause?
- Occurs from compression of the lateral aspect of the fibula head (improper padding against stirrups)
- FOOT DROP
- Elevate and flex simultaneously
- Avoids stretching of one side of the nerve*
> ____ hrs in lithotomy increases risk of injury * Ischemia, edema to skin and muscles
4 hours
Femoral Nerve injury can occur by:
- Excessive angulation of the thigh on the
abdomen - Excessive traction during abdominal Sx
When there is femoral nerve injury what problems can it cause?
- Decreased flexion of the hip.
- Decreased extension of the knee.
- Loss of sensation over the superior aspect of the thigh and medial or anteromedial side of the leg.
what is Compartment syndrome ?
- When perfusion to an extremity is inadequate
What is compartment syndrome characterized by?
Hypoxic edema.
Elevated tissue pressure within fascial compartments.
Extensive rhabdomyolysis.
Ischemia
Compartment syndrome is common in what positions?
- Lateral position(arm)
and lithotomy (legs)
Compartment syndromes is associated with
- Systemic hypotension and loss of driving pressure to the extremity (elevation).
- Vascular obstruction from excessive flexion, knee or pelvic retractors
- External compression from straps
- Lithotomy for > _____ hours common factor Compartment Syndrome
5 hours
Prone Position is used for what procedures?
- Posterior fossa of the skull,
- Posterior spine,
- Buttocks
- Perirectal
- Lower extremities (Achilles).
What things to look out for with a prone position?
Head neutral:
Head turned:
Arms:
Head neutral
* ET tube placement and patency
* Check bilateral eyes/ears for pressure points
Head turned
* Check dependent eye/ear ETT placement * Be aware of potential vascular occlusion
Arms at the side or “surrender position”
- < 90 degrees to prevent stretching of the brachial plexus
How can you provide adequate lung expansion and help alleviate pressure on
abdomen when the patient is prone?
By placing chest rolls from below clavicles to the iliac crest
When proning what are some things to keep in mind?
- Log roll pt. gently.
- Protect genitalia and breast
- ET positioning reconfirmed
- Pillow should be placed under lower legs and ankles –> helps flex knees and prevent pressure.
- Special pillow with a cut-out area
- Head positioned to the side may impair drainage on one side
- compression/stockings to minimize pooling of venous venous blood
Cardiovascular effects of prone position:
- Pooling of blood in extremities.
- Decreased preload, CO, BP, SV.
- Increased SVR and PVR
Pulmonary effects of prone position:
- Decreased total lung compliance.
- Increased work of breathing.
- ETT dislodgment
prone position effects on Eyes:
- Blindness from retinal ischemia.
- Corneal abrasions
- ION - ischemic optic neuropathy.
Eye effects on prone position:
- Blindness from retinal ischemia.
- Corneal abrasions
- ION - ischemic optic neuropathy.
For what procedure do you use reverse Trendelenburg?
- Cholecystectomy
- Head and neck procedures.
T/F: Reverse Trendelenburg shifts the abdominal contents cephalic.
False - Shifts the abdominal contents caudad
Cardio and pulmo effects of Reverse Trendelenburg
May have hypotension.
May result in decreased venous return and perfusion to the brain
Facilitates exposure, aids in breathing (increased FRC)
Pulmo effects of Trendelenburg:
- Further pressure upwards on the diaphragm from abdominal contents and further decreases lung expansion.
-Decrease in pulmonary compliance, FRC and vital capacity
- Increased risk of aspiration
- Mendelson syndrome: aspiration of > 25cc of gastric contents with a pH of < 2.5
Cardiac effects of Trendelenburg position:
Activation of baroreceptors:
- ^ Increase pressure
- ^ Increase baroreceptor discharge;
- Inhibits systemic vasoconstriction ( SNS ).
- Enhances vagal tone
- Further increases translocation of blood to central compartment (along with lithotomy).
Trandelenburg effects on the head and eyes:
- Increases ICP by decreasing venous drainage
- Increased IOP (pt with glaucoma)
careful with patient with eye/brain problems
- What should you think about before extubation of a pt. in trandelenburg position?
Facial and upper airway edema (Can the patient breathe around the ET tube with the cuff deflated)
What nerve injury can happen to a pt. trandelenberg with shoulder braces?
Brachial plexus injury
What is the most common injury to the eye?
What are some other
injuries to the eye?
Corneal abrasion
Chemical injury
Direct trauma (pressure and crush),
Blurred vision
How does the head position affect the position of the ET tube?
Flexion of the head may move the endotracheal tube toward the carina;
extension moves it away from the carina.
A general rule is that the tip of the endotracheal tube follows the direction of the tip of the patient’s nose.
Signs of mainstem bronchial intubation?
- Sudden increases in airway pressure
- sudden oxygen desaturation
Sitting (Beach Chair) used most often
- posterior fossa
- cervical spine
- shoulder
- neck surgeries.
Cardiovascular and pulmonary effects of the sitting (beach chair) position:
- Causes pooling of blood in the lower extremities (compression stockings).
- Decreased venous return.
- Decreased CO (20-40%)
____________ - Increased lung volumes
- Decreased work of breathing
Effects during awake sitting position:
- MAP, SV, CO, PaO2 all - decrease
- Alveolar-arterial oxygen gradient - Increase
- Pulmonary and Vascular resistance - increase
- An autonomic response helps compensate for the above by increasing SVR by up to 50-80%
- Cerebral perfusion pressure decreases by about 15%
Effects during general anesthesia of sitting position:
- The autonomic response is inhibited by general anesthesia causing vasodilation and decreased CO
- GA causes vasodilation, myocardial depression, and impaired venous return that further impairs cerebral blood flow
More Physiologic Changes in Beach Chair
What happens with flexion and extension of head?
- Flexion of the head may obstruct the internal jugular and cause cerebral venous engorgement or hypoperfusion (swelling in the face, eyes).
________________
- Extension of the head can impair cerebral blood flow causing cerebral ischemia, obstruction of ET and pressure on the tongue
Cerebral Perfusion Pressure (CPP) equation:
CPP = MAP–ICP (or CVP)
Cerebral vasculature dilates and constricts to maintain constant blood flow to the brain.
Cerebral Perfusion Pressure (CPP) equation:
CPP = MAP–ICP (or CVP)
Cerebral vasculature dilates and constricts to maintain constant blood flow to the brain.
Autoregulation occurs when MAP is between
_____________ mmHg
In poorly controlled HTN what happens to the curve?
50 and 150
Poorly controlled HTN the curve is shifted higher to the right
CPP and BP in Position
Supine:
Beach chair:
Supine: BP in the arm is similar to CPP in the absence of ICP
Beach chair: MAP and BP in the arm are higher than Cerebral perfusion.
If pt. is in a beach chair position… where would you put the a-line?
Monitored at the external auditory meatus (represents the base of the brain).
The external auditory meatus is about ______ cm above the heart ( _____ mmHg difference).
20 cm
15mmHg
1 mm Hg decrease/1.35 cm heigh
Big differences in BP and CPP can lead to :
blindness and stroke due to inaccurate BP
Potential complications from sitting position (6)
- Venous air embolism
- Hypotension
- Risk of airway obstruction
- Decreases venous return (stockings/compression)
- Macroglossia (avoid chin against the chest).
- Brainstem manipulations resulting in hemodynamic changes. (Neuro sx).
How can Midcervical tetraplegia occur?
- Hyperflexion of the neck, with or without rotation of the head.
- Stretching of the spinal cord resulting in compromise of the
vasculature of the mid-cervical region.
Midcervical Tetraplegia is:
Paralysis below the general level of the 5th cervical vertebra
In what position can Midcervical Tetraplegia occur?
- Sitting position (pulling of the arm in shoulder sx).
- Prolonged head flexion for intracranial surgery in the supine position
What causes venous air embolism?
- Caused by an open venous system above the level of the heart
- Atmospheric pressure > venous pressure and vein sucks air in
How to detect a venous air embolism?
Detection by listening to heart sounds with Doppler at Right 2nd intercostal space
Signs of venous air embolism:
Sudden decrease in CO2,
Hypoxia
Arrhythmias and Hypotension
Mill-wheel murmur (usually a late sign).
Venous Air Embolism Treatment
- Stop the problem
- Flood the area with water if necessary
- 100% O2 and Stop N2O
- Aspirate from CVP
- Durant’s position
- Vasopressors
- Get ready to do CPR
What can facemasks cause?
- Pressure damage over the nose.
- Facial nerve damage from fingers over the mandible.
- Face straps can cause injury or even necrosis to the face, ears, and eyes, and alopecia
Visual injuries can occur from:(10)
- Chemical irritation from preparation solutions
- Direct trauma from a face mask
- Pressure from the hands while intubating
- Pressure effects from the lateral and prone position
- Poor eye-taping techniques
- Large volume blood loss
- Prolonged hypotension
- Duration of surgery
- Prone or lateral position
- Edema
Patient’s at risk of visual injuries:
SHOE-AD
- Smokers
- HTN
- Obese
- ETOH abuse
| - Anemic
- DM
* Consent ALL Patient’s at Risk
Etiology of visual injuries?
- Etiology probably ischemic optic neuropathy
Corneal abrasions are the most common
* Blindness more rare
Potential Etiology of POVL (post-op vision loss)?
- Acute venous congestion of the optic canal
- decrease of optic nerve perfusion pressure
What can cause POVL:
Wilson Frame
- Head is lower than the heart
Obesity can increase intraabdominal pressure in prone patients
Long durations
”LOW”
Ways to help prevent POVL:
- Reduce venous congestion in the optic canal
- Keep head above the heart or at the same level
- Colloids vs Crystalloids
- Reduce intra-abdominal pressure
- Limiting the duration of surgery
T/F : * Anesthesia and muscle relaxants increase malposition injuries
True
what nerve is this
ulnar
what nerve is injured?
ulnar
what nerve is this
long thoracic nerve
what nerve injury is this
long thoracic nerve injury
what upper arm injury is this guy susceptible for
median nerve injury
what nerve
radial nerve
what nerve injury is this
radial nerve injury
what nerve injury
median
what nerve does this represent?
obturator
what nerve does this represent?
lateral femoral cutaneous nerve
what position
lateral decubitus
what nerve is stretched in this posiiton
suprascapular
what position is this
flexed lateral decubitus
what position is this?
lithotomy
what position is this?
reverse trendelenberg
what position is this?
steep trendelenberg
what procedure could this position be used for and what is it called
sitting position
brain or shoulder
