Positioning Overview Flashcards
What is the goal of positioning?
allow optimal surgical access while minimizing potential risk to the patient
What is the risk of positioning for surgery?
Risk: pt is unable to make necessary changes in positioning as needed
The preoperative interview should include specific questions that will determine the patient’s ability to _____________
tolerate the planned procedure
What is the components of patient’s interview?
- General level of awareness
- Age
- Weight and height
- Skin condition
- Nutritional status
- Current medications
- Normal range of motion and limitations on range of motion
- Physical abnormalities or limitations, such as back problems or deformities
- Preexisting medical conditions (e.g., vascular, respiratory, circulatory, or neurological problems, immune compromise)
- Previous surgeries and surgical complications
- Implants, such as total joint prostheses
Who determines the right position?
Positioning is a compromise between what an anesthetized patient can tolerate
- Structurally and physiologically vs. Surgical team access
Positioning-related complication often lead to ________
medicolegal scenarios
Why is position related to medicolegal?
Notations absent or uninformative
What is the documentation of patient positioning?
- Descriptive notation about position
- Note frequent checks as the body will shift during surgery, protective measures (eyes, pressure points, etc.), and complications in positioning
What is the cause of damage of neural tissue?
Hypoperfusion
What are the different types of neural tissue damage? (3)
stretch, compression, disruption
What can stretching of neural tissues cause?
peripheral & central neuropathies
When can tissue ischemia occur?
- > 5% than normal resting length = ISCHEMIA (reducing both arteriole & venule blood flow)
- Kinking of arterioles/venules associated w/ neural stretch = ISCHEMIA
What happens if ischemia is prolonged?
may result in permanent neural damage!
What can direcet compression of neural and soft tissue?
ischemia & tissue damage
What nerves are more susceptible to ischemia?
Peripheral nerves
Not always recognized ____________ after surgery and may manifest/be recognized weeks later
Immediately
What can happen to pressure points on soft tissue?
reduce local blood flow = ISCHEMIA
What is the prevention for damage to pressure points?
Padding (gels, foams, etc.)
What change in BP with change in height between the heart and body region?
MAP increases or decreases ~2mmHg/inch
When is MAP alterations a concern?
cerebral perfusion at the Circle of Willis
What positions are at risk for hypoperfusion and ischemia?
Head up, sitting and lithotomy
What happens to cardiac output in the full sitting position?
Cardiac output decreases 20% in full sitting position (90 degrees) secondary to venous pooling
Review the anatomy of the circle of willis.
What are the cardiovascular changes in the prone position?
- CVP increased
- BP and LV volume decreased
- Decreased venous return and increased intrathoracic pressure
- CI decreased or unchanged
- Increased venous pressure to the head
What are the cardiovascular changes in the lateral decubitus position?
- BP decreased if flexed
- Elevated kidney rest
- Legs dependent
- Venous return decreased by extreme flexion
- Vessel compression (vena cava)
What are the cardiovascular changes in the lithotomy position?
- BP appears normal or elevated
- Gravity dependent redistribution of blood (autotransfusion)
What are the cardiovascular changes in the sitting position?
- BP, CI, CVP and PCWP decrease
- SVR increases
What are the cardiovascular changes in the Trendelenburg position?
- Venous return (CVP), mean PAP, PCWP and MAP increased - problematic in CV disease
- Leads to vasodilation and decreased HR from stimulation of baroreceptor reflexes
- Increased venous pressure to the head
What are the respiratory changes in the prone position?
- Improved V/Q matching
- May depend on excursion of abdomen
- Improved FRC if abdomen excursion good
What are the respiratory changes in the lateral decubitus position for awake patient?
Ventilation favors dependent lung with awake, spontaneous ventilation
What are the respiratory changes in the lateral decubitus position for ventilated patient?
- With anesthesia, PEEP, paralysis, nondependent lung easier to ventilate
- Decreased ventilation and compliance in dependent lung
- Increased ventilation and compliance in nondependent lung
- V/Q mismatch can worsen: as perfusion directed to dependent lung- normally HPV compensates but inhibited by inhaled anesthetics
What are the respiratory changes in the Lithotomy position?
- Minimal resp effect in normal situations
- Extreme flexion and/or obesity
- Compliance and TV decreased
- Airway pressures and dead space / tidal volume ratios increased
What are the respiratory changes in the sitting position?
- Forced vital capacity and FRC normal
- Most favorable for ventilation
- If hips flexed may decrease FRC and closing volumes by shifting abdominal contents cephalad
What are the respiratory changes in the Trendelenburg position?
- Decreased FRC
- Potential for ETT to migrate right mainstem, especially if pneumoperitoneum achieved
What are the respiratory changes in the supine position?
FRC and total lung capacity decreased
What are the components of the brachial plexus?
- 5 roots (merge, split and converge)
- 3 trunks
- 6 divisions
- 3 cords
- 5 Terminal branches
What is true about positioning of the brachial plexus?
]The brachial plexus is vulnerable to injury in almost every position
Where is the brachial plexus?
is formed by the anterior primary rami of C5 through T1 and provides sensory and motor innervation of the upper extremity
What is the supraclavicular portion?
Roots, trunks, divisions - emerging through the posterior triangle of the neck between the anterior and middle scalene muscles
What is the infraclavicular?
Cords, terminal branches - lies within the axilla (cords named to their relation to the axillary artery)
What forms the trunks of the brachial plexus?
formed from anterior rami of C5—C8 and T1 (Roots)
Where do the trunks merge?
C5-C6 merge to form superior trunk, C5 to medial trunk, C8-T1 to inferior trunk
Where are the divisions?
Divisions converge under pectoralis minor to form cords (axilla)
What are the terminal branches?
Divisions become the terminal branches (immediately after the pectoralis minor)
- Ulnar n.
- Radial n.
- Median n.
- Axillary n.
- Musculocutaneous n.
Review brachial plexus.
Define Radial n.
(C5-8; T1) (upper and middle trunks; post divisions, cords)
Define musculocutaneous n.
(C5-7) (upper, middle trunks, ant. Divisions, lateral cord
Define median nerve.
(C6-T1) (all trunks, lateral and medial cords)
Define axillary n.
(C5-6): Motor to deltoid, teres minor, sensory to deltoid
Define ulnar nerve
(C8-T1) (Lower trunk, anterior divisions, medial cord)
Review distribution of the terminal nerves of the brachial plexus.
What are the two types of brachial plexus palsies?
- UBP injury-Erb’s Palsy
- LBP injury- Klumpke’s pLSY
Define ERB’s palsy.
Upper brachial plexus injury
- Increase in angle between neck & shoulder
- Traction (Strethcing or avulsion) of upper ventral rami (C5, C6)
Define Klumke’s Palsy.
- Excessive upward pull of limb
- Traction (Strethcing or avlusion) of lower ventral rami (C8, T1)
Review the classic sign of the Erb’s and klumpke palsy.
What is another perherial nerve that can be damaged?
- Ulnar nerve damage
Define ulnar nerve damage.
Results from damage to medial cord of brachial plexus
How does ulnar nerve damage occur?
Compression at the cubital tunnel (groove of medial epicondyle of humerus and olecranon)
What is the characteristics of ulnar nerve damage?
- Results in inability to oppose 5th finger and diminished sensation to 4th and 5th finger
- Clawlike contracture
Who is at high risk for ulnar nerve damage?
Male gender, presence of preexisting asymptomatic neuropathy, prolonged hospital stay, extremes of body habitus
What is the hallmark characteristics of ulnar nerve damage?
Claw hand
- Inability to extend fingers at interphalangeal joints, result in permananet flexion= claw
What is the hallmark characteristics of median nerve damage?
Ape hand
- inability to oppose thumb
What is the hallmark characteristics of radial nerve damage?
Wrist drop
- inability to extend the hand, inability to fully extend forearm
What effect can happen to the eye after surgery?
Postoperative visual loss
Where can vision loss occur?
May occur in one or both eyes
What are the components of vision loss?
Range of defects from loss of visual acuity to total blindness
Incidence of POVL is approximately ________ of all general anesthetics
1/60,000 to 1/125,000
What are the five primary causes of vision loss?
- Ischemic optic neuropathy (ION)*
- Central retinal artery occlusion (CRAO)*
- Central retinal vein occlusion
- Cortical blindness
- Glycine toxicity
What are the two primary causes of vision loss?
- Ischemic optic neuropathy (ION)*
- Central retinal artery occlusion (CRAO)*
Ischemic optic neuropathy (ION)* ______ of all cases of POVL
89%
What position does Ischemic optic neuropathy (ION)* occur?
Most common and associated with prone and adult patients (and CABG)
Where does Ischemic optic neuropathy (ION)* occur?
Ischemia in a portion of the optic nerve (suspectible to hypoperfusion)
What are the two types ofIschemic optic neuropathy (ION)*?
Two types based on position of the injury relative to the lamina cribrosa:
- Anterior ION (AION)
- Posterior ION (PION)
What are the risk factors Ischemic optic neuropathy (ION)*?
male, obese, Wilson frame, long operative time, increased blood loss and lower colloid to crystalloid ratio in nonblood fluid administration
What are the characteristics of Ischemic optic neuropathy (ION)*?
Sudden onset painless vision loss and a visual field defect
What is the prevention for Ischemic optic neuropathy (ION)*?
- Avoid decreasing MAP
- Avoid venous congestion leading to increased intraocular pressure
- Not having the head below the heart
What is the cause of CRAO (Central retinal artery occlusion)?
Caused by decreased blood supply to entire retina
What is the most common cause of CRAO (Central retinal artery occlusion)?
Most common cause related to incorrect positioning with external pressure on the eye (central retinal artery comes off internal carotid artery)
What are the risk factors of CRAO (Central retinal artery occlusion)?
Prone spine cases, CPB, head and neck procedures with injections around nose and eyes, hypertension, CVD, increased BMI, open angle glaucoma, sickle cell anemia, steep Trendelenburg position
How does CRAO (Central retinal artery occlusion) present?
Often presents as severe unilateral vision loss immediately following surgery
What Factors are Associated with Position Related Injuries?
- Positioning Devices
- Length of Procedure
- Body Habitus
- Pre-existing Pathophysiology
- Anesthetic Technique
What are components of positioning devices that can be caues of injuries?
–Table straps
–Leg holders and stirrups
–Axillary roll
–Bolsters
–Fracture table post
–Shoulder braces
–Positioning frames
–Headrests
–Ether screen
What are components of length of procedure that can be caues of injuries?
Longer than 4-5 hours
What are components of body habitus that can be caues of injuries?
–Obesity
–Malnutrition
–Bulky musculature
What are components of pre-existing pathophysiology that can be caues of injuries?
–Anemia
–Diabetes mellitus
–Peripheral vascular disease
–Liver disease
–Peripheral neuropathies
–Alcoholism
–Limited joint mobility
–Smoking
What are components of anesthetic technique that can be caues of injuries?
–General anesthesia
–Hypotensive techniques
–Neuromuscular blockade
What needs to be done to the operating room table?
Always inspect to ensure working properly and correct attachments (head rests, armboards, leg holders, etc.)
What should the SRNA/CRNA know about the operating table?
Know how to operate (lock properly, hand controls working, plugged in/has a plug)
What are other components of operating room table?
- Ensure correct bed (fluoro or xrays needed?)
- Have appropriate persons to help with positioning including surgeon
