Positioning Flashcards
Who is responsible for operative positioning?
the anesthesia provider
What is the purpose of operative positioning?
comfort
patient safety
surgical access
What should the CRNA document in regards to positioning for a case?
baseline ROM and function intraoperative positioning pads/cushions used body position frequency of checks
What are the height and weight limits for a standard OR table?
136 kg (~300lbs) 80.7 inches
What are the 5 most common operative positions?
supine prone sitting lithotomy lateral decubitus
What are the advantages of the supine position?
access to airway
access to arms for IVs
less physiologic changes than the other positions
What is the benefit of placing a pillow under the head in the supine position?
avoids extension or flexion of the head
places the head/neck in sniffing position
doughnut pillow reduces alopecia (especially in neonates or the elderly)
no pressure on the eyes
How should arms be positioned in the supine position?
tucked - palm in, elbow padded, tuck draw sheet under patient torso
arm boards - secured to OR table, abducted <90 degrees, padded, safety strap on, hands supinated
How should the feet be positioned in supine position?
heels shouldn’t hang over the bed
heels padded
How should the spine be positioned in the supine position?
slight flexion behind the hips and knees
pillows under the knees
legs should not be crossed
SCDs on
What are the 5 mechanisms of nerve injury?
compression kinking ischemia transection stretching
What are some modifiable factors that put you at risk for nerve injury?
obesity
smoking
diabetes
What is the most common upper peripheral nerve injury?
ulnar nerve
How can injuries occur to the brachial plexus?
mostly stretch injuries
- neck extension or head turned too much to the side
- excessive abduction of the arms >90 degrees
- arm/arm board falling off the table
What symptoms would show in a brachial plexus nerve injury?
electric shocks or a burning sensation down the arm
numbness
weak arm function
How does injury to the radial nerve occur?
compression of the radial nerve on the lateral aspect of the humerus against surgical retractors, ether screen, “step off”, repeated BP inflation
Injury to the radial nerve will result in..
inability to flex the elbow
wrist drop
weakness in abduction of the thumb
How does an injury to the ulnar nerve occur?
compression between the olecranon of the ulna and medial epicondyle of the humerus
stretching with severe elbow flexion
What are the consequences of ulnar nerve injury?
claw hand – inability to abduct or oppose 4th and 5th finger, weak grip on the ulnar side of hand
How can you reduce the risk of ulnar nerve injury?
pad arm boards
avoid overcompression by arm straps
place BP cuff proximal to the cubital fossa
avoid prolonged flexion of the elbow
What are the cardiovascular effects in the supine position?
initially increased venous return to the heart but there is a compensatory activation of baroreceptors that decreases HR and PVR
Under what circumstances might venous return be impeded in the supine position?
abdominal/thoracic masses, obesity, pregnancy, ascites
What ventilatory changes occur in the supine position?
FRC changes +/- 800 mL
may be compounded by muscle relaxants
can be overcome with PPV
What cerebral changes occur in the supine position?
minimal changes r/t autoregulation
What are the benefits of trendelenburg
may transiently treat hypotension
may improve surgical exposure
helps prevent air embolism
facilitates placement of central line insertion
Describe the placement of shoulder pads
should be padded and placed laterally… away from the neck and near the acromioclavicular joint
What are the cardiovascular changes associated with trendelenburg position?
reduces blood flow to the lower extremities
can cause compression of the heart
increases venous return to the heart
What ventilatory changes are associated with trendelenburg position?
displacement of abdominal contents will cause decreased lung compliance, PIP increases, decreased lung volumes, V:Q mismatch, ETT displaced to the R main bronchus, risk of aspiration, airway edema
What are the cerebral changes associated with trendelenburg position?
increased ICP and increased IOP r/t vascular congestion
What must be considered when using a foot board with reverse trendelenburg position?
prolonged plantar flexion can cause anterior tibial nerve injury resulting in foot drop
What cardiac changes are associated with reverse trendelenburg position?
reduced preload, reduced CO, lower BPs, RAA activation, venous pooling in the legs
compensatory reflexes to increase SVR and HR are often blunted by anesthetics
What ventilatory changes are associated with reverse trendelenburg?
ventilation becomes easier, FRC increases
What cerebral changes occur with reverse trendelenburg?
ICP decreases, cerebral blood flow decreases up to 20%
If the patient is in reverse trendelenburg, where should you place your A-line BP transducer?
as close to the Circle of Willis as possible
What nerve injuries are associated with the lithotomy position?
femoral – r/t hip flexion
sciatic – r/t overstretching
common peroneal or saphenous – r/t calf compression
Describe positioning for lithotomy
Hips flexed 80-100 degrees
Legs abducted 30-45 degrees from the midline
Lower legs parallel to the torso
What nerves are especially at risk during the lithotomy position, particularly if you are using candy cane stirrups?
common peroneal nerve – the outside of the leg may compress against the metal bars
What is the most common LE nerve injury?
common peroneal nerve
What risk factors place you at increased chance of having a peripheral nerve injury r/t positioning?
obesity, smoking, diabetes, PVD, low BMI, prolonged surgery
What are the symptoms of a common peroneal nerve injury?
foot drop, inability to evert the foot, loss of dorsal extension of the toes
How does sciatic nerve injury occur and what are the symptoms?
excessive external rotation of the hips or pressure in the sciatic notch from overstretching
symptoms: weakness or paralysis of muscles below the knee, footdrop, numbness in foot or lower leg
How does femoral nerve injury occur and what are the symptoms?
compression at the pelvic brim by the retractor or excessive rotation or flexion of the hip
symptoms: inability to flex the hip and extend the knee, decreased sensation over the top of the thigh
How can saphenous nerve injury occur and what are the symptoms?
medial aspect of lower leg compresses against the support bar
symptoms: parasthesias to the medial aspect of the lower leg
Discuss compartment syndrome
occurs when perfusion to the extremity is inadequate, resulting in ischemia and edema with extensive rhabdomyelosis
occurs with longer surgical procedures
more common in lithotomy and lateral decubitus positions
What cardiovascular changes are associated with lithotomy position?
increases venous return to the heart and preload to the heart, causing transient increases in CO and BP
reduced perfusion to the lower extremities (2mm per 2.5 cm above the heart)
What ventilatory changes are associated with the lithotomy position?
abdominal contents may push up and compress lung bases, reducing compliance, Vt and vital capacity.
increased risk of aspiration
How can you combat ventilatory changes associated with lithotomy or trendelenburg position?
PPV
What are the disadvantages of the prone position?
less access to the airway, torsion of the spinal column, hard to get the patient in a natural position
What are important considerations for head rests?
watch the eyes and nose for pressure points, maintain neck alignment
What are the most common eye injuries in the prone position?
corneal abrasions – direct eye trauma, swelling
treatment with antiobiotics, eye patch
What are the most common causes of ischemic optic neuropathy?
edema
hypoperfusion
high IOP
What are the risk factors for ischemic optic neuropathy?
HTN, obesity, smoking, diabetes, operative hypotension, large blood loss, prone position in the OR, anemia, large crystalloid use, male
How should the arms be arranged in the prone position?
on arm boards by the head, abducted less than 90 degrees, extra padding around the elbow, shoulders not sagging
*may also be tucked at the sides
What is thoracic outlet syndrome? How can it be prevented?
when in the prone position and the arms are elevated above the head, the clavicle moves forward and can occlude blood flow and lymphatic drainage
Prevention: check beforehand for problems by having patient place arms folded behind their head for 2 minutes and then check pulses and ask about neuropathies
Cardiovascular changes associated with the prone position?
hypotension
venous pooling in the extremities
decreased preload
What ventilatory changes are associated with the prone position?
V:Q mismatch (anterior better perfused, posterior better ventilated)
decreased lung compliance
increased WOB
overcome this by using rolls and PPV
Cerebral changes associated with the prone position
may cause high ICP
may obstruct cerebral blood flow if the head is turned excessively
What types of surgery would you put a patient in the lateral position for?
thoracic, kidney, shoulder, hip surgeries
What special positioning is required in the lateral position?
- axillary roll to support the chest and axilla
- limit pressure on eyes and ears
- avoid misalignment of the C-spine by keeping the head in a neutral position
- avoid stretching of the brachial plexus
How should arms be positioned in the lateral position?
dependent arm on padded arm board and perpendicular to the torso
non-dependent arm supported with pillow or suspended by arm rest
How should the legs be positioned in the lateral position?
padding between the knees and flex the dependent leg to prevent saphenous nerve injury
padding on the bed for the lower leg to prevent common peroneal injury
What are the cardiovascular changes associated with the lateral position?
minimal…
no change in CO unless the kidney rest compresses venous return
noninvasive BP cuff measurements will be different in the two arms
ventilatory changes associated with the lateral position
V:Q mismatch
- awake & breathing – dependent lung better ventilated and perfused
- anesthetized but breathing – nondependent lung is ventilated and dependent is perfused
- anesthetized and ventilated – nondependent lung is overventilated and dependent lung is overperfused ((worst mismatch))
For what type of surgeries would you put the patient in a sitting position? Why?
cranial surgery, shoulder surgery, humeral surgery
facilitates drainage
excellent surgical exposure
What are some special considerations when placing the patient in a sitting position?
maintain 2 FB between mandible and sternum to avoid excessive cervical flexion
avoid a bite block to prevent tongue ischemia
head will be fixed in pins
How should you set the patient up in a sitting position?
arms supported and not hanging
buttocks in the break of the table
foot board padded
slightly flex knees and hips
cardiovascular changes associated with the sitting position?
hypotension
blood pooling in lower extremities causing decreased preload and CO
HR and SVR may increase as compensation (blunted by anesthetics)
What ventilatory changes are associated with the sitting position?
increased lung volumes, increased lung compliance, easier WOB
cerebral changes associated with the sitting position?
ICP and cerebral blood flow decreased
What are symptoms of VAE (venous air embolism?
wind mill heart murmur on doppler dysrhythmias hypotension desaturation decreased EtCO2 circulatory compromise cardiac arrest
When does VAE become a risk?
when surgery is performed anywhere above the heart
What is the immediate response and treatment to VAE?
flood surgical field with NS or place wax over exposed bones
close any open vessels
D/C nitrous (it will expand in air spaces)
place patient on 100% O2 and add PEEP
trendelenburg position
aspirate air from RA with a catheter
For what kind of surgeries would you place the patient in a supine position?
abdomen, chest, head, neck, extremities
For what type of surgeries would you place the patient in a reverse trendelenburg position?
laproscopic procedures
For what type of surgeries would you place the patient in lithotomy position?
gynecological, rectal, perineal procedures
For what type of surgeries would you place the patient in the prone position?
spinal, rectal, some orthopedic procedures
What are the risk factors for compartment syndrome?
systemic hypotension, vascular obstruction of a major extremity vessel by retractors or extreme flexion, external pressure by a poorly padded area or straps, lithotomy position, trendelenburg position, advanced age, patient hx of nerve ischemia or neuropathy , anemia, prolonged surgical time, vasoconstrictive drugs
