Flashcards in Positioning Deck (72):
How should patients be moved during surgery?
Slow position changes, especially at the en of along case
Length of the OR table
What can happen with irregular head positioning?
Brachial plexus injury, excess swelling,
Where is the drawsheet placed when tucking the patient's arms?
Under the pt's hip or torso. NOT under the mattress.
How long is the anesthesia bed?
How is lumbar support obtained in the supine position?
Slight flexion of the hips and knees by placing a pillow under the knees (be careful that it isn't too hard or too high or could cause problems with venous return). With bend of the legs, should have SCD and TEDs to improve venous return and decrease risk of DVT
What are the mechanisms of nerve injury?
Stretching, compression, kinking, ischemia, transection
How can brachial plexus injury occur in the supine position?
Neck extension or turned to one side, arm abduction > 90 degrees, arm/arm board falls off the table.
Sternal retraction during cardiac surgery is also associated with plexus injury.
- Overall these are mostly due to stretching
S/S of brachial plexus injury
Damage can be specific or general to the entire arm
- Electrical shock / burning sensation shooting down arm
- Arm numbness or weakness
- Absent or weak motor control of shoulder and elbow
How does injury to the radial nerve occur in the supine position?
External compression of the radial nerve against the lateral aspect of the humerus from:
- Surgical retractors
- Ether (anesthesia) screen
- Mismatched arm board
- Repeated BP cuff inflation
Injury to the radial nerve causes
Wrist drop, weakness in abducting the thumb, and numbness of the posterior thumb, and first 2 fingers
This is the most common nerve injury in the supine position
Ulnar nerve injury is more common in (males/females)
How does ulnar nerve injury occur?
Stretch and compression
Compression of the nerve in the cubital groove between the olecranon of the ulna and the median epichondyle of the humerus.
Stretch from severe elbow flexion, dislocation with pronation of the hand, nerve dislocation over the median epichondyle with stretching/compression against the bed.
Symptoms of Ulnar Nerve Injury
Inability to abduct or oppose the 5th finger. Weak grip on the ulnar side of fist.
Loss of sensation of 4th and 5th fingers
Atrophy of intrinsic hand muscles
How to reduce the risk of ulnar nerve injury
Pad the arm boards
Supinate the arms
Make sure that surgical staff aren't compressing the patient's arm
Avoid downward compression from strap
Place the BP cuff proximally so that it doesn't compress on the ulnar groove/cubital tunnel
Avoid prolonged FLEXION of the elbow!**
CV effects of the supine position
MINIMAL effects on circulation and perfusion
Initial increase in venous return (causes increase in preload, SV, CO, BP, and baroreceptor-initiated decrease in HR and PVR)
These measures will increase venous return to the heart
SCDs, TEDs, uncrossing the legs, padding the heels, pillow under the knees, knee/hip flexion
Effect of IVC compression
The IVC can become compressed by a large abdomen (pregnancy, obesity, ascites, masses, etc), decreasing venous return, preload, and CO.
Effect of the supine position on vent status
Slight upward displacement of diaphragm/compression of lung bases causes a decrease in FRC by 800mL
Exacerbated by muscle relaxants (because this causes the loss of chest wall recoil that normally opposes the want of the lungs to collapse)- this is overcome with PPV
Effect of the supine position on CBF
Benefits of trendelenberg
Tx of hypotension by increasing venous return
Decreasing risk of air embolism
Facilitates cannulation during central line placement
Improves surgical exposure for abdominal / laparoscopic surgery
Shoulder braces should be placed here
Over the acromioclavicular joint. This avoids pressure on the clavicle, which would compress the brachial plexus
What should you do if your patient starts sliding in trendelenberg?
You can extend the bed, and also make sure nothing is pulling from their movement.
Slide the patient back.
Place in reverse T if at an appropriate place in surgery
VCV effect of trendelenberg
1) Increase in venous return (as much as 1L extra into central circulation) and reversal of hypotension (use for hypotension is controversial- short term only!!). Remember that this increase in CO will also put more demand on the heart.
2) Activation of baroreceptors- decrease in SVR (vasodilation) and HR---this effect can make shock worse in the long run. Short term use only!
3) Decreased blood flow to the lower extremities
4) Compression of heart by abdominal contents
Effect of the trendelenberg position on ventilation
1) Abd contents move cephalad, impeding diaphagmatic excursion, compressing lung bases, decreasing FRC, and increasing PIP.
2) V:Q mismatch because perfusion of lung apex exceeds ventilation of lung apex
3) Aspiration risk
4) Face and airway edema, which can lead to airway obstruction
5) ETT shift into R mainstem
6) Pulmonary edema and congestion
These may be indicators of airway edema
Lip and periorbital edema
Effect of the trendelenberg position on the head
Increase in intracranial vascular congestion leading to increased ICP!
IOP rises as well.
Patients with IICP and severe glaucoma are not good candidates for this position
Surgical use of reverse T
Enhance exposure of the upper abdomen by shifting abdominal contents caudad (laparoscopic cholecystectomy)
Variations on reverse T may be used for shoulder, neck, breast, or intracranial surgery
Reverse T and nerve injury
Excessive plantar flexion of the feet for extended periods of time causes anterior tibial nerve injury and foot drop
- To avoid, periodically flatten the bed and reposition to avoid foot injury
CV effects of reverse T
1) Reduced preload, reduced SV, reduced CO (20-40%) and decreased BP
2) Activation of the RAAS (kidneys notice the fall in CO)
3) Venous pooling (TEDs and SCDs)
Effect of the reverse T on ventilation
Increase in FRC because abdominal contents are out of the way. Ventilation is reasier.
Effect of the reverse T on CBF
CBF decreases proportional to the degree of head elevation (up to 20%)
Decrease in ICP
Placement of the patient in the lithotomy position
Bend knees, separate, and lift simultaneously (to avoid torsion of the lumbar spine)
Hips flexed 80-100 degrees
Legs abducted 30-45 degrees from midline
Lower legs should be parallel to the torso
Types of leg support in lithotomy and their associated risks for nerve injury
1) Calf-support stirrups (femoral, sciatic, lower leg nerves)
2) Candy cane stirrups (common peroneal, sciatic, and femoral)
3) Knee crutch style (popliteal nerve, femoral, and sciatic)
Overall, lithotomy position can be associated with these nerve injuries
Femoral, sciatic, common peroneal, saphenous, obturator, LFC.
Frequency of nerve injury with lithotomy position
78% common peroneal
Increased risk of nerve injury in lithotomy position is associated with
low BMI, prolonged surgery, recent cigarette smoking
Symptoms of common peroneal nerve damage
Foot drop, inability to evert the foot, inability to dorsiflex the toes
Sciatic nerve injury can be caused by
Excessive external rotation of the hips
Pressure in the sciatic notch from stretching
Symptoms of sciatic nerve damage
Weakness/paralysis of muscles below the knee
Numbness of the foot and lateral half of calf
Femoral nerve can be injured by
Excessive angulation/abduction of the thigh and external rotation of the hips
Damage to femoral nerve causes
Inability to flex the hip and extend the knee. Loss of sensation over the anterior and superior aspects of the thigh
Risk of compartment syndrome
Procedures over 2-3 hours in length and in the lithotomy or lateral decub positions
Effect of lithotomy on lower extremity perfusion
Perfusion pressure decreases by 2mmHg for each 2.5cm increase in vertical height
Lithotomy is often combined with this position
Effect of lithotomy on CBF
Transient increase in cerebral venous blood flow and ICP
Frames used for the prone position
1) Wilson Frame
2) Jackson Table
How to move patient into prone position
- Line placement
- NGT/OGT, esophageal steth, bite block, foley
- Eye protection!!
- Secure the shit out of everything!!
- When about to move, disconnect most of the monitors except pulse ox
Flip to table:
- Anesthesia has head/neck/ETT
Once on Table
- FIRST CHECK BREATH SOUNDS (this is our chance to put them back on the stretcher if they have to be re-intubated
- Reconnect everything
- Make sure all the lines still work
- Properly position the patient and make sure
What should you do with boobs in the prone position?
Place them in a neutral position or pushed medially. Don't push those babies laterally.
This places a patient at high risk for ischemic optic neuropathy
Prone position, hypotension, large blood loss, large crystalloid use, anemia, smoking, diabetes, vascular pathology, HTN, males, cardiac surgery, spinal surgery
Cause of ischemic optic neuropathy
From compression of central vein or artery due to sustained, direct pressure on the eye/retina during surgery. Can cause visual changes or partial or complete blindness.
Treatment for corneal abrasions
Antibiotic ointment and eye patch
If a patient has thoracic outlet syndrome, how should the arms be placed in prone position?
Along the sides. We want to avoid tension of the musculature around the shoulders
CV changes with prone
Pooling in lower extremities, decreased preload, decrease in CO and BP.
Counteract this with TEDs/SCDs
What MUST be anticipated with the move to the prone position??
Be ready to treat. Remember too that prolonged hypotension in the prone position can cause blindness!
Effect of prone on ventilation
Cephalad displacement of diaphragm. Decreased lung compliance. Increase in PIP. Increased WOB.
PPV overcomes these effects.
How to improve lung function in the prone position
Rolls/bolsters to free chest excursion.
Effect of prone on CBF
Turning of the head obstructs venous drainage, leading to IICP
Excess flexion/turning can obstruct vertebral artery flow
Lateral decub is used for
Thoracotomy, kidney, shoulder, and hip surgery
In lateral decub, we place a pillow between the legs to prevent injury to this nerve
Where should the safety strap in lateral decub be placed?
Between the head of the femur and the iliac crest
CV changes with lateral decub
Minimal as long as venous return isn't obstructed
BP measurements will be different in the two arms
Ventilation changes with lateral decub
Awake and spontaneously breathing
- Dependent lung is better perfused and ventilated
Anesthetized but spontaneously breathing
- Nondependent is better ventilated and dependent is better perfused (V:Q mismatch)
Anesthetized and vented
- Non-dependend lung is overventilated and the dependent lung is overperfused (even worse V:Q mismatch)
Sitting position is used for
Crianial, shoulder, and humeral surgery
Facilitates venous drainage as well
Excessive cervical flexion can cause
obstruction of venous outflow causing hypoperfusion and venous congestion, stretching of cervical nerve roots, ETT obstruction (kinking), can cause pressure on tongue (swelling)
We want this amount of space between the mandible and sternum
CV effects of sitting position
Venous pooling, decreased return, decreased preload, CO, and BP
Hypotension!! - Raise the head SLOWLY
Compensatory increase in HR and SVR (but these are blunted by anesthetics)
Treat with: IVF, pressors, adjusting anesthetic depth, TEDs and SCDs
When is venous air embolism (VAE) a risk
ANY TIME the surgical site is above the heart!!
This is a potentially LETHAL complication!!
Signs of VAE
Change in heart tones (wind mill murmur) heard via doppler at the parasternal border at 2nd-6th IC space.
Detection with TEE or precordial doppler ultrasound
Does VAE cause an increased or decreased EtCO2?