Lecture 2: Positioning Flashcards
1
Q
Name 3 purposes of operative positioning.
A
- Comfort
- Patient safety
- Surgical Exposure/Access
2
Q
What types of information should be documented regarding positioning?
A
- Baseline range of motion
- the intra-op position
- Use of padding
- Frame
- Body position
- Checks done and frequency
3
Q
Newer OR tables have what weight limit?
A
270kg or 600lbs
4
Q
Which position is the most common? Why do we like it?
A
Supine. Because we have access to the airway, hands and feet a lot more this way. Less physiologic changes than in other positions
5
Q
A pillow is placed under the head in supine position for what two main reasons.
A
Allow for proper sniffing position
Avoids dorsal extension and lateral flexion of neck.
6
Q
What is the process to tucking a patient’s arms?
A
Draw sheet is under the patients hip or torso (not the mattress) elbow is padded and the palms are into the side of the leg.
7
Q
Name an advantage and a disadvantage to tucking arms in?
A
Surgeon can stand really close. We lose access to them (if we need to start another IV, or if something becomes disconnected we can’t see them)
8
Q
How far is it appropriate to abduct arms secured to armboards? What happens if we go too far? What could happen if the straps were too tight? What could happen if the arms were pronated on accident?
A
Under 90 degrees. Brachial Plexus injuries. Compression. Ulnar nerve entrapment.
9
Q
Hands should be?
A
SUPINATED
10
Q
In the supine position we don’t want anything too hard or too high under the knees because?
A
We don’t want to obstruct venous blood flow.
11
Q
It is/is not acceptable for heels to lay over the bed?
A
Is not
12
Q
Name the 5 mechanisms for nerve injuries.
A
- Stretching
- Compression
- Kinking
- Ischemia
- Transection
13
Q
Microvascular _______ is probably a cause in every nerve injury.
A
Ischemia
14
Q
Name some factors that contribute to nerve injuries.
A
How we position them, prolonged surgery, technique we use, GA because the patient can’t move themselves, having preexisting diseases like DM, CVD and obesity
15
Q
What are the two fixed points through which the brachial plexus courses?
A
Vertebral foramina fascia and the axilla.
16
Q
When does brachial plexus injury occur? What normally causes it?
A
Neck extension Head turned to the side Arm board extended/abducted more than 90 degrees Arm/armboard falls off the table. Retractors Humerous pressed into chect Stretching.
17
Q
Name four things that could cause a radial nerve compression injury.
A
- Surgical retractors
- Ether screen
- Mismatched arm board (it has a step off that digs into the back of the arm)
- Repeated BP inflation
18
Q
What kinds of manifestations would a patient with a radial nerve injury present with?
A
wrist drop
weakness in abduction of the thumb
numbess 1, 2 and right fingers
19
Q
How can we injure the ulnar nerve?
A
in cubital tunnel at the elbow groove compression of the nerve between the olecranon of ulna and the medial epicondyle of humerus (entrapment with arm extension). Also by stretch with severe elbow flexion, dislocation with pronation hand, nerve dislocation over medial epicondyle with stretching, compression against the bed.
20
Q
What patient population is more likely to suffer a ulnar nerve injury?
A
Muscular men.
21
Q
Describe the claw hand.
A
Inability to abduct or oppose 5th finger.
Weak grip ulnar side of fist.
Loss of sensation palmar surface 4th and 5th fingers.
Atrophy of intrinsic muscles of the hand.
22
Q
How do we reduce the risk of ulnar nerve injury? (6)
A
- Pad arm boards
- Avoid downward compression by strap.
- Assure surgical personnel do not compress patient’s arm
- Place BP cuff proximally so that it does not impose on ulnar groove or cubital tunnel
- Avoid prolonged flexion of the elbow
- Avoid excessive abduction/extension.
23
Q
Supine position has what kind of effects on circulation and perfusion?
A
Minimal
24
Q
Name four ways to improve venous return from the lower extremities.
A
- Uncross legs
- Pad heels
- Pillow beneath knees
- Flexed hips and knees.
25
What can cause IVC compression in the supine position?
masses, pregnancy, obese abdomen and ascities.
26
Upward displacement of the diaphragm and compression of the lung bases in the supine position cause what kind of a change in FRC? What further reduces lung volumes?
+ or - 800ml.
| Muscle relaxants
27
Muscle relaxants do what to chest wall muscle? What does this due to elastic recoil? How do we overcome this?
We lose chest wall muscle
Reduces opposition to inherent elastic recoil
Overcome with positive pressure ventilation.
28
Do we see a change in cerebral blood flow in the supine position?
Minimal due to tight autoregulation
29
What do we use trendelenberg for? What does it improve, help with and facilitate?
Used to treat hypotension by increasing venous return
Improves surgical exposure during abdominal and laparoscopic surgery (takes abdominal contents out of the pelvis)
Helps prevent air embolism
Facilitates cannulation during CL placement
30
Tell me about the cardiovascular changes in T-berg (4).
1. Used to counteract hypotension- controversial and short term only increases VR to the heart up to 1L into the central circulation.
2. Causes reduced blood flow to the LE
3. May cause compression of the heart by abdominal contents pushing cephalad
4. Baroreceptors are activated- PV dilation and bradycardia may make "shock syndromes" worse in the long run.
31
What happens when the supine position is resumed from T-berg?
They could become more hypotensive especially if they are hypovolemic to begin with.
32
What are the ventilatory changes associated with T-berg?
1. Contents of the abdomen are pushed upwards impeding diaphragmatic excursion, compresses the lung bases, decreases lung compliance, decreases FRC and PIP increases. ETT could be shifted into R mainstem as everything shifts up.
33
What are the risks associated with T-berg?
Aspiration and face and airway edema can lead to airway obstruction. Look for periorbital, lip and tongue edema.
34
What kind of changes do we see in cerebral blood flow with T-berg? (3). Who would not be a good candidate for this?
Increased intracrainal vascular congestion due to gravity.
Increased ICP.
Increased IOP
Neuro patients in which increased ICP is a problem. Severe glaucoma.
35
Why and when do we use Reverse T-berg? What is it a variation of in terms of physiologic changes?
Use it to enhance surgical exposure of the upper abdomen by shifting the abdominal contents caudad. Variations may be used for shoulder, neck, breast, ENT and intracranial surgery. Variation of sitting position in terms of physiologic changes.
36
What do we need to worry about in regards to patient positioning with reverse T-berg?
Patients can slide. We may want a footboard. Worry about hyperextension. Would want to relieve that pressure every now and again. Could cause anterior tibial nerve injury which would result in foot drop.
37
Name four cardiovascular changes associated with Reverse T-berg. Name something we can do to monitor cerebral perfusion pressure?
Reduced preload, CO (20-40%) and BP
Compensatory increased SNS, SVR and HR plus or minus 30%. (be careful it could be blunted by anesthetics give lower dose and fluid bolus)
Activation of RAAS
Venous pooling in the lower extremities (use compression stockings)
Move the transducer of the aline to the circle of willis.
38
What happens when the supine position is resumed from the sitting position?
Increase in VR so your BP should normalize.
39
What ventilatory changes can we expect with reverse T-berg?
Abdomen is not going to impede diaphragmatic excursion so FRC increases.
Ventilation is easier (yay!)
40
What cerebral blood flow changes can we expect with reverse t-berg? Who would benefit?
Cerebral blood flow decease proportional to the degree of head up (can be up to 20%).
Intracranial pressure decreases. Neuro patients
41
Describe lithotomy position.
Calf support stirrups or candy canes. Hips are flexed 80-100 degrees. Legs abducted 30-45 degrees from midline. Lower legs parallel to torso. Watch femoral sciatic, lower leg nerves
42
What do we worry about injury wise with the lithotomy position?
Pinching the hands in the footboard if they are tucked, perfusion pressure of the toes (we could end up with compartment syndromes) and legs resting against the metal stirrups causing compression nerve injuries to either the inside or outer calf.
43
If the candycanes rested on the outside of the leg which nerve are we worried about? The inside of the leg? What about the femoral and sciatic, why do we have to watch them?
Outside-common peroneal
| Inside-saphenous. Sciatic because of the stretch on the gluts and femoral from being pinched.
44
In the knee crutch style of litotomy position which nerve do we have to watch out for in addition?
The popliteal nerve.
45
When are lower extremity injuries more common?
Low body mass index, prolonged surgery, recent cigarette smoking.
46
When positioning someone in the lithotomy position do we position their legs one at a time or together? Why?
Together to avoid torsion of the lumbar spine and hip flexion beyond 100 degrees. We flex them at the hip and knee, elevate and separate.
47
What could cause a sciatic nerve injury in the lithotomy position?
Excessive external rotation of the hips and pressure in sciatic notch from stretching
48
What are the common symptoms of a sciatic nerve injury?
weakness or paralysis of muscles below the knee, numbness foot and lateral half of calf and foot drop
49
How could the femoral nerve be injured during the lithotomy position?
Compression at pelvic brim by retractor or excessive angulation of thigh/abduction of thighs and external rotation of hips.
50
What does a femoral nerve injury result in?
Loss of flexion of the hip and loss of extension of the knee, decreased sensation over superior aspect of the thigh
51
When does lower extremity compartment syndrome occur?
When perfusion to an extremity is inadequate, resulting in ischemia, edema and extensive rhabdo from increased tissue pressure. Occurs in long surgical procedures (over 2-3 hours) and in lithotomy and lateral decubitis positions.
52
What are the cardiovascular changes associated with the lithotomy position?
Increased venous return/increases preload to the heart with a transient increase in CO and BP. Perfusion to the lower extremities is reduced.
53
What are the vent changes associated with the lithotomy position?
Depends on the degree of hip flexion whether or not the abdominal contents are pushed up on the diaphragm and impede excursion, with a reduction of lung compliance, and decrease in TV and VC. Sometimes this can be combined with trendelenberg and we are definitely at an increased risk for aspiration.
54
What are the cerebral changes associated with the lithotomy position?
Transient increase in cerebral venous blood flow and increase in ICP with legs elevated.
55
In the prone position are the legs bent? Why or why not?
Yes. To increase venous return.
56
In the Wilson Frame what is free and for what?
The abdomen for ventilatory expansion.
57
When do we use Mayfield Head Tongs/Pins? What do we need to watch for?
When we really dont want the head to move at all. 2 or 3 pins are embedded into the skull and then we attach the whole component to the skull. We dont want them to cough, move or wake up. Watch for slippage of the neck alignment, nose and metal components touching.
58
Once moved into prone position what is the first thing you need to do and why? Then what?
Check breath sounds. It is a whole lot freaking easier to turn them back and redo it now then realize 30 minutes into a case that you have a mainstem. Then hook back up your monitors, check your IV's and alines, check for pressure on the eyes, nose, UE breasts, genitals, anterior iliac crest. Check neck alignment
59
Why do we support the chest and hips in the prone position?
To allow for free abdomen for diaphragmatic movement
60
What do we need to pay attention to in the head/neck for prone position?
We can turn the head to the side if adequate mobility, head can be supported face-down with it's weight on bony structures. Neck is in neutral alignment, not excessive flexion or extension.
Eyes, nose, ears free of pressure.
61
What kind of eye injuries do we see with prone positioning?
Corneal abrasions from direct trauma, dry eye or swelling- antibiotic ointment and an eye-patch.
Blindness- ischemic optic neuropathy via central vein or artery obstruction or via sustained direct pressure on the eye/retina
62
What are the symptoms of ischemic optic neuropathy and risk factors? When is it an extreme caution?
visual changes, partial or complete blindness. RF: prone, operative hypotension, large operative blood loss, large crystalloid use, anemia, smoker, DM, vascular pathology or HTN, male.
Spinal surgery and cardiac surgery.
63
How are the extremities positioned in prone?
Arms: on boards by head, abducted less than 90 degrees, extra padding at the elbow, prevent shoulders from sagging, tucked at sides watch for thoracic outlet syndrome- have the patient raise their arms and check for pulses and numbness and tingling.
Legs: Slightely flexed, elastic compression stockings/SCD
64
What are three possible cardiovascular changes associated with the prone position?
1. IVC and Aortic compression- leading to hypotension- rolls or similar devices free the abdomen and chest improving flow.
2. Venous pooling in lower extremities- hypotension (decreased preload, co and BP)-put scds on them.
3. Hypotension associated with the move to prone position must be anticipated, monitored and treated
65
What ventilatory changes are associated with prone positioning?
V:Q mistmatch the posterior portion of our lungs is getting more ventilation than perfusion and the anterior portion of our lung is getting more perfusion than ventilation.
Cephalad displacement of the diaphragm-lung compliance decreases, Peak airway pressures increase, Work of breaking increases.
66
What should we use in the prone position to help ventilation?
Rolls/bolsters to free chest excursion. PPV overcomes compression effects.
67
What cerebral blood flow changes are associated with the prone position? (turning/flexing of the head)
Turning the head obstructs venous drainage leading to increased cerebral volume and ICP.
Excess flexion or turning- obstruction of vertebral artery flow.
Edema with too much flexion of the neck.
68
When do we use the lateral decubitus position?
Thoracotomy, kidney, shoulder and hip surgery.
69
What special positioning does the lateral decubitus position require?
```
Head support- neutral position- avoid misalignment of cervical spine, stretch brachial plexus.
Limited pressure on dependent eye and ear
Axillary roll (chest roll or chest support) placed caudad to and outside of the lower axilla.
```
70
What is the purpose of the axilla roll?
To keep the humeral head from compressing down on the brachial plexus.
71
How do we position the dependent and non-dependent arms in the lateral decubitus position?
Dependent- on padded arm board perpendicular to torso.
| Non-dependent arm supported over folded bedding or suspended with arm rest. We don't want it to sag.
72
How do we position the dependent and non-dependent legs in the lateral decubitus position?
Padding between knees and flexed dependent leg (watch for saphenous nerve injury) padding on bed (to prevent common peroneal nerve injury.
73
Where is the safety strap in the lateral decubitus position?
Between the head of the femur and the iliac crest.
74
Do we see cardiovascular changes in the lateral decubitus position?
Minimal unless you use the kidney rest which could obstruct venous return. NIBP measurements will be different in two arms-higher in dependent arm
lower in non-dependent arm.
75
Do we see ventilatory changes in the lateral position?
YES!
76
For an awake and spontaneously breathing patient in the lateral position what kind ventilatory changes do we see?
Dependent lung is both better perfused and better ventilated but lung volumes FRC, VC and TV decrease- we still have compliance and elastic recoil when you are awake.
77
For an anesthetized but spontaneously breathing patient what kind of V:Q mismatch do we see?
Non dependent lung is better ventilated and dependent lung is better perfused.
78
In an anesthetized mechanically ventilated patient what type of V:Q mismatch do we see?
Non dependent lung is overventilated and dependent lung is overperfused (worse V:Q mismatch)
79
Do we see cerebral blood flow changes in the lateral position?
Minimal change unless there is extreme flexion of the head.
80
When do we use the sitting position? Why?
Used for cranial surgery, shoulder and humeral procedures. Facilitates venous drainage and is excellent for surgical exposure/access.
81
What do we want to avoid when positioning the head in the sitting position?
Excessive cervical flexion- which obstructs venous outflow causing hypoperfusion or venous congestion in the brain, stretch cervical nerve roots, can obstruct ETT, can place pressure on the tongue and cause swelling.
82
Do we use a rigid bite block in the sitting position?
No, tongue ischemia.
83
How are the are the arms, butt, hips, knees and feet positioned in sitting position?
Support the arms, avoid pressure on the frame and avoid traction pulling down on shoulders which could cause a brachial plexus injury. Butt is positioned in the break of the table. The knees and hips are flexed- decrease the stretch of the sciatic nerve, SCD's on, feet are supported and padded.
84
What kind of cardiovascular changes to we see in the sitting position?
Pooling of blood in LE's
Hypotension
HR and SVR increase compensatory (blunted by anesthetics)
85
How do we treat cardiovascular changes of the sitting position?
IVF, vasopressers, adjustments of anesthetic depth, elastic stockings and active leg compression devices.
86
What kind of ventilatory changes do we see in the sitting position?
Lung volumes and capacities increase.
Lung compliance increases
Work of breathing is easier
Mechanical ventilation and spontaneous ventilation are easier.
87
What kind of changes do we see in cerebral blood flow in the sitting position? What could positioning impede?
Cerebral blood flow is decreased
Intracranial pressure is decreased
Positioning could impede arterial and venous blood flow causing hypoperfusion or venous congestion of the brain
88
What is the problem with a lower venous pressure in the sitting position?
It can entrain air, the sinuses can't collapse so worry about entrapped air embolism
89
When is a venous air embolism a risk?
Any time the surgical site is above the level of the heart.
90
What are the signs of a VAE?
change in heart tones (wind mill murmur) heard via a doppler placed at the parasternal border (2-6th IC space), new murmur, dysrhythmias, hypotension, desaturation, decreased etCO2, nitrogen in exhaled gas, circulatory compromise and cardiac arrest.
91
How do we detect entrained air?
TEE or precordial doppler ultrasound
92
What is the treatment for VAE?
Flood the surgical field with NS, apply wax to cut bony edges, close any open vessels, discontinue nitrous oxide, place on 100% O2, Peep, t-berg position, aspirate air from right atrium via a catheter.
93
Why do we discontinue nitrous oxide with a VAE?
Because nitrous would expand whatever air has become trapped.
