Positioning Flashcards
What is the anesthetist’s responisibility regarding positioning?
What are the goals of positioning?
- The anesthetist is responsible for supervising and assuring no nerve or soft tissue injury and to minimize physiological changes and treat changes appropriately
- Goals:
- appropriate surgical exposure/access
- comfort
- patient safety
How/why must the anesthetist be extremely vigilant?
- B/c the patient is unconscious, has no sensation, and is muscle relaxed
- You should establish new positions gradually, especially after a long surgery
- Documentation:
- describe baseline BOM
- describe intra-op position
- use of padding
- frame
- body position
- checks done and frequency
What is the weight limit of the OR table?
How is the pt transfered to the OR table?
- 136 kg (300 lbs)
- Transfer:
- OR table and stretcher must be locked
- make sure OR table has a draw sheet
- staff members on both sides
- pt moves self or moved by staff
- make sure head and neck are aligned with spine
- watch exctremeties
- watch IVs and monitors
- then apply safety strap
What are the most common operative positions?
- supine or Dorsal Decubitus position
- trendelenberg
- reverse trendelenberg
- Lithotomy
- Prone or ventral decubitus position
- lateral decubitus
- sitting
What are the benefits of the supine position?
- great access to airway
- access to arms for IVs and monitors
- less physiologic changes than in other positions
- ** most common, and most preferred by anesthesia
How do you appropriately position the head in supine position?
why?
- Pillow under the head
- allows proper sniffing position
- avoids dorsal extension and lateral flexion of neck
- avoids brachial plexus stretch and vascular compromise in neck
- doughnut shape pillow prevents allopecia
- no pressure on the eyes??
How can you arrange the arms in supine position?
- Arm boards:
- properly secured to table
- abducted <90 degrees to avoid stretch of brachial plexus
- padded
- safety straps
- hands supinated NOT pronated
- tucked
- draw sheet unter pt’s hip or torso, NOT mattress
- elbow padded, palm facing in
How should you position the feet in supine position?
How can you provide lumbar support?
- Feet
- heels not hanging over bed
- heels padded
- legs not crossed
- compression socks or SCT to reduce DVT risk
- Lumbar support
- slight flexion hips and knees
- pillow under knees (with caution, could add to DVT risk)
- legs/feet not crossed
What are different ways (mechanisms) that positioning can cause peripheral nerve injury?
- stretching- most common, can progress to ischemia
- compression
- kinking
- ischemia
- transection
Why is the brachial plexus at risk of injury?
What can cause a brachial plexus positioning injury?
- Because the nerve travels a long superficial course through fixed points
- the vertebral foramina fascia
- the clavicle
- the scapula
- the humerus
- positioning injury can occur with:
- neck extension, head turned to side or sagging
- excessive abduction of arm >90 degrees
- if arm or arm board falls off table
- depressed/sagging shoulders in sitting position
- extending arms overhead when prone
- compression of plexus agains thorax when lateral
- shoulder braces
- sternal retractors in cardiac surgery
What would be expected deficits from a brachial plexus injury?
- limp or paralyzed arm
- lack of muscle control in arm, hand, wrist
- lask of sensation in arm or hand
What can cause injury to the radial nerve?
What deficits occur if it is injured?
- Injury is due to external compression of the radial nerve on the lateral aspect of the humerus against:
- surgical retractors
- ether screet
- mismatched arm board
- repeat BP inflation
- Deficit if injured:
- loss of extension of forearm
- weakness of supination
- loss of extension of hand (wrist drop)
- loss of sensation in lateral arm, posterior forearm, part of hand
What is the most common postoperative peripheral nerve injury?
What can cause this?
- Ulnar nerve injury- higher incidence in muscular men; cannot always be prevented
- The nerve runs in the groove between the olecranon of ulna and medial epicondyle of humerus
- Injury with:
- compression of nerve between the olecranon of ulna and medial epicondyle of humerus (entrapment with arm extension)
- stretch with severe elbow flexion
- dislocation over medial epicondyle with pronation of hand causing stretching
- compression against bed
- misplaced BP cuff
What kind of deficits would an ulnar nerve injury cause?
- inability to abduct or oppose 5th finger
- loss of grip strength, esp. ulnar side of fist
- loss of sensation of palmar surface of hand and 4th and 5th fingers
- eventually, leads to atrophy of intrinsic muscle of hand (claw hand)
What are the cardiovascular changes seen in a pt in the supine position?
- minimal effects on circulation and perfusion
-
initially, will have increased venous return
- increased preload, SV, CO. BP
- this activates baroreceptors which decrease sympathetic outflow and incrases PSN impulses, leading to decrease in HR and PVR (unless blunted by anesthetics!)
-
later, they have reduced venous return due to venous pooling in lower extremities
- decrease CO, BP
- increase HR
- *possible IVC compression by masses, pregnancy, obese abdomen, or ascites may decrease venous return and CO even more
What are the ventilatory changes you would expect to see in the supine position?
- FRC decreases about 800 ml d/t dephalad displacement of the diaphragm and compression of lung bases
- lung volumes reduced by muscle relaxants
- loss of chest wall muscle tone with muscle relaxants–reduces opposition to inherent elastic recoil of pulmonary tissues
- overcome with positive pressure ventilation
What are the cerebral blood flow changes you would expect in supine position?
- Minimal change to CBF due to tight autoregulation
- therefore, ICP unchanged
Why is trendelenberg sometimes used?
What do you need to be excremely cautious about when placing your patient in trendelenberg?
- Used to treat hypotension by increasing venous return
- improves surgical exposure during abdominal and laparoscopic surgery
- helps prevent air embolism
- facilitates cannulation during central line placement
- Extreme caution with shoulder braces!
- if they must be used they should be well padded and placed laterally away from the root of the neck over the arcomioclavicular joint
What cardiovascular changes would you expect with your patient in trendelenberg?
What happens when supine position is resumed?
- Used to counteract hypotension- controversial and short term only
- increases venous return to the heart- up to 1 L
- increases work load of the heart
- Causes reduced blood flow to lower extremeties
- may cause compression of heart by abdominal contents pushing cephalad
- Pulmonary vascular congestion
- baroreceptors activated
- peripheral vasodilation and bradycardia, decreasing CO may make “shock syndromes” worse in the long run
- When supine position is resumed, venous pooling in LE and drop in BP occurs
What ventilatory changes would you expect when you put your patient in trendelenberg?
- decreased lung compliance, decrease FRC, increase PIP
- increased pulmonary vascular congestion
- increased WOB if spontaneously breathing
- V:Q mismathc with perfusion exceeding ventilation in the apex of the lung
- ETT is easily shifted into right mainstem bronchus as abdomen/thoracic contents shift cephalad
- check breath sounds after position changes
- increased risk of aspiration and regurgitation
- face and airway edema can lead to airway obstruction
- check for leak before extubating
What changes would you expect with CBF when a pt is in trendelenberg?
who would you NOT want to put into trendelenberg?
- Increases intracranial vascular congestion
- Gravity! Increased intracranial pressure which decreases CBF
- IOP increases
- You would NOT want to trendelenberg neuro patients or pts with gloucoma
What is reverse trendelenberg position used for?
What do the physiologic changes of this position compare to?
What do you need to be cautious with when placing your patient in reverse trendelenberg?
- Utilized to enhance surgical exposure of the upper abdomen by shifting the abdominal contents caudal
- ex: laparoscopic cholecystectomy
- variations of this position may be used for shoulder, neck, intracranial surgery
- this is a variation of the sitting position in terms of physiologic changes
- Caution with foot board
- excessive plantar flexion for extended time can cause anterial tibial nerve injury resulting in foot drop
What cardiovascular changes would you anticipate in reverse trendelenberg?
- reduced venous return leading to decreased preload, CO (20-40%), and BP
- Compensatory increased SNS tone, SVR and HR +/-30% (may be blunted by anesthetics)
What ventilatory changes would you anticipate in reverse trendelenberg?
- FRC increases
- ventilation is easier
- abdomen does not impede diaphragm
What cerebral changes would you anticipate in reverse trendelenberg?
- CBF decreases proportional to the degree of head up tilt (up to 20%)
- ICP decreases
- *beneficial for neuro pts or those with elevated ICPs
What is lithotomy position?
- Hips flexed 80-100 degrees
- legs abducted 30-45 degrees from midline
- lower legs parallel to torso
- watch femoral sciatic, lower leg nerves
- Lithotomy position can be done with calf support stirrups or candy cane stirrubs
How does the lithotomy position change when using candy cane stirrups?
- Usually more acute flexion of the knees and/or hips
- Watch for injury to:
- common peroneal nerve- from the leg resting on bar
- sciatic
- femoral
What do you have to watch for when putting a patient in lithotomy with knee krutches?
- Watch for popliteal nerve injury
What is lithotomy often used for?
How is it achieved?
What can improper positioning cause?
- used for gyn, GU, and rectal procedures
- both legs are positioned into stirups together to avoid torsion of the lumbar spine and hip flexion beyond 110 degrees and avoided
- improper positioning can lead to injuries of:
- femoral
- sciatic
- obturator
- lateral femoral cutaneous
- saphenous
- common peroneal
What is the most commonly injured nerve of the lower extremeties?
What causes it?
What are the symptoms?
- Common peroneal nerve- a branch of sciatic
- Injury from compression of lateral aspect of knee against stirrup or later position
- Symptoms:
- foot drop
- inability to evert the foot
- loss of dorsal extension of toes
What causes sciatic nerve injury?
What are the symptoms?
- Caused by:
- excessive external rotation of hips
- pressure in sciatic notch from stretching
- Symptoms:
- weakness or paralysis of muscles below knee
- numbness of foot and lateral half of calf
- foot drop
What causes femoral nerve injury?
What does this result in?
- Caused by:
- compression at pelvic brim by retractor
- excessive angulation of high/abduction of thighs and external rotation of hips
- Results in:
- loss of flexion of hip and loss of extension of knee
- decresed sensation over superior aspect of thigh
What causes a saphenous nerve injury?
What does this result in?
- Caused when medial aspect of lower leg is compressed agains the support bar
- Results in paresthesias medial and antermedial side of calf
When does lower extremity compartment syndrom occur?
- Occurs when perfusion to an extremity is inadequate, resulting in ischemia, edema, and extensive rhabdomyolysis from increased tissue pressure
- anytime there is prolonged compression
- surgical procedures >2-3 hours
- occurs with lithotomy and lateral decubitus positions
