Positioning

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Positioning Nerve Injuries848th FST
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Positioning
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Supine Position

• Produces minimal effects on circulation and
  perfusion
• Pulmonary Functional residual capacity decreases
  about 800 ml when changing from standing to
  supine and abdominal contents produce cephalad
  compression of the lung bases
• Venous return facilitated by the flexion of the
  hips and knees (encourages drainage of the lower
  extremities
• Other Pad the heels, ulnar nerve and occiput

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Trendelenburg Position (Head Down)

• Circulation abdominal contents push cephalad
  against the diaphragm which causes compression of
  the lung bases and heart (decreases SV)
• Can increase risk of hypotension
• Pulmonary Compression of lung bases
• Venous return Should increase but may not help
  with decrease in blood pressure
• Other Will increase intracranial pressure by
  increase venous pressure
• Use with caution in obese patients

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Prone Position

• Circulation Pressure from operating room table
  causes cephalad displacement of abdominal
  contents, impediment of downward descent of
  diaphragm, and compression of both vena cava and
  aorta
• Pulmonary Peak airway pressures increase and
  pulmonary compliance decreases
• Venous Return may be hindered if vascular
  compression is severe

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Prone Position Continued

• Other
• Turning head may obstruct jugular venous drainage
  and vertebral artery blood flow
• Abdominal rolls placed under patients sides
  relieve abdominal compression and increase venous
  return to the heart
• Eases ventilation

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Lateral Decubitus

• Patient awake and spontaneously breathing
• Dependent lung is both better perfused and better
  ventilated
• Patient under anesthesia but spontaneously
  breathing
• Nondependent lung is better ventilated and
  dependent lung is better perfused
• Patient under general anesthesia and given muscle
  relaxants
• Nondependent lung is better ventilated and
  dependent lung is better perfused but V/Q
  mismatch is much worse

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Lateral Decubitus (on ventilator)

• Circulation will decrease if kidney rest is
  elevated against IVC
• Increased to dependent lung
• Pulmonary decreased ventilation of dependent
  lung due to pressure on lungs and heart from
  abdominal viscera
• Increased ventilation to nondepent lung
• Venous Return should pose no problems unless
  kidney rest is up
• Other place axillary roll under thorax just
  caudal to axilla

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Sitting Position

• Circulation facilitates venous drainage from
  head/neck and upper body
• Decrease in intrathoracic blood volume
• Pulmonary no changes
• May help to decrease any pressure from abdominal
  contents when compared to other positions
• Venous Return decreased cerebral perfusion
  pressure
• Decrease in cardiac output (can cause HOTN and
  bradycardia)
• Other principle hazard is air embolism

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Lithotomy Position

• Circulation No problem unless abdominal mass,
  gravid uterus or obesity interferes
• Pulmonary Cephalad diaphragm displacement
  compresses lung bases
• Venous Return elevation and lowering of
  extremities together permits the circulatory
  system to adjust to increased vascular
  capacitance
• Other Peripheral nerve injury is common
  (especially common peroneal but can also injure
  sciatic, femoral, saphenous and obturator nurves)

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Zones of the Lung

• Zone 1 Alveolar pressure exceeds either arterial
  or venous pressure and perfusion of the lung unit
  is prevented
• Although it is rarely present in the normal lung,
  Zone 1 can be produced by pulmonary HOTN,
  excessive PEEP, or overdistention of alveolar
  units from large tidal volume during
  positive-pressure ventilation

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Zones continued

• Zone 2 Arterial pressure exceeds alveolar
  pressure, whereas alveolar pressure remains
  higher than venous pressure
• This relationship is found in nondependent
  portions of the lung, and perfusion is the result
  of a fluctuating balance between arterial and
  alveolar pressure
• Zone 3 Hydrostatic forces in the dependent
  portion of the lung produce venous congestion and
  perfusion is determined by the difference between
  arterial pressure and venous pressure

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Zones in Different Positions

• Supine pulmonary circulation tends to be most
  congested on dorsal body wall (Zone 3) and least
  congested substernally (Zone 2)
• Reverse Trendelenberg Zone 3 moves toward lung
  bases as better ventilatory mechanics improve gas
  exchange
• Trendelenberg Zone 3 shifts cephalad into poorly
  ventilated lung apices, and abnormal
  ventilation-perfusion ratios can be expected to
  intensify

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Zones and Positions Continued

• Lateral Decubitus Down lung resembles Zone 3
• Whereas relative hypoperfusion of the up-side
  lung resembles Zone 3
• Ventral Ducubitus (Prone) perfusion of the
  entire lung fits into Zone 3

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Nerve Injuries
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Factors Contributing to the Development of Nerve
Injuries

• Positioning-related compression or stretching
  leading to nerve ischemia
• Coexisting diseases including diabetes mellitus,
  cancer, alcoholism, and vitamin deficiency
• Cigarette smoking

• Prolonged (greater than 2 hours) application of a
  tourniquet
• Hereditary neuropathy with liability to pressure
  palsies
• Congenital anomalies
• Type of surgery

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Common Nerve Injuries of the Upper Extremities

• Ulnar Nerve Injuries
• Brachial Plexus Injuries
• Radial Nerve Injuries
• Median Nerve Injuries
• Musculocutaneous Nerve Injuries

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Ulnar Nerve Injuries

• Most common postoperative peripheral neuropathy
• Anatomy of the ulnar nerve makes it vulnerable to
  injury (there is little tissue or fat around the
  elbow to protect the nerve from external
  compression)
• Evidence has shown that most perioperative ulnar
  injuries are not the result of faulty patient
  positioning

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Reducing the Risk of Ulnar Nerve Injuries

• Avoid obvious compression by using padded arm
  boards
• Avoid compressive restraints that exert downward
  pressure on the elbow
• Assure that surgical personnel do not compress
  patients arm
• Place blood pressure cuff proximally so that it
  does not impose on ulnar groove or cubital tunnel
• Avoid prolonged flexion of the elbow

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Ulnar Nerve Injury Manifestations

• Inability to abduct or oppose the fifth finger
• Diminished sensation in the fourth or fifth
  fingers
• Eventually atrophy of the intrinsic muscle of the
  hand (CLAW HAND)

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Brachial Plexus Injuries

• Second most common peripheral nerve injury
• Brachial plexus has long mobile course between
  two fixed points (the vertebral fascia proximally
  and the axillary fascia distally)
• Injury results during maneuvers that increase
  this distance and stretches the nerve
• In addition, the nerve lies in close proximity to
  several bony structures that can act as fulcrums
  and compress the nerve

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Brachial Plexus Injuries cont.

• How Injured
• Extension and lateral flexion of the head while
  the patient is in the supine or lateral decubitus
  position
• Allowing the arm to fall below the level of the
  operating table
• Suspension of upper arm in abduction from the
  operating table
• Abduction of the arm gt90 degrees in the supine or
  prone position

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Brachial Plexus Manifestations

• Weak arm function

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Radial Nerve Injuries

• Injury occurs with compression against the
  underlying humerus when the lateral arm is
  compressed on the operating table
• Injury can also occur with repeated inflation of
  an automatic blood pressure cuff

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Radial Nerve Injury Manifestations

• Wrist Drop
• Inability to extend the metacarpophalangeal
  joints
• Weakness in abduction of the thumb
• Decreased sensation over dorsal surfaced if the
  lateral 3 and one half fingers (first middle and
  ring)

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Median Nerve Injuries

• Lies in close proximity to the medial cubital and
  basilic veins and may be harmed by venous
  catheters or extravasation of intravenous drugs
• Positioning is an unlikely cause of median nerve
  injuries

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Median Nerve Injuries Manifestations

• Unopposed thumb
• Inability to oppose the 1st and 5th digits
• Decreased sensation on the palmer surface of the
  lateral three and one half fingers

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Musculocutaneous Nerve Injuries

• Nerve runs deep in the arm
• Although rare, this injury occurs due to
  compression
• Manifestations inability to flex arm and
  decreased sensation over the ventral surface of
  the forearm

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Nerves Commonly Injured in the Lower Extremities

• Common Peroneal Nerve
• Sciatic Nerve
• Saphenous Nerve
• Femoral Nerve
• Obturator Nerve
• Anterior Tibial Nerve

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Common Peroneal Nerve Injuries

• Most frequently damaged nerve of the lower
  extremity
• Damage can occur if the nerve is compressed
  against the head of the fibula when patients are
  in the lithotomy or lateral positions
• In the supine position, prolonged pressure in
  popliteal fossa by pillows

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Common Peroneal Injury Manifestations

• Foot drop
• Loss of dorsal extension of toes
• Inability to evert the foot

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Sciatic Nerve Injuries

• Sciatic nerve gives off branches in the thigh to
  the hamstring and divides into the common
  peroneal and tibial nerve
• Stretching injures can occur when the thigh is
  externally rotated and knee is extended in the
  lithotomy position
• Compression injuries can occur in the sitting
  position when pressure is applied to the ischial
  tuberosities on an improperly padded table

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Results of Sciatic Nerve Injuries

• Weakness of all skeletal muscles below the knee
• Diminished sensation of the lateral half of the
  leg and almost all of the foot
• Foot Drop
• Pain or numbness of lower leg, thigh, or foot

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Femoral Nerve Injuries

• Injured with compression at the pelvic brim by a
  retractor or excessive angulation of the thigh
• Also injured in the lithotomy position with
  extreme abduction of the thighs and external
  rotation of the hips

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Characteristics of Femoral Nerve Injuries

• Decreased or absent knee jerk
• Loss of flexion of hip and extension of the knee
• Decreased sensation over superior aspect of the
  thigh and medial and anteromedial side of leg

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Saphenous Nerve Injuries

• Saphenous nerve is a branch of the femoral nerve
• Damaged occurs by compression when the medial
  aspect of the lower leg is suspended outside an
  unpadded support while in the lithotomy position.
• Results paresthesias along the medial and
  anteromedial side of the calf

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Anterior Tibial Nerve Injuries

• Injured with plantar flexion of the feet for
  extended periods of time
• Manifestations Foot Drop

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Obturator Nerve Injuries

• May be damaged during difficult forceps delivery
  or by excessive flexion of thigh to the groin
• Result of injury
• Inability to adduct the leg
• Diminished sensation over medial side of the
  thigh

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Questions