Positioning

Question 1

What are the primary mechanisms of nerve injury?
What is the component of injury that is common to all
nerve injuries?

Answer 1

The primary mechanisms responsible for peripheral nerve injury
are transection, compression, stretch, and kinking, but the
component that stems from these mechanisms and is common
to all peripheral nerve injuries is ischemia.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 405.

Question 2

Why is it important to ask patients preoperatively

about tingling in the hands or fingers?

Answer 2

A significant number of patients exhibit mild ulnar neuropathies
preoperatively in both arms that can worsen despite
conventional positioning and padding. For this reason, it is
important to ask the patient about elbow problems, ‘funny bone’
sensitivity, or neuropathies in the hands and fingers and
document them carefully.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 810.

Question 3

What is compartment syndrome and what factors

contribute to the development of this condition?

Answer 3

Compartment syndrome occurs primarily as a result of
inadequate perfusion to an extremity for any reason. Factors
that contribute to the development of compartment syndrome
include systemic hypotension, pressure against the extremity by
an extremity holder or pressure by any compressive wrap or
sheets used to secure an extremity, excessive flexion of the
extremity, elevation of the extremity, or surgery length greater
than five hours.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 811-812.

Question 4

What are the most common causes of postoperative
vision loss in patients undergoing surgery in the
prone position?

Answer 4

The five causes of vision loss during prone procedures in
patients undergoing nonopthalmologic surgery are 1) central
retinal vein occlusion, 2) glycine toxicity, 3) ischemic optic
neuropathy, 4) central retinal artery occlusion, and 5) cortical
blindness. Ischemic optic neuropathy and central retinal artery
occlusion account for 89% of cases of postoperative vision loss
in patients undergoing surgery in the prone position.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 409.

Question 5

What are the major factors that increase the risk of
postoperative blindness in a patient in the prone
position?

Answer 5

Factors associated with a higher risk for developing
postoperative blindness following prone procedures include
prolonged surgical duration, anemia or massive blood loss, and
hypotension.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 817.

Question 6

With what surgical position is rhabdomyolysis

associated?

Answer 6

Rhabdomyolysis is associated with the lateral decubitus
position. Factors that are considered to contribute to this
phenomenon include prolonged surgical time, hypotension, and
the pressure of the OR table against the gluteal and flank
muscles.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 417.

Question 7

How do respiratory parameters change in a
spontaneously breathing, anesthetized patient when
placed in the lateral decubitus position?

Answer 7

In the spontaneously breathing, anesthetized patient in the
lateral decubitus position, the functional residual capacity
decreases almost immediately. The nondependent lung shifts
to a position of greater compliance. The dependent lung loses
FRC and becomes less compliant. As a result, ventilation is
preferentially distributed to the nondependent lung.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 404-405.

Question 8

What injuries are at risk for occurring when using a

traction table?

Answer 8

A traction table places the patient supine with one leg elevated
and the affected leg placed in traction. A perineal post is
positioned between the patient’s legs to keep them stationary
while the traction pulls on the leg. The elevated leg suffers the
risk of hypoperfusion while the perineal post poses a risk of
crushing the perineum.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 413.

Question 9

What is the most common peripheral nerve injured in

patients undergoing anesthesia?

Answer 9

The ulnar nerve is the most commonly injured peripheral nerve
in patients undergoing anesthesia. The risk is approximately 1
in 2700 patients. Most commonly, symptoms don’t develop until
24 hours after surgery and more than half of them resolve
spontaneously within a year.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 1212.

Question 10

What are the risk factors for ulnar nerve injury?

Answer 10

Risk factors for the development of an ulnar nerve injury include
male gender, thin body habitus, obese body habitus, and a
hospital stay greater than 14 days.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 1212.

Question 11

How do weight and gender influence the risk for

ulnar neuropathy?

Answer 11

Ulnar neuropathy occurs more often in patients with a high BMI
(>38) and occurs more commonly in men than in women. It is
believed to be more common in men because the tubercle of
the coronoid process is 1.5 times larger in males, the cubital
retinaculum tends to be thicker, and there is less adipose tissue
over the medial aspect of the elbow.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 407.

Question 12

What nerves may be damaged by extreme flexion of

the thighs?

Answer 12

Extreme flexion at the thigh can result in injury to the sciatic,
obturator, and femoral nerves.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 1213.

Question 13

Numbness and tingling along the medial aspect of

the calves is consistent with damage to which nerve?

Answer 13

The saphenous nerve, which innervates the medial calf.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 673.

Question 14

Loss of dorsiflexion to the foot would represent

damage to which nerve?

Answer 14

Loss of dorsiflexion of the foot is consistent with injury to the
common peroneal nerve.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 673.

Question 15

A patient experiences postoperative numbness to
the medial aspect of the foot. What nerve do you
suspect may be implicated?

Answer 15

The saphenous nerve, which is a branch of the femoral nerve,
innervates the medial aspect of the foot.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 1015-1017.

Question 16

What are methods you can employ to provide

protection from ulnar nerve injury?

Answer 16

The ulnar nerve is most at risk for compression damage where
it passes under the medial epicondyle. Pronation of the hand
positions the ulnar nerve directly against the table surface,
making it a high-risk position. Supinating the hand shifts the
ulnar nerve above the table or armboard surface and allows the
olecranon to bear the weight of the arm. Padding should be
placed around the elbows to protect the ulnar nerve, especially
when tucking the arms at the side.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 369.

Question 17

What are the respiratory changes you would expect
to occur in a patient placed in the lateral decubitus
position?

Answer 17

In the lateral decubitus position, the vital capacity is decreased
by about 10%. The FRC is also reduced, as is the mobility of
the diaphragm. The mediastinum is shifted into the dependent
hemithorax and can potentially result in a decrease in venous
return, especially in the kidney position. The dependent lung
receives an increase in pulmonary blood flow due to the effects
of gravity.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 368.

Question 18

What are the effects you would expect to see in a
patient changing from the erect position to supine
and why?

Answer 18

When moving from the erect to supine position, there is a
considerable increase in central blood volume. The resulting
stretch of baroreceptors in the central circulation result in a
decrease in MAP, heart rate, and peripheral vascular resistance
whereas cardiac output and stroke volume increase.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 363.

Question 19

What are the cardiovascular effects you would
expect to occur when placing a surgical patient in the
sitting position?

Answer 19

When placed in the seated position, the cardiac index,
pulmonary artery wedge pressure, and central venous pressure
decrease substantially, but the systemic vascular resistance
increases.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 403.

Question 20

What are the cardiovascular changes you would
expect to see in a patient placed in Trendelenburg
position?

Answer 20

In the Trendelenburg position, the MAP, pulmonary capillary
wedge pressure, and systemic vascular resistance increase
whereas the cardiac index, oxygen delivery, and oxygen
consumption remain unchanged. Despite these changes, the
significant increase in venous and cerebrospinal fluid pressure
create an offset that results in decreased arterial blood flow to
the brain.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 366.

Question 21

What are the adverse effects of steep reverse

Trendelenburg position?

Answer 21

Steep reverse trendelenburg position elevates the head, which
displaces the abdominal contents toward the pelvis resulting in
a decreased mean thoracic pressure. It also results in venous
pooling in the lower extremities which decreases preload and
cardiac output. The downward displacement of the abdominal
contents decreases the work of breathing while increasing
functional residual capacity and total lung volume.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 403-404.

Question 22

What concerns would you have regarding the use of
shoulder braces to prevent a patient from sliding
when placed in steep Trendelenburg position?

Answer 22

Shoulder braces placed medially (close to the neck) are
associated with a high incidence of brachial plexus injury at the
root level. If at all possible, shoulder braces should be
avoided. If they are used, placing them laterally over the
acromioclavicular joint reduces the risk of injury to the brachial
plexus.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 808