Which of the 14 AANA standards relates to patient positioning?
Standard 8
What happens to cardiac output in the supine position?
there is a transient increase in venous return, which increases SV and CO
What happens to BP in the supine position?
There is an increase in BP d/t transient increased CO that activates afferent baroreceptors in the aorta and the carotid sinuses.
How is CO returned to normal in the supine position?
Mechanoreceptors in the atria and ventricles are activated and decrease SNS outflow. Atrial reflexes also regulate renal sympathetic activity (renin, ANP, and vasopressin). Ultimately HR, BP and CO return to baseline.
What happens to lung volumes in the supine position?
decreased TV
decreased FRC (cephalad displacement of the diaphragm)
What is the maximal angle for arm abduction? How should palms be faced? Why?
90 degrees
Palms supinated (faced up) to avoid ulnar nerve compression
With arm adduction, how should the hands be placed?
palms up or in neutral position (faced towards the body)
What are some complications of the supine position?
- backache
- pressure alopecia
- brachial plexus or axillary nerve injury if arms are abducted greater than 90 degrees
- ulnar nerve injury if hand/arm are pronated
- stretch injury to brachial plexus if neck extended and head turned away
Patients with kyphosis, scoliosis or a history of back pain may require what in regards to supine positioning?
extra padding or slight flexion at the hip and knee
What used to be the most common nerve injury associated with GA? Recently, what is the leading nerve injury reported with GA?
Historically: ulnar neuropathy
Recent: brachial plexus
What should you use to prevent patient from cephalad shifting when in Trendelenburg position? What should you avoid using? Why?
Use: non-sliding pad
Avoid: bean bags or shoulder braces d/t compression of brachial plexus
what happens to CO in Trendelenburg position?
CO increases by 9% (d/t increased VR from lower extremities)
What are some problems associated with T-burg position?
increased ICP
increased IOP
edema to face, conjunctiva, larynx and tongue
increased intra abdominal pressure
increased aspiration risk
risk of endobronchial intubation (abd contents shift carina cephalad)
What happens to lung volumes in T-burg position?
decreased FRC
decreased TV
What are a few pathophysiologic complications of reverse T-burg?
hypotension (d/t decreased VR)
decreased perfusion to brain (cerebral oximetry may be useful)
Where should you zero the A-line transducer in a patient in reverse T-burg position?
at the circle of Willis
When you put a patient in seated position what can you do to take pressure off of the sciatic nerve?
Flex hips (less than 90 degrees) and flex the knees
What can you do to support venous return in the seated position?
compression stockings and wraps
How many finger breadths need to be between the chin and sternum to allow adequate arterial and venous blood flow?
at least 2 fingerbreadths
list some concerns or risks for surgeries performed in the sitting position?
venous air embolism
pneumocephalus
quadriplegia/ spinal cord infarction
cerebral ischemia
peripheral nerve injuries
hypotension and decreased cerebral perfusion
What are some things to keep in mind when intubating and monitoring a patient in the prone position for surgery?
intubate supine and then pronate
place EKG leads on the back
keep head in a neutral position (turning head to the side can increase risk of jugular or carotid occlusion
What are some risks associated with the prone position?
facial and airway edema
nerve injuries (to the ulnar nerve and brachial plexus if arms abducted > 90 degrees)
eye injuries and post-op vision loss
EET or IV dislodgement
What does the prone position do to abdominal pressure? What effect does this have on CO?
increases abdominal pressure, which decreases VR (d/t compression of the IVC) and decreases overall CO
What does the prone position do to V/Q ratio?
improves the V/Q ratio (less mismatch)
