Exam 3 - positioning Flashcards
Positioning lecture and nerve injury including lab
Ischemic optic neuropathy consequence
Increase risk of post op vision loss
Obturator nerve injury consequence
Inability to ADDuct leg
Direct pressure on globe consequence
Cerebral Retinal artery occlusion
Saphenous nerve injury consequence
Parasthesia along medial & anteromedial CALF
Femoral nerve injury consequence
Absent knee-jerk reflex
Most common peri operative eye injury is
Corneal eye abrasion
*this is why we tape eyes
Median nerve injury consequence
Inability to oppose 1st and 5th digit
Radial nerve injury consequence (2)
Wrist drop
Ape hand
Ulnar nerve injury consequence
Claw hand
Anterior Tibial nerve injury
Foot drop
Sciatic Nerve injury consequence
Foot drop
Common Peroneal nerve injury consequence
Foot Drop
Shunt
More blood flow than O2 exchange
Dead space
Less blood flow than alveolar gas exchange
Factors that increase shunt
COPD
Pulm edema
Pneumonia
Factors that increase dead space
anything that decreases perfusion to well ventilated alveoli
Hemorrhage
Hypovolemia/hypotension
Pulmonary embolism
anticholinergic drugs
IRV
Inspiratory reserve volume
ERV
Expiratory reserve volum
RV
Residual volume
Inspiratory Capacity (IC) =
IRV + TV
FRC =
ERV + RV
Whatis left risidually after exhale of quiet breathing (TV)
VC (vital capacity) =
IRV+Vt+ERV
Expiratory reserve volume (ERV)
the amount of volume that can be expired with effort past quiet expiration
Functional Residual Capacity
the amount of air in the lungs after normal respiration
ERV + RV
Function of gases remaining the in the lungs at the end of expiration (FRC) (3)
- prevent alveolar collapse
- continue to oxygenate pulmonary blood flow through the cappilaries
- allows non hypoxic apnea and is the reserve of O2
Inspiratory reserve volume (IRV)
extra volume of air that can be inspired with maximal effort after reaching the end of normal, quiet respiration
Tidal Volume
Amount of air that moves in and out of the lungs during quiet respiration
Vital capacity
the greatest volume of breath that can be expelled from lungs after taking the deepest possible breath
Inspiratory capacity
maximum volume of air that can be inspired
TV+IRV
Total lung capacity
volume in the lungs after maximal effort inspiration
Arterial Baroreceptor reflex is a ____ loop
negative feedback
Arterial baroreceptor location (3)
- Carotid sinuses
- Aortic Arch
- Pulmonary arteries
baroreceptors responsible for position changes are mostly in
Carotid Sinus
_____ blocks the Bezold-Jarisch Reflex
Ondansetron
How does gravity effect going from standing to supine
Blood no longer goes as much to legs and feet = increased blood volume in thoracic compartment
increased preload and stroke volume
Reverse trendelenburg is
head up
Reverse trendelenburg BP head vs heart
BP head < BP heart
Trendelenburg is
head down
Trendelenburg BP head vs heart
BP head > BP heart
dead space is:
the volume of breath that does not participate in gas exchange
Physiologic or total deadspace is the sum of
anatomic dead space +alveolar dead space
Anatomic deadspace definition and examples
volume of gas within conducting zone
ex) trachea, bronchus, bronchioles, terminal bronchioles
Anatomic deadspace volume in upright position (amount)
2mL/kg
cardia reflexes are
fast acting loops between heart and CNS
regulate cardiac function and maintain homeostasis
Components of cardiac relfexes (5)
- Sensor and stimulus
2.afferent nerves
3.Processor
4.Efferent nerves
5.Effector
Bainbridge relfex
IV infusion increases R. atrial pressure –> stimulate R. atrial receptors–>increase HR and increase CO
Baroreceptor relfex
Increased CO –> increased arterial pressure —>decrease HR
Bezold - Jarisch relfex complex
Orthostasis –> decrease CO and BP–>decrased LV end diastolic volume –>LV mechanoreceptors—>increase in vagal efference and decrease in sympathetic tone –>syncope
Bezold - Jerisch reflex basic MOA and result
Decreases HR by inhibiting sympathetic drive
causes hypotension and peripheral dilation
Alveolar dead space
volume of gas within unperfused alveoli
Ratio of physiologic dead space to tidal volume is usually
1:3
Factors that increase dead space are
and examples
anything that decreases perfusion to well-ventilated alveoli
PA thrombis, hemorrhage, hypotension, surgical manipulation of pulmonary tree
Anticholinergic drugs increase ______ by _____
increase dead space by impairing ventilation rather than perfusion
Alveolar ventilation is
the portion of oxygen that reaches the alveoli and takes part in gas exchage
Normal alveolar ventilation
4L/min
Normal perfusion (CO) is
5 L/min
What causes reduction in FRC?
Changes from upright to supine OR
lateral to prone
Reduction in FRC causes
Airway closer in dependent lung regions
Early airway closure leads to
decreased ventilation in dependent regions
Factors that cause early airway closure are _____ (3) and cause ____
- position
- obesity
- elderly
cause closing capacity
closing capacity
volume of air that is not utilized d/t early airway closure
compliance is best at the _____ of the lung due to ______
best at the base of the lung due to gravity
Perfusion is best at the _____ of the lung due to _____
best at the base of the lung due to gravity
V/Q ratio is highest at the _____ and lowest at the ____
highest at the top of the lung, lowest at the base of the lung
Surgical factors that affect V/Q relationship (3)
- GA
- Mechanical ventilation
- Position
Gradient between V/Q occur in _____ of the lung fields reguardless of ____
occur in vertical axis regardless of position
Worst V/Q mismatch occurs in the (position)
lateral decubitus positioning
area of atelectasis causes
shunt (no gas exchange occurs in spite of perfusion)
Avg. Lung blood flow in lateral position
60% to dependent lung, 40% to non dependent
Aortocaval syndrome and causes
supine hypotensive syndrome
Great vessels compressed by large abdominal mass or gravida uterus
What position?
Lithotmy
most Lithotomy nerve injury is ____ and can cause _____
Common peroneal injury can cause foot drop
Complication of reverse trendelburg and sitting position (3)
- systemic hypotension
- Higher risk for cerebral ischemia
- air embolism
Compression of the chest/abdomen in prone position causes (3)
- CVP increased but LV volume is reduced
- Decreased venous return
- Increased intrathoracic pressure
Prone position complications (5)
- post op vision loss
- Neck torison from turning head
- Extreme rotation (occlusion of arteries)
- Brachial plexus injury
- Increased intrathoracic pressure
Lateral decubitus
Lateral decubitus can cause
- V/Q mismatch
- decreased circulation to elevated kidney
- Brachial plexus injury (axillary roll)
Compression of dependent tissues can cause _____ (most common in _____).
Rhabdomylosis with acute renal failure (most common in in lateral position)
Factors that contribute to nerve injuries (5)
- Ancillary positioning devices
- Prolonged surgical procedures (>4hrs)
- Anesthetic technique
- Body habitus
- Pre-existing conditions
Dependent tissues in position can lead to _____
Edema and ischemic injury with peripheral nerve injury
Most commonly injured nerve
Ulnar nerve injury
Ulnar nerve injury manifestation
claw hand
Brachial plexus injury occurs during (3)
- Arm used as lever during prone position
- spreading of sternum (OHS)
- Axillary block
C5-7 spinal nerves innervate
serratus anterior muscle
Radial nerve injury manifestation
wrist drop
Median nerve injury manifestation
ape hand
Common peroneal nerve is a branch of the
sciatic nerve
Most frequently damaged nerve in lower extremities is
Common peroneal nerve
Common peroneal nerve injury results in
foot drop
Anterior tibial nerve injury results in
foot drop
Foot drop nerves:
- Sciatic nerve
- Common peroneal nerve
- Anterior tibial nerve
Femoral nerve injury occurs from ____ position
lithotomy
Femoral nerve injury manifestation
absent knee jerk reflex
Saphenous nerve injury occurs when
foot is suspended lateral to a vertical brace
-compresses against medial tibial condyle
Obturator nerve injury occurs from ___ position
Lithotomy
Obturator nerve injury manifestation
inability to adduct leg
Lithotomy position nerve injures ():
- Femoral nerve
- Obturator nerve
- Common peroneal (most common)