5) Positioning & Maintenance

define functional residual capacity (FRC)

volume of lungs after passive exhalation (reserve)

patient positions from biggest FRC to smallest

standing > sitting > prone > lateral > supine

define supine position

laying on back, neutral neck, hands supinated/neutral, legs uncrossed, compression stockings

main benefit of supine position and why

hemodynamics best maintained bc body at level of heart

padding for supine position

heels, elbows, occiput, pillow under knees

define trendelenburg

supine but head down

what surgeries use trendelenburg position?

lower abdominal, gyne & urology

↑ or ↓: venous return in trendelenburg

increase

↑ or ↓: central venous pressure in trendelenburg

increase

↑ or ↓: intracranial and intraocular pressure in trendelenburg

increase

in trendelenburg, swelling of what can occur and how is it fixed?

swelling of face, larynx, tongue can be fixed by head up

↑ or ↓: FRC in trendelenburg and why

decreased bc cephalad movement of abdominal organs

in mechanically ventilated patients in trendelenburg, what changes?

increased peak inspiratory pressures

in spontaneously ventilated patients in trendelenburg, what changes?

increased breathing work

define reverse trendelenburg

supine but head up

what surgeries use reverse trendelenburg position?

upper abdominal, lap chole, breast

↑ or ↓: venous return in reverse trendelenburg

decreased

↑ or ↓: perfusion to brain in reverse trendelenburg

what do you have to pay attention to because of this change?

decreased, MAP

↑ or ↓: FRC in reverse trendelenburg

increased

define lithotomy position

supine but legs abducted 30-45 degrees and hips flexed 80-100 degrees

what surgeries use lithotomy position?

gyne, rectal, urology

how are legs supported and moved in lithotomy?

stirrups, raised and lowered together

if the foot section is lowered in lithotomy position, what should you watch out for?

fingers for crush injury

↑ or ↓: venous return in lithotomy

increased

↑ or ↓: FRC in lithotomy

decreased

common nerve injuries in lithotomy

common peroneal: outside of fibula presses against stirrups
sciatic: hyper-flexion of hips

what surgeries use lateral decubitus position?

thoracic, hip

if surgeon must have arms >90 degrees, how do you make sure patient is comfortable?

bend elbows

right side lateral decubitus = ________ side down

right

dependent arm = ↑ or ↓ arm

down

in lateral decubitus, why is an axillary roll used?

avoid compression injury to dependent brachial plexus and blood vessels

in lateral decubitus, where do you put the axillary roll?

caudal and 1 hand width away from dependent axilla

independent lung = ________ lung

operative

how are legs positioned in lateral decubitus?

flexed at 90 degrees, pillow between knees

why is bean bag used in lateral decubitus?

keeps patient from rolling

in lateral decubitus, what arm do you put pulse ox and blood pressure and why?

dependent to monitor arterial compression

how and why is kidney rest used in lateral decubitus?

under iliac crest to avoid inferior vena cava compression

define hypoxic pulmonary vasoconstriction (HPV)

lung shunts blood to areas with better ventilation

how is V/Q affected in the dependent lung in lateral decubitus?

decreased ventilation, increased perfusion

what causes changes to V/Q in lateral decubitus?

mediastinum weight, cephalad pressure of abdominal organs, gravity

dependent lung in lateral decubitus has ________ V/Q

low

how is V/Q affected in the independent lung in lateral decubitus?

increased ventilation, decreased perfusion

independent lung in lateral decubitus has ________ V/Q

high

define prone position

laying face down

what surgeries use prone position?

posterior skull, posterior spine, perirectal

in prone, if belly can hang freely (no abdominal pressure), pulmonary function is…

retained

why is wilson frame used in prone position?

lets belly hang free to maintain lung compliance and decrease bleeding

when to intubate when using prone position

on stretcher before positioning

what to check after patient is turned prone?

bilateral breath sounds

compressed abdomen causes decreased…

venous return and FRC

where to put chest rolls in prone position?

iliac crest to clavicle

when moving patient from stretcher to OR table, it is important to maintain…

head/neck in line with spine and control of ETT

when turning patient prone, ________ circuit

disconnect

prone position safety checks

pressure points, supported shoulders, neutral neck, breasts/genitalia free of pressure

in prone, where are ECG leads placed?

back

what surgeries use mayfield tongs/horseshoe?

neurosurgery

what surgeries use sitting/beach chair position?

head, shoulder

what about sitting/beach chair position can cause risk of venous air embolism?

heart is below surgical site, areas above have sub-atmospheric venous pressure so if vein gets nicked, air can be entrained

in sitting/beach chair position, how is head positioned?

fixed in pins or special holding device

in sitting/beach chair position, how is the neck positioned?

>2 finger widths between mandible and sternum

in shoulder surgery using beach chair position, where do monitors go?

IV, NIBP, pulse ox on same side

in beach chair position, is the NIBP a good representation of cerebral perfusion pressure?

no, pressure at brain is lower

hypotension is important to monitor in sitting/beach chair position because…

blood can pool in lower extremities

for every 1 inch of vertical height between heart and brain, pressure decreases by…

1.86 mmHg

for every 1 foot of vertical height between heart and brain, pressure decreases by…

22.4 mmHg

symptoms of ulnar nerve injuries begin…

24 hrs after surgery

how to avoid ulnar nerve injuries

avoid pressure on postcondylar groove of humerus (elbow)

brachial plexus can be injured from…

stretch & compression

how to avoid brachial plexus injury

avoid shoulder braces, excessive lateral rotation of head, and high axillary roll

how to avoid sciatic and common peroneal nerve injury

minimize time in lithotomy, avoid excessive flexion of hips and pressure on peroneal nerve, move legs together

most common eye injury

corneal abrasion

perioperative vision loss (POVL) is caused by…

ischemic optic neuropathy (ION)

prolonged hypotension

prolonged prone position

large crystalloid use

large blood loss (anemia)

what MAC will prevent movement in 95% of surgical patients?

1.2 MAC

what MAC will prevent movement in 99% of surgical patients?

1.3 MAC

factors that increase MAC (less potent)

acute amphetamines
chronic alcohol
young (highest at 6 months)
hyperthermia
red hair

factors that decrease MAC (more potent)

chronic amphetamines
acute alcohol
old
hypothermia
hypnotics
opioids

volatile anesthetics cause shapid breathing, what does this mean?

increases respiratory rate, decreases tidal volume

what are the main 3 drawbacks of volatile anesthetics?

trigger malignant hyperthermia, decrease BP, financial/environmental impact

what gas uniquely has analgesic properties?

nitrous oxide

benefits of nitrous oxide?

odorless, lowers MAC of halogenated agents, rapid on/off

drawbacks of nitrous oxide

increase PONV, many contraindications (ex: high intra-ocular pressure), stays in atmosphere for over 100 years

what receptors do opioids bind to?

mu1, mu2, kappa, delta

what do opioids do?

mitigate transfer of pain to brain

side effects of opioids

nausea, pruritus (itching), respiratory depression

why can people have allergic reactions to morphine?

histamine release

morphine dose

10mg

morphine onset

5-10 min

morphine peak

>30 min

morphine duration

3-4 hrs

hydromorphone (Dilaudid) dose

1.5mg

hydromorphone (Dilaudid) onset

10-15 min

hydromorphone (Dilaudid) peak

10-20 min

hydromorphone (Dilaudid) duration

2-3 hrs

fentanyl (Sublimaze) dose

100mcg

fentanyl (Sublimaze) onset

1-2 min

fentanyl (Sublimaze) peak

3-5 min

fentanyl (Sublimaze) duration

0.5-1 hr

ketorolac (Toradol) inhibits what?

cyclooxygenase (COX), prostaglandin synthesis, platelet aggregation

ketorolac (Toradol) onset

10 min

ketorolac (Toradol) peak

1-2 hrs