posterior fossa, somer cervical, shoulder arthroplasty, arthroscopy mayfield pins used with neurosurgery, horseshoe variation type headrest used

amount and rapidity of entrance into systemic circulation

venous air embolism

FRC decrease mediastinum movement toward head can increase risk of right mainstem intubation

trendelenburg

sitting

robotics- prostatectomies, colorectal, gynecologic

male anemia from blood loss > 1 liter surgery > 5 hours DM HTN vascular disease smoking intraop hypotension Wilson frame bed

trendelenburg

peroneal

bariatric paraesopheageal hernia

increased dependent blood pooling decrease BP from decreased volume return

standard lateral- minimal change kidney rest- hypotension with dependent lower extremities and impaired venous return and can cause direct compression of great vessels

LFC lateral femoral cutaneous

standard, jacknife, kidney rest thoracic and kidney surges when supine isn’t good enough ortho for hips, shoulders, extremities

lithotomy

less common cause of POVL than ION decrease blood supply to entire retina- one of first branches of internal carotid most common cause is improper head positioning causing direct pressure to eye

ventilation favorable more torso elevated, less trespass on compliance

trendelenburg

for retropubic access pelvis flexed onto spine thighs flexed almost onto the trunk significant perfusion gradient, lumbar spine stress compartment syndrome risk

footboard to prevent sliding off table - placed at beginning of case hypotension- small changes in posotion, IVF bolus to combat if NPO, pressers on standby

trendelenburg

variation of supine or lithotomy position arms tucked or abducted

neurosurgical, butt

ISCHEMIC OPTIC NEUROPAHTY CENTRAL RETINAL ARTERY OCCLUSION central retinal vein occlusion cortical blindness glycine toxicity

tucked or on arm boards

balance angle of torso with flexion of legs opt for semi-recumbent when possible ensure neck is neutral support BP check position of head and ETT frequently - ETT take away form operative side

exaggerated lithotomy

HTN CAD high BMI open angle glaucoma sickle cell anemia

increase repsoiratory compliance lower peak pressures

check eyes, eyes, genitals frequently padding c spine natural ensure downward tissue is compression free limit trendelenburg shoulders under 90 when flexed

hypotension - specially in brain - bezold jarisch reflex venous air embolism pneumocephalus cervical spine injury- tretraplegia from hyper flex ion at C5= paralysis sciatic nerve injury- foot drop braical plexus injury facial Edema from prolonged neck flexion accidental exhumation

conjunctival edema POVL neck injury from lateral rotation and impair cerebral blood flow brachial plexus - extra padding breasts- ischemia from direct pressure, lateral displacement - stretch abdominal compression- diaphragm forced on cephalad and impair Resp increased pressure impairs lower venous return genital- penis and scrotum

maintained or transient increase of BP secondary to auto transfusion strand are decrease in FRC from supine positionsing may be exaggerated

neck injury from sliding down fall off table brachial plexus by taping and position devices (tape lateral aspect of acromioclavicular joints to improve safety) ventilation difficulty hypoperfusion compartment syndrome cranial vascular congestion and increase ICP (visual changes, facial edema)

FRC and total lung capacity are lowered compared to standing increase pressure of abdominal viscera

C spine mobility shoulder, hip, knee mobility pre-existing paresthesias comorbidities that would make them more susceptible to injury

risk increases with higher levels perfusion gradient puts lower extremities at risk for compartment syndrome and ischemia thigh flex ion over 90 degrees= sciatic and obdurator nerve stretch and direct compresssion of neruovascular structures under inguinal ligament lower extremity nerves: peroneal and saphenous arms tucked: fingers at risk when foot is lowered

peroneal most common then saphenous

compress major vessels stretch inguinal ligament impinge lateral femoral cutaneous nerves

trendelenburg

use least degree of change possible slow, incremental movements check positioning frequently, mark bed with tape to check for sliding Pressure control ventilation and larger ETT to promote laminar flow

may increase BP from auto transfusion increased myocardial work from increased central blood volume patient with CAD- increased CVP/PAP may result in decrease CO

reverse trendelenburg

lateral decubitus

gel pads Wilson frame prone-view

limit gas exchange in pulmonary vascuature hypotension, arrhythmias, cardiac arrest

reverse trendelenburg

peroneal

injury to dependent eye and ear cerviacl injury or pain if c-pine is not aligned peroneal nerve injury of dependent leg braichal nerve injury of dependent arm rhabdo with long surgery time, hypotension, pressure of OR table to flank

decrease IOP promote optic nerve perfusion - prevent hypotension ocular perfusion pressure: MAP-IOP= OPP ION can still occur in patients in mayfield pins and without risk factors

anesthetic technique - pts under GA can’t move when uncomfortable high BMI- force and pressure low BMI- less adipose at bony area high muscle- increase risk compartment syndrome comorbiities: htn, PVD, dm, smoking, neuropathies, ETOH

supine lateral displacement of head increased risk if wrist secured to bed

2mmHG

POVL compartment syndrome rhabo ARF

patient positions self assess ability to fully relax elbow assess arm board and shoulders (if tucked, elbows padded and palms facing thighs) pillow under knees for back support padding under occiput, heels, sacrum secure bed straps without compromising circulation strap should be above knee and below hip rotate BP cuff site

raise and lower legs at same time (avoids hip dislocation, spinal torsion) keep hip flex ion less than 90 degree do not allow excessive coughing > obturator damage

CO decreases 20% when torso is 90 degrees due to venous pooling MAP decreases 2mmHG per inch when comparing site of measurement to body part (think BRAIN)

ischemia to portion of optic nerve central retinal and posterior ciliary arteries are at distal most branches and considered watershed regions extremely sensitive to disruption in blood flow (auto regulation still occurs) anterior ION: anterior to lamina cribrosa posterior ION: posterity to lamina cribosa

abrupt drop in ETCO2 mill-wheel murmur increase PAP hypoxia

ULNAR NERUOPATHY brachial plexus neuropathy - lateral displacement of head and increased risk when wrist is secured to bed axillary trauma - over 90 degree arm abduction = places axillary Neuro vascular bundle on the extension side of the shoulder joint- nerve bundle gets compressed radial nerve compression median nerve dysfunction lumbar pain and paraplegia

high BMI, open angle glaucoma , sickle cell anemia , CAD

tucked or abducted and secured on cushion arm rest, less than 90 degrees

patient supine, thighs flexed 90 degrees lower legs parallel to floor

thigh flex ion 30-45% access to abdomen and perineum

dependent leg(bottom)= bent for stabilization superior leg = straight pillow between legs to protect peroneal nerve dependent arm flexed on arm board (less than 90 degreee) superior arm on pillows or in holding device AXILLARY roll if kidney rest used: should be positioned under depends iliac crest

positional change of west zones dependent lung promotes perfusion, superior lung promotes ventilation need for increased PEEP may implant right atrial filling and vous return

placement of nerve stimulator and IC access

thighs flexed 90 degrees or more legs hung from high poles significant uphill gradient for arterial perfusion - avoid hypotension

sciatic and obturator nerve

less respiratory trespass than supine no midiastinal structures compressing with allows expansion of lungs posteriorly

brachial plexus

lateral decubitus

any position where the torso is elevated from supine and higher than legs modified: trunk at 45 angle with legs elevated an flexed

lateral decubitus

degree of elevation above operative side

supine

supine

sitting

major abdominal tumor pregnancy

reverse trendelenburg

minimal change depending on use of frame if head is lower than heart, increase venous congestion to face

MI CVA

male high BMI prolonged postoperative bed rest

slide off table profound hypotension

supine over 90 degree arm abduction axillary Neuro vascular bundle compressed and stretches

brachial plexus or ulnar

TEE