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Positioning
Basics exam #4
| Question | Answer |
|---|---|
| What are the goals of positioning | maximize surgical exposure, allow access to pt (maintain ventilation, drugs, monitors), achieve max surgical results to permit rapid return to preop levels |
| What are general ways to prevent nerve injuries | anticipation of potential problems, proper planning and prevention (be familiar with surgical procedures), communicate abnormal findings |
| How do positioning injuries affect hospitalization | prolonged hospital stay and recovery, psychological trauma and permanent disability, patient incurs the cost |
| What is the key to reducing position related injuries | prevention and adherence to standards of care (of CRNA related incidences, 52% found inappropriate standard of care) |
| How do compression injuries occur? | injury to soft tissues, nerves, and vascular structures over an extended period of time. Increases tissue resistance to venous capillary outflow. Decr in the pressure gradient between capillary and tissue |
| Where do stretch injuries occur | occurs with nerves that are superficial and have along course (brachial plexus, saphenous, femoral) |
| How do transection injuries occur | can occur with surgical trauma (IV insertion – median nerve in AC) |
| How does tissue ischemia occur | decr in tissue blood flow, metabolism continues and acid byproducts accumulates in tissue, Na/K pump fails, intracellular Na accumulates creating incr osmotic gradient and edema develops |
| What is compartment syndrome | life threatening complication that causes neural and vascular structure damage d/t swelling into the muscles compartment |
| What are causes of compartment syndrome | prolonged operative procedures, hypotension, elevation of extremities, body habitus, can be precipitated by hypotension with leg elevation |
| What id definitive treatment for compartment syndrome | fasciotomy |
| What occurs with untreated compartment syndrome | progresses to tissue necrosis with myoglobinuria and acute renal failure, permanent neuromuscular damage, amputation, death |
| What are periop contributing factors to compartment syndrome | positioning devices, length of procedure (>4hrs), anesthetic technique, body habitus, preexisting conditions |
| What are periop preexisiting conditions that contribute to compartment syndrome | peripheral neuropathy, PVD, smoking, subclinical ulnar nerve entrapment, thoracic outlet syndrome |
| What is thoracic outlet syndrome | narrowing of pathway for brachial plexus – numbness and tingling when arms are in certain positions |
| Where does the brachial plexus start? | C5-T1 |
| What are body habitus’ that contribute to compartment syndrome | underweight, overweight, muscular (so pretty much everyone?) |
| What anesthetic techniques contribute to compartment syndrome and how | general anesthesia (unconsciousness), NMB (incr mobility of joints), hypotensive techniques (decr perfusion), neuraxial and peripheral blocks (block technique, hematoma, needle trauma) |
| What positioning devices contribute to compartment syndrome | straps, crutch stirrups, arm boards, hard surfaces |
| The most common injured nerves in anesthesia are | ulnar and brachial plexus in upper extreme, common peroneal of the lower extremities |
| What are the levels of thoracic outlet syndrome | weakness of 4th&5th fingers, supraclavicular tenderness, elevation of hands, selmonosky triad |
| From superior to inferior, what are the nerves that branch from the brachial plexus | musculocutaneous nerve, axillary, radial, median, ulnar |
| An interscalene block is done where | in the brachial plexus where the roots exit the vertebrae |
| What is the most difficult nerve to block in the brachial plexus | musculocutenous nerve |
| Describe the surface of the R hand that is innervated by the median nerve | right 2/3 of palm (on supinated hand) and palmer side of 1,2,3 and partial 4th digit, dorsal side of 2,3 and partial 4th digit |
| Describe the surface of the R hand that is innervated by the ulnar nerve | partial 4th and 5th digit and the palm and dorsal hand directly below those digits |
| Describe the surface of the R hand that is innervated by the radial nerve | base of thumb by wrist, and dorsal side of hand directly below 2,3 digit and dorsal side of thumb |
| How can table straps cause injury | lateral femoral cutaneous nerve in thigh can be injured by tight table straps or leg holding devices for arthroscopy |
| What can crutch stirrups injure | injury to common peroneal nerve |
| How can the supine position cause injury | alopecia of the occiput, excessive neck turning strains brachial plexus, back aches d/t abolishment of lumbarsacral curve, crossed legs (pressure injury to superficial peroneal nerve) |
| How can you minimize back aches from supine position | place roll or sheet under the back to minimize pain |
| What are positioning techniques that can be utilized in supine position | heels elevated, gel pads or mattresses, arms tucked to the side or abducted < 90 degrees, hips and knees slightly flexed to incr venous return |
| What are some effects of supine position (CV and pulm) | produces minimal effects on circulation and perfusion of the lungs, FRC decr when changed from sitting to supine, decr skeletal muscle tone in chest wall, expansion of rib cage is not limited, effects offset by mechanical ventilation |
| What are effects of trendelenberg | does not improve CO in hypotension, hypovolemia. Abdominal viscera pushes diaphragm against heart resulting in decr SV, may incr ICP by elevating venous pressure, accentuates compression of lung bases |
| What is a Jackson table | the abdomen hangs free and allows for better diaphragmatic excursion |
| What are effects of prone position | compression of the inferior vena cava and aorta d/t cephlad displacement of the diaphragm |
| What can happen if you turn the head during prone position | turning of head may obstruct jugular venous drainage, not recommended to turn the head with cervical arthritis |
| What can you use to support the head in prone position | prone pillow or Mayfield headrest |
| How do you protect the patient during prone position | protect prominent aspects of face,arms placed on side or on arm board, chest rolls placed under the patient sides from clavicle to iliac crest |
| How do chest rolls work | serve to relieve abdominal pressure and to facilitate venous return |
| What are variations of prone position | knee-chest position (kneeling position, jack-knife position) |
| In the knee-chest position, how do you protect the patient | pad all pressure points (knees and face), free abdominal and chest expansion, limit arm abduction to less than 90 degrees. |
| What is the lateral decubitus position associated with | associated with significant circulatory and ventilation effects during mechanical ventilation, compression of inferior vena cava may occur esp with use of kidney rest |
| What are pulmonary effects of lateral decubitus position | VQ mismatch, dependent lung tends to be under ventilated bc it is compressed by abdominal contents and weight of mediastinum, nondependent lung is over ventilated bc compliance of lung increased. |
| VQ mismatch in lateral decubitus position may manifest as what | arterial hypoxemia |
| What is done to protect patient during lateral decubitus position | axillary roll, check radial artery, pulse ox to assess perfusion to dependent hand, pillow beneath head to prevent stretch injury to brachial plexus, legs flexed, knees bent with pillow btwn, nondependent arm elevated on lateral arm rest |
| High risk of air embolus can occur with what positioning | sitting |
| True sitting position is at what angle | 90 degrees, but modified versions of 45 degrees can be done |
| What are CV effects of sitting position | decr CO, CVP, PAWP, MAP decr 0.75 mmHg per cm elevation |
| Pulm effects of sitting position | less effects on lung volume, beneficial for ventilation |
| What is the most serious complication of the sitting position and how does this happen | venous air embolus – there is a negative pressure gradient btwn the right atrium and veins at the operative site |
| What do you do if VAE occurs | place pt in down lateral tilt to left position (air sits in right atria), flood surgical field and pull out air from central line |
| If pt has hx of lumbar disc disease or hx of lower back pain, what may we ask pt to do before lithotomy position | assume this position while they are awake to see if they can tolerate it |
| What injuries are principle hazards of lithotomy position | injuries to peripheral nerves (sciatic, common peroneal, femoral, saphenous and obturator) |
| What are pulm effects of lithotomy position | effects of ventilation are similar to supine while causes cephlad displacement of diaphragm by abdominal viscera, trendelenberg with lithotomy decreases FRC even further |
| What is the worst position for FRC | lithotomy |
| Blowing up abdomen with air insufflation pressures should be no greater than___ and why? | 15 mmHg (difficulty ventilating) |
| Prolonged lithotomy greater than _____ may result in ______ | >4 hrs- compartment syndrome |
| What can decr injury in lithotomy | proper padding between metal leg braces and pts legs, both legs should be elevated and lowered at the same time to avoid stretching of the peripheral nerves and minimize effects on decr venous return |
| Thigh in lithotomy should be flexed no more than ___ degrees before rotating the stirrups laterally | 90 degrees |
| _____are a significant source of anesthesia related liability claims | peripheral nerve injuries |
| Peripheral nerve injuries are more likely to occur | during general anesthesia |
| Postop neuropathy occurs as a result of | position-related compression or stretch of the involved nerve. |
| Acute nerve injury will appear ______ after the onset of symptoms | 18-21 days |
| What to do when peripheral nerve injury occurs | neurology consult, performance of nerve conduction velocity and EMG studies to decide of there already was preexisiting injury (test both extremities) |
| Recovery from peripheral nerve injuries can take | 3-12 months, some irreversible |
| Both extremities injured? | usually not r/t positioning |
| What is the most common postop neuropathy | ulnar nerve injury |
| What is the incidence of ulnar nerve injury | 0.04-0.5% of cases |
| What is prevalence of ulnar nerve injury after cardiac surgery | 38% |
| Describe the path of the ulnar nerve | passes along the anterior aspect of the medial head of the tricep muscle, and posterior into the groove of the epicondyle of the humorous and the olecranon |
| What position of the forearms increases risk of injury | pronation of the forearms (palms down) |
| How should arms be positioned to decr risk of ulnar nerve injury | rest on arm boards at less than 90 degree abduction, forearms supinated and padded (palsm up) |
| Clasping hands on the abdomen causes | supination of the hands and rotating the humorous |
| Bending the elbow can | narrow the cubital tunnel and compress the ulnar nerve |
| Injury to the ulnar nerve can manifest itself as | CLAW HAND-inability to abduct or oppose the 5th finger, diminished sensation over medial one and a half fingers and atrophy of intrinsic muscles of hand |
| What is the second most common injury of the upper extremity | brachial plexus |
| The brachial plexus is susceptible to stretch and compression injury because | its long superficial course in the axilla, proximity to freely moveable body structures (clavical and humerus) |
| How can stretch injuries occur to the brachial plexus | occur when the neck is extended, the head is turned in the opposite side, or the arms are abducted > 90 degrees |
| How can compression injuries occur to the brachial plexus | may occur btwn clavicle and first rib when shoulder braces are not placed over the acromioclavicular joint (should not be by neck) |
| What position are brachial plexus injuries most common and why | lateral decub – d/t arm abduction greater than 90 degrees, excessive stretch, lateral flexion of head, posterior shoulder displacement |
| What is stingers/burners syndrome | injury to brachial plexus – burning sensation that radiates along arm – may last several weeks |
| How can sternal retractors cause injury | causes clavicle to move posteriorly and first rib to move upward pinching the brachial plexus – stinger/burners syndrome |
| What are ways to prevent brachial plexus injuries | avoid excessive and prolonged retraction and chest asymmetry during cardiac surg, abd of arms < 90 deg, prone patient arms overhead bent at elbow and abducted < 90 deg, head and neck in alignment with body, axillary roll under dependent side of thorax |
| What can cause radial nerve injury | if arm slips off side of OR table and pressure is applied to nerve as it transverses the spiral groove of humerus, pressure exerted from the distal edge of the BP cuff on radial nerve |
| Symptoms of radial nerve injury | wrist drop, weakness of abduction of thumb, decr sensation over dorsal surface of lateral three and ½ fingers |
| Where is the median nerve located | along the anticubital fossa |
| How do median nerve injuries usually occur | result of IV placement or by extravasation of drugs (thiopental) |
| Describe a median nerve injury | APE HAND DEFORMITY-opposition and flexion of thumb are lost. Thumb and index finger arrested in adduction and hyperextension, decr sensation on palmar surface of lateral 3 ½ fingers |
| What is the longest and widest single nerve of the human body | sciatic nerve |
| How can the sciatic nerve become injured | compression may occur as the nerve passes under piriformis muscle. Stretch injury since the distance btwn the points of fixation of nerve (sciatic notch & fibula) is incr by external rotation of the leg or extension of the knee. Lithotomy. IM injections |
| Braches of the sciatic nerve are | tibial and common peroneal |
| To prevent sciatic nerve injury, where should IM injections be administered | lateral aspect of the thigh |
| To minimize injury to sciatic nerve in lithotomy position, how should the patient be positioned | to minimize stretch the patient should be positioned such that external rotation of the legs is minimal and knees should be flexed. |
| How is sciatic nerve injury manifested | weakness of all skeletal muscles below the knee and diminished sensation over the lateral half of the leg and almost all of the foot |
| What is the most frequently damaged nerve in the lower extremities | common peroneal nerve (branch of sciatic nerve) |
| How can the common peroneal nerve become injured | compression of the nerve between the head of the fibula and metal brace used in lithotomy position. (nerve runs along side of knee) |
| How does common peroneal nerve manifest | foot drop, loss of dorsal extension of toes and inability to evert the foot |
| How can you prevent common peroneal nerve injury | proper padding decr likelihood |
| How does anterior tibial nerve injury manifest | foot drop post op if feet are plantar flexed for extended periods during anesthesia |
| How can you prevent anterior tibial nerve injury | foot drop is prevented by pts in sitting position should have a roll placed under the anterior aspect of the ankle to maintain the extended position. |
| How can the femoral nerve become injured | compressed at the pelvic brim by the blade of a self-retaining retractor as used during laparotomy or by excessive angulation of the thigh when patient is placed in lithotomy |
| What are symptoms of femoral nerve injury | decr in knee jerk and loss of flexion of hip and extension of the knee as a result of quadriceps femoris injury, sensation is absent/decr over superior aspect of thigh, medial and anterior medial side of leg |
| The saphenous nerve is a branch of the ____ | femoral nerve |
| How can damage occur to saphenous nerve | compression against the medial tibial condyle if the foot is suspended lateral to a vertical brace. |
| How does saphenous nerve injury manifest | medial knee and leg pain with prolonged walking and standing |
| How does obturator nerve injury manifest | inability to adduct the legs and decreased sensation over the medial side of the thigh. |
| How does obturator nerve injury occur | during difficult forceps delivery or excessive flexion of the thigh to the groin |
| What are examples of non neural injuries | skin, eyes, appendages |
| How can skin injuries occur | excessive pressure = ischemia and localization ulcers, ulceration of skin at corner of mouth d/t ETT, pressure necrosis of groin with positioning on OR table for hip surgery (chick table) |
| What is the incidence of postop visual loss | 0.0008-0.02% |
| Higher risk surgeries for postop visual loss is | cardiac surgery and prone spine surgery |
| The retina contains | cell bodies that supply axons to the optic nerve and brain |
| The optic nerve extends from the ____ to the _____ and is divided into what 4 sections | globe to the optic chiasm, divided into intraocular, intraorbital, intracannilicular, intracranial |
| The retina and optic nerve’s blood supply is through | central retinal artery and long and short posterior ciliary arteries that arise from the internal carotid. |
| Why are arteries that supply blood to eye at incr risk for causing post op vision loss – who is at incr risk | these arteries lack auto-regulation in event of hypoperfusion, diabetes and HTN make these patients more susceptible |
| Conditions that place patients at risk for postop vision loss | pressure on eyes: head rest in prone position can cause thrombosis of central retinal artery, hypotension, incr intraocular pressure |
| How can appedages become damaged | fingers and toes from surgical table, fingers when foot of adjustable table is returned to horizontal position from lithotomy, ears if folded btwn head and mattress of OR table |
| Damage r/t mask: | face mask straps (hair loss to outer 1/3 of eyebrow that wont grow back), pressure on buccal branch of facial nerve (parasthesia of orbicularis oris muscle-whistle, kiss), necrosis of bridge of nose, compression of suborbital nerve from ETT, facial nerve |
| Compression of suborbital nerve from ETT manifests as what | decr sensation over the forehead and pain in eye |
| How does facial nerve damage occur from mask | compression of fingers with the ascending ramus of the patients mandible |
Created by:
rwilson