Positioning Flashcards
OR table weight limit and length
136 kg (300 lbs), 270 kg on the newer tables, Length: 80.7 inches or 6'5
What is the most common operative position?
Supine; easy access to airway, arms for IV monitoring, less physiological changes than other positions
Supine positioning
tuck arms, use arm boards, draw sheet under the hip or torso, not the mattress, elbow pads, plasm supinated, UP. NOT PRONATED; lumbar support, slight flexion of hip and knees, safety strap
What are the 5 mechanisms of nerve injury?
Stretching, compression, kinking, ischemia, transection (stretching is most common, next compression)
Brachial plexus injury occurs in supine position when?
neck extended or turned to the side, excessive abduction of arm >90 degrees, arm falls off table. s/s would be shocks, numbness/weak arm
Radial nerve injury in supine position?
Radial nerve- due to external compression against humerus, surgical retractors, ether screen, mismatched arm board, repeated inflation
injury results in wrist drop/ weakness of abduction of thumb, and numbness of 1 and 2 ring fingers, inability to extend elbow.
Ulnar nerve injury in supine position?
*most common peripheral nerve injury
Compression in elbow groove between ulna and medial epicondyle of humerus. Stretched by elbow flexion, dislocation with pronated hand, compression against bed. More common in men (3x). Injury= CLAW HAND (cannot abduct or oppose 5gh finger, loss of sensation in 4th or 5th fingers, atrophy)
Cardiovascular changes with supine position?
Minimal effect on circulation and perfusion
Initial increase in return to heart, increased preload, SV, CO, BP. Baroreceptors activated which decrease sympathetic outflow= decreased HR, PVR. Beware of IVC masses.
Ventilatory changes with supine?
FRC decreases 800 ml d/t cephalad dispalcement of diaphragm. Lung volumes reduced by muscle relaxants reduces opposition to inherent elastic recoil of pulmonary tissues, overcome with PPV.
Supine cerebral blood flow changes?
Minimal due to tight autoregulation
Trendelenberg procedures
Laproscopy, GYN, abdominal, helps prevent air embolism, used during central line insertion; use braces and pads over arcomiocalvicular joint
Trendelenberg cardiovascular changes
Increases up to 1L venous return to heart. Reduced BF to LE. Compression of heart from abd contents, baroreceptors activated, makes shock syndromes worse in the long run.
Trendelenberg ventilatory changes
Compresses lung bases, decreases lung compliance, decreases FRC, PIP increases; V:Q mismatch, in apex: perfusion>ventilation; aspiration, ETT shifts to R mainstem, face/airway edema
Trendeleberg CBF
Increases intracranial vascular congestion due to gravity. Increases ICP. Intraoccular pressure increases.
Reverse Trendeleberg
Used to enhance exposure of upper abdomen, laparoscopic cholecystectomy, ENT surgeries; variation of sitting position; use footboard: excessive plantar flexion can cause anterior tibial injury= FOOT DROP
Reverse Trendelenburg Cardiovascular changes
Reduced preload, reduced C.O (20-40%), lowered BP, compensatory increased SNS tone, SVR, HR changes 30%. Activates RAS system, venous pooling in lower extremities, use stockings
Reverse Trendelenberg ventilatory changes
Abdomen does not impede diaphragm, FRC increases, ventilation is easier
Reverse Trendelenberg CBF
CBF decreases proportional to the degree of head up tilt (can be up to 20%), ICP decreases. Know the blood pressure at the circle of willis (move transducer up)
Describe the lithotomy position
Stirrups, hips flexed 80-100 degrees, legs abducted 30-45 degrees from midline, lower legs parallel to torso, watch femoral, sciatic, lower leg nerves (saphenous, common perineal especially)
Hip flexion beyond 110 degrees avoided.
Lithotomy position knee crutch style
Lithotomy position candy can stirrups
- Watch the popliteal nerve (tibial and common peronal nerve); also arms can fall off.
- Common peronal nerve injury*, sciatic, more acute flexion of the knees and hips
Lithotomy lower extremity nerve injury percentages
1: 3608 patients 78% common peroneal 15% sciatic 7% femoral Most common with low body mass index, prolonged surgery, recent cigarette smoking, PVD, DM, obesity
What procedures is the lithotomy position used for? And what nerves can be damaged?
GYN, GU, Rectal
Femoral, sciatic, obturator, lateral femoral cutaneous, saphenous, COMMON PERONEAL (compression of lateral aspect of knee against stirrup or lateral position) symptoms are foot drop, inability to evert the foot, loss of dorsal extension of toes
Scatic nerve injury symptions?
Excessive external rotation of hips, pressure in sciatic notch from stretching, weakness or paralysis of muscles below knee, numbness in foot or lateral half of calf; foot drop
Femoral nerve injury symptoms?
Compression at pelvic bring by retractor or excessive angulation of thighs and external rotation of hips, results in loss of flexion of hip and extension of knee; decreases sensation over superior aspect of thigh.
Saphenous nerve injury symptoms?
Occurs when medial aspect of lower leg compressed against support bar; paresthesias medial and anterior side of calf
Lower extremity compartment syndrome
Occurs when perfusion to an extremity is inadequate, resulting in ischemia, edema, extensive rhabdomyolysis from increased tissue pressure, occurs with long surgical procedures (>2-3 hours); occurs with lithotomy and lateral decubitus positions
Lithotomy cardiovascular changes?
increases VR; increased preload with transient increase in CO and increase in Bp; perfusion to LE is reduced:
2 mmhg change for each 2.5 cm above or below heart
Lithotomy ventilatory changes?
Depending on the degree of hip flexion, abdominal contents may be pushed up on the diaphragm and impede excursion, reduces lung compliance, TV and VC; aspiration risk
Lithotomy cerebral changes
Transient increase in cerebral venous blood flow and increase in intracranial pressure with legs elevated
Prone positioning procedures?
achilles, hemhorroid; back, cervical
What types of beds are used for prone?
Wilson frame, Jackson table
horseshoe head rest, or with mirror; mayfield head tongs/pins (for back/cervical)
Prone position
Head may be turned to side if adequate mobility, weight on bony structures, neck in neutral alignment, no pressure on eyes, breasts, genitals.
Prone position eye injuries:
corneal abrasions, blindness (central vein or artery obstruction, sustained pressure on eye/retina)
Blindness risk factors: prone, operative hypotension, blood loss, crystalloid use excessively, anemia, smoker, diabetic, patient with HTN, male
Prone position injuries?
Thoracic outlet syndrom: bundle of IJ, EJ and lymph come right under clavicle. Raise arm for 2 mins and check for decreased pulse ox or decreases pulse. Esp on left side.
Prone position cardiovascular changes
IVC and aortic compression: hypotension! (use rolls)
Venous pooling in LE: hypotension! (use SCDs or stockings)
*HYPOTENSION! anticipate and give fluids
Prone position ventilatory changes
V:Q mismatch:
anterior perfusion> ventilation
Posterior ventilation>perfusion
Cephalad displacement of diaphragm, lung compliance decreases, PIP increases, WOB increases. = use rolls/bolsters to free chest. PPV overcomes effects
Prone position CBF
turning head obstructs venous drainage leading to increased cerebral volume and ICP; excessive flexion or turning obstructs vertebral artery flow
Lateral decubitus position procedures
thoracotomy, kidney, shoulder, hip
Lateral decubitus position
Keep head supported and neutral; use axillary roll; pad between knees, flex dependent leg (saphenous nerve injury)
Anterior/posterior support, bean bag, safety strap between head of femur and illiac crests
Lateral positioning cardiovascular changes
minimal change, no change in CO unless VR is obstructed (kidney rests against vena cava),
noninvasive BP will be different in each arm.
Lateral position ventilatory changes
Awake and spontaneous breathing: Dependent lung is better perfused and ventilated, but FRC, VC, TV decrease
Anesthetized and spontaneously breathing: nondependent lung better ventilated and dependent lung better perfused (VQ mismatch)
anesthetized, mechanically ventilated: nondependent lung is overventilated and dependent lung is overperfused (worse VQ mismatch)
Lateral position CBF:
Minimal change unless extreme flexion of head
Sitting position
uses mayfield tongs to keep head in placed, used for cranial surgery, shoulder, humeral procedures, facilitates venous drainage, excellent surgical exposure/access; avoid excessive cervical flexion, want 3 FB between mandible and sternum, avoid rigid bite block for tongue ischemia; flex knees and hips to avoid sciatic injury, SCD
Sitting position cardiovascular changes
Pooling of blood into lower extremities decreases preload, CO and BP, HYPOTENSION; HR and SVR increase as a compensatory measure, treat with IVF, vasopressors, adjust anesthetic depth, stockings, SCD
Sitting position ventilatory changes
Lung volumes increase, WOB is easier, easeri to mechanically ventilate
Sitting position CBF
Gravity, CBF decreases, ICP decreases; check BP at circle of willis
Venous air embolism
VAE: at risk during anytime where surgical site is above the level of the heart, inability of venous sinuses to collapse, lethal complication. S/S: change in heart tones (wind mill murmur) heart at parasternal border (2-6 IC space), dysrhythmias, hypotension, denaturation, decreased EtCO2. Nitrogen in exhaled gas, tachycardia. Find with TEE or precordial doppler to hear the air entrained.
Treatment of VAE
Flood surgical field with NS, apply wax to cut bony edges, close any open vessels, D/C nitrous oxide, place on 100% Fio2, peep, Trendelenberg, aspirate air from R artium via catheter.