Week 14 - Nagelhout C. 23 high yields Flashcards
What is the goal of positioning for anesthesia and surgery?
Optimize surgical access while minimizing risk to the patient.
What are the risks of surgical positioning?
Every position has inherent risks, especially under anesthesia.
How does general anesthesia affect the cardiovascular system?
Decreases cardiac output and blood pressure due to myocardial depression and vasodilation.
What are the hemodynamic effects of the prone position?
↑ CVP, ↓ left ventricular volume, possible ↓ CI depending on frame.
What is the hemodynamic risk in the sitting position?
↓ CO by 20% at 90° due to pooling in extremities.
What are the attenuation methods for hemodynamic changes?
Slow positioning, light anesthesia (<0.5 MAC), volume loading, gradual anesthetic deepening.
What is the cardiovascular effect of the Trendelenburg position?
↑ CVP and PAP, but variable effect on MAP and CI; may mask hypovolemia.
What are the risks of combining Trendelenburg and lithotomy positions?
Apparent normal MAP despite hypovolemia; risk of lower extremity ischemia in PVD patients.
What are the risks associated with the head-down position?
Facial, pharyngeal, and orbital swelling; ↑ ICP; POVL risk due to ↓ ocular perfusion pressure.
What is the respiratory risk in the Trendelenburg position?
↓ FRC due to cephalad diaphragm displacement; risk of right mainstem intubation.
What is the respiratory benefit of the prone position?
Improved V/Q matching; posterior lung better ventilated; FRC may increase if abdomen hangs free.
What causes V/Q mismatch in the lateral decubitus position?
Positive pressure ventilation favors nondependent lung ventilation; dependent lung perfused more.
What is the respiratory effect of lithotomy position?
Minimal in healthy patients, but extreme flexion compresses abdomen and ↓ compliance.
What is the respiratory advantage of the sitting position?
↑ FRC, better diaphragmatic movement; rib cage contributes more to ventilation.
What are the primary nerve injury mechanisms?
Transection, compression, stretch.
What causes common peroneal nerve injury?
Compression against table in lateral position or stirrups in lithotomy.
What are the risk factors for ulnar nerve injury?
Male gender, elbow flexion >90°, pronation, prolonged hospitalization, extremes of body habitus.
What positions are at risk for brachial plexus injury?
Supine >90° arm abduction, Trendelenburg, prone overhead arm extension, lateral arm rotation.
What position risks sciatic nerve stretch injury?
Lithotomy with hip flexion >90°.
What are the risk factors for compartment syndrome?
Lithotomy >2-3 hours, Trendelenburg, hypotension, leg elevation.
What are the major causes of POVL?
ION (anterior/posterior), CRAO; often related to prone position and long surgeries.
What are the risk factors for ION?
Male, obesity, surgery >5 hrs, anemia, blood loss, hypotension.
What causes CRAO?
External eye pressure, improper head positioning.
What position is at risk for venous air embolism (VAE)?
Sitting position; occurs with negative pressure gradient between heart and veins.
What are the detection methods for VAE?
TEE (most sensitive), precordial Doppler, ETCO₂ ↓, mill-wheel murmur.
What are the methods for preventing perioperative neuropathy?
Proper padding, neutral positioning, avoid arm abduction >90°, supinate forearms.
What are the ASA recommendations for arm position?
Supine: abduct <90°, forearm supinated/neutral. Lateral: pad axilla, monitor perfusion.
What is the risk of arm injury in Trendelenburg position?
Shoulder braces can compress brachial plexus; should be placed over distal clavicle.
What should be considered for the abdomen in the prone position?
Abdomen should hang freely to reduce venous pressure and bleeding risk.
What is the airway complication risk in Trendelenburg position?
Risk of right mainstem intubation due to diaphragm displacement.
Why is anesthesia documentation important?
Accurate records support quality care and legal protection in case of complications.
What are the considerations for the supine position?
Head neutral, arms tucked or on padded armboards <90°, uncrossed legs, heels elevated, pillow under knees.
What are the nerve injury risks associated with the supine position?
Ulnar and brachial plexus injuries from poor arm positioning or padding.
What are the benefits of the Trendelenburg position?
Increases venous return for hypotension and improves surgical exposure.
What complications can arise from the Trendelenburg position?
Increased intracranial pressure (ICP), facial/oropharyngeal edema, risk of brachial plexus injury from shoulder braces.
What is a safety tip for the Trendelenburg position?
Avoid shoulder braces if arms are on armboards; brace over acromioclavicular joint.
What is a consideration for the reverse Trendelenburg position?
Risk of hypoperfusion to the brain; monitor cerebral perfusion.
What is the lithotomy position used for?
Perineal surgeries; legs flexed and elevated in stirrups.
What is the safety rule for raising/lowering legs in the lithotomy position?
Raise/lower legs simultaneously to prevent spinal torsion and hip dislocation.
What are the nerve injury risks in the lithotomy position?
Peroneal, saphenous, femoral, obturator, and sciatic nerves.
What is the hemilithotomy position?
One leg elevated; arm on that side may be crossed over chest—watch for crush injury.
What is the prone position used for?
Spine, rectal, and some orthopedic surgeries.
What are the key considerations for prone positioning?
Abdomen hangs free; arms flexed <90°, neck in neutral, eyes protected from pressure.
What is a risk associated with the prone position?
Postoperative visual loss (POVL) from venous congestion, increased intraocular pressure, airway edema.
What is the sitting position used for?
Neurosurgery, shoulder surgery; excellent exposure and venous drainage.
What complications can arise from the sitting position?
Venous air embolism (VAE), hypotension, paradoxic air embolism (PAE) in patients with PFO, airway edema from neck flexion.
What is lateral decubitus positioning used for?
Thoracic, kidney, and some orthopedic procedures.
What are the safety measures for lateral arm & leg positioning?
Dependent arm on padded board, axillary roll caudad to axilla, pillow between legs.
What are the three primary nerve injury mechanisms?
Transection, compression, stretch.
What are the symptoms of ulnar neuropathy?
Inability to oppose 5th finger, sensory loss in 4th/5th fingers, claw hand if prolonged.
How can ulnar nerve injury be prevented?
Supinate/neutral forearm, avoid elbow flexion >90°, pad elbows.
What are the risks for brachial plexus injury?
Arm abduction >90°, head rotation, shoulder depression, falling arms.
What is a common cause of peroneal nerve injury?
Compression at fibular head by stirrups or table.
What is the risk of sciatic nerve injury?
Lithotomy position with extreme hip flexion.
What is the risk associated with suprascapular nerve injury?
Lateral position with shoulder roll without stabilization.
What is the risk for radial/circumflex nerve injury?
Arm pressed against hard surface or vertical post.
What is the risk of femoral nerve injury?
Extreme hip flexion (lithotomy) compresses under inguinal ligament.
What causes posterior tibial/saphenous/pudendal nerve injury?
Leg holders or perineal post compression.
What causes peripheral nerve ischemia?
Stretch, compression, or capillary perfusion compromise from pressure.
What effect does stretch injury have on nerves?
May disrupt axons or blood supply, causing conduction block or infarction.
What is POVL?
Postoperative visual loss; visual defects up to total blindness.
What are the top two causes of POVL?
Ischemic optic neuropathy (ION) and central retinal artery occlusion (CRAO).
What are the risk factors for ION?
Male, obesity, long surgery (>5 hrs), anemia, hypotension, Wilson frame, diabetes.
What is the main cause of CRAO?
External pressure on the eye due to poor head positioning.
What are the prevention strategies for POVL?
Neutral head, avoid face pressure, monitor hematocrit/blood pressure, inform high-risk patients.
What positions carry a risk of airway edema?
Prone, Trendelenburg, sitting (with excessive neck flexion).
What causes macroglossia in the sitting position?
Jugular venous obstruction due to head flexion.
What positions increase the risk of right mainstem intubation?
Trendelenburg or neck flexion.
What is a risk factor for compartment syndrome?
Lithotomy >2–3 hrs, leg elevation, hypotension, tight compartments.
What are the signs of compartment syndrome?
Increased pressures, ischemia, muscle/nerve infarction, risk of renal failure.
What position is associated with VAE risk?
Sitting; air enters venous system due to pressure gradient.
What are the detection tools for VAE?
Transesophageal echocardiography (TEE) (most sensitive), precordial Doppler, end-tidal CO₂ decrease, mill-wheel murmur.
What is PAE?
Paradoxic air embolism; risk in patients with PFO; air enters systemic circulation under pressure shift.
What is the maximum safe arm abduction in the supine position according to ASA?
<90°; prone may tolerate >90° with support.
What should be documented in positioning?
Record all actions for quality improvement and legal support.
What are the key ASA upper extremity tips?
Supinate forearm, neutral elbow, avoid elbow flexion when tucked.
What are the key ASA lower extremity tips?
Avoid fibular head pressure, assess hip/knee flexion, pad pressure points.
What are the key areas of litigation according to CRNA/AANA claims insight?
Nerve injuries, brain injury, and POVL.
What is the top nerve injury in closed-claims?
Ulnar (28%), brachial plexus (20%), spinal cord (13%).
What is the trend over time for ulnar nerve injury claims?
Decreasing; spinal cord injury claims are increasing.
What percentage of quality of care judgments (ASA) were deemed appropriate in spinal cord damage cases?
Only 46%.
What is the preventive theme across guidelines?
Meticulous positioning, padding, and monitoring.
