Module 2 Flashcards
Postural changes may alter lung volumes, ventilation, and pulmonary blood flow
Redistribution of V/Q (Ventilation/perfusion)
Worsened by the majority of surgical positions
Anesthetic respiratory depression
Dependent lung (bottom) is better perfused, while independent lung (top) is better ventilated
V/Q mismatching
FRC (functional residual capacity) and TLC (total lung capacity) are decreased in this position
Supine position
Improved oxygenation, improved V/Q mismatching, and ventilation is more uniformed because abdominal organs are not pushing down on lungs in this position (commonly used to treat ARDS)
Prone Position
This position alters V/Q mismatching and can impact oxygenation
Lateral Position
This position limits diaphragmatic movement because all abdominal organs are pushing down on diaphragm and lungs causing a decreased FRC
Lithotomy Position
Nerve transection that occurs as a result of surgical maneuver or traumatic injury; Cutting the nerve.
Transection Nerve injury
What injury occurs when a nerve is forced against a bony prominence or hard surface such as an arm board or OR table
Compression Nerve Injury
Most common compressed nerve
Ulnar Nerve
What injury can cause excessive elongation of a nerve may cause conduction changes, axonal disruption, or interruption of vascular supply
Stretching/ Traction nerve injury
Muscle relaxants may contribute to this injury by allowing increase mobility of joints
Stretching/ Traction nerve injury
Most commonly affects the brachial plexus nerve
Stretching/ Traction nerve injury
This nerve root (C8-T1) injury is the second most common post op injury; most vulnerable to injury if the arm is abducted, arm board falls off, the head is rotated away from arm, and if shoulder straps are used in steep Trendelenburg because it causes stretching and compression
Brachial Plexus
Abduct arms less than 90 degrees, avoid shoulder compression, and keep head midline
To avoid stretching injury
When a peripheral nerve is pinched between two immovable structures
Kinking
Blood flow that can be interrupted by stretch, compression or transection injury
Nerve Injury
Common component of all peripheral nerve injury
Ischemia
Form of preventing injuries
Ensure PPP (pressure points padded)
Most frequently reported injury after surgery; patient will have “claw hand” and loss of abduction/adduction of fingers
Ulnar neuropathy
Use padding, place arms in supinated position (palms up), and abduct arms less than 90 degrees. Or patient’s arms tucked at side of the body in neutral position with palms facing inward. Pronation (palms down) increases pressure on ulnar nerve
Prevention of Ulnar neuropathy
Compresses neural and vascular structures and may cause compartment syndrome
Improper placement of axilla roll
Nerve injury that can occur when legs are improperly placed in candy cane stirrups
Peroneal nerve injury
Contribute to postoperative positioning complications; weight of body causes external compression of dependent tissue and states of low perfusion
Prolonged surgical procedures
Under which anesthetic technique is the patient unable to respond to painful stimuli generated by uncomfortable body positions
General Anesthesia
The brachial plexus consist of what nerve roots?
Primary C8 – T1
Name anatomical location of the brachial plexus and what happens with brachial plexus injury?
Fixed first rib, clavicle and humerus,compression of nerves between these locations
Precautions that help prevent brachial plexus injury include
Arm abduction <90o
Avoid shoulder braces
Maintain head midline
In the lateral decubitus position, injury to the brachial plexus is most commonly the result of
Excessive stretching
Causes of brachial plexus excessive stretching include
Abduction >90o
External rotation
Extension and lateral flexion of the head
Posterior shoulder displacement
What positioning device can relieve pressure of the brachial plexus
Axillary roll
To prevent brachial plexus injury during cardiac surgical procedures
what is the placement of sternal retractor and avoidance measures
Placement of sternal retractor is Caudad
Avoidance of prolonged asymmetric chest wall retraction.
The supine position is also called
Dorsal Decubitus
What position would you put the patient for surgery of abdomen, head, neck, extremities
Supine
How should the head be positioned
Neutral position, with small pillow or donut
If a patient has severe arthritis, neuropathy, and ↓ mobility of head or neck. How should Pt be positioned
To his or her preference prior to induction of anesthesia
When using an arm board it is important to use padding and place hands in what position
Supinated
Post op back pain is caused by
The relaxation of ligaments of the vertebral column, use pillow under knees to provide comfort
Utilize beach chair position
During prolonged surgery what should you do to the head
Reposition and massage occiput to prevent alopecia.
Crossing the legs during surgery can cause injury to
Superior peroneal nerve –dependent extremity
Sural nerve – superior extremity
Where is the head in trendelenberg
Head down position
Where is the head in reverse trendelenberg
Head up position
Trendelenberg position is used to increase what cardiovascular effect
venous return
This position is used to supplement the primary surgical position and improve surgical exposure
Trendelenberg
This position causes increase in central venous, intraocular and intracranial pressure,
Trendelenberg
Trendelenberg can cause _______ to face, tongue, oropharynx, and eyes.
Edema
Trendelenberg should not be used when
Arms are extended on arm boards
Avoid using this positioning device in trendelenberg
Shoulder brace
If use of steep reverse trendelenberg is necessary this positioning device should be used
Foot board
What type of position would you place your patient for laparoscopic surgery
Reverse Trendelenberg
Lithotomy position is used to access what anatomical structure
Perineal
In lithotomy position how are the legs positioned
Legs are in flexion and abduction above the level of the torso
What are the types of lithotomy positioning
Low, standard high, exaggerated, and hemi-lithotomy
When positioning for lithotomy, legs should be
Elevated and lowered simultaneously
What nerve injury can occur from incorrect positioning of lithotomy
Peroneal injury
Raising and lowering the legs separately can cause
Hip dislocation, spinal torsion, and post op back pain
Flexion of the hips more than 90o in the lithotomy position can cause
Stretching of the sciatic and obturator nerves
Use of exaggerated lithotomy can cause
Compression of femoral canal and stretch of the sciatic nerve
While using leg holders which nerves can be affected
Peroneal and saphenous nerve
Lateral Decubitus is used for surgeries involving
The thorax, and kidneys when the supine position cannot provide sufficient exposure
How should you position for a nephrectomy
Lateral decubitus position, with kidney rest elevated, and flexion of the table
Body alignment is vital, who coordinates the positioning of the patient
The anesthetist
How should the shoulders, hips, head, and legs be maintained during lateral decubitus
In the same plane and turned simultaneously.
For lateral decubitus positioning, induction and intubation is performed in what position
Supine
Blood pressures should be obtained in which extremity while in lateral decubitus position
Nondependent arm
While in lateral decubitus position which facial areas must be free of pressure
Ear & Eye
While in lateral decubitus position it is necessary to assess perfusion of dependent arm by checking
Capillary refill
What medical condition has occurred due to use of lateral decubitus
Rhabdomyolysis
What is the placement of an axillary roll
Dependent side slightly caudal to the axilla
What is the purpose of the axillary roll
Relieve pressure on shoulder, axillary vessels, and brachial plexus of dependent arm
Arm abduction position should be
Less than 90o
When is the sitting position or beach chair position used?
Used in shoulder arthroplasty and arthroscopy
What are some of the advantages of the sitting position?
- Ventilation
- Forced vital capacity and FRC are within normal parameters in the seated position.
- The abdominal contents shift, causing less interference with diaphragmatic movement
- Greater expansion of dependent lung regions.
What are some disadvantages of the sitting position?
- Pooling of blood into the lower body
- Hypotension and hemodynamic instability.
- Excessive cervical flexion, impedes arterial and venous blood flow causing hypoperfusion
- Venous air embolism (VAE) is also a risk in this position.
Sitting position complication.
Sitting position & interscalene block for shoulder surgery may elicit the Bezold-Jarish reflex
What is the Bezold-Jarish Reflex?
- An inhibitory reflex mediated through cardiac sensory receptors.
- Associated with the beach- chair position.
- Venous pooling occurs due to dependent extremities - - Subsequent increase in sympathetic tone and ultimately a low-volume, hypercontractile ventricle
- Combination of venous pooling and paradoxical increased vagal tone results in sudden, profound bradycardia and hypotension
What are some of the prone position advantages.
Provides optimal exposure for spine & orthopedic procedures.
Advocated for intracranial procedures owing to the decreased risk of VAE
Prone position disadvantages?
Head, neck, shoulders & eyes must be checked preoperatively and periodically intraoperative
Maintain alignment of head and neck & provide support.
avoid pressure on the abdomen which can impede venous return
Protect the eyes from corneal abrasions & postoperative visual loss (POVL)
What is POVL?
- Postoperative vision loss (POVL) is associated with general anesthesia and prone positioning.
- Direct pressure to the periorbital region of the eye can cause increased intraocular pressure and blindness as the result of central retinal artery occlusion.
Mention some contributing factors for POVL.
- Duration in prone position,
- Eye compression
- Increased IOP
- Hypoperfusion
- Anemia
Name some causes of POVL.
Ischemic Optic Neuropathy (ION)
Central Retinal Artery Occlusion (CRAO)
Cortical blindness
Glycine toxicity
What is Ischemic Optic Neuropathy (ION)?
- Ischemia in a portion of the optic nerve.
- Majority of POVL after prone spinal procedures
What are some of the contributing factors to ION?
- Male gender
- Presence of coexisting diseases
- HTN
- Vascular Dz.
- Obesity
- Diabetes
What is the most common cause of ION?
- Intraoperative factors •Spinal surgery •Prone position •Prolonged surgical time •Large blood loss •Low hematocrit •Systolic blood pressure <100 mmHg
What is OPP?
ocular perfusion pressure
How is OPP calculated?
OPP= MAP-IOP
How does MAP affect OPP?
Intraoperative and anesthetic events that decrease MAP also decrease OPP.
What is the formula for OPP?
OPP= MAP-IOP
What are some Intraoperative events that decrease MAP and OPP?
Hypotension
Hemorrhage
hypovolemia
General anesthetics
What are some positions that may affect IOP?
Trendelenburg
Prone
What are other possible causes of POVL?
- Infarction of the visual pathways in the parietal or occipital lobes
- Air and particulate emboli
- Cardiopulmonary bypass and hypoperfusion from hemorrhage or hypotension
- Glycine toxicity
What is the least preferred head support technique?
Prone position with horseshoe adapter
What is CRAO?
Central retinal artery occlusion
Location and function of the Central retinal artery.
Central retinal artery is one of the first branches of the internal carotid & nourishes the internal layer of the retina
Is POVL caused by CRAO reversible?
•Some recovery of vision is possible if blood flow is restored within 4 hours
What are some of the treatments for CRAO?
- Thrombolytic agents
- Carbogen inhalation
Acetazolamide infusion - Ocular massage and paracentesis
- Various vasodilators such as intravenous glyceryl trinitrate.
What are the two optic end-arteries that leave that leave the eye susceptible to ischemia when interrupted?
Central Retinal Artery
Ciliary Artery
What is the most common cause of CRAO?
Improper head positioning that results in external pressure on the eye.
Hypertension, cardiovascular disease, increased BMI, Open angle glaucoma, and sickle cell anemia are risk factors in what form of POVL?
Central Retinal Artery Occlusion (CRAO)
In cases involving the head and neck, what positioning device is preferred over horseshoe headrest to prevent POVL
Three-pin head rests
True/False: Because three-pinned headrests avoids external ocular pressure, the risk of POVL is eliminated.
False, unpredictable causes of ION can still lead to POVL with the use of three-pinned headrests.
What is the most common name for “Reperfusion injury?”
Compartment syndrome
A life-threatening complication often associated with poor patient positioning and use of devices that can lead to tissue ischemia and muscle and nerve infarction
Compartment syndrome
Lower extremity compartment syndrome is mostly distinguished with what type of surgical positioning.
Lithotomy position in surgeries of long duration
What two surgical positions are most at-risk for compartment syndrome?
Lithotomy
Trendelenburg
What 4 preoperative findings would indicate patient is at-risk for surgery-associated compartment syndrome?
Advanced age
Extremes of body habitus
Patient history of nerve ischemia or neuropathy
Connective tissue disease
What are 4 intraoperative factors can put the patient at-risk for compartment syndrome?
Systemic hypotension
Anemia
Prolonged operative duration
Vasoconstrictive drugs
Intrapelvic retractors can lead to what postoperative complication?
Compartment syndrome from vascular obstruction of the major extremity vessels
The lithotomy position can lead to compartment syndrome from flexion of what two body parts?
Knee
Hip
Why does compartment syndrome often occur in intraoperative elevated extremities?
External compression from poorly padded positioning devices or straps that are too tight.
What two factors cause low flow states in the leg and are factors in the development of compartment syndrome?
Intraoperative hypotension
Leg elevation
Blood pressure to the legs decrease by how much with every cm change in leg height?
0.75mmHg
What is the definitive treatment for compartment syndrome?
Fasciotomy
What three complications of untreated compartment syndrome can lead to amputation or death?
Tissue necrosis
Rhabdomyolysis
Acute renal failure
What is the surgical complication that can occur when a negative pressure gradient forms between the right atrium and the veins at the operative site.
Venour Air Embolism
What surgical complication is a well known complication of surgeries that occur in the sitting position when entrained air?
Venous air embolism
What surgical complication occurs when entrained air enters the right atrium of the heart and creates a V/Q mismatch by limiting gas exchange in the lungs and displaces air in the pulmonary vasculature?
Venous Air Embolism
No effect for minimal amounts of air - -
Hypotension
Arrhythmias
Cardiac arrest
death with larger volumes…
Are possible physiologic effects of what surgical complication?
Venous Air Embolism
Air emboli leaving from the left ventricle can lead to what two surgical complication?
Myocardial infarction
Cerebrovascular accident
The presence of Nitrogen and an increase in dead space will lead to what three assessment findings in a VAE?
Drop in end-tidal C02
Presence of end-tidal Nitrogen
“Mill-wheel murmur” through precordial or esophageal auscultation.
What is the major risk-factor fo the development of ar Paradoxical Air Embolism (PAE)?
Patent Foramen Ovale (PFO)
What is the gold-standard diagnostic in the evaluation of a PFO to assess the risk of PAE and VAE development?
Transesophageal Echocardiogram
VAE can be aspirated from systemic circulation by what technique?
Aspiration from a multi-lumen CVP placed at the SVC.
Patient who are prone during surgery should have their CVP placed in what position?
At the junction of the inferior vena cava to the right atrium.
Entrained air will enter via lumbar spinal and ipdural veins.
PFO can occur in as high as ________% of the population?
35%
The gold standard for the detection of a PFO is a TEE with contrast, but the cheaper, safer, alternative is the…
Transcranial doppler
Act of positioning patients for surgery is a group responsibility requiring?
Teamwork, Timing, Communication, and Knowledge of strategies that protect patients against injury.
What is the main goal of positioning patient accordingly?
To allow optimal surgical access while minimizing potential risk to patient
Nurse anesthetist standard V related to positioning?
Monitor & assess patient positioning & protective measures.
Role of anesthesia providers pertaining patient’s positioning?
Essential role in coordinating patient positioning & continually monitor & assess subsequent changes in patient’s physiologic status.
Contributing factors of physiologic changes?
Surgical position, length of time, padding & positioning device used, type of anesthesia administered, operative procedure.
What Physiologic changes can be seen related to positioning?
Cardiovascular, respiratory, and nervous system. Skin, eyes, breast and genitalia.
Cardiovascular hemodynamic changes are usually minimal in these two positions.
The supine and lateral positioning.
Cardiac output and blood pressure are often decreased in what three positions?
The sitting, prone & flexed lateral positions.
Preload and strove volume are decreased by?
Blood pools in dependent body areas
Pooled blood from depended body parts reduces what?
Blood return
How does lateral decubitus position affect the cardiovascular system?
Venous return is reduced due to legs being dependent thus causing hypotension.
In lateral decubitus position what is the kidney rest compressing?
The Vena Cava
Where should the kidney rest be anatomically placed?
Should lie under the dependent iliac crest.
How does lithotomy position affect the cardiovascular system?
Bp stays normal or higher.
Why does lithotomy position causes hypertension?
Because elevated legs auto transfuse 100-250 mls of blood per lower limb.
AKA: Cephalad blood return.
What is the patient at risk for in the head-up sitting and lithotomy position?
Hypo-perfusion & ischemia if hypotension occurs.
Hemodynamic changes can be minimal if patient is placed in what position?
In a 45-degree head-up sitting position.
Why is the cardiac output decreased when patient is raised to 90 degrees?
Because of venous blood pools in the extremities.
GA and positioning may lower perfusion pressure but a patient’s BP should not drop more than __ percent from their normal BP.
20
Though neuraxial and peripheral nerve blocks are associated with permanent and temporary nerve injuries, the majority of injuries are not related to positioning but..
Poor block technique, hematoma formation, and direct needle trauma.
Patients with BMI less than___ are likely to develop ___ neuropathy.
Less than 22 and ulnar neuropathy
Muscular physique patients are at an increased risk for __.
Compartment Syndrome
How does obesity increase morbidity during surgery?
Large tissues place increased pressure on dependent body parts. Adipose tissue is poorly perfused.
What are preexisting conditions associated with increased incidence of positioning complications?
HTN, DM, PVD, Peripheral neuropathies, Alcoholism, Smoking within 1 month of surgery, limited joint mobility, and liver disease
Closed claims studies found that this nerve is the most commonly injured during surgery.
Ulnar
What are complications patients encounter after damage to the ulnar nerve?
Claw hand (ring and little finger hyperextended). Loss of abduction & adduction of fingers & flexion
What are contributing factors of ulnar neuropathy?
Surgical positioning, mechanical devices (tourniquet, BP cuff), prolonged hospital stay, sternotomy & sternal retraction. Age>50, preexisting disease, gender, Body habitus, and preexisting neuropathy.
Ways OR staff can prevent ulnar neuropathy.
Pad bony prominences, supinate arms (PALMS UP) in supine position, abduct arms <90 when not tucked.
Which way should the patients palms face when their arms are tucked?
Inward
Turning the head to the side with arms abducted can cause stretching &; compression of the contralateral___.
Brachial plexus
How can a CRNA relieve pressure on the brachial plexus when the patient is in a lateral position?
Place an axillary roll caudal to the dependent axilla to relieve pressure.
