Mod10: Anesthesia for Orthopedic Surgery - Positioning Flashcards
Anesthesia for Orthopedic Surgery
Anesthetic Challenges
Minor
Finger - Knee arthroplasty
Major
Spinal fusion for scoliosis - Hemipelvectomy
Variety of patients
Neonate with CHD - Young healthy adult
Elderly with CAD, COPD, DM, OSA
206 bones in body
Vast range of patients – neonate with Congenital Heart disease, Elderly pt with multi-organ failure, and at the very least, CAD in almost all patients of advanced age.
Providing anesthesia for orthopedic surgery requires knowledge of a wide range of procedures, as well as competence to care for a diverse group of patients.
Example of some of the more straightforward procedures are: repair of a minor finger injury or a knee arthroplasty (more commonly known as a knee “replacement”)
Examples of more complex or major orthopedic surgical procedures include: a spinal fusion for scoliosis or a hemipelvectomy
Patients can vary in age and comorbidities. For example, at CHOG, you may be caring for a young neonate with a congenital heart defect. In a trauma center, you may provide anesthesia for a young, otherwise healthy patient with a major pelvic fracture following a MVA. Another example would be an elderly patient with a hip fracture who has CAD, along with a number of other comorbidities, such COPD, DM, and/or OSA
Anesthesia for Orthopedic Surgery
Special Anesthetic Considerations
Positioning
Pneumatic tourniquet
Bone cement
Fat embolism
Venous air embolism
Thromboembolic event
Large blood loss
Some special anesthetic considerations specific to orthopedic procedures include: positioning, pneumatic tourniquet, bone cement (polymethylmethacrylate), fat emboli, thromboembolic events, and the potential for large blood loss
Anesthesia for Orthopedic Surgery
Most common Positions:
Prone
spine cases (e.g. PCF, lumbar and thoracic fusions, laminectomies
Beach chair (semi-sitting)
Shoulder arthroscopy or Total shoulder arthroplasty
Lateral
Some hip surgeries; some thoracic and lumbar spine cases
Supine
with HOB down (knee surgeries – knee scope or total knee arthroplasty) – usually have leg holder for leg
Positioning will depend on access needed and surgeon preference
Anesthesia for Orthopedic Surgery
Prone Position
used for:
Spine cases
(e.g. PCF, lumbar and thoracic fusions, laminectomies)
Anesthesia for Orthopedic Surgery
Beach chair (semi-sitting) Position
used for:
Shoulder arthroscopy
or
Total shoulder arthroplasty
Anesthesia for Orthopedic Surgery
Lateral Position
used for:
Some Hip surgeries
Some Thoracic and Lumbar spine cases
Anesthesia for Orthopedic Surgery
Supine (with HOB down) Position
used for:
Knee surgeries
Knee scope or total knee arthroplasty
usually have leg holder for leg
Anesthesia for Orthopedic Surgery
Positioning
extreme variations:
Wilson frame
Fracture table (Chick)
Jackson table
Positioning will depend on access needed and surgeon preference
Anesthesia for Orthopedic Surgery
Spontaneously breathing patients under GA
Altered pulmonary function d/t Positioning
Decreased Vt and FRC
Increased closing volume
(i.e. their small airways are more prone to collapse)
Diaphragm displaced unevenly
(due to loss of muscles tone)
[Review Miller Chapter 19]
Orthopedic Surgery - Altered pulmonary function d/t Positioning
Patients under GA with spinals and epidurals
Loss of abdominal and thoracic muscles function
at the affected dermatome level
Orthopedic Surgery - Altered pulmonary function d/t Positioning
Diaphragm function
Patients only having a neuraxial anesthetic without GA nor NMB:
Normal
Orthopedic Surgery - Altered pulmonary function d/t Positioning
Atelectasis d/t general anesthesia
avoidable?
Unavoidable
Orthopedic Surgery - Altered pulmonary function d/t Positioning
Minimizing atelectasis during GA
how?
Set an appropriate Vt for the patient
Add PEEP
Give sigh breaths
Use recruitment maneuvers (”Valsalva”) from time to time to try to re-open collapsed alveoli
(delivery of sustained pressure 30-40 cmH20 – for several seconds => just know you will have a drop in BP d/t decreased venous return)
=> This may not be appropriate for all patients
=> i.e. if you are battling hypotension, might not be the time to do this
Orthopedic Surgery - Altered pulmonary function d/t Positioning
Positioning that impairs diaphragmatic, chest wall or abdominal movement
lead to:
Further increase the risk for atelectasis and intrapulmonary shunt
Positions that cause gastric contents to be pushed cephalad or compressed => decreased FRC and TLV
May see increased Peak Airway Pressures
=> Smaller VT => Atelectasis => Decrease SpO2 reading
Orthopedic Surgery - Altered pulmonary function d/t Positioning
How to Prevent or Treat pulmonary function alterations?
Make sure abdomen is free of pressure.
May need to give NMBs and/or change to PCV and adjust other vent settings
Prone position actually can improve respiratory function
Under GA, prone position is more favorable than supine in relation to lung volumes and oxygenation
Orthopedic Surgery - Positioning and CV Function
Altered CV functions
VR
Arterial tone
Autoregulation
Risk for hemodynamic compromise with position change (because the body’s mechanisms of autoregulation/adjustment are inhibited)
Orthopedic Surgery - Positioning and CV Function
Causes of Altered CV functions
GA
Muscle relaxation
PPV
Neuraxial blockade
Orthopedic Surgery - Positioning and CV Function
Awake patient lies down in a supine position
CV changes:
Improved VR
Increased CO
Increase in right heart filling pressure
Decrease in HR (Baroreceptor-mediated)
Vasodilation (there are also mechanoreceptors and arterial reflexes involved in this autoregulation)
Ultimately the body normalizes (autoregulates) the HR and BP back to baseline)
Orthopedic Surgery - Positioning and CV Function
Patient under anesthesia in a supine position
Autoregulation:
Compromised
Patients hemodynamically labile just after induction or just after a position changed
Monitor BP frequently and treat appropriately
This is especially important to remember when the surgical team is rushing to get the patient positioned right after induction or when you have flipped your patient to a prone or lateral position
Remember to hook all of your monitors back up after your airway management (i.e. hooking circuit back up and making sure you haven’t lost your airway)
Orthopedic Surgery - Positioning and CV Function
CV effects of Sitting position or Rev. T-burg
BP can drop significantly when changing from a supine to sitting position
Consider sitting patient up in increments
Be ready to treat with volume and/or pressors
May need to turn INH agent down
Orthopedic Surgery - Positioning and CV Function
CV effects of Extreme flexion of neck
Can inhibit venous and arterial blood flow
=> decreased cerebral perfusion and increased cerebral venous congestion
Can impair respiratory mechanics
ETT can become obstructed; with flexion
=> maintain 2 FB between chin and sternum
Orthopedic Surgery - Positioning and CV Function
CV effects of Prone position
If the lower extremities are kept level with the torso
=> hemodynamic stability is preserved
If legs lowered or if OR bed is tilted L or R
=> VR will decrease or increase accordingly
Orthopedic Surgery - Positioning and CV Function
CV effects of Lateral position
There is potential for a decrease in VR if kidney rest isn’t properly placed
=> should be placed under the iliac crest
=> prevents compression of the IVC and to prevent impaired ventilation of the dependent lung
Do not place under flank or lower costal margin
Monitor pulse ox in dependent arm
=> a decrease in saturation may be an early sign that blood flow to axillary neurovascular structures is compromised or inadequate
Orthopedic Surgery - Effects of positioning
Effects of Lateral Position and V/Q Mismatch
in an wake, spontaneously breathing patient:
V/Q ratio is not greatly changed
Dependent lung => better ventilated and better perfused
Orthopedic Surgery - Effects of positioning
Effects of Lateral Position and V/Q Mismatch
Once the patient is anesthetized and mechanically ventilated:
Pulmonary function is compromised
Non-dependent lung (Up lung) = better ventilated, but poorly perfused
Dependent lung (Down lung) = poorly ventilated, but blood flow increases to this lung (gravity) => so better perfused
Orthopedic Surgery - Effects of positioning
Nerve injury results when:
Nerves are compressed, stretched, or lack adequate blood flow
Injury can also occur as the result of direct trauma
(laceration during surgery; injury from needle during nerve block placement)
Orthopedic Surgery - Effects of positioning
Most common nerve injuries:
Ulnar nerve damage
is complex,
involves a number of factors,
can’t always be prevented;
exact etiology is not fully understood;
damage can be temporary or permanent
Orthopedic Surgery - Effects of positioning
Second most common nerve injuries:
Brachial plexus injury
results from stretching and compression;
associated with abducting the arm > 90 degrees,
rotation of the head from L to R (laterally),
asymmetrical sternal retraction for dissection of the internal mammary artery during open heart surgery
Orthopedic Surgery - Effects of positioning
How to prevent Brachial Plexus injury?
Keep head midline,
arms at side,
mildly flex elbows, and
forearms should be supinated
Orthopedic Surgery - Effects of positioning
Potential causes of Postoperative visual loss:
Ischemic Optic Neuropathy (primarily) and
Central retinal arterial occlusion
Orthopedic Surgery - Effects of positioning
Perioperative factors a/w Postoperative visual loss:
Extensive periods of hypotension,
long surgeries in the prone position,
excessive blood loss,
excessive administration of crystalloid,
anemia or hemodilution,
increased IO or venous pressure from the prone position
Hyperglycemia,
hypothermia,
repeat spine surgery in prone position,
preop donation of blood leading to a low Hct,
smoking,
obesity
Orthopedic Surgery - Effects of positioning
Perioperative factors a/w corneal abrasion/injury
and Prevention/Treatment:
Swelling of eyes during prone cases is associated with corneal abrasion/injury;
carefully tape the eyes,
lacrilube;
watch out for dangling objects (lanyard with badge, stethoscope);
remind patients not to rub the eyes;
be very careful and aware of eyes when changing positions
Orthopedic Surgery - Effects of positioning
Effects of Rheumatoid Arthritis
Joint pain and inflammation, can affect other organs
Frequent fatigue, low grade fever, anorexia, muscle/joint aches, stiffness;
check cervical ROM; may need C-Mac or Glidescope;
can have patient position themselves prior to induction and not deviate from that position during induction
Orthopedic Surgery - Effects of positioning
How should pt with Decreased ROM (e.g. Osteoarthritis)
be positionned?
According to patient’s ROM
Decreased ROM: Osteoarthritis => Systemic symptoms are not present.
Localized joint pain.
Position patients according to their comfort and safety
Sometimes patients are contractured, and you have to position according to patient’s ROM
Orthopedic Surgery - Effects of positioning
Which patients are induced on the stretcher or bed?
Trauma and/pain
may prohibit movement from stretcher to bed
Prone cases
(usually induce on stretcher)
Orthopedic Surgery - Effects of positioning
Safety considerations with stretcher or bed at induction
Still need to bring the patient to top of the bed,
position the head and neck in the sniffing position,
maximize your ability to access the patient
Bring machine to you, etc.
May even have to move the OR bed over and out of way, so that the patient is in a SAFE position for induction
This may involve removing or adjusting parts of the bed.
No matter how much of a rush you or the surgeon is in, as long as the patient is not coding ;), move the patient to a position that is SAFE and IDEAL for induction
Orthopedic Surgery - Effects of positioning
For a SAB for hip fx
may have to place SAB with patient in lateral position
Make landmarks as usual;
Hook patient up to monitors,
O2 as necessary;
Aim for belly button,
can throw you off placing lateral position
Orthopedic Surgery - Effects of positioning
Considerations for Versed, fentanyl or other anxiolytics, narcotics
AS TOLERATE
many of these patients are fragile, elderly, lots of comorbidities;
overall patient morbidity goes up with hip fracture in and of itself in the elderly;
some may have already had narcotics;
consider holding versed in elderly because of PCD
