Pathophysiology of Osteoarthritis
NON-systemic disease!!
- Degenerative disease: loss of cartilage & associated w/non-systemic inflammation
- Articular wear/tear
- Affects articular surfaces of one or more joints
What are a few key anesthetic management considerations for EVERY type of ortho case?
- Comorbidities: CV status & baseline vitals
- Positioning: effect on pulm/CV, possible nerve injuries
- Desired vent settings: based on positioning & pt physiology
- Blood loss: expected & acceptable blood loss
- Airway concerns?: Fiberoptic/glidescope available
- Regional vs General
- Risk factors specific to the type of procedure: prophylactic tx? (DVT proph)
OA Clinical Manifestations
**Limited physical activity/mobility
Pain
Crepitance
Deformity of involved joints
Swelling of DISTAL interphalangeal joints = Heberden’s nodes
Swelling of PROXIMAL interphalangeal joints = Bouchard’s nodes
OA most commonly affects ____ or ___.
Hips or Knees
OA pt’s are usually on medication? What are we concerned about?
NSAIDS = Bleeding! (Consider GIB prophylaxis in preop)
Pathophysiology of Rheumatoid Arthritis
SYSTEMIC disease
- Immune-mediated joint destruction with CHRONIC, progressive inflammation of synovial membrane
- Involves multiple joints in a SYMMETRICAL fashion
Systems affected by RA:
- CV: pericardial thickening, valvular fibrosis, conduction defect –> increasing CAD r/t corticosteroids
- Pulm: effusions
- Hematology: anemia
- Endocrine: adrenal insufficiency r/t steroids (stress dose if w/in 6mo)
Medication use associated w/RA? What are we concerned about?
NSAIDS = Bleeding Steroids = need stress dose; cardiac/adrenal insuff Methotrexate = BM suppression
What are the two major things we are concerned w/RA & AIRWAY?
Atlantoaxial Instability & Cricoarytenoid Arthritis
Describe the Atlantoaxial Instability found in RA pts
C-spine issues w/erosion of ligaments by rheumatoid involvement of the bursae around the ODONTOID PROCESS of C2 causes ATLANTO-AXIAL SUBLUXATION with flexion…
Pushes odontoid into foramen magnum –> compressing spinal cord against the posterior arch of C1 —> potentially reducing vertebral BF
What type of subluxation is found w/RA pts?
ANTERIOR Subluxation is the most common form
Consider a fiberoptic intubation if atlantoaxial instibility is > ___.
Instability >5mm = fiberoptic intubation w/manual inline stabilization
How will Cricoarytenoid arthritis present?
Hoarse or inspiratory stridor = narrow glottic opening
Anesthetic considerations/concerns for cricoarytenoid arthritis
- Use smaller ETT
- Post-extubation concerns due to development of airway obstruction -(Judicious use of narcotics or epidural analgesia for pain relief should be considered)
- Post-op O2
Airway assessment for RA pt’s should include:
- Flexion/extension X-rays (65% of RA pts will develop atlantoaxial instability within 2 years – will tell us if we can use glidescope or need to do awake fiberoptic intubation)
- Neck pain? HA?
- Neurologic symptoms in arms or legs w/neck motion?
Immediate pre-op concerns with RA pt’s (technical difficulties)
Starting A-lines & central lines (r/t calcified vasculature)
Positioning issues
What is similar between RA & AS?
C-spine instability –> consider awake fiberoptic
RA = Subluxation of C2 AS = Fused C-spine
Describe the pathopysiology of Ankylosing Spondylitis
SYSTEMIC Disease
- Fused vertebrae starts at sacrum & ASCENDS to cervical spine
- Ossification of ligaments at bone attachment sites –> progressive ossification involves joint cartilage & disk space of axial skeleton with eventual ankylosis –> immobility & consolidation of joints
Who does AS affect most?
Men > women
AS affects what part of the body?
Cervical spine
Hips
Shoulders
Costovertebral joints
**Careful positioning!!
Systems affected by AS
- Pulm: Lung function impaired, restrictive lung dx picture, rigid rib cage (DECREASED FRC)
- CV: Aortic regurg & BBB
- Verbetral Column: Fused, making lumbar epidural/spinal anesthesia difficult/impossible. May require paramedian approach.
What do we take into consideration when deciding between regional or general?
1) Pt preference
2) Pt Health/Comorbidities
3) Expertise of anesthesia provider
4) Duration of procedure
5) Surgeon’s preference
**Combined techniques very popular
How can we minimize homologous blood transfusions?
1) Induced hypotension (on right pt)
2) Intra-op hemodilution
3) Cell savers
4) Preservation of normothermia (Cold pts = bleeding)
5) Lower transfusion “trigger” (cosider ABL)
6) Aprotonin (not on market anymore but Vicky still thought it was nec to bring up- protease inhibitor caused problems w/thromboembolism & kideny dysfxn)
Two reasons we use tourniquets
Reduce blood loss & surgeon visualization
Physiology behind tourniquet pain?
Result of unmylinated C fibers (slow conducting) RESISTANT to LA = even w/block still have sx of tourniquet pain
Under GA it causes increased SNS outflow = HTN & Inc HR
Onset of tourniquet pain
30-90 min after inflation
Tx of tourniquet pain
Higher MAC– deepen w/IA
Be careful w/narcotics
Release of a tourniquet will cause…
Release of metabolic byproducts –> INCREASE MV due to an inc CO2
When using a tourniquet, how much pressure do you add to a patient’s SBP for an UPPER extremity procedure? How much time is allowed?
50-75mmHg
1hr
When using a tourniquet, how much pressure do you add to a patient’s SBP for a LOWER extremity procedure? How much time is allowed?
100-150mmHg
1.5-2 hrs
When using a tourniquet, how much pressure do you add to a PEDIATRIC pt’s SBP?
100mmHg
When using a tourniquet, what can you do if the surgeon requires additional time after the “max safe time” has been reached?
Deflate the tourniquet for 10 min to reperfuse & then re-inflate
**Max safe time = 2hrs
Name 5 tourniquet complications
1) Nerve injury
2) Post-tourniquet syndrome (PTS)
3) DVT
4) Compartment syndrome
5) Digital necrosis
How does post-tourniquet syndrome manifest?
Pronounced &, at times, prolonged postop SWELLING of the extremity
Nerve injury is the most complication from the use of tourniquets during upper or lower extremities?
Upper
Physiologic changes associated w/the sitting position/beach chair
- Decreased: MAP, CVP, PAOP, SV, CO & CPP
* Increased: PAO2-PaO2 gradient, pulm vasc resistance & total peripheral resistance
Without GA, the physiologic changes associated w/the beach chair position are usually compensated by_______.
Increase SVR 50-80% **This is what is blocked by anesthetics
What should you take into consideration when caring for a poorly controlled htn pt who needs to be in the beach chair position?
Autoregulation of CBF is shifted to the RIGHT = requires higher CPP/MAP to ensure adequate cerebral perfusion (always need an accurate baseline BP).
___mmHg drop in BP for every ____cm the ear (level of the head) is above the heart.
2mmHg drop in BP for every 2.5cm the ear is above the heart.
Anesthetic considerations w/beach chair position
- Avoid deliberate hypotension
- Tilt legs up after head is up to limit pooling of VR
- Use SCDs
- Adequate PRELOAD (500ml pre-op)
- Know baseline BP preop
- Questions to ask: Take ACE-I? dizzy/tachy w/position changes?
Drugs to consider using w/beach chair position
Phenylephrine or Ephedrine Ketamine 25mg (add to induction dose of propofol; avoid w/severe HTN & AS)
Main pre-op anesthetic considerations with shoulder arthroSCOPY vs arthroPLASTY
ArthroSCOPY = mostly lateral decub; minimal EBL (1IV); minimal pain ArthroPLASTY = mostly beach chair; inc EBL to 1L (need 2 IVs); PAIN (need block or PCA)
**Both done w/GA or interscalene block with either beach chair or lateral decubitus position
The shoulder is innervated by which dermatomes?
C5-6 dermatomes
Post op morbidity & mortality r/t lower extremity procedures are usually due to…
DVT & PE —> prevent venous stasis w/SCD’s & early ambulation
- Total Hip 42-57% DVT & 0.9-28% PE
- Total Knee 41-85% DVT & 1.5-10% PE
- Hip Fracture 46-60% DVT & 3-11% PE
Due to the increased risk of DVT & PE w/lower extremity procedures, which medication should always be considered??
LMWH – outweigh risk/benefits
How long do you wait after administration of LMWH before administration of a block?
12hrs = would have to come in the night before
How long after administration of LMWH do you have to wait to remove an epidural catheter?
8hrs
Reaming (drilling within core of a bone to make space for a rod/nail) causes an increase in _____ & _____.
blood loss & risk of emboli
When can fat emboli syndrome (FES) occur?
12-72hrs post op & intraop
Triad of symptoms of FES
Dyspnea
Confusion
Petechia to chest
***presents as acute resp distress/cardiac arrest
Under GA, what would you notice if your pt experienced FES?
Decreased arterial oxygenation
EKG changes
Sudden DROP in ETCO2
Do lower or upper extremity procedures have the potential for large blood loss?
LOWER = large blood loss >1500ml
***Type & cross
When taking regional anesthesia into consideration (whether in conjunction w/GA or alone) what should you also be thinking about…
- pt difficult to position?
- case length predispose pt to discomfort?
- painful procedure in which pt needs post-op pain control?
**Alwaysssss ASA STATUS & CO-EXISTING DISEASES
Use of hypotensive techniques or regional anesthesia REDUCES blood loss by ____ to ___%.
30-50%
What are your concerns w/having a REVISION ortho procedure?
Need to ream bone & old cement = Inc BLEEDING & EMBOLI
Describe the physiologic response pt has to metylmethacrylate cement.
Cement = exothermic reaction –> intramedullary htn –> pushes fat/air/marrow into femoral venous channels
- Decreased SVR
- Hypotension
- Hypoxia
Anesthetic considerations to using methylmethacrylate cement.
- Open fluids if pt can tolerate it
- 100% O2 even on low flows
- Phenylephrine gtt ready
- Watch ETCO2 (will be first sign of CV collapse)
Patients at high risk for developing hypotension during THR w/use of cement
1) Metastatic CA
2) Removal of hardware
3) Revisions
Methylmethacrylate cement causes hypotension by:
DIRECT VASODILATION or by forced entry of air/fat/bone marrow into venous system resulting in PULMONARY EMBOLI
When do THR pt’s develop hypoxia after using methylmethacrylate cement?
Immediately after insertion of cement & for up to 5 days into post-op period
How can we prevent hypoxia w/cement use?
- Use NC
- Pulse ox for several days (can last up to 5 days after insertion)
- Judicious use of narcotics (avoid hypovent or airway obstruction)
- Appropriate fluid management/diuresis
When dose blood loss occur for TKR vs THR?
TKR = blood loss POST-op (r/t tourniquet-- can be increased for 24hrs) THR = blood loss INTRA-op
Typical pt presenting w/fractured neck of femur
Old women (>80yo) with dementia after falling in nursing home
With fractured neck of femur, what is the most common cause of intra op death?
MI & PE
*Also have complications like pneumonia contributing to mortality
What time of spinal would a pt w/a fractured neck of femur need?
HYPObaric spinal – most likely wont be able to tolerate position changes.
Anesthetic considerations for pts w/LE amputations
- Gangrene, septic, chronic dz, trauma = regional a good idea???
- EBL 250ml
- High mortality of 10-20%
- Morbidity: phanton limb 85-95%, wound infection <15%, pneumonia 10-15%, MI 7-10%, emboli 6-19%, CVA 5-10%
When is the anterior vs posterior approach used in spine surgeries?
Anterior = thoracic & cervical spine Posterior = mid thoracic & below
How do we facilitate a ‘wake-up test’ in the middle of a thoracolumbar spinal surgery?
Tell pt ahead of time they will asked to move extremities in middle of case while prone & not be able to talk (practice pre-op). There is a 20% chance of recall.
- Avoid 0/4 twitches – give incremental doses of MR
- Watch opioid use & AVOID reversals
- Turn down IA & turn on low nitrous
EBL for a thoracolumbar surgery depends on…
of segments fused
Most common stimulation site for SSEP in upper vs lower ext?
UE = Median nerve LE = Posterior tibial nerve
When using SSEP, what is being monitored?
Posterior spinal cord function (sensory) via a current delivered to peripheral nerves. Looks at the…
- Amplitude
- Shape
- Latencies
VA effect on SSEP
Decrease amplitude/distort electrical signal
What does a decrease in SSEP signal despite no change in anesthetic or surgical changes mean??
HYPOTENSION