Mod10: Bone Cement - Fat Embolism Syndrome - Venous Air Embolism Flashcards
Orthopedic surgery
Characteristics of Bone Cement:
Frequently used in joint arthroplasties
Used to affix implants and remodel lost bone
Cement interdigitates with the intertices of cancellous bone (spongy inner layer of bone; found at the ends of long bones) and strongly binds prosthetic device with patient’s bone
Mixing polymerized methylmethacrylate powder with liquid methylmethacrylate causes polymerization and cross-linking of the polymer chains
Exothermic reaction occurs and leads to hardening of the cement and expansion against the prosthetic components

Orthopedic surgery
Effects of Bone Cement placement:
Exothermic reaction occurs and leads to hardening of the cement and expansion against the prosthetic components
What results is Intramedullary HTN (> 500mmHg)=> this can cause embolization of fat, bone marrow, cement, and air into the venous channels

Orthopedic surgery - Bone Cement placement
If residual methylmethacrylate monomer gets absorbed systemically =>
can produce vasodilation and a decrease in SVR

Orthopedic surgery - Bone Cement placement
Systemic embolization of bone cement triggers the release of
Tissue thromboplastin
=>
triggers PLT aggregation
microthrombus formation in the lungs, and
CV instability as a result of the circulation of vasoactive substances

Orthopedic surgery - Bone Cement
What should you monitor carefully during placment?
Changes in oxygenation, ventilation, and hemodynamics!
Orthopedic surgery - Bone Cement Syndrome
Clinical manifestations of bone cement implantation syndrome:
Hypoxia (due to increased pulmonary shunt)
Hypotension (vasodilation)
Arrhythmias (including heart block & sinus arrest)
Pulm HTN (increased PVR)
Decreased CO

Orthopedic surgery - Bone Cement Syndrome
Emboli a/w Bone Cement implantation most frequently occur during:
Insertion of a femoral prosthesis for hip arthroplasty
Orthopedic surgery
What can the anesthtist do to minimize effects of Bone Cement Syndrome
Being proactive prior to insertion…..
anticipate…you will know by the fumes released with mixing
Increase FiO2 before cement put in joint
Maintain euvolemia
Orthopedic surgery
What the Surgeon do to minimize effects of Bone Cement Syndrome
Create a vent hole in distal femur to relieve intramedullary pressure
Perform high-pressure lavage of femoral shaft to remove debris (and potential microemboli)
Use femoral component that doesn’t require cement
Orthopedic surgery
Cement vs Cementless protheses; which last longuer?
Cement can loosen over years,
whereas cementless implants are made of porous material, allowing natural bone to grow into them
Cementless protheses generally last longer
Orthopedic surgery - Cement vs Cementless protheses
Difference in lenght of recovery
Cementless protheses are better for younger, active pt’s but longer recovery
Cementless implants require healthy active bone formation and recovery may be longer
Cemented prostheses preferred for those patients who are > 80, less active, have osteoporosis
Orthopedic surgery
Joint replacement articular surfaces can be:
Metal, plastic, or ceramic
In many cases cemented and cementless components are used in the same patient (eg, total hip arthroplasty).
Articular surfaces on modern prostheses may be metal, plastic, or ceramic.
Orthopedic surgery - Fat Embolism
Some degree of fat embolism probably occurs with which types of fractures?
All Long-bone fractures
Orthopedic surgery - Fat Embolism
Incidence and mortality of Fat embolism syndrome
Less frequent (about 3-10% of orthopedic trauma patients)
but has a high mortality rate (10-20%)
Orthopedic surgery - Fat Embolism syndrome
Presentation of Fat Embolism syndrome
when?
Usually within 72 hours of fracture of long-bone or pelvis
Can also occur after CPR
After parenteral nutrition with lipid infusion (TPN/PPN)
after liposuction
Orthopedic surgery - Fat Embolism syndrome
Triad of symptoms
Dyspnea - Confusion - Petechiae
Orthopedic surgery - Fat Embolism syndrome
Triad of symptoms & Other symptoms
Dyspnea - Confusion - Petechiae
Petechiae on chest, upper extremities, axilla, conjunctiva
Sometimes globules of fat can be seen in retina, urine, sputum
Thrombocytopenia, prolonged clotting times
Serum lipase may be high
Pulmonary presentation usually starts as mild hypoxia
=> progresses to severe hypoxia and respiratory failure
CXR normal at first => can progress to the appearance of diffuse pulmonary opacities
Orthopedic surgery - Fat Embolism syndrome
Theories of pathogenesis
Exact mechanism still not known
Fat globules or droplets released by disruption of fat cells in the fx’d bone
=> enter bloodstream thru tears in medullary vessels and can be deposited into pulmonary capillary beds and travel to the brain through AV shunts
Droplets can deposited in the microvasculature and this causes
=> local ischemia and inflammation, and at the same time
=> inflammatory mediators and vasoactive amines are released, and PLT aggregation occurs
Metabolic changes cause normal circulating fat to become free fatty acids
=> These FFAs ultimately aggregate to become fat globules or chylomicrons
=> behave in same way as just mentioned (deposited in pulmonary capillaries)
Regardless of source => increased FFA levels can have toxic effect on capillary-alvelolar membrane leading to the release of vasoactive amines and prostaglandins and the development of ARDS
Orthopedic surgery - <strong>Fat Embolism syndrome</strong>
Neurological symptoms:
Agitation - Confusion - Stupor - Coma
These symptoms likely due to capillary damage in cerebral circulation and cerebral edema
Hypoxia exacerbates this
Review question on fat embolism syndrome: Connelly page 277
Orthopedic surgery - Fat Embolism syndrome
Neuro sx’s d/t:
Capillary damage to cerebral circulation
Cerebral edema may be exacerbated by hypoxemia
Orthopedic surgery - Fat Embolism syndrome
Presentation under GA:
Hypoxia with increased A-a gradient
(A-a gradient is difference between alveolar concentration of oxygen and arterial concentration of oxygen => increased A-a gradient means Oxygen is not moving from the Alveoli to the blood)
Tachycardia
Petechial rash on upper body
Decreased pulmonary compliance
Increased PA pressures
Decreased CO
ECG
[ST changes (ischemia)]
Fat Embolism Syndrome - Triad of presenting symptoms
Petechiae
Petechiae on chest, upper extremities, axilla, conjunctiva

Fat Embolism Syndrome - Triad of presenting symptoms
Sometimes globules of fat can be seen in
Retina - Urine - Sputum

Orthopedic surgery - Fat Embolism syndrome
Diagnosis:
Gurd Diagnostic Criteria
Schonfeld Fat Embolism Index
