Test 1: Anesthesia for Orthopedic Surgery Preoperative/ Intraoperative Flashcards
What systems are the primary focus of a preoperative evaluation?
- CNS
- Respiratory
- Cardiac
What does MILS stand for?
Manual in-line Stabilization (MILS)
What is the goal of MILS?
Stabilization of head, neck and torso in neutral position
What patients require MILS?
Patients who have not been cleared from C-spine precautions
How many clinicians are required for MILS and what are their responsibilities?
3 Clinicians required
- Stabilize and align head in neutral position without applying cephalad traction
- Stabilize shoulders
- Intubate
What airway maneuvers can you still perform on a patient requiring MILS?
Airway maneuvers, such as:
- Jaw thrust
- Chin lift
- Head tilt
These maneuvers still result in some cervical movement, so be careful
What must the anesthetist be prepared for with a patient requiring MILS?
Be prepared for a difficult airway
Decide ahead of time on DL or video laryngoscopy
What are CNS concerns during a pre-operative evaluation?
- Confusion
- Delirium
What are risk factors for delirium?
- Age
- ETOH use
- Preop dementia / cognitive impairment
What are triggers for delirium
- Hypoxemia
- Hypotension
- Hypercarbia
- Sleep deprivation
- Hypervolemia
- Infection
- Abnormal electrolytes
- Pain
- Admin of benzos and anticholinergics
When assessing for CNS concerns post-op what should you look for?
- Attention and awareness deficits
- Irritability
- Anxiety
- Paranoia
- Hallucinations
If a patient is non-cooperative, what type of anesthesia is contraindicated?
Regional anesthesia
What is the best part of planning?
“Do in preop what you plan to evaluate in postop” - Jose Castillo
What are preoperative respiratory concerns?
Age related
- Progressive decrease in PaO2
- Increased closing volume
- FEV1 decrease of 10% for each decade
Obesity
OSA
- STOP-BANG
What are preoperative cardiac concerns?
- Intermediate risk surgery (per ACC/AHA guidelines)
- Is preop cardiac testing necessary
- Stent placements (antiplatelet meds)
- Beta-blockers (continue meds)
- Initiate Beta-blockers if high risk (Target HR< 80 bpm)
What is the goal when deciding between regional and general anesthesia?
How can we decrease the risk of complications e.g.
- DVT
- PE
- Blood loss
- Respiratory complications
- Death
What is the goal when choosing regional over general and what are additional considerations?
Goal: Improved pain management
- Single shot vs indwelling cath
- Preemptive analgesia (blocks progression to chronic pain syndrome)
- Potentially increases participation in PT/OT
What fractures are fat emboli most common in?
- Pelvic
- Femoral
What is the mechanism of fat emboli formation?
- Long bone trauma
- Release of fat droplets into venous system
- Fracture releases mediators affecting the solubility of lipids in circulation
What are fat emboli known as in the anesthesia community?
Fat Embolism Syndrome (FES)
What is a common location for FES formation?
What is the incidence rate?
Mortality rate?
What are the symptoms and how soon do they present?
Location : Femoral medullary canal (IM rod)
Incidence: <1%
Mortality: 10-20%
Symptoms: Dyspnea, confusion, petechiae - Most definitive symptom
Present in 12-72 hrs
Lab findings of FES
- Fat macroglobulinemia
- Anemia
- Thrombocytopenia
- Elevated SED rate (Male: 0-22 mm/hr = normal)(Female: 0-29 mm/hr = normal)
Where can fat emboli obstruct?
End organ capillaries
What are fat emboli ideally metabolized into?
Free fatty acids
What can systemic inflammation from FES result in?
- Inflammatory cell invasion
- Cytokine release
- Pulmonary endothelial injury
- Pulmonary edema
- ARDS (<10% of cases)
What can respiratory insufficiency from FES result in?
- Mild hypoxemia
- Alveolar infiltrates
- Dyspnea
- Edema
- ARDS (<10%)
What are neurological symptoms from FES?
- Drowsiness
- Confusion
- Obtundation
- Coma
Where can petechiae from FES appear?
- Conjunctiva
- Oral mucosa
- Skin folds of chest, neck and axilla
What are minor symptoms of FES?
- Fever (>100.4 F)
- Tachycardia (>120 bpm)
- Jaundice
- Renal changes
What does treatment for FES include?
- Early recognition
- Stabilization of fracture
- Supportive management: 100% FiO2; no N2O
- Aggressive and early cardiopulmonary resuscitation
- Minimize stress response related to hypoxia, hypotension and decreased end-organ perfusion
- IV heparin (Not standard of practice)
When will symptoms of FES resolve?
3-7 days
Risk factors for DVT/PE
- Obesity
- > 60 yo
- Procedure length > 30 mins
- Use of tourniquet
- Lower extremity fractures
- Immobilization > 4 days
- No prophylaxis
What is DVT/PE rate of occurrence without prophylaxis?
40-80%
What ortho cases cause the greatest risk for DVT/PE?
- Hip surgery
- TKA
- Lower extremity trauma
What are the preventative measures against DVT/PE?
- Prophylaxis
- Early ambulation
- SCDs
- TED hose
- Less or no tourniquet use
- Periop anticoagulation
What is the initiation time for low molecular weight heparin?
- 12 hours preop
OR - 12 hours postop
How frequently can you dose neuraxial anesthesia when pt is taking LMWH once daily?
Neuraxial can be dosed 10-12 hours after previous dose of LMWH if pt is receiving once daily dose of LMWH.
Delay the next dose of LMWH to at least 4 hours after neuraxial administered
AS LONG AS THERE IS NO INDWELLING CATHETER
What is contraindicated with twice daily dosing of LMWH?
- Neuraxial catheter is “not okay”
- Remove catheter 2+ hours before 1st dose of LMWH
Is neuraxial anesthetic okay if on warfarin?
Yes, if INR </= 1.5
How soon can neuraxial anesthesia be performed after Aspirin/NSAIDS are stopped?
No special precautions with these drugs
How soon can neuraxial anesthesia be performed after Clopidogrel is stopped?
5-7 days
How does neuraxial anesthesia possibly help prevent DVT/PE formation?
- Increased lower extremity venous blood flow d/t sympathectomy
- Systemic anti-inflammatory properties of local anesthetics
- Decreased platelet reactivity
What procedures is tranexamic acid frequently used in?
How does TXA help in these procedures?
When do you administer?
- Procedures: Total knee & hip arthroplasty
- Decreases blood transfusion need
- Administer prior to incision
What is the IV dose for TXA?
10/15/30 mg/kg
MAX 2.5 grams
Risks with TXA administration
- VTE
- MI
- CVA
- TIA
TXA also causes hypotension if administered too fast.
What are the benefits of using a tourniquet?
- Decreased intraop blood loss
- Provides bloodless field
- Increased blood volume in central circulation
How soon does tourniquet pain begin after initiation?
45 minutes
How do you know what pressure to inflate the tourniquet to?
Thigh - Add 100 mmHg to SBP
Arm - Add 50 mmHg to SBP
Standards:
Upper extremity ~250 mmHg
Lower extremity ~ 300 mmHg
Generally, what length of time should tourniquet use not exceed?
What is the maximum time a touniquet can be used?
Generally not to exceed 2 hours
Max time ~ 3 hours
What are some of the possible negative effects of touniquet use?
- Hypercarbia
- Hyperkalemia
- Acidosis
- Tachycardia
- HTN
What should we document when tourniquet is being used?
- Inflation time
- Deflation time
- Total inflation time
- Inflation pressure and any adjustments
What are some of the risks of tourniquet use?
- Nerve injury
- Ischemia
- Rhabdomyolysis
- Mechanical trauma
How do we minimize risk of tourniquet use?
Deflating tourniquet every 20 - 30 minutes to allow for reperfusion
When using a double tourniquet, what should be kept in mind?
Inflate proximal first then distal
When the surgery is done, deflate distal first than proximal
What influences pain from tourniquet use?
- Tourniquet time
- Malposition or pressure
- Anesthesia technique
- Dermatomal spread / peripheral nerve coverage
- Local anesthetic and dose (density)
What does tourniquet deflation cause?
- Pain relief
- Decreased CVP, BP and temp
- Increased HR
- Transient lactic acidosis
- Transient hypercarbia
- Increased minute ventilation
