Vascular Anesthesia Pt.1 (Exam I) Flashcards
What comorbidities are typical of “vasculopaths”?
- DM
- HTN
- CRI
- COPD
>50% have CAD.
Heparin is a naturally occurring anticoagulant produced by ______ and ___ ____.
basophils & mast cells
What does heparin directly bind to?
Antithrombin III
What is the consequence of heparin binding to antithrombin?
Enhances antithrombin by 1000x to inactivate factors 9, 10, 11, & 12.
What are the the three mechanism of actions of heparin?
- Binds to Antithrombin
- Inhibits thrombin
- Inhibits platelet function
What occurs when heparin inhibits thrombin?
Thrombin won’t active factors 5 & 7
Is heparin technically a direct anticoagulant?
No. Binds to Antithrombin which is a direct anticoagulant.
Heparin is _______ lipid soluble.
poorly
Does heparin cross the placenta?
no
How is heparin absorbed in the GI tract?
poorly
No PO formulation.
What conditions/factors will potentiate heparin’s anticoagulant activity?
- Hypothermia
- Liver dysfunction
- Kidney dysfunction
What will occur with heparin administration if circulating plasma protein concentrations are low?
Heparin won’t be bound and will be more active
What occurs with the vasculature when heparin is administered?
Vascular smooth muscle dilates
↓ MAP, PAP, SVR.
What is the most common, serious complication that occurs with heparin usage?
Hemorrhage
Especially higher if patient is already on ASA.
A platelet count of < 100k with concomitant heparin administration might be indicative of….
Mild HIT (Heparin-induced Thrombocytopenia)
What are the characteristics of severe HIT (Heparin-induced Thrombocytopenia)?
- PLT <50k
- IgG antibody formation
Severe HIT occurs _____ days after heparin initiation typically.
5 - 10 days
Mild HIT typically occurs ________ after initiation of therapy.
Within hours to 15 days
How do IgG antibodies neutralize toxins, viruses & bacteria?
IgG antibodies opsonize (bind) to foreign pathogens & make them targets for phagocytosis.
Where does IgG bind to on platelets?
FC receptor on platelet surface
What are the results of IgG binding to platelets?
- PLT activation
- PLT release of pro-thrombotic substances (like thrombin)
- Activation of more PLTs
What is the typical dose of heparin for vascular cases?
1mg/kg = 100u/kg
What is a normal aPTT?
30 - 35s
What is target aPTT for vascular cases?
~ 60 seconds
Goal is 1.5 - 2.5x normal.
What is normal ACT?
90 - 120seconds
What is protamine derived from?
Salmon sperm
how about that
What is the mechanism of action of protamine?
Protamine = (+) charged alkaline
Heparin = (-) charged acidic
neutralize each other.
What is the typical vascular surgery dosage of protamine?
1mg Protamine per 1mg of Heparin given
What clears protamine?
Reticular endothelial system
Protamine is cleared _____ than heparin.
faster
Which patient groups are more susceptible to protamine allergies?
- Patients with protamine insulins (NPH insulin)
- Vasectomy hx
- Fish allergy hx
What drug would be given for heparin reversal in a patient who is allergic to protamine?
PLT Factor IV
What is a rare pulmonary adverse effect associated with protamine administration?
Pulmonary Hypertension
Protamine induced pulmonary hypertension is mediated by the release of ______ and ______.
thromboxane & serotonin
How can protamine induced pulmonary hypertension be pre-treated?
COX inhibitors (indomethacin, aspirin, etc.)
Renal disease is usually noted when GFR drops below….
25 mL/min
Patients become dialysis dependent when GFR drops to _____ mL/min.
10 mL/min
What metabolic abnormalities (mentioned in lecture) are typically of kidney patients?
- ↑ K⁺
- ↑ Mg⁺⁺
- ↓ Ca⁺⁺
- ↓ Albumin
- H₂O & Na⁺ retention
- Metabolic acidosis
What Hgb might be typical for a renal patient?
6 - 8 g/dL
How does V̇T change in renal patients?
Minute ventilation will increase to offset metabolic acidosis
What adverse cardiac changes occur in renal patients?
- ↑CO
- HTN
- CHF
- Dysrhythmias
What GI issues with renal patients are of special consideration with anesthesia?
- Hypersecretion of gastric acid
- Delayed gastric emptying
Consider RSI.
What are the “pros” of native vessel AV fistulas?
- Long-term patency
- Low infection rate
What are the “cons” of a native vessel AV fistula?
- Maturation time (6 weeks)
- May require multiple operations
What are the “pros” of AV grafts?
- Shorter maturation time
- Typically only one operation
What are the “cons” of AV grafts?
- Doesn’t last
- Prone to infections
- Clotting is common
Why is LR often avoided in renal patients?
Contains K⁺
When would NS be avoided with a renal patient?
If the renal patient is already:
- Hypochloremic
- Acidotic
NS will worsen both of these things
Which anesthetic drugs will have an increased effect due to decreased serum protein binding in renal patients?
- Etomidate
- Barbiturates
- Benzo’s
What are clinical indications for elective revascularization surgery?
- Claudication
- Ischemic pain (at rest)
- Gangrene (possibly emergent if bad enough)
What causes claudication?
Ischemic pain due to muscle metabolic requirements from movement.
Pain when active, relief at rest.
What is an ankle/brachial index study?
Comparison of systolic pressure in the arm vs the ankle.
Ankle systolic ÷ Arm systolic = ABI
What is a normal ankle/brachial index?
1.0 - 1.4
At what ankle/brachial index is pain at rest likely to occur?
0.4
At what ankle/brachial index is gangrene likely to occur?
0.25
What ABI (Ankle-Brachial Index) values are indicative of moderate disease & severe arterial disease?
Moderate = 0.5 - 0.8
Severe = < 0.5
What are the five mainstays of PAD treatment?
- Stop smoking
- Maintain normoglycemia
- Maintain normotension
- Antiplatelet therapy (ASA or ASA/Plavix)
- Revascularization Therapy (stents, surgery,etc)
What drug class is protective for atherosclerotic patients at risk for cardiac disease?
Βeta blockers
Is success more often seen in Iliac artery stenting or in Femoral/Popliteal artery stenting?
- Iliac artery stenting is more successful
- Thrombosis/restenosis is common in femoral/popliteal arteries.
When are synthetic grafts indicated over insitu (saphenous vein) grafts?
Large vessel revascularization (aorta-femoral, femoral-femoral, etc.)
Which coagulation factors are part of the intrinsic pathway?
8, 9, 11, and 12
Which coagulation factors are a part of the extrinsic pathway?
3 and 7
Which coagulation factors are a part of the common pathway of the coagulation cascade?
1, 2, 5, 10, and 13
