Peripheral Vascular Anesthesia Flashcards
1
Q
Over 50% of Vasculopaths have this comorbidity.
A
CAD
2
Q
Heparin is a naturally occurring anticoagulant produced by ____ and _______.
A
- Basophils
- Mast Cells
3
Q
What does heparin bind to?
A
- Antithrombin III
4
Q
What happens to AT III when heparin is bound to it?
A
Enhances 1,000x the ability of AT III to inactivate thrombin and factors XII, XI, IX, X
5
Q
Heparin will also inhibit thrombin activation of what factors?
A
- Factor V
- Factor VII
6
Q
Heparin’s effect on platelet function
A
Inhibits platelet function
7
Q
What factor does heparin effect on the extrinsic pathway?
A
Factor VII
8
Q
What factor does heparin effect on the common pathway?
A
Factor V
9
Q
Lipid solubility of heparin?
A
Poorly lipid soluble
10
Q
GI absorption of heparin?
A
Poorly absorbed in the GI Tract
11
Q
Does heparin cross the placenta?
A
No
12
Q
Heparin’s anticoagulation increases in intensity and duration with increasing ________.
A
Doses
13
Q
Heparin’s anticoagulation increases in intensity and duration with decrease ________, _____, and _______.
A
- Temperature
- Hepatic dysfunction
- Renal dysfunction
14
Q
CV side effects of heparin
A
- Relaxation of vascular smooth muscle
- Decreased MAP, Pulmonary arterial pressure, SVR
15
Q
What is the most common side effect of heparin?
A
Hemorrhage
16
Q
What is mild HIT due to?
A
Platelet aggregation
17
Q
Plt count for mild HIT?
A
<100,000
18
Q
When will mild HIT begin?
A
Appx 15 days after initiation of heparin therapy
19
Q
What is the plt count for severe HIT?
A
< 50,000
20
Q
When will severe HIT begin?
A
5-10 days after initiation
21
Q
What antibody is formed with severe HIT?
A
IgG
22
Q
What are the normal functions of IgG?
A
- Neutralize toxins, viruses, and bacteria
- Opsonize them for phagocytosis
23
Q
How does IgG react with HIT?
A
- lgG will bind to receptor on platelet
- Lead to platelet activation
- Activated platelets release pro-thrombotic substances (such as thrombin)
- IgG activates more platelets
Key Takeaway: IgG antibodies in HIT cause the platelets to stick together and form clots
24
Q
Heparin dose for Vascular Surgery
A
100 units/ kg
25
Normal aPTT and Heparinized aPTT
* Normal aPTT: 30-35 seconds
* Heparinized aPTT: 60-70 seconds
26
Normal ACT
90-120 seconds
27
When will you draw an ACT during a vascular surgery?
* 3 minutes post heparin injection
* repeat q 30 mins to 1 hour
28
What is the half life of heparin?
1-2 hours
29
Reversal for heparin
Protamine
30
Where can protamine be naturally found?
Salmon Sperm
31
MOA of Protamine
Protamine is a positively charged alkaline that combines with negatively charged (acidic) heparin
32
How is heparin naturally cleared in the body?
* Reticuloendothelial system (RES)
* Protamine clears heparin faster
33
What is the dosage of protamine?
1 mg of protamine / 100 units of heparin
34
Most common side effect of protamine
Hypotension d/t histamine release
35
Who might be allergic to protamine?
* Pt on chronic protamine insulin
* Vasectomy
* Fish allergies
36
What reversal alternative can be used for patients undergoing vascular surgery if they are allergic to protamine?
Platelet factor 4
37
What is a rare side effect of protamine?
Pulmonary Hypertension which will lead to pulmonary vasoconstriction, pulmonary edema, and hypoxia
38
Pulmonary HTN from protamine is due to the secretion of ______ and ______.
* Thromboxane
* Serotonin
39
If a patient is prone to pulmonary hypertension secondary to protamine what can be given as pre-treatment?
Cyclooxygenase Inhibitors (Indomethacin or ASA)
40
At what GFR will symptoms be noted?
< 25mL/min
41
What what GFR will a patient be dialysis dependent?
< 10 mL/min
42
Most ESRD patient have their multisystem side effects controlled with _______.
Renal Replacement Therapy
43
What are the metabolic abnormalities of ESRD?
* Hyperkalemia
* Hypermagnesemia
* Hypocalcemia
* Hypoalbuminemia
* Water and sodium retention
* Metabolic acidosis
44
Hgb of ESRD patients
6-8 g/dL
45
CV complication of ESRD
* Increased cardiac output
* HTN/CHF
* Arrhythmias
46
What is the increase minute ventilation of ESRD patients due to?
Increased minute ventilation to offset metabolic acidosis
47
GI complications of ESRD
* Nausea, vomiting, ileus
* Hypersecretion of gastric acid
* Delayed gastric emptying
48
Neuro complications of ESRD
* Lethargy, confusion
* Peripheral neuropathies
49
Pros of AV Fistulas
* Best long-term patency
* Lowest rate of infection
* No foreign material used
50
Cons of AV Fistulas
* Requires a longer “maturation” time (6 weeks or more)
* May require more than one operation to create a functional dialysis fistula
51
Pros of AV Grafts
* Shorter time required for “maturation”
* Usually requires only one operation
52
Cons of AV Grafts
* Does not last as long
* More prone to infections…complete removal
* Embolectomies/revisions
53
Anesthesia Pre-op Considerations for AV Fistulas/ AV Grafts
* Day of surgery dialysis
* Address cardiac/pulmonary issues
* Consider ABG’s
* EKG
* Bleeding time/Coag studies
* BUN, creatinine
* Manage aspiration risk, hyperglycemia, hyperkalemia
54
Anesthesia Intra-op Considerations for AV Fistulas/ AV Grafts
* Access arm/blood pressure cuff
* Consider invasive monitoring with uncontrolled HTN
* Consider RSI for GA
* Decrease dose of induction agents if hypovolemic/unstable
* Maintain cardiac output
* Adequate ventilation: spontaneous/controlled to prevent hypercarbia
55
What fluids are usually preferred for ESRD patients?
Isolyte
56
When would LR be avoided for ESRD patients?
If the patient is hyperkalemic
57
When will NS will be used for ESRD patients?
If the patient is hypochloremic and alkalotic
58
What drugs will have an increased effect on ESRD patients due to decreased protein binding?
* Etomidate
* Barbiturates
* BZD
59
What drugs will have an increased effect on ESRD patients due to elimination concerns?
* Opioid metabolites
* Anticholinergics
* Metoclopromide
* H2 blockers
* Pancuronium
* Neostigmine
* Suggamadex
60
What fraction of PAD patients are over the age of 75?
two-thirds of PAD population
61
Clinical indication for revascularization surgery
* Claudication
* Ischemic rest pain
* Gangrene (may be considered emergent d/t potential limb loss)
62
Anesthesia Pre-op considerations for revascularization surgery.
* History/Physical Assessment (CAD/COPD/CKD/DM)
* Decreases or absent pulses
bruits
* Intermittent claudication
* Rest pain
* Hair loss
* Temperature change
* Doppler ultrasound
* Ankle/brachial index
* Angiography
* Consider Type and Cross
63
Ankle-brachial index formula
SBP at ankle / SBP at arm
64
Ankle-brachial index for rest pain
0.4
65
Ankle-brachial index for impending gangrene
0.25
66
Normal Ankle-brachial index
0.9-1.4
67
What does an ankle-brachial index > 1.4 indicate?
Calcification/ Vessel Hardening
68
Ankle-brachial index that indicates severe arterial disease
Less than 0.5
69
Treatment of PAD
* Stop smoking!!!
* Normalization of blood sugars
* Treatment of hypertension
* Antiplatelet therapy
* Revascularization
70
What are the types of revascularization procedures?
* Angioplasty
* Stenting
* In-situ bypass
* Synthetic bypas
71
PAD patients requiring angioplasty and stenting through these arteries have a high success rate.
Iliac arteries
72
PAD patients requiring angioplasty and stenting through these arteries have a low success rate and are prone to restenosis.
Femoral/popliteal arteries
73
How long does a revascularization stent last?
10 years
74
Regions that warrant an in situ bypass
* Femoral-popliteal
* Femoral-tibial
75
Regions that warrant a synthetic graft bypass
* Aorta-bifemoral
* Axilla-bifemoral
* Femoral-femoral (fem-fem crossover)
76
Anesthesia Intraop consideration for Femoral-popliteal and Femoral-tibia bypass.
* Few concerns
* Little blood loss
* Sometimes heparin is not reversed
* 45 minute procedure
77
Anesthesia Intraop consideration for Aorta bi-fem/Axillo bi-fem/fem-fem crossover
* Type and cross
* Large bore IV access
* Central line/SVV monitoring
* Large blood loss may occur
* Heparin often redosed and usually reversed
* 2-4 hour procedure
78
Anesthesia Post-op Concerns for Revascularization Surgery
* Sudden loss of pulses
* Sudden temperature change
* Complaints of numbness/paresthesia
* Loss of motion/sensation
