Chapter 18: Surgical Hemostasis Flashcards
How long can the abdominal aorta be ligated for?
30 mins
How long can the Portal triad (Pringle) be ligated for?
10-15 mins
How long can the Hepatic artery be ligated for?
30 mins
How long can the splenic artery and vein be ligated for?
15-20 mins
How long can the renal artery and vein be ligated for?
30 mins
Tourniquets over what pressure can cause demyelination?
> 1000mmHg - causing compression of nerves causing neurological deficits for up to 6 months postop
Tourniquet max time is?
1.5 - 2 hours due to ATP depletion
Two recommendations for applying a touniquet?
Use the widest one you can
Elevate the limb before application to help exsanguinate leg.
Exsanguination of the limb prior to tourniquet or with Esmarch is not recommended in what 2 circumstances?
Infection and/or neoplasia
What can reduce the risk of ischemic damage when using a tourniquet?
hypothermia
What are the three groups of hemostatic agents?
Mechanical agents, active agents and hemostatic sealants
What are possible complications of hemostatic agents?
volumetric swelling
exothermic reaction
foreign body reaction
inhibition of normal tissue healing
immunogenic reaction
When should hemostatic agents not be used?
in intravascular spaces
when blood salvage procedures are being used (autotransfusion - can get through the 40um filters)
How do mechanical hemostatic agents work?
Swell in response to bleeding and can be a matrix for clot to form on - rely on normal clotting
Do mechanical hemostatic agents inhibit healing?
They inhibit the healing of tissue edges of skin
Gelatin combined with what is more effective than gelatin on its own?
Thrombin
Which one collagen or gelatin actively promotes platelet aggregation?
Collagen
gelatin does not
How does gelatin reabsorb?
Via granulomatous inflammation with ingrowth of fibroblasts developing rapidly following placement of the sponge
How long in experimental studies do gelatin sponges take to absorb?
5 weeks
How can you tell if a gelatin sponge is what you see on advanced imaging or if it is a tumor?
Small little pockets of air in the foam
Bovine collagen is what type of collagen? How long does it stay there and how is it removed?
Type 2
8-10 weeks and is absorbed by fibroblast remodeling
what is the name of the cellulose used as a hemostatic agent?
Oxidised regenerative cellulose (ORC)
- unknown mechanism
- appears to form a large gelatinous clot
- works independently from coagulation pathway
- acidic properties may cause denaturing of blood proteins
Why might cellulose be a less effective hemostatic agent than others?
The acidic environment inactivates thrombin
Is cellulose bactericidal?
Yes
Against Gram - and Gram + aerobes and anaerobes
How long does resorption of cellulose take?
2-6 weeks
Name 3 mechanical hemostatic agents that are not gelatin/collagen or cellulose?
bone wax
ostene
polysaccharide spheres - dehydrate the blood
Alginates cannot be used in which environments and why?
In body cavities - they cause foreign body reactions
How does thrombin work?
Actively converts fibrinogen in blood to fibrin to create a clot (It’s Factor II)
Fibrin is what type of hemostatic agent?
Active - works independently from the patients own clotting pathway - derived from pooled human plasma
What is a concern with synthetic sealants?
How long to absorb?
They swell up to 400% - need to be used with caution next to vital structures
4-8 weeks
Antifibrinolytics are either lysine (EACA, tranexamic acid) or serine (aprotinin) protease inhibitors - which one is more potent and why?
Lysine is more potent as it binds more strongly to the plasminogen molecule
How does tranexamic acid work?
thrombin time prolonged and stabilizes clot - does not affect platelet number or normal coagulation times
Desmopressin is what? how does it work?
A synthetic analogue of arginine vasopressin that stimulates the release of factor 8 and vWF from endothelial cells
What are the main side effects of desmopressin?
antidiuretic effect causing hyponatremia and water retention
Ethamsylate improves what?
platelet adhesiveness and aggregation in the presence of vascular injury
- Also anti-inflammatory and improves blood flow in necrotizing pancreatitis
What is chitosan?
A natural biodegradable non toxic carbohydrate derived from deacetylated chitin from shrimp shells - it rapidly forms a gel-like clot on contact with blood
