Fluid and Transfusions Module 2

Question 1

How do the glyocalyx and subglycocalyx interact?

Answer 1

The glycolcalyx is a negatively charged gel like layer that plays a part in vascular permeability, coagulation and control of the microenvironment
- It is made of proteoglycans and glycoproteins

Beneath the glycocalyx lies the a small protein free subglycocalyx space
- Fluid between the subglycocalyx and plasma is though to be fluid flux determinant rather than the plasma and interstitial space = Revised Starlings Principle

Question 2

Briefly explain how RAAS activation helps with hypovolaemia?

Answer 2

Renin-Angiotensin Activating System

Angiotensin (Produced in liver) is activated in to angiotensin 1 by Renin (produced in the kidney and stimulated to production by low BP from baroreceptor in heart).

Angiotensin 1 is activated to angiotensin 2 within the circulation by ACEs
Angiotensin 2 works to increase water and sodium resorption and and mediates aldoesterone release fro the adrenal glands

Aldosterone works on proximal renal tubules to increase sodium resorption

ADH (vasopressin) released from the pituitary increase renal water retention and stimulates thirst

Question 3

What are types of colloids available and when can they be used and contraindications

Answer 3

1. HES (Hydroxyethyl starches) - most common, plant derived. Classified based on average molecular weight
2. Dextrans - bacterial fermentation of sucrose - not recommended for small animals patients
3. Gelatins - bovine collagen, shorter life than HES but the volume-expanding effects are similar - renal
4. Natural colloids - Whole blood or FFP/FP
   Human serum albumin used in ppl but very expensive and difficult to source so used for critically hypoalbuminaemic patients
5. Haemoglobin-based oxygen carriers
   for anaemic patients but also great colloid for expanding plasma

Main indication: Resus for hypovolaemic patients/haem
Contraindications: Renal injury, dose dependant coagulopathy and increase in mortality
Anaphylaxis
Leakage of molecules into spaces where bleeding is occurring
Contra-indicated in sepsis due to increased leakage due to leakage vessels

Question 4

When is cross-matching recommended and how is it done?

Answer 4

Determines serological compatibility between donor and recipient at that time point
- Donor cells mixed with recipient plasma and vice versa looking for agglutination

Cross matching when
- If previous transfusion >4 days dog, >2 days cat
- Unknown transfusion history
- History of transfusion reaction

Question 5

What are types of transfusion reactions possible?

Answer 5

Immunologic (antibody mediated) or non-immunologic and further into acute or chronic

Immunological:
- Type 1 Hypersensitivity: Urticaria (acute)
- Haemolytic reactions acute v. delayed
- Serological reactions - 4-14 days early
destruction of transfused cells
- Febrile non-haemolytic tranfusion reaction - acute

Non-immunological
- Resp reactions: fluid overload, TRALI
- Infectious disease transfusion
- Citrate toxicity - hypocalcaemia
- Hyperammonaemia (ppl)

Question 6

Risks and benefits of autotransfusion?

Answer 6

RISKS
Haemolysis - free Hb can result in AKI (poor blood collection)
Coagulopathy - dilution of clotting factors
Hypocalcaemia - citrate binds calcium

BENEFITS
No typing and crossmatching needed
Lower cost
Blood can be collected rapidly
Precious blood resources conserved
No risk of disease transmission or senstiziation to antigenic foreign proteins
No storage lesions