Blåt fag Modul 1 Flashcards
What is Heparin and where is it found in the body
Heparin is a fast acting anticoagulant drug.
It is found in mastcells in the lungs, liver and connecting tissue around the blood vessels.
What is heparin derrived from
It is derrived from either bovine or porcine lung and gut tissue
How does heparin work?
Heparin activates AT3, which inhibits thrombin activity.
What is the half life of heparin
1-2.5 hours
Where is heparin Metabolised
Mostly in the liver, and a little by kidneys
If the patient has a decreased liver function, how will that affect the metabolism of heparin
It will decrease the clearence of heparin. Half time is prolonged.
How much affect does heparin have on AT3?
It affects the activation of AT3 by 1000 fold
When is heparin used
It is used pre-bypass (by the anesthesiologist), in the priming solution, and during CPB
How much heparin is given pre-bypass
300-400 IE/kg
What should the ACT be, before going on by-pass?
480
How much heparin should be given in the priming solution (according to the recommendations)
5000 IE/L
What other tests can be used to monitor coagulation
- POC (hemocron jnr.)
- Hepcon - (Protamine titration assay)
- Heptem - (Heparin effects on the hemostasis)
- TT - Thrombin time
- APTT - APTT can not be used when there are high levels of heparin in the plasma
Can you go on by-pass without heparin
No! Because the oxygenator and pump will clot.
Can you cannulate without heparin
No, heparin needs to be given before, otherwise the coagulationsystem is activated.
What is protamin?
Protamin inhibits heparin
How does protamin work
Protamin binds to heparin, making it release AT3
How long is the half life of protamin
About 5min
How much protamin is used to reverse the effects of heparin
2mg/kg
What allergy is important to know before giving protamin
If the patient has a fish or shellfish allergy, because protamin is derrived from fish (salmon) semen.
What happens in an allergic reaction to protamin
You will get an anaphylactic reaction
- Pulmonary hypertension
- Oedema
- Systemic hypotension
- Vascular restriction
Who is most prone to get an allergic reaction from protamin
people with prior protamin exposure and people with fish/shellfish allergies
How is an allergic reaction by protamim treated?
Stop giving protamin!
- 100% O2
- Fluids
- Steroids
- Antihistamines
- vasodialators
- Bronchodialators
When is protamin given
Post by-pass, by the anaestethic team
When test dosis is given, you turn of the last suctions.
How is the effect of protamin measured
By returning the ACT or APTT to the pre by-pass baseline
Can you go back on by-pass after protamin is given
Yes, but a new full dose of heparin must be given, and the ACT is at the required limit according to guidelines
What happens if protamin enters the CPB circuit
It will clot rapidly.. Or not at all. It is very dangerous.
Mention other coagulation disturbances
- Cold agglutinins
- Haemophilia
- DIC (dissiminated intravscular coagulation)
- HIT (Heparin induced thrombopeni)
How do you keep fluid and electrolyte homeostasis in CPB (3)
- Restricting hemodilution
- Minimizing the circuit (shorten tubes)
- Use VAVD
What scenarios makes the perfusionist “mess up” the homeostasis
- Hypovolemia (lack of volume)
- Poor venous drainage
- Blood loss
- Hemodilution
- External suctions or cellsaver
What is homeostasis
It is where the body is in a balanced state internally
Where are possible placements of venous catheters
- single stage in the right atrium (atrial)
- Two stage in the vena cava (cavoatrial)
- Bi caval with 2 single two stages
- In the femoral or iliac vein.
What size are cannulas and catheters given in
In outer diameter!
Does a high pressure drop create greater or lower resistance to flow? (delta P)
A high pressure drop means a smaller inner diameter and therefore equals a greater resistance to flow
What determines pressure drop
Pressure drop is the difference between the fluid entering the cannula and the fluid leaving the cannula.
What different types of drainage are there
- Syphon - Gravity
- KAVD - Kinetic assisted venous drainage
- VAVD - Vaccum
How low should the venous reservoir be placed under heart lvl in cm?
around 40-70 cm
What is syphon drainage dependent on
- CVP (central venous pressure
- Cannula size, tubing, connectors and resistance
- Height difference
- volume of air in tubing
- Intravascular volume
What can cause chattering?
- Inadequate blood volume
- Excessive siphon drainage
- Venous walls collapse against cannular openings.
What can help correct chattering?
- Venous line resistance
- Repositioning catheter
- Give inotropes to increase muscle compliance
What does VAVD do?
It creates a slight negative pressure in the venous reservoir.
This “pulls” blood to the venous catheter and then to the reservoir.
Mention advantages of VAVD
- Smaller catheters
- Reduced tubing dimensions (less priming volume)
- Possibly better venous drainage, and improved venous drainage in special procedures.
- Better visability in the operating field
- Prevents air locks
What are some of the disadvantages of VAVD
- Possible transmission of gaseous micro-emboli from venous line to arterial side of circuit
- Over pressurization of venous reservoir!!!
- Collapse of vena cava (chattering and possible damage interior wall structure)
- Amplification of venous air (microbubbles)
Can you use any kind of reservoir for VAVD?
No, only an open (hardshell) reservoir.
What should you be aware of when using VAVD (4)
- Use as little as possible
- Start only if syphon can drain up to a 75% flow
- No substitution for poor cannulation, small catheter and position
- Always turn VAVD off before filling the heart
What describes KAVD
It is kinetic assisted venous drainage. There is a pump (roller or cetrifugal) in front of the reservoir that actively draines the blood from the heart.
What is MIECC
Minimally invasive extra corporale circulation
???
What are important cardiac electrolytes?
Na+, Ka+, Cl-, Mg2+, ca2+
Name the 3 types of fluid categories and where they are
- Intracelluar fluid, which is inside the cells.
- Interstitial fluid which is inbetween the cells
- Intravascular fluid which is fluid in the vascular system (plasma)
2 and 3 are also called extracellular fluid
What fuid type concentrations do we mostly work with/occurs
Isotonic and hypertonic.
equal concentration between non-permeable solutes compared to another solution.
A solution that has a greater concentration of non-permeable solutes compared to another solution.
Why do we prime?
- Deair CPB circuit
- Contain fluid continuity between patient an CPB circuit
What is a crystalloid?
It is a fluid with small water soluble molecules, such as Ringer’s lactate.
What is a colloid?
It is a fluid which contains larger molecules, such as proteins (albumin)
What are the advantages and disadvantages of crystalloids?
- The are inexpensive, low incidence of adverse effects.
- Short lived hemodynamic (half life 20-30mins). Chance of peripharel and pulmonary oedema.
What are the advantages/disadvantages of colloids?
- To maintain or increase plasma concentration. Intravascular 3-6 hours. Prevents oedema.
- Derrived from human plasma, therefore higher risk of allergic reactions
- Caution with patients with increased intravascular permeability (sepsis, trauma, burn)
- Can cause weak anticoagulation effects - though not significant if under 25% of volume.
What is pRBC
Packed red blood cells
How do you determine which priming fluid/fluids you use
- All about the patien
- Hct
- Other conditions including function of liver and kidney
- Cardic function
- Type and duration of surgery
What should you be awere of when using Ringer’s lactate
Lactate is a source of bicarbonate. Be aware of patients with diabetes, as lactate may be converted to glucose (via the gluconeogenic pathway)
How much prime solution should be used?
300-1700ml (paed-adult)
How can you reduce priming volume? and volume in generel
- Useing RAP and VAP. Retrograde autologous prime and venous ….
- Downscaling tubings
- VAVD
- Useing colloids
- Blood cpl
- Microplegia (needle directly in the heart)
- Reduce flow (cooling)
- Reduce targeted Hct
Can you just have an empty vein line?
No! this creates microbubbles!
Prime checklist pre-bypass
- Temperature (37oC)
- pH is neutral in prime solution
- Hct - asses need for blood prime or pRBC
How do you calculate EBV by weight
Weight x 7% for females
Weight x 7,5% for males
It gives you ml/kg
What factors can affect EBV
- Obesity/underweight
- Muscles
- Cardiac incompensation (incompetent mitral valve f.exp.)
- oedema
- Diuretics
What is hemodilution?
A dilution of erythrocytes or other blood elements, which results in an increase in plasma volume
Why is hemodilution used?
To lower the Hct to avoid thrombosis and avoid high pressure and clotting in CPB circuit
What are some benfits of hemodilution (5)
- Decrease blood viscosity
- Improved microcirculatory bloodflow
- Increase regional blood flow
- Increase oxygen delivery to tissues
- Reduce risk of hypertension during higher pump flows
Factors affecting Hct before, during and after CPB
- Weight and sex
- Pre operative anemia
- CPB circuit and prime volume
- Pre CPB blood loss
- Pre CPB volume distribution
- Cpl volume
- Added prime to maintain flow
What is critical Hct threshold?
> 25%
What factors can affect the need for added volume? (4)
- Urine output
- Bleeding
- Oedema
- Perspiration
How do you calculate the estimated hct on bypass
Calculate EBV (weight x7/7,5%) (or nadler’s equation)
Then calculate Hct2 = (Hct1xEBV) / (EBV+PrV)
How do you calculate required donor blood?
- You need a desired Hct (Hct3)
- Calculate EBV (weight x7/7,5%) (or nadler’s equation)
- Calculate Hct2 = (Hct1xEBV) / (EBV+PrV)
- Calculate dbV = (hct3-hct2)(prv+EBV) / (hctD-hct3)
What are the normal range of
1. Creatinine
2. eGFR
3. Glucose
4. APTT
- 60-105 micromol/L, lidt lavere for kvinder
- > 90 normal < 60 nedsat
- 4-7 fastende
- 30-50 sec
What does a high lvl of creatinine mean
You have decreased kidney function
Where would you place pressure trancdusers on your circuit, and why?
Pre/post oxygenator, and for cpl.
- Pre oxy to ensure oxy is not clotting
- post oxy to ensure right placement of arterial cannula
- cpl. to ensure right pressure when giving cpl.
- If you are yousing VAVD you could place a trancduser to measure the reservoir pressure
How do you calculate the dose of heparin based on weight.
300-400 IE/kg
exp. W=85kg, hep dose = 85x300 = 25500IE
What should the ACT be for cannulation?
?
Why do you use blood cpl
To minimize extra fluids. Specifically crystalloids.
What is the start dose of cpl?
If you use blood cpl the start dose is 1000ml in a ratio of 1:4 (blood:cpl) - redose every 20min with 300ml in a ratio of 1:8
If you use servator or similar the start dose is 1400ml (?) this last for about 2 hours)
Why would you recieve a high cpl pressure alarm
?
How do you see if the cpl is effective
The heart will arrest within 30-40 sec.
???
What is your minimum SvO2?
65%-70%
What are the temperaturegradients for 1. venous-arterial blood
2. venous blood - HCU water
- 5oC
- 8-10oC
Or 10oC pr. hour
What could happen if you warm the patient to quickly?
You can extract airbubbles in the blood, if the temperature difference is to big
What does hypertropich mean
Enlarged - Example hypertropich left ventricle - enlarged left ventricle
What is hypOvolemia?
A state where the body is missing extracellulare fluid
Calculate BSA simple method
(H+W-60)/100
Calculate EBF
2.4xBSA L/min
What is preload
The preload refers to the amount of blood already in your ventricles when you’re ready to pump it out
What is afterload
the afterload refers to the pressure against which your heart has to pump the blood
What is an inotropic drug
A drug that tells your heart to contract more or less
