1. Handy Hints for Registrars
Continuous Veno- Venous
Haemofiltration
(CVVH)
Handy Hints for Registrars

2. Indications for CVVH
Children in ARF, tumourlysis syndrome, in born errors of metabolism
Main one on PICU is pre renal failure
When conservative management is no longer effective
Children with haemodynamic instability
Severe electrolyte imbalance, hypervolaemia, symptomatic metabolic abnormalities

3. CVVH
A procedure whereby solutes are removed by convective transfer and the large ultra filtered volume is replaced by a balanced electrolyte solution

4. Why CVVH
The use of pumps has the advantage of predictably allowing fluid to be removed
Continuous treatment allows constant adjustment of therapy
Well tolerated by patients with haemodynamic instability
Allows nutrition to be optimised (enteral or TPN)

5. The Basics Access Blood Commencing CVVH Housekeeping Trouble Shooting
Vascath
Blood
Commencing CVVH
Housekeeping
Blood tests
Ordering blood
Prescription chart
Trouble Shooting

6. ACCESS Age Size Length Priming Volume Child <10kg 6.5fr 10cms 15cms
Check clotting and correct if necessary
before putting in the line
ACCESS
Age
Size
Length
Priming Volume
Child <10kg
6.5fr
10cms
15cms
A=0.75ml V=0.78ml
A=0.81ml V=0.84ml
Child
<20kg
8fr
A= 0.80ml V=0.82ml
A=0.88ml V= 0.90ml
>20kg
11fr
25cms
A= 1.04ml V= 1.10ml
A=1.36ml V=1.42ml
Length of line depends on size and site of access.
After insertion flush with ‘heplock’.If line won’t be used for 1 hour
then must be flushed with heparin 1 in 1000 and labelled clearly

7. Access Vascath is line used at GOSH
Insertion as for any other central line.
Be aware of the priming volume.
Treat as for any other central line
Close observation of the site is essential.
X ray to confirm placement of vascath:
Sub-clavian
Neck lines
Neonates no neck line without discussion with consultant

8. Prior to going on
Check routine bloods have been sent to have a baseline
Make sure a cross match has been sent especially if child <10kgs
You should request an ADULT unit of blood – pedi pack is not enough volume
Blood should available in blood bank
X ray to confirm placement of vascath
Sub-clavian
Neck lines
Neonates no neck line without discussion with consultant

9. The Aquarius Platinum
by Edwards Life Sciences

10. The Filter and Priming Filter: Priming:
The machine is initially primed with 1 litre of 0.9%sodium chloride with 5000 units of heparin added
This is then followed by 500mls of 0.9%sodium chloride
Patient Size
Filter size
Priming volume
<5-15kg
HFO3
32mls
>15kgs
HFO7
54mls

11. The filter is hydrophyllic therefore
the machine can be primed a
Couple of hours before you need it
and can re-circulate. This can
lengthen the life of the filter

12. Priming
For any child <10kgs a blood prime should be used as the volume of the circuit is 100mls. The blood should only be run through the circuit immediately before going on CVVH in case there are any problems with access etc
In certain situations the need to start CVVH may override the need for a blood prime (in hyperkalaemia or other metabolic emergencies) discuss with consultant and nurse in charge
If this is the case the child can go on CVVH and blood transfusion can be given shortly after
Check daily that blood is available especially if there have been problems with the filter (generally in infants)

13. If you don’t want a heparin bolus Please inform the CVVH nurses
Commencing CVVH
The nurses will inform you that they are going to start CVVH
There will be 2 nurses, one for the patient and one for the machine
Ensure fluid boluses are ready
Increase inotropes as necessary
Increase oxygen as necessary
Heparin bolus 20 iu/kg dependent on patients condition
If you don’t want a heparin bolus
Please inform the CVVH nurses

14. Pump Speed Weight Initial pump speed Suggested pump speed
Is dependent on the weight of the child
Start off slowly and then gradually increase until desired speed is achieved as tolerated by the patient
Weight
Initial pump speed
Suggested pump speed
0-5kg
15ml/min
Up to 50ml/min
5-10kg
25ml/min
Up to 75ml/min
10-20kg
50ml/min
Up to 100ml/min
20-30kg
75ml/min
Up to 150ml/min
Over 30kg
Up to 200ml/min

15. Once satisfied the patient is tolerating the pump speed then the turnover and fluid loss programmes can be set and started

16. Pre-dilution or Filtration Fraction
Turnover is set usually between 5-15% but in certain circumstances up to 30% can be used safely (tumourlysis syndrome, metabolic problems)
Represents the percentage of ultra filtration fluid that is removed from the blood passing through the filter every hour

17. Substitution /Replacement Fluid
Primary function to remove solutes via convection
Is pre-filter, to lengthen the life of the circuit
One type used at GOSH. Can have extra potassium added if needed to a maximum of 5mmols per litre
Accusol
For all patients
Suitable for patients with severe metabolic acidosis
For patients in liver failure
Bicarbonate based solution
Comes in plain bags and bags with added potassium
Pre mixed: 2mmols & 4mmols per litre

18. Fluid Loss The programme is set on an hourly basis
The nurse will have calculated all the fluids (including, infusions IV antibiotics, and feeds or TPN going into the child) over a 24 hour period.
This is divided by 24 to get the hourly total
Decide with the consultant what fluid balance they would like to achieve in 24 hour period. (Andy Petros - 3 litres negative by the morning!)
Use of inotropes to maintain blood pressure in order to remove fluid – again discuss with consultant

19. Fluid loss…
Child has 360mls of infusions, drugs and feed going in in 24 hours. Therefore every hour 15mls is going in to the patient. For an even balance the machine would be set to take off 15mls per hour
If we want the child negative 10mls per hour then the machine would be set to take off 25mls per hour
Other things to think about, if you are giving FFP, blood, etc to correct numbers then remember, that fluid can be taken off as it’s going in to prevent a positive fluid balance

20. Setting the programme Every cycle should be set for 4 hours
To allow for re calculation of fluids (if having FFP or other blood transfusions)
To prevent errors

21. Heparin The circuit is heparinsed to prolong the life of the filter
Is delivered pre-filter
ACT’s are measured post filter
Aim to keep them unless patient is bleeding then
Or sometimes don’t use at all

22. Daily Housekeeping
Check if the child needs any blood cross matching and ordering
Check the CVVH prescription chart
Check fluid balance
Check U&E’s
Check phosphate levels (Has an affinity to the filter) and commence infusion if necessary. Also if the filter is old and less effective the phosphate level could increase
Maximise the patient’s nutrition whether TPN or enteral
Did you know that the venous (return line)
can be used for administration of TPN
or other infusions if access is a problem

23. Check with Rachelle

24. Trouble shooting Access U&E’s not clearing as well Clotting
if the vascath is positional or one or both of the lumens are difficult to aspirate then it might need re-positioning
U&E’s not clearing as well
Check how old the filter is, if it has been going for a few days it may need to be electively changed
Could the filtration fraction be increased
Clotting
If the child is coagulapathic then heparin does not have to be used, although this could shorten the life of the filter
Have to balance between the risk of bleeding and the risk of loosing the filter. Especially in very small infants (<5kgs as the pump speed is so slow)

26. References Dykes M, Ameerally P (2002) Anatomy. 2nd edition.
Guyton AC, Hall JE (2006) Textbook of Medical Physiology. 11th edition.
Hazinski MF (1992) Nursing Care of the Critically Ill Child. 2nd edition

27. 3.5kg baby with metabolic condition ammonia at dangerously high level.
What would the pump speed be?
Would you do a blood prime?
What would the filtration fraction be?
What would you set the fluid loss, even negative, or positive?

28. 20kg child. MoF on multiple inotropes. ARDS 3L +ve. Fluids 50mls hour
What would the pump speed be
What filtration fraction would you set
How would you calculate the fluid loss

29. 30kg child. Tumourlysis Syndrome. Hb 7.5. K+ 6.3 Fluids 50mls hour.
What would the pump speed be
What filtration fraction would you set?
Would you do a blood prime?
Would you set the child on an even, positive, or negative fluid balance?