Handy Hints for Registrars

1. 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 • Vascath • Blood • Commencing CVVH • Housekeeping • Blood tests • Ordering blood • Prescription chart • Trouble Shooting

6. Check clotting and correct if necessary before putting in the line ACCESS 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

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. 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 • 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

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 180-200 unless patient is bleeding then 160-180 • 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 • 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)

25. roberc1@gosh.nhs.uk

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 • http://en.wikipedia.org/wiki/tumor_lysis_syndrome • http://www.purchon.com/biology/osmosis.htm

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?