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

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

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

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)

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

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

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

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

The Aquarius Platinum by Edwards Life Sciences

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

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

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)

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

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

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

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

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

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

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

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

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

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

Check with Rachelle

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)

roberc1@gosh.nhs.uk

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

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?

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

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?