7 CRRT deliveryCVVH is convective, use replasment fluid ( lood side of the filter)CVVHD is diffusive, use dialysate fluid (opposite side of the filter)There are no convincing clinical data to support either CVVH or CVVHDCombination therapy; CVVHDF is also not supported by evidenceHow fluid is delivered has little impact on the composition of the fluidThe replacement and dialysate fluids should have the same composition to reduce staff confusion and the risk for error
8 Options for fluids in CRRT Custom fluids compounded by the pharmacy- The complications of compounding include increased cost and a shorter shelf life (usually 30 days).Commercially prepared fluids with additives- K, P, Mg and even bicarb can be added as needed but, carries the risque for pharmacy errors and may increase costs.- Whether replacement fluid or dialysate is utilized, the fluid should be ultrapure and sterile.- Each time an additive is injected, this is associated with a chance of human error; contamination; wrong dose; wrong syringe, wrong vial etc.Commercially prepared pre-mixed fluids- The safest approach. Less expensive and have longer shelf life.- Available from multiple manufacturers, generally 3 l and 5 l bags with a discrete number of fluid compositions.- The most common concentrations of these solutes are equal to normal plasma levels
9 Evaluation of Errors in Preparation of CRRT Solutions Survey of 3 Pediatric Listserves:Pediatric Critical Care, Nephrology, CRRT16/31 programs reported solution compounding errorsConsequences of improper solutions2 deaths1 non lethal cardiac arrest6 seizures (hypo/hypernatremia)7 without complicationsBarletta et al, Pediatr Nephrol. 21(6):842-5, 2006 Jun
10 PD solutions are not recommended PD solutions are not recommended! because of the risque of hyperglycemia and metabolic acidosis
11 Replacement fluids:Are directly given in to the blood pre- or post filterThey are used to increase the amount of convective solute removalDespite their name, replacement fluids do not replace fluid.Fluid removal rates are calculated independently of replacement fluid rates
12 Predilution: Postdilution: Lower solute clearance, Higher ultrafiltration rateLarger filter surface areaReduced sludging and need for anticoagulationUse of pre-filter replacement fluids invalidate post-filter lab drawsPostdilution:Higher filtration fraction
13 Fluid Composition Sodium Should be in the physiologic range (140 meq⁄l).Customization needed if hypertonic citrate for anticoagulation is usedCVVHDF is more likely to achieve serum sodium concentrations within the normal range than CVVHSupraphysiological sodium concentration in the dialysate or replacement solutions would improve the hemodynamic stability or prevent the increase in intracranial pressure, but there are no conclusive data concerning this issue.
14 PotassiumK concentrations between 0 to 4 meq⁄ l are acceptable and commercially available.Most patients have a degree of hyperkalemia at initiation of RRT therapy.If K free fluid is used, careful monitoring is necessary.In cases of severe hyperkalemia associated with arrhythmia and⁄or hemodynamic collapse hemodialysis should be utilized.
15 CalciumAbout 60% of total plasma calcium is ultrafilterable, substitution fluid in CVVH must contain about 3 mEq/l of calciumPatients undergoing an exchange of very large volumes of ultrafiltrate carry the risk of hypercalcemia, therefore may require a lower content of calcium in replacement fluids.Calcium is always absent from solutions when phosphate is presentDuring citrate anticoagulation, if calcium is present in the fluid it will neutralize the citrate before it can do its job of keeping the filter free of clots
16 MagnesiumMg in CRRT fluids ranges between 1 and 1.5 meq ⁄ l. This level is not well studied but has been clinically successfulA bolus of 2–4 g should be prescribed when Mg levels fall below normal range.
17 PhosphorusP plays a key role in cellular metabolism and is essential in several biological processesPhosphorus is not a standard component of replacement or dialysate fluids in CRRT. This is appropriate as CRRT is commonly employed in the setting of hyperphosphatemiaMajority of patients on CRRT will require phosphate supplementation shortly after CRRT initiation.Critically ill patients present several conditions predisposing hypophosphatemia such as sepsis, malnutrition, catecholamines, intravenous glucose infusion, hyperventilation, diuretics and rhabdomyolysis.Management of hypophosphatemia:- Ensure proper nutrition.- Add P to the solutions- Use Phosphate-containing ready solutions
18 The addition of phosphate to the CRRT fluids at concentrations of up to 7.7 mg/dL does not cause problems with precipitation or instability of the mixture.
20 GlucosePhysiologic concentrations of glucose in the dialysate and replacement fluids is advised to compensate extracorporeal lossesGlucose-free solutions might be used when an adequate nutritional regimen has been established
21 LactateThe simplest, most economical solution; no mixing required.Effectiveness is well-supported in clinical literature.Many adults are successfully treated with CVVH using Lactated Ringer's solution as it is:- convenient- cheap- eliminates risk of pharmacy errorPatients with severe liver failure, and particularly those with reduced muscle blood flow, may fail to metabolise lactate and develop a metabolic acidosis.In ICU patients suffering from multiple organ dysfunction, the conversion of lactate to bicarbonate is frequently impairedLactic acidosis causes cardiac dysfunction and hypotensionMany fluids contain a small, clinically insignificant amount of lactate to improve stability
22 Sodium bicarbonateThe sodium bicarbonate concentration in CRRT fluids can be variable. With customized solutions bicarbonate theoretically can vary from 0 to 150 meq ⁄ l.With prescribed CRRT clearances of 20 ml⁄kg⁄hour, most acid base disturbances can be managed with commercially available bicarbonate compositions of 25 meq⁄ l to 35 meq⁄ l.If there is difficulty improving pH with a commercially available solution, therapy can be changed to accommodate the patient’s needs.Options: Pharmacy customized solutions with higher bicarbSupplemental bicarbonate dripIncrease the clearance rate of the CRRT system. By increasing the clearance rate, acid removal is increased as is bicarbonate administration.The first two options have a risk of human error, whereas it is simple to increase clearances to significantly greater than 35 ml ⁄kg ⁄hour.
23 Bicarb-buffered replacement fluids can improve acid-base status and reduce cardiovascular events better than lactate fluidsThe buffer concentration should exert a buffer load that may compensate for deficits, for losses in the buffer process, and for extracorporeal losses and should therefore usually be supraphysiological.Be avare of hypercapnia!Citrate is metabolized to bicarbonate, each citrate ion producing three bicarbonate ions, no additional anionic base is required during citrate anticoagulationBicarbonate-based dialysate/replacement fluids are considered standard of care today
24 Dialysate solutions containing bicarbonate have low compatibility with calcium. If calcium is added to a bag containing bicarbonate, calcium carbonate produces , which could precipitate out of solution and clog the filter.Calcium can be added to bicarbonate-containing solutions in limited amounts; calcium concentrations of less than 2.5 mEq/L usually do not result in precipitation.The two-compartment bag with unique peel-seam interface simplifies preparation and mixing prior to use.
25 A total of 62 patientsBicarbonate-based CRRT fluids cost some 28% more than standard lactate fluidsBicarbonate fluids led to a more rapid fall in lactate and greater improvement in base excess during CRRT, but not overall control of acidosisThe choice of fluid for CRRT did not affect blood pressure or vasopressor requirements.
26 AlbuminCan be added in dialysate to remove protein bound medications in the setting of intoxication as well as substances such bilirubin
27 Fluid temperatureThe use of replacement fluids or dialysate solutions at room temperature as well as continuous blood flow through the extracorporeal system cause an average 2C reduction in body temperature, and an energy loss of about 1,000 kcal/dayThe energy loss during CVVHD is important in hemodynamic stability and prognosisHeat loss and consequent hypothermia may also affect immune functions and increase the risk of clotting of circuitLower body temperature may be desirable in patients with excessive oxygen consumption and low systemic vascular resistanceIt is not clearly known in which patients the net effect of CRRT-induced hypothermia is useful or harmful
28 Formula of an Ideal CRRT Solution PhysiologicalReliableInexpensiveEasy to prepareSimple to storeQuick to the bedsideWidely availableFully compatible
29 We dont really know the solution of this formula but what we know is…
30 A successful CRRT program can only run on safe fluids !