Continuous Renal Replacement Therapy Inservice
Jennifer A. Wooley, MS, RD, CNSD
November 14, 2001
WHAT: Continuous Renal Replacement Therapy (CRRT) – always involves dextrose. Net
absorption/assimilation of dextrose from dialysate is 270 grams per day, which contributes 918
calories/day.
1L [2.5%] dextrose (25 g /L) dialysate / hr x 24 hr / day = 600 gm dextrose x 45% uptake
= 270 gm dextroxe x 3.4 kilocalories /gram = net absorption of 918 dextrose calories/day
Slow Continuous Ultrafiltration (SCUF) – does not involve dextrose
WHY: Primarily used for the removal of fluid and azotemic waste products in critically ill patients that
are hemodynamically unstable.
WHO: Acute Renal Failure
Multi-system organ failure
Fluid overload
Hypotensive/hemodynamically unstable patients
HOW: CRRT uses a dextrose-based osmotic gradient to pull fluid and azotemic waste products from the
blood at a continuous rate over 24 hours per day. Net fluid loss per hour is programmed into the
process.
NUTRITION ASSESSMENT:
Calories:
25 – 30 calories/kg reference weight
- Hypothermia induced by CRRT may decrease REE by as much as 7%.
- Indirect calorimetry during CRRT may not be a reliable indicator of energy
expenditure.
Protein:
CRRT is a catabolic process. Patients may require 1.5 – 2.0 gm/kg protein per
day. Re-evaluation of protein requirements may become necessary based on
acute visceral protein trends.
-
Protein delivery does not need to be restricted in this catabolic population.
-
1.5 – 2.0 gm nitrogen/day lost across the CRRT membrane in patients with
dialysis flow rates of 1 and 2 L/hr, respectively.
Fat:
goal: < 1 gm/kg reference weight
Fluid:
LIBERAL
Micronutrients: depends on the nutrition mode
DESIGNING THE NUTRITIONAL REGIMEN:
1.
2.
3.
4.
5.
6.
Complete a thorough review of the medical record.
Review all medications.
Review all laboratory data.
Assess the patient’s nutritional status.
Determine the patient’s predicted caloric and protein requirements.
Evaluate the most appropriate route for nutrient delivery.
PARENTERAL NUTRITION:
1.
Determine whether the patient has central access and a clean port for parenteral nutrition.
2.
Determine the contribution of obligatory dextrose and lipid calories from all I.V.’s, medications and
CRRT.
3.
The base solution:
-
There is no need for phosphate-free amino acids or protein restriction in this
population for the following reasons:
-
Uninterrupted CRRT leads to a dramatic daily decline in serum
phosphorus levels secondary to intracellular shifting and increased
losses with ultrafiltration.
-
The fluid concentration with phosphate free amino acids is maximally
limited in its 15% final concentration. Fluid restrictions are not
necessary with CRRT as total volume delivery and ultrafiltration fluid
losses are manipulated to result in an hourly net loss of fluid. In other
words, fluid delivery is built into the goal for hourly “net” fluid losses,
therefore fluid restrictions aren’t necessary.
-
Phosphate free amino acids are very expensive.
-
A minimum of 50 grams of dextrose must be included in each bag of
parenteral nutrition to protect the solution from precipitation.
-
Parenteral delivery of lipid must be modulated around propoful therapy
when indicated and should not exceed 20-30% of total calories/day.
4.
The Nephrology Service generally, manages serum ionized calcium levels and treats acid –base
abnormalities via the dialysis bath. Therefore, daily manipulation of these substrates via the nutrition
regimen is not necessary.
5.
Anticipate an increased need for phosphorus, magnesium and potassium as TPN additives during
CRRT therapy. Err on the moderate side with these additives as they can always be supplemented
outside the TPN.
6.
Standard MVI and trace element packages are appropriate.
7.
Daily provision of additional water soluble vitamins (Nephrovite®) crushed and administered via the
nasogastric tube may be beneficial to replace losses during ultrafilitration.
8.
Physicians and pharmacists routinely use renal dose Pepcid (20 mg/day) unless the patient is
coagulopathic in which carafate per tube would be used for GI stress prophylaxis.
9.
Use an insulin drip (dose: 100 units / 100ml volume) as the sole agent for glucose control during
CRRT. Insulin must not be incorporated into the parenteral solution as an additive as the risk of
hypoglycemia is great should CRRT be interrupted for any reason.
ENTERAL NUTRITION:
1.
This critically ill population must have small bowel access.
2.
Determine the contribution of obligatory dextrose and lipid calories from all I.V.’s, medications and
CRRT.
3.
In general, use of Standard or Fat Malabsorption formulas are appropriate.
- Fat Malabsorption formula is appropriate for use when patients are on propofol therapy because
it is low in fat (39 gm/liter 70% MCToil).
4.
Renal formula (Nepro) is not indicated for the following reasons:
- This formula is high in calories at 2.0 cals/ml. In particular, the lipid content is very high, at 95.6
gm/liter, and may contribute to overfeeding especially when patients are on propofol therapy.
- The electrolyte and fluid restrictions in this formula are not necessary with this form of dialysis.
5.
It may be necessary to dilute enteral formulas in order to avoid overfeeding CRRT patients.
6.
When adding modular protein powder to diluted enteral formula, limit MPRO to 10 gm/240 ml in
order to protect the solubility of the solution as well as prevent clogging of the feeding tube.
7.
A multi-vitamin may be needed to meet 100% RDI’s with diluted enteral formulas.
8.
Daily provision of additional water soluble vitamin (Nephrovite®) delivery may be beneficial during
CRRT to replace losses during ultrafiltration.
9.
An insulin drip is the preferred method for achieving glucose control in this population. Recommend
using 100 units insulin / 100ml volume.
10. Anticipate that serum phosphorus, magnesium and potassium levels will fall dramatically with CRRT
resulting in the need to monitor levels closely and supplement via I.V. route accordingly.
11. The Nephrology Service generally, manages serum ionized calcium levels and treats acid –base
abnormalities via the dialysis bath. Therefore, daily manipulation of these substrates via the nutrition
regimen is not necessary.