Week 8 Chronic Renal Disease: Dialysis Flashcards
What are the types of dialysis?
- peritoneal dialysis: exchange in peritoneal cavity; can be done by pt at home and can be done 7 days a week
- hemodialysis: directly exchanging with blood; done in a clinic (more rpaid) over 8-12 hrs; low QoL; nausea and vomitting
Treatment for renal failure
Goal of renal failure treatment
preserve renal function if any.
* Treatment with medications/fluid management (may need diuretic therapy).
* BP management.
* Will eventually need dialysis If GFR falls below 10 mL/min/1.73m2 (with or without uremic/fluid overload symptoms).
Protein Requirements in CRF (predialysis)
Pre-dialysis: Protein restrictions (0.8-1 g/kg or less if symptoms are severe or if patient not yet starting dialysis; typically stage 1-4), maintain electrolyte/mineral stability (K+/PO4), sodium restriction essential; look at blood work to decide
* IF Stage 3-4:KDOQI guidelines talk about 0.6-0.8 g/kg/d (but controversial as older guideline).
Weight to use in pre-dialysis patients with CRF
BMI range to decide on which weight to use: 22-27 (IBW weight range)
* Must always look at best estimate of dry weight in patients with chronic kidney disease as the weight (verses actual weight if excess fluid on board). Use the best estimate of the dry weight to compare to ideal body weight
* <20 high prevalence of sarcopenia
* >27 may be fluid overload and have CV risk; pitting edema of 1+ (1kg), 2+ (2kg), 3+ (3kg)
Energy Requirements in Pre-dialysis patients with CRF
25-35 kcal/kg (pre and during dialysis)
* As per renal tip sheet use 30-35 kcal/kg if underweight or malnourished; otherwise 25-30 kcal/kg. Older patients (>65 yrs); may need this as well
Nutrition therapy for renal insufficiency
- Fluid: generally not fluid restricted unless severe fluid overload or prescribed by MD (if so, based on insensible losses + u/o)
- Energy: 25-35 kcal/kg; may need more in acute renal failure; but be careful not to give too high in renal transplant if patient’s BMI>27. (Consider age of patient)
- Need water soluble supplementation/keep fat soluble vitamin supplementation on lower side (monitor labs)
Treatment of ESRD
- Hemodialysis (HD)
- continuous ambulatory peritoneal dialysis (CAPD)
How does hemodialysis work?
Semi-permeable membrane separates the 2 compartments: Blood & Dialysate (glucose, bicarbonate/acetate, electrolytes/minerals)
* Works on principles of osmosis and diffusion (higher concentration moves to area of lower concentration)
* Unwanted substances removed (urea, creatinine, excess potassium, excess fluid)
* Also lose vitamins and amino acids
* Dont want them taking vit A supplements
* Usually done 3 times per week in a dialysis center
* Issues: fluid shifts/venous access
* Correct electrolyte imbalances quickly
* Quality of Life issues
* Can do home HD
Protein needs in HD
In stable hemodialysis 1.0-1.2 g/kg
* May need 1.2-1.5g/kg/d if an ICU patient on
continuous HD and in Acute renal failure; catabolic, stress illness; some up to 2
Energy needs in HD
Typically 25-35 kcal/kg
* Energy needs as per pre-dialysis (based on age). Consider though if patient had inter current illness-may need an SF.
* use weight that is weight after dialysis session or the best estimate of the dry weight.
Body weight to use in HD
Best estimate of dry weight; often considered to be the weight after coming off of HD
* RD’s monitor intra-dialytic weight gain (try to keep less than 1-2 kg per session; but it can be higher)
Fluid needs in HD
Fluid needs: u/o (urine output in 24 hrs) + 500-1000 mls/24 hrs typically
* includes free fluid in food
Describe CAPD
Catheter inserted through pt’s abdominal wall and Dialysate infused by gravity (2 litres at one time)
* Dwell for specified length (4-6 hours) then drained
* More substances lost
* Promotes steady state chemistries/fluid balance
* Fewer dietary restrictions
* Can be done at home
* Usually daily
* Also the option for Continuous Cyclic PD (CCPD); allows for better control of electrolyte and fluid balance
* Risk: Infection of the peritoneum (peritonitis)
What makes up dialysate?
Dialysate solutions consist of amino acids, electrolytes, dextrose
* Create a concentration gradient to facilitate transfer of excess electrolytes and fluid into dialysate solution (by osmosis)
* Need to consider: CAPD dialysate solutions contain calories via dextrose in solution
Protein needs for CAPD
Emphasis on protein: protein intake of high biological value (animal based protein) – consider phosphorus content of protein foods
* 1-1.2 g/kg/d in ambulatory/stable setting
* higher if peritonitis, > 1.2 -1.3 when patient has peritonitis (or malnourished)
* Could be up to 1.5-2.0 g/kg/d in ICU
Energy needs for CAPD
25-35 kcal/kg
* may need more in acute renal failure; but need to adjust for energy delivery from dialysate solution
* CAPD patients need less energy due to absorption of calories from dialysate (60-75%) (absorbed dextrose so x3.4 kcal/g then 60-75% = calories dextrose is giving)
Fluid needs in CAPD
Fluid based on u/o (often little or no u/o) therefore fluids restricted to 500-1000 mL/day + u/o
* if no TFI listed then there isnt one needed and we use their fluid amount for their age
weight t
Weight to use in CAPD
Need to use dry weight to calculate nutrient requirements.
* There are fluid shifts during dialysis (from ECF to ICF)
Vitamin/mineral restriction during dialysis
- Vitamin D supplementation and dietary PO4 restriction typically required to prevent renal osteodystrophy
- Na restriction essential
- Hyperkalemia common in HD patients – will often require K+ restricted diet; CAPD patients less prone to hyperkalemia and often require liberalized K+ diet +/- additional high K+ foods
How much of dialysate solution is exchanged and what is the typical concentration of dextrose in the solution?
- exchange bags of dialysis solution are 2L each, usually 4 exchanges per day; this is 8 Litre of fluid per day
- Solutions come in: 1.5, 2.5 and 4.25% dextrose concentrations (higher dextrose concentrations/hypertonic remove more fluid)
Calculation: CAPD dialysate calories using 75% Absorption for 2L exchange of 2.5% dextrose
- 2000 mL x 0.025 g/mL dextrose concentration = 50 g dextrose x 3.4 kcal/g dextrose = 170kcal
- 170 x absorption factor (assumed to be about 60-75%) = 170 kcal x 0.75 = 128 kcal from one exchange (511.5 kcal/d for 4 exchanges)
- A patient on 4 exchanges of 1.5% gets 306 kcal per day
- A patient on 4 exchanges of 4.25% gets 867 kcal per day
What can increased PTH levels lead to?
- Parathyroid hyperplasia (enlargement of parathyroid gland(s))
- Secondary hyperparathyroidism
- Renal osteodystrophy
renal diets
Cosider phosphorous and potassium content (#1 priority is hyper/hypokalemia, #2 priority is hyper/hypophosphatemia
* Strong emphasis on potassium and phosphorus regulation; need to look at foods high in those foods; as well as protein content (plant-based proteins important)
* Mediterranean Meal and DASH Meal Patterns; yet many traditional renal diets require restriction of healthy foods like F/V
Food Sources of Potassium
- Low potassium diets restrict F/V; challenges with what is the healthiest
- Diet for patients with renal disorders.
- Little is known about the amount of potassium in processed foods.
- Lower sodium products may contain potassium additives that increase potassium content
Food sources of phosphorous
Phosphorus content in food additives also largely unknown; although being explored
