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 are CAPD patients prone to with the extra dextrose in the dialysate solution?
CAPD patients on hypertonic solutions are prone to high triglyceride levels due to excess kcal from dextrose
What does urea or BUN represent?
- Recent protein intake
- Hydrational status
- Declining renal function
What might cause decreased levels of urea/BUN?
- Liver failure
- Malnutrition
- Overhydration from prolonged IV
- Pregnancy (due to expansion of plasma volume)
- SIADH: Syndrome of inappropriate antidiuretic secretion; occurs with brain injuries; ADH is secreted by posterior pituitary but sometimes brain injury results in increased secretion of ADH and get increase in BP and increase in fluid retention
- In dialysis patients, low BUN can signal inadequate protein intake or residual kidney function that is contributing to some urea clearance
What might cause increased levels of urea/BUN?
- Dehyration
- Renal failure (decreased urea excretion)
- CHF
- Hemorrhage/bleeding in GI tract
- Stress
- Acute MI
- Excessive protein intake/protein catabolism
Urea levels in renal insufficiency
Higher levels of urea (within the normal ranges) are typically a goal in renal insufficiency –indication of adequate protein intake.
* However, if values are above normal this is not okay ie it maybe indicative that patient is not receiving dialysis.
Urea values on dialysis
On dialysis patients will have abnormal values, but the goal is for these values to be stable. Aiming for normal serum urea for patients on dialysis is not realistic.
Low creatinine
- Small stature with decreased muscle mass
- Inadequate dietary intake
- In dialysis patients: high dialysis efficiency &/or frequent dialysis
High creatinine
- impaired renal function (with ↑ in urea)
- nephritis
- urinary tract obstruction
- CHF
- shock
- myasthenia gravis
- In dialysis patients: low dialysis efficiency &/or infrequent dialysis
renal bone disease
Renal bone disease is also known as renal osteodystrophy - Complex bone disease process that results from the mineral and hormonal abnormalities seen in CKD
how do mineral and hormonal abnormalities in CKD result in renal bone disease?
The kidney is the final regulator for calcium and phosphorus and it is also the primary site for production for calcitriol (1,25 (OH)2 D) – the active form of vitamin D. As kidney disease progresses:
* High phosphorus in the blood
* Low calcitriol levels leading to low serum calcium levels
* High parathyroid hormone (PTH) levels
What are the two different types of bone disease?
- High bone turnover (osteitis fibrosa cystica)
- Low bone turnover (adynamic bone disease and osteomalacia)
Major long-term complications of renal bone disease
- bone pain
- deformities
- fractures
- vascular and soft tissue calcification
Calcium in renal disease
98-100% of all calcium is excreted by the kidney (proximal tubules reabsorb 2/3 of that) - As renal disease progresses:
* ↓ Ca absorption in the gut (due to ↓
calcitriol production)
Kidneys lose their ability to protect against calcium overload
Phosphate in renal disease
70% of dietary phosphorus is excreted by the kidneys
As renal function declines:
* ↓ in renal tubular reabsorption to maintain serum phosphorus (mediated by in part by PTH)
Once GFR falls below ~20-25 mL/min:
* Serum PTH cannot further ↑ phosphorus excretion
* Hyperphosphatemia develops
Primary function of PTH
maintain serum calcium by:
* Increasing bone mineral dissolution (↑ Ca/PO4 release from bone)
* Enhancing gut absorption of Ca/PO4 indirectly through effect on synthesis of 1,25 (OH)2 vitamin D
What stimulates PTH
- Hypocalcemia
- Hyperphosphatemia
- 1,25(OH)2 vitamin D deficiency
What can increased PTH levels lead to?
- Parathyroid hyperplasia (enlargement of parathyroid gland(s))
- Secondary hyperparathyroidism
- Renal osteodystrophy
Sodium in renal disease
Sodium retention is seen in both acute and chronic renal failure, Leads to:
* Hypertension
* Pulmonary edema
* Heart failure
* Peripheral edema
Often on a no added salt diet
What is serum sodium indicator of?
indicator of hydration status
* Serum sodium is not a reflection of dietary sodium intake
Causes of potassium retention in renal disease
Potassium retention is seen in both acute and chronic renal failure
* Excessive intake (from diet, dialysate &/or medication)
* Tissue damage
* Fever/infection
* Hyperglycemia
* Acidosis (potassium moves out of the cell as pH decreases)
* Medications (e.g. ACE inhibitors, ARBs, amiloride, spironolactone)
* Inadequate dialysis
potassium restrictions in diet for renal disease
If serum levels increased then restrict to 1 mmol/kg in the diet (use best est of dry weight); otherwise use DRI for potassium in diet
Potential causes of hypokalemia in kidney disease
- Decreased dietary intake &/or low potassium dialysis bath
- Vomiting
- Diarrhea
- Alkalosis
- Medications (potassium binders like Kayexalate, potassium-losing diuretics)
monitoring phosphorous in renal disease
hyerphosphatemia common in later stages…. May need to be put on medications that decrease phosphorus absorption in the GI tract (eg. calcium carbonate to bind PO4)
* RDA of phosphorus approx. 700 mg/d; most renal RD would recommend 800- 1000 mg/d when phosphorus levels are high.
treating hyperkalemia
need to restrict K+ in diet + may
need to treat with K+ binder
monitoring vitamins in renal disease
- Monitor fat soluble vitamins: get increased retention of fat soluble vitamins (vitamin A/E) leading to toxicity
- Have increased need for water soluble vitamins as these tend to be excreted or dialyzed out of blood
- Most ESRD patients are prescribed a renal multivitamin instead of a general multivitamin (to avoid excessive intake of fat soluble vitamins)
vitamin D, sodium and iron supplementation in renal failure
- Vitamin D supplementation (1000-2000 IU vitD3/d) and dietary PO4 restriction typically required to prevent renal osteodystrophy
- Na restriction essential, especially if hypertensive (remember this will only help a small percentage of people); often put on 2 gram sodium restricted diet
- Iron may need to start on erythropoietin therapy +/- oral iron supplementation (low hemoglobin not uncommon)
macros diet with renal insufficiency
Diets are often higher in fat/lower in CHO; consider nutrient quality of a lower K+/lower phosphorus diet
* Often have to restrict dairy, some classes of fruits and vegetables
* Consider other medical co-morbidities (diabetes, hypertension, dyslipidemia)
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
Protein in the Diet of patients with CKD
Follow the levels recommended based on CKD (0.8-1 g/kg) or HD or PD (1-1.2 for HD; 1-1.2 or up to 1.3 g/kg/d on PD)
* Need to ensure at least 50% HBV; so if patient needs 70 g protein; then at least 35 g protein should be HBV.
Enteral nutrition for renal disease
EN must be done very carefully with peritoneal dialysis; only contraindication is the presence of an abdominal sepsis in peritoneum
* If EN feeding: what kind of formula would you use in renal insufficiency?
* Dialysis: higher protein formula - Note: caloric density, osmolarity-High
* How do you think this affects tolerance to feeds…..What about when you have uremia…
Parental nutrition for renal disease
PN can be given…. Need to monitor intra-dialytic changes in weight between dialysis to determine dry weight.
* Often kcal and nutrient delivery is limited by volume.
