Lecture 5: Nutrition, Fluids, and Electrolyte Therapy Flashcards
What should we not base our nutrition assessment solely on?
Weight
What goes into a nutrition assessment?
- BMI
- Unintentional weight change
- Changes in PO intake
- Severity of illness
- IBW
What is the criteria to diagnose malnutrition?
ASPEN Criteria
- Insufficient caloric intake (energy intake)
- Wt loss
- Loss of muscle mass
- Loss of subcutaneous fat (Body Fat)
- Localized or generalized fluid accumulation masking wt loss (Fluid accumulation)
- Diminished functional status (Grip strength)
At least 2
What can long-term overfeeding result in?
- Hepatic steatosis
- Ureagenesis
- Immunosuppression (esp w/ liquids)
What equations are used to determine nutrition requirements?
- Harris Benedict
- Mifflin-St Jeor
Quick rule of thumb for estimating caloric needs and protein needs based on IBW
- Cal: 25-30/kg/d
- Protein: 1.2g/kg/d
Burn pts may require more protein, up to 2g/kg
What is the preferred method of feeding?
PO
When do we start enteral or parenteral feeding?
7-10d of no oral intake and if its going to be in for at least 5 days.
How does enteral nutrition work?
Direct entry into GI system at stomach or small intestine
CIs to enteral nutrition
- GI hemorrhage
- Peritonitis
- Severe ileus
- Bowel obstruction distal to access site
- Intestinal ischemia
- Malabsorptive disorders with high volume diarrhea
How do we start enteral nutrition?
- Low rate, tapering up after 24-48h
- Monitoring for N/V/D/C/abd pain
How are macronutrients presented in parenteral nutrition?
- Carbs: Dextrose (50%-60%)
- Protein: Crystalline amino acids (15%-25%)
- Lipids: Polyunsaturated long-chain triglycerides like soybean oil (20%-25%)
parenteral has the highest risk.
alphabetically in order of highest to lowest proportion CLP
What is refeeding syndrome?
Electrolyte abnormalities that occur during reinstitution of carbs to a starved patient
Phosphate, Mg, and K depletion may occur
What is the typical breakdown of macronutrients in parenteral nutrition?
- Carbs: 50-60%
- Proteins: 15-25%
- Lipids: 20-25%
What kind of access does parenteral nutrition require?
Central venous access due to its hyperosmolar nature.
How often do we recheck labs in pts on TPN?
- Glucose: every few hrs
- BMP: Q8-12h
What is the general breakdown of fluid in the body?
- ICF: 2/3
- ECF: 1/3
Within ECF: 75% is interstitial, 25% is intravascular.
How do you approximate TBW (total body water)?
60% of body weight in males
50% for a female
Example distribution of TBW
Normal minimal obligatory water intake
1600 mL/d
Where is most fluid loss through?
Urine
What requires increased water intake? (7 conditions)
- Fever
- Sweating
- Burns
- Tachypnea
- Surgical drains
- Polyuria
- Ongoing GI losses
- 100-150 mL/d for every degree of body temp above 37C
4 main ways we lose water from our body
- Urine: 500 mL
- Skin: 500 mL
- Respiratory tract: 400 mL
- Stool: 200 mL
How do we estimate water requirements?
- 35 mL/kg/d = 35x70 = 2450 mL/d
Na requirements daily
- 1-3 meqs/kg/d
- 0.45% saline contains 77 meq NaCl/L
K requirements daily
- 1 meq/kg/d (50-100 daily)
- Osmotically as active as sodium, so adding 40 mEq to 0.45% saline creates 3/4 isotonic saline.
- Commonly added as 20meq/L
Oral is most preferred
Why do we only infuse potassium at 10 meq/hr?
Rapid administration causes a burning sensation
How do we estimate hypokalemia?
1 mmol/L below normal => total deficit of 200-400 mmol
How do we calcuate the potassium deficit and correct it?
- Deficit in mmol = (normal K lower limit - measured K) x BW in kg x 0.4
- 10 mEq of KCl raises serum by abt 0.13 mEq for normal kidneys.
1 mmol = 1 mEq
Average dosing to tx hypokalemia
40 to 100 mmol/d
What are the 3 primary mechanisms we utilize to treat hyperkalemia?
- Membrane stabilizer: calcium gluconate
- Redestribution: insulin + B2 agonist (albuterol)
- Removal: Kayexalate or hemodialysis
Why do we want to make sure glucose is normal and how?
- If glucose is low, protein and body fat will get consumed. (Protein-sparing effect)
- We need about 100-200g/d
What are colloid solutions? (2)
- Large molecules that DO NOT PASS through membranes
- When infused, they remain in the intravascular compartment and expand intravascular volume by drawing fluid from extravascular spaces.
Albumin is the most common?
What are crystalloids? (3)
- Small molecules that flow between cell membranes
- Increase fluid volume in both intra and extravascular spaces.
- Subdivided into isotonic/hypotonic/hypertonic
What is the danger with infusing sodium too fast?
Central pontine myelinolysis can occur
What are the isotonic crystalloids? (4)
- NS (0.9%)
- LR’s
- D5W (5% dextrose in water)
- Ringer’s acetate solution
What is in NS? (2)
- 154 meq of Na
- 154 meq of Cl
What is in LR/hartmann solution? (5)
- 130 meq of Na+
- 4 meq of K+
- 3 meq of Ca+
- 109 meq of Cl-
- 28 meq of HCO3-
Most physiologically adaptable due to similarity to body composition.
When is LR typically used? (5)
- Burn injuries
- GI tract losses
- Fistula drainage
- Fluid losses due to burn/trauma
- Acute blood loss or hypovolemia d/t 3rd spacing
What is the concern with using LR? (3)
- LR cannot be used in someone with liver dz, or it will make bicarb
- Caution in severe renal impairment d/t K
- Do not give in someone with pH > 7.5
What happens when D5W is metabolized?
Hypotonia, causing fluid shift inward to cells.
How many calories is D5W?
170 cal
What are the primary options in treating hypovolemia via fluids? (2)
Volume expansion: NS or LR
We want intravascular volume expansion
How do we treat dehydration/hyperosmolarity? (Not hypovolemia)
Free water replacement, aka D5W or 0.45% saline
In post-op pts, how do we manage fluids?
NS is preferred because narcotics can stimulate SIADH.
Why does NS cause volume expansion? (3)
- Free water gets distributed
- Na stays outside of cells
- NS essentially has no free water.
What is the 4 2 1 rule of peds for maintenance fluids?
- First 10kg = 4 cc/kg/hr
- Second 10kg = 2 cc/kg/hr
- 1cc/kg/hr after
Maintenance fluids
What is the IVF rate for an adult?
wt (kg) + 40 per hour.
