Fluids Flashcards
Extracellular fluid compartment
- Intravascular = fluid component of blood
- Interstitial = fluid surrounding cells 3rd spacing
- Transcellular = CSF, pericardium, synovial fluid
Principal Extracellular Fluid Electrolytes
Sodium
Bicarbonate
Chloride
Principal Intracellular Fluid Electrolytes
Potassium
Magnesium
Calcium
Intracellular Fluid (ICF) Calculations
2/3 of TBW
Extracellular Fluid (ECF) Calculations
1/3 of TBW*
a. Interstitial = 3/4 x total ECF
b. Intravascular = 1/4 x total ECF
Two factors that regulate total body volume
- Osmolality
2. Total Body Water
Baroreceptors sense change in what compartment of the body for fluid volume regulation?
Intravascular
T/F: Osmolality always overrides effective blood volume
False; Other way! (Think about Edema)
Osmolality Critical Values:
<260 =
>330 =
Must look at both serum [Osm] and ___________ in the patient to assess fluid balance.
total fluid volume
What can cause a low serum [Osm] but does not indicate excess water in the patient?
Loss of electrolytes, especially Na+
Hydrostatic pressure pushes fluids ___________ of cell and the interstitial space and ______________ of circulation. Oncotic pressure pushed fluid _________ of cells and the interstitial space and _________ of circulation.
Inside; Out
Ouside; Into
Hypovolemia
Loss of body fluid in the intrastitial and/or intravascular space
Two types of hypovolemia:
- Total body water loss
2. Intravascular hypovolemia - fluid not appropriately distributed
Symptoms of Dehydration
- Rapid weightloss (fluid v fat)
- Decreased skin turgor
- Oliguria (decreased output)
- Concentration urine
- Weak, RAPID pulse
- Decreased BP (<90/<60), orthostasis (Diastolic drop 10 mmHg; Systolic drops 20 mmHg)
- Prolonged capillary filling time - Finger nail bed test
- Sensation of thirst, weakness, dizziness, muscle cramps
Lab Findings for dehydration
- High [Osm] due to lots of fluid loss
- Low [Osm] due to lots of SODIUM loss
- Blood: High HCT, BUN:Cr ratio > 20:1
- Urine: High osmolality {>300 mOsm/kg)
How do you establish severity of dehydration?
Look at weight loss
Mild: 2%
Moderate: 6%
Severe: 10%
How do you implement fluid replacement in patients?
Must include: Maintenance + Deficit + Ongoing loss
- Replace 1/2 of deficit in the first 24 hours
- Replace remaining deficit in the next 48 hours
- Replace ongoing fluid loss mL/mL
What types of fluids can we use for fluid replacement and where do they go?
- D5W = Intravascular space; Behaves like water (Even distribution)
- 1/2 NS = Hypotonic solution acting as 1/2 free water and 1/2 NS in the body
- NS = Expands to ECF
- 3% sodium chloride
Need to increase blood pressure, which fluid replacement option would you use?
a. D5W
b. 1/2 NS
c. NS
d. 3% sodium chloride
Normal Saline due to increased fluid to interstitial space
Low blood volume and normal sodium content fluid replacement:
a. D5W
b. 1/2 NS
c. NS
d. 3% sodium chloride
a. D5W
Hypervolemia
Thirdspacing of fluid resulting in Edema and Ascities
Symptoms of hypervolemia
- Decreased output
- Increased HR
- Decreased BP
- Rapid Weight increase
- Pitting edema: Location, bilateral? and how high
- hematoma
Bilateral versus Unilateral edema
Bilateral = ORGAN FAILURE Unilateral = some other disease pathway
How do we manage hypervolemia?
- Treat underlying disease
- Restrict fluid replacement
- Administer diuretics/colloids
Best recipient of colloid infusion?
Patient with low albumin levels to increase colloid pressure
Patient is dehydrated, which fluid replacement should you use to expand volume?
a. D5W
b. 1/2 NS
c. 25% colloid infusion
d. 3% sodium chloride
e. 5% colloid infusion
f. NS
e. 5% colloid infusion = iso-oncotic
Patient has edema and low albumin levels, which fluid replacement option should you use?
a. D5W
b. 1/2 NS
c. 25% colloid infusion
d. 3% sodium chloride
e. 5% colloid infusion
f. NS
c. 25% colloid infusion
What defines oliguria?
< 400 mL of urine output in 24 H (for adults)
What defines orthostasis?
> 20 mmHg change in systolic BP with sitting & standing BP
10 mmHg change in diastolic BP with sitting & standing BP
Serum Osm when water loss»_space; Na loss
Hyperosmolarity > 330 mmol/L (hypovolemia)
Serum Osm when water loss «_space;Na loss
Hyposmolarity < 260 mmol/L (hypovolemia)
What lab values increase with hypovolemia?
HCT Proteins Electrolytes (sometimes!! Complex...) BUN: Creatinine > 20:1 Urine osmolality (>300 mOsm/kg, concentrated urine)
Mild dehydration (weight loss only, know that symptoms can add urgency)
2% weight loss (acute)
Moderate dehydration (know that symptoms add urgency)
6% weight loss (acute)
Severe dehydration (know that symptoms add urgency)
10% weight loss (acute)
0-10 kg patient fluid needs
100 mL/kg
10-20 kg patient fluid needs
1000 mL + 50 mL/kg over 10
> 20 kg patient fluid needs
1500 mL + 20 mL/kg over 20
Adults fluid needs “rule of thumb”
30-35 mL/kg/day
Fluid replacement strategy and time line:
Day 1: replace 1/2 of the deficit lost in first 24 hours (PLUS MAINTENANCE NEEDS, 1 kg lost = 1 L water)
Day 2/3: replace remaining deficit in the next 48 hours (plus maintenance needs)
Replace ongoing fluid loss mL/mL
Cautions in replacing fluid loss with hypovolemic patients:
Renal failure Hepatic failure Cardiac failure Elderly (Pre-disposed to fluid overload, start low and go slow)
D5W: Tonicity Dextrose content ECF% ICF% Free water/L
Hypotonic (no NaCL) Dextrose 5 g/dL 40% ECF 60% ICF 1 L free water
0.45% NaCL: Tonicity NaCl mEq/L ECF% ICF% Free water/L
Hypotonic 77 mEq/L Na; 77 mEq/L Cl 66.5% ECF 33.5% ICF 0.5 L free water
0.9% NaCl: Tonicity NaCl mEq/L ECF% ICF% Free water/L
Isotonic 154 mEq/L Na; 154 mEq/L Cl 100% ECF 0% ICF 0 L free water
3% NaCl: Tonicity NaCl mEq/L %ECF %ICF Free water/L
Hypertonic 513 mEq/L Na; 513 mEq/L Cl 100% ECF 0% ICF -2.33 L free water
Hypervolemia sign/symptoms: Urine output HR BP Weight
Decreased urine output Increased HR Decreased BP Increased weight (Edema/ascites/hematoma)
Pitting edema scale 1+
2 mm (lowest scale)
Pitting edema scale 2+
4 mm (2nd)
Pitting edema scale 3+
6 mm (3rd)
Pitting edema scale 4+
8 mm (4th)
Management of hypervolemia (3):
- Treat underlying disease
- Restrict fluids
- Diuretics (loop are most effective, thiazides, K+ sparing if underlying disease would make it rational)
- Colloids given if proteins v. Low
Therapeutic fluids (2) with hypervolemia:
Colloid solutions
Oxygen-carrying resuscitation solutions (Blood, PRBC)
Albumin 5% indication
Oncotic comparison with plasma
Hypovolemic patients (low BP) Iso-oncotic with plasma
25% albumin solution indication
Given when fluid intake needs are minimized or oncotic pressure needs are raised (edema)
Drug-induced cause from amphotericin B, aminoglycosides (kidney tubule damage), and long-term diuretic therapy
Hypomagnesemia (also caused from GI/renal loss and poor intake/absorption)
Signs/symptoms of hypomagnesemia usually not seen until
< 1 mg/dL
S/S: CNS & CV
lethargy, weakness, fatigue, confusion
V-tach, V-fib, premature ventricular contractions
Hypomagnesemia (usually not seen until < 1 mg/dL)
1 g = ___ mEq Mg
8.1 mEq
Treatment of hypomagnesemia WITH symptoms AND < 1 mg/dL Mg:
- IV magnesium sulfate: 2 g bolus
2. Continuous infusion to replenish body stores: 0.5-1 mEq/kg/24 H over 2-5 days
Treatment of hypomagnesemia WITHOUT symptoms AND < 1 mg/dL Mg:
- Continuous infusion ONLY: 0.5-1 mEq/kg/24 H over 2-5 days (to replenish body stores)
Treatment of hypomagnesemia without symptoms and Mg > 1 mg/dL:
- Magnesium oxide supplement: 400-800 mg QID (242 mg of elemental Mg)
Seen in renal failure patients taking antacids or laxatives or with excessive doses in hospitalized patients
Hypermagnesemia
Decreased tendon reflexes
Muscle weakness
Sedation
Vasodilation
S/S of hypermagnesemia
Treatment of hypermagnesemia (3):
- DC magnesium source
- Ca++ to reverse effects
- Administer diuretics to promote excretion
