IV Fluids Flashcards
Body Fluid Distribution
Intracellular 40% (2/3) total body weight 28L
Extracellular 20% (1/3) total body weight 14L
Average weight 70kg
Total 42L
Extracellular
20% total body weight 14L
Plasma volume 4% 3L
Interstitial volume 16% 11L
↑ Total Body Water
Term infants 75%
Premature infants 80-90%
Children
Pregnancy
↓ Total Body Water
Elderly 50-55%
Obesity
Average TBW
70kg adult male 60% = 42L
70kg adult female 55%
Intracellular Electrolytes
Potassium K+
Magnesium Mg2+
Phosphate PO34¯
Extracellular Electrolytes
Sodium Na+
Chloride Cl¯
Bicarbonate HCO3¯
Calcium Ca2+
Osmolality
Number osmotically active particles per kg H2O
Osmolarity
Number osmotically active particle per L solution
Concentration
Tonicity
Measures particles capable to exert an osmotic force (pull)
Isotonic
Two solutions w/ = osmolarity
No osmotic pressure generated across the cell membrane
Hypotonic
Solution w/ ↓osmolarity as compared to plasma
→ cells swell
Hypertonic
Solution w/ ↑osmolarity as compared to plasma
→ cells shrink
Starling Forces
Pc - capillary hydrostatic pressure
Pt - tissue hydrostatic pressure
πc - capillary plasma oncotic pressure
πt - tissue fluid oncotic pressure
Colloid Oncotic Pressure
Osmotic pressure exerted by macromolecules (Albumin, proteins, gamma globulins)
Prevents fluids from leaving plasma & exerts pull from interstitial space
Endothelial Glycocalyx
Gel layer in capillary epithelium that creates physiologically active barrier w/in vascular space (keeps fluid intravascular)
Creates barrier b/w blood & vessel
Binds to circulating plasma albumin, preserving oncotic pressure, & ↓capillary permeability to H2O
Contains inflammatory mediators, free radial scavenging, activates anticoagulation factors
Promotes laminar flow (prevents adhesion)
RAAS Impact on Fluid Dynamics
Sodium & water reabsorption
ACEi/ARBs ↓fluid volume
ADH
Anti-diuretic hormone
Prevents diuresis
Water reabsorption
Atrial Natriuretic Peptide
ANP
Natriuresis - sodium excretion
Stimulates kidney to release Na+ & H2O
↓intravascular volume
Crystalloid Volume Expansion
3-4L to expand IV compartment 1L
3:1 replacement
Half-life 20-30min intravascular
Normal Plasma Concentrations
Na+ 142mEq/L K+ 4mEq/L Cl¯ 103mEq/L PO43¯ 1.4mEq/L Mg2+ 2mEq/L Ca2+ 5mEq/L pH 7.4 290mOsm/L
Lactated Ringer
Buffer = lactate (converted to bicarbonate)
Isotonic (275mOsm/L)
Provides 100mL free H2O per L solution
Lowers Na+
Avoid in ESRD (K+)
Avoid mixing w/ PRBC (Ca2+ binds to citrate)
- Citrate keeps blood anticoagulated
LR Electrolytes
Na+ 130mEq/L K+ 4mEq/L Cl¯ 110mEq/L Ca2+ 3mEq/L Lactate 28mEq/L 275mOsm/L