Intraoperative Fluid Mgmt Flashcards
% Total Body Water
80% Newborn, Adults 60-70%, obese=lower%, lean=higher%
Fluid Compartments and %
2 main compartments: intracellular and extracellular. ICF 2/3, ECF 1/3, ECF 1/3 plamsa fluid, 2/3 interstitial fluid
Std 70kg patient water composition
70gk - 60% water = 42 total liters, 28L ICF, 14L ECF –> 4.5L plasma, 9L interstitial
Mean of regulation of fluid compartments / separation of compartments
Diffusion, Filtration, Osmosis / ICF to ECF by cell membrane, IVF to ISF by capillary membrane
Diffusion / Filtration / Osmosis
Movement of molecules among each other / transfer of water/dissolved substance from high to low pressure / water shifting thru semipermeable membrane to reach equilibrium
What is diffusion?
Movement of molecules among each other in liquids.
What is filtration?
Transfer of water from region of high pressure to low pressure
What is osmosis?
Water shifting through semi permeable membrane from area of low solute to high solute concentration unto equilibrium reached. Generated osmotic pressure. Relates to tonicity.
ECF and ICF osmolalities
Equilibrate within minutes. # of osmo active substances remains constant or moves across membrane and being water with is to maintain equilibrium.
Osmotically active substances
ECF –> sodium, chloride, bicarb.
ICF –> potassium, phosphates, mag, proteins.
Intracellular fluid lytes
Cations are potassium and mag. Anions are proteins and phosphates.
Sodium potassium pump
Counter acts sodium desire to move inside cell. Energy requiring exchange of three sodium for two potassium. Uses ATP-ase. Also
Maintain intra cell potassium for RMP and nerve conduction.
Net Capillary and lymphatics
Capillary filtration depends on cap permeability and imbalance of hydrostatic and colloidal pressures. Cap filtration is 2ml/min. Cap filtrate them enters lymphatic circulation.
Lymphatic characteristics
Receives cap filtrate via highly perm lymph caps, carries in unidirectional manner d/t valves thru right lymph or thoracic duct to venous sys via contraction of vessels or muscles.
What are starling forces?
Forces/pressures that determine mvmt of fluid across cap membrane. Capillary hydrostatic and plasma colloid osmo pressure. ISF hydrostatic and colloid osmo pressure.
Electrolyte composition.
ICF = lots of potassium, mag, phosph/sulf and protein ECF/plasma = high sodium, bicarb chloride, calcium, organic acids, some protein but less than ICF. Plasma>ISF
Summary of fluid movement between compartments.
ICF to ECF is based on osmotic gradient reg by sodium and potassium conc. IVF to ISF is based on plasma proteins, filtration pressure and cap permeability.
What is tonicity?
Deals with how a solution affects a cells volume. Water flows OUT of cell in hypertonic area, INTO cell in hypotonic area. Body adjusts better to chronic tonicity changes more than acute. IVF + salt = cell shrinks. IVF - salt = cell swells.
Types of hypervolemia
Isotonic hypervolemia has no ICF shifts, excess isotonic admin. Hypotonic hypervolemia is result of excess hypotonic admin lacking of normal lytes.
Hypotonic hypervolemia characteristics.
Leads to sig hyponatremia and low osmo (tonicity decr). Leads to CHF and cerebral edema. Examples: turp fluid flush being absorbed, anesthetic agents incr ADH secretion.
Types of Hypovolemia.
Isotonic hypovolemia has no ICF shifts. Decr in volume, no composition change. Hypertonic had loss of mostly free water from IVF. Hypotonic had loss of composition with more lytes lost.
Isotonic volume contraction (hypovolemia)
Fluids and lytes lost together. There is no intra cell fluid shifts. Most common fluid issue. Causes: diuretics vomiting excess urine loss hemorrhage 3rd spacing.
Hypertonic dehydration (contraction)
Loss of water leading to contraction of IVF, then become hypertonic. Leads to hypernatremia and pulls water from ICF. Causes include evaporative and insensible losses, inadequate free water.
Causes of fluid loss
GI loss, fever, burns, evaporation, peritonitis, diuretics, inhale dry gas. Majors: blood loss, fluid shifts (both isotonic losses). 3rd spacing is redistr of IVF to ISF, replace with balanced salts.