Fluids Flashcards
Describe the distribution of the total body water in dogs/cats
TBW- 66% in the cell 34% is extracellularly
25% (70% of ECF) is interstitial; and 9% (30% oftheECF) is in the vessel
What are the approximate values of the major electrolytes in the extracellular and intracellular fluid compartments
Extracellular: Na 145; Cl 110 Intracellular: K 140 mEq/L and Mg 35 mEq/L
What is electroneutratility
is the concept that intracellular and extracullular will add up to zero (mEq/L)
Gibbs Donan effect
the behavior of charged particles near a semi-permeable membrane that sometimes fail to distribute evenly across the two sides of the membrane
Convert mEq to milimoles
mEq = milimoles x valance
Discuss effective vs. ineffective osmoles and toncitiy
Tonicity- ability to hold water; osmolarity; Isotonic replacement (solution that does cause achange in the size of red cell); Effect osmolarity
Osmolalrity: The concentration of a solution expressed as the total number of solute particles per kilogram
What is the total osmolality
2 (Na+K) + BUN/2.8 + Glu/18
Effective osmolality caluclation
2 (Na+K) + Glu/18
Whate is the osmolal gap
Difference is between the measured and calculated. Normal -2 to 5
Define Colloid
Osmotically active > 32 kdaltons
Whate is normal plasma COP for dogs and cats
~20
Describe net filtration of fluid in the capillary including a being able to discuss and apply Starling’s law
Out is 0.3-.5 filtration in the arteries; In is 0.3-0.5 favors reabsorption in venules
What is the effect of the endothelial glycocalyx on fluid flux in the capillary and how does this differ from fluid movement originally described by the starling equation
The endothelial glycocalyx is the primary barrier to microvascular filtration
Colloid osmotic pressure of the fluid on the interstitial side of the glycocalyx and within the endothelial clefts has a more direct effect on filtration than that of the free interstitial fluid.
Reversal of fluid flow across the microvascular barrier upsets this colloid osmotic pressure gradient and limits fluid reabsorption by the microvasculature
Describe the net effect on the effective circulating volume if loss is a hypotonic fluid
will result in increases in ECF osmolality, reflected by increased in serum sodium concentration. As a consequence, water will move from the ICF compartment to the ECF compartment until osmolality is equalized. The loss of ICF volume has the greatest impact on the central nervous system, and if the degree of soule-free water loss is severe and acute it can result in neurologic abnormalities and possibly death ias a result of neuronal cell shrinkage. The effective circulating volume is preserved- overall though less total body water
Describe the net effect on the effective circulating volume if loss is a isotonic fluid
The ECF will cause changes in the ECF volume with little change in ECF osmolality, and hence there will be no change in the ICF volume. Will lead to interstitial dehydration. Isotonic fluid gain would cause interstitial overhydration
Describe the net effect on the effective circulating volume if loss is a hypertonic fluid
: a drop in ECF osmolality results and provides a gradient for water to move into the ICF compartment leading to cell swelling- net decrease
Describe the effects of administration of hypotonic on the effective circulating Volume.
lower of osmolarity and sodium concentration. 5% dextrose in free water is a unique isosmotic solution with hypotonic effects because dextrose is rapidly metabolized and free water remains. Replenish free water deficits and useful for treating animals with hypernatremia . hypotonic fluids distribute throughout both intracellular and extracellular fluid compartments, with less remaining extracellularly in comparison to isotonic fluids. Should not be bolused. Depends on the fluid type that you give
Describe the effects of administration of isotonic on the effective circulating Volume.
useful for hypovolemic shock; does not cause significant fluid shifts between intracellular and extracellular fluid compartments in normal animals. Used for dehydration with losses that are hypotoic/isotonic
Describe the effects of administration of hypertonic on the effect on circulating volume
high osmolarity and sodium concentration such as 7.5% saline. Causes a free water shift from the intracellular space to the extracellular space; expands the extracellular fluid volume by 3-5 times volume administered. Hypertonic saline is used for the therapy of hypovolemic shock, intracranial hypertension and severe hyponatremia. The intravascular volume expansion effect to hypertonic saline is transient (<30 mins) because of the redistribution of electrolytes throughout the extravascular space.
Define urine osmolality
is the number of molecules (unaffected by the size of the molecules) per kilogram of water and must be measured by an osmometer. Used to assess the concentrating ability of the kidney and should be interpreted along with the hydration and volume status of the patient
Define urine specific gravity
assess renal concentrating ability because it is easier to measure. Is a ratio of the density of a susbatance compared to water, so it is affected by the number of molecules and their molecular weights.
How are urine osmolality and urine specific gravity related? And when does this relationship fail?
Normally USG and urine osmol are linearly correlated. If many high molecular weight molecules are present in the urine, USG will overestimate the urine solute concentration whereas the urine osmolality remains accurate. Interfere with USG include albumin, synthetic colloids and iohexal, lipoproteins. Synthetic colloids- at 6 hrs at difference, differengce at 18 hrs- not in reading reading list; first pee okay, not the second
What is urine osmolality was useful for?
differentiating sodium disorders, identifying the syndrome of inappropriate antidiureic hormone, differentiating perrenal from renal causes of azotemia and diagnosing diabetes insipidus
Whate are the 3 general phases of fluid therapy
Resuscitation, rehydration, and maintence
What is the law of physics that governs the flow of fluids through a tube
Poiseuille’s Law: that the flow of fluid is related to a number of factors: the viscosity of the fluid, the pressure gradient across the tubing the length and diameter of the tubing. Doubling the diameter of a catheter increases the flow rate by 16 (r4). The larger the IV catheter the greater the flow; Also want the shortest length of tubing to maximize flow
Discuss the methods (physical exam, or labs) of monitoring IV fluid therapy
Body weight gain. Assessment of hydration: plasma osmolality, urine osmolality, urine specific gravity, PCV, total protein, serum sodium concentration
What physical exam findings are associated with overhydration/volume overload
Serous nasal discharge, chemosis, juguar venous distension, interstitial pitting edema; increased respiratory rate/ crackles wheezes.
What are some of the complications of IV fluid therapy
Organ edema with volume overload; electrolyte imbalances, changes to the gastrointestinal tract resulting in decreased motility, increased interstitial permeability. Increased risk of ventricular arrhythmias, disruption of cardiac contractility, decreased cardiac output. Starling’s myocardial performance curve
What buffers are used in the currently available IV fluid preparations/ metabolized?
LRS- Lactate- liver; Norm-R - acetate- Gluconate; Plyte- acetate/lactate
What is the most common complication of rapid administration of hypertonic saline
hypernatremia; risk for hypernatremia induced central pontine myelolysis when administered to patients with pre existing chronic hyponatremia; Used cautiously in patients with cardiac or pulmonary abnormalities because of the increase in intravascular volume and hydrostatic pressure may lead to volume overload and pulmonary edema. Also may cause significant interstitial volume depletion, particularly in patients that are already dehydrated
Whate complications have been associated with the use of synthetic colloid fluids
Acute kidney injry, coagulopathy, pulmonary edema
Discuss the pros and cons of the use of human serum albumin in canine and feline patients
Immune mediated reactions have been noted for up to 4 weeks afterwards, therefore needs to be monitored even after improved. Studies in healthy dogs show anaphylactoid reactions after a single infusion and after a second infusion; however in critically ill dogs, results in survivors showed improved albumin and total protein. Acute hypersensitivity type 1 reactions were not reported in critically ill dogs
What are the mechanisms of coagulopathy associated with use of synthetic colloids?
Either through hemodilution – non specific vs. specific actions of macromolecules on platelet function, coagulation proteins and fibrinolytic system. High molecular weight starches can cause decrease in the activity of von Willebrand’s factor and its associated factor VIII and risotcetin cofactor activities. And platelet dysfunction
Whate is pressure diuresis
urine output can double when intravascular volume and pressure increase even a few millimeters of mercury above normal. Concomitant sodium loss occurs- if diuresis goes undetected then all electrolytes may be excreted in urine because of decreased reabsorption in the proximal and distal renal tubules.
Whate dictates the rate and total volume of fluid shift after administration of IV fluids?
Starling forces, types of fluid, disease process- ex. Sepsis
Over approximately how long do rehydration fluids need to be administered
4-24 hrs
