F L U I D S Flashcards
Two conditions that increase insensible loss
Fever, hyperventilation.
2 sources of aldosterone stimulation/release
Low volume receptors in the right atrium OR high serum potassium (indirectly, because it stimulates ACTH to release aldosterone). High serum potassium would cause aldosterone to be released because aldosterone reabsorbs Na+ in exchange for the secretion of K+ at the distal tubule.
Tx of dehydration
Give a fairly large aliquot of fluid as volume expander. 20 mL/kg of NS or LR is given over first hour. During remaining 8 hours, expected maintenance fluid is given + about 1/2 of remaining calculated loss. Over remaining 16 hours, other 1/2 of remaining calculated loss is given along with assumed maintenance fluid.
What is an important complication to remember when using NS to replace fluids?
Large amounts of NS can cause hyperchloremic metabolic acidosis
What is an important complication to remember when using LR to replace fluids?
If patient is hypovolemic and in metabolic alkalosis (i.e., from MG tube, vomiting) – you might worsen alkalosis when lactate is metabolized.
What kind of fluid replacement should you use in patients who have ascites, CHF, post-cardiac bypass patients, etc.?
These patients have excess Na and water but are hypovolemic so you should use COLLOID.
Causes of isotonic volume excess
Iatrogenic – intravasc overload of IV fluids with electrolytes.
Increased ECF without equilibration with ICF – especially post or trauma when hormonal responses to stress are to decrease Na and water excretion by kidney.
Often secondary to renal insufficiency, cirrhosis, or CHF.
Define third spacing and what kind of volume excess it is seen in.
Third spacing is shift of ECF from plasma compartment to elsewhere, such as interstitial or transcellular spaces. Causes HYPOTONIC volume excess.
Most common cause of hypotonic volume excess
Inappropriate NaCl-poor solution as a replacement for GI losses
Tx of isotonic hypervolemia
Restriction of Na and fluids
Tx of hypertonic hypervolemia
Free water replacement corrects hypertonicity which should lead to diuresis of excess fluid
Tx of hypotonic hypervolemia
Saline – will correct hypotonicity which should then correct hypervolemia
Each degree celsius above 37 adds how much insensible water loss?
2.0-2.5 mL/kg/day
Fluids/hr for pets up to 10 kg
100 mL/kg/day = 4 mL/kg/hr
Fluids/hr for pts up to 11-20 kg
1000 mL + 50 mL/kg/day for each kg above 10 kg = 40 mL/hr + 2 mL/kg/hr for each kg above 10
Fluids/hr for pts > 20 kg
1,500 mL + 20 mL/kg/day for each kg above 20 kg = 60 mL/hr + 1 mL/kg/hr for each kg above 20.
The avg (70 kg) adult needs about how many L per day?
2.5L/day (1500 + (20 x 50)=2500) OR 100 mL/hr (2500/24 hrs).
Normal UO for adults
0.5 cc/kg/hr
Normal UO for kids
1 cc/kg/hr
You note flattened T waves, ST depression, and a U wave on a patient’s ECG. Tx?
HYPOKALEMIA. fNo more than 40 mEq should be added to a liter of IV fluid and rate should not exceed 40 mEq/hr. Do not give to oliguric patient.
You note peaked T waves, wide QRS, and ST depression on patients EKG. Tx?
This is hyperkalemia (>5 mEq/L). Could give Kayexalate, a cation exchange resin. Also could give 10% calcium gluconate 1 g IV which temporarily suppresses the myocardial effects but does not move potassium. Also could give albuterol. Additionally, 45 mEq NaHCO3 in 1 L D10W with 20 units of regular insulin would promote cellular repute of K, giving transient relief of hyperkalmia. As a last resort, give dialysis.
How to correct for low albumin in calculating calcium
0.8 (normal albumin-observed albumin) + observed calcium.
How does acidosis and alkalosis affect calcium?
Acidosis causes INCREASE in ionized fraction. Alkalosis causes DECREASE in ionized fraction.
Tx of hypercalcemia
Vigorous volume repletion with salt solution would dilute Ca and increase Ca excretion. This may be augmented with furosemide. However, if the cause is an acute hypercalcemic crisis due to hyperparathyroidism, immediate surgery is the only treatment.
