Chapter 9 - Fluids and Electrolytes Flashcards
% body that is water?
2/3 (men); infants with a little more, women with a little less
% TBW that is intracellular?
2/3
% of TBW that is extracellular?
1/3
% of extracellular water that is interstitial?
3/4
% of extracellular water that is in plasma?
1/4
What determines the plasma/interstitial compartment osmotic pressures?
Proteins
What ion determines the intracellular/extracellular osmotic pressure?
Na
Composition of 0.9 NS?
Na 154, Cl 154
Composition of LR?
Na 130, K 4, Ca 2.7, Cl 109, bicarb 28
Normal plasma osmolarity?
280-295
What is the best indicator of adequate volume replacement?
Urine output
What are the insensible fluid lossess in a day?
10ml/kg/day; 75% skin, 25% respiratory
Why switch to D5 1/2 NS after 24h?
5% dextrose will stimulate insulin release, resulting in amino acid uptake and protein synthesis (prevents protein catabolism)
How much glucose will D51/2NS @ 125 provide?
150g glucose per day
Amount of fluid secreted by the stomach?
1-2L/day
Amount of fluid secreted by the biliary system?
500-1000ml/day
Amount of fluid secreted by the pancreas?
500-1000ml/day
Amount of fluid secreted by the duodenum?
500-1000ml/day
What is the normal K+ requirement?
0.5-1 mEq/kg/day
What is the normal Na+ requirement?
1-2 mEq/kg/day
Which secretion has the highest concentration of K+ in the body?
Saliva
Fluid replacement for gastric losses?
D51/2NS w/ 20 of K
Fluid replacement for pancreatic, biliary, small intestine losses?
LR with HCO3-
Fluid replacement for large intestine losses?
LR with K+
At what rate should GI losses be replaced?
cc/cc
Treatment for hyperkalemia?
Calcium gluconate (membrane stabilizer), sodium bicarb (causes alkalosis, KI enters cell in exchange for H), 10U insulin and 1 amp of 50% dextrose, kayexalate, dialysis
EKG findings with hypokalemia?
Loss of T waves
Symptoms of hypernatremia?
Restlessness, irritability, ataxia, seizures
How do you calculate the free water deficit?
0.6 x pt’s wt (kg) x [(Na+/140)-1]
How do you calculate the water requirement?
(Desired change in Na over 1 days x TBW)/(Desired Na+ after giving water requirement)
Rate at which you should change Na?
No more than 0.7 mEq/h (16 mEq/day)
Symptoms of hyponatremia?
Headaches, delirium, seizures, nausea, vomiting
How do you calculate the sodium deficit?
0.6 x (weight in kg) x (140 - Na)
Treatment for hyponatremia?
Water restriction, then diuresis, then NaCl replacement
Why correct hyponatremia slowly?
To avoid central pontine myelinosis (no more than 1 mEq/h
Most common malignant cause of hypercalcemia?
Breast cancer
Treatment for hypercalcemia?
NS @ 200-300/hr, lasix; NO LR or thiazide diuretics
Symptoms of hypocalcemia?
Hyperreflexia, Chvostek’s sign, perioral tingling and numbness, Trousseau’s sign, prolonged QT
What is the protein adjustment for calcium?
For ever 1g decrease in protein, add 0.8 to Ca
Which patients get hypermagnesemia?
Burn, trauma, renal dialysis pts
Treatment for hypermagnesemia?
Calcium
What is the anion gap?
Na - (HCO3 + Cl); normal <10-15
What causes anion gap acidosis?
Methanol, Uremia, Diabetic ketoacidosis, Paraldehydes, Isoniazid, Lactic acidosis, Ethylene glycol, Salicylates
What causes normal gap acidosis?
Due to loss of Na/HCO3- (ileostomies, small bowel fistulas)
Treatment of metabolic acidosis?
Treat underlying cause; keep pH >7.2 with bicarb, severely decreased pH can affect myocardial contractility
What causes metabiolic alkalosis?
Usually a contraction alkalosis; NGT (hypochloremic, hypokalemic and paradoxical aciduria)
What causes the paradoxical aciduria of metabolica alkalosis?
Na+/H+ excanger activated in effort to reabsorb water, plus K+/H+ exchanger in an effort to reabsorb K+ leads to H+ in the urine
What causes hypokalemia in metabolic alkalosis?
Loss of water causes kidney to reabsorb Na in exchange for K, losing K
What is the best test for azotemia?
FeNa = (urine Na/Cr)/(plasma Na/Cr)
What is the FeNa, urine Na, and BUN/Cr ratio in a prerenal patient?
- FeNa <1
- Urine Na <20
- BUN/Ct >20
Why is myoglobin toxic to renal cells?
Converted to ferrihemate in acid environment
What is the treatment of myoglobinuria?
Alkalinize urine
What is tumor lysis syndrome?
Release of purines and pyramidines which leads to increased PO4 and uric acid as well as decreased Ca
Treatment for tumor lysis syndrome?
Hydration, allopurinol, diuretics, alkalinization of urine
Metabolism of Vitamin D?
Made in skin (UV rays) from 7-dehydrocholesterol –> to liver for (25-OH) –> to kidney for (1-OH)
What does the active form of Vitamin D do?
Increases calcium-binding protein, leading to increased intestinal Ca absorption
What are the effects of chronic renal failure on Vit D and Ca?
Decreased active vitmain D (dec. 1-OH hydroxylation) leading to decreased Ca reabsorption from gut
Why does chronic renal failure cause anemia?
Low erythropoietin
What are the effects of increased Angiotensin II from decreased ECV?
Increase CO, increased peripheral resistance; increased sympthetic nerve activity; increased aldosterone; decreased renal blood flow, decreased GFR
