9: Fluids and Electrolytes Flashcards
What is the composition and pH of normal saline?
- Na: 154 mEq
- Cl: 154 mEq
[pH is 5.5]
Which body fluid has the highest concentration of K+?
Saliva
What determines the plasma/interstitial and the intracellular/extracellular osmotic pressures?
- Plasma/interstitial: Protein
- Intracellular/extracellular: Sodium
What are the symptoms of hypernatremia?
- Restlessness
- Irritability
- Seizures
[Usually from dehydration. Correct with D5 water slowly to avoid brain swelling.]
What should be used to replace fluid loss from the following sources?
- Stomach
- Pancreatic/biliary/small intestine
- Large intestine
- Generalized dehydration
- Stomach: D5 1/2 NS with 20 mEq K+
- Pancreatic/biliary/small intestine: Lactated ringer with HCO3-
- Large intestine: Lactated ringer with K+
- Generalized dehydration: Normal saline
[GI losses should generally be replaced cc for cc.]
What is the most common malignant and most common benign causes of hypercalcemia?
- Malignant: Breast cancer
- Benign: Hyperparathyroidism
What should one avoid administering to a patient with hypercalcemia?
- Lactated ringer solution (contains Ca)
- Thiazide diuretics (causes retention of calcium)
Why does hypochloremic, hypokalemic metabolic alkalosis from vomiting or nasogastric suctioning result in paradoxical aciduria?
- Loss of Cl- and H- ions from the stomach (hypochloremia and alkalosis)
- Loss of water causes kidney to reabsorb Na in exchange for K+ thus losing K+ (hypokalemia)
- Na+/H- exchanger activated in an effort to reabsorb water along with K+/H- exchanger in an effort to reabsorb K result in paradoxical aciduria
What is the best indicator of adequate volume replacement?
Urine output
[4 cc/kg/hr for 1st 10kg, 2 cc/kg/hr for 2nd 10kg, 1 cc/kg/hr for each kg after that. During open operations, fluid loss is 0.5-1.0 L/hr unless ther are measurable blood losses. Usually unecessary to replace blood lost unless it is >500cc.]
What is the treatment for hypercalcemia?
- Normal saline at 200-300 cc/hr
- Lasix
[For malignant disease, mithramycin, calcitonin, alendronic acid, and dialysis.]
What is the normal daily requirement of Na+ and K+?
- Na: 1-2 mEq/kg/day
- K: 0.5-1.0 mEq/kg/day
How much insensible fluid is lost each day?
10 cc/kg/day
[75% is lost from skin, 25% from respiratory tract.]
What are the symptoms of hypocalcemia?
- Hyperreflexia
- Chvostek’s sign (tapping face produces twitching)
- Perioral tingling and numbness
- Trousseau’s sign (carpopedal spasm)
- Prolonged QT interval
[Calcium usually must be <8 or ionized calcium <4 for symptoms to manifest. Mg may need to be replaced in order to correct Ca.]
What is the formula for plasma osmolarity?
Plasma osmolarity = (2 x Na) + (Glucose / 18) + (BUN / 2.8)
[Normal plasma osmolarity is 280-295.]
Why is myoglobin nephrotoxic and what is the treatment?
- Myoglobin is converted to ferrihemate in acidic environments which is toxic to renal cells
- Treatment is alkalinization of the urine