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
What is the protein adjustment to calcium?
For every 1 gram decrease in protein (IE albumin), add 0.8 to Ca
What are the drugs that can be given to treat hyperkalemia?
- Calcium gluconate: Membrane stabilizer for heart to prevent arrhythmias
- Sodium bicarbonate: Causes alkalosis, drives K+ into cells in exchange for H+
- Insulin (10 units) and glucose (1 ampule of 50% dextrose): K+ driven into cells with glucose
- Kayexalate: Draws K+ into large intestine for excretion
[Can also dialyze the patient.]
High plasma levels of what can cause pseudohyponatremia?
Hyperglycemia
[For each 100 increment of glucose over normal, add 2 points to the Na value.]
What is the treatment for tumor lysis syndrome?
- Hydration is the best treatment
- Rasburicase converts uric acid into inactive metabolite allantoin
- Allopurinol decreases uric acid production
- Diuretics
- Alkalinization of urine
How is vitamin D-synthesized in the body?
- It is made in the skin (UV light converts 7-dehydroxycholesterol to cholecalciferol)
- Cholecalciferol goes to liver for 25-OH and then the kidney for 1-OH yielding the active form of vitamin D
- The active form of vitamin D increases calcium-binding protein leading to increased intestinal Ca absorption
What is the normal sodium concentration of sweat?
35-65 mEq
What are the signs of the below conditions on ECG?
- Hyperkalemia
- Hypokalemia
- Hyperkalemia: Peaked T-waves
- Hypokalemia: Absent T-waves
[Hyperkalemia often occurs in renal failure. Hypokalemia often occurs in setting of overdiuresis.]
What is the composition of lactated ringer solution?
- Na: 130 mEq
- K: 4 mEq
- Cl: 109 mEq
- Ca: 2.7 mEq
- Bicarb: 28 mEq
[pH is 6.5]
Which fluid type should be used to replace fluids after major adult gastrointestinal surgery?
- During operation and continued for first 24 hours: Lactated ringer solution
- After 24 hours: Switch to D5 1/2 NS with 20 mEq K+
[5% dextrose will stimulate insulin release, resulting in amino acid uptake and protein synthesis (also prevents protein catabolism). D5 1/2 NS @ 125 cc/hr provides 150g of glucose per day (525 kcal/day).]
