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What % of the total body weight is water?
- 1) Roughly 2/3 of total body weight is water (men)
- 2) infants have a little more body water
- 3) Women have a little less
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What percentages are in which compartments?
- 1) 2/3 of water weight is intracellular (mostly muscle
- 2) 1/3 of water is extracellular
- 1- 2/3 of extracellular water is interstitial
- 2- 1/3 of extracellular water is plasma
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What determines plasma/interstial compartment osmotic pressures?
Proteins determine plasma/interstitial compartment osmotic pressures
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What determines intracellular/extracellular osmotic pressure?
Na determines intracellular/extracellular osmotic pressure
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Volume overload:
- 1) most comon cause is iatrogenic
- 2) first sign is weight gain
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What cellular process can release a significant amount of H20
cellular catabolism
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0.9% normal saline:
Na 154 and Cl 154
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Lactate Ringer's solution:
- 1) LR; ionic composition of plasma:
- 2)
- Na-130
- K-4
- Ca- 2.7
- Cl- 109
- Bicarb- 28
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Formula for plasma osmolarity:
(2 x Na)+(glucose/18)+(BUN/2.8)
Normal= 280-295
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Estimates of volume replacement:
- 1) 4cc/kg/h for 1st 10kg
- 2) 2cc/kg/h for 2nd 10kg
- 3) 1cc/kg/hr for each kg after that
- 4) best indicator of adequate volume replacement is urine output
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What is the fluid loss in open abdominal operations:
During open abdominal operations, fluid loss is 0.5-1.0L/h unless there are measurable blood losses
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At what point do you need to replace blood loss?
usually do not have to replace blood loss unless it is >500cc
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Insensible fluid losses:
- 1) 10cc/kg/day
- 1- 75% skin
- 2- 25% respiratory
- 3- pure water
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IV replacement after major adult gastrointestinal surgery:
- 1) during operation and 1st 24 hours, use LR2) After 24 hours, switch to D5 1/2 NS with 20mEq K1- 5% dextrose will stimulate insulin release, resulting in amino acid uptake and protein synthesis (also prevents protein catabolism)
- 2- D5 1/2NS @ 125/h provides 150g glucose per day (525kcal/day)
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GI fluid secretion:
- Stomach: 1-2L/day
- Biliary System: 500-1,000 ml/day
- Pancreas: 500-1,000 ml/day
- Duodenum: 500-1,000 ml/day
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Normal K+ requirement:
Normal Na+ requirement:
- Normal K+ requirement: 0.5-1 mEq/kg/day
- Normal Na+ requirement: 1-2 mEq/kg/day
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Electrolyte losses:
Sweat-
Saliva-
Stomach-
Pancreas-
Bile-
Small Intestine-
Large Intestine-
- Sweat- hypotonic
- Saliva- K+ (highest concentration of K+ in the body)
- Stomach- H+ and Cl-
- Pancreas: HCO3-
- Bile- HCO3-
- Small Intestine- HCO3-, K+
- Large Intestine- K+
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What do you replace gastric losses with?
Gastric losses- replacement is D5 1/2NS with 20mg K+
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What do you replace pancreatic/biliary/small intestine losses with?
replacement is LR with HCO3-
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What do you replace Large intestine (diarrhea) losses with?
replacement is LR with K+
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How is volume of GI losses replaced?
GI losses- should generally be replaced cc/cc
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What should urine output be kept at?
Urine output- should be kept at least 0.5cc/kg/h; should not be replaced, usually a sign of normal postoperative diuresis
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Potassium:
1) Normal: 3.5-5
- 2) Hyperkalemia- peaked T waves initial finding on EKG
- 1- calcium gluconate (membrane stabilizer for the heart)
- 2- sodium bicarbonate (causes alkalosis, K enters cell in exchange for H)
- 3- 10U insulin and 1 ampule of 50% dextrose (K driven into cells along with glucose)
- 4- kayexalate
- 5- dialysis if refractory
- 3) Hypokalemia- T waves disappear
- 1- may need to replace Mg+ before you can correct K+
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Sodium:
1) Normal: 135- 145
- 2) Hypernatremia- restlessness, irritability, ataxia, seizures
- 3) Correct with D5 water slowly to avoid brain swelling
- 4) Total free water deficit =
- 0.6 x patient's weight (kg) x [(Na+/140)-1]
- 5) Water Requirement:
- [desired change in Na+ over 1 day x TBW]/
- [desired Na+ after giving the water requirement]
- 1- TBW (total body water)= 0.6 x patient's weight (kg)
- 2- Change Na more than 0.7mEq/h (16mEq/day for below)
- 3- for the equation above, if the Na was 165 for a 70kg man: (16x42)/149= 4.5L
- 4) Hyponatremia- headaches, delirium, seizures, nausea,vomiting
- 1- Na deficit= 0.6 x (weight in kg) x (140-Na)
- 2- Water restriction is the first treatment of hyponatremia, then diuresis, then NaCl replacement
- 3- Correct Na slowly to avoid central pontine myelinosis (no more than 1mEq/h)
- 4- Hyperglycemia can cause pseudohyponatremia- for each 100 increment of glucose over normal, add 2 points to the Na value
- 5- SIADH results in hyponatremia
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Calcium
- 1) Normal: 8.5-10; Normal ionized Ca- 4.4-5.5
- 2) Hypercalcemia (Ca usually >13 or ionized >6-7)- causes lethargic state
- 1- breast Ca most common malignant cause
- 2- no lactate ringer's (contains Ca2+)
- 3- no thiazide diurectics (these retain Ca2+)
- 4- Tx: NS at 200-300cc/h, Lasix
- 1- for malignant disease- mithramycin, calcitonin, aledronic acid, dialysis
- 3) Hypocalcemia (Ca usually <8 or ionized Ca <4)- 1- hyperreflexia
- 2- Chvostek's sign (tapping on face produces twitching)
- 3- perioral tingling and numbness
- 4- Trousseau's sign (carpopedial spasm)
- 5- prolonged QT interval
- 4) may need to correct Mg before being able to correct Ca
- 5) Protein adjustment for calcium- for every 1g decrease in protein, add 0.8 to Ca
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Magnesium:
- 1) Normal: 2.0-2.7
- 2) Hypermagnesemia- causes lethargic state; burn, trauma, and renal dialysis patients.
- 1- Tx: calcium
- 3) Hypomagnesemia- signs similar to hypocalcemia
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Metabolic Acidosis: (following slides):
-
Anion gap:
Anion gap = Na - (HCO3 + Cl)
Normal <10-15
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Anion gap acidosis:
"MUDPILES"
- Methanol
- Uremia
- Diabetic ketoacidosis
- Paraldehydes
- Isoniazide
- Lactic acidosis
- Ethylene glycol
- Salicylates
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Normal gap acidosis:
1) usually due to loss of Na/HCO3- (ileostomies, small bowel fistulas)
-
Treatment of metabolic acidosis:
- 1) keep pH > 7.2 with bicarbonate
- 2) Severely decreased pH can affect myocardial contractility
-
Metabolic alkalosis:
- 1) usually a contraction alkalosis
- 2) Nasogastric suction- results in hypochloremic, hypokalemic, metabolic alkalosis, and paradoxical aciduria
- 3) Loss of Cl- and H ion from stomach secondary to nasogastric tube (hypochloremia and alkalosis)
- 4) Loss of water causes kidney to reabsorb Na in exachange for K (Na/K ATPase), thus losing K+ (hypokalemia)
- 5) Na/H exchanger activated in an effort to reabsorb water along with K/H exchanger in an effort to reabsorb K--> results in paradoxical aciduria
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Acid-Base Balance:
- Respiratory acidosis:
- pH: low
- CO2: high
- HCO3: high
- Respiratory alkalosis:
- pH: high
- CO2: low
- HCO3: low
- Metabolic acidosis:
- pH: low
- CO2: low
- HCO3: low
- Metabolic alkalosis:
- pH: high
- CO2: high
- HCO3: high
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Henderson-Hesselbach equation:
pH= pK + log [HCO3-]/[CO2]
Ratio of base to acid (HCO3- to CO2) of 20:1 = pH of 7.4
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Acute renal failure:
FeNa = (urine Na/Cr) / (plasma Na/Cr) = best test for azotemia
- Prerenal:
- 1- FeNa <1%
- 2- urine Na<20
- 3) BUN/Cr ratio >20
- 4- Urine osmolality >500mOsm
70% of renal mass must be damaged before theres an increase in BUN + Cr
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Contrast dyes-
1) volume expansion best prevents renal damage: HCO3- and N-acetylcysteine gtt
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Myoglobin
- 1) converted to ferrihemate in acidic environment, which is toxic to renal cells
- 2) Tx: alkalinize urine
-
Tumor lysis syndrome:
- 1) release of purines and pyrimidines leads to increased PO4 and uric acid, decreased Ca
- 2) Can result in:
- 1- increased BUN and Cr
- 2- EKG changes
- 3) Tx:
- 1- hydration
- 2- diuretics
- 3- allopurinol (decreased uric acid production)
- 4- alkalinization of urine
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Vitamin D
- cholecalciferol
- 2) made in skin (UV sunlight) from 7-dehydrocholesterol
- 3) goes to liver for (25-OH), then kidney for (1-OH). This creates active form of vitamin D
- 4) active form of vitamin D- increases calcium-binding protein, leading to increased intestinal calcium absorption
-
Chronic renal failure:
- 1) decreased active vitamin D (decreased 1-OH hydroxylation)--> decreases Ca reabsorption from gut (decreased Ca-binding protein)
- 2) Anemia- from low erythropoietin
-
See image on pg 42: Multiple effects of increased angiotensin II release in response to the stimulus of decreased extracellular volume
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Transferrin:
transporter of iron
-
Ferritin
storage form of iron
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