Water, Electrolytes And Acid Base Flashcards
Norma osmolality of plasma
280-300 mOsm/kg
Factors stimulating aldosterone release and its effects
Decreased ECF volume
Retains Na
Factors stimulating ADH release and its effects
Increased osmolality
Reabsorption of water from renal tubules
Factors stimulating renin release and its effects
Decreased ECF volume
Decreased BP
Salt depletion
Prostaglandins
Thirst, water and salt reabsorption
Causes of dehydration
Diarrhea Vomiting Excess sweating Fluid loss in burns Adrenocorticoid dysfunction Kidney disease
Features of dehydration
ECF volume decreases
Electrolyte concentration increases
Water is drawn from ICF. Cells shrink
Electrolytes are lost
C/F Pulse rate inc. BP dec. Sunken eyeballs Lethargy, confusion
Treatment for dehydration
Intake of water orally/nasogastric tube/IV
If only decrease in Na - Normal saline
If decrease in both Na and H2O - dextrosesaline
Na RDA
5-10g/day
Normal ECF conc of Na
135-145mEq/L
Causes of hyponatremia
Vomiting Diarrhea Burns Addison's Nephrotic syndrome ACE inhibitors Lithium Vasopressin
S/S of hyponatremia
Cramps Headache Nausea Lethargy Tremors Oliguria
SIADH
Syndrome of inappropriate secretion of ADH Hyponatremia: Na - <135 mEq/L Urine Na - >20mmol/L Urine osmolality - >100mOsm/kg Normal GFR Normal serum creatinine and urea
Edema in congestive heart failure
Both Na and water are retained
- In early stages, hydrostatic pressure on venous side is increased
- Water is primarily retained
- Causes dilution of Na concentration triggering aldosterone secretion
- Sodium is also retained
- Vicious cycle broken by administration of aldosterone antagonists.
Hypernatremia causes
Cushings Pregnancy Hyperaldosteronism Excess intake of salts Amplicillin, tetracyclin
S/S of hypernatremia
Dry mucous membranes
Fever
Thirst
Restlessness
Hypertonic hyponatremia
- Due to other osmotically active particles in serum causing shift of water to ECF
- for every 100mg/dl of glucose, serum Na drops by 1.6 mmol/L
- above 400mg/dl, serum Na drops by 2.4 mmol/L for every 100mg
- increased glucose leads to increased osmolality.
Normotonic hyponatremia
- severe hyperlipidemia and paraproteinemia lead to low measured serum sodium levels
- pseudohyponatriemia
Treatment of hyponatremia
- Rapid correction in acute works but in chronic can lead to neurological problems
- water restriction, increased salt intake, furosemide, anti- ADH drugs
Potassium RDA
3-4g/day
K normal plasma levels
3.5-5 mEq/L
In cells 160 mEq/L
K normal plasma levels
3.5-5 mEq/L
In cells 160 mEq/L
Causes of hypokalemia
Cushings Hyperaldosteronism Renal tubular acidosis Alkalosis Insulin therapy Thiazides
S/S of hypokalemia
Below 3mmol/L Muscle weakness Cramps Hypotension Arrhythmias T wave is inverted
Causes of hyperkalemia
Addison's Renal failure Necrosis Pseudohyperkalemia ACE inhibitors Beta blockers
S/S of hyperkalemia
Above 5.5 mmol/L
Flaccid paralysis
Bradycardia
Elevated T wave
Normal plasma bicarbonate concentration
22-26 mmol/L
pH of urine
6.0
Respiratory acidosis
Increased pCO2 and H+
- Severe asthma
- pneumonia
- COPD
Respiratory alkalosis
Decreased pCO2 and H+
- High altitude
- hyperventilation
- septicemia
Metabolic acidosis
Excess production of ketone bodies Excess excretion of bicarbonate -DM -starvation -renal failure -lactic acidosis -renal tubular acidosis
Metabolic alkalosis
Loss of H+
- vomiting
- cushings
Anion gap
12-18 mEq/L
