체액량의 장애
- Effective circulating volume 이 중요
1. Decreased effective (arterial) circulating volume
1) Decreased ECF volume
- Extra-renal loss: vomiting, diarrhea, sweating, burn, hemorrhage
- Renal loss: diuretics, osmotic diuresis, hypoaldosteronism, diabetes insipidus,
2) Normal or increased ECF (interstitial, venous) volume
- Heart failure
- Tissue redistribution: capillary leak, hypoalbuminemia with LC, nephrotic syndrome
- Sepsis (vascular tone↓, venous pooling↑, permeability↑)
2. Increased effective (arterial) circulating volume
- Primary aldosteronism, SIADH
- Acute glomerulonephritis, End stage renal disease
Hyponatremia ( Na < 135 )
1.ADH mediated water retention: ADH 증가
1) Effective circulating volume depletion
① Decreased ECF volume (primary sodium loss)
- Extra-renal loss: vomiting, diarrhea, sweating, burn, hemorrhage
- Renal loss: diuretics, osmotic diuresis, hypoaldosteronism, cerebral salt wasting (by BNP)
② Increased ECF volume (primary sodium gain) ; usually associated with edema
- Heart failure: poor prognosis factor
- Hepatic cirrhosis: poor prognosis factor
- Nephrotic syndrome
2) SIADH
3) Hormonal changes
① Adrenal insufficiency
- Cortisol이 안 나와 ADH에 대한 음성피드백 안됨
- Primary adrenal insufficiency: aldosterone 분비 장애: volume depletion, BP ↓: ADH ↑
- Secondary adrenal insufficiency: aldosterone 분비 유지 : euvolemic hyponatremia
② Hypothyroidism: Cardiac output ↓(effective volume 감소) : ADH ↑
2. Non-ADH mediated water retention : ADH 감소 or 일정
1) Advanced renal failure : 물 배설 불가
2) Primary polydipsia
- > 12L/day or concurrent SIADH
- psychiatric illness with antipsychotic drug (dry mouth)
3) Beer drinker’s potomania
- low protein intake + large volume of beer
- low urine solute (osmole) excretion: 200mosm/day
- low max urine volume: 200/50=4L/day
3. Sodium loss mixed with volume depletion: Thiazide diuretics
4. Pseudohyponatremia
Hyperglycemia, Mannitol, Hyperlipidemia, Glycine
Major steps in the initial evaluation of hyponatremia
1) Plasma osmolality
A. Low: true hyponatremia
B. Normal/elevated: pseudohyponatremia or renal failure (azotemia)
2) Urine osmolality
A. <100 mosmo1/kg: primary polydipsia (non-ADH mediated)
B. >100 mosmo1/kg: other causes of true hyponatremia in which water excretion is impaired (ADH mediated)
3) Urine sodium concentration
A. Less than 25 meq/L: effective circulating volume depletion (including heart failure and hepatic cirrhosis)
B. Greater than 40 meq/L: SIADH, diuretics (when drug still acing), adrenal insufficiency, hypothyroidism patients with vomiting, osmotic diuretics, salt losing nephropathy
Hypernatremia ( Na > 145 )
1. Non-renal loss
1) Skin: sweating (insensible), fever, exercise, heat exposure, burns
2) Respiratory tract (insensible): mechanical ventilation
3) Gastrointestinal tract: diarrhea, Osmotic and Viral gastoenteritidis
cf. Secretory diarrhea (cholera): hyponatremia
2. Renal loss
1) Drug: Loop diuretics interfere with the countercurrent mechanism and decrease medullary interstitial tonicity
2) Osmotic diuresis by non-reabsorbed organic solutes (urine osmole excretion rate>750mosmo/day)
- Hyperglycemia and glucosuria in poorly controlled DM
- IV administration of mannitol
- Increased endogenous urea production (high-protein diet)
3) Diabetes insipidus (ADH 분비,반응 ↓)
Major steps in the initial evaluation of hypernatremia
1) Minimum volume of maximally concentrated urine
- Urine volume < 500mL/day & Urine osmolality > 800mosm/kg
-> Non-renal loss
2) Urine osmole excretion rate > 750mosmol/day
-> Osmotic diuresis
3) Renal response to desmopressin
- Urine osmolality increased: CDI
- Urine osmolality unchanged: NDI