Hyponatremia: Difference between revisions

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==Background==
==Background==
*Urine Na only useful before beginning tx
*Defined as sodium concentration <135meq/L
*Low = <135meq/L
*Patients often not symptomatic until <120meq/L although this level varies by patients and may be higher if the change occurred abruptly<ref>Spasovski G. et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrol Dial Transplant. 2014</ref>
*Symptomatic = <120meq/L (may be higher if occurs abruptly)


==Clinical Features==
==Clinical Features==
*N/V
*[[Nausea and Vomiting]]
*Anorexia
*Anorexia
*Muscle cramps
*Muscle cramps
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##Cortisol
##Cortisol


==DDX==
==Types and Causes==
#Hypertonic hyponatremia (osm > 295)
*Often described in terms of tonicity and volume status of the patient <ref>Understanding Lab Testing for Hyponatremia. Clin J Am Soc Nephrol 2008;3:1175</ref>
##[[Hyperglycemia]]
===Hypertonic Hyponatremia ===
###[Na+] decreases by 1.6-1.8mEq/L for each 100mg/dL increase in glucose
*Defined as osmolarity > 295mmol/L with the following causes:
##[[Mannitol]] excess
#[[Hyperglycemia]]
#Isotonic (pseudo) hyponatremia (osm 275-295)
:*[Na+] decreases by 1.6-1.8mEq/L for each 100mg/dL increase in glucose
##Hyperlipidemia
#[[Mannitol]] excess
##Hyperproteinemia
 
#Hypotonic hyponatremia (osm < 275)
===Isotonic (pseudo) hyponatremia===
##Hypovolemic
*Defined as osmolarity > 275-295mmol/L.  Often referred to as pseudo hyponatremia because the elevated lipids or potions interfere with the laboratory sodium reading.  The following are common causes:
###Renal
#Hyperlipidemia
####Thiazide diuretic use
#Hyperproteinemia
####Na-wasting nephroathy (RTA, CRF)
 
####Osmotic diuresis (glucose, urea)
===Hypotonic Hyponatremia===
####Aldosterone deficiency
*Defined as an osmolarity < 275 mmol/L and categorized as hypovolemic, hypervolemic or euvolemic
###Extra-renal
 
####GI loss
====Hypovolemic====
####3rd space loss
#Renal Causes
#####Burns
##Thiazide diuretic use
#####Pancreatitis
##Na-wasting nephroathy (RTA, CRF)
#####Peritonitis
##Osmotic diuresis (glucose, urea)
##Hypervolemic
##Aldosterone deficiency
###Urinary Na > 20
#Extra-renal Causes
####[[Renal Failure]]
##GI loss
###Urinary Na < 20
##3rd space loss
####[[CHF]]
##*Burns
####[[Nephrotic Syndrome]]
##*Pancreatitis
####Cirrhosis
##*Peritonitis
##Euvolemic (urine Na usually > 20)
====Hypervolemic====
###SIADH
#[[Renal Failure]]
####Pain, stress, nausea
#*Urinary Na < 20
###[[Hypothyroidism]]
#[[CHF]]
###Drugs
#*[[Nephrotic Syndrome]]
####NSAIDs, sulfonylureas
#[[Cirrhosis]]
###H20 intoxication
 
###Glucocorticoid deficiency
====Euvolemic====
#SIADH
*urine sodium is greater than 20-40 mEq/L
#Pain, stress, nausea
#[[Hypothyroidism]]
#Drugs<ref>Review of Drug-Induced Hyponatremia. Am J Kidney Dis 2008;52:144</ref>
##NSAIDs, sulfonylureas
#H<sub>2</sub>0 intoxication
#Glucocorticoid deficiency


==Treatment==
==Treatment==
*1. Hypertonic hyponatremia
===Hypertonic hyponatremia===
**Correct underlying disorder
*Correct underlying disorder which is often hypoglycemia<ref name="treatment">Schrier RW, Bansal S. Diagnosis and management of hyponatremia in acute illness. Curr Opin Crit Care 2008;14:627-34</ref>
**Often volume depleted (give NS)
*Often volume depleted due to osmotic diuresis and normal saline provides adequate volume repletion
*2. Isotonic (pseudo) hyponatremia
===Isotonic (pseudo) hyponatremia===
**No tx needed  
*No treatment needed <ref name="treatment"></ref>
*3. Hypotonic hyponatremia
===Hypotonic hyponatremia===
**A. Hypovolemic
#Hypovolemic
***Give NS (see below)
#*Give NS but be cautious of total daily repletion of Na so you avoid causing central pontine demylinosis
**B. Euvolemic
#Euvolemic<ref name="treatment"></ref>
***Water restrict
#*Water restrict
***Treat underlying cause
#*Treat underlying cause
**C. Hypervolemic
#Hypervolemic
***Water restriction
#*Water restriction
***Diuresis
#*Diuresis
***Treat underlying cause
#*Treat underlying cause


===Na Therapy===
===Na Therapy===
*Max correction 10mEq/L in 24hr (avoids CPM)
*Max correction 10mEq/L in 24hr (avoids central pontine demylinosis)
*NS = 154 meq/L
 
*3% NS = 513 meq/L
{|class="wikitable"
*each 100 ml will raise sodium by ~2 mmol/l
|+Sodium Containing fluid Concentrations
| align="center" style="background:#f0f0f0;"|'''Fluid type'''
| align="center" style="background:#f0f0f0;"|'''Sodium Concentration'''
|-
| 1/2 Normal Saline||77 mEq/L
|-
| Normal Saline||154 mEq/L
|-
| Lactated Ringers||130 mEq/L
|-
| 3% Saline||513 mEq/L
|}


====Asymptomatic====
====Asymptomatic====
*Step 1: Calculate total body water
*Step 1: Calculate total body water<ref>The hyponatremia formulas do not work so well (Clin J Am Soc Nephrol 2007;2:1110 and Nephrol Dial Transplant 2006;21:1564)</ref>
**TBW(kg) = Wt(kg) x 0.6 = [Wt(lb) x 0.45] x 0.6 = Wt(lb) x 0.27
**TBW(kg) = Wt(kg) x 0.6 = [Wt(lb) x 0.45] x 0.6 = Wt(lb) x 0.27
*Step 2: Calculate mEq deficit
*Step 2: Calculate mEq deficit
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*[[Electrolyte Abnormalities (Main)]]
*[[Electrolyte Abnormalities (Main)]]


==Source ==
==Sources ==
*Tintinalli
<references/>
*Pontine and extrapontine myelinoslysis: a neurologic disorder following rapid correction of hyponatremia Medicine/ 1993;72(6):359-373
 
*emcrit.org (http://emcrit.org/podcasts/hyponatremia/)
*Review by Schrier (Curr Opin Crit Care 2008;14:627)
*Review of Drug-Induced Hyponatremia (Am J Kidney Dis 2008;52:144)
*Understanding Lab Testing for Hyponatremia (Clin J Am Soc Nephrol 2008;3:1175)
*The hyponatremia formulas do not work so well (Clin J Am Soc Nephrol 2007;2:1110 and Nephrol Dial Transplant 2006;21:1564)


[[Category:FEN]]
[[Category:FEN]]

Revision as of 00:04, 15 August 2014

Background

  • Defined as sodium concentration <135meq/L
  • Patients often not symptomatic until <120meq/L although this level varies by patients and may be higher if the change occurred abruptly[1]

Clinical Features

Diagnosis

  • Must determine volume status and calculated osm
    • In true hyponatremia the osm is reduced

Work-Up

Prior to giving treatment

  1. Urine
    1. UA
    2. Urine electrolytes
    3. Urine urea
    4. urine uric acid
    5. urine osmolality
    6. urine creatinine
  2. Serum
    1. Chemistry
    2. Serum osmolality
    3. Uric acid
    4. TSH
    5. Cortisol

Types and Causes

  • Often described in terms of tonicity and volume status of the patient [2]

Hypertonic Hyponatremia

  • Defined as osmolarity > 295mmol/L with the following causes:
  1. Hyperglycemia
  • [Na+] decreases by 1.6-1.8mEq/L for each 100mg/dL increase in glucose
  1. Mannitol excess

Isotonic (pseudo) hyponatremia

  • Defined as osmolarity > 275-295mmol/L. Often referred to as pseudo hyponatremia because the elevated lipids or potions interfere with the laboratory sodium reading. The following are common causes:
  1. Hyperlipidemia
  2. Hyperproteinemia

Hypotonic Hyponatremia

  • Defined as an osmolarity < 275 mmol/L and categorized as hypovolemic, hypervolemic or euvolemic

Hypovolemic

  1. Renal Causes
    1. Thiazide diuretic use
    2. Na-wasting nephroathy (RTA, CRF)
    3. Osmotic diuresis (glucose, urea)
    4. Aldosterone deficiency
  2. Extra-renal Causes
    1. GI loss
    2. 3rd space loss
      • Burns
      • Pancreatitis
      • Peritonitis

Hypervolemic

  1. Renal Failure
    • Urinary Na < 20
  2. CHF
  3. Cirrhosis

Euvolemic

  1. SIADH
  • urine sodium is greater than 20-40 mEq/L
  1. Pain, stress, nausea
  2. Hypothyroidism
  3. Drugs[3]
    1. NSAIDs, sulfonylureas
  4. H20 intoxication
  5. Glucocorticoid deficiency

Treatment

Hypertonic hyponatremia

  • Correct underlying disorder which is often hypoglycemia[4]
  • Often volume depleted due to osmotic diuresis and normal saline provides adequate volume repletion

Isotonic (pseudo) hyponatremia

  • No treatment needed [4]

Hypotonic hyponatremia

  1. Hypovolemic
    • Give NS but be cautious of total daily repletion of Na so you avoid causing central pontine demylinosis
  2. Euvolemic[4]
    • Water restrict
    • Treat underlying cause
  3. Hypervolemic
    • Water restriction
    • Diuresis
    • Treat underlying cause

Na Therapy

  • Max correction 10mEq/L in 24hr (avoids central pontine demylinosis)
Sodium Containing fluid Concentrations
Fluid type Sodium Concentration
1/2 Normal Saline 77 mEq/L
Normal Saline 154 mEq/L
Lactated Ringers 130 mEq/L
3% Saline 513 mEq/L

Asymptomatic

  • Step 1: Calculate total body water[5]
    • TBW(kg) = Wt(kg) x 0.6 = [Wt(lb) x 0.45] x 0.6 = Wt(lb) x 0.27
  • Step 2: Calculate mEq deficit
    • (Desired Na - Measured Na) ~ must be ≤ 10
  • Step 3: Calculate NS rate to be given over 24hr
    • NS rate (cc/hr) = TBW x mEq deficit x 0.27
      • If using 3% NS (to avoid volume overload) divide above rate by 3.33

Symptomatic

  • 3% NS 100cc bolus over 10min; repeat after 10min x1 if no improvement
    • Each 100 ml will raise sodium by ~2 mmol/l
  • Fluid restrict

Disposition

  • Admit if Na <125

See Also

Sources

  1. ↑ Spasovski G. et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrol Dial Transplant. 2014
  2. ↑ Understanding Lab Testing for Hyponatremia. Clin J Am Soc Nephrol 2008;3:1175
  3. ↑ Review of Drug-Induced Hyponatremia. Am J Kidney Dis 2008;52:144
  4. ↑ 4.0 4.1 4.2 Schrier RW, Bansal S. Diagnosis and management of hyponatremia in acute illness. Curr Opin Crit Care 2008;14:627-34
  5. ↑ The hyponatremia formulas do not work so well (Clin J Am Soc Nephrol 2007;2:1110 and Nephrol Dial Transplant 2006;21:1564)
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