Ver el código de «Hyponatremia»

==Background==
*Defined as sodium concentration <135meq/L<ref>Upadhyay A, Jaber BL, Madias NE. Epidemiology of hyponatremia. Seminars in Nephrology 2009 29 227–238</ref>
*Patients often not symptomatic until <120meq/L, although this level varies by patients and may be higher if the change occurred abruptly<ref name="Spasovski">Spasovski et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrol Dial Transplant (2014) 0: 1–39. [http://ndt.oxfordjournals.org/content/early/2014/02/21/ndt.gfu040.full.pdf fulltext]</ref>
*Too fast of sodium correction (>10 mmol/L/day), especially if chronic, can cause [[osmotic demyelination syndrome]] (central pontine myelinolysis)<ref name="NEJM">Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000 May 25;342(21):1581-9.</ref>

==Clinical Features==
===Hyponatremia Symptoms by Severity<ref name="Spasovski" />===
{| {{table}}
| align="center" style="background:#f0f0f0;"|'''Severity'''
| align="center" style="background:#f0f0f0;"|'''NOT severe'''
| align="center" style="background:#f0f0f0;"|'''Moderately severe'''
| align="center" style="background:#f0f0f0;"|'''Severe'''
|-
| '''Symptoms'''
||
*Gait disturbances
*Falls
*Concentration
*Cognitive deficits
||
*[[Nausea]] without vomiting 
*[[Confusion]]
*[[Headache]]
||
*[[Vomiting]] 
*Cardiorespiratory distress 
*Abnormal and deep somnolence 
*[[Seizures]]
*[[Coma]] (GCS <8)
|}

===Symptoms from Rapid Correction of Sodium===
*[[CHF]]
*[[Osmotic demyelination syndrome]] (central pontine myelinolysis)
**[[Altered mental status]]
**[[Dysphagia]]
**[[Dysarthria]]
**[[Weakness|Paresis]]

==Differential Diagnosis of '''Hypotonic''' Hyponatremia (by Volume Status)==
===Hypovolemic===
====Renal Causes====
*Thiazide [[diuretic]] use
*Na-wasting nephropathy ([[renal tubular acidosis|RTA]], CKD)
*Osmotic diuresis ([[hyperglycemia|glucose]], urea)
*Aldosterone deficiency

====Extra-renal Causes====
*GI loss
*3rd space loss
*[[Burns]]
*[[Pancreatitis]]
*[[Peritonitis]]

===Hypervolemic===
*Urinary Na >20
**[[Renal failure]]
*Urinary Na <20
**[[Nephrotic syndrome]]
**[[Cirrhosis]]
**[[CHF]]

===Euvolemic===
*[[SIADH]]
**urine sodium is greater than 20-40 mEq/L
*Pain, stress, nausea
*Psychogenic polydipsia
*[[Hypothyroidism]]
*Drugs<ref>Review of Drug-Induced Hyponatremia. Am J Kidney Dis 2008;52:144</ref><ref>Kate M, Grover S.  Bupropion-Induced Hyponatremia.  General Hospital Psychiatry Volume 35, Issue 6, November–December 2013, 681-683.</ref>
**[[NSAIDs]], [[sulfonylurea]], [[bupropion]]
*H<sub>2</sub>0 intoxication
*[[Adrenal insufficiency|Glucocorticoid deficiency]]

===Pseudohyponatremia===
*[[Hyperglycemia]]
**Na+ decreases by 2.4mEq/L for each 100mg/dL increase in glucose over 100mg/dL<ref name="Hillier">Hillier TA, Abbott RD & Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia. American Journal of Medicine 1999 106 399–403</ref>
*Displaced sodium in lab specimen
**[[Hypertriglyceridemia|Hyperlipidemia]]
**Hyperproteinemia

==Evaluation==
===Work-Up===
''Prior to giving treatment''
*Urine
**[[Urinalysis]]
**Urine electrolytes (Urine sodium)
**Urine urea
**urine uric acid
**urine osmolality 
**urine creatinine
*Serum
**Chemistry including Ca/Mg/Phos
**Serum osmolality
**Uric acid
**TSH
**Cortisol

===Diagnosis===
[[File:Hyponatremia correction.png|thumb|True serum sodium (corrected) based on serum glucose<ref name="Spasovski" />]]
[[File:Hyponatremia.png|thumb|Algorithm for hyponatremia diagnosis]]
#Correct for glucose (see table)
#Determine volume status
#Calculated osm (in true hyponatremia the osm is reduced)

====Hypertonic Hyponatremia====
''Defined as osmolarity > 295mmol/L with the following causes:''
#[[Hyperglycemia]]
#*Sodium decreases by 2.4mEq/L for each 100mg/dL increase in glucose over 100mg/dL<ref name="Hillier" />
#[[Mannitol]] excess

====Isotonic (pseudo) hyponatremia====
''Defined as osmolarity > 275-295mmol/L.  Often referred to as pseudo hyponatremia because the elevated lipids or proteins interfere with the laboratory sodium reading.  The following are common causes:''
#Hyperlipidemia
#Hyperproteinemia

====Hypotonic Hyponatremia====
''Defined as an osmolarity < 275 mmol/L and categorized as [[Hyponatremia#Hypovolemic|hypovolemic]], [[Hyponatremia#Hypervolemic|hypervolemic]] or [[Hyponatremia#Euvolemic|euvolemic]]''

==General Management==
''Must have sufficient confidence that the symptoms are '''caused''' by hyponatraemia; see Clinical Features for definition of categories.''

===NOT Severe/Moderately-Severe (Including Asymptomatic)===
'''Adults:<ref name="Spasovski" />''' 
#Start prompt diagnostic assessment and provide cause-specific treatment
#Check serum sodium concentration after 4 hours
#*Aim for a 5 mmol/l per 24-h increase in serum sodium concentration
#*Limit increase to 10 mmol/l in the first 24 h (8 mmol/l during every 24 h thereafter), until a serum sodium concentration of 130 mmol/l is reached
#Manage the patient as in moderately-severe symptomatic hyponatraemia if the serum sodium concentration decreases 10 mmol/l

===Moderately Severe Symptoms===
'''Adults:<ref name="Spasovski" />''' 
#3% hypertonic saline 150 mL bolus over 20 min
#Start prompt diagnostic assessment and provide cause-specific treatment
#Check serum sodium concentration after 1, 6 and 12 hours
#*Aim for a 5 mmol/l per 24-h increase in serum sodium concentration
#*Limit increase to 10 mmol/l in the first 24 h (8 mmol/l during every 24 h thereafter), until a serum sodium concentration of 130 mmol/l is reached
#{{MedicationDose|drug=Desmopressin|dose=2 mcg IV q8h|route=IV|context=Prevent overcorrection of sodium|indication=Hyponatremia|population=Adult}} to prevent overcorrection
#Manage the patient as in severely symptomatic hyponatraemia if the serum sodium concentration further decreases despite treating the underlying diagnosis (2D).

===Severe Symptoms===
'''Adults:<ref name="Spasovski" />''' 
#3% hypertonic saline 150 mL bolus over 20 min
#Check serum sodium concentration after 20 min
#Repeat infusion of 150 ml 3% hypertonic saline for the next 20 min
#Repeat twice or until a target of 5 mmol/l increase in serum sodium concentration is achieved
#*Each 100 mL will raise sodium by ~2 mmol/l
#*In general, 200-400 mL of 3% hypertonic saline is reasonable dose in most adult patients with severe symptomatic hyponatremia, which may be given IV over 1-2 hr until resolution of seizures.  
#If you do not have 3% hypertonic saline you can give two ampules (100ml) of crash cart hypertonic bicarbonate (1 mEq/ml sodium bicarbonate equivalent to giving ~200 ml of 3% saline, which will raise the serum sodium by ~3 mM)<ref>[https://emcrit.org/ibcc/hyponatremia/ Josh Farkas IBCC Hyponatremia]</ref>. 
#*Sodium bicarbonate should be given slowly (each ampule over 5-10 minutes).  Bicarbonate is contraindicated in patients with metabolic alkalosis. 
'''Pediatrics:<ref>Moritz ML, Ayus JC. 100cc 3% sodium chloride bolus: a novel treatment for hyponatremic encephalopathy. Metab Brain Dis. 2010 Mar; 25(1): 91-6.</ref>''' 
*2 mL/kg  of 3% over 10-60 minutes can be infused with a repeat of up to 3 times.

==Cause-Specific Treatment==
===Hypertonic hyponatremia===
*Correct underlying disorder which is often hyperglycemia<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 due to osmotic diuresis and normal saline provides adequate volume repletion

===Isotonic (pseudo) hyponatremia===
*No treatment needed <ref name="treatment"></ref>

===Hypotonic hyponatremia===
#Hypovolemic
#*Give normal saline, but be cautious of raising the serum sodium more than 10 mmol/L/day and causing [[osmotic demyelination syndrome]] (central pontine myelinolysis)''<ref name="Nagler">Nagler EV1, Vanmassenhove J, van der Veer SN et al. Diagnosis and treatment of hyponatremia: a systematic review of clinical practice guidelines and consensus statements.  [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4276109/ BMC Med. 2014 Dec 11;12:1]</ref>''
#Euvolemic<ref name="treatment"></ref>
#*Water restrict
#*Treat underlying cause
#Hypervolemic
#*Water restriction
#*Diuresis
#*Treat underlying cause

==Calculating Sodium Replacement Therapy==
''Max correction 10mEq/L in first 24hr (8 mmol/l during every 24 h thereafter), until a serum sodium concentration of 130 mmol/l is reached (lowers risk of [[osmotic demyelination syndrome]]) <ref name="Nagler" />''
===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

===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% sodium chloride (to avoid volume overload) divide above rate by 3.33

{|class="wikitable"
|+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
|}

==[[DDAVP]] Combined with Hypertonic Saline==
*Limited evidence suggests usage of [[DDAVP]] in combination with HTS can safely increase sodium, while lowering risk for over-correction<ref>Sood L et al. Hypertonic saline and desmopressin: a simple strategy for safe correction of severe hyponatremia. Am J Kidney Dis. 2013 Apr;61(4):571-8.</ref>
**DDAVP prevents free water excretion renally
**Give 3% hypertonic saline based on calculations above
**{{MedicationDose|drug=Desmopressin|dose=1-2 mcg IV q6h|route=IV|context=Combined with hypertonic saline for safe correction|indication=Hyponatremia|population=Adult}}
**Patients must be PO water restricted
*Goal sodium is 6 mEq/L over first 24 hours

==Disposition==
*Admit if symptomatic or if Na <125mEq/L
*Manage severely symptomatic patients in "an environment where close biochemical and clinical monitoring can be provided" (e.g. ICU)

==See Also==
*[[Electrolyte abnormalities]]
*[[Osmotic demyelination syndrome]]

== Calculators ==
{{Corrected Sodium Calculator}}
{{Sodium_Deficit_Calculator}}

{{Serum_Osmolality_Calculator}}

==External Links==
*[https://emcrit.org/ibcc/hyponatremia/ IBCC Hyponatremia Josh Farkas]
*[http://emcrit.org/podcasts/hyponatremia/ EMCrit Hyponatremia Management]
*[http://ddxof.com/electrolyte-abnormalities/ DDxOf: Differential Diagnosis of Electrolyte Abnormalities]
*[https://emcrit.org/pulmcrit/taking-control-of-severe-hyponatremia-with-ddavp/ PulmCrit DDAVP Clamp]

==References==
<references/>
[[Category:FEN]]