By

Dr:-FATIMA EYAD AL GLAD

• Definition• Epidemiology• Physiology• Pathophysiology• Types• Clinical Manifestations• Diagnosis • Treatment

• Definition:– Commonly defined as a serum sodium concentration

135 meq/L

– Hyponatremia represents a relative excess of water in relation to sodium.

Epidemiology:FrequencyHyponatremia is the most common electrolyte disorderincidence of approximately 1%prevalence of approximately 2.5%surgical ward, approximately 4.4%

30% of patients treated in the intensive care unit

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Epidemiology Cont.›Mortality/Morbidity

Acute hyponatremia (developing over 48 h or less) are subject to more severe degrees of cerebral edema

sodium level is less than 105 mEq/L, the mortality is over 50%

Chronic hyponatremia (developing over more than 48 h) experience milder degrees of cerebral edema

Brainstem herniation has not been observed in patients with chronic hyponatremia

Epidemiology Cont.›Age

Infants fed tap water in an effort to treat symptoms of

gastroenteritis Infants fed dilute formula in attempt to ration

Elderly patients with diminished sense of thirst, especially when physical infirmity limits independent access to food and drink

Physiology›Serum sodium concentration

regulation:stimulation of thirst

secretion of ADHfeedback mechanisms of the

renin-angiotensin-aldosterone system

renal handling of filtered sodium

Physiology Cont.›Stimulation of thirst

Osmolality increasesMain driving force

Only requires an increase of 2% - 3%

Blood volume or pressure is reducedRequires a decrease of 10% - 15%

Thirst center is located in the anteriolateral center of the hypothalamus

Respond to NaCL and angiotensin II

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Physiology Cont.›extracellular-fluid and intracellular-fluid

compartments make up 40 percent and 60 percent of total body water

›renal handling of water is sufficient to excrete as much as 15-20 L of free water per day

›sodium is the predominant osmole in the extracellular fluid (ECF) compartment and serum

Pathophysiology›hyponatremia can only occur when some

condition impairs normal free water excretion

›acute drop in the serum osmolality:neuronal cell swelling occurs due to the

water shift from the extracellular space to the intracellular space

Swelling of the brain cells elicits 2 responses for osmoregulation, as follows:

It inhibits ADH secretion and hypothalamic thirst center

immediate cellular adaptation

TypesHypovolemic hyponatremia

Euvolemic hyponatremiaHypervolemic hyponatremiaRedistributive hyponatremia

Pseudohyponatremia

develops as sodium and free water are lost and/or replaced by inappropriately hypotonic fluids

Sodium can be lost through renal or non-renal routes

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Nonrenal loss›GI losses

Vomiting, Diarrhea, fistulas, pancreatitis›Excessive sweating

›Third spacing of fluids ascites, peritonitis, pancreatitis, and burns

›Cerebral salt-wasting syndrometraumatic brain injury, aneurysmal

subarachnoid hemorrhage, and intracranial surgery

Must distinguish from SIADH

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›Renal LossAcute or chronic renal insufficiency

Diuretics

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Normal sodium stores and a total body excess of free waterPsychogenic polydipsia, often in psychiatric patients

Administration of hypotonic intravenous or irrigation fluids in the immediate postoperative period

›administration of hypotonic maintenance intravenous fluids

›Infants who may have been given inappropriate amounts of free water

›bowel preparation before colonoscopy or colorectal surgery

SIADH›downward resetting of the osmostat

›Pulmonary DiseaseSmall cell, pneumonia, TB, sarcoidosis

›Cerebral DiseasesCVA, Temporal arteritis, meningitis,

encephalitis

›MedicationsSSRI, Antipsychotics, Opiates, Depakote,

Tegratol

Total body sodium increases, and TBW increases to a greater extent .

Can be renal or non-renalacute or chronic renal failuredysfunctional kidneys are unable to excrete the ingested sodium load

cirrhosis, congestive heart failure, or nephrotic syndrome

›Water shifts from the intracellular to the extracellular compartment, with a

resultant dilution of sodium. The TBW and total body sodium are unchanged .

This condition occurs with hyperglycemiaAdministration of mannitol

Pseudohyponatremia›The aqueous phase is diluted by excessive

proteins or lipids. The TBW and total body sodium are unchanged .

hypertriglyceridemiamultiple myeloma

Clinical Manifestations ›most patients with a serum sodium

concentration exceeding 125 mEq/L are asymptomatic

›Patients with acutely developing hyponatremia are typically symptomatic at

a level of approximately 120 mEq/L›Most abnormal findings on physical

examination are characteristically neurologic in origin

›patients may exhibit signs of hypovolemia or hypervolemia

Diagnosis›CT head, EKG, CXR if symptomatic›Repeat Na level›Correct for hyperglycemia›Laboratory tests provide important initial

information in the differential diagnosis of hyponatremia

Plasma osmolality Urine osmolality Urine sodium concentration Uric acid levelFeNa

Laboratory tests Cont.›Plasma osmolality

normally ranges from 275 to 290 mosmol/kgIf >290 mosmol/kg :

Hyperglycemia or administration of mannitol

If 275 – 290 mosmol/kg: hyperlipidemia or hyperproteinemia

If <275 mosmol/kg: Eval volume status

Laboratory tests Cont.›Plasma osmolality < 275 mosmol/kg

Increased volume:CHF, cirrhosis, nephrotic syndrome

Euvolemic SIADH, hypothyroidism, psychogenic polydipsia,

beer potomania, postoperative states

Decreased volumeGI loss, skin, 3rd spacing, diuretics

Laboratory tests Cont.›Urine osmolality

Normal value is > 100 mosmol/kgNormal to high:

Hyperlipidemia, hyperproteinemia, hyperglycemia, SIADH

>100 mosmol/kghypoosmolar hyponatremia

Excessive sweatingBurnsVomitingDiarrheaUrinary loss

Laboratory tests Cont.›Urine Sodium

<20 mEq/L SIADH, diuretics

>20 mEq/Lcirrhosis, nephrosis, congestive heart failure, GI

loss, skin, 3rd spacing, psychogenic polydipsia

›Uric Acid Level >4 mg/dl consider SIADH

›FeNaHelp to determine pre-renal from renal

causes

Treatment›four issues must be addressed

Asymptomatic vs. symptomaticacute (within 48 hours)

chronic (>48 hours)Volume status

›1st step is to calculate the total body watertotal body water (TBW) = 0.6 × body weight

• Treatment Cont .›next decide what our desired correction

rate should be›Symptomatic

immediate increase in serum Na level by 8 to 10 meq/L in 4 to 6 hours with hypertonic saline is recommended

›acute hyponatremiamore rapid correction may be possible

8 to 10 meq/L in 4 to 8 hours

›chronic hyponatremiaslower rates of correction

12 meq/L in 24 hours

›Symptomatic or AcuteTreatment Cont. - Here comes the Math!!!estimate SNa change on the basis of the amount of

Na in the infusateΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)

ΔSNa is a change in SNa]Na + K[inf is infusate Na and K concentration in 1

liter of solution

OH MY GOD, what did he just say!!!!!!!!!!!!!!!!!!

IV Fluids›One liter of Lactated Ringer's Solution

contains:130 mEq of sodium ion = 130 mmol/L109 mEq of chloride ion = 109 mmol/L 28 mEq of lactate = 28 mmol/L4 mEq of potassium ion = 4 mmol/L 3 mEq of calcium ion = 1.5 mmol/L

›One liter of Normal Saline contains:154 mEq/L of Na+ and Cl−

›One liter of 3% saline contains:514 mEq/L of Na+ and Cl−

Example:›a 60 kg women with a plasma sodium of

110 meq/L›Formula:

ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)›What is the TBW?›How high will 1 liter of normal saline raise

the plasma sodium ?Answer:

›TBW is 30 L›Serum sodium will increase by

approximately 1.4 meq/L for a total SNa of 111.4 meq/L

Example:›a 90 kg man with a plasma sodium of 110

meq/L›Formula:

ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)

›What is the TBW?›How high will 1 liter of 3% saline raise the

plasma sodium ?Answer:

›TBW is 54 L›Serum sodium will increase by

approximately 7.3 meq/L for a total SNa of 117.3 meq/L

Asymptomatic or Chronic›SIADH

response to isotonic saline is different in the SIADH

In hypovolemia both the sodium and water are retained

sodium handling is intact in SIADHadministered sodium will be excreted in the

urine, while some of the water may be retained

possible worsening the hyponatremia

Asymptomatic or Chronic›SIADH

Water restriction0.5-1 liter/day

Salt tabletsDemeclocycline

Inhibits the effects of ADHOnset of action may require up to one week

Example:–85 y/o male with weakness and head ache–SNa is 118 mEq/L–Plasma osmolality is 254 mosmol/kg–Urine osmolality is 130 mosmol/kg–Urine sodium >20 mEq/L–Uric acid is 3mg/dl

•What type of hyponatremia does this patient have?

•What additional labs/studies would you want?

Example Cont:.›Noncontrast CT

Head:Tx

›Call Neurology and neurosurgery

›Free water restriction

Ouch!!!!!

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•Example:–63 y/o female at 75 Kg with N/V/D for 4 days–SNa is 108 mEq/L–She has had one seizure in the ambulance

•Plasma osmolality is 251 mosmol/kg•Urine osmolality is 47 mosmol/kg•Uric acid is 6mg/dl

•What type of hyponatremia does this patient have?

•What additional labs/studies would you want?

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How will you Tx her?›Calculate the total body water

0.5 x weight = 37.5 L

›What rate of correction do you want?8 to 10 mEq/L in 6 to 8 hours

›What fluid will you use?3% Saline

›How will you calculate the amount of sodium to give her?

ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)

›How will her sodium increase after 1 liter of 3% saline?

By 10.8 mEq/L to 118.8 mEq/L

What other medication will she need?›Lasix and a foley

Her sodium increases to 118.8 mEq/L over the next 8-10 hours. How will you

continue to correct her hyponatremia?› ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)›ΔSNa = 154mEq/L – 118.8mEq/L ÷ 38.5L =

0.9 mEq/LSo 2 liters of normal saline over the next

14 hours

The syndrome of inappropriate antidiuretic hormone secretion or SIADH  (other names: Schwartz-Bartter syndrome, SIAD—syndrome of immoderate antidiuresis) is characterized by excessive release of antidiuretic hormone from the posterior pituitary gland or another source. The result is often dilutional  hyponatremia in which Athe sodium remains normal but total body fluid increases. It was originally described in people with small-cell carcinoma of the lung, but it can be caused by a number of underlying medical conditions. The treatment may consist of fluid intake restriction, various medicines, And management of the underlying cause.

Gastro-intestinal Anorexia Nausea

Skeleto-muscular Muscle achesGeneralised muscle weakness

Neuro-muscularMyoclonusHyporeflexiaAtaxiaPathological reflexesTremorAsterixiRespiratoryCheyne-Stokes respirationNeurologicaDysarthriaLethargyConfusionDeliriumSeizuresComa (from cerebral oedema)

Some common causes of SIADH include:[citation needed]MeningitisHead injury

Subarachnoid hemorrhageCancers

Lung cancer (especially small-cell lung cancer, as well as other small-cell malignancies of other organs)

Infections Brain abscess Pneumonia Lung abscess

Guillain-Barré syndromeDrugs

Chlorpropamide Ciprofloxacin[2] Clofibrate Moxifloxacin[2]

Phenothiazine

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