Approach to Hyponatremia

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Approach to Hyponatremia : 

Approach to Hyponatremia Dr Vidyashankar .P MBBS,Dch,DNB,DM Asst prof in nephrology

Case scenario 1 : 

Case scenario 1 65 years old gentleman KH.Hypertensive on Amlodepine and hydrochlorthiazide was admitted with nausea and hiccoughs Vitals. Pulse 85,BP was 110/76 Clinical examination was unremarkable Lab: Urea 36mg/dl,Creat 0.9 mg/dl,Na 122mEq/L,K 2.8 mEq/L,LFT was normal.

How to manage ? : 

How to manage ? A. Give NS? B. Give 3% NS C. Advise increased oral salt intake? D. Stop diuretics and oral salt?

Approach : 

Approach Is hyponatremia -acute/Chronic Is symptomatic/Asymptomatic Further investigation needed? What is the cause ? Treatment Prevention

Definition (Arbitrary) : 

Definition (Arbitrary) Normal serum sodium varies between 135-145 mEq/L Serum sodium level < 135mEq/L Severe Hyponatremia is serum Sodium < 120 mEq/L Life threatening when is serum sodium < 110 mEq/L

Clinically what to look for? : 

Clinically what to look for? Sensorium Presence of hypovolumia Clinical signs of hypovolumia Pulse- Feeble, Tachycardia BP-(Postural fall, Most* fall of BP fall>10 mm) Decreased Skin turgor Low JVP Low CVP Hypervolumia Edema, Ascitis Increase JVP,CVP Pleural effusion and pulmonary congestion

Hypovolumia /dehydration : 

Hypovolumia /dehydration Can they be used synonymously ? Dehydration is loss of electrolyte free water -Hypovolumia due to pure water loss (Excessive sweating, Decreased water intake, DI) Hypovolumia or volume depletion refers to extracellular volume depletion as a result of salt and water (Bleeding, diarrhea, diuretics, third space loss)

Types of Hyponatremia : 

Types of Hyponatremia Hypovolumic Hyoponatremia(LowTotal body H20, Decreased total body Na ) -Hypovolumia(Most common) -Minerlocortoid deficiency -Diuretics Hypervolumic hyponatremia( Increased total body H20,Total body Na Normal/Increase ) But can have decrease ECV -Renal Failure -CHF -Nephrotic syndrome -Cirrhosis of liver -NSAIDs Euvolumic hyponatremia( Normal H20, Na ) Classically SIADH But occurs in any edematous conditions on diuretic

Symptoms : 

Symptoms Symptoms are related to the rate of fall of serum Na(>0.5mEq/L) Mild symptoms Lethargy, dizziness, Headache, Agitation(Raised ICT) Nausea, Vomiting and Hiccoughs Muscle cramps and twitching Severe symptoms Unconsciousness, Seizures(due to severe brain swelling)

Acute/Chronic : 

Acute/Chronic Acute hyponatremia is Change of serum sodium< 48 hrs Chronic hyponatremia is Change of serum sodium> 48 hrs Difficult to assess as outpatient Chronic hyponatremia are rarely symptomatic unless Serum Na <120 mEq/L

Further investigations : 

Further investigations The patient had Urinary Sodium of 54 mEq/L Serum osmolality of 256 mosmol Normal lipid and blood sugar Urine Qty 2.6 L Urine Osmolality of 580 mEq/L

Pseudohyponatremia : 

Pseudohyponatremia Hyperosmotic hyponatremia(Serum osmolality >290 mosm with Low Na) Low serum sodium due to high proteins and hyperlipidemia Redistributive hyponatremia is due to hyperglycemia and mannitol

Normal values : 

Normal values Normal serum osmolality varies (275-290 m osm/Kg) Rule of thumb(serum sodiumX2+10)+ 10 Low osmolality due Low sodium or Normal sodium with excess water Normal urine osmolality(100-1200 mOsm/Kg) High urine osmolality Less water loss (SIADH) More solute loss (Glucose, Sodium) Normal Urine Na <40mEq/L but varies on dietary salt intake

Urine osmolality and specific gravity : 

Urine osmolality and specific gravity

Urinary sodium : 

Urinary sodium Interpret Hyponatremia with urinary sodium Normal urinary sodium level(<40mEq/L) Urine Na<20 mEq/L Dehydration, Decreased effective circulating volume, Hypovolumia High urinary sodium(>40 mEq/L) Diuretics(Common) Tubulo interstitial disease(HTN, DM, Drug induced) Mineralocortoid deficiency Hypothyroidism

Urinary sodium in Hyponatremia : 

Urinary sodium in Hyponatremia Hypovolumic patients Renal losses of water and Na(Urinary Na>40mEq/L) Extrarenal losses(Urine Na<20mEq/L) Euvolumia Urine Na>40 -SIADH -Hypothyroidism -Pain/emotional stress -Reset osmostat in chronic illness -Diuretic use in CHF,Cirrhosis,Nephrotics Urine Na<10mEq/L -Psychogenic polydypsia -Acute water intoxication Hypervolumia Urinary Na <20 Cirrhosis,CHF,Nephrotic syndrome Urinary Na> 40 Renal Failure, Hypervolumia on diuretics

Cause of Hyponatremia : 

Cause of Hyponatremia pt is having Euvolumic,?Acute symptomatic hyponatremia Cause? Is it Diuretics induced

How to manage : 

How to manage No CNS symptoms Stop diuretics oral salt intake and hydration Supplement K 1 gm of table salt = 17 mEq/L 1 gm Na = 44 mEq/L

Correction of K itself corrects Na : 

Correction of K itself corrects Na Hypokalemia drive Na into the cell to maintain electroneutrality Exogenous K supplements directly enters cells and Na efflux Kcl(K+,Cl),Chloride enters RBC and drags water along thus raising serum Na Na is reabsorbed in the distal and collecting tubule for the exchange of K(Aldosterone dependent). Presence of Hypokalemia decrease Na reabsoption

How to calculate Na deficit : 

How to calculate Na deficit Na deficit=0.5XLean body Wt(Kg)X(desired Na-plasma Sodium) Eg=60 kg man with Na of 123 Na deficit=0.5X60X(135-123) =30X12 =360 mEq/L Assuming no urine loss Na Salt supplementation=360/17 21 gms in 48 hrs

Course in the ward : 

Course in the ward On Day 3 patient was symptamatically better Lab; Serum Na 142,K 4 He was discharged with advise to take salt of 5 gms

Diuretics and hyponatremia : 

Diuretics and hyponatremia

Diuretic induced hyponatremia : 

Diuretic induced hyponatremia Almost always caused by thiazides Acute symptomatic hyponatremia can be due to idiosyncratic reaction ,particularly who drink large volume of water. Hyponatremia is not caused by natriuresis, but due to K loss and ADH stimulation(Volume depletion) Loop diuretic inhibit Na-K-2Cl channel in the loop of henle Unabsorbed Na is available in the DCT for the exchange of K in the presence of aldosterone Thiazides block Na, K in the distal tubule

Key points in Hypovolumic hyponatremia : 

Key points in Hypovolumic hyponatremia Hypovolumia with no life threatening CNS symptoms -Restore ECF volume(NS bolus) -3 cc/kg/hr to replace ECF water and Na Dehydration+Hyponatremia+Hyperkalemia=> Adrenal insufficiency(Until proved otherwise)

Slide 25: 

After 2 weeks, he was admitted to ER with seizures and unconsciousness Vitals were normal. No edema CT brain was unremarkable Lab; Urea 8mg/dl, creat 0.8 mg/dl. Na 112,K3.2 Urine Na 52 mEq/L Serum Osmolality 233 mOsm/kg

What is the management : 

What is the management Ongoing seizures,anti epileptics with Hypertonic saline(5 mEq/10 ml) @ 25 ml/hr till seizures are controlled I.V 3% NS to bring up the serum Na to 120mEq/L Rule of thumb:0.5mL/Kg/Hr of 3% Nacl will increase serum sodium by 0.5 mEq/L Not to increase serum sodium by 8-10 mEq/day Safe level of serum Na is 120 mEq/L 30 ml/hr of Nacl for 16 hrs

Indications for hypertonic Nacl(3%) : 

Indications for hypertonic Nacl(3%) Acute symptomatic hyponatremia(Neurological),even if serum sodium is > 120 mEq/L Chronic asymptomatic hyponatremia if serum sodium < 110 mEq/L Acute symptomatic hyponatremia(Serum sodium < 120 mEq/L) even absence of CNS symptoms

Target serum sodium : 

Target serum sodium For I .V correction Acute symptomatic hyponatremia(Neurological)=120 mEq/L Chronic asymptomatic hyponatremia if serum sodium = 110 mEq/L Acute asymptomatic hyponatremia(Serum sodium = 120 mEq/L

Day 2 of admission : 

Day 2 of admission Pt was alert and oriented No further episodes of seizure Serum Na 122 mEq/L Urine osmolality was 450 mOsmal/L Serum Osmolality 248 mOsm/L

Problems? : 

Problems? Euvolumic Hyponatremia Acute CNS symptoms Recurrent hyponatremia No diuretics Any other tests needed

Further tests : 

Further tests Basal cortisol levels were Normal TSH 3.5 T3 and T4 levels were normal Diagnosis?


SIADH Diagnostic criteria Hyponatremia Euvolumic state Urine sodium>40 mEq/L Urine Osmolality >200 Normal renal, Thyroid and adrenal Functions Supportive: Low serum urea,Na correctable with water restriction

Few Causes of SIADH : 

Few Causes of SIADH Drugs Carbamazepine NSAID Barbiurates Clofibrate Thaizides Pulmonary disease CNS diseases Tumors

Evaluation : 

Evaluation PET scan-N Colonoscopy-N CT thorax-N PSA-45ng/dl Bx of prostate= Adeno Ca

Diagnosis and treatment : 

Diagnosis and treatment Ca prostate with acute symptomatic hyponatremia due to SIADH Restriction of water Normal salt and high protein diet(Clears water osmotically) Demeclocycline, Lithium( Antagonize ADH) Treatment of underlying disease

Key points in Euvolumic Hyponatremia : 

Key points in Euvolumic Hyponatremia Look for the underlying renal, Hepatic and cardiac condition Always look for BACK EDEMA in recumbent patients Patients with CHF, Cirrhosis and Nephrotic syndrome on diuretic may have euvolumia SIADH is a diagnosis of exclusion TSH and Basal cortisol to r/o SIADH

Case scenario 2 : 

Case scenario 2 25 year old marathon runner was bought to ER with confusional state He had completed 14 Km of marathon,with 10 L of water Clinical examination; No signs of dehydration ,vitals Normal. Lab: Urea 12,serum creat 0.8 Na 108,K 4.5 Urine Na 10 mEq/L

Treatment : 

Treatment A)Give NS B)Give 3% NS C) Give Frusemide and NS

Diagnosis : 

Diagnosis He had consumed Excess water Acute water intoxication He was given I.V 3% NS @ 30 ml/hr X 24 hrs On day 2 he sodium of 120 mEq/L and normal neurological state Serum sodium returned to normal in 3 days

What is dietary salt and water balance : 

What is dietary salt and water balance First every 500 ml of water intake-1 gms salt Next every 250 ml of water intake- 1gms Ex;person taking 1.5 litres of tap water should take -1g(500)+4(250X4)= 5gms salt Water consumption without salt=Water intoxiation Other causes of dilutional hypnatemia -Post TURP-Absorption of Gycine (Bladder irrigatation) -Beer potomania-Excess beer consumption(Beer contains 45% v/v of Glycine

Case senioro 3 : 

Case senioro 3 52 year old male MN,Alcoholic cirrhosis was admitted to the ICU with GI bleed. CVP was 16 cm He was conscious and oriented Chemistry:Urea 165 mg/dl.S.creat 0.9 Na 118,K 5.7.Urine spot Na 65 mEq/L Edema++,Ascitis +

Treatment : 

Treatment A)Give hypertonic NS B)Give NS and frusemide C)Restrict fluid and frusemide D)Frusemide

How to manage : 

How to manage Hypervolumic hyponatremia have Increased ECF and Normal or High total body Na(Secondary hyperaldosteronism,Low GFR,Increased ADH) I.V 3%Nacl or NS will cause fluid over load Initially use Frusemide to clear off free water One liter of free water cleared will bring up the sodium by 5mEq

Diagnosis : 

Diagnosis Hypervolumic hyponatremia Why his urine Na is high? -Decrease ECV and ADH secretion Glucocorticoid/thyroid deficiency

Stimulation of ADH : 

Stimulation of ADH Osmotic stimuli -Serum osmolality >275 -Decrease effective ciculating volume(Cirrhosis,Nephrotic syndrome) Non osmotic stimulation -Nausea, Pain,drugs(SIADH) ,Alcohol -Angiotensin II

Case study 4 : 

Case study 4 49 yr old man with small cell ca developes severe vomiting after chemotherapy On admission JVP below 5 cm,reduced skin turgor Lab;plasma Na 114 meq/L Plasma osm=243 mosm/kg Urine Na=6 meq/L Urine Osm=498 mosm/kg

Problems : 

Problems Hypovolumic hyponatremia Underlying SIADH due to Oat cell Ca?

Slide 48: 

Clinical and lab are consistent with dehydration and may be underlying SIADH The pt was initially treated with isotonic NS, Next day plasma Na was 122 mEq/L Urine sodium was 52 mEq/L Interpretation of Urine Na and Osmol

ABG and serum K in hyponatremia : 

ABG and serum K in hyponatremia Metabolic acidosis with Metabolic alkalosis

Key points : 

Key points Take meticulous history (Renal, cardiac,liver,drugs) Examination(Assess Volume status, CNS ) Chronic hyponatremia never have symptoms unless Na is less than 120 mEq/L Not to correct > 12 mEq/L in acute and >8 mEq/L in chronic hyponatremia Always interpret serum Na presence of symptoms Patients with severe CNS always due to acute hyponatremia Hyponatremia management always include urinary Na

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