Hyponatremia Management

Dr. Fateh AkramDTCD STUDENTMedicine Unit VI

National Institute of Diseases of The Chest & Hospital

Sodium Water

Hyponatremia

“Hyper-acquemia”

Normal water balanceNormal water intake(1-1.5 L/d)

Intracellular ExtracellularCompartment compartment28 L 14 L

42 L TBW60% of body weight

Fixed water excretionStool Sweat Lungs0.1 L/d 0.1 L/d 0.3 L/d

Total insensible losses0.5 L/d

WaterOfCellularMetabol0.3-0.5 L/d

Variable water excretion

Kidney

Total urine output1-1.5 L/d

Waterintake

Waterexcretion

ADH

Hyponatremia

Mechanism of

Hyponatremia

Hyponatremia Supervenes when

free water intake >> free water excretion

Main defense excretion of free water by kidneys

Identifying types of

Hyponatremia

Hypotonic Hyponatremia

Hypotonic HyponatremiaHypovolemic Euvolemic Hypervolemic

Urine Na

<30 >30ExtraRenal Renal

1.Diarrhea2.Vomiting3.Hemorrhage4.Sweating

1.Diuretics2.Mineralocorticoid def3.Salt losing Nephropathies4.Cerebral salt wasting

1.SIADH 2.Glucocorticoid def3.Hypothyroidism4.Poor solute intake -Tea Toast syndrome - Beer potomania5.Post op / Hospital acquired

1.CHF2.Cirrhosis3.Nephrotic synd4.Advanced CRF

Hypotonic hyponatremia(Vol status indeterminate)

Urine Na <30 : Respond to 0.9 NS Volume depleted

Urine Na > 30 : No response to 0.9 NS Likely to have SIADH

Euvolemic Hypotonic Hyponatremia

SIADH

Criteria for diagnosis:

P osm <275 mOsm/kg U osm >100 mOsm/kg Clinical euvolemia Urine Na > 30mmol/L while on normal salt intake Normal thyroid, adrenal and renal functions Inappropriately elevated AVP levels in 85-90%

Tumors small cell CA, Head & NeckCNS Trauma, tumors, meningitis, CVAPulmonary Pneumonia, PTB, resp failure, asthma

Mechanical ventilation, COPDDrugs DDAVP, Diabinese, NSAIDS, opiates,

Carbamazepine, SSRI, Tricyclic, ThiazidesEcstasy, ACE-I, Omeprazole

Miscellaneous Pain, Nausea, surgery, stress, Alcohol withdrawal

SIADH : Common Causes

SIADH : Treatment

Discontinue offending agent Treatment of etiology (infection, pain) Fluid restriction (for Chronic asymptomatic

Hyponatremia)

Euvolemic Hypotonic hyponatremiaPoor solute Intake

Beer Potomania, Tea Toast syndrome

Urine Volume =

Normal Urinary Electrolytes Normal Urinary Urea

Na+ , K+ = 150 + 50 = 200 Catabolism= 75-100

Accompanying anions= 200 Diet ~50 mM/10 gm of dietary protein

Total 400 mM/day Total 400-500 mM/day

Urinary solute excretionUrinary Osmolality

Clinical setting of low solute intake: - Alcoholism (Beer Potomania) - Anorexia (Tea and Toast Diet)

Urinary solute excretion in person on normal diet-800-900 mM/day

Euvolemic Hypotonic hyponatremiaPoor solute Intake

Treatment

1. Increase solute intake –• High protein diet• Salt tablets or high dietary

salt• Urea

2. Fluid restriction

Hospital acquired HyponatremiaVirtually every hospitalized patient has

potential stimulus for AVP excess Administration of hypotonic fluid with

excess AVP are at risk for Hyponatremia

Chung HM et al, Arch Inter Med 2002

Hospital acquired hyponatremia• Ringer’s Lactate (Sodium 77) is hypotonic

and can produce hyponatremia• No justification for Ringers lactate in post op

period• Administration of 0.9 saline is safe• No reports of 0.9 Saline causing neurological

complications of hyponatremiaSteele A et al, Ann Intern Med 1997Moritz ML et al, J Am Soc Nephrol 2005

Clinical featuresAnd

Brain Adaption

Hyponatremia Symptoms

Cerebral adaption to decrease cerebral edema

Early 1-3 hrsCSF distribution

Later (> 3 hrs)Loss of Osmolytes and electrolytes:

Glutamate, Inositol, Taurine, Urea, K, Na, Creatinine

InvestigationHistory & volume statusSerum OsmolalityUrine Osmolality/sp grUrine NaS Cr/urea/KT3/T4/TSHCXRCT Scan Manisha Sahay

Treatment

Extensive data suggest that the serum sodium should be raised by no more than 10 mEq/L over 24 hours. Correction by 6 mEq/L in 24 hours has been dubbed the "rule of sixes."The rule of sixes is as follows: "Six-a-day makes sense for safety. Six in 6 hours for severe symptoms and stop."

Acute Hyponatremia: Less than 48 hrs Neurologic symptoms due to brain edema Rapid correction well tolerated

Chronic Hyponatremia:More than 48 hrs or unknown time Mild brain edema (<10%) Sensitive to Na correction rate Aim to increase Na by 10% (not more than 12 in 24 hrs)

How long has hyponatremia been present?

Does the patient have symptoms?

Does the patient have risk factors for development of neurologic complications?

Monitoring of patients Volume status Daily weight Frequent Serum Na, K Plasma Osmolality Urine Na, K, osmolality Strict Input and Output

Basic concept Free water intake << Free water output

ANDNa, K intake >> Na, K output Needed Info:

Serum Na , osmolality Urine Na, K, Osmolality Strict Input/ Output

Rate of correction

Hyponatremia

Chronic

Asymptomatic

Symptomatic

Long term managementTreat etiologyWater restrictionDemeclocyclineUreaV2 receptor antagonist

Some immediate correctionHypertonic saline + FurosemideChange to water restrictionFrequent serum & urine electrolytesDo not exceed 12 meq/l/d

Emergency Hypertonic saline+ furosemide

Acute <48 hrs Chronic>48 hrs

No immediateCorrection needed

Thurman et al,Therapy in nephrology and Hypertension,Saunders 2003

Treatment of Symptomatic Hyponatremia

Treatment based on neurological symptoms and not on Sodium

Needs aggressive management with 3%NaCl

No role of fluid restriction alone Treatment should precede any

neuroimaging Treatment in monitored setting Sodium levels measured every 2 hours

Impending herniation: Sz, resp arrest,, obtundation, Decorticate posturing, dilated pupils:

100 ml of 3% NaCl as a bolus over 10 min to rapidly

reverse brain edema. Repeat bolus as required till symptoms improve

Encephalopathy: Headache, N/V, Altered mental status:

3% NaCl @ 50-100 ml/hr Calculating 3% saline rate: Weight in kg x desired rate of increase in Serum Na

Monitor [Na] every 2-4 hrs Stop active correction when appropriate end point

is reached: Patient becomes asymptomatic Safe Na levels reached (generally 120) Total correction 12 mmol in 24 hrs or 18-20 mmol in 48 hrs Complete rest of correction with - fluid restriction

Attend to underlying cause No immediate correction needed Fluid restriction

Urine Na + K Plasma Na

Recommended water intake

>1 < 500 ml/day

-1 500 to 700 ml/day

< 1 < 1000 ml/day

D Ellison, T Berl. NEJM 2007;356:2064-72

Treatment Mechanism Dose Advantage Limitations Fluid restriction

Decreases availability of free water

Variable EffectiveInexpensive

Non compliance

Encourage dietary salt and protein

Solutes required for free water excretion

Variable

Demeclocycline ↓ ADH response 300-600 mg BID Effective Unrestricted water intake

Nephrotoxic, Polyuria, Photosensitive

V-2 Receptor antagonist -Conivaptan

Antagonize ADH receptor

20-40 mg/dayIV (Vaprisol)

Effective Available only as IV

Complications of treatment

Acute Cerebral edema Osmotic Demyelination

Take home messageHyponatremia –a common, life threatening problem

In presence of ADH concentrated urine is formed

Treatment – Basic concept: Free water Input << Free water Output Na+K Input >> Na+K Output

Step wise evaluation importantInappropriate treatment – Worse than disease• Practicing is the best way of learning!!!

HyponatremiaAsymptomaticSymptomatic

Long term management

Hypertonic saline

Acute <48 hrsNo immediateCorrection needed

Emergency

Go slow