SODIUM

Dr Nick Taylor Visiting Emergency SpecialistTeaching Hospital Karapitiya

Senior Specialist and Director ED TrainingClinical Lecturer, Australian National UniversityCanberra Hospital, Australia

GOALS

•Learn to diagnose Hypo and Hypernatraemia•Learn to safely manage these acutely

•SODIUM LEVELS MEASURE WATER STATUS NOT SODIUM STATUS

Sodium

• Sodium is the major positively charged cationin ECF. • Determines ECF volume.• Major intravascular ion to affect osmolality

(2Na+ + Glucose + urea)• An acute increase or decrease in serum sodium

will produce an increase or decrease in serum osmolality.

Amounts

• Total body sodium = 60mmol/kg (4000mmol in adult male) – Plasma level around 140mmol/L• ECF: 50% (140mmol/L)• ICF: 5% (15mmol/L)• Bone: 45% (125mmol/L)• 70% is exchangeable (90% for K)• Strong inward gradient to cells (opposite to K)

and Equilibrium potential +60mV

HOMEOSTASIS

•Sodium homeostasis is maintained by thirst, ADH aldosterone and the kidneys

Reabsorption

• Na is reabsorbed in the kidney (Excrete only 0.6%), • 70% proximal tubule• 20% ascending loop• 5% distal tubule• 3% collecting duct

OSMOLARITY REGULATION: ADH

•ADH secreted by hypothalamus in response to raised osmolarity•Causes water retention in kidney and thirst• Increased water in circulation causes decrease in osmolarity

VOLUME REGULATION: RAS

• When intravascular volume falls, the renin-angiotensin system is stimulated and aldosterone is released from the adrenal gland

• Results in increased reabsorption of sodium in exchange for increased excretion of potassium and hydrogen.

• The increased sodium reabsorption will cause more water to also be reabsorbed by the kidney.

• If too much circulating volume is sensed by the atria, natriuretic peptides are released, resulting in a diuresis

HYPERNATRAEMIA

HYPERNATRAEMIA (>145)

• Usually in an unwell patient• Almost always associated with TBW deficit• Usually patients have impaired thirst mechanism or no water access• Thus: elderly, very young, coma, ventilated, psychiatric at highest risk

CAUSES

•It’s all about VOLUME STATUS

3 GROUPS of Hypernatraemia

• Hypovolemic hypernatremia: decreased total body sodium and decreased TBW • Euvolemic hypernatremia: normal total body sodium and decreased TBW • Hypervolemic hypernatremia: increased total body sodium and increased TBW

Hypovolaemic: decreased total body sodium and decreased TBW

• LOSS of Water>Salt• Heat illness • Increased insensible losses: burns, sweating • Gastrointestinal loss: diarrhea, protracted

vomiting, continuous gastrointestinal suction, fistula • Osmotic diuresis: glucose (HHNK), mannitol,

enteral feeding

Euvolaemic: normal total body sodium and decreased TBW

• LOSS of WATER• Diabetes insipidus • Neurogenic • Elderly with “reset” osmostat• Hypothalamic dysfunction • Suprasellar or infrasellar tumors • Renal disease • Drugs (amphotericin, phenytoin, lithium,

aminoglycosides, methoxyflurane)• Sickle cell disease

Diabetes Insipidus

• Central• Familial• Brain disease: trauma, tumour, HIE, infiltrative, infection• Anorexia

• Nephrogenic• CKD• PCKD• Lithium toxicity• Sickle cell• Hyper Ca, hypoK

Hypervolaemic hypernatremia: increased total body sodium and increased TBW

• EXCESS SALT• Salt tablet ingestion • Salt water ingestion • Saline infusions • Saline enemas • Intravenous sodium bicarbonate • Poorly diluted interval feedings

• Primary hyperaldosteronism (Conn’s)• Hemodialysis • Cushing syndrome

Sodium Level

• Levels of 150 to 170 mmol/L (150 to 170 mEq/L) usually indicate volume depletion • >170 mmol/L (170 mEq/L) is usually associated with diabetes insipidus • >190 mmol/L (190 mEq/L) is usually a result of exogenous sodium gain

Symptoms

• Irritability, nausea, weakness, abdominal pain, lethargy, and tachypnea. • Patients or caregivers may have noted polyuria or

polydipsia, or patients may have obvious signs of extrarenal fluid losses. Other patients may be asymptomatic• The degree of dehydration may be underestimated

because intravascular volume is maintained. • In severe cases of hypernatremia, coma,

convulsions, pulmonary edema, and shock due to severe intracellular fluid loss can develop rapidly.

Evaluation

•Urine osm and Na+•Calculate TBW deficit•TBW deficit = TBW x [(serum Na/140) - 1] •TBW is generally 0.6 x body wtbut use table

Evaluation:TBW deficit

Urine osm

• Normal kidney response to hypernatraemia is to excrete minimal aurine that is maximally concentrated (urine osmolality >800 mmol/kg • Hypertonic urine is usually seen with extra-renal

fluid losses, eg vomiting, diarrhoea, burns, and excessive sweating. • Isotonic urine can be seen with diuretic use,

osmotic diuresis, and salt wasting. • Hypotonic (<300 mOSm/kg) urine associated with

polyuria is seen with diabetes insipidus

Urine Sodium

• If <20 causes is usually hypovolaemic with Gi or other losses• If >20 could be hypovolaemcwith renal losses or hypervolaemic

Management: 3 goals

•Quickly correct underlying shock, hypoperfusion, or significant hypovolemia with normal saline;

• Treat the underlying cause of hypernatremia (such as fever, vomiting, diarrhea, or diabetes insipidus)

• Carefully lower the serum sodium, usually by replacing the body’s total water deficit.

Formula: Medcalc

Fever increases insensible water losses by 10% per degree Celsius above 38°, or 100-150 cc/day increase per degree Celsius above 37°.

Volume resuscitation

• Until hypovolaemia is corrected, homeostatic mechanisms will promote sodium retention• N/S is appropriate until euvolaemia, then change to N/2• Correct at 1-2mEq/L /hr if acute rise

For non hypovolaemic

• If chronic elevation no more than 10-12mEq/L/24 hours (18mEq/L/48hrs)• For central DI; desmopressin (DDAVP)• For renal DI: low Na diet, Rx cause• For fluid-overloaded patients water

administration or its equivalent, D5W, in conjunction with frusemide. This combination achieves negative sodium balance with neutral or negative fluid balance.

HYPONATRAEMIA

HYPONATRAEMIA <135

• Commonly asymptomatic• Can present with headache, vomiting ,

lethargy or seizures, confusion, coma• Most likely causes:

• Therapy with thiazide diuretics • SIADH • Polydipsia in psychiatric patients • Unintentional water intoxication • Patients recovering postoperatively

Classification

•Pseudo and hypertonic•Hypovolaemic•Hypervolaemic•Euvolaemic

Pseudo and hypertonic hyponatraemia

•Hyperglycaemia (hypertonic) (Na+ lower by 2.4/100 >100)•Hyperlipidaemia•Hyperproteinaemia (myeloma)•Collection error

Hypovolaemic (low TBW and Na with Na loss>TBW loss)

• Body fluid loss (diarrhoea, sweat, NGT)• Third spacing (burns, bowel obstruction)• Renal• Diuretics• Addisons• RTA• Osmotic diuresis

Hypervolaemic (TBW gain > salt gain)

•Heart Failure•Cirrhosis•Chronic renal failure

Euvolaemic (TBW gain with near normal TB sodium)

•SIADH• Drugs• Psychogenic polydipsia• Beer potomania• Hypothyroidism• MDMA• Addisons

SIADH

• Inappropriately concentrated urine with hypo-osmolar state

ASSESSMENT

•It’s all about VOLUME STATUS

Using Urinary Sodium for diagnosis: Hypovolaemic

• Renal causes have elevated urine sodium levels > 20 mEq/L, as their kidneys cannot retain sodium or chloride. • Nonrenal causes have a low urinary sodium or chloride (< 20 mEq/L) Thus, these patients are appropriately retaining sodium due to their hyponatremia.

Hypervolaemia

• Congestive heart failure or cirrhosis have urine sodium levels < 20 mEq/L due to renal hypoperfusion• Those with renal causes have sodium levels > 20 mEq/L, as their kidneys are not retaining sodium

Euvolaemic

• Patients with euvolemic hyponatremia typically have a urinary sodium concentration > 20 mEq/L secondary to volume expansion caused by water retention.• Then use urine osm• Urine osm > serum osm = SIADH• Urine Osm < serum osm = other causes

Management

•Rate of correction depends on severity and acuity of symptoms as well as cause

Hypo Na Mx

• Most are stable and don’t need treatment acutely• Trial water restriction 800-1250mL/24hrs

•2 Groups need emergency Rx• 1. Symptomatic Na+ <120• 2. Asymptomatic <110

What to use

• 3% saline• 100mL results in increase of 2mmol/L• So start at 100mL/hr (1-2ml/kg/hr) or bolus 100mL if fitting• K+ must also be replaced

What rate of correction

• Still controversial•Worried about osmotic demyelination vs brain damage from persistent hypoNa• 8-10mmol/L/24 hrs or 18/48hrs has not been associated with osmotic demyelination• If severe/symptomatic raise by 1-2mmol/L /hr but stay within above limits

Osmotic demyelination

• Most cases of osmotic demyelination syndrome occur in the alcoholic, malnourished, and elderly population, but can occur in healthy, young patients• Flaccid paralysis, dysarthria, dysphagia, and hypo

tension.• Stop all sodium-containing fluids and administer

D5W immediately to temporarily lower serum sodium levels. • Reversal of symptoms has been shown,

experimentally, in numerous animal studies and also in 3 human case reports.

Calculations

•

Hypovolaemic

•Use NS rapidly until volume status corrected•Then continue NS at a slower rate with correction limits in mind

Hypervolaemic

• Hypertonic saline can cause volume overload to worsen•Water restriction very important• Consider diuretics in CCF or albmin/diuretic in liver failure• Dialysis may be needed in CRF

Euvolaemic (SIADH)

•Mainstay of Rx is water restriction and treating cause• Demeclocycline has side effects• USFDA approved ADH receptor antagonists (vaptans) are newer treatment showing some promise

Exercise induced hypoNa

• Exercise duration > 4 hours, • Female gender, • Excessive drinking during the event, • Preexercise dehydration,• NSAIDs• Lack of heat acclimation

Exercise induced hypoNa

•Rx for encephalopathy is with 3% saline 100mL repeated if needed• If not very symptomatic, water restrict

MCQ 1

• A 38-year-old man who is hiking the Kokoda trail feels unwell and is confused, but not hypotensive; His weight is 4.5 kg higher than at the start of the trek. Electrolyte measurements when retrieved included a serum sodium concentration of 118 mEq/L. The most likely proximate reason for the hyponatremia is:

• a Cerebral salt wasting• b NaCl-wasting nephropathy• c. Excessive intake of hypotonic fluid• d Increased secretion of ANP• e Excessive sweating

MCQ 2

A 42-year-old marathon runner collapsed at the finish She was confused and knew only her name. Blood pressure was 90/60 mmHg and pulse was 130 beats/minute; No pre-marathon weight was available. Serum sodium concentration was 163 mEq/L. The most likely underlying cause of the hypernatremia is:

• a. Loss of hypotonic fluid across skin • b. Lithium use • c. Hereditary nephrogenic diabetes insipidus • d. Pregnancy with increased placental vasopresinase

activity • e. DDAVP

MCQ 3

• A 40-year-old man with a yet undiagnosed systemic disease, including pulmonary lesions, presents with increasing thirst, polydipsia, polyuria, and a serum sodium concentrate of 152 mEq/L. Simultaneous urine osmolality was 100 mosm/kg. He takes no medication. The most likely systemic disease responsible for the hypernatremia is:

• a. Diabetes mellitus • b. Neurosarcoidosis• c. Adrenal insufficiency • d. Primary aldosteronism• e. Hereditary nephrogenic diabetes insipidus

MCQ 4

• A 60-year-old man with known lung cancer is seen in follow-up with no major symptomatic changes. His BP is 150/90 mmHg, pulse 86 and regular and he has no edema. Electrolytes reveal a serum sodium concentration of 125 mEq/L; and the urine osmolality is 280 mosm/kg. The most likely explanation for the hyponatremia is:

• a Cerebral salt wasting• b Diuretic use/abuse• c. SIADH• d Adrenal insufficiency• e Psychogenic polydipsia

MCQ 5

• The most appropriate therapy for that patient is:• a. Solute-free water restriction• b DDAVP• c. Cortisone• d. Thyroxine• e. 5% hypertonic saline

MCQ 6

• A 38 F is seen by Psychiatry. A diagnosis of bipolar disease is made and medication is prescribed. Four months later, she returns and states that she now is thirsty and is voiding frequently Serum sodium concentration is 150 mEq/L and Urea is 22 mg/dl. The most likely agent/process responsible for the polyuria is:

• a. Hypercalcemia• b. Lithium • c. Demeclocycline• d. Sickle cell disease • e. Prolonged low protein diet

MCQ 7

• A 28-year-old woman is brought to the ETU by friends after collapsing at an all-night dance event. Serum sodium concentration is 118 mEq/L. The most likely cause of the hyponatremia is:

• a DDAVP• b Addison's disease• c Beer potomania• d. MDMA (“Ecstasy”)• e Pseudo hyponatremia

MCQ 8

• A 76-year-old man is sent to the hospital from his nursing home because of obtundation, decreased skin turgor and fever. The serum sodium concentration is 168 mEq/L (it was 142 mEq/L four months earlier). The most likely cause of the hypernatremia is:

• a. Primary hypodipsia• b. Prolonged low protein diet • c. Hypercalcemia• d. Inadequate solute-free water replacement for

cutaneous pure water loss • e. Lithium

MCQ 9

• The treatment goal for this patient is: • a. Reduce serum sodium concentration to normal

in first 12 hours • b. Reduce serum sodium concentration to

normal in 24 hours • c. Reduce serum sodium concentration to 150

mEq/L in 24 hours • d. Maintain serum sodium concentration at 165

mEq/L for first 8 hours • e. Reduce serum sodium concentration by 10

mEq/L in 24 hours

THANKYOU

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