disorders of electrolyte balance

1-5gm/day

2-5gm

Dr. N. Sivaranjani 1

SODIUM METABOLISM

INTAKE

BODY DISTRIBUTION

LOSES100 -300 mmoles/DAY

Bones and tissues

25%

Exchangeable

75%

ECF

ICF

Interstitial fluid

Renal = IntakeRenal = Intake

Faeces

5mmoles/day

Sweat

5mmoles/day

Normal level of Na+ in plasma is 136-145 mEq/Land in cells 12 mEq/L.

Sodium is the major cation of extracellular fluid


• Functions of sodium

• Maintenance of resting membrane potential

• Nerve impulse transmission

• Muscle contraction

• Maintenance of EC osmotic pressure and Water balance

• Regulation of A-B balance

• Glucose , galactose, amino acid absorption

• Functioning of NaK ATPase and Na-H exchanger.


Regulation of sodium balance

• Kidney plays a predominant role.

• Renin/angiotensin – Aldosterone mechanism

effective circulating volume is the major stimulus

• Atrial Natriuretic peptide

increase in ECF, increase BP - stimulus


Disorders of sodium balance

• Hyponatremia

• Abnormally low serum sodium <136 mEq/L

• Decrease in plasma osmolality

Clinical features : Hyponatremia –due to excess H2O & Na :-

Edema , ascites , increased JVP

Hponatremia - due to loss of Na & H2O :-

Decreased skin turgor , dry mucus membrane, hypotension and tachycardia.Dr. N. Sivaranjani 5

HYPONATREMIA

Hypervolemia Excess of H2O & Na retention Presents with Edema

PSEUDOHYPONATREMIA

RENAL lossSALT LOSING NEPHROPATHY

ADDISONS DISEASE

DiarrheaVomitingBurns

SIADHCCF

NEPHROTIC SYNDROME

CIRRHOSIS

HYPERLIPIDEMIA

HYPERPROTEINEMIA

HyponatremiaN or raised P.Osmolalityplasma water fractionfalls

TRUE HYPONATREMIA

ATN

EuvolemiaExcess of H2O NO Edema

Increased intake of water –PSYCHOGENIC POLYDIPSIAIATROGENIC FLUID OVERLOAD

HypovolemiaH2O & Na loss Dehydration

NON RENAL loss


Diagnostic approach

• Plasma Na – decreased

• Plasma osmolality – decreased

• If pt Dehydrated – due to loss of Na and H2O

• Not dehydrated – due to excess Na and H2O

• Urine Na –

• Renal loss more than 20 mEq/L

• Non renal loss less than 10 mEq/L


8

Treatment of Hyponatremia

• Treat the underlying cause

• Administered sodium should be closely monitored

• Fluid restriction and diuretics – edematous state

Dr. N. Sivaranjani

9

Hypernatremia

– Plasma Na+ > 145 mEq / L

– Total body Na Content is high with respect to water

– Common cause – excessive water loss - Cells dehydrate

C/F :-If Hypernatraemia is due to water loss-

symptoms of Dehydration

Intense thirst, mental confusion, fever & decreased urine output

Due to excess salt gain- Hypertension ,Edema

Dr. N. Sivaranjani

CAUSES OF HYPERNATREMIA

Water depletionRetention of sodium

GIT loss

S.Vomiting S.Diarrhea

Excessive sweating

Ch.Fever S.ExerciseDIHypothalamic

Nephrogenic

Ingestion

Infusion of Na HCO3

for treatment of acidosis

1 ̊ Hyperaldosteronism

Conn’s syndromeCushing’s syndrome

Na & H2O depletion

Decreased intake Increased loss

Unconscious patient

Diuretic therapy , nephropathy ,polyuric phase of ATN , DM


• Diagnostic approach • Serum sodium and osmolality – elevated

HYPERNATREMIA

Urine osmolality

>300 mOsmo/Kg

Diarrhea – 700 mOsmol/KgExcessive sweatingDM – Osmotic diuresis

< 300 mOsmo/Kg

Diabetes insipidusADH stimulation

No response Nephrogenic DI

Response Central DI


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Treatment of Hypernatremia

• Treat the underlying cause

• Correct the free water deficit at a rate of 1mEq/L/hr

• Check serum Na every 4hr

• Use isotonic salt -free IV fluid

• acute hypernatremia - correction can be quicker.

• chronic cases should be treated slowly to prevent cerebral edema

Dr. N. Sivaranjani

POTASSIUM METABOLISM

INTAKE

BODY DISTRIBUTION

LOSES30 -100 mmoles/DAY

ECF

55 MMOLES/L

ICF

3600 MMOL/L

Renal

20-100 MMOL/L

Faeces

5mmoles/day

LOSS

Normal level of K+ in plasma is 3.5-5 mEq/Land in cells 150 mEq/L.


Functions of potassium

• Nerve impulse transmission

• Maintenance of IC osmotic pressure

• Function of H-K ATPase and HCL secretion

• Activation of intracellular enzyme- PK, GS

• Cardiac muscle activities

• Neuromuscular excitability


Uptake of K into cells - Na K ATPase / pump

Renal regulation K balance – 67% reabsorbed by PCT H+-K ATPase

Aldosterone – increase excretion of K+ from DCT

High K diet, H+ – increases the excretion of K.

Regulation of plasma Potassium

Increase uptake of K into cell Decrease uptake of K

Insulin DM

Alkalosis Acidosis – H+

Beta adrenergic stimulation Alpha Adrenergic stimulation

Inhibition of Na K ATPase


K

KH+

H+


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Hypokalemia

• Serum K+ < 3.5 mEq /L

• Beware if diabetic

– Insulin pushes K+ into cells

– D.Ketoacidosis – H+ replaces K+, which is lost in urine

Dr. N. Sivaranjani

HYPOKALEMIA

Intake Altered cellular uptake

GI loss Renal loss

Alkalosis

Insulin

Renal Tubular acidosis

Hyper Aldosteronism –Cushing’s disease

Dietary deficiency

Diuretics

Vomiting Diarrhea GI fistula

Hypokalemic periodic paralysis(abnormal calcium channels)


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Clinical manifestations of Hypokalemia

Non specific symptoms - Anorexia, Nausea, Vomiting ,Muscle cramps, confusion.

• Neuromuscular disorders– Weakness, decreased reflexes.– ECG - appearance of U wave , Flat or inverted T wave, ST

segment depression. Arrhythmias and cardiac arrest

Rx- supplement K+ slowly, preferably by foodsBe cautious in administering drugs that are not potassium-sparingMonitor acid-base balance, pulse, BP and ECG

Dr. N. Sivaranjani

Diagnostic approach

Hypokalemia

True hypokalemia Redistribution Insulin therapy

Urine K excretion - More than 25 mEq/dayRenal Loss

less than 25 mEq/dayNon Renal Loss Diarrhea

Plasma bicarbonate

Decreased – seen in metabolic acidosis Proximal RTA

Increased – Met Alkalosis Cushing’s syndrome


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Hyperkalemia

• Serum K+ > 5.5 mEq /L

• Beware of diabetic

– Insulin deficiency pushes K+ outside cells.

Dr. N. Sivaranjani

HYPERKALEMIA

Intake Pseudo hyperkalemia

Altered Cellular Uptake

Renal Excretion

Acidosis

Insulin deficiency

Renal failure

Hypo Aldosteronism –Addison’s disease

HemolysisK rich food –banana ,orange Leukocytosis

Thrombocytosis

Factitious (K+ leaches out when blood is kept for a long time before separation


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Clinical manifestations of hyperkalemia

• Early – hyperactive muscles , paresthesia

• Late - muscle weakness, flaccid paralysis

ECG – wide QRS complex, Peaked T-waves, Prologed PR interval.

• Dysrhythmias

– Bradycardia, heart block, cardiac arrest

Dr. N. Sivaranjani

ECG Changes


Diagnostic approach

Hyperkalemia

Exclude psuedohyperkalemiaand Redistribution

Plasma bicarbonate

High Anion GapDKA, LA

Normal Anion GapRTA RFMineralocorticoid deficiency

Increased Respiratory acidosis

Decreased

Anion Gap

NormalPeriodic paralysis


Treatment

Acute treatment –

• Infusion of Ca. gluconate – antagonize K

• Insulin and glucose administration – enhance entry of K into cell from plasma

• Administration of HCO3 – correct acidosis

Chronic treatment –

• Administration of K binding resins orally

• Dialysis – hemodialysis and peritoneal dialysis.Dr. N. Sivaranjani 26

Cl ˉ (Chloride)

• Major extracellular anion

• Plasma conc. 95 -105 mEq/ L

Regulation in kidney through:

• Reabsorption with sodium

• Reciprocal relationship with bicarbonate


Functions of chloride

• Regulation of A-B balance, Water balance and osmotic pressure

• Formation of HCl

• Chloride shift

• Enzyme salivary amylase is activated by Cl.


• Most commonly from gastric losses

– Excessive vomiting - compensatory increase in plasma bicarbonate. This is called hypochloremic alkalosis

– Excessive sweating.

• Renal loss

- Addisons disease, salt losing nephropathy .

• Often presents as a contraction alkalosis with paradoxical aciduria (Na+ retained and H+ wasted in the kidney)

Rx: resuscitation with normal saline

Hypochloremia


• Dehydrtaion ,

• Cushing’s synd,

• Severe diarrhea - loss of bicarbonate and compensatory retention of chloride.

• Renal tubular acidosis.

• often presents as a hyperchloremic acidemia with paradoxical alkaluria (H+ retained and Na+ wasted in the kidney)

Rx: stop normal saline and replace with hypotonic crystalloid

Hyperchloremia


IV FLUID REPLACEMENT THERAPY

Indications

Replacement of abnormal fluid & electrolyte losses [surgery, trauma, burns, GI bleeding]

Maintenance of daily fluid & electrolyte needs

Correction of fluid disorders

Correction of electrolyte disorders


Assessment of fluid compartment

Plasma volume –• BP, JVP, Pulse rate, CVP central venous

pressure

Interstitial volume –• Edema

Intracellular volume –• Difficult to assess clinically• Disorders of cerebral function is

important


What fluids to give :

5% dextrose – replace deficit in total body water

0.9% sodium chloride – expands only ECF volume

Hypotonic - Water moves from ECF to ICF by osmosisUsually maintenance fluids

0.45% sodium chloride 0.33% sodium chloride

Hypertonic – expands and rise osmolality of ECF 3% NaCl


Plasma Expanders

• Stay in vascular space and increase osmotic pressure

• Colloids (protein solutions)

– Packed RBCs

– Albumin

– Plasma


Essay (15)What are the functions of Na in the body? What is the reference range for levels of serum Na. describe working of RAA system o maintain optimal amounts of sodium in the body. Briefly disorders associated with derangements in Na homeostasis.

Short notes (5)Water toxicity Dehydration Give an account of water distribution and its balance in the body Explain the metabolic inter relation b/w Na conc and water volume. Hyponatremia

Very short notes (2)Normal Na and K levelName the major intra and extra cellular anionOsmolality Dr. N. Sivaranjani 35

disorders of electrolyte balance

Education