disorders of electrolyte balance
TRANSCRIPT
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
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• 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.
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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
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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
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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
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Treatment of Hyponatremia
• Treat the underlying cause
• Administered sodium should be closely monitored
• Fluid restriction and diuretics – edematous state
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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
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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
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• 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
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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.
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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
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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
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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
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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
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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.
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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
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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
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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
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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.
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• 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
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• 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
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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
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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
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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
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Plasma Expanders
• Stay in vascular space and increase osmotic pressure
• Colloids (protein solutions)
– Packed RBCs
– Albumin
– Plasma
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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