This document discusses fluid and electrolyte imbalances. It covers water distribution in the body, the roles of major electrolytes like sodium, potassium, calcium, and their regulation. Causes, evaluation, and treatment approaches for various electrolyte abnormalities like hyponatremia, hypernatremia, hypokalemia, hyperkalemia, hypocalcemia, and hypercalcemia are summarized. Evaluation involves assessing symptoms, medical history, examination, and lab tests of serum and urine electrolytes and osmolality. Management depends on the specific imbalance and aim of correcting underlying causes and abnormal electrolyte levels.

1. Fluid & electrolyte imbalance
Sodium, Potassium, Calcium

2. Water distribution
 Water constitutes
 60% total body weight
 40% intracellular (2/3rd
of total)
 20% extracellular (1/3rd
of total)
 15% interstitial (3/4th
of ECF)
 5% intravascular ( 1/4th
of ECF)
 Major electrolytes
 Extracellular- Na, Cl, HCO3
 Intracellular- K, Mg, Ca, proteins
 ICF & ECF are in osmotic equilibrium
 Water follows sodium

3. Electrolytes
 Help maintain homeostasis
 Regulate
 Cardiac & neurological function
 Oxygen delivery
 Acid-base balance etc.
 Common etiology
 Increased or decreased ingestion
 Increased or decreased excretion

4. Evaluation
 Body weight
 Pulse, blood pressure, edema, JVP
 Urine output
 Serum electrolytes
 Urine electrolytes- Fractional excretion
FEx (%)= Ux/Sx÷Ucr/Scr x 100
 Serum osmolality-
Osmolality= 2Na+Glucose/18+BUN/2.8

5. Na & water homeostasis
 Blood osmolality-
 Osmoreceptors in hypothalamus- control thirst
 Release of AVP from hypothalamus/pituitary- acts on
V1 receptor- on vascular smooth muscle cells
V2 receptors- in collecting duct- water reabsorption
 Blood pressure & volume-
 Decrease- JG apparatus in kidney- releases renin, that leads to
production of angiotensin II- vasoconstriction, aldosterone
release (Na reabsorption), cardiac contractility, stimulates thirst
 Increase- ANP/BNP- act on kidneys to reduce renin /AT-II-
cause vasodilation & inhibit aldosterone release

6. Hyponatremia
 Serum Na < 135 mEq/l.
 Mostly due to abnormal water handling,
causing defective urinary dilution
 Basic causes-
 Unregulated release of ADH
 Reduced GFR
 Impaired tubular reabsorption/transport/permeability

7. Causes
 Isotonic (280-295)- severe hyperlipidemia or
hyperproteinemia
 Hypertonic (>295)- hyperglycemia, mannitol
 Hypotonic (<280)-
 Hypervolemic- CHF, CLD, CRF/NS
 Euvolemic- SIADH, thyroid/cortisol deficiency, postoperative,
marked free water intake (beer/psychogenic)
 Hypovolemic-
 Extrarenal loss- UNa<10- diarrhea/vomiting, sweating/burn
 Renal loss- UNa>20- diuretics, renal disease, mineralocorticoid
deficiency/Addison’s disease, cerebral salt wasting

8. Evaluation
 Symptoms of hyponatremia
 Primarily CNS
 Related to severity & rapidity
 History- to elicit cause
 Examination- for volume status
 Investigation
 Serum & urine electrolytes
 Serum & urine osmolality

9. Treatment
 Water restriction, loop diuretics, oral salt in
hypervolemic hyponatremia
 Normal saline- 0.9%- in hypovolemic hyponatremia
 Vasopressin antagonists- Vaptans-
for hyper/euvolemic hyponatremia
 Correction depends on severity & rapidity of
hyponatremia
 If severe/rapid, 3% hypertonic saline
 Rate of correction- 0.5-1 mEq/L/Hr
 Rapid correction may cause CPM or
osmotic demyelination syndrome characterized by
flaccid paralysis, dysarthria, dysphagia

10. Hypernatremia
>145 mEq/L
Caused by a relative deficit of free water
Primary defense- thirst

11. Causes
 Hypovolemic- Uosm.>400
 Inadequate intake of water
 Extreme sweating
 DM, osmotic diuretics
 Severe watery diarrhea
 Euvolemic- Uosm.<250
 Diabetes insipidus- central or nephrogenic
 Hypervolemic- mild

Mineralocorticoid excess- Conn’s or Cushing’s

12. Management
 Symptoms-
 Lethargy, irritability, seizures, coma
 Examination- volume status
 Investigation- S & U- elec. & osm.
 Treatment- free water- oral /IV
 Rate of correction- ~1 mEq/L/hr.

13. Hypokalemia
<3.5 mEq/L
Aldosterone- facilitates K excretion at
distal renal tubules
Most important regulator of K

14. Causes
 Inadequate intake
 GI loss
 Renal-
 Diuretics- thiazides, loop diuretics, Amphotericin, Cisplatin
 Excessive mineralo/glucocorticoids
 Tubular defect- RTA type I/II
 Low Mg
 Intracellular shift-
 Alkalosis
 Insulin
 Periodic paralysis

15. Evaluation
 Symptoms-
 Muscular weakness, myalgia, cramps, constipation
 Flaccid paralysis, hyporeflexia, tetany
 Rhabdomyolysis, respiratory depression
 Serum K
 Urine K- >40 with urinary loss &
<20 with extrarenal loss
 ECG changes-
 Flat T-wave, U-wave, prolonged QT-interval
 Arrythmias

16. Treatment
 Address the cause
 Deficit- 4-5 mEq/kg for each 1 mEq/L
decrease in serum K
 Mild deficiency- oral K
 IV K- 40 mEq/L @ 40 mEq/L/h max.
 K sparing diuretics- Spironolactone
 Correct Mg deficit
 Frequent K monitoring

17. Hyperkalemia
>5 mEq/L

18. Causes
 Spurious
 Delayed sample processing, faulty sample collection
 Marked leuco/thrombo-cytosis
 Decreased excretion
 Acute or chronic kidney disease
 Drugs- ACEI, K sparing diuretics, NSAIDs, trimethoprim, pentamidine,
cyclosporin, tacrolimus
 Mineralocorticoid deficiency- Addison’s
 Type IV RTA- DM, sickle cell dis., obstructive nephropathy
 Excessive release from cells
 Burns, rhabdomyolysis, tumor lysis syndrome
 Acidosis, low insulin, beta-blockers
 Increased intake

19. Evaluation
 Non-specific symptoms
 Get h/o drugs & kidney disease
 Serum K
 Serum Cr., CPK, cortisol
 Renal US
 ECG-
 Reduced P wave, peaked T wave, widened QRS complex

20. Treatment
 Urgent-
 Calcium gluconate- decreases myocardial excitability
 Insulin-glucose- intracellular shift of K
 Sodium bicarbonate- acidosis shifts K in cell
 Salbutamol- shifts K in cell
 Dialysis- refractory cases
 Preventive-
 Diuretics- HCTZ or loop diuretics
 K-binding resin- Polystyrene sulfonate- Kayexelate

21. Hypocalcemia
 Serum Ca<9 mg/dl or
ionized Ca<4.5 mg/dl
 Causes-
 Absent PTH- hereditary, post-Sx
 Ineffective PTH- CRF
 Inadequate vitamin D
 Malabsorption
 Hypo/hypermagnesemia

22. Management
 s/s-
 Cramps, tetany, paresthesias- lips/extremities, seizures
 Trousseau & Chvostek sign
 Serum Ca, PO4, albumin, Cr, PTH
 ECG- prolonged QTc
 CT scan- B/L basal ganglia calcification
 Treatment-
 IV Ca gluconate
 Oral Ca- carbonate/citrate & vitamin D
 Correct Mg levels

23. Hypercalcemia
 Serum Ca >10.5 mg/dl
 Causes-
 Primary hyperparathyroidism
 Malignancy- bone mets, MM, paraneoplastic
 Elevated vitamin D- sarcoidosis, lymphoma
 Paget’s disease of bone
 Immobilization

24. Management
 s/s-
 Groans-constipation, moans, bones-pain, stones-renal,
psychiatric overtones-depression/confusion
 Polyuria , PUD
 Look for e/o malignancy
 Serum Ca, PO4, PTH, PTHrp
 ECG- shortened QT interval
 Treatment-
 Rehydration- oral/IV, with loop diuretics
 Bisphosphonates- inhibit osteoclast activity, oral/IV
 Glucocorticoids- increase urinary excretion,
decrease intestinal absorption