A short presentation on fluid balance and distribution, electrolyte balance and acid-base balance.

1. Ilkin Bakirli
Slovak Medical University

2. Contents
• Fluid balance
• Electrolyte balance
• Acid-base balance

3. Fluid
Balance

4. Fluid distribution
• Intracellular Fluid (ICF): The amount of water that’s inside our cells accounts for
2/3rds of ourTotal BodyWater (TBW).
• Extracellular Fluid (ECF): The amount of water that surrounds our cells accounts
for 1/3 of ourTBW. ECF is also known as interstitial fluid because it’s the fluid in
between the cells.
• There’s 3 types of ECF:
-Tissue fluid: 2/3rd of ECF
-Blood plasma: 1/3rd of ECF
-Transcellular fluid: Often not calculated as a fraction of the extracellular fluid, but
it is about 2.5% ofTBW.

6. Functions of fluid in the body
• All reactions occur in a liquid medium
• Chemical and bioelectrical regulation in cells
• Substance transport
• O2 and CO2 transport
• Dilutes toxins and waste products
• Distributes heat in the body
• 3 types of fluid: isotonic, hypotonic and hypertonic

7. Composition of body fluids
• Nonelectrolytes (most organic molecules, do not dissociate in water, no charge)
• Electrolytes (dissociate in water, include salts, acids, bases, some proteins)
• Major extracellular cation= sodium (Na+)
• Major extracellular anion= chloride (Cl-)
• Major intracellular cation= potassium (K+)
• Major intracellular anion= phosphate (P-²)

8. Fluid regulation-ADH
• Produced in the posterior pituitary gland (neurohypophysis)
• The amount of water reabsorbed is proportional to ADH release
• When ADH levels are low, water is not reabsorbed in the collecting ducts in the
kidneys, resulting in polyuria with diluted urine
• When ADH levels are high, most of the water is absorbed, resulting in oliguria and
concentrated urine

9. Fluid movement
• Constant total body water and osmolarity control with ingestion and excretion
• Hydrostatic and osmotic pressure differentials
• Movement of fluids by osmosis, diffusion and active transport

10. Disorders of fluid balance
• Deficient fluid- hypovolemia, dehydration
• Excess fluid volume: hypervolemia, water intoxication (hyperhydration)
• Electrolyte imbalance: deficit or excess
• Acid base balance

11. Dehydration
• Hyperosmolarity, hyperglycemia, hyperalbuminemia, increased haemoglobin,
increased creatinine, increased urea, increased uric acid
• Etiology: inadequate intake, old age, psychiatric, unconscious, increased urinary
losses (DM1, DM2, DI, diuretic use), sweating, burns, bleeding
• Clinical: dry skin, xerophtalmia, xerostomia, mucous membrane dryness, thirst,
oliguria
• Treatment: fluid and electrolyte replacement

12. Hyperhydration
• Etiology: iatrogenic, ↓elimination (renal failure, SIADH)
• Clinical: edema, ascites, hypervolemia, hypertension, ↓electrolytes
Severe cases: increased ICP, cerebral edema, bradycardia
• Treatment: cause, reduce water intake, diuretics, dialysis

13. Electrolyte
balance

14. Hypernatremia (Na+ >145mmol/L)
• Normal serum Na+ range: 135mmol/L -145mmol/L
Etiology
1. Hypervolemic hypernatremia: hyperaldosteronism, excessive fluid administration
2. Euvolemic hypernatremia: fever, lithium use
3. Hypovolemic hypernatremia: diabetes insipidus, vomiting, diarrhoea, diuretics,
CKD
• Clinical: strong thirst, ↓appetite, nausea, vomiting, confusion, muscle twitches
• Treatment: cause, stop infusion, furosemide in hypervolemic

15. Hyponatremia (Na+ <135mmol/L)
Etiology
1. Hypervolemic hyponatremia: nephrotic syndrome, HF, cirrhosis, renal causes
2. Euvolemic hyponatremia: SIADH, Addison’s disease
3. Hypovolemic hyponatremia: ascites, dehydration, burns
• Clinical: anorexia, nausea, HTN, confusion, dehydration
• Diagnosis: Na+, K+, ECG, medication history, HF?, SIADH?
• Treatment: 1. reduce fluid intake/ 2. slow Na+ substitution / 3. NaCl infusion

16. Hyperkalemia (>5.0mmol/L)
• Normal serum K+ range: 3.6mmol/L – 5.0mmol/L
Etiology
1. ↑K+ supply: (penicillin, blood transfusion, ↑intake)
2. ↓K+ excretion: (AKF, Addison’s disease, aldosterone deficiency, ACEI)
3. Shift from ICF to ECF (acidosis, diabetic coma, digoxin intoxication)
• Clinical: asymptomatic to muscle twitches to paralysis, arrhythmias
• Diagnosis: ↑serum K+, ECG peakT waves, broad QRS, longer PQ interval
• Treatment: calcium gluconate, concentrated glucose, long term, dialysis, loop
diuretics

17. Hypokalemia (<3.6mmol/L)
Etiology:
1. Reduced intake
2. Increased loss (diarrhea, vomiting, renal losses in ARF, RTA, chronic GN,
diuretics, hyperaldosteronism, hypercorticolism, steroid therapy)
3. Alkalosis
4. Insulin treatment of coma
• Clinical: asymptomatic to fatigue, constipation, weak reflexes, extrasystoles,
metabolic alkalosis, nephropathy
• Diagnosis: serum and urine K+ levels, acid-base balance
• Treatment: K+ supplements, PCl in metabolic acidosis

18. Hypercalcemia (>2.7mmol/L)
• Normal serum Ca++ range: 2.1mmol/L – 2.7mmol/L
Etiology
1. Bone malignancy induced (suppression of PTH)
2. Hyperparathyroidism
3. Drug induced (vit D or vit A intoxication, thiazide diuretics, Ca++ intake)
4. Familial hypercalciuric hypercalcemia
• Clinical: polyuria, thirst, nausea, vomiting, psychosis, arrhythmias
• Diagnosis: ↑serum Ca++, ↑PTH in cancer
• Treatment: parathyroidectomy, bisphosphonates, fluids

19. Hypocalcemia (<2.1mmol/L)
Etiology
1. Hypoparathyroidism / parathroidectomy (decreased absorption in intestines)
2. Vit D deficiency
3. CKD (increased excretion)
• Clinical: tetany, osteoporosis, rickets, paraesthesia, chvostek sign +
• Diagnosis: clinical and serum ↓Ca++
• Treatment: Ca++ I.V / oral calcium carbonate +Vit D

20. Phosphate disorders
• Hyperphosphatemia
Etiology: renal insufficiency (increased uptake)
Clinical: lack of appetite, vomiting, diarrhea, polyuria
Treatment: phosphate restriction and dialysis
• Hypophosphatemia
Etiology: increased losses by the kidneys, decreased absorption by intestines
Treatment: phosphate supplements

21. Magnesium disorders
• Hypermagnesemia
Etiology: renal insufficiency
Clinical: neuropathy, hypoventilation, bradycardia
Treatment: furosemide, Ca++ supplements
• Hyp0magnesemia
Etiology: decreased reabsorption and increased excretion by the kidneys
Clinical: increased neuromuscular excitability up to tetany
Treatment: Mg+ replacement

22. Acid-base
balance

23. Acid-base balance
• Normal pH: 7.36-7.44
• H+ 36-44nmol/L
• Acidosis: pH <7.36
• Alkalosis: pH >7.44
• Homeostasis
1. Buffer systems: HCO3- , HPO4-2
2. Lungs: hypo/hyperventilation ; H+ + HCO3-  H2CO3  H20 + CO2
3. Kidneys: H+ excretion / resorption, HCO3- excretion / resorption

24. Metabolic acidosis (pH <7.36)
• Etiology: diabetic ketoacidosis, fasting, alcoholism, lactic acidosis, CKD (acid
retention), HCO3- losses (diarrhea)
• Symptoms: kaussmal’s breathing, hyperkalemia, hyperventilation
• Treatment: gradual correction with intravenous sodium bicarbonate

25. Metabolic alkalosis (pH >7.44)
• Etiology: dehydration, diuretics, diarrhea, vomiting, increased HCO3- intake
• Clinical: tetany, confusion, increased neuromuscular excitability, hypoventilation
• Treatment: Cl- and K+ replacement, acetazolamide

26. Respiratory acidosis (pH <7.36)
• Etiology: respiratory centre failure (pulmonary diseases), neuromuscular
disorders, chest wall trauma, diseases of the airways
• Clinical: hypoventilation, confusion, weakness, comatose, hypoxemia,
papilledema
• Treatment: symptomatic, O2, mechanical ventilation

27. Respiratory alkalosis (pH >7.44)
• Etiology: psychogenic hyperventilation in hysteria, stroke, lung diseases,
metabolic disorders
• Clinical: hyperventilation, dizziness, dry mouth
• Treatment: cause, breath into a paper bag

28. Diagnosis of acid base disorders
• History, clinical
• ABG (pH, pO2, pCO2, HCO3-, Na+, K+, Cl-)
• Normal pCO2 : 33-45mmHg
• Normal HCO3-: 22-28mmol/L