Water, Electrolyte, Acid-Base, Hemodynamic Disorders

  >   Rahul's Noteblog   >   Notes on Pathology   >   Water, Electrolyte, Acid-Base, Hemodynamic Disorders

Body Water:

• TBW = 60% BW.

Extracellular vs Intracellular:

• Extracellular cation = Na+.

• Intracellular cation = K+.


• POsm ~ Na+ concentration in serum ~ number of solutes in plasma.

Sodium and POsm:

• Hyponatremia = decreased POsm; water shifts from ECF to ICF.

• Hypernatremia = increased POsm; water shifts from ICF to ECF.

Total Body Sodium Levels:

• Increased TBNa = body cavity effusions; water shifts to ECF from ICF.

• Decreased TBNa = volume depletion; water shifts to ICF from ECF.

Hydrostatic and Oncotic Pressure:

• Increased hydrostatic pressure or decreased oncotic pressure causes fluid to flow outward.

Normal Saline Infusion:

• In patients with fluid loss, normal saline is infused to maintain normal BP; normal saline approximates plasma tonicity (POsm).

Causes of isotonic disorders (normal POsm and serum Na+):

• Isotonic loss: diarrhea, blood loss.

• Isotonic gain: excessive saline.

Causes of hypotonic disorders:

• Hypertonic loss of Na: loop diuretics, Addison's disease, 21-Hydroxylase deficiency.

• Gain of H2O: SIADH.

• Hypotonic gain of Na in ICF/ECF: right-sided heart-failure, cirrhosis, nephritic syndrome.

Causes of hypertonic disorders:

• Hypertonic gain of Na: infusion of Na-containing antibiotics, infusion of NaHCO3.

• Hypotonic loss of Na: osmotic diuresis (glucose), sweating, infant diarrhea.

• Loss of H2O: water loss in fever, diabetes insipidus.

• Hyperglycemia: diabetic ketoacidosis, hyperosmolar nonketotic coma.

Potassium disorders:

• Controlled by aldosterone (direct relationship), arterial pH (more pH, less K).

• Hypokalemia: muscle weakness, U waves on ECG, polyuria, rhabdomyolysis.

• Hyperkalemia: ventricular arrhythmias, peaked T waves on ECG, muscle weakness.

K loss caused by:

• Decreased intake, GI loss, renal loss, alkalosis.

Acid-base disorders:

Respiratory acidosis:

• Hypoventilation and CO2 retention.

• Basic blood (increased HCO3) compensates for acidic lungs (decreased pH) by causing metabolic alkalosis. Very high pCO2.

• Findings: somnolence, cerebral edema.

Respiratory alkalosis:

• Hyperventilation with CO2 elimination.

• Acidic blood (decreased HCO3) compensates for basic lings (increased pH) by causing metabolic acidosis. Very low pCO2.

• Findings: light-headedness, tetany (Ca binds to albumin, so decreased Ca).

Metabolic acidosis:

Increased anion gap:

• Decreased serum HCO3- due to excess H+.

• Causes: lactic acidosis, ketoacidosis, renal failure, salicylate poisoning, antifreeze, window-washing fluid/paint thinner.

Normal anion gap:

• Decreased serum HCO3- due to inability to synthesize HCO3- in the kidneys.

• Decreased pH, low pCO2.

• Respiratory alkalosis is compensation.

• Causes: diarrhea, Type I/II/IV renal tubular acidosis.

• Findings: Kussmaul (rapid) breathing, warm shock, osteoporosis.

Metabolic alkalosis:

• Loss of H+ or gain of HCO3-.

• Increased pH, increased HCO3-, increased pCO2.

• Respiratory acidosis is compensation.

• Causes: vomiting, mineralocorticoid excess, thiazide and loop diuretics.

• Findings: ventricular arrhythmias, tetany.

Mixed disorders:

• Normal pH.

• Extreme academia.


Fluid moves out of blood vessels due to:

• Increased vascular hydrostatic pressure; decreased vascular oncotic pressure; renal retention of Na and H2O; increased vascular permeability, lymphatic obstruction, increased synthesis of extracellular matrix components.

• Types: Transudate (protein-poor), exudate (protein-rich), lymphedema (protein-rich), glycosaminoglycans.


• Due to: endothelial cell injury, blood stasis, hypercoagulability.

Types of thrombi:


• Deep veins below knee; contain entrapped RBCs, WBCs, and platelets; use heparin and warfarin.


• Muscular and elastic arteries; composed of platelets; use aspirin.


• Heart (due to acute MI) and aorta (due to aneurysms); lines of Zahn; contain platelets (held by fibrin), RBCs; use aspirin.



• Originates in femoral vein, pelvic vein, or vena cava; occludes pulmonary artery branches; sudden death.


• Travel in arterial system; originate in left ventricle after acute MI, or in left atrium; get stuck in lower extremities, brain, SI, spleen, and kidneys; cause infarctions in brain, spleen, kidneys, digits.


• Originate in fractures of long bones; damage vessel endothelium; restlessness, coma, delirium.

Amniotic fluid:

• During labor or postpartum; amniotic fluid in blood; dyspnea, cyanosis, hypotension, bleeding; DIC.

Decompression sickness:

• Gas embolism.

• Nitrogen gas forced out of alveoli, and dissolves in blood and tissues.

• Rapid ascent causes Nitrogen to expand and cause bubbles in tissue and blood.

• Pain in joints, muscle, and bones.

• The bends.

• Pneumothorax, pulmonary embolus.

• Use recompression, followed by slow decompression.


• Definition: reduced perfusion causing impaired oxygenation of tissue.


• Excessive fluid/blood loss; no initial effect on hemoglobin/hematocrit; decreased CO, increased PVR; cold, clammy skin, hypotension.


• Due to acute MI; decreased CO; increased PVR; chest pain.


• Gram negative pathogen infections; released vasodilators, PGI2; alternate complement pathway activated; initial increase in CO; decreased PVR; warm skin, bounding pulse, acute RDS, DIC.

Complications associated with shock:

• Ischemic acute tubular necrosis, multiorgan dysfunction, lactic acidosis due to tissue hypoxia.

Additional Reading:

Basic Pathology

1. Cell Injury
2. Inflammation and Repair
3. Immunopathology
4. Water, Electrolyte, Acid-Base, Hemodynamic Disorders
5. Genetic and Developmental Disorders
6. Environmental Pathology
7. Nutritional Disorders
8. Neoplasia
9. Vascular Disorders
10. Heart Disorders
11. Red Blood Cell Disorders
12. White Blood Cell Disorders
13. Lymphoid Tissue Disorders
14. Hemostasis Disorders
15. Blood Banking and Transfusion Disorders
16. Upper and Lower Respiratory Disorders
17. Gastrointestinal Disorders
18. Hepatobiliary and Pancreatic Disorders
19. Kidney Disorders
20. Lower Urinary Tract and Male Reproductive Disorders
21. Female Reproductive and Breast Disorders
22. Endocrine Disorders
23. Musculoskeletal Disorders
24. Skin Disorders
25. Nervous System Disorders
26. Notes on Tissue Regeneration
27. A Table of Bleeding Disorders
28. FAQ on Structure and Function of Red Blood Cells
29. FAQ on Components of Blood
30. Notes on Hemostatic Mechanisms
31. What is Fever?
32. What is Edema?
33. FAQ on Blood Pressure
34. FAQ on principles of fluid and flow dynamics of Blood
35. Causes of Thrombocytopenia
36. Squamous cell carcinoma of head and neck mucosa
37. Four tumors which never metastasize to the brain
38. What is caustic injury?
39. What causes Peripheral Edema?

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