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Serum Electrolytes
This document discusses sodium and potassium levels in the body. It begins by outlining the distribution of sodium, potassium, and water in the body and their roles in homeostasis. It then describes pathological conditions that can result from imbalances in sodium and potassium levels. Various techniques for estimating serum sodium and potassium are also outlined, including ion selective electrodes, atomic absorption spectroscopy, and flame emission photometry.
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Serum Electrolytes
- 1. Estimation of Sodium& Potassium Ashikh Seethy Senior Resident Department of Biochemistry
- 2. Objectives: At the endof this briefing, you should be able to describe: The distribution of Na+, K+ and water in the body. The role of Na+ and K+ in maintenance of homeostasis. The different pathological conditions in which Na+ and K+ balance is disturbed. Various techniques utilized for estimation of serum Na+ and K+.
- 3. The Body asOrganized “Solutions” In the body of a young adult male: Proteins:18% Minerals: 7% Fat: 15% Water: 60%
- 4. Fluids Compartments: Total BodyWater: 42 L Intra-cellular Fluid 28 L 66% Extra- cellular Fluid 14 L 34% Interstitial Fluid 10.5 L Plasma 3.5 L
- 5. Electrolytes and Proteins areUnequally Distributed Among the Body Fluids
- 6. Osmolality: Measure ofthe number of osmotically active particles in serum. Calculated serum osmolality = (2 x serum Na+) + Glucose + Urea (in mmol/L). Estimated in lab by Osmometer (based on colligative properties). Reference interval: 275–295 mOsmol/kg of water.
- 7. Water Balance isRegulated by the Hypothalamus, the Neurohypophysis and the Kidneys
- 8. Action of Vasopressinin Renal Tubules:
- 9. Water and electrolytescan be lost through Gastrointestinal tract Skin Bronchial tree etc. But kidneys are the only organs able to conserve or excrete electrolytes and water under tight regulatory control.
- 10. Osmolality: Carbonic Anhydrase Inhibitors Loop Diuretics BartterSyndrome Thiazide Diuretics Gitelman Syndrome Minerallocorticoid-R Antagonists Liddle Syndrome ENaC Na+
- 11. Nephron is theTarget of Many Hormones
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- 13. Sodium: Principle cationof ECF Reference interval (Plasma): 136 to 145 mmol/L Recommended daily dietary intake : < 2 g (<5 g salt) Na+ levels are regulated by the kidneys Functions: Maintains normal water distribution and osmolality Maintenance of membrane potential Absorption of chloride, amino acids, and glucose
- 14. Abnormality in SodiumLevels Affects Neuronal Function: Plasma sodium:136 to 145 mmol/L Hyponatremia: Plasma sodium <135 mmol/L Hypernatremia: Plasma sodium >145 mmol/L
- 15. Hypernatremia ECF Volume Increased • Totalbody water↑ • Total body sodium↑↑ Not Increased • Total body water↓↓ • Total body sodium↓ Hypertonic NaCl NaHCO3 Insensible water loss GI water loss Central Diabetes Insipidus Nephrogenic Diabetes Insipidus Osmotic Diuresis
- 16. Hyponatremia Volume Status • Hypovolemia • Totalbody water↓ • Total body sodium ↓↓ • Euvolemia • Total body water↑ Total body sodium ↔ • Hypervolemia • Total body water↑↑ Total body sodium ↑ UNa> 20 UNa< 20
- 17. Hyponatremia Volume Status • Hypovolemia • Totalbody water↓ • Total body sodium ↓↓ • Euvolemia • Total body water↑ • Total body sodium ↔ • Hypervolemia • Total body water↑↑ Total body sodium ↑ UNa> 20 UNa< 20 Renal losses Diuretics ↓↓ Minerallocorticoids Osmotic diuresis Metabolic alkalosis
- 18. Hyponatremia Volume Status • Hypovolemia • Totalbody water↓ • Total body sodium ↓↓ • Euvolemia • Total body water↑ • Total body sodium ↔ • Hypervolemia • Total body water↑↑ • Total body sodium ↑ UNa> 20 UNa< 20 Renal losses Diuretics ↓↓ Minerallocorticoids Osmotic diuresis Metabolic alkalosis Extra-renal losses Vomiting Diarrhea Trauma Pancreatitis
- 19. Hyponatremia Volume Status • Hypovolemia • Totalbody water↓ • Total body sodium ↓↓ • Euvolemia • Total body water↓ • Total body sodium ↔ • Hypervolemia • Total body water↑↑ Total body sodium ↑ UNa> 20 UNa< 20 Nephrotic syndrome Cirrhosis Cardiac failure Acute Renal Failure Chronic Renal Failure
- 20. Hyponatremia Volume Status • Hypovolemia • Totalbody water↓ • Total body sodium ↓↓ • Euvolemia • Total body water↑ • Total body sodium ↔ • Hypervolemia • Total body water↑↑ Total body sodium ↑ Una> 20 Glucocorticoid deficiency Polydipsia SIAD- Syndrome of Inappropiate Antidiuresis
- 21. Hyponatremia Volume Status • Hypovolemia • Totalbody water↓ • Total body sodium ↓↓ • Euvolemia • Total body water↑ • Total body sodium ↔ • Hypervolemia • Total body water↑↑ Total body sodium ↑ • Total body water ↔ • Sodium intake↓ Beer potomania Nutrient restricted diet
- 22. Potassium: Principle intracellularcation (140 mmol/L) High cellular concentrations maintained by active transport mechanism via Na+/K+ ATPase pump Reference interval (Plasma): 3.5 – 5.0 mmol/L Normal daily dietary intake : at least 90 mmol/day (3510 mg/day) Functions: Maintenance of ionic gradients which is required for: • Nerve impulse transmission • Muscle contractility
- 23. Abnormality in PotassiumLevels Adversely Affects Cardiac Function : Plasma Potassium:3.5 to 5.0 mmol/L Hypokalemia: Plasma potassium <3.5 mmol/L Hyperkalemia: Plasma potassium >5.5 mmol/L Cardiac muscles- Arrhythmias; Cardiac arrest Skeletal muscles Intestinal muscles
- 24. Hyperkalemia Pseudohyperkalemia: • Hemolysis • Increasein blood cells Intra- to Extracellular Shift • Acidosis • Digoxin • Trauma • Tumor lysis • Drugs Inadequate Excretion • Inhibition of RAAS • Chronic kidney disease • Adrenal insufficiency • ↓ Renin production
- 25. Hypokalemia Decreased Intake: • Starvation •Clay ingestion Extra- to Intracellular Shift • Alkalosis • Insulin • Anabolic states • Drugs • Thyrotoxicosis Increased Loss • Diarrhea, sweating • Diuretics other than potassium sparing diuretics • Conn syndrome • Cushing syndrome • Bartter’s syndrome • Gitelman’s syndrome • Liddle’s syndrome • Diabetic ketoacidosis
- 26. Sample Considerations: Serum,heparinized plasma or whole blood may be used for Na+ estimation Whole blood or heparinized plasma preferred for K+ Samples should be maintained near 25 °C Preferably plasma to be separated by high speed centrifugation without cooling Hemolysis to be avoided Avoid prolonged tourniquet use and fist clenching
- 27. Techniques for Estimationof Na+ and K+ Ion selective electrode (ISE) Atomic absorption spectroscopy Flame emission photometry
- 28. Ion Selective Electrode Ionselective membrane: • Na+ : Glass • K+ : Valinomycin
- 29. Flame Emission Photometry Theintensity of emission is proportional to the number of excited atoms, which is indeed proportional to the concentration of the element in the solution.
- 30. Flame Emission Photometry Ion selective electrode (ISE) Atomic absorption spectroscopy
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