Electrolyte Disorder and Blood Gas Level PDF

Electrolyte Disorder and Blood Gas Level  Electrolyte Substance when dissolved in solution separates into ions and is able to carry an electrical current. Cation: positively charged electrolyte Anion: negatively charged electrolyte Intracellular Fluid Extracellular...

Electrolyte Disorder and Blood Gas Level  Electrolyte Substance when dissolved in solution separates into ions and is able to carry an electrical current. Cation: positively charged electrolyte Anion: negatively charged electrolyte Intracellular Fluid Extracellular Fluid Major cations Major cations Potassium, Magnesium, Sodium, Potassium, Sodium Calcium, Magnesium Major anions Major anions Phosphorus Chloride, Phosphorus  Electrolyte Electrolytes in the fluids help distribute the fluids inside and outside the cells, thus ensuring the appropriate water balance and acid-base balance to support all life processes. The concentrations of electrolyte in body fluids must be maintained within specific limits, and even a small deviation outside these limits can have serious or life- threatening consequences. Commonly measured in milliequivalents/liter (mEq/L)  Sodium Major cation in the ECF. Normal serum sodium range: 135-145 mEq/L Functions: Maintain fluid balance of ECF, thereby it controls the movements of water between fluid compartments. Transmission of nerve impulse. Muscle contraction. Level of Na+ in blood is controlled by: Antidiuretic hormone (ADH) Aldosterone – increases renal reabsorption Atrial natriuretic peptide – reduces renal reabsorption  Hyponatremia Serum Na+ < 135 mEq/L Causes: I. Extrarenal loss of sodium Gastrointestinal losses (e.g. vomiting and diarrhea) Sweat losses (e.g. endurance exercise) II. Renal loss of sodium Diuretic therapy Renal failure Addison’s disease: destruction of adrenal gland  aldosterone deficiency  increase sodium loss Diabetes mellitus: glucose in blood high (high osmolality)  water flows from cells to ECF to correct the rising osmolality  sodium in blood diluted  Hyponatremia Generally asymptomatic if Na+ level > 125 mEq/L Symptoms include: Headache Nausea, vomiting Muscle cramps Lethargy, restless, mental depression, confusion Seizure, coma, permanent head damage and death  Hypernatremia Serum Na+ > 145 mEq/L Causes: I. Excess sodium Over-vigorous sodium replacement therapy for patients with sodium depletion. Conn’s syndrome: excess secretion of aldosterone Cushing’s syndrome: excess secretion of cortisol  increase sodium retention II. Increased water loss Protracted vomiting, diarrhea, sweating Chronic kidney failure: inability to retain water Failure of thirst response (e.g. unconscious patients) ADH deficiency in diabetes insipidus: large volume of diluted urine produced (polyuria) Hypernatremia  Potassium Most abundant cation in the ICF. Normal serum potassium range: 3.5-5.2 mEq/L Functions: Keep the body’s fluids in balance Maintain blood pH Muscle contraction Nerve impulse conduction Level of K+ in blood is controlled by: Aldosterone – stimulates principal cells in renal collecting ducts to secrete excess K+  Hypokalemia Serum K+ < 3.5 mEq/L Causes: Inadequate K+ intake Diuretic therapy Conn’s syndrome: excess secretion of aldosterone  increase K+ loss. Bartter’s syndrome (autosomal recessive renal tubular disorder): affects the kidney’s ability to retain K+ Severe chronic diarrhea/vomiting Treatment for diabetic ketoacidosis – Insulin increased activity of Na+/ K+ pump Na+ moves into the ECF; K+ moves into cell  Hypokalemia No symptoms until K+ < 3.0 mEq/L If symptoms arise, they are related to function of potassium in transmission of nerve impulses to muscle. Muscle weakness with general lethargy Constipation due to impaired muscle tone of GI tract Muscular paralysis Cardiac muscle: arrhythmias (tachycardia, bradycardia)  Hyperkalemia Serum K+ > 5.2 mEq/L Causes: Renal failure Excessive potassium administration Severe tissue damage (trauma major surgery) – cells destruction release K+ into plasma Addison’s disease: autoimmune destruction of adrenal glands  deficiency in aldosterone  decreased sodium retention  increased K+ retention in blood Poor specimen handling – hemolysis of blood cells, delayed transport  Blood Gas Analysis Also known as arterial blood gas (ABG) test. Determine acidity (pH) of the blood – evaluate a person’s acid-base balance. Measure the levels of oxygen and carbon dioxide in the blood from an artery – evaluate a person’s respiratory, metabolic and renal function. Blood for an ABG test is taken from the artery.  Measurement of Blood Gas The analysis measures: Arterial blood pH measures the amount of hydrogen ions in blood. Blood pH: 7.35-7.45 Partial pressure of oxygen (PO ) is a measure of the pressure of 2 oxygen dissolved in the blood. It determines how well oxygen is able to flow from the lungs into the blood. PO : 10.6-13.3 kPa/ 75-100 mmHg 2 Partial pressure of carbon dioxide (PCO ) is a measure of the 2 pressure of carbon dioxide dissolved in the blood. It determines how well carbon dioxide is able to flow out of the body. PCO : 4.7-6.0 kPa/ 38-42 mmHg 2 Bicarbonate is a chemical that helps prevent the pH of blood from becoming too acidic or too basic. HCO - : 22-28 mmol/L 3  Acid-Base Disorders Components of the blood gas analysis are interrelated and the results must be considered together. Certain combinations of results, if abnormal, may indicate a condition that is causing acidosis or alkalosis. pH PCO2 HCO3- (mmHg) (mmol/L) Normal 7.35-7.45 38-42 22-28 Acidosis < 7.35 > 42 < 22 Alkalosis > 7.45 < 38 > 28  Respiratory Acid-Base Disorders Abnormalities in acid-base balance initiated by a change in the arterial carbon dioxide tension There are two respiratory acid-base disorders: Respiratory acidosis – Increased PCO2 Respiratory alkalosis – Reduced PCO2  Respiratory Acid-Base Disorders Respiratory acidosis Lower pH and an increased PCO2 Due to respiratory depression (not enough oxygen taken in and reduced elimination of carbon dioxide). Can be caused by: Inadequate ventilation (hypoventilation) Asthma Pneumonia Chronic obstructive lung disease (e.g. emphysema) Respiratory Acid-Base Disorders Respiratory alkalosis Raised pH and a decreased PCO2 Due to excessive loss of CO2 by hyperventilation of lungs. Can be caused by: Hypoxemia (reduced oxygen in blood) stimulates increased ventilation  respiratory alkalosis (e.g. high altitude, severe anemia) Cardiac failure Pain, anxiety  Metabolic Acid-Base Disorders Abnormalities that result from a primary alteration in H+ or HCO3-. There are two metabolic acid-base disorders: Metabolic acidosis – Reduced HCO3- Metabolic alkalosis – Increased HCO3-  Metabolic Acid-Base Disorders Metabolic acidosis Lower pH and decreased HCO3- Can be caused by: Failure of kidney to excrete H+ or reabsorb HCO3- Excess metabolic production of H+ (e.g. lactate acidosis & diabetic ketoacidosis)  the level of HCO3- will fall as ions are used to buffer these acids Increased loss of HCO3- from the body (e.g. diarrhoea)  Metabolic Acid-Base Disorders Metabolic alkalosis Elevated pH and increased HCO3- Can be caused by: Hypokalemia Chronic vomiting  loss of gastric acid and electrolytes  ICF ECF [Potassium] - [Potassium] - high low [Hydrogen] - [Hydrogen] – low high (pH is high) [Bicarbonate] - high  Renal Excretion of H+ Kidneys help regulate the H+ concentration of body fluids by excreting H+ in the urine.  Acid-Base Disorders Blood pH HCO3- PCO2 Condition Metabolic acidosis Metabolic alkalosis Respiratory acidosis Respiratory alkalosis