Electrolytes and acid base status

Elecrolytes

negative ions (anions) and positive ions (cations) of elements that are found in all body fluids of all organisms. used with water balance, fluid osmotic pressure, and normal muscular and nervous functions.

acid base status

depends on electrolytes, refers to steady state of pH in the body. indicates hydrogen ions. power of 10 difference in hydrogen ions. normal range is 7.35-7.45.

acidosis

when pH is less than 7.3. excess hydrogen. any other cause is referred to as metabolic alkalosis.

alkalosis

pH is greater than 7.4. respiratory kinds have to do with the lungs. any other cause is referred to as metabolic alkalosis.

buffers

substances that alter hydrogen ion concentration. located both intracellularly and extracellularly and multiple buffering systems are present in the body. both respiratory and renal systems work together. the respiratory system can change it in minutes but the renal system can take days to restore levels

bicarbonate buffer (HCO3)

helps with acidic pH by binding to excess hydrogen ions to form carbonic acid (H2CO3). this is then broken down to water and carbon dioxide. the reaction is mediated by carbonic anhydrase. kidneys help regulate concentration of bicarbonate by actively secreting or resorbing it form the filtrate in response to the blood pH. the reaction is reversible.

potassium buffer

changes in concentration affect the plasma concentration of hydrogen. Both potassium and hydrogen are positively charged that move freely between intracellular fluid and extracellular fluid. Decreased concentration of plasma potassium causes potassium to move from cells to ECF and hydrogen ion to move ICF. increased potassium causes potassium to move ICF and hydrogen to move ECF.

Protein buffer

hemoglobin molecules serves as a blood buffer as a result of its ability to bind carbon dioxide and hydrogen.

respiratory acidosis and alkalosis

if RR decreases the rate of excreted carbon dioxide decreases. it reacts with water to form carbonic acid. then it becomes hydrogen ions and water. this will show up as partial pressure carbon dioxide (PCO2). Increased PCO2 is hypercapnia. decrease in PCO2 is called hypocapnia.

metabolic acidosis and alkalosis

excess ketones are produced when glucose metabolism is abnormal (diabetes mellitus) which can overwhelm the buffer system. decreasing the blood bicarbonate level. vomiting can also cause metabolic alkalosis and increases blood bicarbonate levels.

base excess

amount of strong acid or base required to titrate 1 L of blood to a pH of 7.4 at 37 celcius while the PCO2 is held constant at 40 mm Hg. calculated from pH, PCO2 and hematocrit measurements. may be used to evaluate the degree of metabolic acid base disturbance. negative value indicates metabolic acidosis, and a positive value indicates metabolic alkalosis.

cation

sodium+, potassium+, calcium++, magnesium++ and hydrogen+

anion

chlorine, Bicarbonate (HCO3), phosphate (PO4)

indirect potentiometry (per unit of plasma)

procedure that measures electrolytes in total plasma volume. Electrolytes are distributed in the aqueous portion of plasma and not found in the lipid portion. volume displacement by lipids typically affects measurement making them artificially decreased. (triglyceride samples of 1500 mg/dL.

direct potentiometry (per unit of plasma)

measure electrolytes in aqueous phase only are better for high concentrations of lipids in measuring electrolytes. Arterial samples are ideal for analysis. Venous samples have significantly different normal reference ranges. exposure to room air results in alterations in the concentration of dissolved gases in the sample and can affect pH.

sodium

elevated in

• dehydration

• renal failure

• fluid loss

• Hyperaldosteronemia

• · Evaporation of serum sample

Decreased in

• · Hypoadrenocorticism

• · Fluid loss

• . Severe liver disease

• . Hookworms

• · Renal disease

• · Diuretics

• . Hypotonic fluids

• · Diabetes mellitus

• . Diet

• · Hyperlipidemia

• · Marked hyperproteinemia

major cation of plasma and ECF. it affects osmotic pressure. kidneys filter sodium through glomeruli and resorbed back into the body as needed through the tubules in exchange for hydrogen ions. Hypernatremia refers to elevated levels of sodium. Hyponatremia is decreased levels of sodium. sodium salt of heparin should not be used as an anticoagulant, because it can falsely elevate the results. Hemolysis doesn’t significantly alter results but may dilute the sample with erythrocyte fluid and cause falsely lower results

potassium

Elevated in

• · Renal failure

• . Postrenal conditions

• · Hypoadrenocorticism

• . Acidosis

• · Gastrointestinal conditions

• . Massive muscle trauma

• · Dehydration

• . Drugs

• · Hypoaldosteronism

• · Thrombocytosis

• · Hyperkalemic periodic paralysis

. Decreased in

• · Alkalosis

• . Dietary deficiency

• · Potassium free fluids

• · Bicarbonate administration

• . Drugs

• · Gastrointestinal fluid loss

• · Hyperadrenocorticism

• · Hyperaldosteronism

• · Insulin therapy

• · Diuresis

• · Diabetic ketoacidosis

• · Renal conditions

• · Total parenteral nutrition

• · Hypokalemic periodic paralysis

Potassium is the major intracellular cation. It is important

for normal muscular function, respiration, cardiac function,

nerve impulse transmission, and carbohydrate metabolism. In

acidotic animals, potassium ions leave the ICF as they are

replaced by hydrogen ions, thereby resulting in elevated plasma

potassium levels, or hyperkalemia. The plasma potassium level

may also be elevated in the presence of cellular damage or

necrosis, which causes the release of potassium ions into the

blood. Decreased plasma potassium levels, or hypokalemia,