Acid – Base Fluid Balance

1. Acid – Base Fluid Balance

2. What is fluid balance Homeostasis – a state of body equilibrium or stable internal environment of the body Total Body Water – makes up 60% men’s weight 50% women’s weight Relationship between water & other electrolytes

3. Water • Occupies main locations • Intracellular fluid (ICF) • Within the cell • Extracellular fluid (ECF) • All body fluids such as: • Blood plasma • Interstitial fluid • Cerebrospinal fluid • Serous fluid • Aqueous & Vitreous humors of the eye • lymph

4. Water & Salt relationship • Water & sodium have a direct relationship • Low sodium ions in the extracellular fluid results in water loss from the blood into the tissue spaces & muscular weakness • Sodium & water are reabsorbed through the Loop of Henle in the kidneys • The systems that control the sodium levels • Keep the extracellular level of Na between 135 – 145 mEq/L • Keep the volume of extracellular fluid compartment WNL

5. Sodium levels • Sodium is mostly found in extracellular fluid. Sodium levels are controlled by 3 ways: • Renin – Angiotensin- Aldosterone System • ArtrialNatriuretic Factor • Sympathetic nervous system • Hypernatremia • Hyponatremia

6. Treatment of abnormal sodium levels • FYI in clinical patients: • Abnormal ECFV are due to problems with the sodium control system • Abnormal sodium concentration is due to problems with the water control mechanisms • What are some factors that can affect these?

7. Blood Acid – Base Balance • Normal blood pH? • 7.35 – 7.45 • If the pH (arterial) is above 7.45: alkalosis • If the pH (arterial) is below 7.35: acidosis • pH 7.0 – 7.35 is physiological acidosis • What components affect the acid base? • H+ blood buffers • CO2 lactic acid

8. What are Blood buffers? • 1 or 2 molecules that prevent dramatic changes in hydrogen ions by binding to H+ when the pH drops to increase the pH • 3 major chemical buffers • Bicarbonate • Phosphate • Protein Buffer systems

9. Bicarbonate buffer system • Carbonic acid (H2CO3) & Salt yielding NaHCO3 (Sodium Bicarbonate) • Carbonic acid is a weak acid & does not dissociate in a neutral or acidic environment • Hydrochloric acid is stronger & bicarb has to “buffer” it; with the presence of carbonic acid, the pH will only be slightly lowered • A stronger base will allow the carbonic acid to dissociate & lower the pH significantly • Usually 20 parts NaH2CO3 to 1 Carbonic acid • Excreted & regulated by the kidneys

10. Respiratory contribution • Carbon Dioxide enters the blood from the tissue cells as Bicarbonate ion (HCO3-) • Depending on the amount of CO2 will determine if it is converted to Carbonic acid (H2CO3) or H+ + HCO3- • In healthy people, CO2 is expelled at the same rate that it is formed in the cell; when this happens the H+ ions are tied up in water & can not raise the pH of blood

11. When CO2 accumulates in the blood, more H+ are released in the blood by metabolism • The higher level of CO2 & H+ (respiratory acidosis) trigger the brain to tell the lungs to breathe deeper & faster to exhale the CO2 & decrease H+ • The higher the pH (respiratory alkalosis) the respiratory center in the brain is depressed to slow the RR & depth to accumulate more CO2 & H+ in the blood

12. Respiratory Acidosis • When the pH is less than 7.35 & PaCO2 greater than 45 • Due to inadequate excretion of CO2 from inadequate ventilation • Occur: • Emergency situations • Acute pulmonary edema • Aspiration of a foreign object • Atelectasis • Pneumothorax • Overdosage of sedatives • Severe pneumonia • ARDS

13. Clinical signs • Increased pulse & RR • Increased blood pressure • Mental cloudiness • Feeling of fullness in the head • Clinical findings • pH below 7.35 • PaCO2 greater than 42

14. Medical Management • Improving ventilation • Bronchodialators for infections • Thrombolytics for pulmonary clots

15. Respiratory Alkalosis • pH greater than 7.45 & PaCO2 less than 35 mm Hg • Due to hyperventilation causing excessive CO2 to be blown out • Causes: • Extreme anxiety • Hypoxemia • Gram negative bacteremia

16. S & S • Lightheadedness • Inability to concentrate • Numbness • tinnitus • Assessment • pH greater than 7.45 • PaCO2 is lower than 35

17. Treatment • Slower RR to increase the level of CO2 in blood • Correct the underlying problem

18. Metabolic Acidosis • Low pH & low plasma bicarbonate • Could be either increase in H+ or decrease in Bicarbonate • Peripheral vasodilatation occurs when pH falls below 7 • S & S • HA • Confusion • Drowsiness • Increased RR & depth • N & V • Decreased BP • Cold & clammy skin • dysrhythmia

19. Arterial blood gas is when Bicarbonate levels is less than 22** key sign • pH less than 7.35 • Hyperkalemia may also occur with Metabolic Acidosis (K+ moves out of the cell) • Correction • Hyperventilation to decrease CO2 level • Administer Bicarb with pH lower than 7.1 & bicarb level less than 10

20. Metabolic Alkalosis • High pH due to decrease in H+ or increase level of bicarb • Most common causes: • Vomiting • Gastric suctioning • Other causes: • pyloric stenosis • diuretic therapy that increases K+ excretion • hyperaldosteronism • Cushing’s syndrome

21. S & S • Tingling of fingers & toes • Dizziness • Hypertonic muscles • Hypocalcemia usually coincides with metabolic alkalosis • pH greater than 7.6 may result in hypokalcemia • Lab work • pH greater than 7.45 & Bicarb level greater than 26

22. Correction • Respiratory rate is depressed • Atrial tachycardia • Treatment • Restore normal fluid volume • Possible KCl (replace K+ & Cl-) • Tagamet (to decrease the production of HCl)