acid-base balance.pptx Acid-base balance refers to the balance between input (intake and production) and output (elimination) of hydrogen ion.

Acid-base balance refers to the balance between input (intake and production) and output (elimination) of hydrogen ion. The body is an open system in equilibrium with the alveolar air where the partial pressure of carbon dioxide pCO2 is identical to the carbon dioxide tension in the blood.

1. Acid- Base B alance

2. Specific Learning Objectives At the end of this lecture all students will be able to: Define PH , acid and base. Discuss how the body regulates acid- base balance. Identify the main diagnostic tests used to assess acid- base imbalance. Identify ABG parameters. Differentiate between the respiratory and metabolic imbalances regarding their causes, and clinical manifestations.

3. Definitions  Acids :-are substances that dissociate or l o s e ions.  Bases: -are substances capable of accepting ions.  Buffer :-is substance that reacts with acids & bases to maintain neutral environment of stable PH.  PH :-represent the free hydrogen I o n concentration .

4. Definition of Acid Base balance Acid-base balance refers to the mechanisms, the body uses to keep its fluids close to neutral pH (that is, neither basic nor acidic) so that the body can function normally. Or Equilibrium between the acid and base elements of the blood and body fluids is called as acid base balance.

5. Acid Base balance The normal pH of the blood is maintained in the narrow range of 7.35-7.45 , i.e. slightly alkaline. The pH of intracellular fluid is rather variable. Thus, for erythrocytes the pH is 7.2, while for skeletal muscle, it may be as low as 6.0

6. Conti… Maintenance of blood pH is an important homeostatic mechanism of the body. In normal circumstances, the regulation is so effective that the blood pH varies very little. Changes in blood pH will alter the intracellular pH which, in turn, influence the metabolism e.g. distortion in protein structure, enzyme activity etc. It is estimated that the blood pH compatible to life is 6.8-7.8.

7. Production of acids by the body The metabolism of the body is accompanied by an overall production of acids. These include the volatile acids like carbonic acid (most predominent , about 20,000 mEq /day) or nonvolatile acids (about 80 mEq /day) such as lactic acid, sulfuric acid, phosphoric acid etc. Carbonic acid is formed from the metabolic product CO2; lactic acid is produced in anaerobic metabolism; sulfuric acid is generated from proteins (sulfur containing amino acids);

8. Phosphoric acid is derived from organic phosphates (e.g. phospholipids). All these acids add up H+ ions to the blood. A diet rich in animal proteins results in more acid production by the body that ultimately leads to the excretion of urine which is profoundly acidic.

9. Production of bases by the body The formation of basic compounds in the body, in the normal circumstances, is negligible. Some amount of bicarbonate is generated from the organic acids such as lactate and citrate. A vegetarian diet has a tendency for a net production of bases.

10. This is due to the fact that vegetarian diet produces salts of organic acids such as sodium lactate which can utilize H+ ions produced in the body. For this reason, a vegetarian diet has an alkalizing effect on the body. This is reflected by the excretion of neutral or slightly alkaline urine by these subjects

11. Regulation of acid-base balance The body has three mechanisms to maintain acid-base balance:

12. Blood Buffer A buffer may be defined as a solution of weak acid and its salt with a strong base. The buffer resists the changes in pH by the addition of acid or alkali and the buffering capacity is dependent on the absolute concentration of salt and acid.

13. Conti.. The blood contain 3 buffer systems: The bicarbonate buffer Phosphate buffer Protein buffer

14. The bicarbonate buffer The bicarbonate buffer system works in the blood to maintain the needed pH, or concentration of H+ ions. Blood is composed largely of water, which breaks apart into H+ ions and OH- ions, also known as hydroxide. The hydrogen ions, or H+, are what determine the pH of the blood.

15. Phosphate buffer It is a water-based salt solution containing disodium hydrogen phosphate, sodium chloride and, in some formulations, potassium chloride and potassium dihydrogen phosphate. The buffer helps to maintain a constant pH.

16. Protein buffer Proteins are made up of amino acids, which contain positively charged amino groups and negatively charged carboxyl groups.  The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers.

17. Respiratory regulation of acid- base balance The lungs regulate blood levels of co2 that combine w i t h H2O to form H2CO3 . Chemo receptors in the medulla of the brain sense t h o s e PH changes and vary the rate and depth of breathing to compensate. Breathing faster or deeper(Hyperventilation) Eliminate more co2 leading to increase PH. Slow and shallow breathing(Hypoventilation) Lead to accumulation of co2 decrease PH.

18. Renal regulation of acid-base balance Kidneys make long- term adjustment to PH. They reabsorb acids and bases or excrete them i n t o urine, and can also produce HCO3to replenish lost supply. Such adjustment to PH take the kidneys days to weeks to complete. If the blood contains too much acids or not enough base, the PH drops and the kidneys in response reabsorb NaHCO3 and excrete (H+) leading to normalization of PH.

19. Diagnosis of acid base imbalance 1. Arterial Blood Gases(ABG). 2. Anion gap estimation.

20. ABG parameters  pH [H + ]  PCO 2 Partial pressure CO 2  PO 2 Partial pressure O 2  HCO 3 Bicarbonate  BE Base excess  SaO 2 Oxygen Saturation

21. Normal values Parameters Normal values PH 7.35-7.45 PaCO2 35-45 HCO3 22-26 Pao2 80-100 Sao2 %More than 95 B/E (2 ( -/+

22. Base excess(B/E ) The base excess indicates the amount of excess or insufficient level of bicarbonate in the system. The normal range is –2 to +2 mEq/liter. (A negative base excess indicates a base deficit in the blood).

23. Arterial Blood Gases Interpretation

24. Expected Question Essay / Situation Question Describe acid base balance Short Question Explain characteristic of Describe Types of buffer system Describe Arterial Blood Gases Interpretation