Acid-base Balance:- Part 1 A – Introduction to the Acid-Base Balance

Acid-base Balance

What sample is needed for acid-base studies?

1. pH and blood gases preferably should be done on arterial blood.
2. Venous blood is not suitable for judging oxygenation.
   1. Venous blood can be used to check acid-base status.
3. Collect blood for electrolytes at the same time.
   1. Blood gases, electrolytes, and pH should be performed on blood specimens obtained at the same time because of the variation in labile blood gases.

What are the Precautions for acid-base studies?

1. The blood sample should be ice-packed immediately.
   1. A delay of a few minutes will give false values.

How will you define acid-base balance?

1. Acid-base balance refers to the regulation of the pH level in the blood.
2. Its main purpose is to maintain homeostasis.
3. The ideal pH range for the body is 7.35 to 7.45 in the arterial blood.
4. An acid-base balance is essential for life.

What is the mechanism of Acid-base balance and electrolyte regulation?

1. Electrolytes in different compartments are present in our body.
2. Our body has three compartments, and these communicate with each other.
   1. Intracellular fluid.
   2. Extracellular fluid (Vascular fluid containing blood and lymph).
   3. Interstitial fluid.
3. Electrolytes and fluids continuously move among these compartments to maintain:
   1. Homeostasis.
   2. Cell metabolism.
   3. Organ functions.

Acid-base compartments

4. The body maintains an acid-base balance through the following three systems.
   1. Buffer system. The bicarbonate, protein, and phosphate buffer systems respond immediately.
   2. Respiratory system. Lungs regulate CO2.
   3. Renal system. Kidneys regulate HCO3^– and H⁺ ions.
5. The regulation of intracellular and extracellular electrolyte concentration depends on the following factors:
   1. There is a balance between the intake of substances in a diet containing electrolytes and the electrolytes’ output in feces, urine, and sweating.
   2. It also depends upon the transport of fluids and electrolytes between ECF and ICF.
6. Physiological changes in the concentration of H⁺ ions in the blood lead to acid-base balance

What factors are important for acid-base balance?

1. This regulation of the extracellular fluid environment involves the ratio of acid to base, measured clinically as pH.
   1. Physiologically, all positively charged ions are called acids, and all negatively charged ions are called bases.

Acid-base definition

What is the distribution of various anions/cations in body fluids?

What are the possibilities of an acid-base imbalance?

How will you discuss Acidosis (Acidemia)?

1. A systemic increase in the concentration of H+ ions is called acidosis (acidemia).

Acid-base acidemia

2. Metabolic acidemia:
   1. Due to metabolic disorders, there is an excess accumulation of acids, such as lactic acidosis, ketoacidosis, and organic acids.
3. Respiratory academia:
   1. It occurs when there is excess CO2, leading to carbonic acid.
   2. It occurs in chronic obstructive pulmonary disease, pneumonia, and severe asthma.

How will you discuss Alkalosis (Alkalemia)?

1. A systemic decrease in the H⁺ ions is called alkalosis (alkalemia).

Acid-base alkalemia

2. Metabolic alkalemia:
   1. It occurs when there is an excess of HCO3^/ or a decrease in non-carbonic acid.
   2. It may be seen in severe vomiting.
   3. Excessive intake of alkaline substances.
   4. In some kidney diseases.
3. Respiratory alkalemia:
   1. There is a decrease in the CO2 in the blood, leading to a decrease in carbonic acid.
   2. It is seen in hyperventilation, leading to excessive elimination of CO2.
4. The body must regulate the acid-base balance within a narrow range to function normally.
   1. A very slight change in the pH will affect the body.
   2. A slight change in the H+ ions can change the cells and tissues.

• The pH range is very narrow for normal body functions and needs to be maintained within these limits.

What is the significance of pH in our lives?

What is the pH of arterial/venous/blood and body fluids?

What is the Importance of H⁺ ions?

1. To maintain the integrity of the membrane.
2. Speed of the metabolic reactions.
3. Any change in the pH will lead to more harmful effects than other diseases.
4. The symbol pH represents the power of H⁺.
5. When the pH changes by one unit, like 7.0 to 6.0, = [H+] [H+] = the concentration of H+ ions changes 10-fold.

What is the mechanism of body acid formation?

1. Metabolism of proteins.
2. Metabolism of Carbohydrates.
3. Metabolism of fats.
4. This must be balanced by the number of basic substances in the body to maintain the normal pH.
   1. The lungs, kidneys, and bones are the major organs involved in regulating the acid-base balance.

What are the types of Body acids?

1. Volatile acids:
   1. Carbonic acid (H2CO₃) is a weak acid that does not easily release the H⁺ ions.
   2. The presence of carbonic anhydrase enzyme can eliminate CO2 gas and water H2O.
   3. CO2 is eliminated through the lungs.
2. Nonvolatile acids:
   1. These are sulfuric acid, phosphoric acid, and other organic acids eliminated through the kidneys.
   2. These are strong acids and readily give up their H⁺ ions.
   3. Nonvolatile acids are secreted into the urine by the renal tubules.
   4. These acids are about 150 meq/L of H⁺ ions per day or about one meq/kg body weight.

How will you discuss in detail the buffer systems of the acid-base balance?

• The buffer systems become active in response to changes in the body’s pH as an acid-base balance.

What are the functions of the buffer system?

1. Prevent significant changes in pH.
2. A buffer can absorb the excess of the H⁺ ions (acid).
3. The buffer system can absorb OH^– ions and hydroxide (base).
4. The buffer system is present in the intracellular fluid (ICF) and extracellular fluid (ECF).
5. The most common buffer systems are:
   1. Carbonic acid-bicarbonate system.
   2. Hemoglobin-oxyhemoglobin system.
   3. Phosphate and protein are the most important intracellular buffers (ICF).

How will you summarize the different buffer systems in acid-base balance?

How will you discuss the Renal buffering system?

1. The distle tubule of the kidneys regulates acid-base balance by secreting the H⁺ ions in the urine and reabsorbing the HCO3^–.
2. Dibasic phosphate (HPO4^—) and ammonia (NH3) are two important renal buffers.
3. The renal buffering of H⁺ ions requires CO2 and water (H2O) to form H₂CO3.
4. The enzyme carbonic anhydrase catalyzes the reaction.
5. H⁺ ions are secreted from the tubular cells and buffer in the lumen by PO4^— and NH3 = H2PO^–3 + NH4⁺.
6. The rest of HCO3^– is reabsorbed.

Acid-base balance and role of kidneys

7. If a respiratory Disease causes acidosis or alkalosis, the kidney becomes active and changes H⁺ and HCO3^– ions to return the pH to normal.
   1. Renal compensation starts in hours to days after respiratory alteration in the pH.
   2. There is a delay, but the renal buffer system is powerful.
8. In academia (acidosis): The kidney excretes an excess of the H⁺ ions, and these may combine with PO4 (phosphate) or NH3 (ammonia) to form titratable acids in the urine.
   1. The net outcome is raising the HCO3- ions’ concentration in the ECF and restoring the acid-base balance.
9. In alkalemia (alkalosis): kidneys excrete HCO3^–  ions, usually with Na⁺ ions.
   1. The net result is decreased concentration of HCO3- ions in the ECF, and the acid-base balance is restored.

How will you discuss the carbonic acid-bicarbonate buffering system?

1. This buffer system operates both in the lungs and kidneys.
2. This is the major extracellular buffer system.
3. Lungs can decrease the carbonic acid by blowing out the CO2 and leaving water behind.
4. Kidneys can reabsorb HCO3^– or regenerate new HCO3^– from CO2 and water.
5. Normal bicarbonate (24 meq/L) and normal carbonic acid (1.2 meq/L) produce a 20:1 relation and maintain a pH of 7.4.
6. Both systems are very efficient because:
   1. HCO3^– is easily reabsorbed or regenerated by the kidneys.
   2. The lungs adjust acid concentration.
7. Compensation for the pH is done as follows:
   1. The respiratory system compensates for pH by decreasing or increasing CO2 by changing the respiration rate.
   2. The renal system produces more acidic or alkaline urine.

How will you discuss the protein buffering system?

1. Hemoglobin (Hb) is the best intracellular buffer system, and it combines with H⁺ and forms HHb and CO2, forming the HHbCO2 complex.
2. When Hb combines with H+ ions, it becomes a weak acid.
3. Venous blood Hb is a better buffer system than arterial blood Hb.

Acid-base control

How will you discuss the pulmonary role in the acid-base balance?

1. In case of acidosis or alkalosis resulting from metabolic or renal diseases, the respiratory system regulates the respiratory rate to restore the pH to normal.
2. In acidemia (acidosis), there is an increased respiratory rate and depth to eliminate CO2.
3. In alkalemia (alkalosis), there is a decreased respiratory rate and depth to retain the CO2.

What are the various Buffer Systems and their role in the acid-base system?

What are various organs’ roles as a buffer and in acid-base balance?

What is the role of various anions in the acid-base balance?

What are the Panic values?

What are the parameters needed for the acid-base balance?

Questions and answers: