ACID BASE
MAINTENANCE
PREPARED BY MR. ABHIJIT DAS
pH:
pH is a measure of acidity or alkalinity of a
solution. It stands for "potential of hydrogen." The pH scale ranges
from 0 to 14:
- A
pH less than 7 indicates an acidic solution.
- A
pH of 7 indicates a neutral solution.
- A
pH greater than 7 indicates an alkaline (or basic) solution.
Normal value:
- Blood
pH: 7.35 - 7.45
- Stomach
pH: 1.5 - 3.5
- Urine
pH: 4.5 - 8.0
- Saliva
pH: 6.2 - 7.6
REGULATION OF BLOOD PH:
The body has several mechanisms to regulate pH and
maintain it within the narrow range of 7.35 to 7.45 in the blood. These
mechanisms include:
1.
Blood Buffers:
·
Bicarbonate Buffer System:
This is the primary buffer system in the blood. It consists of bicarbonate (HCO3-) and carbonic acid (H2CO3). When
there's an excess of acid, bicarbonate acts as a
base to neutralize it, and when there's an excess of base, carbonic acid acts as an acid to neutralize it.
·
Protein Buffer System:
Proteins in the blood, particularly hemoglobin and
albumin, can act as buffers by accepting or
donating hydrogen ions (H+).
2.
Respiratory Regulation:
·
CO2 and Breathing Rate:
The respiratory system helps regulate pH by controlling the levels of carbon
dioxide (CO2) in the blood. When CO2
levels increase, the body increases the breathing rate to expel more CO2, which
helps decrease the acidity (increase pH). Conversely, when CO2 levels decrease, breathing rate
decreases, allowing CO2 to accumulate and increase acidity (decrease
pH).
3.
Renal (Kidney) Regulation:
·
Acid-Base Balance:
The kidneys play a crucial role in maintaining pH by
selectively excreting or reabsorbing bicarbonate ions (HCO3-) and
hydrogen ions (H+).
ABG (ARTERIAL BLOOD GAS):
ABG stands for Arterial Blood Gas. It's a test that
measures the levels of oxygen, carbon dioxide, and pH in your blood. This test
is used to assess how well your lungs and kidneys are functioning.
Normal values for arterial blood gas (ABG) tests:
- pH:
7.35 to 7.45
- Partial
pressure of oxygen (PaO2): 75 to 100 mmHg
- Partial
pressure of carbon dioxide (PaCO2): 35 to 45 mmHg
- Bicarbonate
(HCO3-): 22 to 28 mEq/L
- Oxygen
saturation (SaO2): 95% to 100%
ACID BASE DISORDERS:
There are four primary types of acid-base disorders:
1.
Respiratory Acidosis: Caused by
hypoventilation, where the lungs can't remove enough carbon dioxide, leading to
increased levels of carbonic acid in the blood.
2.
Respiratory Alkalosis: Due to
hyperventilation, leading to decreased carbon dioxide levels and increased pH.
3.
Metabolic Acidosis:
Causes:
Ø Excessive
production of acids (e.g., diabetic ketoacidosis)
Ø Loss
of bicarbonate (e.g., diarrhea)
Ø Inability
of kidneys to excrete acid (e.g., renal failure)
4.
Metabolic Alkalosis:
Causes:
Ø Loss
of acids (e.g., vomiting, diuretics)
Ø Excessive
intake of alkaline substances (e.g., antacids)