Acid-Base Balance

Acid

A substance that can yield hydrogen or hydronium ions when dissolved in water.

Base

A substance that can yield hydroxyl ions when dissolved in water.

lower than 6.8 pH

Greater than 8.0 pH

Arterial blood pH that is incompatible to life?

• Acid taken with food (exogenous sources)

• Carbonic acid formation taking place in the

  cell and plasma (constant)

• Inorganic acids produced during the

  breakdown of nutrients

• Organic acids resulting from intermediary

  metabolism

Sources of Hydrogen ion in the body

Chemical buffers

First line of defense against pH changes, including the bicarbonate carbonic acid system as the major chemical buffer in the blood.

only takes second to minute after abnormality to react.

Respiratory mechanism

Second line of defense against pH changes and second to respond, involving respiratory mechanism and ventilation.

Takes minutes to hours after pH change occurs.

Renal mechanism

Third line of defense against pH changes, involving the kidneys through reabsorption.

Takes hours to days after pH change to activate.

CO2

Regulated by the lungs thru ventilation (respiration).

Bicarbonate

controlled by the kidneys

Carbonic Anhydrase

An enzyme that catalyze and produce H2CO3.

TRUE

True or False

CO2 and Hydrogen ions are directly proportional in the Lungs?

Level of hydrogen ion determination in the body.

the rate of removal of carbon dioxide would determine the what?

CO2 would accumulate in the plasma and more carbonic acid will be produced as well as hydrogen ion concentration.

Hypoventilation or Slow removal of CO2 of Lungs / no removal will result to

Decrease Hydrogen ion concentration and fast removal of CO2 leading to decrease H+

Hyperventilation or Rapid/fast elimination of CO2 by the lungs will result to

FALSE

TRUE OR FALSE

pH and H+ are directly proportional.

Kidneys

• Excrete Considerable Amounts of Acid and Base for Acid-Base Regulation.

• Reclaim bicarbonate from the glomerular filtrate

• Responsible for excreting excess acid or excess base

50-100 mmol/L

Kidneys excrete _________ of Acid per day.

26-30 mmol/L

Kidneys reabsorb ________ of HCO3

• IV infusion (Lactate, Acetate, and HCO3)

• When lactate and acetate are infused intravenously, they are transformed into HCO3.

Increase HCO3 in

• Diuretics

• Reduced Reabsorption

• Chronic neophritis

Decrease HCO3 in

Henderson-Hasselbach Equation

Expresses acid-base balance relationship and relates pH to the dissociation properties of weak acids.

20:1

What ratio should be maintained to determine if there is disturbance in 7.4 pH?

pH, pCO2, HCO3, pO2 - key factors in evaluating acid-base balance.

Parameters of Interest

Bicarbonate and carbonic acid, plasma proteins, hemoglobin, and inorganic phosphate - involved in maintaining pH balance.

Blood buffers

7.40 pH

Optimum Value For Arterial Blood

7.35 - 7.45 pH

normal value of pH

35-45 mmHg

Normal pCO2

<35 mmHg pCO2

Respiratory Alkalosis is seen in

>45 mmHg pCO2

Respiratory Acidosis is seen in

pCO2 (partial CO2)

Index or efficiency of gas exchange.

Heparin, Barbiturates, Morphine Or Alcohol

It can Have An Increasingly Marked Effect On Measured pCO2.

19- 24 mmol/L

Arterial blood total CO2

22-26 mmol/L

Venous blood total CO2

21-28 mEq/L

Normal HCO3

<21 mEq/L HCO3

Metabolic Acidosis is seen in

>28 mEq/L HCO3

Metabolic Alkalosis is seen in

pO2

Reflect the availability of the gas in the blood.

The degree of association or dissociation of oxygen with hemoglobin is determined.

81-100 mmHg

Normal pO2

< 81 mmHg

Hypoxemia is seen in

Mild Hypoxemia

61-80 mmHg pO2

Moderate Hypoxemia

41-60 mmHg pO2

Severe Hypoxemia

40 mmHg or Less pO2

TRUE

TRUE OR FALSE

Healthy persons living at high altitudes will show a lower range of arterial pressure.

Metabolic Acidosis

• A condition marked by marked Low pH, Low pCO2, and Low HCO3-

• caused by Bicarbonate Deficiency

• Production Of Excess Amount Of Acid

• DKA - Diabetic Ketoacidosis

• Lactic Acidosis

• Renal Failure

• Diarrhea

• (+) Hyperkalemia And

  Hyperchloremia

• Increase breathing rate

Metabolic Alkalosis

• A condition marked by high pH, high pCO2, and high HCO3- levels in the blood

• typically caused by an excess of bicarbonate due to factors like vomiting or hypokalemia & hypochloridemia.

• seen in decrease Breathing rate.

Respiratory Acidosis

A state where there are Low pH, high HCO3-, and high pCO2 levels in the blood.

Usually resulting from excessive carbon dioxide accumulation seen in conditions of

• COPD

• Druug overdose

• Myasthenia Gravis

• CNS Dse

• Pneumonia

Kidneys retain HCO3 because of increased pCO2

Respiratory Alkalosis

An abnormal condition characterized by high pH, low pCO2, and low HCO3- levels in the blood

Often due to excessive carbon dioxide loss seen in situations of

• Anxiety

• Severe pain

• Aspirin Overdose

• Hepatic Cirrhosis

• Gram-Negative Sepsis

Decreased Reabsorption of HCO3 causing Acidification and Hypokalemia.