Acidosis And Alkalosis

Acidosis, Respiratory:::

Respiratory acidosis is a process where the arterial partial pressure of carbon dioxide (PaCO2) is elevated above the normal range (greater than 44 mm Hg) leading to a blood pH less than 7.35. Respiratory acidosis results when the level of carbon dioxide (CO2) excreted from the lungs does not match the level of CO2 produced by the body.

Respiratory acidosis may be an acute or chronic process. An acute respiratory acidosis occurs when there is a sudden impairment in the respiratory system that leads to a sharp increase in PaCO2. In contrast, a chronic respiratory acidosis is characterized by a gradual and sustained increase in PaCO2 that produces compensatory physiologic responses.



CO2 + H2O « H2 CO3 « H+ + HCO3


An arterial blood gas (ABG) is diagnostic of a respiratory acidosis.
The serum HCO3- level and pH can be helpful in distinguishing between acute and chronic hypercapnia.
Acute respiratory acidosis
pH decreases 0.08 for every 10-mm Hg increase in PaCO2
HCO3- increases by 1 mEq/L for every 10-mm Hg increase in PaCO2
If PaCO2 increases acutely to 80 mm Hg, pH is 7.12 and HCO3- 28
Chronic respiratory acidosis
pH decreases 0.03 for every 10-mm Hg increase in PaCO2
HCO3- concentration equals 24 mmol/L plus 4 mmol/L for every 10-mm Hg increase in PaCO2 > 40 mm Hg, ± 4 mmol/L
For example, if the PaCO2 is 80 mm Hg, the pH is 7.28 and HCO3- 40 ± 4
The bicarbonate resorption process is very efficient. If a patient with chronic hypercapnia has a pH <7.20, a superimposed acute on chronic respiratory acidosis or concomitant ****************bolic acidosis is most likely occurring as well.




****************bolic Acidosis:::::

****************bolic acidosis is a clinical disturbance characterized by an increase in total body acid. It should be considered a sign of an underlying disease process. Identification of the underlying condition that is causing the acidosis is essential to initiate appropriate therapy.

This chapter discusses the differential diagnosis of ****************bolic acidosis. It also presents a scheme for identifying the underlying cause of acidosis by using laboratory tests that are available to ED physicians. Clinical strategies for treating ****************bolic acidosis are described.


H+ + HCO3- = H2CO3 = CO2 + H20

Blood gas measurement shows evidence of acidemia, and serum electrolytes indicate a low level of bicarbonate. In addition, blood gas measurements may also reflect the degree of respiratory compensation. To determine whether respiratory compensation is adequate, the Winter formula can be applied as follows:


Measured bicarbonate X 1.5 + 8 +/- 2.5 = PCO2


If the PCO2 is significantly higher than the level indicated by the Winter formula, it may indicate that the patient is unable to compensate appropriately by increasing CO2 elimination. This condition may be caused by a depressed mental state or by an airway pathology. This inability to compensate is especially important in patients with diabetic ketoacidosis who may develop cerebral edema and altered mental status.




Respiratory Alkalosis

Respiratory alkalosis is a clinical disturbance due to alveolar hyperventilation. Alveolar hyperventilation leads to a decreased PaCO2 (hypocapnia). In turn, the decrease in PaCO2 increases the ratio of bicarbonate concentration (HCO3-) to PaCO2 and increases pH. Hypocapnia develops when the lungs remove more carbon dioxide than is produced in the tissues. Respiratory alkalosis can be acute or chronic. In acute respiratory alkalosis, the PaCO2 is below the lower limit of normal and the serum is alkalemic. In chronic respiratory alkalosis, the PaCO2 is below the lower limit of normal, but pH is normal or near normal because of renal compensation.

Respiratory alkalosis is the most common acid-base abnormality observed in patients who are critically ill. It is associated with numerous illnesses and is a common finding in patients undergoing mechanical ventilation. Many cardiac and pulmonary disorders can present with respiratory alkalosis as an early or intermediate finding. When respiratory alkalosis is present, the cause may be minor but more serious disease processes should also be considered in the differential diagnosis.


Arterial blood gas
Alkalemia is documented by the presence of an increased pH (>7.44) on arterial blood gas determinations.
The presence of a decreased PaCO2 (<36 mm Hg) indicates a respiratory etiology of the alkalemia.




Alkalosis, ****************bolic

****************bolic alkalosis is an acid-base disturbance caused by an elevation in plasma bicarbonate (HCO3) concentration. This condition is not a disease; it is a sign or state encountered in certain disease processes. Although ****************bolic alkalosis may not be referred to as often as ****************bolic acidosis, it is the most common acid-base abnormality in hospitalized adults.

The 2 types of ****************bolic alkalosis (ie, chloride-responsive, chloride-resistant) are classified based upon the amount of chloride in the urine.

Chloride-responsive ****************bolic alkalosis involves urine chloride levels less than 10 mEq/L, and it is characterized by decreased extracellular fluid (ECF) volume and low serum chloride such as occurs with vomiting. This type responds to administration of chloride salt.

Chloride-resistant ****************bolic alkalosis involves urine chloride levels more than 20 mEq/L, and it is characterized by increased ECF volume. As the **************** implies, this type resists administration of chloride salt. Primary aldosteronism is an example of chloride-resistant ****************bolic alkalosis.



Arterial blood gas (ABG) measurement shows elevated pH with high HCO3 level. With compensation, PCO2 may also be near the reference range or elevated.


SOMETIMES WE GET MIXED PICTURE OF ****************BOLIC ASIDOSIS COMPONSATED BY RESPIRATORY ALKALOSIS OR VICE VERSA OF ANY MIXTURE??????????????

TO DIFFERENTIATE WHICH IS WHICH WE SHOULD LOOK TO (SBE)
WHIC IS NORMALY BETWEEN -2 TO +2
IF >-2 THAT IS PRIMARY ****************BOLIC ACIDOSIS
IF>+2 THAT IS PRIMARY ****************BOLIC ALKALOSIS

IF THE RANGE IS WITHEN NORMAL THAT MEANS IT IS RESPIRATORY OF ORIGIN AND COMPONSATED BY ****************BOLIC>>>