1. Fluid and Electrolyte Imbalance
Lecture 3
4/24/2017

2. Acid Base Disturbance
Plasma pH is an indicator of hydrogen ions concentration
The increase in hydrogen in the blood make it acid while the lower hydrogen make it alkaline
Normal plasma pH is
Lower pH means more acidity
There is 3 important factors that control the pH of blood hydrogen ion H+, bicarbonate ions HCO3- and carbon dioxide CO2.
H+ , HCO3- and CO2 are routinely measured in Arterial Blood Gas sample (ABG)
The more HCO3- in the blood the more the alkalinity( normal value 22-26mEq/L)
The more CO2 the more the acidity (normal value 35-45mmHg)
4/24/2017

3. Kidney and lung has the primary role in maintaining pH in the blood
Kidney is responsible for the 24 hrs regulation of pH while the lung act mainly in the emergency situation
Kidney regulate pH directly through bicarbonate and hydrogen ions .
When the blood is acidic the kidney produce more bicarbonate and increase excretion of hydrogen ions . The opposite happens in case of alkalosis
The lung helps in mainatinence of pH through CO2 control
When the blood is acidic the lung increase the rate and depth of breathing which lead to wash off CO2 .
When the blood is alkaline the lung decrease the rate and depth of breathing which entails more CO2 retintion in the blood
Change in bicarbonate concentration in the blood reflect a metabolic disorder while the change in CO2 reflects a respiratory disorder . Change in both reflect mixed metabolic and respira.tory disorder
4/24/2017

4. Metabolic Acidosis
A clinical disturbance that is characterized by low pH ( less than 7.35) low bicarbonate ( less than 22mEq/L and low hydrogen concentration.
Clinical manifestations
Increase rate and depth of breathing
Peripheral vasodilation which lead to hypotension
Decrease cardiac out put
Neurologic sign such as headache confusion
Causes: renal failure, loss of bicarbonate as in diarrhea, vomiting , lower intestinal fistula , excessive administration of chloride, hyperkalemia
4/24/2017

5. Metabolic Acidosis Medical management
Adminsiter bicarbonate when pH below 7.1
Ringer lactate ( sodium lactate): metabolized into sodium bicarbonate inside the body
correct hyperkalemia: Potassium move from inside the cell to the blood in exchange for hydrogen ions which increase acidity of the blood.
4/24/2017

6. Metabolic Alkalosis
Clinical disturbance characterized by high pH ( higher than 7.45) and high bicarbonate (higher than 26mEq/L)
Causes
The most common cause is vomiting or nasogastric tube suction ( gastric secretion is pH is 1to3 and rich in hydrogen and chloride).
Condition of hypokalemia
4/24/2017

7. Metabolic Alkalosis Clinical manifestations
Usually related to decrease calcium ionization( calcium need acid environment to be chemically active) .
Symptoms of hypocalcaemia develop such as tingling of fingers, respiratory depression
Management
Administration of chloride( increase bicarbonate excretion)
Administer potassium in case of hypokalemia
4/24/2017

8. Respiratory acidosis
A clinical disturbance charcterized by low pH( less than 7.35), and CO2 higher than 45mmHg.
Causes
All condition that increase CO2 in the blood such as respiratory diseases atelectasis, pneumonia…..)
4/24/2017

9. Respiratory acidosis Clinical manifestations
Increase rate and depth of breathing
Signs of vasodilation in brain and peripheral as a result of increase CO2 such as increase in intracranial pressure (ICP)
Cardiac arrhythmia
Hyperkalemia ( potassium increase as exchange with hydrogen ions)
Medical management
Manage respiratory disease, improve oxygenation
4/24/2017

10. Respiratory alkalosis
Clinical disturbance characterized by high pH greater than 7.45 and CO2 less than 35mmHg
Causes
Main cause is Hyperventilation which cause excessive blow off ( wash off ) for CO2
Other causes include salicylate toxicity ( aspirin)
Clinical manifestations
Signs of decrease cerebral blood flow such as inability to concentrate, cardiac arrhythmia
4/24/2017

11. Respiratory alkalosis
Medical management
Treatment of the underlying cause
4/24/2017