Acid-base imbalances Flashcards
What is the linkage between hydrogen levels and pH?
When the H+ levels are high the pH will decrease
When the H+ levels are low the pH will increase
Alteration in pH below or above 7.35 - 7.45 can cause?
Acidosis - pH below 7.35
Alkalosis - pH above 7.45
What is a common end-product in catabolic processes of nutrients?
Carbonic acid
How is carbonic acid formed?
By reaction of CO2 + H20 —– carbonic anhydrase—-> carbonic acid, H2CO3
- The concentration of CO2 is regulated by the lungs
The H2CO3 can spontaneously dissociate into HCO3- and H+ ions
- The concentration of HCO3- is regulated by the kidneys
CO2 + H20 —– carbonic anhydrase—-> H2CO3 HCO3- + H+
Acid are generally classified into 2 types of acids, which?
Volatile acids
- Weak acids
- Can be eliminated as a gas; CO2
Non-volatile acids
- Strong acids
- Can NOT be eliminated as CO2
What is the principal gas of volatile acids?
Carbonic acid
What is typical for Non-volatile acids?
- Strong acids from metabolism of proteins, carbohydrates and fats
- Can react immediately with plasma buffers (bicarbonate) and form
- Sulfuric acid: Formed from sulphur containing acids as Methionine, Cystine, Cysteine
- Phosphoric acid: Produced from hydrolysis of phosphodiesters
What is typical for bases?
Binding to H+ ions and appear in blood as HCO3-
Formed during intake of feed
What are regulatory mechanisms for acid-base imbalances?
- IC/EC chemical buffers
- Lungs (Resp. adjustment of CO2 concentration)
- Kidneys ( Excretion of acids and regeneration of buffer systems)
Complete restoration of acid-base balance takes how long?
Few hours or even several weeks
How quickly does buffers and respiratory systems act and for prevention of what?
Act within minutes in order to prevent large deviation of H+ ions
What does the Henderson-Hasselbach equation tell?
That the pH of a solution containing buffer systems is termed by the ratio of BASES to ACIDS: HCO3 / H2CO3
What are the Principle buffer systems ?
- Bicarbonate buffers
- Plasma protein buffers
- Phosphate buffers
- Haemoglobin buffers
What are the Major buffer systems in body?
- Blood plasma
- RBC
- Interstitial fluid
- IC fluid
- Mineral matrix of bone
What is the Isohydric principle?
That each base of each buffer pair will bind to H+ ions
As a result, addition of acid or base to a solution containing several buffers will result in a change in the rations of all the buffer pairs
OR
The phenomenon whereby multiple acid/base pairs in solution will be in equilibrium with one another, tied together by their common reagent: the hydrogen ion and hence, the pH of solution. That is, when several buffers are present together in the same solution, they are all exposed to the same hydrogen ion activity.
Which buffer system is the most important in the body?
The bicarbonate buffer system
Which principal buffer system is the most important and contain which buffer pair?
- The bicarbonate buffer system
- Carbonic acid + Bicarbonate buffer pair makes up the system
The respiratory and renal systems also play major roles in acid-base homeostasis by removing CO2 and hydrogen ions, respectively, from the body
Describe the function / process of bicarbonate buffer system
Function both in LUNGS and KIDNEYS.
CO2 + H2O H2CO3
H2CO3 H+ + HCO3-
- The acid in this process = CO2 = carbonic anhydrate = not a true acid
- H2CO3 = carbonic acid = a weak acid that quickly ionizes to form H+ ions and HCO3-
- The carbonic anhydrase enzyme catalyses formation of carbonic acid from CO2 + H2O.
This acid then dissociates and the H+ ions is then mainly buffered by Hb by HCO3- and leaving the RBC to exchange for Cl- ions for entering the plasma.
Why is a part of the Bicarbonate buffering happening by Hb, protein and Phosphate instead?
Since the HCO3- (bicarbonate) itself is unable to buffer the formed H2CO3.
Therefore the rest of the buffering is happening within the RBC by Hb, protein and phosphate
What is a very good intracellular buffer system and why?
Haemoglobin buffer system
Due to its ability to bind to H+ ions and CO2
Which blood type is the best buffer ?
Unsaturated Hb (venous blood) is a better buffer than Hb saturated with O2 (arterial blood) due to the O2 effect on pK
Which buffer systems are good IC systems?
- Phosphate buffer system
- Protein buffer system
- Haemoglobin buffer system
Which buffer system play an imp role in acid-base balance and urinary buffering?
The phosphate buffer
Imp. for excretion in tubular lumen
What is the most effective extracellular buffer?
The bicarbonate buffer system
Which buffer system acts within the RBC?
- Haemoglobin buffer system
What is the role of bones in buffering?
As pH decreases of EC fluid the K+, Ca2+ andMg2+ of the bones can be released and be replaced by H+ ions.
Typical for Chronic acidosis
Which are the major buffer systems for acid-base balance / homeostasis?
- Bicarbonate buffer system
- Respiratory system
- Renal system
(These two also play major roles in acid-base homeostasis by removing CO2 and hydrogen ions, respectively, from the body)
What is the central control of alveolar ventilation?
- Central control which is of chemical origin: Central chemoreceptors
- Peripheral chemical control: Peripheral chemoreceptors
Central chemoreceptors senses the changes of pCO2
Peripheral chemoreceptors sense the changes of pO2
Lungs / respiratory system is able to control the partical pressure of CO2 and is a vital regulator of acid-base balance
Respiration is under control of?
Nervous and Chemical control
The Nervous control of respiration includes which 3 centers?
Inspiratory, exiratory and Pneumotaxic centre
The kidneys play an important role in?
- Conservation of filtered HCO3-
- Excretion of H+ ions by formation of Titratable acid
- Formation of NH4+
The kidneys main role in the acid base balance is the excretion of acid and the regeneration of buffer systems within the body.
What are the compensatory mechanisms/ maintenance of acid-base balance?
- Chemical buffering
- Rapid/Respiratory compensation
- (Renal) Correction
What is the first compensation that is achieved during acid-base deviation?
Chemical buffering
What does it mean “Immediate chemical buffering” ?
That all the buffer systems of EC can react at the same time.
Having an interrelationship = Isohydric principle
What is the most common disorder of acid-base in all animals?
Metabolic acidosis
What is metabolic acidosis?
A condition where there is too much acid in the body fluids
Due to:
- Loss of base (HCO3-) from ECF
- Intake of strong acid or too much acid (H+) to ECF
Causes pH of EC fluid to decrease and by the isohydric principle it also leads to a drop in all buffer pairs of ECF and RBC
Renal correction is responsible for increasing pH of ECF by urinary excretion of H+ ions and HCO3- regeneration
What are the compensatory mechanism of acid-base imbalances?
- Chemical buffering
- Respiratory compensation
- Renal correction
Causes an electrolyte shift:
- A higher intake of H+ ions into the cell and K+ efflux leads to H+ buffered intracellularly and Hyperkalemia
- A higher intake of K+ ions into the cell and H+ efflux have a tendency to correct alkalosis but cause Hypokalemia
Hypercalcinuria and Hyperkalemia are often associated with?
Metabolic acidosis
What are common causes for Metabolic acidosis?
- Increased production of acids or intake of acids
- Monday morning disease
- Decrease in renal excretion of H+
- Body loss of HCO3- from GIT
What is Ileus?
Prolonged transit time of digesta from pylorus to anus
What are common imbalances in Diabetes Mellitus?
Ketoacidosis
Hyperglycemia
Dehydration
What is metabolic alkalosis?
- Addition / gain of base (HCO3-) to ECF
- Loss of acid (H+) from ECF
causing an increase in pH
Alveolar hypoventilation is typical for?
Metabolic alkalosis.
As respiratory/rapid compensation mechanism
- Causes a decrease of pCO2 followed by Hypoxia since we can’t stop breathing for too long time and therefore respiratory compensation isn’t very efficient
= Incomplete compensation!
Renal correction of metabolic alkalosis consist of?
- Decreased secretion of H+ ions
- Larger secretion of HCO3- (low excretion even if it is higher than usual)
This leads to an decrease of ECF pH
What are common causes for Metabolic alkalosis?
- Loss of H+ ions from ECF
- Intake of alkalinized substances
- Increased retention of bases and Na+ in the body
- Primary / Secondary hyperaldersteronism
- Diuretics
- Loss or depletion of potassium from the body in Hypokalemia
Overdose of NaHCO3- and CaCO3, Increased retention of bases and Na+ in the body, loss of K+ from the body are common conditions that result in?
Metabolic alkalosis
Persistent vomiting of both gastric and intestinal content may result in
Metabolic acidosis
What is respiratory acidosis?
- Low ventilation leads to hypercapnia: Gain of CO2 , retention of CO2 and more carbonic acid (H2CO3)
- Serum pH decreases
Can be:
- Acute –> Hypoxia
- Chronic –> Hypoventilation due to e.g. overdosage of anaesthetic
Common causes of acute respiratory acidosis are
- Depression of resp
- Trauma
- Drugs
- Brain damage,
- Obstruction to gas movement / diffusion within the lung: Foreign body, -
- Pnemonia
- Pulmunary edema
- Hypercapnia in inspired air
Chronic respiratory acidosis disorders?
Neuro-mascular disorders, paralysis of diaphragm
Hyperventilation, reduce of CO2 (hypocapnia). alkalic pH (due to low H+) is typical for?
Respiratory alkalosis
Alkalic pH = Increased pH of blood
Respiratory alkalosis is commonly caused due to?
Central and Peripheral hyperventilation: Excessive ventilation
Central hyperventilation:
- Intoxication
- Excitement, fear, stress,
- Hyperthermia/ Fever
- Encephalitis, meningitis, cerebral edema.
Peripheral hyperventilation:
- Pulmonary disease
- Hypoxia, Anemia
- Bacterial sepsis
Confusion, paresthesia, coma and deep, rapid respiration is typical clinical signs for?
Acute respiratory alkalosis
In chronic respiratory alkalosis typical clinical signs are
- Hyperventilation leading to Hypokalemia.
- Increased irritability, seizures
How can secondary acid base de-arrangements occur?
When K+ imbalances occur already it can lead to further fluid imbalances:
- Overhydration leading to Acidosis
- Dehydration leading to Alkalosis
