Acid Base Balance Flashcards
(42 cards)
What metabolic processes produce acids?
Protein/ phospholipid metabolism, CO2 from carbohydrate metabolism
What is acid buffered by?
HCO3-, haemoglobin, plasma proteins
How is acid excreted?
Lungs & kidney
Why is acid-base such a big deal?
Most enzyme systems in the body will function optimally within a narrow range of pH (7.4- homeostasis- optimal)
When does an acid-base imbalance occur?
When there is a change in the production or excretion of a specific acid or base. e.g. lack of insulin in diabetic animals can lead to being unable to use glucose for energy. Instead they use fatty acids. These acids can build up and lead to a drop in the serum pH of the patient. This is diabetic ketoacidosis
What happens in chronic renal failure to cause an imbalance?
Kidney is no longer able to retain bicarbonate, which is a base, increased loss of bicarbonate in the urine causes an acidosis in the body
What is an acid?
Simply a molecule that can donate a proton; H+ is the most basic acid itself
What significantly impacts H+’s concentration?
Na+, K+, Ca++ (cation concentrations), etc.
What significantly impacts HCO3-‘s concentration?
Cl-, phosphates, sufates, etc. (anions)
The body must always remain electroneutral. Therefore, electroneutrality takes precedence over what?
Acid-base balance
What is the chain reaction when a patient vomits gastric fluid?
Lose HCl- –> H+ and Cl- and H2O–> loss of H+ creates mild alkalotic environment–> Na+ is retained to help water retention–> Na+ or K+ is retained in place of lost H+ –> Less Cl- now availalble, HCO3- is retained in order to maintain electroneutrality–> Increase in bicarbonate will cause the alkalosis to become much more severe
What is the first strategy for balancing acid-base?
Buffering
What are buffers?
Proteins or ions that can take up or release H+ as needed. HCO3-, lactate, albumin (in the blood stream) and Hb, phosphates, proteins (in the cells)
What percentage of acute acid load can be buffered by bone?
40%
What does acidosis cause in regards to bone?
Calcium release
Where is the Calcium excreted
Through urine
What can chronic acidosis lead to in regards to bone (2)?
Fragile bones & pathological fractures, alkalosis causes carbonate to be laid down in bone
What happens if there is a change in the metabolic acid base balance?
Respiratory acid base system will compensate and vice versa
What happens in metabolic acidosis?
Increased production of acid (cellular hypoxia- anaerobi metabolism, ketoacidosis, lactic acidosis), decreased excretion of acid (hypoadrenocorticism, renal tubular acidosis, uraemia), increased acid intake (ethylene glycol toxicity, salicylate toxicity, metaldehyde toxicity), increased excretion of base (chronic renal failure, severe small intestinal diarrhoea)
In severe acidosis (<7.2) what are the clinical effects?
Cardiac arrhythmias, decreased cardiac contractility, arterial vasodilation (low blood pressure), decreased blood flow to liver and kidney, shift of oxygen-haemoglobin dissociation curve to the right (increased off loading of oxygen in tissues), insulin resistance, increased intracranial pressure, alterations in K+ and Ca++
What are some clinical causes of metabolic alkalosis?
Increased retention of bases, increased base intake, increased loss of acid (endocrine disease), most common cause is low Cl- concentration (vomiting of gastric contents, increased urinary excretion of Cl-)
What are the clinical effects of metabolic alkalosis?
Muscle twitching, seizures, cardiac arrhythmias, shift in oxygen haemoglobin dissociation curve to teh left (Hb binds more tightly to oxygen), hypokalaemia, hypocalcemia
With respiratory acid base, what is the main player? What does it act like?
CO2, acts like an ACID (increase in ventilatory rate will blow off more CO2, causing a respiratory alkalosis/ decrease in ventilatory rate will increase CO2, causing a respiratory acidosis)
What are some causes of respiratory acidosis?
Any disease or process or injury that causes hypoventilation (decreased rate or depth of breathing), traumatic brain injury/ brain disease, anaesthesia, upper airway obstruction, end stage resp. disease, resp. muscle weakness/paralysis (snake venom, tick paralysis, myasthenia gravis, phrenic nerve injury)
