1What is the normal pH range?
7.35 to 7.45
2What does pH stand for?
Potential of hydrogen
3What is the normal anion gap when potassium is included?
12-20 mEq/L
4What is the normal anion gap when potassium is excluded?
8-16 mEq/L
5Why is maintaining pH important?
Maintains normal enzyme function, protein structure and cellular processes.
6What is the optimum pH for pepsin?
Around 2-3
7What is the optimum pH for amylase?
Around 7
8What is the optimum pH for tryspin?
Around 8-9
9What are some acute things that happen when pH is out of control?
Decreased heart contractility; altered neurological function; potassium shifts between cells and blood, potentially causing hyperkalaemia or hypokalaemia depending on the disturbance.
10What are some chronic things that can happen when pH is out of control?
Effects on bone and stone formation; associated with progression of kidney disease.
11What organ regulates volatile acid?
Lungs
12What organ regulates titratable acid?
Kidneys
13What are some things that increase psychological acid load?
Aerobic respiration; Anaerobic respiration; Sulfuric acid production from sulfur-containing proteins; Acid production from ketone bodies; Phosphoric acid production from phosphate-containing compounds.
14What is a buffer?
A weak acid and its conjugate base, or a weak base and its conjugate acid, that resist changes in pH when small amounts of acid or alkali are added.
15How is acid excreted?
Volatile acid is excreted as CO2 via the lungs, while non-volatile acids are excreted by the kidneys.
16What is the difference between strong acids/alkali and weak acids/alkali?
Strong acids and alkalis completely dissociate in solution whereas weak acids and alkalis partially dissociate in solution.
17What are the main buffer systems in the body?
Bicarbonate buffer system; Haemoglobin buffer system; Protein and amino acid buffer systems; Phosphate buffer system.
18What does the henderson hasselbach equation show?
An increase in bicarbonate relative to CO2 increases pH, while a decrease lowers pH.
19Describe acid excretion in the lungs.
The lungs remove volatile acid as CO2. Increased ventilation removes more CO2 and raises pH, while decreased ventilation retains CO2 and lowers pH.
20Describe acid excretion in the kidneys.
Reabsorbs filtered bicarbonate; generates new bicarbonate; increases hydrogen ion secretion and excretion in urine, mainly buffered by phosphate and ammonia.
21Where is bicarbonate reabsorbed in the nephron?
Predominantly in the proximal tubule.
22Where in the nephron are hydrogen ions excreted?
Mainly in the proximal tubule and distal nephron, particularly the collecting ducts.
23What can causes repsiratory acidosis?
Hypoventilation causing CO2 retention
24What can cause respiratory alkalosis?
Hyperventilation causing excessive CO2 loss
25What is the primary cause of metabolic acidosis?
Diarrhoea; Renal failure; Lactic acidosis; Ketoacidosis; Renal tubular acidosis; Certain toxins.
26What does a high anion gap acidosis show?
Metabolic acidosis due to accumulation of unmeasured anions, such as in renal failure, lactic acidosis, ketoacidosis or poisoning.
27What does normal anion gap acidosis show?
Metabolic acidosis commonly caused by bicarbonate loss or impaired renal acid excretion, such as in diarrhoea or renal tubular acidosis.
28What are the causes of metabolic alkalosis?
Vomiting; Nasogastric suction; Diuretic use; Excess mineralocorticoid activity; Alkali intake in susceptible individuals.
29What is the anion gap?
The difference between measured cations and measured anions, used to estimate the concentration of unmeasured ions in the blood.
30What are the meausred cations?
Sodium and potassium ions.
31What are the measured anions?
Chloride and bicarbonate.
32What does a high anion gap mean?
There is an increased concentration of unmeasured anions, which may indicate lactic acidosis, ketoacidosis, renal failure or poisoning.
33Describe how the hypercapnic drive works in COPD?
Some patients with advanced COPD develop chronic CO2 retention and may have a reduced ventilatory response to CO2. Hypoxaemia can contribute to their respiratory drive. Excess oxygen can worsen hypercapnia through changes in ventilation-perfusion matching and the Haldane effect, as well as reduced ventilation in some patients. Oxygen should be carefully titrated, usually to a target saturation of 88–92% in patients at risk of hypercapnic respiratory failure, with blood gases monitored as indicated.