Acid/base Balance

Question 1

Physiological pH and consequences of disturbance

Answer 1

• normal: ECF is 7.4, blood is 7.35-7.45
• acidosis: 7.35-6.8
• alkalosis: 7.45- 8.0
• consequences: disturbances in electrolytes, enzymatic function, hormone function, bone synthesis and reabsorption

Question 2

Buffer systems in the body

Answer 2

• ICF: phosphorus
• proteins: carboxyl group donates H+ and amino group accepts H+
• carbonic acid bicarbonate system:
  CO2+H2OH2CO3H+HCO3Na+HCO3 NaHCO3
  Bicarbonate stores can be utilised to neutralise protons, forming carbonic acid which can be exhaled as CO2. Similarly, CO2 can be used to make carbonic acid and neutralise alkaline environments
• action of the kidney: can excrete H+ or HCO3 depending on environment, can also conserve one or the other

Question 3

Respiratory acidosis

Answer 3

• Characterised by: high blood CO2 (more than 45 mmHg)
• chronic causes: emphysema, head trauma affecting respiratory rates
• acute causes: pneumothorax, pulmonary oedema
• symptoms: breathless, restless, tremors, convulsions, coma
• body response: excrete more H+ through kidneys and conserve HCO3
• treatment: restore ventilation, lactate IV (converts to HCO3 in liver)

Question 4

Metabolic acidosis

Answer 4

• characterised by: low HCO3 and high H2CO3
• causes: unable to excrete H+ in kidneys, depletion of HCO3 reserves i.e due to diarrhoea
• symptoms: headaches, lethargy, coma, death
• body compensation: excrete more H+ (if able) and conserve HCO3, hyperactive breathing to blow off CO2
• treatment: IV lactate (converted to HCO3 in the liver)

Question 5

Respiratory alkalosis

Answer 5

• characterised by: low CO2 (pCO2 <35 mm Hg)
• primary causes: hyperventilation (acute alkalosis), oxygen deficiency at high altitudes, pulmonary disease/ congestive heart failure
• symptoms: numbness, lightheadedness, nervousness, convulsions
• body compensation: kidneys conserve H+ and excrete HCO3
• treatment: breathe into paper bag, IV chloride

Question 6

Metabolic alkalosis

Answer 6

• characterised by: high HCO3
• causes: excess vomiting, too many antacids, endocrine disruptors, severe dehydration
• symptoms: confusion, tremor, lightheadedness, muscle twitching
• body compensation: kidneys conserve H+ and excrete HCO3, breathing slows to conserve CO2 (but risk of hypoxia)
• treatment: IV chloride to replace HCO3