Acid-base and Blood Gases Flashcards
What happens in an oxygen deficit?
Haemoglobin gives up O
Takes in CO2
HCO3- given up + exchanged for Cl-
What happens when its oxygen rich?
Large shunt of O into RBC
High affinity for O
CO2 out = gives up H+
Cl- exchanged for HCO3-
What happens if there is an injury in the lungs?
Acute problem = chest can’t respond fast = can’t get rid of gas = RBC becomes saturated
What normal metabolic processes are involved in the production of hydrogen?
Digestion of food
Metabolism of drugs
Errors with within metabolism
Which organ is responsible for the secretion of hydrogen?
Kidney
Why can anaerobic metabolism produce H?
Produces lactate = an acid = H+
How is CO2 produced?
Oxidative metabolism
How is CO2 excreted?
By ventilation
What is the normal pH within the body?
7.35-7.46
Describe renal filtration
1. maintain acid-base balance
Na+ + HCO3- filtered in glomerulus
Renal tubule cells secrete H+ in exchange for Na+
CO2 is formed by reaction of H+ + HCO3- + diffuses into tubule cell = impermeable to bicarbonate
CO2 converted back to HCO3- in cell
Na+/HCO3- symporter carries Na+ + HCO3- across membrane
What do renal cells do?
Secrete H+ in exchange for Na+
Describe renal filtration
2. maintain acid-base balance
Na+/H+ antiport secretes H+
H+ in filtrate combines with filtered HCO3- to form CO2 + H2O
CO2 diffuses into cell + combines with H2O to form H+ + HCO3-
H+ is secreted again + excreted
HCO3- is reabsorbed
Glutamine is metabolised to ammonium ion + HCO3-
NH4+ is secreted + excreted
HCO3- is reabsorbed
What are buffering systems in intracellular fluid?
Phosphate buffer system
Protein buffer
What are buffering systems in extracellular fluid?
Protein buffer
Carbonic acid-bicarbonate system
What is involved in protein buffering system?
Haemoglobin
Amino acid (all proteins)
Plasma protein
What is the concentration of H+:
directly proportional to?
inversely proportional to?
[CO2]
[HCO3-]
What is the renal system dependent on?
Na+
= no sufficient Na+
= H+ can’t get out
What is acidosis?
High [H+] = low pH
What is alkalosis?
Low [H+] = high pH
What is non-respiratory acidosis caused by?
Increased [H+] = poisons
Decreased excretion = renal failure
Decreased [HCO3-] = diarrhoea
What are the reasons for increased [H+]?
Diabetic ketoacidosis = absolute lack of insulin = metabolism of fatty acids
What are the reasons for decreased H+ excretion?
Decreased GFR reduces filtration of Na+ = less available to be exchanged with H = H accumulates
Describe non-respiratory acidosis
H+ rises = buffered by bicarbonate
Carbonic acid produced + dissociates
Non-respiratory acidosis develops = stimulates respiratory centre to remove CO2 = producing compensatory respiratory alkalosis
= rapid breathing rate
How do you treat non-respiratory acidosis?
Removal of underlying problem
BUT renal function must be maintained
Bicarbonate used in patients with pH <7
Summary of non-respiratory acidosis
pH decrease
H+ increase
CO2 decrease = rapid breathing rate
HCO3- decrease = bicarbonate used to neutralise H+
What are the causes of respiratory acidosis?
Airway obstruction
Depression of respiratory centre = drugs + illness
Neuromuscular disease
Pulmonary disease
What happens in acute respiratory acidosis?
pH decreases
H+ increases
CO2 increases =respiratory system can’t function normally
HCO3- slight increase = some used to neutralise BUT reaction pushed right
What happens in chronic respiratory acidosis?
pH slight decrease/normal
H+ slight increase/normal
CO2 increase
HCO3- increase
What is respiratory response to metabolic change?
FAST
What is metabolic response to respiratory change?
SLOW
How do you treat respiratory acidosis?
Restore O = ventilation + high conc of O
= O prime issue = die from hypoxemia 1st
What are the causes of non-respiratory alkalosis?
Excess alkali administration
Overcorrection of acidosis
Loss of free H
How is free H lost?
GI loss
Mineralocorticoid steroid
Diuretic therapy
What happens in non-respiratory alkalosis?
pH increases
H+ decreases
CO2 increases
HCO3- increases
How do you treat non-respiratory alkalosis?
Normal saline infusion
Potassium supplements
What causes respiratory alkalosis?
Hypoxia = COPD, altitude
Increased drive = infection, respiratory stimulants
What happens in acute respiratory alkalosis?
pH increases
H+ decrease
CO2 decreases
HCO3- slight decrease
What happens in chronic respiratory alkalosis?
pH slight increase/normal
H+ slight decrease/normal
CO2 decreases
HCO3- decreases
What is the treatment for respiratory alkalosis?
Remove underlying cause
Hyperventilation = rebreathe CO2 = brown paper bag