acid/base balance and ABGs Flashcards
what is an acidic solution?
one with a higher concentration of hydrogen ions than pure water
how is CO2 transported in the blood?
as carbonic acid/bicarbonate
bound to haemoglobin
dissolved in plasma
chemical symbol for carbonic acid?
H2CO3
what is the main way that carbon dioxide is carried in the blood?
converted to carbonic acid (can then disassociate to bicarbonate ion and H+ ion in the buffering system)
chemical symbol for hydrogen?
H+
chemical symbol for bicarbonate?
HCO3-
what ion concentration determines pH?
does more of this ion make the blood more acidic or more alkaline?
H+
more H+ = more acidic
what are the terms for more hydrogen/less hydrogen in the blood than usual
acidosis/alkalosis
what do acid/base imbalances generally result from?
respiratory or metabolic failures
what is respiratory acidosis?
what is its consequence?
a condition where CO2 accumulates in the blood because of respiratory impairment
blood becomes more acidic
hypoxaemic follows
common causes of respiratory acidosis?
impaired ventilation - ie opioid overdose
impaired gas exchange - eg. asthma, pneumonia
clinical signs of respiratory acidosis?
cyanosis
cold and clammy skin
issues around RR
disorientation
what is respiratory alkalosis?
Condition of high pH due to excessive ventilation, resulting in excess excretion of CO2 from the lungs → less H+ → more alkalotic
common causes of respiratory alkalosis?
hyperventilation ie panic attacks
fever - increases metabolic rate, increasing RR
what is metabolic acidosis?
Condition of low blood pH resulting from excess acid produced (H+), or loss of base (HCO3-)
common causes of metabolic acidosis?
DKA
chronic renal failure - excess loss of bicarbonate, extra H+ produces
diarrhoea - bicarbonate lost from GI tract
clinical signs of metabolic acidosis?
kussmauls resps,
disorientation
what is metabolic alkalosis?
Condition of high pH resulting from excessive retention of HCO3- or loss of H+
common causes of metabolic alkalosis?
vomiting - H+ ions lost from system (stomach acid)
chronic kidney disease - increased secretion of H+ ions
clinical signs of metabolic alkalosis?
slower breathing
confusion
which two body systems regulate blood pH?
what is the other way the body regulates blood pH?
respiratory and metabolic (renal) systems
buffering system
when discussing the regulation of blood pH, what is a buffer?
a chemical which acts as either an acid or base depending on the number of H+ ions present in the blood
what are the four buffering pairs?
- Bicarbonate/carbonic acid system (HCO3-/H2CO3)
- Disodium/monosodium phosphate buffer system (HPO4-)
- Haemoglobin/oxyhaemoglobin system
- Protein buffer system
what is any alteration to return to normal blood pH know as?
compensation
what are the two types of compensation in regulation of blood pH?
complete compensation: pH returned to normal
partial compensation: signs of correction but pH has NOT returned to normal
what does an arterial blood gases test (ABGs) measure?
ph PCO2 PO2 HCO3 SaO2 (represents amount of Hb sites which have attached O2)
what regulates the amount of HCO3 in the blood?
the kidneys
PaCO2 - normal range ABGs?
does a higher or lower value indicate acidosis?
respiratory or metabolic?
35-45 mmHg
higher indicates acidosis, lower indicates alkalosis
respiratory
HCO3- :normal range ABGs?
does a higher or lower value indicate acidosis?
22-28 mEq/L
lower indicates acidosis, higher indicates alkalosis
PaO2 - normal range ABGs?
what does a lower than normal value indicate?
80-100 mmHg
hypoxaemia
six steps to ABG analysis
- Analyse the pH
- Analyse the PaCO2
- Analyse the HCO3
- Match the PaCO2 or the HCO3 with the pH
- Does the PaCO2 or the HCO3 go in the opposite direction of the pH? (IF YES, THEN THERE IS
COMPENSATION BY THAT SYSTEM) - Analyse the PaO2 and SaO2
