PHYS Acid-Base Disorders & Compensation - Week 11 Flashcards
What system is the fastest compensatory mechanism for buffering?
Carbonic acid-bicarbonate.
Primary & secondary changes in metabolic acidosis.
P - decrease in HCO3-
S - decrease in pCO2
Primary & secondary changes in metabolic alkalosis.
P - increase in HCO3-
S - increase in pCO2
Primary & secondary changes in respiratory acidosis.
P - increase in pCO2
S - increase in HCO3-
Primary & secondary changes in respiratory alkalosis.
P - decrease in PCO2
S - decrease in HCO3-.
Normal body pH range
7.35-7.45
Respiratory acidosis pH and paCO2
pH < 7.35 & PaCO2 > 45mmHg
Respiratory alkalosis pH and paCO2
pH >7.45 & PaCO2 < 35mmHg
Metabolic acidosis pH and HCO3- changes
pH < 7.35 & HCO3- < 22mmol/L
Metabolic alkalosis pH and HCO3- changes
pH > 7.45 & HCO3- > 26mmol/L.
Acidaemia definition
Arterial blood pH < 7.35
Alkalaemia definition
Arterial blood pH > 7.45
Acidosis definition
The abnormal process that decreases the arterial blood pH to < 7.35.
Alkalosis definition
The abnormal process that increases the arterial blood pH to > 7.45.
Metabolic acidosis causes
Lactate, toxins, ketones, renal impairment/failure.
Remember LTKR.
What is the anion gap?
Refers to the unmeasured anions (-vely charged) like proteins, phosphates, sulphates & organic anions.
NAGMA
Normal anion gap metabolic acidosis
HAGMA
High anion gap metabolic acidosis
Hyperchloraemia & anion gap relationship
NAGMA, but increased Cl-
What is acute acidosis & possible causes?
Sudden elevation of PCO2 due to insufficient ventilation (e.g., chest wall injuries, asthma, Gillian-Barre syndrome).
What is the relationship btw PaCO2 & minute volume?
Inversely proportional
PaCO2 = 1/MV.
What is chronic acidosis & possible causes?
Chronic lung disease w restrictive lung disease w V/Q mismatch (e.g., obstructive disease, chronic neuromuscular disease).
What is metabolic alkalosis & possible causes?
Caused by an increase in HCO3- (e.g., impaired renal excretion of HCO3-, nasogastric drainage, vomiting, diuretics).
Simple vs mixed disturbances
Simple disturbances are one of the four primary disturbances.
Mixed disturbances are when a pt has more than one disorder - which may worsen/cancel each other out.
Mixed disorder location on the arterial blood pH-plasma nomogram?
Outside yellow shaded areas.
Severe vomiting is an example of what kind of alkalosis/acidosis?
Metabolic alkalosis.
Renal failure is an example of what kind of alkalosis/acidosis?
Metabolic acidosis.
Nerve disease leading to a partial paralysis of respiratory mms is an example of what kind of alkalosis/acidosis?
Chronic respiratory acidosis.
Student having a panic attack & hyperventilating is an example of what kind of alkalosis/acidosis?
Acute respiratory alkalosis.
Anaemia is an example of what kind of alkalosis/acidosis?
Chronic respiratory alkalosis.
Pt who has fallen and broken their ribs is an example of what kind of alkalosis/acidosis?
Acute respiratory acidosis.
2 x of classifications of acidosis based on anion gap? Provide example of what conditions normally cause this and the chemistry behind it.
- High anion gap acidosis (e.g., increased lactic acid, ketoacids, formic acid, oxalic acid) – more organic acid being produced/ingested
- Normal anion gap acidosis (e.g., via diarrhoea, vomiting, renal tubular acidosis ) - loss of HCO3-
Hyperchloraemia often occurs with normal anion gap acidosis due to Cl- loss.
When should anion gap be calculated? Why?
When metabolic acidosis is suspected - to help determine cause.
Severe diarrhoea is an example of what kind of alkalosis/acidosis?
Metabolic acidosis.
PaO2 arterial vs venous.
75-100mmHg & 40mmHg.
2 x compensation & situations when these compensations are seen in acid-base disorders.
Renal & respiratory.
Maximal renal seen in chronic resp disorders.
Maximal respiratory seen in metabolic disorders.
Has to be chronic for renal, as kidneys respond within 2-4 days.
