AcidBase Pathology Flashcards
how do we assess acid base status
what is the ph ie above 7.45 or below 7.35
is the primary disorder metabolic or respiratory
is there compensation - normal respiratory or metabolic compensation
how do respiratory acidosis and metabolic differ
RAc = increased pCO2 MAc = decrease NpCO2
how do respiratory alkalosis and metabolic differ
RAl = decreased PCO2 MAl = increase in NpCO2
how does respiratory vs metabolic compensation differ
RC - changes in CO2 (help metabolic disturbances)
MC - changes in HCO3 (help respiratory disturbances)
how do we measure bicarbonate levels
main lab bicarbonate - calculated in part from CO2
standard bicarbonate - removes respiratory contribution ie normal standard bicarbonate = all respiratory
abnormal = metabolic component
what is base excess (BE)
amount of acid or alkali to titrate blood pH to 7.40 - tells us if there is a metabolic component
what does a negative vs a positive BE mean
negative (less than 2.3mmol/l) = metabolic acidosis
positive BE (greater than 2.3 mol/L) = metabolic alkalosis
what is an anion gap
difference between the sum of measured anions and cations
what does an increased anion gap mean
significant amounts of unmeasured anions such as ketones, lactate, salicyate, proteins)
what are the physiological characteristics of metabolic acidosis
decreased pH increased H+
normal or decreased pCO2
deceased HCO3
increased pO2
what are the signs and symptoms of metabolic acidosis
nausea, vomiting, anorexia
tachypnoea due to respiratory compensation
kussmaul breathing in severe acidosis
what are the causes of metabolic acidosis
increased acid formation
decreased acid excretion (renal failure)
loss of bicarbonate (diarrhoea)
acid ingestion
what is the normal physiological response to metabolic acidosis
protein and bicarbonate buffering try to help
respiratory compensation - hyperventilation
increase HCO3 regen
increase H+ excretion in urine
what are the physiological characteristics of metabolic alkalosis
increased pH and decreased H+
normal or increased pCO2
increased HCO3
decreased pO2
what are some causes of metabolic alkalosis
loss of H+ eg vomiting
administration of HCO3
potassium depletion
what is the normal physiological response to metabolic alkalosis
release of H+ buffers
respiratory compensation - reduce breathing
what are the physiological characteristics of respiratory acidosis
decreased pH and increased H+
increased pCO2
normal or increased HCO3
deceased pO2
what are the signs of respiratory acidosis
relate to underlying disorder or dyspnoea
what are the causes of repository acidosis
defective control of respiration
defective respiratory function eg pneumothorax or pulmonary disease
what is the physiological response
limited buffering by hb
try to have respiratory compensation ie breathe quicker
max bi carb reabsorption and excretion of NH4 and H2PO4
what are the physiological characteristics of respiratory alkalosis
pH increased and H+ decreased
decreased pCO2
normal or lower HCO3
increased pO2
what are the signs and symptoms of respiratory alkalosis
severe = hypocalceamia - headache, lethargy, delirium and seizures
what are some causes of respiratory alkalosis
central - head injury, stroke, hyperventilation
pulmonary - PE, pneumonia, asthma
iatrogenic - excessive mechanical ventilation
what is the normal physiological response to respiratory alkalosis
release of H+ from non-bicarbonate buffers
decreased renal regen of HCO3
