acid base disorders Flashcards
(26 cards)
what does increased pco2 levels represent and how does it manifest
increased pco2 levels- respiratory acidosis
hypoventilation
caused by bronchitis, asthma emphysema, respiratory conditions or mechanical reasons, guilian barre syndrome, mysthenia gravis, clostridium toxins, motor neurone disease, spinal injury nerve agents, thorax instability- multiple rib fractures
reduced diffusion capacity- pneumonia, pleural effusion, pulmonary oedema, pulmonary fibrosis,- usually affects oxygen first
reduced respiratory drive- sleep apnoea, opiates benzodiazepine- respiratory depression
chronic conditions will show partial metabolic compensation
what does decreased pco2 represent and how does it manifest
respiratory alkalosis- hyperventilation- hypocapnia
high altitude n2 atmosphere
anxiety panic attack head injury
stroke
attempt to extend breath during diving
what does increased hco3- represent and how does it manifest
metabolic alkalosis-
loss of chloride- vomiting, nasogastric tube on suction
hypokalaemia- h+ shifts into intracellular fluid
hyperaldosteronism- hypokalaemia- alpha intercalated cells, excrete hydrogen ions into lumen tubular fluid
principle cells increased sodium reabsorption into blood and increased potassium secretion into filtrate
dieuretic use or genetic disorders like glietmans or bartter syndrome
what does decreased hydrogen bicarbonate represent and how does it manifest
metabolic acidosis- diarrhoea
loss of bicarbonate- diarrhoea
renal tubular acidosis- mutations in proton pump sub units AE1 NHe3 and others
renal failure-no new bicarbonate generated, no ammoniagenesis
added acids- lactic acidosis ketoacidosis- shock, mitochondrial disorders, diabetes type 1
intoxication- salicylates, methanol, ethanol (ethanol induces lactic acidosis)
what is the anion gap
helps to assess the presence of abnormal acids (or rarely bases)
na+ k+ often omitted (hco3-) +cl- 8-16mmol/L 10-20 without potassium
an increased anion gap suggests that exogneous or endogenous acids are elevated
decreased anion gap is rare but may be found in multiple myeloma where abnormal levels of paraproteins- immunoglobulins are found
lethal levels of salicylic acid usually increase the anion gap by 5-10mmol/L
critical levels of lactate can reach 10-15mmol/L (normal 0.5-1, in critically ill patients<2)
what is the compensation for respiratory acidosis
renal retention of hco3- ———> increased bicarbonate slow
what is the compensation of respiratory alkalosis
renal- excretion of hco3- ——> decrease bicarbonate slow
what is the compensation of metabolic acidosis decreases bicarbonate
respiratory hyperventilation decreases carbon dioxide
renal retention of bicarbonate increase bicarbonate
what is compensation of metabolic alkalosis
respiratory hypoventilation increase pco2
renal excretion of hco3- —–> decrease bicarbonate
in acute care what parameter is used to distinguish between respiratory and metabolic disorders
base excess
base deficit
who introduced the concept of base deficit
astrup
siggard anderson amount of acid or base needed to titrate a blood sample equilibrated at 40mmhg co2
ph 7.40
eliminates respiratory component and thus allows to assess metabolic disorders or compensation independently from respiration
look at diarrhoea, vomiting, known conditions such as asthma or copd, are they hyperventilating or showing any signs of shock
compare relative changes in bicarbonate and pco2
what does the upper left segment of the davenport diagram show
respiratory acidosis with partial metabolic compensation
what does the right upper segment of the davenport diagram represent
metabolic alkalosis with partial respiratory compensation
what does the lower left segment of the davenport diagram represent
metabolic acidosis partial respiratory compensation
what does lower right segment of davenport diagram represent
respiratory alkalosis with partial metabolic compensation
what does the space inebetween the segments represent
combined disorders
what is the fundamental difference between a channel and a transporter
channels can only allow substances to be transported through via their own chemical gradient ( facilitated diffusion), transporters can also engage in active transport, atp is needed
explain why thiazide diuretics enhance, calcium reabsorption
thiazide dieuretics block the sodium chloride transporter in distal convoluted tubule, this increases the excretion in sodium and water- increases amount of calcium reabsorbed
na cl channel in distal convoluted tubule has enhanced activity
how many nacl are transported per ATP hydrolysed in TAL , DCT and CD
why are peritubular capillaries well suited for reabsorption
they have a lower hydrostatic pressure at venous end
what would happen if dct only had luminal potassium channels
there would be no potassium being excreted into interstitial fluid, build up of potassium potassium not recycled
which ions are transported transcellularly
sodium transported transcellularly in proximal convoluted tubule
thick ascending limb
distal convoluted tubule
collecting duct via principal cells
potassium reabsorbed transcellularly in proximal tubule and alpha intercalated cells
calcium transcellular in dct and passive paracellular in proximal convoluted tubule
what is the equilibrium potential of sodium na+
60mv
high outside, low inside
what is the equilibrium potential of potassium
-90mv
