Pharm Acid/Base Flashcards
Acidity of solution reflects its
hydrogen ion content
PH stands for
Potential of hydrogen
causes for metabolic alkalosis
loss of acid from extracellular space examples
loss of gastric fluid- vomiting, NG drainage
loss of acid into urine- diuretic administration, hyperaldosteronism
causes for metabolic alkalosis
excessive HC03 loads
NaHCO3 administration
Lactate, acetate, citrate administration
Alkali administration to patients with renal failure
Abrupt correction of chronic hypercapnia
respiratory alkalosis
Hyperventilation-Increase in minute ventilation to level greater than that required to excrete the metabolic production of CO2
respiratory acidosis
Hypoventilation-Occurs when minute ventilation is insufficient to eliminate CO2 production without an increased capillary-alveolar CO2 gradient
metabolic acidosis is normally accompanied by compensatory
hyperventilation
in metabolic acidosis the significant reduction of PH
increased PVR
reduced myocardial contractility
decreased SVR
impaired response to CV system to endogenous or exogenous catecholamines
what compensatory mechanism is immediate
buffer system
the buffer system is followed by
respiratory
renal system- renal is slow and more effective
when the patient is acidosis- what happens to opioids, sedatives and anesthetic agents
sedatives and anesthetic agents on the CNS are potentiated
nonionized form of opioids increases and more penetrates the brain
what neuromuscular blocker do we avoid in the acidotic patient
succinylcholine in the acidotic patient with hyperkalemia
respiratory or metabolic acidosis augments nondepolarizing NMB agents?
respiratory acidosis
what are the circulatory depressant effects of volatile and IV anesthetics for the acidotic patient
exaggerated
what acid-base imbalance prolongs the duration of opioid induced respiratory depression
respiratory alkalosis
what electrolyte abnormality may precipitate severe arrhythmias in alkalemia
hypokalemia
especially during hypotension cerebral ischemia can occur from marked reduction in cerebral blood flow- what acid base imbalance is this
alkalemia
normal clearance maintains serum concentrations of lactate at
0.5-1mmol/L
where is most lactate cleared
by the liver
in the liver what three things does lactate undergo
oxidation
gluconeogenesis
eventual conversion to bicarbonate
lactate undergoes both passive diffusion and active transport into the liver via
monocarboxylate transporter
active transport becomes saturated as serum lactate concentrations >
2.5mmol/L
severe reduction in hepatic blood flow will do what to hepatic lactate clearance
decrease
lactate acid is a strong acid and therefore dissociates almost completely under physiologic conditions into the
lactate anion
and
hydrogen ion
when does lactate accumulation occur
mainly during anaerobic glycolysis
generated under normoxic conditions
in the critically ill patient lactate production may increase while lactate clearance is impaired- meaning…
lactic acidosis may occur
a serum lactate ___ upon admission is an independent predictor of mortality in critically ill patients
> 1.5mmol/L
failure to decrease lactate concentration to less than or equal to ___24 hours after admission is also associated with significant mortality
1.0mmol/L
this investigational drug decreases concentration of lactate
dichloroacetate (DCA)
dichloroacetate decreases concentration of lactate in what 4 situations
malaria
DKA
burns
cardiogenic shock
DCA activates
activates the mitochondrial pyruvate dehydrogenase complex, thus accelerating the irreversible oxidation of lactate via pyruvate to acetyl CoA which then enters the Krebs cycle
The buffer:
tris (hydroxymethyl) aminomethane or THAM can be used to treat metabolic acidosis and does not generate carbon dioxide
Lactic Acidosis
It may be useful as an alternative to sodium bicarbonate to treat metabolic acidosis in pts who are hypernatremic
When cause of metabolic acidosis is unclear measure:
Serum lactate
BUN,
Creatinine
Glucose
If this does not identify the etiology then:
Send serum for toxicology to measure:
Salicylates
Methanol
Ethylene glycol
large volume infusion of isotonic saline may result in
hyperchoremic metabolic acidosis
Dilutional acidosis also occurs when the plasma pH is decreased by extracellular volume expansion with chloride-containing solution such as NS
Dilutional acidosis also occurs when the plasma pH is decreased by extracellular volume expansion with chloride-containing solution such as NS
ph of water at 37 degrees celsius is 6.8- what does this mean
any increase in the free water volume of the body will contribute to acidosis.
normal saline is commonly thought of as physiologic. why
because it has an osmolarity close to that of plasma and does not lyse RBC
what is the PH of normal saline? as it contains more chloride and slightly more sodium
5.7
infusion of a large volume of NS will increase ___
plasma chloride concentrations to a relatively greater degree than sodium concentrations
chloride is a
strong acid (proton donor)
sodium is a
strong base (hydroxyl donor)
BE is a calculation (not measured) from an algorithm baed on measured
bicarb and PH
does base excess distinguish among the possible causes of metabolic acidosis
no
anion gap normal
6-10 mEq/L
acute respiratory acidosis or alkalosis what happens to BE
it does not change.
respiratory acidosis in the presence of metabolic acidosis the BE is
<0
if underlying issues was metabolic alkalosis BE=
BE>0
mixed respiratory and metabolic acidosis is a common clinical problem - how do we guide treatment
BE can be a guide to treatment
does base excess distinguish among the possible causes of metabolic acidosis
no
major extracellular anions (-)
chloride and bicarbonate
the major extracellular cation is
sodium
is potassium measured in its anion gap
calculation varies from institution
k -ca- mg is grouped into
unmeasured cations
anion gap refers solely to the differences in concentrations between
anions and cations
electroneutrality occurs when
the concentrations of the combined unmeasured anions exceed that of the unmeasured cations by the same amount
Anion Gap
“Anion Gap” refers solely to the differences in concentration between the traditionally measured anions and cations.
Strong Ion Gap (SIG):
strong cations
compares excess measured serum concentrations of strong cations (NA+, K+, Mg++, Ca++)
Strong Ion Gap (SIG): strong anions
(Cl-, HCO3-, albumin, phosphate).
what can strong ion gap do
differentiate between dilution acidosis to acidosis due to tissue hypo perfusion
normal anion gap metabolic acidosis
diarrhea
pancreatic fistula
renal tubular acidosis
intoxication ammonium chloride, acetazolamide, toluene.
hyperchoremic acidosis (excess saline administration)
increased anion gap
lactic acidosis
ketoacidosis
chronic renal failure accumulation of sulfates, phosphates, urea.
intoxication organic acids (salicylate, ethanol, methanol, formaldehyde, ethylene glycol, paraldehyde) INH, sulfates, metofrmin
massive rhabdomyolysis
metabolic alkalosis is commonly
iatrogenic
causes of metabolic alkalosis
vomiting with excess hydrochloride acid ng suction chronic administration of diuretics hypoalbuminemia excess secretion of aldosterone
a loss of free water (PH 6.8) will cause a
volume contraction alkalosis
treatment of metabolic alkalosis
treat underlying cause
hospital cause of metabolic alkalosis
excess administration of sodium bicarbonate
when is respiratory acidosis compensated-
how does respiratory compensation occurs
within 6-12 hours
increased secretion of hydrogen ions with a resulting increase in the plasma bicarbonate concentration.
correction of chronic respiratory acidosis is
iatrogenic hyperventilation.
acute metabolic alkalosis. because increased plasma bicarbonate is not promptly eliminated by the kidneys
compensation of respiratory alkalosis
decreased reabsorption of bicarbonate ion from renal tubules.
compensation for metabolic acidosis
stimulates alveolar ventilation, which causes rapid removal of carbon dioxide
the respiratory compensation for metabolic acidosis is only partial - what does the PH do
Ph remains somewhat below normal
metabolic alkalosis compensation
diminishes alveolar ventilation
metabolic alkalosis and metabolic acidosis- the respiratory compensation is only ever
partial
during cardiopulmonary bypass- what happens to c02 and ph
ph will increase to 7.6 and c02 becomes more soluble.
in PH stat we give c02 via
the oxygenator
who do we give co2 in PH stat
in pediatric cardiac surgeries
what is a negative outcomes oh PH state
microemboli
what is the Main goal of PH stat
to provide co2 for cerebral vasodilation
to combat the leftward shift of the oxyhemoglobin during hypocarbia and hypothermia and alkalosis. so the addition of the PH stat strategy will help the oxygen unload the hemoglobin
who do we use alpha stat on
adult cardiopulmonary bypass
does alpha stat have microemboli
no because supplemental carbon dioxide is not administered
does alpha stat have temperature correction
no
what is the alpha stat strategy
seek to optimize enzyme function during hypothermia.
the objective of alpha stat is to
maintain biologic neutrality by preserving the alpha imidazole and protein charge state OH/H ratio.
