pH : acidosis and alkalosis Flashcards
When is something determined to be an acidosis (pH) v alkalosis
role of CO2 levels and how they serve as a prox. acid
role of HCO3 - levels and how it serves as a base
pH < 7.35 = acidosis
normal = 7.35 - 7.45
pH > 7.45 = alkalosis
CO2: plays a vital role in exchange of waste: going from high to low concentrations via diffusion : ability to diffuse from the RBC into the alveoli across the pulmonary interface is vital!!
- level of CO2: triggers chemoreceptors in the caroitid body and medulla
CO2: acts like an acid as an H+ donor
CO2 normal range: 35-45
Co2 + H2) = HCO3- + H+
Bicarb (HCO3-) : plays a vital role in buffering the acidic compounds of the body by accepting a H+
HCO3- : base (adding more base, pushes more CO2 to be produced and breathed out)
normal HCO3- : 22-26
process of thinking to determined the metabolic disorder given a pt. blood gas values
- look at the pH : acidosis or alkalosis
- evalute Co2 and HCO3 -
if the CO2 is derange (like high) and the pH is low: probably a repiratory acidosis: the lack of ability to breath off CO2 = increase CO2 in blood = decreased pH
- even if the bicarb is high:need to evalute what the pirmarly driver of teh derangment is: the high bicarb could be trying to off-set the acidosis (the Co2 will be much more out of wack than the bicarb)
a dareanged CO2 value = respiratoyr issue
a deranged HCO3- value = metabolic disorder
idea behind deciing if something is compensated or not?
compensation mechansims will NEVER make the homeostatis reach normal : they will just attempt to push the needle back towards normal
compensatory mechanisims: secondary responses
how do you decided what is chloride responsive metabolic alkalosis v chloride unresponsive
Chloride Responsive: where giving Cl- will help with the alkalosis (ike giving saline will help)
- a urine chloride level < 20: TRYING TO hold onto chloride
- a loss of chloride (GI losses/vomiting)
- loss of water (diuretics)
- post hypercapnic state
Chloride Unresponsive: whenre giving Cl- will not help
- urine chloride > 20
- hypokalemia
- mineralocorticoid exccess: increased retention of sodium and excretion of potassium and hydrogen (which creates an alkalosis state)
how does acidosis and alkalosis change the oxygen dissassociation curve
pH decreased: or a more acidotic state will push the graph to the right: indicating that there will be a decreased affinity of hemoglobin to hold onto oxygen, it will readily give it up
what is the anion gap
how is it calculated
reasons for elevated anion gap
the net abudence of cations (+) should equal the amout of anions (-) ; we meaure the Na+, Cl- & HCO3-
the anion gpa: refers to the amount of unaccounted for anions (-) in the serum to determine how abudent they are
a normal anion gap = 4-12
a corrected anion gap: accounts for the amount of anions which are bound to albumin within the serum
increased anion gap: more negative anions present in the serum: usually due to increased acids in theboyd: because when acids are present, they dissassocaite into H+ and their conjugate base (anion!!!) so there lots of anions when theres increased acids
Reasons for elevated gap
M: methanol
U: uremia
D: DKA
P: propylene glycol
I: isoniazed
L: lactic acidosis
E: etylene glycol
S: salysaicds (NSAIDS)
a non-gap: will occur when theres a relative lack of HCo3- instead of a surplus of acids in the serum
Reasns for non-gap acidosis
H: hyperchloremia
A: acetazolamide
R: RTA
D: dirrhea
U: uteroenteric fistula
P: pancreoenterostomy
in these intances, these increased the anions, so the body tries to compensate by decrease HCO3- to balance: leadint to no gap in the anions, but still acidosis
Calculate: Na - (Cl +HCO3)
what is the delta gap and why is it used
< 1:1 ratio
> 2:1 ratio
Delta Gap: is done to evaluate the ratio between the rise in the anion gap relative to the fall inthe HCO3-
(change in anion gap) / (change in HCO3-) = normal 1.6:1 ratio showing that for every 1.6 increase in the anion gap (increase acidic components) there is a 1 change of the bicarb falling to compensate for the anions present
if the rati is < 1:1 = combined gap/ nongap acidosis
- example: a lactic acidosis (type of gap acidosis) with a hyperchloremia secondary to saline resusitation (a non-gap acidosis)
if the ratio is > 2:1 = superimposed gap with metabolic alkalosis
- example: a hypovolemic lactic acidosis (an anion gap acidosis) due to vomiting (alkalosis)
