Acid Base Physio Flashcards
For the H-H equation, what is pH equal to? How can you rearrange this to solve for bicarb? To regulate pH what do the kidney and lungs do? What’s the normal level of pH?
pH = 6.1 + log([bicarb]/.03[PCO2]); Bicarb = .03PCO2 x 10 ^ (pH - 6.1); kidney sets level of bicarb, while lungs set partial pressure of CO2; 7.4
What is “normal” PCO2? What happens with hyper- or hypoventilation? What is the overriding equation relating CO2 to bicarb?
40 mmHg; you have different metabolic lines with higher pressure CO2 lines to the left, lower pressure CO2 lines moving to right; CO2 + H2O H2CO3 H+ + HCO3
What is total CO2 equal to? With more CO2 bubbled, what does that mean for pH?
TCO2 = [CO2] + [H2CO3] + [bicarb], with [CO2] = .03PCO2; at equilibrium, with more CO2, that means pH is lower because you use LeChat principle to make more H+
What happens with increased Hb with bicarb?
You see more bicarb made per change in pH (Hb can bind H, and using Lechat, you can make bicarb)
On the graph pitting bicarb vs. pH, what is the “normal” point? What causes respiratory acidosis? On the graph, from the normal point, where would you find respiratory acidosis? What is the compensation for respiratory acidosis?
PCO2 40 mmHg, pH = 7.4, bicarb is 24 mM; hypoventilation: COPD, asthma, narcotics/anesthesia, airway obstruction, lung collapse, MD or paralysis, pneumonia, bronchitis, pulmonary edema; Moving upward and left along respiratory line; kidney makes more bicarb and secretes more H into urine
What happens with bicarb during respiratory acidosis and renal compensation? What mediates the change in pH in either case?
They can both increase; the proton level, which changes if H is made b/c of having too much CO2 or if you make bicarb to bind H
What causes hyperventilation? What does this lead to? How do you represent this condition on the graph? How do you compensate?
Ventilator too high in ICU, anxiety attack, trauma to respiratory center in brain, brain tumor; respiratory alkalosis; move downward and to the right; kidney reabsorbs less bicarb to try and allow for proton concentration to increase and lower pH
What is the most common acid/base abnormality in hospital patients? How is this represented on the graph? What causes this? What is the compensatory response?
Metabolic alkalosis; Move upward and to the right; ECF volume conctraction (Cl responsive: vomiting, gastric tubes, excess diuretics) and ECF volume expansion (Cl resistanct: hyperaldosteronism); decrease in ventilation but WE NEED O2, so kidney will reabsorb less bicarb
What do excess diuretics cause?
Increased loss of NaCl and fluid –> increased RAA –> increased renal proton secretion –> plasma bicarb increase –> METABOLIC ALKALOSIS
In cases of metabolic acidosis, what is the compensation? What are causes of metabolic acidosis?
Pulmonary compensation is hyperventilation, while renal response is reabsorbing bicarb; Diabetes mellitus (acetoacetic and beta-hydroxybutyric acids), lactic acid, poisons (formic acid, glycolic acid, acetylsalicyclic acid); hyperchloremic: prox renal tubular acidosis (reduced bicarb reabsorption), distal renal tubular acidosis (acid secretion/excretion decreased), diarrhea
What is the anion gap? What is the normal value?
Na - (Cl + HCO3); 12+/- 4
What organ compensates for the metabolic disorders? What compensates for respiratory disorders?
Lung; kidney
How is base excess defined? When is this positive? When is it negative?
Base excess = Actual [bicarb] - 24; Alkalosis; acidosis
