Physio 9

Question 1

metabolic lines on the davenport graph

Answer 1

isobars that describe the changes in pH and bicarbonate that occur when acid or base is added at a constant PCO2.

Question 2

respiratory line

Answer 2

if at each value of PCO2, the corresponding values of [HCO3-] and pH from the CO2 absorption curve are marked on the davenport graph, the resulting line is known as a respiratory line. this line represents the effect of pulmonary ventilation on blood pH and bicarbonate

Question 3

respiratory acidosis

Answer 3

upper left quadrant of the davenport graph. decreased pH due to increased PCO2. caused by hypoventilation.

Question 4

renal compensation in respiratory acidosis

Answer 4

during respiratory acidosis, bicarbonate is increasing while pH is falling. in compensation by the kidney, bicarb increases further while pH rises. this shows that the pH depends on the proton concentration, NOT the concentration of bicarb. the kidney increases reabsorption of HCO3- and increases the excretion of acid

Question 5

respiratory alkalosis

Answer 5

bottom right quadrant of the davenport graph. caused by hyperventilation. increased pH with decreased PCO2. leads to decrease in cerebral blood flow which results in lightheadedness and an inability to concentrate

Question 6

renal compensation in respiratory alkalosis

Answer 6

decrease reabsorption of HCO3 and to retain acid, thereby acidifying the body and alkalinizing the urine. involves a decreased excretion of NH4Cl and other titratable acids. this is the only acid/base disorder in which renal compensation can completely normalize the blood pH

Question 7

metabolic acidosis

Answer 7

increased pH with increased bicarb. upper right quadrant of the davenport graph. caused by excess vomiting, which involves loss of water and acid from the stomach. renal response is a decrease in reabsorption of HCO3.

Question 8

pathway used by excess diuretics causing volume contraction and metabolic alkalosis

Answer 8

excess diuretics –> loss of NaCl and fluid –> increased renin/angiotensin/aldosterone response –> increased renal proton secretion –> increased plasma bicarbonate

Question 9

metabolic acidosis

Answer 9

lower left quadrant on the davenport graph. decreased pH with decreased bicarb. caused by excessive overproduction or exogenous overload leading to accumulation of acid in the blood. underexcretion of acid by the kidneys, or excessive renal excretion of bicarb, or GI loss of bicarb. can happen due to being poisoned or diabetes mellitus

Question 10

causes of metabolic acidosis

Answer 10

anion gap: increased organic anions, decreased HCO3. Diabetes, poisoning, lactic acid

hyperchloremic: increased Cl-, decreased HCO3. happens in severe diarrhea, and uremias (proximal renal tubule acidosis, distal renal tubular acidosis)

Question 11

base excess

Answer 11

amount of HCO3 that should be added or subtracted to bring the patient back to normal. it is a positive number in alkalosis, and a negative number in acidosis.

Question 12

henderson hasselbach equation for bicarb

Answer 12

[HCO3-] = 0.03PCO2 x 10^(pH-6.1)