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Acid Base Jeopardy Steve Wood, PhD, UNM School of Medicine

Acid Base Jeopardy Steve Wood, PhD, UNM School of Medicine View in slide show mode with speakers on – click on your choice for correct answer to hear if you’re right . Clinical. Renal. Physiology. pH. 100. 100. 100. 100. 200. 200. 200. 200. 300. 300. 300. 300. 400. 400. 400.

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Acid Base Jeopardy Steve Wood, PhD, UNM School of Medicine

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  1. Acid Base Jeopardy Steve Wood, PhD, UNM School of Medicine View in slide show mode with speakers on – click on your choice for correct answer to hear if you’re right Clinical Renal Physiology pH 100 100 100 100 200 200 200 200 300 300 300 300 400 400 400 400 500 500 500 500 1000 1000 1000 1000 2000 2000 2000 2000 3000 3000 3000 3000 4000 4000 5000 5000 5000

  2. explanation

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  8. The diuretic acetylzolamide (diamox) inhibits the • enzyme carbonic anhydrase. Which of the following data sets shows the expected effects of this drug on pH and renal function? explanation

  9. Acetylzolamide (diamox) is an inhibitor of carbonic anhydrase. Predictable side-effects effects of diamox treatment would include: • Diuresis and acidification of urine, decreased blood PCO2 • Antidiuresis, decreased blood Na+ and PCO2 • Increased Na+ excretion, diuresis, alkalinization of urine, decreased blood pH • Diuresis, increased H+secretion, no change in blood PCO2 explanation

  10. explanation

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  15. A buffer system; e.g., « + - HA H + A is most effective when: A. [HA] > [A ] - B. [HA] < [A ] - C. [HA] = [A ] - D. pH > pK

  16. The defense against acid load with the slowest response time is: • Chemical buffering • Renal compensation • Respiratory compensation • Hemoglobin proton coupling

  17. The acid base status of a pregnant woman in • the 3rd trimester is best depicted by point___. • A) 3 • 4 • C) 7 • D) 2 • E) 6

  18. A normal rate of bicarbonate reabsorption in the renal tubule cells requires the enzyme: • Carbonic anhydrase • Lactate dehydrogenase • Tyrosine hydroxylase • Carbonate reductase

  19. The most important mechanism of hydrogen secretion in the proximal tubule is: • H+ ATPase (electrogenic H pump) • H+ - K+ antiporter • Na+ - H+ antiporter • diffusion

  20. Lab results for a 24 hour urine sample show: Titratable acid = 20 mEq [NH4+] = 40 mEq [HCO3-] = 3 mEqThe patient’s net acid excretion is: • 63 mEq/day • 20 mEq/day • 57 mEq/day • 23 mEq/day

  21. The inhibition of ventilation by metabolic alkalosis is countered (partially reversed) by the stimulation of ventilation due to: • pH increases • hypercapnia • hypoxia • low bicarbonate

  22. COPD patient in respiratory failure. ABG report: PaO2 = 35 mm Hg PaCO2 = 64 mm Hg pH = 7.2 Hb = 10 g/dL Sat. = 60 % HCO3- = 26 mEq/L Base excess = 0 mEq/L • Acid base status is most accurately described as: • Uncompensated metabolic acidosis • Uncompensated respiratory acidosis • Compensated respiratory acidosis • Compensated metabolic acidosis explanation

  23. Room Air 100% oxygen PO2 mm Hg 43 mm Hg 452 mm Hg PCO2 mm Hg 16 mm Hg 34 pH HCO3- 7.50 15 7.32 17 4. COPD patient with with cyanosis and marked peripheral edema. ABG report: The patient’s acid base status on room air is: • Compensated respiratory alkalosis • Uncompensated respiratory alkalosis • Uncompensated metabolic alkalosis • Compensated metabolic alkalosis explanation

  24. A COPD patient who is an alcoholic is admitted to the ER after losing consciousness at home. ABG shows pH = 7.2 PCO2 = 52 mm Hg HCO3- = 18 mmEq/L PaO2 = 81 mm Hg The patient’s acid base status is: • Normal • Respiratory + metabolic acidosis • Respiratory acidosis • Metabolic acidosis + resp. alkalosis • Metabolic alkalosis

  25. During an operation, the arterial PCO2 and pH of an anesthetized patient are monitored. The patient is being ventilated by a mechanical respirator, and the initial values are normal (PCO2 = 40 mm Hg; pH = 7.41). If the ventilation is increased, which of the following is most likely to occur? • Arterial PCO2 • Decrease • Decrease • Decrease • Increase • Increase • Increase • Arterial pH • Decrease • Increase • No change • Decrease • Increase • No change explanation

  26. A patient excretes 3 L of urine with a pH of 7.6 with a [HCO3-] = 24 mEq/L. What is the net acid excretion? • 24 mEq/L • 48 mEq/L • Negative • Can not tell from these data explanation

  27. Lab results for a patient with DKA show a [HCO3-] = 10 mEq/L, PCO2 = 33 mm Hg. You forgot your calculator and impress the chief resident by telling her that you used the Henderson-Hasselbalch equation to calculate a pH = _______. • 7.4 • 6.8 • 6.1 • 7.1 explanation

  28. Lab results for a patient with respiratory failure and cholera show a [HCO3-] = 2 mEq/L, PCO2 = 66 mm Hg. You forgot your calculator and impress the chief resident by telling her that you used the Henderson-Hasselbalch equation to calculate a pH = _______. • 7.4 • 6.8 • 6.1 • 7.1 explanation

  29. Daily Double

  30. Daily Double

  31. Daily Double

  32. Final Jeopardy

  33. Use a bicarb – pH diagram to plot the course of a triple disorder in an alcoholic with ketoacidosis who develops hyperventilation from liver failure and then starts to vomit.

  34. PCO PCO PCO (mm Hg) (mm Hg) (mm Hg) 2 2 2 120 120 120 80 80 80 60 60 60 40 40 40 30 30 30 20 20 20 ] (mEq/L) ] (mEq/L) ] (mEq/L) 9 3 40 40 40 15 15 15 - - - 3 3 3 10 30 30 30 5 1 8 4 Plasma [HCO Plasma [HCO Plasma [HCO 20 20 20 2 6 7 10 10 10 6.8 7.0 7.2 7.4 7.6 7.8 8.0 6.8 7.0 7.2 7.4 7.6 7.8 8.0 6.8 7.0 7.2 7.4 7.6 7.8 8.0 pH pH pH 9 3 10 5 1 8 4 2 6 7 The diagram above shows plasma bicarbonate as a function of pH at different PCO2 levels. The two points that represent “mixed” acid base disorders are: • 2 and 6 • 4 and 7 • 8 and 10 • 8 and 9 explanation

  35. Filtered load = GFR x plasma concentration = 180 L/day x 24 mEq/L = 4320 mEq/day

  36. Alkalosis will inhibit the central and peripheral Chemoreceptors causing hypoventilation and increased PCO2, which will cause alveolar and arterial PO2 to Decrease. This will stimulate the carotid body PO2 receptor Which will oppose the inhibition by alkalosis. Also, the Increased PCO2 will compensate the alkalosis. Systemic alkalosis causes vasoconstriction in most vascular Beds. This may be countered by the hypoxia in some beds But normally there is cerebral and coronary vasoconstriction. Alkalosis caused decreased extra and intracellular calcium Leading to prolonged action potentials and muscle spasm (tetany).

  37. urine may be alkaline as well as acidic, depending on diet and/or compensation for alkalosis. citrus fruits, due to high amounts of citrate will produce alkaline urine. citrate is metabolized to citric acid by adding a hydrogen ion. this makes blood, and urine, more alkaline. compensation for metabolic alkalosis is both respiratory and by renal excretion of bicarbonate.

  38. Acidosis inhibits the slow calcium channels which are activated during phase 2 of the cardiac action potential. in addition, tissue acidosis causes hydrogen in and potassium out of cells leading to hyperpolarization (more negative membrane potential). The force of contraction is directly dependent on the magnitude of the initial calcium influx, therefore acidosis decreases the force of contraction. For more http://www.accessmedicine.com/content.aspx?aID=889838 Used id = rossmed password = rossmed

  39. CA is present in both the brush border of the luminal membrane and in the cytoplasm. nahco3 uptake from filtrate is inhibited so hco3- reabsorption is blocked leading to higher urine ph and lower blood ph http://www.accessmedicine.com/content.aspx?aID=943477&searchStr=acetazolamide

  40. anion gap = NA – (CL + HCO3-) = 135 – 118 = 17 mEq/l pH = 7.35 so acidosis. what kind? has to be metabolic since pco2 is low, not high. PCO2 is down by 6 to partially compensate for HCO3- being down by 6 (which would predict that ph would be 7.3 and instead it is 7.35 due to partial respiratory compensation

  41. pH = 7.29 = acidosis PCO2 = 27 mmHg, so you know it’s metabolic acidosis and hyper Ventilation is compensatory HCO3- = so you also know it is metabolic acidosis

  42. The concentration of free hydrogen ion is so small it is measured in nanomoles (a nanomole is a billionth of a mole) A pH of 7.4 = 40 nmoles/L (extracellular) A pH of 7.0 is 100 nmoles/L (typical intracellular)

  43. The renal tubule cells normally secrete enough hydrogen ion to completely reabsorb all the filtered bicarb (4320 mEq/L) PLUS enough extra to produce new bicarb to replace that lost in buffering fixed acid from metabolism (80 mEq/L) for a total of 4400 mEq/L

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