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1. In which of the following fluids is the pH highest (most alkaline)? (Assume the person is normal.) A. systemic arterial blood plasma B. systemic venous blood plasma C. urine D. all of the above, since pH is normally of the same for all E. A and B above, since blood plasma pH is relatively uniform 2. The ammonium (NH4+) ion that may be present in urine is produced by A. breakdown of urea in the liver B. metabolism of amino acids in the renal tubule and collecting duct C. aerobic carbohydrate metabolism D. gylcolytic pathways during anaerobic metabolism E. gluconeogensis during starvation 3. The reason that respiratory compensation for metabolic alkalosis can never be complete (return plasma pH to normal) is that (Note: PaCO2 = systemic arterial carbon dioxide partial pressure.) A. high PaCO2 inhibits respiratory ventilation B. high PaCO2 stimulates respiratory ventilation C. low PaCO2 inhibits respiratory ventilation D. low PaCO2 stimulates respiratory ventilation E. none of the above, since respiratory compensation for metabolic alkalosis can be complete 4. The appearance of large amounts of ammonium ion (NH4+) in the urine is characteristic of the renal response to A. B. C. D. E. respiratory acidosis respiratory alkalosis acidosis resulting from pancreatic diabetes alkalosis resulting from gastric vomiting both A and C above 5. An individual hoping for an LSD "acid high" mistakenly gives himself an intravenous injection of hydrochloric acid. The responses of his body which attempt to compensate for this ignorance of physiology include all of the following except A. B. C. D. E. hyperventilation increase in the acid form of the blood fixed buffers decrease in blood bicarbonate ion concentration increase in urine bicarbonate ion excretion increase in urine ammonium ion excretion 6. A systemic arterial blood sample taken from the above individual an hour after his HCl "adventure" might show which of the following? A. B. C. D. E. base base base base base excess excess excess excess excess = = = = = +10 meq/liter; PaCO2 +10 meq/liter; PaCO2 -10 meq/liter; PaCO2 -10 meq/liter; PaCO2 0 meq/liter; PaCO2 = = 50 mmHg = 30 mmHg = 50 mmHg = 30 mmHg 40 mmHg 7. A young woman is found comatose, having taken an unknown number of sleeping pills an unknown time before. An arterial blood sample yields the following values: pH HCO3PaCO2 7.02 14 meq/liter 68 mmHg This patient's acid-base status is most accurately described as A. B. C. D. E. uncompensated metabolic acidosis uncompensated respiratory acidosis simultaneous respiratory and metabolic acidosis respiratory acidosis with partial renal compensation respiratory acidosis with complete renal compensation ANSWERS 1. A. Systemic arterial blood has a higher (more alkaline) pH than systemic venous blood because of the CO2 added by metabolizing cells as blood passes through the systemic vascular beds. Urine is generally more acid than plasma because of the necessity of excreting the excess fixed (non-volatile) acids created by metabolism. 2. B. 3. B. Respiratory compensation for metabolic alkalosis involves depression of alveolar ventilation to accumulate CO2. However, the higher PaCO2 stimulates ventilation, which prevents complete compensation (return of pH to 7.4). 4. E. Renal compensation for acidosis, of both respiratory and metabolic origin (assuming the metabolic acidosis is not due to renal pathology), involves synthesis of NH3 and subsequent excretion of NH4+. 5. D. Renal compensation for acidosis involves bicarbonate reabsorption, not bicarbonate excretion. 6. D. After an hour, we should expect respiratory compensation but not renal compensation. Thus, there will be a negative base excess due to the acid injection and low PaCO2 due to the hyperventilation. 7. C. The low pH indicates acidosis. The low bicarbonate indicates metabolic acidosis. The high PaCO2indicates respiratory acidosis. Presumably, the narcotic overdose depressed the patient's respiratory center in the brain, reducing ventilation. The reduction of available oxygen then caused cellular anaerobic metabolism to increase, leading to production of lactic acid, etc.