DrVirgo
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40. A 22-year-old woman is brought to the emergency department unconscious 30 minutes after sustaining multiple injuries in a motor vehicle collision. Her temperature is 36°C (96.8°F), pulse is 82/min, respirations are 6/min, and blood pressure is 110/75 mm Hg. Physical examination shows significant head trauma with a depressed segment of parietal bone. Arterial blood gas analysis on room air shows: pH 7.17
PC O2 80 mm Hg
P O2 50 mm Hg
HCO3ˆ’ 28 mEq/L A. Which of the following renal compensatory responses will occur in this patient?
B. Decreased H+ secretion into the tubule
C. Decreased proximal tubule HCO3- reabsorption
D. Decreased titratable acid excretion
E. Increased HCO3- excretion
F. Increased NH4Cl excretion
F?
(I picked by exclusion, because all others would lead to MORE acidosis instead of compensation to increase pH, but if you agree with F can you please explain?- Thanks)
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| vallia
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all right first of all you have to think about the main problem causing this. It's a global respiratory failure, which means that P CO2 will increase and P O2 will decrease. Focusing just on the P CO2 increase. It will produce acidosis, respiratory acidosis. This can be compensated by the activation of the renal mechanism. These mechanisms include the production of HCO3 which is reabsorbed into the blood and the secretion of H+. The hydrogen ions cannot be excreted as they are so they will be coupled with NH3 which is excreted by the kidneys and NH4+ formed in the tubules will be coupled with the Cl- which was freed from NaCl. Na enters the tubular cell replacing the H+ in the H2CO3.The NaHCO3 will be then transported to the blood compensating the pH also.
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| robin082006
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good explanation
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