Question 1: A patient appears in the ER. He is hyperventilating and his blood pH

Question

Question 1: A patient appears in the ER. He is hyperventilating and his blood pH is 7.6. It turns out he has taken an accidental overdose of aspirin. Aspirin is Acetylsalicylic acid. In the stomach it is hydrolyzed to acetic acid and salicylic acid. The salicylic acid acts on the central nervous system to increase respiration rates. a)What does hyperventilation do to the pH of the blood stream? b)Why? c)Patients suffering from an aspirin overdose are treated with activated charcoal to absorb the aspirin. Sodium bicarbonate is also given when the stomach is pumped to increase the solubility of the salicylic acid in the stomach. Why does this help? Hint: the pKa of salicylic acid is 3.0 and the pH of stomach is about 2. What is the fraction of salicylic acid that is charged at pH 2 and pH-7?

Explanation / Answer

a) Hyperventilation is a condition in which we start to exhale more than inhale and hence disturb the balance . And hence more loss of CO2 than the body produce results in rising the ph of blood .

b) since CO2 reacts with water to form carbonic acid in equilibrium and decrease in pressure of CO2 results in more decomposition of h2co3 and hence making the solution less acidic and more basic. This increase in ph increases the haemoglobin affinity for oxygen through Bohr effect.

c)Aspirin poisoning can be treated with activated charcoal as it will absorb the salicylate from the stomach .

Sodium bicarbonate are added to make the blood and urine more basic so that kidneys capture more salicylate that can leave the body through urine.

Using Henderson equation we can calculate the fraction

-pka = - ph + log( A^-/ HA)

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