Question

Background info: (Images)

Background You are an emergency room physician and you have just admitted a patient, a 23-year-old female, who had been hospitalized for psychiatric treatment for the past six months. She was out on a day pass when she was brought to the emergency room around 9 pm. The patient was disoriented, had trouble speaking, and was suffering from nausea and vomiting. She was also hyperventilating. The patient admitted to taking an entire bottle of aspirin, which contained 250 tablets. The patient said that she took the tablets around 7 pm that evening. You draw blood from the patient and the laboratory performs the analyses shown in Table 1. The patient is experiencing mild respiratory alkalosis. Table 1: Arterial blood gas concentration in patient Two hours after aspirin Ten hours after aspirin ingestion ingestion Normal values Partial Pressure CO2 26 mm Hg 19 mm Hg 35-45 mm Hg Partial Pressure 02 113 mm Hg 143 mm Hg 75-100 mm Hg Bicarbonate (HCO3] 18 mM 21 mm 22-26 mM PH 7.44 7.55 7.35-7.45 Blood salicylate concentration, mg/dL 57 117 In the emergency room, the patient is given a stomach lavage (gastric irrigation and pumping) with saline (salt) solution and two doses of activated charcoal to adsorb the aspirin. Eight hours later, nausea and vomiting became severe, and her respiratory rate increased; she was in severe respiratory alkalosis, and further treatment was required. You carry out a stomach lavage at pH = 8.5 and administer further activated charcoal treatments, once every 30 minutes. Respiratory alkalosis also triggers excretion of potassium and sodium bicarbonate through the kidneys. An intravenous bicarbonate (HCO3) drip was required to prevent the blood bicarbonate concentration from dropping below 15 mM. After 12 hours, blood salicylate concentrations began to decrease. The patient's blood pH begins to drop around 24 hours after the aspirin ingestion and finally returned to normal at 60 hours, although salicylate concentrations did not fall to zero until about 80 hours after aspirin ingestion.

The images above are background info. Please answer the following question: (4)

4. It has been shown that aspirin acts directly on the nervous system to stimulate respiration. Thus, our patient is hyperventilating due to her aspirin overdose.

b. Explain how aspirin-induced hyperventilation causes the pH of the patient’s blood to increase. (Hint: what acid/base pair is the blood’s main buffering system?

Answer 1

Answer 4

Aspirin-induced hyperventilation causes the pH of patients to rise

reasons

Steps

1- As we know Aspirin acts directly on the nervous system to stimulate respiration

2- the overdose of Aspirin thus results in hyperventilation

3- hyperventilation ( increase in the rate of breathing or tidal volume of breathing) causes more eliminations of carbon dioxide than the body produces

4- so it leads to hypocapnia ( I.e reduced CO2 concentration in blood)

5- This alters the bicarbonate buffer system.

( the most of CO2 molecules (85 percent) are carried as part of the bicarbonate buffer system.

In which carbon dioxide diffuses into the red blood cells. Where carbonic anhydrase converts CO2 into carbonic acid and carried via blood to the lungs for eliminations

CO2+H2O---->H2CO3(carbonic acid)---->HCO3^-(bicarbonate ions) + H+

Here H+ ions help to control pH)

6 - As a result, fewer H+ ions will produce (due to less CO2 in blood)

7- finally results in respiratory alkalosis.

Acid-base pair of blood main buffering system is

carbonic acid(H ₂CO ₃) and bicarbonate anion (HCO ₃^-)