Question

A patient has just been admitted 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, i.e. over breathing. The patient accidentally took an entire bottle of aspirin, which contained 250 tablets, around 7 pm that evening. Blood from the patient is analysed and the analyses shown in Table 1. The patient is experiencing mild respiratory alkalosis.

Table 1: Arterial blood gas concentration in patient Patient, two hours after aspirin ingestionafter aspirin ingestion Patient, ten hoursNormal values Pco2 HCO3 Po pHI Blood salicylate 19 mm Hg 26 mm Hg 18 mM 113 mm Hg 35-45 mm Hg 22-26 mM 75-100 mm Hg 7.35-7.45 21 mM 143 mm Hg 02 7.44 7.55 57 concentration, mg/dL

In the emergency room, the patient is given a stomach lavage with saline 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. A gastric lavage at pH = 8.5 and further activated charcoal treatments are administered, one every 30 minutes. A bicarbonate 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 after the ingestion.

Aspirin is chemically acetyl salicylic acid, which is converted to salicylic acid (a weak acid with pKa = 2.97) in the stomach, which can ionise to form the salicylate ion.

Q1: At pH 2.0 in the stomach, what is the charge on this weak acid ?

Q2: At pH 8.5, what is the charge on this weak acid? It has been shown that salicylates act directly on the nervous system to stimulate respiration. Thus, the patient is hyperventilating due to her salicylate overdose.

Q3: What is the change in O2 level, due to aspirin ingestion, compared to normal?

Q4: After 10 hours of aspirin overdose, how would the blood pH value be described, compared to normal?

Q5: What is the effect of the bicarbonate drip on blood pH?

Answer 1

Sclution Gaven As doncenlootion n Takent Cancor an d amd Saiculin aud он aa d Buro

Aepisun Converte a t Sal cal acet nd ck S eak aud tohch n Slenm.ch nveoSlkalals ten amdea Sade& Contain nd n Сон он Hudobopm bondin (tHt -loondia) C Saliculae ron) belourg

Umpscterated Csim s the LUmpocke altu totll C3) ingeton a dus o eneaton sun Loas due to 9uyi9olosu alkalogs

u. (5) BiCorberaihop ottl help to eHon ataint the blcod nd ap