Biology of Disease

SUMMARY

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12.6 Summary

The body is exposed daily to many chemicals, some of which have the
potential for harm. These chemicals may be ingested with food and drink,
they may be therapeutic or recreational drugs or they may be toxins from
microorganisms or the abiotic environment. Xenobiotics may be detoxified
in the liver, by conversion to more water-soluble compounds, which are then
excreted through the kidneys. Sometimes this process results in more harmful
compounds being produced, as is the case with paracetamol poisoning.
Clinical investigations of suspected poisoning include liver function tests,
analysis of blood gases and determination of acid–base status.

The commonest cases of poisoning involve accidental or deliberate overdose
with common analgesics such as paracetamol or aspirin but abuse of alcohol
is an increasing problem in developed countries, leading to liver damage in
the patient. In addition, carbon monoxide poisoning may be insidious and
fatal, in badly ventilated houses warmed by faulty gas heaters. Treatment of
poisoning first involves identification and removal of the poison; thereafter
treatment depends on the nature of the poison involved. Unfortunately, some
poisons, such as paraquat, are invariably fatal.

QUESTIONS

1. Which of the following produces a combination of respiratory
   alkalosis and metabolic acidosis?

(a) paracetamol poisoning;

(b) ethylene glycol poisoning;

(c) aspirin poisoning;

(d) lead poisoning;

(e) carbon monoxide.

2. Which of the following is the toxin produced during paracetamol
   poisoning?

(a) paracetamol-3-mercapturic acid;

(b) glutathione;

(c) N-acetylbenzoquinoneimine;

(d) UDP-glucuronyl transferase;

(e) trimethylarsine.

CASE STUDY 12.4

John’s girlfriend found him in his closed garage

unconscious in his car with the engine running. He was

taken to the hospital immediately. The following blood

results were obtained (reference ranges are shown in

parentheses).

H+ 50 nmol dm–3 (36–46 nmol dm–3)

HCO 3 – 15 mmol dm–3 (22–30 mmol dm–3)

PCO 2 3.5 kPa (4.5–6.0 kPa)

Hemoglobin 150 g dm–3 (130–180 g dm–3)

Lactate 10 mmol dm–3 (0.65–2.0 mmol dm–3)

Questions

(a) Suggest a plausible explanation for these data?

(b) How should John be treated?