Page 257 - Textbook of Pathology, 6th Edition

burning of fossil fuel in industries or at home; and 241
tobacco smoke.
CO is an important cause of accidental death due to
systemic oxygen deprivation of tissues. This is because
haemoglobin has about 200-times higher affinity for CO than
for O and thus varying amount of carboxyhaemoglobin is CHAPTER 9
2
formed depending upon the extent of CO poisoning. Besides,
carboxyhaemoglobin interferes with the release of O from
2
oxyhaemoglobin causing further aggravation of tissue
hypoxia. Diagnosis of CO poisoning is, therefore, best
confirmed by carboxyhaemoglobin levels in the blood.
CO poisoning may present in 2 ways:
Acute CO poisoning in which there is sudden
development of brain hypoxia characterised by oedema and
petechial haemorrhages.
Chronic CO poisoning presents with nonspecific changes
of slowly developing hypoxia of the brain.

DRUG ABUSE Environmental and Nutritional Diseases
Drug abuse is defined as the use of certain drugs for the
purpose of ‘mood alteration’ or ‘euphoria’ or ‘kick’ but
subsequently leading to habit-forming, dependence and
Figure 9.5 Complications of lead poisoning.
eventually addiction. Some of the commonly abused drugs
and substances are as under:
b) Brain, liver, kidneys and bone marrow accumulate the 1. Marijuana or ‘pot’ is psychoactive substance most widely
remaining 10% lead which is directly toxic to these organs.
It is excreted via kidneys. used. It is obtained from the leaves of the plant Cannabis sativa
and contains tetrahydrocannabinol (THC). It may be smoked
Lead toxicity occurs in the following organs predo-
minantly: or ingested.
2. Derivatives of opium that includes heroin and morphine.
1. Nervous system: The changes are as under: Opioids are derived from the poppy plant. Heroin and
In children, lead encephalopathy; oedema of brain, morphine are self-administered intravenously or
flattening of gyri and compression of ventricles. subcutaneously.
In adults, demyelinating peripheral motor neuropathy 3. CNS depressants include barbiturates, tranquilisers and
which typically affects radial and peroneal nerves resulting alcohol.
in wristdrop and footdrop respectively. 4. CNS stimulants e.g. cocaine and amphetamines.
2. Haematopoietic system: The changes in blood are quite 5. Psychedelic drugs (meaning enjoyable perception-giving)
characteristic: e.g. LSD.
Microcytic hypochromic anaemia due to inhibition of two 6. lnhalants e.g. glue, paint thinner, nail polish remover,
enzymes: delta-aminolevulinic acid dehydrogenase required aerosols, amyl nitrite.
for haem synthesis, and through inhibition of ferroketolase It is beyond the scope of the present discussion to go into
required for incorporation of ferrous iron into the porphyrin the pharmacologic actions of all these substances. However,
ring. apart from pharmacologic and physiologic actions of these
Prominent basophilic stippling of erythrocytes. street drugs, the most common complication is introduction
of infection by parenteral use of many of these drugs. Sharing
3. Kidneys: Lead is toxic to proximal tubular cells of the
kidney and produces lead nephropathy characterised by of needles by the drug-addicts accounts for high risk of most
accumulation of intranuclear inclusion bodies consisting of feared viral infections in them, AIDS and viral hepatitis (both
lead-protein complex in the proximal tubular cells. HBV and HCV). Following are a few common drug abuse-
related infectious complications:
4. Gastrointestinal tract: Lead toxicity in the bowel 1. At the site of injection—cellulitis, abscesses, ulcers,
manifests as acute abdomen presenting as lead colic.
thrombosed veins
2. Thrombophlebitis
CARBON MONOXIDE POISONING
3. Bacterial endocarditis
Carbon monoxide (CO) is a colourless and odourless gas 4. High risk for AIDS
produced by incomplete combustion of carbon. Sources of 5. Viral hepatitis and its complications
CO gas are: 6. Focal glomerulonephritis
automobile exhaust; 7. Talc (foreign body) granuloma formation in the lungs.