VIVA: Pathology - Environmental Flashcards
What are the major pathological consequences of IV drug use?
Thrombophlebitis
Sepsis (to injection site, lungs, heart valves, bones)
Viral inoculation (e.g. hepatitides, HIV)
ARDS
What are the features of IVDU endocarditis?
Affects 10% of hospitalised addicts
Distinctive form involving R-sided heart valves, especially tricuspid
Most are caused by Staphylococcus aureus
Other common organisms include fungi
Describe the organ system effects of lead poisoning
- CNS:
- Encephalopathy including headache, dizziness, memory disturbance and coma
- Impaired CNS development in foetus and infants - PNS:
- Peripheral neuropathy (impaired conduction) - Haematological:
- Microcytic hypochromic anaemia
- Haemolysis
- Characteristic basophilic stippling of red cells - Renal:
- Renal tubular injury - CVS:
- HTN - Genitourinary:
- Male infertility
- Failed ovum implantation
*3 systems with some details to pass
What regard to lead poisoning, what are the toxic mechanisms that operate?
- High affinity for sulfhydryl groups:
- Binds to gamma-aminilevuline acid dehydratase and ferroketolase, involved in haem synthesis - Competition with Ca2+ ions:
- Interferes with nerve transmission and brain development - Inhibition of membrane-associated enzymes including Na+/K+ ion pumps
Describe the clinical features of acute radiation syndrome
Features are dose-dependent:
- <200 rem: subclinical (mild N+V, minor neutropenia)
- 200-600 rem: haematopoietic (N+V, neutropenia maximal at 2 weeks, risk of infection)
- 600-1000 rem: gastrointestinal (N+V, diarrhoea, severe neutropenia, death from shock and infection within 2 weeks)
- >1000 rem: CNS (severe N+V, coma within 3hrs, no lymphocytes, death within 36hrs)
Describe some of the delayed effects of radiation injury
- Carcinogenesis*:
- Especially leukaemias and thyroid cancer in children - Blood vessels:
- Fibrosis, narrowing (leads to organ ischaemia) - Skin:
- Radiation dermatitis, impaired healing - Heart:
- Pericardial fibrosis leading to constrictive pericarditis - Lungs:
- Radiation pneumonitis with intra-alveolar and interstitial fibrosis - Kidneys and urinary tract:
- Peritubular fibrosis, loss of glomeruli, bladder fibrosis - GIT:
- Oesophagitis, gastritis, enteritis, colitis, proctitis, fibrosis leading to strictures and obstruction - Breast:
- Fibrosis - Ovary and testis:
- Fibrosis and infertility - Eyes:
- Cataracts - CNS:
- Transverse myelitis
*needed to pass + at least two other examples
Describe the effects of acute ionising radiation exposure
Sublethal doses:
- Delayed effects: mutations, chromosome aberrations, genetic instability
Larger doses:
- Kill proliferating cells: haematopoietic and GI systems most prone
- Vessel endothelial cell injury causes delayed organ dysfunction
Larger still:
- Overt tissue necrosis
Delayed consequences:
- Fibrosis (scarring when parenchymal cells can’t regenerate and when vessels are damaged)
Carcinogenesis:
- Skin, leukaemia, osteogenic sarcomas, lung cancer, thyroid cancer in children
By what mechanism does smoking contribute to emphysema?
Emphysema is a consequence of high protease (elastase) activity with low anti-protease (elastase) activity*
Smoking causes:
- Increased neutrophils and macrophages in alveoli
- Release of elastase from neutrophils
- Enhanced elastolytic activity in macrophages
- Inhibition of alpha-1 antitrypsin* (oxidants in smoke, oxygen free radicals from neutrophils)
*needed to pass
What cancers can smoking predispose to?
3 to pass:
- Oropharynx
- Larynx
- Lung
- Oesophagus
- Stomach
- Pancreas
- Bladder
What is sudden infant death syndrome?
The sudden death of an infant under 1 year of age which remains unexplained after thorough investigation and autopsy
What are the risk factors for sudden infant death syndrome?
Parental risks:
- Young mum <20yo
- Maternal smoking or drug use
- Low socioeconomic status
- Deficient prenatal care
Infant risks:
- Premature
- Low birth weight
- Male
- SIDS in sibling
- Brainstem anomalies
Environment:
- Prone sleeping
- Soft bedding and co-sleeping
- Hyperthermia
*at least 3 risk factors needed to pass
How are thermal burns classified?
According to depth of injury:
- Superficial *: confined to epidermis
- Partial thickness *: extends to dermis
- Full thickness *: involves subcutaneous tissue
*needed to pass
What are the potential complications of thermal burns?
Early*:
- Hypovolaemic shock (especially with >20% BSA)
- Compartment syndrome with circumferential LL burns
- Associated injuries (e.g. inhalational burns, CO poisoning)
- Airway oedema and compromise
- Hypermetabolic state
Late*:
- Infection / sepsis (Pseudomonas is a common pathogen)
- ARDS
- Multi-organ failure
- Skin grafting, scarring / cosmetic concerns
- Psychological
*2 early and 2 late to pass
How do you determine the extent of burns
TBSA calculation notoriously inaccurate
Does not include superficial burns
Can use Wallace “rule of nines” or Lund & Browder diagram *
For smaller burns can use size of patient’s palm to estimate (~1% BSA)
*one method needed to pass
What are the pathological consequences of thiamine deficiency?
2 needed to pass with some details:
- Dry beriberi: symmetric peripheral polyneuropathy (myelin degeneration leading to axonal disruption in motor and sensory fibres, and reflex arcs)
- Wet beriberi: high output cardiac failure with peripheral vasodilation and AV shunting, may get dilated cardiomyopathy
- Wernicke-Korsakoff syndrome: Wernicke’s encephalopathy (ophthalmoplegia, nystagmus, ataxia, higher centre dysfunction) and Korsakoff’s psychosis (permanent impairment of remote recall, confabulation)
