From StudyingMed

< SH3‎ | Lectures
Jump to: navigation, search

Organophosphates

Look at the slides because he didn't get to go through them

  • Toxicology is a disease of underregulation e.g. developing world, pesticides, water quality, food quality etc
  • Public health research + work is all in the places that need it least based on burden of disease
  • Poisoning globally is largely via deliberate self poisioning (300/100,000 per year). Higher chance of dying outside Australia
    • Largely impulsive
    • Suicide implies intent - but it's usually an accident due to taking risks. Most suicide is due to a deliberate impulsive act that goes wrong
  • Sri Lanka - suicide rates increased with pesticides and banning pesticides has reduced suicide rates; this solution could be replicated around the world and drop suicide rates globally by 25%
    • Solution to the problem is not psychiatric - it is sociological and environmental. Psychiatry has no effect in suicide rates (?)
  • China - 57% drop in suicides driven by reduced toxicity - no depression intervention has ever changed suicide rate like that (suicide is based on impulsivity)
  • Toxic person: HR 125, SaO2 = 61%, paradoxical breathing (abdomen goes out when breathing in)
    • Flickering eyes: organophosphate poisoning (AChE inhibitors - affect NMJ)
      • Like carbamates/organophosphates (AChE inhibitors) for treating myasthenia gravis
    • Pesticide poisoning
  • Availability drives lethality and poisoning
  • 1/4 of beds in Sri Lankan hospitals are poisoning or snakebite. Sometimes there are so many poisonings you have to put two in a bed
  • Sri Lanka: they use gastric lavage (which is NOT indicated here) - 7 aspiration pneumonia and 2 deaths.
    • Basically people being killed by doctors
  • People use diuretics to treat poisoning because they're foaming at the mouth - this is wrong for pesticide poisoning
  • There are better ways to approach this from public health approach - so you can achieve a lot in the developing world based on public health interventions (which are cheap)
  • 2/3 of poisoning events are driven by alcohol (but underreporting from females means this could be underestimated)
  • Organophosphates are nerve agents - chemical weapons, easy to make and toxic. They bind to AChE and inactivate it. Most of the ones used for insects require activation (insects have high metabolic rate so it is more active in them)
  • AChE is important for normal communication between nerves and other nerves, glands, muscles etc
    • AChE treatment for Alzheimers only blocks 30% of activity.
  • Microscope = showing ACh in the NMJ
    • ACh is a neurotransmitter, and after a depolarisation, AChE has to mop it up.
    • OP binding to AChE causes ACh to accumulate --> too much firing
    • Firing occurs in skeletal muscle, brain (disordered respiratory centre output), affects vasoconstriction/dilatation (can cause either up or down HR and BP), sweat and produce a lot of secretions
    • = acute cholinergic crisis
    • Constantly stimulating something causes it to switch off -- causing weakness rather than activity
  • Anticholinergic poisoning = hot, dry (bladder retention), mad, pupil dilatation
    • Treatment:carbamate
  • See the slides for cholinergic poisoning
    • A lot of secretions = frothing at the mouth. Lungs fill with fluid - people drown to death. A diuretic is not useful in removing excess lung fluid
  • Treatment for cholinergic poisoning
    • Atropine, to block ACh. This will dry up secretions
    • Normal dose of atropine is 0.5mg, in OP poisoning you may need 500mg/hour (need to block a lot to get control of secretion - measure it by looking at the person)
      • E.g. anticholinergic drugs used in asthma (low doses), here we do the same thing but in high doses: dry up lungs, reduce bronchoconstriction
        • Cambridge guy halved the death rate in Sri Lanka due to poisoning by bringing in appropriate treatment for poisonings
  • In rats, OPs are teratogenic (neurologically) - in India they cover pregnant people with the stuff. Environmental exposure to pesticides is widespread - health consequences not known since they're not studied
  • In Australia, we use small bottles, and PPE. In the developing world, we have large amounts of banned pesticides with no PPE
  • Industry at most levels is trying to increase the use of pesticides rather than reduce it
  • It's often not in the original bottle and people don't even know they're using it

Arsenic

  • Bangladesh, Vietnam, China
  • There are water wells full of arsenic
  • Red area in Bangladesh is the most populous and has >20x the acceptable rate of Arsenic
  • In China they have it due to coal mining
  • Derm: causes hyperkeratosis (increased thickening on palms and soles of feet)
    • This is caused by arsenic poisoning in the water
    • The problem has not been solved yet
    • More insidiously it affects blood vessels - causes gangrene, skin cancers
  • There are outbreaks of CKD of unknown cause in Sri Lanka, but there is no discovered toxicological explanation
    • Some rates are 50x the background rate
    • River - one side of the river is poisoned, the other side is not. Suggests waterborne problem
  • Their dam system can increase poisonous concentrations
    • Possibly due to cyanobacteria?
  • Function of regulation and measurement

Snakebite in Sri Lanka

  • Very small but dangerous snakes, and inject 50x as much venom as an Australian brown snake
  • High deathrate in poor countries - don't have good healthcare (in Australia it is very hard to die of snakebite). We have quality antivenoms and ventilators for paralysis
  • Women are frequently not taken to hospital - too expensive
  • Function of living standards

GHB poisoning

  • Gamma hydroxybutyrate (GHB) poisoning - due to sucking toy beads
    • All came from China - they had poor regulation and switched precursor chemicals