Organophosphate Poisoning Flashcards
What is an organophosphate and some of its uses
Nerve agent in chemical warfare
Insecticide
Potent cholinesterase inhibitor capable of causing severe cholinergic toxicity after ingesting , inhaling or cutaneous exposure
Classification of organophosphate and examples
Based on toxicity / potency
1 highly - parathion
2 intermediate - coumaphos
3 mild - malathion
Mechanism of action of organophosphates and effects
- bind to acetylcholinesterase and render it non-functional
- over abundance of AcH at neuronal synapses and NMJ
- overstimulation of muscarinic and nicotinic receptors
- aging ( conformational changes of AcHE-organophosphate over time and resistant to re-activation by anidotal oxime
Effects of organophosphates to Parasympathetic Sympathetic Somatic CNS Systems
- bradycardia , smooth muscle contraction, bronchoconstriction
- tachycardia, bronchodilaton , diophoresis ,
- fascinations , weakness ,
- coma , seizure , confusion , agitation , anxiety
What do clinical features of organophosphates depend on and onset times
1 rate of AcHE inhibition
2 route of absorption
3 lipophilicity of organophosphates
4 enzymatic conversion to active metabolites
1 oral / respiratory exposure - 3 hours
2 dermis - 5 hours
3 lipophilic - delayed up to 5 days
What are muscarinic and nicotinic receptors
1 G protein coupled receptors involved in parasympathetic nervous system
2 AcH receptors which stimulate sympathetic and somatic nervous system
What are the muscarinic effects of organophosphates
SLUDGE / BBB
-salivation , lacrimation ( uncontrollable flow of tears ) , urination , defaecation , gastric emesis
- bronchospasm ( abnormal contraction of bronchi smooth muscle )
- bronchoconstriction
- bronchorrea ( overproduction of sputum )
Nicotinic effects
1 ANS - ( sympathetic) : bronchodilaton , tachycardia , pallor , hypertension
2 somatic : fasculations , fatigue , cramps
Acute and chronic effects of organophosphates
1 all nicotinic and muscarinic effects
2 polyneuropathy with flaccid weakness of lower limbs and sensory disturbances
Differential diagnosis of organophosphates poisoning
1 viral gastroenteritis 2 botulism 3 mushroom toxicity 4 Eaton-lambert syndrome 5 myasthenia gravis
Investigations of organophosphates poisoning
1 RBC cholinesterase : reduced levels show inhibition
2 ECG - inverted T Waves
- elevated ST segments
- prolonged QT interval
- sinus bradycardia with PR prolonged
Describe the 1s 3 steps of organophosphate management
1 skin decontamination- remove clothes, removal from site of exposure , wear PPE , wash with soap and water
2 airway and breathing - secure with adequate O2
3 cardiac monitoring - ECG monitoring
List the types of Doses ( medicines ) used to treat organophosphates
1 atropine 2 pralidoxime 3 glycopyrolate 4 oximes 5 bezodiazepine 6 suxamethoneium
Describe atropine function , dose , signs that it’s working and when is it started
- started after airway secured
- competes with Ach at muscarinic receptors preventing cholinergic stimulation
- start of with 2mg IV bolus
- 2-5 mg every 5-15 mins
If working
1 decreased sputum formation
2 increased heart rate
3 reduced bowel sounds
Describe glycopyrolate
Describe oximes
- doesn’t cross BB Barrier
- controls CNS cholinergic toxicity
- reduces salivary , tracheobronchial and pharyngeal secretions
-nucleophilic Agents that reactivate phosphorylated AcHE by binding to organophosphates
