Organophosphate Poisoning Flashcards
(18 cards)
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
Describe benzodiazepines and suxamethoneium
- treated seizures by increasing GABA activity
- competitive agonist for AcH
Initial resuscitation based on toxicity
/moderate to severe - O2 and intubation
/mild - monitoring
What does pralidoxime do , dose and used with what and why
- actives AcHE in nicotinic nervous system
- used with atropine to prevent worsening of condition due to oxime induced
- 30mg / kg for 30 mins
- infusion 8mg / kg per hour
