Clinical Toxicology 1 Flashcards
what are the most common cases of poisoning caused by ?
involving drug misuse
sometimes due to self inflicted either to cause suicide or as a case of parasuicide
accidental poisoning is very uncommon
What is clinical toxicology also referred to as?
diagnosis of poisoning and its treatment
in the UK in 2005 what were the statistics of poisoning ?
1783 deaths due to poisoning by drugs, medicants and biological substances
910 deaths due to accidental poisoning and noxious substances
761 deaths due to intentional self poisoning
65 deaths were caused by criminal poisoning
how many patients per year in the UK are admitted to hospital for treatment of poisoning ?
as many as 170000
how is the poisoning of a patients evaluated ?
using ABCDE approach airway breathing circulation disability exposure
what are the affects on the airways and breathing generally caused by poisoning ?
shallow and irregular breathing
low partial pressure of oxygen
build up of carbon dioxide
what is usually the first priority when a patients has been poisoned ?
to maintain a clear airway and support their breathing if its needed
how do you ensure the airways are clear?
conscious patients- positioning patient on side to prevent them chocking on vomit
unconscious patient- prevent tongue falling back and obstructing pharynx
what may be necessary in unconscious patients to maintain clear airways ?
insertion of an endotracheal tube to maintain artifical breathing and deliver oxygen to maintain pressure in blood
what drugs if overdosed on can cause respiratory depression?
ethanol
opiates
antidepressants
what effects does poisoning often have on circulation ?
cause cardiac dysrhythmias and shock
what are the priorities of circulation that have to be checked?
vascular assess- to get blood samples and to correct any abnormal chemistry of the blood
check heart rhythm
check blood pressure
what often happens in a TCA overdose ?
block the fast sodium channels in the heart causing reduced contractility and dysrhythmias
can cause hypotension
how can an overdose on TCAs be reversed ?
infusion of sodium bicarbonate can reverse blockade of sodium channels
hypotension can be corrected by a vasopressor such as noradrenaline or phenylephrine
what can an overdose with MAOIs cause and how is it treated?
cause severe hypertension
treated with a short acting vasodilator such as nitroprusside
what is shock and why is it dangerous?
dangerous because it can cause cardiovasular collapse
causes low systolic BP, tachycardia, cold pale skin, acidosis and low oxygen tension in arterial blood
main feature is dilation of venous bed causing poor venous return and decrease in CO
how is shock managed ?
expansion of circulation volume by infusion of high molecular weight impermeant substance such as dextran
admin of drugs to increase CO- dopamine, dobutamine
correction of acidosis with infusion of sodium bicaronate - important because it can depress myocardial contractility
what is classed as disability by poisoning ?
seizures agitation delirium coma hyper or hypothermia
what is a common cause of delirium and coma ?
hypoglycaemia
easy to detect levels by blood sample and corrected by dextrose
why are seizures dangerous ?
they can impair cardio-respiratory function
what class of drug can often induce seizures and how is it treated ?
TCAs
controlled by benzodiazepines with anticonvulsant activity- diazepam
what drug if overdosed can cause hyperthermia/hypothermia?
hyperthermia- caused by amphetamines
hypothermia- caused by opiates
what is associated with hyperthermia and how is it treated ?
> 40 degrees temp
loss of blood caused by prolonged sweating
restored by fluid replacement
in severe cases ice baths are required
also decreases the need for calcium in excitation contraction coupling so muscles contract without exertion generating heat - treated with dantrolene
why does hypothermia normally occur ?
due to coma
<35 degrees
what are the 4 ways to minimise or prevent entry of an oral toxicant to reduce or prevent exposure?
gastric lavage= stomach is washed 3-4 times to remove contents
emesis= admin of ipecacuanha syrup containing many alkaloids that irritate the stomach and stimulate chemo trigger zone in medulla
adsorption = many organic toxicant bind to activate charcoal so this is best at removing drugs in the gut - given orally at 10x estimated weight of toxicant
bowel irrigation with polyethylene glycol= given a solution at about 2L/hr - good if substance does bind to charcoal well and removing packages of illicit drugs
how can you speed up removal of the toxicant from the body to reduce exposure ?
forced diuresis for weakly acidic/basic compounds
dialysis for removal of small molecular weight solutes in body fluids
explain forced diuresis
urine made alkaline -pH7-8 by infusion of large volume of sodium hydrogen carbonate - used for barbiturate or salicylate poisoning
acid urine produced by infusion of NH4Cl helps excretioin of weak bases such as amphetamine
explain haemodialysis
relies on diffusion of solutes across a semi-permeable membrane
blood is dialysed against continuous stream of toxicant free fluid
this is only useful if toxicant has a small volume of distribution
haemofiltration and haemoperfusion to remove toxic substances from blood
what are toxidromes?
they are a group of symptoms which can be useful at diagnosing the type of poisoning
what causes cholinergic toxidrome?
caused by organophosphate nerve agents - cause gross activation of the parasympathetic nervous system
what are the symptoms of cholinergic toxidrome ?
DUMBBELS - diarrhoea - urination - miosis= excessive constriction of pupil - bronchorrhoea= accumulation of fluid in the bronchioles and lungs - can drown from this - bronchospasm= difficulty breathing - emesis - lacrimination - salivation also seizures
what can cause anticholinergic toxidrome?
arises by atropine and hyoseine administration = plant toxins
-atropine is from deadly night shade and some fungi
what are the symptoms of anticholinergic toxidrome ?
dry mouth
dilated pupils
blurred near vision - accommodation becomes paralysed
warm, dry and red skin - particularly in the face
urinary retention and constipation
tachycardia
confusion - delirium
what can be used as an antidote for cholinergic toxidrome ?
atropine
what can you use to treat anticholinergic toxidrome ?
acetylcholinesterase
what are the symptoms of sympathetic toxidrome ?
dilated pupils excessive sweating agitation hyperthermia tachycardia hypertension dysrhythmias
why are toxidromes useful ?
useful in clinical situations to determine the type pf poisoning to help guide an appropriate treatment
