Toxiciology Flashcards
What are the features of salicylate poisoning? (6)
- Increased RR
- Tinnitus
- Deafness
- Sweating
- Vasodilation
- Acid base disturbance
What metabolic disturbance do adults presenting with salicylate poisoning predominates?
Reps alkalosis > metabolic acidoses
What metabolic disturbance do children presenting with salicylate poisoning predominates?
Metabolic acidosis > resp alkalosis
What is mild salicylate poisoning and how should it be managed?
- < 300mg/L
- Asymp and normal VBG then home at 6 hours
What is moderate salicylate poisoning and how should it be managed?
- 300-700mg/L
- Urinary alkalization - PH 7.5-8.5 using sodium bicarbonate
What is severe salicylate poisoning?
1, CNS features, acidosis or > 700mg/L
2. Consider HD and I+V
What is the pathophysiology of paracetamol poisoning?
Metabolite of paracetamol (NAPQI) binds glutathione in the liver and causes hepatic necrosis when glutathione stores are depleted.
What are the features of TCA OD in conscious patients? (7)
Anti-cholinergic toxidrome
- Tachycardia
- Dry skin
- Dry mouth
- Dilated pupils
- Urinary retention
- Ataxia
- Jerky limb movements
What signs do unconscious patients developed following TCA OD? (7)
- Divergent squint
- Hypertonia
- Hyper-reflexia
- Myoclonus
- Upgoing plantars
If comatose - areflexia and muscle facciditiy
What ECG changes will be seen in TCA OD and which is the most sensitive?
- Increased QRS (most sensitive)
- Increased PR
- Tachy
- P waves can be lost in T - looks like VT
What is the tx for TCA overdose? (5)
- If under 1 hour activated charcoal
- 50-100ml 8.4% bicarbonate
- Aim PH 7.5-7.55 (excessive is fatal) and normal QRS
- Avoid routine use anti-arrhythmics
- Severe consider glucagon or intralipid
What is the antidote to benzo OD?
Flumazenil
How long does flumezanil last?
1 hour
What are the risks of using flumazenil and when is it particularly high risk?
Can lead to convulsions and arrhythmias
With concurrent TCA OD - can lead to arrest
What signs/symptoms feature in haloperidol + chlorpromazine (and related drugs)?
Oculogyric crisis
Muscle spasms - torticollis/opisthonus
What ECG changes will you see in haloeridol/chlorpromazine/similar drugs in OD? (2)
- Increased QRS
- Arrhythmias
What is the treatment for haloperiol/chlorpromazine OD? (3)
- Proycylidine
- Diazepam
- Bicarbonate if QRS >120ms
What are the features of lithium toxicity? (6)
- n/v
- diarrhoea
- ataxia
- confusion
- increased tone
- clonus
What is the treatment for lithium toxicity?
Supportive
Dialysis
What are the effects of sulfanylurea overdose?
- Low glucose
- Low potassium
What is the treatment for sulfanylurea overdose?
Octreotide
What are the features of unique to propanolol OD? (2)
- Bronchospasm in asthmatics
- Hypoglycaemia in children
What does sotalol OD cause in particular?
Torsades des pointes
What are the treatments of beta blocker OD without severe hypotension?
- Consider activated charcoal
- Atropine may work (pacing probably not)
- Glucagon 5-10mg IV (anticipate vomiting)
In severe beta-blocker OD with low BP what are 3 treatment options?
- High dose Insulin Euglycaemic Therapy (HIET)
- Intralipid
- Ionotropes/vasopressors
What are the features of CCB OD? (6)
- Bradycardia
- AV block
- Profound vasolidation
- Metabolic acidosis
- Hyperkalaemia
- Hyperglycaemia
What is the treatment for CCB OD? (3)
- Consider activated charcoal
- Atropine +/- pacing
- Calcium chloride 10% over 10 mins and consider repeating up to x 4
What are the treatment options for severe CCB OD? (4)
- Glucagon
- Intralipid
- HIET
- Vasopressors/ionotropes
What are the features of digoxin toxicity? (4)
- Xanthopisa- yellow flashes/discolouration
- Hyperkalaemia
- Brady, increased PR/QRS
- Arrhythmias
What is the treatment for digoxin toxicity? (3)
- Digiblind/Digifab
- Insulin/dex for increased K+ (rapid decrease with Digibind)
- Atropine/pacing
What are the biochemical changes in acute methanol poisoning? (3)
- Acidosis
- Hypergylcaemia
- Raised amylase
What are survivors of methanol poisoning at risk of? (2)
- Blindness
- Parkinsonian features
What is the treatment for methanol poisoning? (4)
Ethanol
Fomepizole
Folinic acid
Bicarbonate if acidotic
What are the early (<12 hours) features of ethylene glycol poisoning?
Appear drunk, no smell alcohol
What are the late features of ethylene glycol poisoning? (6)
- CCF
- Acidosis
- Tachy/arrhythmias
- Hypocalcaemia (can be profound)
- Acute tubular necrosis
- CN palsies`
What are the treatment options for ethylene glycol poisoning? (5)
- Fomepizole
- Ethanol
- Sodium bicarbonate for acidosis
- Calcium chloride only if seizures or QTc >500 as can lead to calcium oxolate stones
- HD + I+V
What can occur in petrol ingestion?
Can be fine but aspiration lead to severe pneumonitis requiring steroids + resp support
What is the pathophysiology of organophosphate poisoning?
Inhibit cholinesterases which leads to build up of acetylcholine at nerve endings (cholinergic affect)
What are the features of organophosphate poisoning (cholinergic toxidrome)? (8)
S- alivation
L - acrimation
U - rination
D - efecation
G - I upset
E - mesis
M - iosis
M - muscle twitching
Bradycardia, paralysis and resp failure
What is the treatment for organophosphate poisoning and what is its mechanism
Atropine - blocks affect of acetylcholine at muscarinic receptors
Eases smooth muscle constriction and dries up secretions
What is the atropine dose in organophosphate poisoning?
2mg IV adult
0.02mg/kg children
Every 5 mins double dose until atropinisation
What is the mechanism of pralidoxime?
Reactivate acetylcholinesterase inhibited by organophosphates allowing metabolisation of acetylcholine.
What can lead to cyanide poisoning? (3)
- Polyurethane burning
- Fruit kernels
- Finger polish remover
What are the features of cyanide poisoning? (4)
- Metabolic acidosis
- Seizures
- Pulmonary oedema
- Arrhythmias
What is the initial management of cyanide poisoning? (2)
- Remove clothes
- Wash exposed skinW
What is the antidote for severe cyanide poisoning and what is the risk of giving it?
- Dicobalt edetate - Kelocyanor
- If no cyanide can be fatal
What are the treatments for mild cyanide poisoning? (2)
- Sodium thiosulphate
- Sodium nitrate
What is the best treatment for inhaled cyanide poisoning?
5g hyroxycobalamin IV (Cyanokit)
What is the max dose of lidocaine?
3mg/kg
max 200mg
What is the maximum dose of lidocaine with adrenaline?
7mg/kg
max 500mg
What is the maximum dose of bupivicaine?
2mg/kg
150mg
What is the management of LA toxicity including dose?
Intralipid
1.1.5mg/kg bolus and 15mg/kg/hr infusion
5 mins no response:
2. 2nd bolus and increase infusion to 30mg/kg/hr
3.Continue to 3rd and 4th bolus which is maximum
In arrest may need 1 hour for intralipid to take effect
How are hydrofluric burns managed? (4)
- Irrigate normal saline ++
- Calcium gluconate gel
- Tx low Ca2+
- In arrest - 60ml x 10% calcium chloride
What drugs can cause methaemoglobinaemia?(7)
benzene derivatives
chloroquine
dapsone
prilocaine
metoclopramide
nitrites (nitroglycerin, NO, sodium nitroprusside)
sulphonamides
What are the features of methaemoglobinaemia?
1.cyanosis
2. symptoms and signs of decreased oxygen delivery e.g. chest pain, dyspnea, altered metal state, end organ damage
3. SpO2 reading 85-90%
4. blood samples typically have a chocolate brown hue
5. Normal PaO2
What is the treatment for methaemoglobinaemia?
Methylene blue
What is the triad of symptoms in serotonin syndrome?
- Change in mental staus
- Autonomic hyperactivity
- Neuromuscular manifestations
What are the 3 major and 5 minor symptoms suggestive of neuroleptic malignant syndrome?
Major
1. Fever
2. Rigidity
3. Elevated CK
Minor
1. Tachycardia
2. Abnormal arterial pressure
3. Altered consciousness
4. Diaphoresis
5. Leucocytosis
Describe an anticholinergic toxidrome (8)
- Altered mental status, confusion, restlessness, seizures, coma
Symptoms resulting from peripheral muscarinic receptor blockade:
2. Impaired sweat gland function
3. Dry mouth
4. Dry axillae
5. Mydriasis
6. Tachycardia
7. Flushing
8. Urinary retention
In cases of serotonin syndrome where other management options have failed, what is the treatment?
Cryoheptadine
What are the tx options for NMS? (2)
- Bromocriptine (first line)
- Dantrolene
What are the commonly used drugs in ED that might cause methaemaglobinaemia? (4)
- Metoclopramide
- Nitrites (including ‘poppers’ and GTN)
- Local anaesthetics
- Abx including dapsone
What level of methaemagobinaemia should be treated? (2)
- > 30% methaemaglobin
- Any evidence of tissue hypoxia
If initial management of beta blocker OD with low BP doesn’t success (i.e. glucagon) what does toxbase suggest as second line?
HIET
How is the toxicity of something calculated?
From the Lethal Dose 50 (LD50) = concentration required to kill 50% of exposed individuals
How do cholinergic drugs act?
Class of medication that increase/mimic activity of acetylcholine and lead to parasympathetic activity increase
Name anticholingergic medication? (7)
- Tricyclic antidepressants (amitryptyline)
- oxybutynin
- olanzepine
- quetiapine
- clozapine
- chlorpromazine
- prochlorperazine
What type of toxidrome does Sarin gas cause?
Cholinergic
Over what level does acute radiation syndrome?
> 0.5 Sv (Sievert)
What are the paeds ‘one pill killers?’ (8)
- Beta blockers
- Calcium channel blockers
- Opiates
- Amphetamines
- Theophylline
- Sulfonyureas
- TCAs
- Chloroquines
When should we not offer PEP to a patient who has unprotected sex with a patient who is HIV positive?
If partner has been on ART > 6 months and has had an undetectable viral load in last 6 months
When should PEP be offered routinely (4)
If unknown or detectable vial load and:
1. Receptive anal sex
2. Receptive vaginal sex
3. Occupational exposure
4. Needle sharing
When should PEP be considered? (2)
Unknown or detectable viral and:
1. Insertive vaginal sex
2. Insertive anal sex
When is PEP not recommended? (2)
- Sex/splash/injection in high risk group but not known HIV
- Human bite in HIV positive
What PEP should be offered?
Tenovir + emtricitabne (Truvada) combination and raltegravir OD for 28 days
When should PEP be started?
ASAP (ideally <24hours)
After what period is PEP not effective?
> 72 hours
What is a tetanus prone wound? (5)
- Puncture wounds occurring in contaminated enviroment
- Wounds with foreign body
- Compound #s
- Wounds/burns with sepsis
- Certain animal bites
What are high risk tetanus prone wounds? (3)
- Heavy contamination with soil containing spores
- Wounds/burns with significant devitalised tissues
- Wounds/burns requiring surgery that are delayed over 6 hours
What is full tetanus immunisation? (3)
- > 11 year priming course and last dose < 10 years ago
- 5-11 years and priming course pre-school booster
- < 5 years and priming course
What is partial tetanus immunisation? (2)
- Over 11 years, priming course but last dose >10 years
- 5-11 years with priming course but no pre-school booster
If fully immunised against tetanus what do you require following a:
1. clean wound
2. tetanus prone wound
3. high risk tetanus prone wound
Nothing
If partially immune against tetanus what do you require following a:
1. clean wound
2. tetanus prone wound
3. high risk tetanus prone wound
1.Nil
2. Vaccine dose
3. Vaccine and TIG
If no immunisation against tetanus what do you require following a:
1. clean wound
2. tetanus prone wound
3. high risk tetanus prone wound
- Vaccine
- Vaccine and TIG
- Vaccine and TIG
What dose of TIG should be given in tetanus? (4)
- 250 IU IM
- 500 IU IM if :
- heavy contamination
- burns
- > 24 hours
NB do not given vaccine and TIG at same site
What is a clean wound re: tetanus risk?
< 6 hours
non-penetrating
What level of TCA overdose is considered life threatening?
> 10mg/kg
What causes the ECG changes associated with TCA overdose?
Sodium channel blockade
What ECG change in TCA OD is predictive of:
1. seizures
2. arrhythmia
- QRS > 100ms
- QRS >160ms
What should be used to target sodium bicarbonate treatment for TCA OD? (2)
- Narrow QRS
- PH 7.5-7.55
What is the mechanism behind malignant hyperpyrexia?
- genetic abnormality of the ryanodine receptor and excitation-contraction coupling in the skeletal muscle when exposed to certain triggers
What does malignancy hyperpyrexia lead to?
- continuous release of calcium into muscle cell
- leads to a huge increase in metabolic demand, hypercalcaemia, continuous muscle contraction and rigidity
- increaesed metabolic demand leads to consistent increase ETC02, tachycardia and pyrexia.
- ultimately leads to MOF/DIC
How should malignant hyperpyrexia be treated? (4)
- Stop/remove trigger
- Dantrolene (ryanodine receptor antagonist) 2.5mg/kg and repeated at 1mg/kg until ETC02 <6KPa and temp <38.5
- Active cooling to <38.5 degrees C
- Acidosis- hyperventilate to normal pC02 and add sodium bicarbonate if PH remains < 7.2
What is the toxic dose of paracetamol?
10g or >200mg/kg
What dose of paracetamol is considered safe?
75mg/kg (therapeutic excess)
What is the maximum weight to be used when calculating NAC dose?
110kg
How common are anaphylactoid reactions with NAC tx?
10-50%
What is intralipid made up of? (4)
- Soya oil
- Egg
- Phospholipids
- Glycerol
What can be used as an adjunct to managing digoxin toxicity?
Magnesium sulphate
How is arsenic poisoning managed?
Chelation with succimer or dimercaprol
How should life threatening acute hypercalcaemia be managed?
IV pamidronate
What is the mechanism of action of Paraquat poisoning?
Generates reactive oxygen species (ROS) and induces oxidative stress, leading to cell damage and death.
This mechanism primarily targets the alveolar cells in the lungs, which can result in severe pulmonary injury.
How is Paraquat poisoning managed?
- Mild hypoxia tolerated >88%
- Anti-oxidants e.g NAC
- Supportive care
What is the mechanism of action of cocaine?
Sodium channel blocker and inhibits noradrenaline and serotonin reuptake
What are the sympathominetic effects from the sodium channel blockade of cocaine?
- Hypethermia
- Hypertension
- Cardiac conduction abnormalities
- Vasconstriction - IHD/SAH
What are the 4 families of viruses that cause VHF?
- Arenavirus
- Filovirus
- Bunyavirus
- Flavivirus
How are VHF transmitted?
Percutaneous/mucosal contact with bodily fluids
What is the incubation of VHF?
21 days
What are some of the more common notifiable diseases?
- Meningitis/encephalitis
- Botulism
- Cholera
- Covid
- Invasive group A step
- MMR
- Rabies
- SARS
- VHF
How does cement cause injury?
Caustic injury and liquefactive necrosis
When it reacts with water cement powder produces highly alkali calcium hydroxide (PH >12)
What does dry cement cause in terms of injury? (2)
- If powder reacts with sweat/resp secretions causs topical burns
- Can cause silicosis
Describe the local and systemic mechanism for hydrofluoric burns?
Local:
- H+ and F- ions cause direct local tissue damage
- F- ions highly lipophilic and absorbed into the deep layers of the dermis and cause liquefactive necrosis. This causes a release of intracellular myoglobin, urate and K+
Systemic:
- F- also absorbed systemically resulting in systemic fluorosis (main mechanism of toxicity)
- F- chelate calcium and magnesium leading to profound hypocalcaemia/magnesia.
- Hypocalcaemia leads to Na+/K+ ATPase inhibition, negative ionotropy and QTc prolongation and increased permeability to K+ leading to hyperkalaemia
- Hypomagnesia can lead to polymorphic VT and seizures
What are the dermal signs of HF burns?
Grey and sloughy
Patients can report deep pain but not have any dermal evidence
What can ingested HF lead to?
Cardiac arrest within 30 mins to 6 hours
Describe how phosphorous causes:
1. Local burns
2. Respiratory issues
3. Systemic toxicity
- Lipophilic and causes deep subcutaneous burns like HF acid
- Burning white phosphorous leads to phosphorous pentoxide smoke that is a respiratory irritant
- Presents in 3 phases:
- non specific abdo pain and diarrhoea
- then asymp
- haemolysis, hypocalcaemia and MOF
What is the treatment for phosphorous toxicity?
Supportive
What do phosphorous burns appear like?
Yellow appearance and smell of garlic
What is unique about the smell of hydrogen sulphide?
- Smells rotten eggs
- Proportion of population can’t smell it
- Smell diminishes at high concentrations.
What is the priority when managing hydrogen sulphide poisoning? (2)
- Remove from source
- High flow 02
What are the effects of hydrogen sulphide poisoning at 1.low and 2. high concentrations?
1.Bronchospasm, Methaemoglobinaemia, respiratory paralysis, cyanosis, convulsions, coma, cardiac arrhythmias, and death within minutes.
- irritate the eyes and respiratory tract, resulting in sore throat, cough, and dyspnoea.
What is the appearance and odour of chlorine gas?
Green/yellow appearance
Bleach like odour
Where will chlorine gas accumulate when mixed with air?
Low areas as it is heavier than air
What are the local and systemic affects of chlorine?
- Local = irritant and corrosive. Causes sloughing of the pulmonary mucosa 3-5 days after inhalation causing metabolic alkalosis and respiratory acidosis
- None (according to book, not sure this is the case)
What concentrations of chlorine are needed to cause:
1. acute symptoms
2. fatality
- > 15 parts per million (ppm)
- 430ppm for 30 mins
How do button batteries cause damage to patients?
- Saliva and oesophageal tissue allow current to flow between the positive and negative poles of the battery in an electrolytic reaction.
- Sodium hydroxide that forms at the negative pole is a strong alkali and causes chemical burns
What chemical causes burns in button batteries?
Sodium hydroxide (Strong alkali)
What time frame can button batteries cause symptoms?
From 2 hours after ingestion up to 28 days (Even after removed)
What are the risk factors for injury with regards to button batteries? (5)
- Oesophageal location (and above
- size (lower risk if <12mm, higher if >20mm),
- prolonged mucosal contact
- younger age (<6 years)
- coingestion with magnets
What is the initial investigation of choice for button battery ingestion
AP + lateral neck/chest/abdo XR
Whilst waiting for surgical removal of battery what other intervention can be attempted if:
1. > 1year
2. Any age
If ingestion occurred LESS than 12 hours ago;
- > 1 year give 10 mls honey every 10 mins (max 6 doses)
OR
- Any age give 1 gram sucralfate oral suspension every 10 mins
(max 3 doses)
What is the management for button batteries:
1. above clavicle
2. below diapragm
- Time critical surgical emergency
- D/w surgical team - likely follow up xr 24-48 hours
