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Toxicology: (General Approach (INVESTIGATIONS (Other Investigations
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Toxicology:
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Bite/Stings
Snake
- Common Presentation to Australian ED's
- Envenoming is rare,but lethal
- Even if no bite mark or symptoms may still be envenomed.
- Time- Critical emergency
- Medically NB snakes:
- Brown, Tiger, Death Adders, Black, Tiapan, Sea Snakes
- Most NB Clinical effects of envenoming: Consumptive Coagulopathy (VICC), Neurotoxicity, Rhabdomyolysis, Renal Failure
(Pg 37 + 38 in Toxicology Handbook)
FIRST AID:
- Delay lymphatic spread and systemic effects
- Pressure-Immobilisation bandaging
- Pressure bandage entire limb
- Immobilisation of limb
- Immobilisation of patient
- do not removed until medical assessment
HOSPITAL MX
- Resusitation ABCDE,
- Determine of envenomed
- Life threatening Features
- Hypotension (brown, Tiger, Taipan)
- Resp Failure secondary to paralysis ( Death adders, taipan, tiger)
- Seizures (taipan)
- VICC with uncontrolled haemorrhage
- Serial Examination and investigations when PIB removed @ 1, 6, 12hrs.
- Determine if monovalent/polyvalent antivenom and doses required
- Clinical Presentation
- Knowledge of snakes in the area
- Lab abnormalities
- Commonwealth Serum Laboratories Snake Venom Detection Kit
- Adjuvant therapy
- Risk of serum sickness (4-21 days) post antivemom. Treat with Prednisolone for 5 days.
- ? fresh frozen plasma or cryoprecipitate in VICC
- Update tetanus
Spider
REDBACK
- Most Common, not life-threatening
- Ubiquitous
- Toxin: Alpha-Latrotoxin - Open presynaptic cation channels → Release multiple motor endplate NT's
- Clinical Presentation lactrodectism
- Local pain 5-10min after bite
- Piloerection
- Generalised or regional sweating
- Mild Hypertension
- Tachycardia
- Ascending pain
- N/V, headache, dysphoria
- if no treatment: 1-4 days fluctuating course
- Management
- Pre-hospital: Ice pack, analgesia, NOT PIB
- Hospital: CSL Redback Spider Antivenom. Patients without features of systemic envenoming → D/C
WHITETAIL
- Ubiquitous
- Toxin: no cytoxic effects
- Clinical Features
- Painful bite
- severe local (<2hrs), Local pain + red mark ( <24hrs)
- Persistent and painful red lesion (5-12 days)
- No ulceration or necrosis occurs
- N/V, Headache
- Managment
- Ice, Analgesia, NO PIB
- Hospital care not indicated
FUNNEL-WEB
- East Coast AU
- Lethal
- Neurotoxin: Inactivate Na channels → ↑ ANS and Neuro- muscular activity
- Clinical Features
- Local pain, famg marks
- Systemic signs within 30minutes
- Hypertension, tachucardia, pulmonary oedema, fasciculations etc.
- Management
- PIB
- Resus
- Antivenom
- Disposition and F/U
- No systemic features @ 4hrs → D/C
Irukandji ( Jelly Fish)
- Hypotension/Hypertension
- Severe Pain
- Feeling of Impending Doom
- Catecholamine Excess
- Toxin induced Cardiomyopathy
- Die from Cardiac Shock
Box Jelly Fish
- Not usually fatal
- Bit can die from Sudden cardiac Arrest
-
String Ray
- Tx: Hot emmersion and regional anasthesia
- Avoid Local Anaesthetic and Adrenaline
Paracetamol
- Dose: >200mg/kg or >10g in 24hrs ( Massive ingestion >500mg - Modified NAC Dose)
- Main Complication: Hepatic Injury, risk predicted with Nomogram and time of ingestion to commencement of NAC
- Toxic Mechanism: In overdose hepatic metabolism is overwhelmed and Glutathione stores are exhausted ↑ NAPQI ( Centrilobular Necrosis of the liver)
- Toxicokinetics: SI absoprtion, Peak levels in 1-2hrs, VoD: 0.9L/kg
- Clinical Features: Described as phases
- As managment we give NAC which acts as a glutathione donor and prevents NAPQI Accumulation
APPROACH
- Resuscitation: ABCDE
- Risk Assessment: Agent, Dose, time of ingestion, clinical symptoms, patient factors
- Supportive Care: General supportive care, monitoring (BSL, signs of encephalopathy)
- Investigations : Paracetamol levels (4 and 8 hours) + nomogram, LFTs (ALT/AST (peaks 72 hours post ingestion)), INR, UEC.
- Decontamination: Activated charcoal if presentation <2 hours (50g)
- Enhanced elimination: Not clinically useful
- Antidotes IV NAC –2 stage infusion of total 300 mg/kg over 20 hours.*
- 200ml/kg over 4 hours
- 100mg/kg over 16 hours
- Beware anaphylactoid response - stop the infusion, give an antihistamine and recommence once symptoms settle then recommence tx.
- OTHER CONSIDERATIONS within 24hrs and sym, Start NAC; > 24hrs no sym, check levels before treating; >24hrs, sym, NAC
STOP NAC: ALT Down trending
- Disposition: If NAC given <8hours after ingestion usually able to d/c after 20 hour infusion, for other cases general rule is continue NAC and monitor for downward trend in ALT/AST, asymptomatic and serum paracetamol<10g, will require psych assessment if intentional overdose
Patient taken MASSIVE dose and has Physical features (Low GCS): Intubate, Activated charcoal via NG, , Paracetomol level and LFT's, Start NAC at higher the usual dose (possibly double)
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TCA's
- Amitriptyline, Clomipramine, Dothiepin, Doxepin, Imipramine, Nortriptyline, Trimipramine
- Main complication:Rapid Onset CNS and Cardiovascular Toxicity
- Dose:>10mg/kg life threatening
- Mech: NA and 5 HT reuptake inhibitors, GABAa Blockers
- Mycocardial toxicity and Myocardial Depression → Na and K channel blockade
- Blocks: M1, H1, A1
- Toxicokinetics Rapidly absorbed, peaks 2hrs, Large VoD, Plasma and protein bound, Hepatic metabolism
CLINICAL FEATURES
- SEVERE TOXICITY: Rapid deterioration in 1-2 hrs of ingestion
- Coma, seizures, hypotension, cardiac arrhythmias
- Sinus Tachy and ↑BP, Hypotension, Broad-complex Tachy and Broad-complex brady pre-arrest NA CHANNEL BLOCKADE
- Anti-cholinergic effects
- Agittions, restlessness, Delirium
- Mydriasis
- Dry, Warm, Flushed skin
- Tachy, Unrinary retention, ileus
- Myoclonic jerks
APPROACH
- Resuscitation: ABCDE
- Risk Assessment
- Supportive Care:
- Intubation and hyperventilation @ GCS <12. Maintain pH: 7.50-7.55.
- Arrhythmias: Sodium bicarbonate 100mmol IV, every 1-2 minutes until restoration of perfusing rhythm ; Lignocaine 1.5mg/kg when pH >7.5.
- Hypotension: Crystaloids, Sodium Bicarb, Adrenaline/NA infusion
- Seizures: Benzo's
- Catheter adn bladder care
- PRessure Ulcers - Turning the patient
- VTE Prophylaxis
- Decontamination: Activated Charcoal (only after airway secured - Seen done via NG Tube)
- Investigations:
- Screening Test: - Serial ECG, BSL, Paracetomol
- Serial ECG
- PR and QRS prolongation
- QT prolongation
- Specific tests Timed drugs levels
- Antidotes: Sodiume Bicarbonate as above
- Disposition: Based on @ 6 hrs: ECG, Mental Status, BP, seizures. If required intubation and ventilation → ICU
Benzodiazepines
CLINICAL FEATURES
- within 1-2 hours
- Ataxia, lethargy, slurred speech, drowsiness, decreased level of responsiveness
- Large ingestions: hypothermia, bradycardia, hypo tension
- Resolved with 12hrs
APPROACH
- Resuscitation: ABCDE
- Risk Assessment: Mild sedation in isolated overdose; co-ingestion increased complications, length of stay and risk of death
- Supportive Care:
- Investigations
- Antidote: Flumazenil in special cases
- Decontamination: Not indicated
- Disposition:
- Mild sedation - managed supportive management on wards. D/C when clinically well
- Significant CNS Depression: ICU
Midazolam, Clonazepam, Temazepam
- 1/3 Deliberate Self Poisenings
- Main Effect: CNS Depression
- Toxic mech: GABAa Agonists → ↑Cl channel opening → Inhibition and depression
- Toxicokinetics:
- Rapidly Absorbed Orally
- Protein bound
- Hepatic Metabolism, with active metabolites
- Duration of overdose depends on CNS Tolerance and redistribution, rather than rate of elimination
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Serotonin Syndrome
- Excess accumulation of 5-HT in CNS
- Mechanisms:
- Excess Release
- Inhibited Reuptake
- Inhibited Metabolism
- Increase Pre-cursor - tryptophan
- Clinical Features:
RISK OF: RHABDOMYOLYSIS
- Diagnosis: CLINICAL
- Hx of ingestion
- characteristic features
- high index of suspicion
- Clincal Setting with Increased risk :
- Intro or increased Dose of serotonergic drug
- No adequate "Washout" period
- Interaction between 2 serotonegic agents
- Interaction between serotenerg drug and Illicit drug
- Self-Poisoning
-
Approach
- Resuscitation: ABCDE
- Risk Assessment:
- Supportive Care: Cease agent, Reassure, IV Fluids and Fluid Balance Chart
- Observe: Temp, Mental Status, Muscle tone
- Benzo's: Diazapam 5-10mg
- Investigations: BSL, ECG, Paracetamol, UEC's, Creatinine *
- Decontamination: Not indicated
- Antidote: Not enough evidence
- Disposition: Self-Poisoning - observe for 8hours, then anywhere up to 24-48hrs depending on the scenario.
Alcohol
- CNS Depression
- Consider: Intoxication and Withdrawal
- Toxic Mechanism: Mainly GABAa agonist
- Toxicokinetics:
- Clinical Features: Progressive with increasing degrees of intoxication, disinhibition, Euphoria, Nystagmus, Ataxia, Slurred Speech, Agitation, disorientation, N/V, Tachycardia, Hypotension, Coma, Resp depression
Approach
- Resuscitation: ABCDE
- Risk Assessment: Risk Assessment:* Agent, Dose, time of ingestion, clinical symptoms, patient factors
- Standard Drinks with 10g ETOH ( 375mL Beer, 100mL wine; 30mL spirits)
- Supportive Care: Thiamine 100mg PO or IV, Close monitoring, Montior for Urinary retention +/- Catheter
- Investigations: BSL, ECG, Paracetamol levels, Blood ETOH level
- Decontamination: Not indicated
- Enhanced Elimination: Haemodialysis if indictaed
- Antedotes; None Available
General Information
- Common ED presentation
- Context:
- Deliberate Self-Poisoning
- Recreational Drug use Complication
- Unintentional paediatric exposure
- Presentation with poisoning is a medical exacerbation of a chronic psychological disorder
- Need Psycho-social assessment and F/U
- Acute Mortality → Cardiovascular, Respiratory, neurological Complications
One Pill can kill → Kids
- Syph- ureas
- Cardiac Drugs
- Ca Channel Blockers
- B blockers
- Lithium