This section will give a brief overview to the toxicology patient covering initial approach, risk assessment, examination, investigations, and treatments.

Links are provided to more in depth discussion of some topics particularly treatment modalities.

Some knowledge of the epidemiology of poisoning (toxicoepidemiology), preferably from your area, is useful as an aid to diagnosis when the history of ingestion is unclear. Common poisonings occur commonly. The poisons ingested vary substantially between countries and between urban and rural areas (where pesticides and herbicides are more common). They are also different for adults, adolescents, and children.

Medications ingested to some extent reflect what is prescribed in the community, with patients being far more likely to ingest some types of drugs per prescription than others.

A combination of knowledge of the possible toxic effects of drugs, the frequency with which these effects occur and the frequency with which these drugs are taken in overdose is a sensible approach to diagnosis.

Daly et al. (2006) ^[1] provide a summary of factors that need to be considered when assessing and managing the toxicology patient. Their described approach forms the common mnemonic 'R RSI DEAD', some components of which are explored below.

• Resuscitation
• Risk assessment
• Supportive care and monitoring
• Investigations
• Decontamination
• Enhanced elimination
• Antidotes
• Disposition

Toxicology covers a wide range of presentations including deliberate self-poisoning, recreational drug misuse and abuse, accidental poisoning, occupational exposure and envenomation. Central to the management of the toxicology patient is risk assessment, as it will anticipate the poisoning severity and help guide treatment.

A thorough risk assessment is crucial in the approach to the toxicology patient and includes:

• Agent(s) taken
• Dose
• Time of ingestion
• Any co-ingestions
• Clinical manifestations since the exposure
• Regular medications
• Relevant co-morbidities - especially:
  • Renal or liver disease which may affect drug clearance.
  • Cardiac or respiratory disease which may increase toxicity for agents that cause cardiac or sedative effects.
  • Seizure history.

If the exposure is a deliberate self-poisoning, a mental health risk assessment should also be undertaken.

Patients are usually reliable when giving a risk assessment. In some scenarios – patient in custody, highly suicidal, using illicit drugs – there may be less willingness to divulge what was taken. In this instance, or if the patient is too sedated to give a history a collateral history can be taken from paramedics, family and friends. Empty pill packets on scene can be helpful to estimate a worst-case scenario. Sometimes contacting the patient’s regular doctor or getting a dispensing history from the patient’s chemist can be helpful to know what medications they may have access too. Access to electronic medical records can make this process easier.

Examination should be focused on the expected toxicity given the risk assessment. In the patient where the risk assessment is unclear, examination for specific toxidromes may be helpful in determining likely agents involved in the poisoning. The below table summaries the examination findings of common toxidromes.

Specific complications of poisoning should also be considered and sought on examination:

• Aspiration
• Pressure areas
• Neuropraxia
• Rhabdomyolysis
• DVT/PE

The following investigations may be useful.

Laboratory tests

• Blood gas analysis to assess gas exchange and metabolic disturbance particularly in patients with altered level of consciousness.
• Blood glucose especially important in those with an altered level of consciousness.
• Electrolytes, renal function, liver function tests.
• CK if rhabdomyolysis is suspected on risk assessment, particularly following long lie.

Toxicology tests

• Paracetamol concentration is often tested routinely when a patient is not alert enough to give a reliable risk assessment.
• Specific drug concentrations (e.g. valproate, carbamazepine, lithium) may be helpful if results are available in a clinically useful timeframe.
• Urinary drug screens have limited utility in a toxicology patient, they confirm the presence of some drug classes which are commonly misused, however false positives and negatives occur.

Cardiac investigations

• ECG assessing for QT prolongation or evidence of sodium channel blockade.
• Bedside echocardiography in patients with haemodynamic instability to determine the contribution of negative inotropy versus vasodilation.

Radiology studies

• CXR if evidence of aspiration.
• CT head if concerns for concurrent trauma or hypoxic brain injury.

More in depth description of some investigations can be found in appropriate sections (Bloods Gas Analysis , ECG) or in specific drug monographs.

Resuscitation should occur along standard lines such as the ABCDE approach.

Airway and Breathing
Certain drugs overdoses may cause a depressed level of consciousness. This can result in airway compromise, respiratory depression, hypoxemia, and hypercapnia. Airway adjuncts, oxygen therapies, or ventilation therapies may be required to correct these.

Circulation
Bedside echocardiography may be helpful to discriminate between negative inotropy from vasodilation as a cause of circulatory shock, to better guide inotropic and vasopressor therapy.

Disability (Neurological Status)
Hypoglycaemia should be corrected with glucose. Seizures, if they occur, should receive benzodiazepines in the first instance. Second line therapy is barbiturates.

Exposure/Environmental
Severe hyperthermia (>39°C) should be corrected with cooling techniques.

Cardio-respiratory arrest
In the event of cardio-respiratory arrest, advanced life support protocols should be provided. Prolonged resuscitation attempts are often advised as patients with poisonings are typically healthy before the exposure and the toxicity is likely to be reversible once peak toxicity has passed. Extracorporeal membrane oxygenation may have a role in refractory cardiac arrest due to poisoning and should be considered early where available.

Decontamination refers to techniques that reduce the exposure to a drug or toxin by reducing absorption. The use of decontamination methods should be based on a risk/benefit assessment. In those cases where the risk of toxicity is high decontamination should be given if the poisoning is amenable to it. Decontamination should always be a lower priority than resuscitation.

Methods of decontamination include:

• Activated charcoal
• Other binding resins
• Whole bowel irrigation
• Washing skin after dermal exposure

In general, decontamination can only be performed on a consenting patient. If it is felt the risk of the poisoning is so high that good supportive care or antidote therapy won’t result in a safe outcome it may be necessary to perform decontamination procedures even without consent. This would require intubation and ventilation in most cases.

Further information regarding decontamination techniques can be found here.

Enhanced elimination aims to reduce the severity and duration of an intoxication. As with decontamination, the decision to proceed with enhanced elimination techniques requires a thorough risk/benefit analysis and shouldn’t interfere with resuscitation or good supportive care. It is only available for ingestions with the toxicokinetics amenable to elimination, in particular the volume of distribution and clearance of the drug in question needs to be considered.

Methods of Enhanced Elimination include:

• Multi Dose Activated Charcoal
• Urinary Alkalinisation
• Extracorporeal Techniques

More in depth discussion of enhanced elimination techniques can be found here.

Antidotes for poisonings have existed for thousands of years and the term refers to a wide range of substances that ameliorate poisonings. Broad mechanisms of action of antidotes include reducing absorption, restoring function, or treating effects of poisoning. Examples of antidotes used currently are supplied in the following table (click to enlarge).

Good supportive care is the mainstay of managing the poisoned patient. It involves but is not limited to the following.

• Maintaining hydration with IV fluids
• Placing a urinary catheter if there is urinary retention
• Treating agitation with sedation (e.g. benzodiazepines)
• Adequate thromboprophylaxis
• Prevent of pressure area damage
• Treating nausea with antiemetics

Further Reading:

• PMID: 25929508. Buckley NA, Whyte IM, Dawson AH, Isbister GK. A prospective cohort study of trends in self-poisoning, Newcastle, Australia, 1987-2012: plus ça change, plus c'est la même chose. Med J Aust. 2015;202(8):438-442. doi:10.5694/mja14.01116 PDF
• Assessment and Management of the Poisoned Patient Video Summary Vimeo link
• PMID: 26816206. Buckley NA, Dawson AH, Juurlink DN, Isbister GK. Who gets antidotes? choosing the chosen few. Br J Clin Pharmacol. 2016;81(3):402-407. doi:10.1111/bcp.12894 PDF