Emesis: a thing of the past?

Until I started researching this Tip of The Week, I did not know the medical profession has abandoned the routine use of emesis in oral poisoning.

This is based on multiple medical literatures that have proven emesis induction does not influence the clinical severity of poisoning, the length of hospitalisation and the clinical outcome or mortality.

Although the rationale for inducing emesis is obvious, it is not necessarily evidence based. It is also dependent on satisfying a few large assumptions, all of which are untrue:

• Emesis is a very effective way of removing gastric contents.
• No separation exists of poison from its vehicle while inside the acidic environment of the stomach.
• Poison is not absorbed through the stomach wall.

Ineffective method

Emesis induction is an ineffective way of clearing stomach contents. A review of the effectiveness of induced emesis, with both human and canine participants, showed at 30 minutes post-ingestion of non-absorbable markers, the recovery rate averaged between 17.5% and 52.1%, but never exceeded 62%.

In fasted puppies, this was even lower at 2% to 31%, despite inducing emesis immediately after marker administration. These have been confirmed by the presence of poisonous materials in the stomach of dead patients, despite effective emesis induction until clear fluid was brought up.

The clinical outcome only improves if the systemic exposure of a toxicant is reduced by more than half. However, considering animals rarely practice restraint, the ingested amount is unlikely to be exactly the lethal dose and no more. Therefore, even reducing the ingested toxic dose by 62% is unlikely to make a clinical difference.

Furthermore, most patients rarely present within 30 minutes of ingesting a toxicant, thus further reducing its efficiency.

The absorption conundrum

Some may argue the retrieval of metaldehyde or anticoagulant rodenticide granules from vomitus is indicative of reducing the toxicant dose. This could be true, but only if emesis was induced immediately after ingesting the poison.

The poison itself is colourless and has a different absorption characteristic to the coloured vehicle (granule); therefore, the presence of granule only serves to confirm ingestion, but is of no indication whether the poison has already been absorbed.

Contraindications

Many well-recognised absolute contraindications also exist to inducing vomiting:

• Ingestion of oils, which includes waxes that melt to oil in the internal body environment, as this poses a high risk of lipoid and bacterial pneumonia. This is of significant veterinary significance, as wax is routinely used in rodenticide baits.
• Ingestion of hydrocarbons and other volatile substances, or caustic or corrosive substances.
• When the mental status is altered – for example, hyperexcitable or depressed mental state.
• Where the patient is at risk of seizures (seizures can be induced by emesis).
• Increased intracranial pressure.
• Risk of intracranial or cerebral haemorrhage – for example, thrombocytopenia or abnormal clotting parameters.

Other less severe, yet important, reasons include:

• delays administration of more effective treatment, such as activated charcoal, antidote or other treatments
• risk of aspiration pneumonia
• hypochloraemia in recurrent emetic patients
• significant CNS and respiratory depression from apomorphine
• rare, but reported, complications such as cerebral haemorrhage, oesophageal tear/ rupture, hiatal hernia, gastric rupture, pneumothorax and pneumomediastinum
• legal implications – for example, if the product information clearly states emesis should not be induced

A place for everything

Emesis induction is not a benign procedure. It still has its place in certain circumstances, but its use in the routine management of oral poisonings may need to be reconsidered – especially if it means delaying administration of a more effective treatment, such as activated charcoal.

So, after all this, how do I tackle this information? It is a bit hard to swallow. My clinical experience is emesis is generally safe, especially in canine patients using apomorphine. So, I still feel some merit exists in reducing the amount of toxicant in the stomach if you have a chance – and in some situations, you don’t know until you try.

Emesis after ingestion of a toxic dose of chocolate can be incredibly rewarding, even six hours after ingestion, leading to patients not developing clinical signs at all.

Overall, I am biased by my personal successes with emesis, so still feel a time and place exist for emesis induction. But I now stop and question my decision to induce emesis, whereas I did not hesitate before.

• Some drugs listed are used under the cascade.