Decontamination

Introduction

Decontamination refers to techniques that reduce the exposure to a drug or toxin by reducing absorption.

Virtually all actions in clinical toxicology should be based on a risk/benefit assessment.

Decontamination should always be a lower priority than patient resuscitation.

Methods of decontamination include:

  • Induced emesis
  • Gastric lavage
  • Activated charcoal
  • 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 under the Guardianship Act. This would require intubation and ventilation in most cases.

Induced emesis

Induced emesis is no longer recommended. It is usually achieved through administrating Syrup of Ipecac, a powerful plant derived emetic. It is only effective if given early- within one hour of ingestion. It is unpleasant for the patient and has not been shown to be as superior to activated charcoal, which is much better tolerated. There is also the potential for aspiration, pneumomediastinum and gastric perforation. It is not currently recommended.

Gastric lavage

Gastric lavage is no longer recommended, it attempts to clear the stomach by administration and then aspiration of small volumes of fluid via a large orogastric tube.  Like most methods of decontamination, its effectiveness is greatly reduced more than one hour following poisoning.   A large bore OGT is gently inserted prior to administering 200mL aliquots of warm tap water.  This fluid is then drained into a container on the ground adjacent to the bed via gravity.  This can be repeated until the effluent is clear.  It is poorly tolerated in the non-intubated patient and not superior to activated charcoal.  There is a risk of aspiration, oesophageal trauma and water intoxication.  It is not currently recommended and contraindicated in cases of caustic or hydrocarbon ingestions. If a patient requires intubation, it is reasonable drain the stomach contents following placement of the gastric tube.

Activated Charcoal

Porous charcoal has a large surface area that adsorbs most toxins. It is the preferred method for gastrointestinal decontamination.

Its effectiveness decreases sharply with time. If given within 30 minutes of ingestion, charcoal may decrease the absorption of the ingested compound by up to 70%, this drops to 35% after 1 hour.

Drugs not bound by charcoal:

  • Hydrocarbons
  • Alcohols
  • Metals, including Li+ and K+
  • Corrosives

Offer to alert co-operative patients presenting within two hours of ingestion.

It can be offered up to four hours following ingestions of slow release preparations.

Rx 50g or 1g/kg activated charcoal PO/NGT

Complications of activated charcoal

  • Vomiting
  • Aspiration

Whole Bowel Irrigation

WBI physically flushes substances from the gastrointestinal tract using large volumes of polyethylene glycol solution until the effluent runs clear.

While WBI is very effective, the practicalities of its implementation have meant that its use is largely limited to specific poisonings where activated charcoal alone is not satisfactory.

Situations amenable to WBI:

  • Poisoning with sustained release preparations (e.g. verapamil, diltiazem)
  • Poisoning with medications not absorbed by charcoal (eg iron, lithium, potassium)
  • Body packers

Rx       1- 1.5L/h of PEG solution PO or via NGT (GoLytely),

(25mL/kg/h if paediatric patient)

Continue until the effluent runs clear – which usually occurs following approximately 5L of fluid. Often an antiemetic such as ondansetron or metoclopramide will need to be charted.

WBI should not be performed in haemodynamically unstable patients.

Complications of WBI:

  • Normal AG metabolic acidosis
  • Aspiration
  • Distraction from resuscitative priorities

 Further reading

References

  • Albertson TE, Owen K et al. Gastrointestinal decontamination in the acutely poisoned patient. International Journal of Emergency Medicine 2011, 4:65