Although unabsorbed drug in the stomach may be removed by gastric aspiration and lav­age its usefulness in practice has been seriously questioned (Proudfoot 1984). Most drugs and poisons seem to be absorbed rapidly and this technique is unlikely to be productive more than 4 hours after ingestion, unless gastric emptying has been delayed by opioid analgesics, anti­cholinergic agents, central nervous system de­pressants, and possibly salicylates. In such circumstances gastric lavage may be worthwhile up to 12 hours after ingestion.

It is said to be contraindicated after ingestion of corrosives and hydrocarbons such as paraffin because of the risks of perforation and lipoid pneumonia, respectively.

The patient must be correctly positioned head down in the left lateral position and a cuffed endotracheal tube inserted beforehand if the protective pharyngeal reflexes are depressed. It is essential to use a large bore tube (e.g. Jacques 30 gauge) and in adults lavage should be carried out with 300ml portions of warm tap water un­til the return is clear. Complications include pulmonary aspiration of stomach contents, and, rarely, oesophageal rupture.

Although gastric lavage is often unrewarding, large amounts of drug are occasionally re­covered. A common cause of failure is the use of too small a tube – an ordinary nasogastric tube is virtually useless. Large amounts of re­sidual drug have been found in the stomach postmortem after attempts at lavage with a nasogastric tube (Jenis et al. 1969), and in i case i large drug mass containing 25g of meproba­mate was removed by gastrotomy 40 hours after ingestion despite gastric lavage (Schwartz 1977).

Emetics

The comparative efficacy of induced emesis and gastric lavage is still debated. Neither guar­antees emptying of the stomach. Lavage is not always practicable in children because of the physical difficulty in passing a tube large enough to allow the passage of tablets, and emesis is probably preferable in young children. In 1 study in children poisoned with salicylates, emesis was claimed to be more effective than lavage (Boxer et al. 1969), but in another, only 10 to 15% of the amount of salicylate taken was recovered, even when emesis occurred within 1 hour of ingestion (Yaffe et al. 1970).

The major disadvantages are failure of eme­sis, particularly if central nervous system de­pressants have been taken, and toxicity, some­times fatal, from the retained emetic. Syrup of ipecac given with water is probably the best emetic, and is often effective within 15 to 30 minutes (Neuvonen et al. 1983).

Other agents which have been used include sodium chloride, copper sulphate, zinc sulphate, tartar emetic (antimony potassium tartrate), apomorphine and mustard. However, the over-enthusiastic use of sodium chloride and heavy metals can be ex­tremely dangerous and fatal poisoning with salt and copper sulphate has been reported (Gresham & Mashru 1982; Stein et al. 1976).