Clinical Toxicology J.A

Postgrad Med J: first published as 10.1136/pgmj.69.807.19 on 1 January 1993. Downloaded from Postgrad Med J (1993) 69, 19 - 32 A) The Fellowship of Postgraduate Medicine, 1993 Reviews in Medicine Clinical toxicology J.A. Vale Director, National Poisons Information Service (Birmingham Centre), West Midlands Poisons Unit and Pesticide Monitoring Unit, Dudley Road Hospital, Birmingham B18 7QH, UK Introduction Selfpoisoning is the second most common cause of Much of the relevant literature relates to studies in acute medical presentation to hospital in the UK. volunteers given either a non-toxic marker or a However, as a result ofchanges over the last decade non-toxic dose ofa drug. As a result, the extrapola- both in the amount and type of agent ingested, the tion of many of these data to the poisoned patient majority of patients now suffer little if any adverse cannot be done with confidence. consequence and so require no active medical intervention. Nonetheless, a substantial minority Gastric lavage ofpoisoned patients do still require skilled medical management, often using the facilities of an inten- Although 'the idea of washing out the stomach sive care unit, if they are to survive without any with a syringe and tube, in cases where large important sequelae. Supportive therapy, including quantities oflaudanum and other poisons had been the correction of metabolic abnormalities, is of swallowed,' was first reported by Physick' in 1812 paramount importance in the care of such severely the value of gastric lavage remains controversial. by copyright. poisoned patients and this approach alone has Lavage performed 60 minutes after a therapeutic reduced the mortality significantly. Occasionally, dose (1 g) of aspirin had been administered to the use of a specific antidote will be life-saving but volunteers did not produce any significant reduc- in few patients is such treatment either appropriate tion in the absorption of aspirin2 as judged by or necessary. salicylate recovery in the urine. Similarly, no Procedures to reduce the absorption of ingested significant reduction in the area under the curve poisons have been employed widely for decades in relating plasma drug concentration to time after its the management ofintoxicated patients. However, administration (AUC) was noted after volunteers evidence of substantial clinical benefit to the had been subjected to lavage 60 minutes after the http://pmj.bmj.com/ majority of patients undergoing such treatment is administration of 5 g ampicillin.3 Tandberg et al.4 lacking. Moreover, there is no general agreement as found that lavage 10 minutes after the administra- to which therapeutic approach is best. In addition, tion of cyanocobalamin as a marker, resulted in a the value of procedures to increase elimination mean recovery of cyanocobalamin of 45 ± 13%; such as forced diuresis, dialysis and haemoper- this study, however, has little relevance to clinical fusion is also being questioned and there is much practice due to the very early use of lavage. present support for the use of activated charcoal Allan,5 after reviewing the use ofgastric lavage in both to reduce absorption and to increase elimina- 68 cases of barbiturate poisoning and finding that on September 30, 2021 by guest. Protected tion. an average ofonly 1 7 mg barbiturate was recover- This review will assess critically firstly, the value ed, concluded that the technique was 'potentially of gastric lavage, activated charcoal and syrup of dangerous in all cases and of no value in most'. It ipecacuanha in reducing poison absorption and was Matthew et al.6 who established, in patients secondly, the use ofprocedures to increase elimina- poisoned with barbiturates, that lavage less than 4 tion. hours post-overdose was likely to be more effica- cious than later lavage. However, only 37% of those lavaged early had more than 200 mg barbit- Reducing absorption urate recovered in the lavage fluid; in only 1% of patients lavaged after 4 hours was more than Unfortunately, few clinical studies have been per- 200 mg recovered. In the case of salicylate poison- formed to determine the most beneficial approach. ing, only 26% ofall patients lavaged had more than 1,000 mg recovered in the lavage fluid.6 Despite seemingly adequate lavage, drugs may Correspondence: J.A. Vale, M.D., F.R.C.P., F.F.O.M. be found in the stomach at post mortem but this is Postgrad Med J: first published as 10.1136/pgmj.69.807.19 on 1 January 1993. Downloaded from 20 J.A. VALE not surprising as even the largest bore orogastric practice are observed only infrequently. These tube may be inadequate to allow the removal of a include temporary cyanosis and laryngospasm dur- bezoar of tablet/capsule debris from the stomach. ing the procedure; conjunctival haemorrhages; Recent evidence indicates that even after lavage mechanical injury to the gut (though perforation is most (88%) patients may still have residual intra- exceedingly rare, occurring in approximately 1 in grastic solid.7 In addition, lavage may cause gastric 5,000 cases); aspiration pneumonia, which is par- contents to be discharged into the small bowel, ticularly likely to occur ifpetroleum distillates have thereby increasing the amount ofdrug available for been ingested and lavage is carried out without an absorption.8 Moreover, continued absorption of endotracheal tube in situ; water intoxication in drugs after lavage is known to occur.9 young children as a result of overzealous lavage; Comstock et al.9 evaluated the efficacy of lavage cardiac arrhythmias'4 and enhanced drug absorp- in 62 patients of whom 40% were lavaged within 2 tion.9 hours of overdose. Unfortunately, very limited drug sampling was undertaken and even before Syrup ofipecacuanha lavage therapeutic drug concentrations were present in 52% of patients. The authors concluded Syrup of ipecacuanha contains two alkaloids, that except in the case of tricyclic antidepressant emetine and cephaeline, which act upon the vomit- poisoning and massive overdose, poor recovery of ing centre after absorption; in addition, emetine is drug was likely if lavage was performed more than an impressive gastric irritant and causes vomiting 2 hours after overdose. Yet, in another study,'0 the usually within 30 minutes in ingestion. Provided mean amount of tricyclic antidepressant recovered that the dose of syrup of ipecacuanha is appropri- in 13 patients who were moderately or severely ate for the age of the patient, and a second dose is poisoned was only 109 mg at a mean time of 6 administered within 20 minutes if necessary, 100% hours post-overdose. of children'" and more than 90% of adults'6 will In a comparative study of volunteers, gastric vomit. lavage was shown to be significantly better than Syrup of ipecacuanha has been shown to reduce syrup ofipecacuanha in reducing drug absorption4 significantly the peak drug concentration (Cmax)by copyright. but of similar value to syrup ofipecacuanha in two and AUC of aminophylline,'7 cimetidine,'8 para- other studies,2'3 probably because the latter two cetamoli' and pindolol'8 if administered 5 minutes studies were performed at 60 minutes post-dosing, after a therapeutic dose of drug in volunteers. The whereas the first study involved assessment at 10 Cmax and AUC of tetracycline were also reduced minutes. significantly'7 when syrup of ipecacuanha was Auerbach et al." performed lavage on 37 administered both at 5 minutes and 30 minutes patients, 34 of whom were drowsy or obtunded post-dosing. The mean AUC of ampicillin3 and (comatosed) when the procedure was performed. A paracetamoli9 was also reduced significantly when further 51 patients, all of whom were fully cons- syrup of ipecacuanha was given 60 minutes after http://pmj.bmj.com/ cious, were each given syrup of ipecacuanha. Both drug dosing. However, it should be noted that in groups of patients received thiamine as a marker another study'7 the Cmax and AUC of paracetamol when lavage was performed or syrup of ipeca- were not reduced significantly when syrup of cuanha was administered. Thiamine recovery was ipecacuanha was given at 30 minutes. In the same significantly greater following lavage than after study,i7 syrup of ipecacuanha did not reduce syrup of ipecacuanha administration. Kulig et al.12 significantly the absorption ofaminophylline when assessed the value of gastric lavage in 72 obtunded it was given at 30 minutes. patients who also received supportive care and The recovery of urinary salicylate was signifi- on September 30, 2021 by guest. Protected activated charcoal. Gastric lavage led to a better cantly reduced by the administration of syrup of outcome only if performed within one hour of ipecacuanha 60 minutes post-dosing in one study20 ingestion of overdose. but not in another,2 possibly due to differences in A further study published recently'3 has assessed study design. Syrup ofipecacuanha reduced tilidine the value of aspiration (but not lavage) of stomach absorption when given at 3 minutes but not at 25 contents in 50 patients inebriated with alcohol. minutes.2' In three other volunteer studies, the Although a significant amount of ingested alcohol mean recovery of marker was 83% at 5 minutes,22 could occasionally be removed by this technique, 28-47% at 10 minutes,4'23 59% at 30 minutes and there was no way of identifying on presentation 44% at 60 minutes22 post-marker administration. It which patient would benefit and the routine use of is noteworthy that the recovery of marker in gastric emptying in the detoxification ofinebriated individual volunteers varied widely even when patients, therefore, cannot be recommended. syrup of ipecacuanha was administered soon after marker administration. The value of syrup of Complications ofuse The potential complications ipecacuanha has also been assessed in several of gastric lavage are well documented though in clinical studies. In the first two studies a marker was Postgrad Med J: first published as 10.1136/pgmj.69.807.19 on 1 January 1993.

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