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\begin{document}

\title{Whole bowel irrigation should not be used routinely in the management of
poisoned patients}



\author[1]{Euan Sandilands}%
\affil[1]{NPIS Edinburgh \& Royal Infirmary of Edinburgh}%


\vspace{-1em}



  
  \date{May 20, 2024}


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\begin{abstract}
Whole bowel irrigation is a method of gastric decontamination in the
poisoned patient involving administration of large volumes of
osmotically balanced polyethylene glycol-electrolyte solution to empty
the gastrointestinal tract of ingested toxins before absorption,
limiting systemic toxicity. While this approach may seem intuitive and
it can lead to expulsion of tablets or packets in the rectal effluent,
there is a lack of evidence correlating this with improved patient
outcomes. Administration of whole bowel irrigation is also challenging
to the inexperienced physician and associated with adverse effects,
which may be serious. Recommendations for the consideration of whole
bowel irrigation are limited to patients who have ingested modified
release preparations, those of have ingested pharmaceuticals not
adsorbed by activated charcoal, and for the removal of packages in body
packers. Until more robust evidence is available from high-quality
prospective studies demonstrating efficacy, the use of whole bowel
irrigation should not be used routinely in poisoned patients.%
\end{abstract}%



\sloppy


\textbf{Whole bowel irrigation should not be used routinely in the
management of poisoned patients}

Gastric decontamination is a cornerstone principle in the management of
poisoned patients. It is based on the theory that preventing absorption
of an ingested poison from the gastrointestinal (GI) tract will limit
systemic toxicity and reduce morbidity. The term gastric decontamination
encompasses several interventions all aimed at reducing gut absorption,
including gastric lavage to empty stomach contents, cathartics to
stimulate expectoration of toxins, activated charcoal to adsorb toxins
before systemic absorption, and irrigation of the GI tract to `washout'
toxins. For more than two decades, the safety and efficacy of these
methods has been debated {[}1-4{]}, with some interventions becoming
obsolete or rarely used due to significant associated adverse risk
{[}5,6{]}, while others, such as activated charcoal, being commonplace
in the early management of poisoned patients {[}7{]}.

Whole bowel irrigation (WBI) is a method of gastric decontamination
describing the administration of large volumes of osmotically balanced
polyethylene glycol-electrolyte solution (PEG-ES) to empty the GI tract
before absorption of potentially harmful toxins {[}8{]}. While the
theory of this approach appears intuitive, there is a paucity of
high-quality studies demonstrating beneficial outcomes in poisoned
patients. Administration of WBI is also complicated by adverse effects
and poor tolerability, due to the volumes of solution required (1-2
L/hour), often necessitating placement of a nasogastric tube. In the
absence of a robust evidence base, a consensus view from the European
Association of Poisons Centres and Clinical Toxicologists (EAPCCT) and
the American Academy of Clinical Toxicology (AACT) was published as a
joint position paper in 1997 {[}9{]} with updates in 2004 {[}10{]} and
2015 {[}11{]}. Recommendations for WBI include patients who have
ingested modified release pharmaceuticals, particularly in cases
presenting more than two hours after ingestion when activated charcoal
is less effective; after large ingestions of potentially highly toxic
agents not adsorbed by activated charcoal (e.g. iron, lithium); and for
the removal of ingested packets of illicit drugs in `body packers'
{[}11{]}. Despite these recommendations, there remains uncertainty
regarding appropriate utilization of WBI. Practical and ethical
considerations mean that undertaking randomized controlled trials would
be challenging. We must therefore rely on less robust evidence drawn
from volunteer studies, retrospective case series and case reports to
inform clinical practice {[}11,12{]}. Until such evidence can provide a
clear indication of clinical benefit, without significant adverse
effects, WBI should not be used routinely in the management of poisoned
patients but may be considered in specific scenarios.

Volunteer studies demonstrate WBI is associated with a significant
reduction in bioavailability of ampicillin (67\%) {[}13{]}, enteric
coated aspirin (73\%) {[}14{]}, and modified release lithium (67\%)
{[}15{]} when initiated within one hour of ingestion of 5g, 2.9g and
0.8mg/kg respectively. However, following therapeutic doses of sustained
release carbamazepine, theophylline and verapamil, no additional benefit
over activated charcoal alone was shown {[}16{]}. Indeed, in the case of
carbamazepine, administration of WBI was associated with a significant
reduction in the efficacy of activated charcoal {[}16{]}. Importantly,
volunteer studies cannot completely replicate the poisoned patient
scenario where ingested doses are significantly larger, the
pharmacokinetic properties of drugs may differ, and the effect of
co-administered interventions are not accounted for.

Analysing the effect of decontamination procedures on the
pharmacokinetics and pharmacodynamics of venlafaxine in overdose
demonstrated that activated charcoal increased clearance by 35\%, while
combined activated charcoal and WBI reduced bioavailability by 29\% and
was associated with lower venlafaxine peak concentrations {[}17{]}.
Kumar \emph{et al} {[}18{]} subsequently studied the relationship
between decontamination and the incidence of seizures. Activated
charcoal (OR: 0.48, 95\%CI: 0.25-0.89) and a combination of activated
charcoal and WBI (OR 0.25, 95\%CI: 0.08-0.62) reduced the likelihood of
seizures, with the combination providing greater overall benefit than
the sum of the independent effects {[}18{]}.

A recent retrospective multicentre study of 257 patients recommended for
WBI reported that of the 150 (58\%) patients to receive the
intervention, it was deemed successful (defined by obtaining diarrhoea
or evacuation of packets) in only 47 (31\%) cases {[}19{]}. The agents
ingested included lithium and other metals (e.g. potassium, iron), drug
packets, and multidrug ingestions (with our without cardiotoxic drugs).
Modified release tablets were involved in 81 (55\%) cases. Adverse
effects were reported in 27 (18\%) patients, with vomiting the
predominant feature (23 patients). Despite a low rate of completion, the
authors concluded that patients who were treated with WBI were less
likely to deteriorate than those not treated and that this clinical
benefit was associated with an acceptably low risk of complications.
However, the effect of any concomitantly administered interventions such
as supportive care, antidotes, inotropes, or vasopressors, were not
considered. Furthermore, the success of WBI was defined simply by the
presence of diarrhoea or evacuation of packets, rather than an improved
clinical outcome. Concluding the efficacy of WBI on this basis is
premature. These limitations were discussed by Vodovar \& Megarbane
{[}20{]} who highlighted the need for well-designed large prospective
cohort studies to provide robust evidence on which to base future
clinical recommendations.

Lack of outcome data, treatment-associated morbidity, and poor
tolerability are features of many other studies of WBI. A retrospective
review of 270 cases of sustained release ingestions treated with WBI
over a 6.5-year period demonstrated that only 57 (21\%) cases completed
treatment {[}21{]}. Activated charcoal was co-administered in 230 (85\%)
cases with no detail provided about the effect of this intervention.
Adverse events or treatment failure was reported in 68 (25\%) cases and
included vomiting, abdominal distension, hypotension, and patient
refusal. One death was recorded in a patient with abdominal distension
and hypotension following ingestion of diltiazem. In another
retrospective observational study of 59 patients with acute-on-chronic
lithium poisoning, Deguigne \emph{et al} {[}22{]} compared early
(\textless{}12 hours after ingestion) and late (\textgreater{}12 hours)
decontamination with sodium polystyrene sulfonate and/or WBI. While
early decontamination overall was associated with a more favourable
outcome, there was no difference for patients who received WBI either
alone or in combination with sodium polystyrene sulfonate. Lo \emph{et
al} {[}23{]} described 176 paediatric patients (age range 4 months to 12
years; mean 2 years) who received WBI. Common agents included calcium
channel blockers, iron and antidepressants, with 72 (41\%) cases
involving sustained release preparations. Abdominal x-rays confirmed the
presence of pills in 16 cases, four of which showed a reduction in
opacities on repeat imaging. Twelve patients (7\%) had documented pills
in their effluent. While the reduction of radiological opacities and
detection of pills in the effluent may be reassuring to the treating
physician, no clinical outcome data was available to support conclusions
about the efficacy of this intervention. Adverse effects, including
abdominal pain and vomiting, were reported in 10\% of patients.

The use of WBI to clear ingested packets of illicit drugs in body
packers represents a unique indication for this intervention
{[}24,25{]}. It is intuitive that hastening removal of packets of
potentially lethal drugs from the GI tract before rupture, leakage and
systemic absorption can occur would be advantageous. While a reduction
in hospital length of stay has been demonstrated in this patient group
(2.1 days when treated with WBI versus 2.8 days when treated with
laxatives {[}24{]}), there is again a lack of outcome data confirming
clinical benefit {[}24,26,27{]}. Administration of WBI in this patient
group is also frequently complicated by poor tolerability and treatment
refusal {[}24,26{]}.

Administration of WBI is challenging to the inexperienced physician and
not without risk. Nausea and vomiting, abdominal distension, bloating,
and pain are commonly reported in up to 10-25\% of patients
{[}19,23,26{]}. More serious adverse effects including hypotension,
aspiration, and even death may occur {[}28,29{]}. Treatment failure or
refusal is a significant problem due to poor tolerance of the quantities
of fluid required, often for many hours {[}19,21,23,24,26{]}. While a
nasogastric tube may ease practical administration, this is in itself
associated with adverse risks, including pulmonary aspiration secondary
to a misplaced tube {[}28,30{]}, emphasising the need for experienced
physicians.

In conclusion, there are no trials demonstrating improved outcomes
following WBI. In addition to retrospective case series and
observational studies, many case reports describing the use of WBI with
variable outcomes have been reported and reviewed in detail elsewhere
{[}11{]}. The limitations of data from case reports, however, are well
documented {[}31{]}, and without more high-quality randomized trials it
is difficult to draw definitive conclusions about efficacy. In addition
to the lack of outcome data, there are practical difficulties associated
with WBI administration and potentially serious adverse effects can
occur in up to 25\% of patients. Therefore, while there are some
specific scenarios where WBI may be considered beneficial based on the
best evidence currently available {[}11{]}, until such time as higher
quality randomised studies demonstrate improved outcomes for poisoned
patients in general, WBI should not be considered a routine treatment
for all.

\textbf{Data availability statement}

Data sharing not applicable to this article as no datasets were
generated or analysed during the current study.

Competing interests:

None declared.

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