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Chapter: Modern Medical Toxicology: General Principles: General Management of Poisoning

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Decontamination - General Management of Poisoning

– Emesis – Gastric Lavage (Stomach Wash) – Catharsis – Activated (Medicinal) Charcoal – Whole Bowel Irrigation (Whole Gut Lavage)

Decontamination

EYE

Irrigate copiously for at least 15 to 20 minutes with normal saline or water. Do not use acid or alkaline irrigating solutions. As a first-aid measure at home, a victim of chemical burns should be instructed to place his face under running water or in a shower while holding the eyelids open. During transportation to hospital the face should be immersed in a basin of water (while ensuring that the patient does not inhale water).

SKIN

Cutaneous absorption is a common occurrence especially with reference to industrial and agricultural substances such as phenol, hydrocyanic acid, aniline, organic metallic compounds, phosphorus, and most of the pesticides. The following measures can be undertaken to minimise absorption*—

■■  Exposed persons should rinse with cold water and then wash thoroughly with a non-germicidal soap. Repeat the rinse with cold water.

■■  Corroded areas should be irrigated copiously with water or saline for at least 15 minutes. Do not use “neutralising solutions”.

■■  Remove all contaminated clothes. It is preferable to strip the patient completely and provide fresh clothes, or cover with clean bedsheet.

■■  Some chemical exposures require special treatment :

·     Phenolic burns should be treated by application of polyethylene.

·     Phosphorus burns should be treated with copper sulfate solution.

·     For hydrofluoric acid burns, use of intradermal or intra-arterial calcium gluconate decreases tissue necrosis.

·     For tar, bitumen, or asphalt burns, first irrigate the affected skin with cold water and then clean and apply solvents such as kerosene, petrol, ethanol, or acetone. However, since these substances can not only be locally cytotoxic, but also be absorbed through the skin, it is preferable to use mineral oil, petrolatum, or antibacte-rial ointments in a petrolatum base. Prolonged irrigating applications may be required.

GUT

The various methods of poison removal from the gastrointes-tinal tract include:

■■  Emesis

■■  Gastric lavage

■■  Catharsis

■■  Activated charcoal

■■Whole bowel irrigation

Emesis

The only recommended method of inducing a poisoned patient to vomit is administration of syrup of ipecacuanha (or ipecac). However, the initial enthusiasm associated with the use of ipecac in the 1960s and 1970s in western countries has declined substantially in recent years owing to doubts being raised as to its actual efficacy and safety. The current consensus is thatsyrup of ipecac must NOT be used, except in justifiable circumstances.


Syrup of Ipecac

·              Source—Root of a small shrub (Cephaelis ipecacuanha or C. acuminata) which grows well in West Bengal (Fig 3.1).

·              Active principles: Cephaeline, emetine, and traces of psychotrine.

·              Indications: Conscious and alert poisoned patient who has ingested a poison not more than 4 to 6 hours earlier.

·              Mode of action:

o     Local activation of peripheral sensory receptors in the gastrointestinal tract.

o     Central stimulation of the chemoreceptor trigger zone with subsequent activation of the central vomiting centre.

·              Dose:

o     30 ml (adult), or 15 ml (child), followed by 8 to 16 ounces, i.e. 250 to 500 ml approximately, of water.

o     The patient should be sitting up.

o     If vomiting does not occur within 30 minutes, repeat the same dose once more. If there is still no effect, perform stomach wash to remove not only the ingested poison but also the ipecac consumed. However the therapeutic doses of ipecac recommended above are not really harmful.

Contra-indications:

·              Relative :

–– Very young (less than 1 year), or very old patient –– Pregnancy

––  Heart disease

––  Bleeding diathesis

––  Ingestion of cardiotoxic poison

––  Time lapse of more than 6 to 8 hours

·              Absolute :

–– Convulsions, or ingestion of a convulsant poison –– Impaired gag reflex

––  Coma

–– Foreign body ingestion –– Corrosive ingestion

–– Ingestion of petroleum distillates, or those drugs which cause altered mental status (phenothiazines, antihistamines, opiates, ethanol, benzodiazepines, tricyclics).

–– All poisons which are themselves emetic in nature

·              Complications:

 Cardiotoxicity (bradycardia, atrial fibrillation, myocar- ditis).

 Aspiration pneumonia.

 Oesophageal mucosal or Mallory Weiss tears (due toprotracted vomiting).

Other Emetics

The only other acceptable method of inducing emesis that is advocated involves the use of apomorphine. Given subcu-taneously, it causes vomiting within 3 to 5 minutes by acting directly on the chemoreceptor trigger zone. The recommended dose is 6 mg (adult), and 1 to 2 mg (child). Since apomorphine is a respiratory depressant it is contraindicated in all situations where there is likelihood of CNS depression.

In some cases, stimulation of the posterior pharynx with a finger or a blunt object may induce vomiting by provoking the gag reflex. Unfortunately, such mechanically induced evacua-tion is often unsuccessful and incomplete, with mean volume of vomitus about one third of that obtained by the other two methods.

Obsolete Emetics

The use of warm saline or mustard water as an emetic is not only dangerous (resulting often in severe hypernatraemia), but also impractical since many patients, especially children refuse (fortunately) to drink this type of concoction and much valuable time is lost coaxing them to do so. One tablespoon of salt contains at least 250 mEq of sodium, and if absorbed can raise the serum level by 25 mEq/L in for instance, a 3-year old child.* It is high time that the use of salt water as an emetic be deleted once and for all from every first-aid chart or manual on poisoning.

Copper sulfate induces emesis more often than commonsalt, but significant elevations of serum copper can occur leading to renal and hepatic damage. It is also a gastrointestinal corrosive.

Zinc sulfate is similar in toxicity to copper sulfate, and hasin addition a very narrow margin of safety.

Gastric Lavage (Stomach Wash)

The American Academy of Clinical Toxicology (AACT), and the European Association of Poison Centres and Clinical Toxicology (EAPCCT) have prepared a draft of a position paper directed to the use of gastric lavage, which suggests that gastric lavage should not be employed routinely in the management of poisoned patients. There is no certain evidence that its use improves outcome, while the fact that it can cause significant morbidity (and sometimes mortality) is indisputable. Lavage should be considered only if a patient has ingested a life-threatening amount of a poison and presents to the hospital within 1 to 2 hours of ingestion.

But in India, very often caution is thrown to the wind and the average physician in an average hospital embarks on gastric lavage with gusto the moment a poisoned patient is brought in. A sad commentary on the existing lack of awareness and a reluctance to change old convictions in spite of mounting evidence against the routine employment of such “established procedures”.

 

■■   Indications—

·              Gastric lavage is recommended mainly for patients whohave ingested a life-threatening dose, orWho exhibit significant morbidity and present within1 to 2 hours of ingestion. Lavage beyond this periodmay be appropriate only in the presence of gastricconcretions, delayed gastric emptying, or sustainedrelease preparations. Some authorities still recommendlavage upto 6 to 12 hours post-ingestion in the case ofsalicylates, tricyclics, carbamazepine, and barbiturates

·              Precautions—

o     Never undertake lavage in a patient who has ingested a non-toxic agent, or a non-toxic amount of a toxic agent.

o     Never use lavage as a deterrent to subsequent inges- tions. Such a notion is barbaric, besides being incorrect.

·              Contraindications—

o     Relative: Haemorrhagic diathesis, oesophageal varices, recent surgery, advanced pregnancy, ingestion of alkali, coma.

o     Absolute: Marked hypothermia, prior significant vomiting, unprotected airway in coma, and ingestion of acid or convulsant or petroleum distillate, and sharp substances.

·              Procedure—

o     Explain the exact procedure to the patient and obtain his consent. If refused, it is better not to undertake lavage because it will amount to an assault, besides increasing the risk of complications due to active non-co-operation.

o     Endotracheal intubation must be done prior to lavage in the comatose patient.

o     Place the patient head down on his left lateral side (20o tilt on the table).

o     Mark the length of tube to be inserted (50 cm for an adult, 25 cm for a child).*\

o     The ideal tube for lavage is the lavacuator (clear plastic or gastric hose).

o     In India however, the Ewald tube is most often used which is a soft rubber tube with a funnel at one end (Fig 3.2). Whatever tube is used, make sure that the inner diameter corresponds to at least 36 to 40 French size.** A nasogastric tube used for gastric aspiration is inadequate and should never be used. In a child, the diameter should be at least 22 to 28 French, (Ryle’s tube may be sufficient – Fig 3.3).



o     The preferred route of insertion is oral. Passing the tube nasally can damage the nasal mucosa considerably and lead to severe epistaxis. Lubricate the inserting end of the tube with vaseline or glycerine, and pass it to the desired extent. Use a mouth gag so that the patient will not bite on the tube.

o     Once the tube has been inserted, its position should be checked either by air insufflation while listening over the stomach, or by aspiration with pH testing of the aspirate, (acidic if properly positioned).

o     Lavage is carried out using small aliquots (quantities) of liquid. In an adult, 200 to 300 ml aliquots of warm (38o C) saline or plain water are used. In a child, 10 to 15 ml/kg body weight of warm saline is used each time. Water should preferably be avoided in young children because of the risk of inducing hyponatraemia and water intoxication. It is advisable to hold back the first aliquot of washing for chemical analysis.

o     In certain specific types of poisoning, special solutions may be used in place of water or saline (Table 3.17).


o     Lavage should be continued until no further particulate matter is seen, and the efferent lavage solution is clear. At the end of lavage, pour a slurry of activated charcoal in water (1 gm/kg), and an appropriate dose of an ionic cathartic into the stomach, and then remove the tube.

Complications –

·              Aspiration pneumonia.

·              Laryngospasm.

·              Sinus bradycardia and ST elevation on the ECG.

·              Perforation of stomach or oesophagus (rare).

Catharsis

Catharsis is a very appropriate term when used in connection with poisoning, since it means purification. It is achieved by purging the gastrointestinal tract (particularly the bowel) of all poisonous material.

The two main groups of cathartics* used in toxicology include

·               Ionic or Saline:

–– These cathartics alter physico-chemical forces within the intestinal lumen leading to osmotic retention of fluid which activates motility reflexes and enhances expulsion. However, excessive doses of magnesium-based cathartics can lead to hypermagnesaemia which is a serious complication.

–– The doses of recommended cathartics are as follows:

--  Magnesium citrate: 4 ml/kg

-- Magnesium sulfate: 30 gm (250 mg/kg in a child)

--  Sodium sulfate: 30 gm (250 mg/kg in a child).

·              Saccharides:

–– Sorbitol (D-glucitol) is the cathartic of choice in adults because of better efficacy than saline cathartics, but must not be used as far as possible in young children owing to risk of fluid and electrolyte imbalance (especially hypernatraemia).

–– It occurs naturally in many ripe fruits and is prepared industrially from glucose, retaining about 60% of its sweetness. Sorbitol is used as a sweetener in some medicinal syrups, and the danger of complications is enhanced in overdose with such medications when sorbitol is used as a cathartic during treatment.

––  Dose of sorbitol: 50 ml of 70% solution (adult).

·              Efficacy of catharsis:

While cathartics do reduce the transit time of drugs in the gastrointestinal tract, there is no real evidence that it improves morbidity or mortality in cases of poisoning.

·              Contraindications:

––  Corrosives

–– Existing electrolyte imbalance

–– Paralytic ileus

––  Severe diarrhoea

–– Recent bowel surgery

–– Abdominal trauma

–– Renal failure.

Oil based cathartics should never be used in poisoning since they increase the risk of lipoid pneumonia, increase the absorption of fat soluble poisons, and inactivate medicinal charcoal’s effects when administered along with them. The last mentioned reason also applies to conventional laxatives, and hence they are also not recommended in poisoning.

Activated (Medicinal) Charcoal

A number of studies have documented clearly the efficacy of activated charcoal as the sole decontamination measure in ingested poisoning, while emesis and lavage are increasingly being associated with relative futility.

Activated charcoal is a fine, black, odourless, tasteless powder (Fig 3.4) made from burning wood, coconut shell, bone, sucrose, or rice starch, followed by treatment with an activating agent (steam, carbon dioxide, etc.). The resulting particles are extremely small, but have an extremely large surface area. Each gram of activated charcoal works out to a surface area of 1000 square metres.


·     Mode of action—

Decreases the absorption of various poisons by adsorbing them on to its surface (Fig 3.5). Activated charcoal is effec-tive to varying extent, depending on the nature of substance ingested (Table 3.18).




·              Dose—

       1 gm/kg body weight (usually 50 to 100 gm in an adult, 10 to 30 gm in a child).

·              Procedure—

·              Activated charcoal is most effective when administered within one hour of ingestion. Administration in the  prehospital setting has the potential to significantly decrease the time from toxin ingestion to activated charcoal administration, although it has not been shown to affect outcome.

·              Add four to eight times the quantity of water to the calculated dose of activated charcoal, and mix to produce a slurry or suspension. This is administered to the patient after emesis or lavage, or as sole inter- vention. The slurry should be shaken well before administration.

Multiple-dose Activated Charcoal: The use of repeated doses (amounting to 150 to 200 gm of activated charcoal) has been demonstrated to be very effective in the elimination of certain drugs such as theophylline, phenobarbitone, quinine, digitoxin, phenylbutazone, salicylates and carbamazepine. The actual dose of activated charcoal for multiple dosing has varied consider- ably in the available medical literature, ranging from 0.25 to 0.5 gm/kg every 1 to 6 hours, to 20 to 60 gm for adults every 1, 2, 4, or 6 hours. The total dose administered is more important than frequency of administration.

·              Disadvantages—

o     Unpleasant taste*

o     Provocation of vomiting

o     Pulmonary aspiration

o     Intestinal obstruction (especially with multiple-dose activated charcoal).

·              Contraindications—

o     Absent bowel sounds or proven ileus

o     Small bowel obstruction

o      Caustic ingestion

o      Ingestion of petroleum distillates.

Whole Bowel Irrigation (Whole Gut Lavage)

This is a method that is being increasingly recommended for late presenting overdoses when several hours have elapsed since ingestion. It involves the instillation of large volumes of a suit-able solution into the stomach in a nasogastric tube over a period of 2 to 6 hours producing voluminous diarrhoea. Previously, saline was recommended for the procedure but it resulted in electrolyte and fluid imbalance. Today, special solutions are used such as PEG-ELS ( i.e. polyethylene glycol and electro-lytes lavage solution combined together, which is an isosmolar electrolyte solution), and PEG-3350 (high molecular weight polyethylene glycol) which are safe and efficacious, without producing any significant changes in serum electrolytes, serum osmolality, body weight, or haematocrit.

·              Indications—

·              Ingestion of large amounts of toxic drugs in patients presenting late ( > 4 hours post-exposure)

·              Overdose with sustained-release preparations.

·              Ingestion of substances not adsorbed by activated char- coal, particularly heavy metals.

·              Ingestion of foreign bodies such as miniature disc batteries (button cells), cocaine filled packets (body packer syndrome),** etc.

·              Ingestion of slowly dissolving substances: iron tablets, paint chips, bezoars, concretions, etc.

·              Procedure—

·              Insert a nasogastric tube into the stomach and instil one of the recommended solutions at room temperature, at a rate of 2 litres per hour in adults, and 0.5 litre per hour in children. The patient should preferably be seated in a commode. The use of metoclopramide IV, (10 mg in adults, 0.1 to 0.3 mg/ kg in children) can minimise the incidence of vomiting. The procedure should be continued until the rectal effluent is clear, which usually occurs in about 2 to 6 hours.

·              Complications—

o     Vomiting

o     Abdominal distension and cramps

o     Anal irritation.

·              Contraindications—

o     Gastrointestinal pathology such as obstruction, ileus, haemorrhage, or perforation.


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