A medical practitioner should have an emergency case ready for cases of poisoning, in order that he could also be able to adopt immediate treatment without loss of your time.
Unlike the average clinical case, many overdosed patients are brought to dispensary/hospital in a unconscious/semiconscious condition. Even if a poisoned patient is conscious and alert, he/she is typically uncooperative and even hostile, since the bulk of hospital admissions are cases of attempted suicide. Added to those problems is that the unfortunate absence of specific signs and symptoms regarding many poisonous substances. The adage ‘treat the patient and not the poison’ is sort of relevant in toxicological cases. Many poisoned patients will recover with simple treatment.
A minority may require intensive care. It is required to send samples of blood, urine, vomitus, etc. to the closest Forensic Lab for analysis. Sodium chloride is sufficient as a preservative, though sodium fluoride is preferred for the blood sample.
The main objects include
(i ) removal of unabsorbed poison,
(ii ) Elimination of absorbed poison,
(iii ) administration of antidotes and
(iv) treatment of general symptoms.
BASIC PRINCIPLES OF POISONING
MANAGEMENT Supportive Care
Treatment of seizures
Correction of temperature abnormalities
Correction of metabolic derangements
Prevention of secondary complications
Removal of Unabsorbed Poison
– Induced emesis
– Gastric lavage
Hastening Elimination of Absorbed Poison
Interruption of Enterohepatic Circulation
Forced alkaline diuresis
Administration of Antidotes
- Using mechanical (physical) antidotes
- chemical antidotes
- Chelation therapy
Some of these are explained as follows.
Removal of Unabsorbed Poison
Depending upon the route of entry, the subsequent principles should be applied.
When a poison has been inhaled, like carbon monoxide gas, automobile exhaust, gas from a tank, etc., the patient should immediately be removed to fresh air to chase out the poisonous gas through the lungs. A clear airway should be ensured.
If the poison has been injected, use of tourniquets, proximal to the point of injection may slow down the absorption. Some unabsorbed poison may need to be removed through multiple incisions and suction, almost like that commonly advised for snake bite.
If a poison comes in contact with skin, eye or wound or be inserted into vagina or urinary bladder, the suitable way is to wash it out with plain warm water. If a selected antidote is understood, the poisons are often neutralised.
The objective is to remove the poison from the gastrointestinal tract as soon as possible. Efforts should be made to minimize or stop its absorption by gastrointestinal decontamination. Whether or to not perform gastrointestinal decontamination and which procedure to use depends on the time since ingestion, the existing and predicted toxicity of the ingestant; the supply, efficacy and contraindications of the procedure; and therefore the nature, severity and risk of complications. The mode of gastrointestinal decontamination includes the gastric lavage.
Gastric Lavage (Stomach Wash)
It is useful any time wihin 3 hours after ingestion of a poison. It is done employing a stomach tube (Ewald’s or Boa’s, tube) or ordinary soft, non-collapsible rubber tube of 1 em. diameter and one-and-half metre length, with a glass funnel attached at one end, and a mark about 50 em. from the other end, which should be rounded with lateral openings to avoid any injury when it is being passed. At about the midpart of the tube there is a suction bulb, used to pump out the stomach contents.
A wooden mouth gag has a hole at its mid-part to allow the passage of the tube through it. One end of the gag is pointed s that it can be forcefully inserted by the side of the mouth in non-cooperative patients. Dentures must be removed and a mouth gag is placed in right position in between the teeth of two jaws, in order that the teeth do not bite the tube.
Care should be taken in unconscious persons, who are likely to regurgitate and then aspirate stomach contents into respiratory tract and die from asphyxia. Patient should be lying on his left side or prone with head hanging over the sting of the bed, and face down supported by an assistant, so that the mouth is at a lower level than larynx, so that any fluid which may leak out through the sides of the tube will not trickle down inside the larynx and trachea.
The end is lubricated with olive or sweet oil, liquid paraffin or glycerine, and is passed into the stomach by depressing the tongue with two fingers or tongue depressor, and slowly passing it downwards through the pharynx and oesophagus into the stomach, till the 50 em. mark is reached. If there (jl”e no marks on the tube, the tube should be passed for a distance ediquate to that measured between the bridge of the nose and •be tip of the xiphoid process.
Force must not be wont to insert the tube. Absence of coughing and of breath sounds in the funnel will confirm that the tube has not entered into the trachea. Whenever in doubt, test by keeping the free end of the tube just below a water surface. Air from the stomach is usually expelled completely in 2 to 3 expirations, whereas air from the lungs causes bubbling at each expiration.
About one-fourth litre of warm water (35’C) should be passed through the funnel held high up above the patient head. When funnel is empty, compress the tube below it between the finger and thumb and lower it below the level of the stomach, and its contents will be emptied by syphon action on releasing the pressure rubber tubing. If stomach pump is used applying suction on the bulb will iphon the stomach contents.
stomach contents can be aspirated by a 20 ml. syringe. Preserve this for chemical analysis. If there is any bleeding, abandon the procedure. Gastric lavage may be done with water; 1:5000 potassium permanganate; five per cent sodium bicarbonate ; four percent tannic acid; one percent sodium or potassium iodide; one to three percent calcium lactate; saturated lime water or starch solution, or 0.9% saline. Next, use about half litre of suitable solution and repeat till clear and odourless fluid comes out. This indicates that there is no further interaction between the antidote and poison.
At this stage, the stomach is not completely emptied but a small quantity of the fluid containing the antidote or activated charcoal suspension (one gm/ kg body weight, or/and a cathartic) is left behind in the stomach, so that it may neutralise whatever small quantity of the poison is left behind. Ryle’s tube or a number 10 to 12 French catheter can be used for infants and children, and about 25 em. is necessary to reach the stomach. After a recent heavy meal, the bulky contents are first removed by emetics. Stomach wash is better than emesis because of the discomfort caused to the patient in vomiting In poisoning with salicylates, phenothiazines, tricyclic antidepressants, antihistamines, lavage can be done up to 12 to 18 hours after ingestion of the poison.
Elimination of Absorbed Poison
Once a poison has been absorbed, its systemic effects are often reduced by accelerating its removal from the body. Various techniques employed to reinforce the elimination of poisons from the body are discussed below:
Interruption of Enterohepatic Circulation
A few poisons are secreted into the bile and are reabsorbed within the gut. This is referred to as enterohepatic circulation and may be seen in phenobarbital, carbamazepine, glutethimide and a few organochlorine poisonings. Cholestyramine reduces this reabsorption by binding with the poison within the gut thereby reducing the plasma concentration of the poison.
Haemodialysis: it is very useful for removing ethanol, methanol, ethylene glycol, chloral hydrate, lithium, trivalent arsenic, bromides, salicylates, fluoride, boric acid, digitalis etc.
Forced alkaline diuresis: achieving a urinary pH of 7.5 to 9 promotes excretion of drugs that are weak acids such as salicylates, methotrexate, chlorphopamide etc. A solution of sodium bicarbonate 50 -100 meq. Added to one litre of 0.45% saline may be administered at the rate of 250-500 ml/hr for the first 1 to 2 hrs. Alkaline solution and diuretics should be administered to take care of a urinary output of two to three ml/kg/hr.
Renal excretion: it’s going to be improved by giving great amount of fluid, tea or lemonade orally. Forced dieresis may cause pulmonary or cerebral oedema. Urinary acidification is not recommended.
Administration of Antidotes
An antidote is defined in Webster’s New desk Dictionary as a remedy to counteract the consequences of a poison. Remedies, in this sense, are usually visualised to be specific chemical entities but this definition may be broadened to include nonspecific measures such as charcoal haemoperfusion, dialysis and so on. Specific therapy of a case of poisoning involves the utilisation of antidotes that prevent the pathophysiology produced by a toxin. According to their modes of action, they’ll be enumerated as follows.
Physical or Mechanical Antidote
They neutralize the poison by mechanical action or prevent their absorption. Examples may include: demulcents like egg albumin, starch or barley water or may be milk. They have a soothing action and form a protective layer on the mucosa of the stomach to guard it from the action of poison.
Adsorbents like activated animal charcoal that acts mechanically by adsorbing and retaining within its pores organic, and also to a less degree mineral poisons, and thus delays the absorption from the stomach (e.g. alkaloids). Diluents like water or milk or similar drinks that dilute the poison and therein way delay absorption. Bulky food like boiled rice or boiled vegetables act as a medical antidote to glass powder by imprisoning its particles within its meshes, and thus prevent damage being affected by the sharp glass particles.
Chemical antidote: They prevent the action of poison by forming harmless or insoluble compounds or by oxidising poison when brought into contact with them.
(1) Common salt decomposes nitrate by direct chemical process, forming the insoluble chloride.
(2) Albumen precipitates mercuric chloride.
(3) Dialysed iron is employed to neutralise arsenic.
(4) Copper sulphate is employed to precipitate phosphorus.
(5) Potassium perrnanganate has oxidising properties.
1:5000 solution is used in poisoning for opium and its derivatives, strychnine, phosphorus, hydrocyanic acid, cyanides,etc. When it reacts with the poison in the stomach, it loses its pink colour. The wash must be continued till the solution coming out of the stomach is of the same pink colour as the solution put in.
(6)A solution of tincture iodine or Lugol’s iodine 15 add to half a glass of warm water precipitates almost all
alkaloids, lead, mercury, silver, quinine and strychnine.
(7) Tannic acid 4%, or tannin in the form of a strong tea or one teaspoonful of tannic acid in water tends to precipitate apomorphine, cinchona, strychnine, nicotine, cocaine, aconite, pilocarpine, lead, silver, aluminium, cobalt, copper, mercury, nickel and zinc.
(8) Alkalis neutralise acids by direct chemical process. It is safer to give little weak solution of an alkaline hydroxide, magnesia or ammonia. Bicarbonate should not be given, because of the possible risk of rupturing the stomach due to liberated C02.
(9) Acids neutralise alkalis by direct chemical process. Only those substances which are by themselves harmless should
be given, e.g. vinegar, lemon juice, canned fruit juice. Neutralisation of acids with alkali and vice versa should be avoided because exothermic reaction or neutralisation can cause additional injury.
The term is usually used to describe those agents that exercise their action on complex of certain metals. They act on the absorbed metallic poisons. They form chelate with the metallic poisons that are freely and help their early excretion from the body. Some of important are described below:
- B.A.L. (British anti-lewisite; dimercaprol; dimercaptopropanol): It is used as a physiological antidote in arsenic, lead, bismuth, copper, mercury, gold, thallium and antimony. Many heavy metals have great affinity for sulphydryl (SH) radicles and combine with them in tissues and relieve the body of the use of respiratory enzymes. Dimercaprol has two unsaturated sulphydryl groups which combine with the metal, and thus stop union of arsenic with the SH group of the enzyme system. The compound formed by the heavy metal and dimercaprol is comparatively stable, which is carried into the tissue fluids, particularly plasma, and is excreted in the urine. In severe poisoning a dose of 3 to 4 mglkg is given. It shouldn’t be used when liver is injured.
(B) E.D.T.A. (ethylenediarninetetraacetic acid: calcium disodium versenate; edathernil; edetic acid; versene): It is a chelating agent and is effective in lead, mercury, copper, cobalt, cadmium, iron and nickel poisoning. The usual dose is 25 to 35 mg/kg.. It forms chelates with lead which are water-soluble, non-toxic, non-ionised, and non-metabolised and excreted intact in the urine.
(C) Penicillamine (cuprirnine; dimethyl cystine): It is a hydrolysis product of penicillin. It has a stable SH group. It is given during a dose of 30 mg/kg. body weight up to a total of 2 g. per day in 4 divided doses orally for about 7 days. It is the chelating agent of maximum efficiency for copper, lead and mercury.
(D) DMSA, succimer (Meso-2, 3-dimercaptosuccinic acid): It is used in lead, mercury and arsenic poisoning. It is better than EDTA in the treatment of lead poisoning, as it does not lead to accumulation of lead to the brain. It is given in a dose of 10 mglkg orally every 8 hours for 5 days, followed by the same dose every 12 hours for 14 days. A combination of succimer and EDTA is said to be more effective. DMSA and DMPS possess the same dithiol (sulphydryl) chelating grouping as dimercaprol and the molecules are more hydrophilic. They have a better therapeutic index.
(E) DMPS: (2,3-dirnercaptopropane !-sulfonate) is effective in the treatment of mercury, lead and arsenic poisoning. It is given during a dose of 5 mg/kg.
Symptomatic treatment :It refers to the adoption of general measures to support the lifetime of the patient and to reduce suffering.
Follow up: adequate follow-up is important to treat the complications if any. In suicidal cases, psychiatric treatment is important.
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