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Poisoning

With the epidemiology of poisoning, there is the young child, the toddlers, generally less than five-years-of-age. Those are typically a single drug. The kids don’t go through the whole medicine cabinet and eat it. They take a single drug. The other age group are those who act like children, who are typically adolescents and these are oftentimes suicide gestures or attempts, oftentimes multiple drugs. So the fact you find one drug ingested in an adolescent does not mean that that’s all there is.

History is very crucial. You need to know the exact substance ingested. I gave you the example of household bleach being relatively benign. Another good example is nail polish remover; in the small bottles, is acetone and is relatively benign. If the substance is nail remover, that is it is designed to remove the glue on nails, it is exceedingly toxic. It has cyanide. So you don’t want to tell a parent whose child has ingested cyanide in the form of nail remover, that it’s a benign ingestion or they are likely to find him dead in the morning. So know what the substance is that you are talking about so that you can in fact give good advice. You want to know exactly what the preparation is. If they are going to be seen either in the office or in an emergency department, have them bring in the substance. You’d like to know what the maximum dosage is. That is, how many pills were originally in the bottle, how many are in there now. Again, bring in the container and you’d like to know what the time of ingestion is. You are going to do something different if the child took it three days ago than if they took it five minutes ago. You are going to want to know about any other possible medicines that they could have ingested, and the best way to do that is to just scoop up all the medicines in the medicine cabinet and have them bring them along with them. You want a significant medical history. You don’t care if they’ve had two episodes of otitis or four episodes of otitis. What you care about is, are they neurologically normal. Do they have any major underlying conditions and are they taking any medications baseline.

So we are going to talk about modes of decontamination. You certainly don’t want someone to continue absorbing the toxin after they reach medical care. Some substances continue to be absorbed through the skin. You want to remove the clothing, irrigate copiously. This is especially important for certain corrosive agents, but also the organo-phosphates, the pesticides. They are actually pretty well absorbed through the skin, so you don’t want absorption to go on. Also, wear gloves when you are doing this.

What are other forms of decontamination? We are going to talk about each of these in turn. Emesis, lavage, activated charcoal, cathartics, whole bowel irrigation and means of enhanced elimination. You would think with all of the poisonings around the country and around the world that there would be good answers to which of these modes are best. In fact, the answers are not as clear cut as you might think. Syrup of ipecac is really the preferred agent to use if you are going to induce emesis. The doses are up there. You don’t really need to give them additional liquid. It’s 90% effective with a single dose. You can repeat the dose, if it’s not effective, in 20 minutes. There is really no evidence that it is superior to charcoal in the agent using it with substances that are absorbed by charcoal. There are some contraindications. If someone took in a caustic agent, the last thing you want to do is have them bring it back up and burn their esophagus going both directions. So certainly, caustics you don’t want to have them bring up. Hydrocarbons in general are benign substances systemically. Their toxicity is with aspirations. So if they didn’t aspirate it going down, don’t help them aspirate it by making them vomit.

Altered level of consciousness. If they are altered at the time that you see them, or they are likely to do so - that is, become altered level of consciousness - do not induce vomiting. The last thing you want to do is give them ipecac, have them become comatose, and then vomit and aspirate. The tricyclics are classic for inducing coma in a short period of time. So certainly for a tricyclic ingestion you would not want to induce emesis. In age of less than six months, the reason is really unclear to me for that contraindication. Likely because at six months old and less, may not protect their airway very well. Again, that’s a relative contraindication.

Lavage; lavage basically refers to washing out the stomach. It may be useful if used early, that is less than an hour. Obviously if the substance has left your stomach, there is no good in lavaging out the stomach. Again, caustics and hydrocarbons are the big indications. If there is decreased level of consciousness and you really feel that they need to be lavaged, they need their airway protected. A lot of the studies with lavages used very small NG tubes. It’s relatively useless with small tubes. You need the largest possible tube placed, which involves going in the mouth rather than the nose. And lavage, a normal saline 15 ml aliquots with the left side down. You don’t want to be washing it transpylorically and being absorbed. Again, really no evidence that lavage is any better than activated charcoal.

I think over the years activated charcoal has been the mainstay of therapy for most ingestions. The doses are 1 gm/kg oftentimes given with the first dose in sorbitol. It comes pre-prepared in many preparations in sorbitol. If you are going to use it on an ongoing basis, don’t use all the doses in sorbitol. You will likely create more problems than you are solving. There are a few things that charcoal does not absorb; alcohol, iron, the caustics, hydrocarbons, lithium and heavy metals. So there is no use given charcoal for these ingestions. Multiple doses may be potentially useful, especially in substances that are picked up and excreted again in the liver. The substances that are best documented for multiple uses of charcoal are the salicylates, Phenobarbital, theophylline and carbamazepine. Even with an IV overdose, you have enough capillary blood flow to your GI tract that you can enhance elimination of substances, even if they are given IV, oftentimes by repeat enteral charcoal. So it’s not just that it prevents initial absorption.

Cathartics; cathartics are things like sorbitol, magnesium sulfate. Very limited evidence that they are of any benefit at all. If you give them in significant doses, you will end up with electrolyte problems. Certainly magnesium sulfate given repeatedly, you can end up with magnesium toxicity. Again, a single dose only for cathartic. There is really no evidence that it’s all that effective, and sorbitol - if you somehow feel compelled to give a cathartic - is your agent of choice.

Now, the ultimate of a cathartic is whole bowel irrigation. This is with isotonic polyethylene glycol. Substances which in my mind are very mis-named with things like GoLYTELY, which patients do anything but go lightly after polyethylene glycol. This is not a few cc. This is a half a liter an hour in little children, and a liter an hour in adolescents. Basically until their rectal effluent is clear. So you are literally washing out their intestines. Patients will tolerate this remarkably well with essentially little or no electrolyte disturbances. It is especially useful for substances that have delayed absorption or time release capsules. Slow release iron where you can see many pills on the abdominal x-ray. You can wash them out. You can actually follow your progress with repeat x-rays. So whole bowel irrigation may be useful for things like that. Body-packers; get somebody smuggling drugs, body-packers. Balloons or condoms filled with drugs. You’d like to get it out before they burst. It may be effective for that. Contraindications; ileus, bowel perforation, and obviously a bowel obstruction.

Now what about enhanced elimination, once it’s been absorbed into your body and you’d like to get rid of it? Forced diuresis, although historically done fairly frequently, is of relatively limited benefit. Maybe for ethylene glycol forced diuresis would be helpful. Otherwise, by itself is not real helpful. Urine alkalinization; the classic drug that urine alkalinization is helpful for is the salicylates. By keeping it in an ionized form you prevent its re-absorption from the tubules and it is excreted. You also maintain the salicylate in an ionized form, such that it doesn’t cross the blood/brain barrier, so you have a lot less neurotoxicity.

Hemodialysis may be very effective in some agents. What you would like is a low volume of distribution of your drug, so that it stays in the blood stream, a relatively low molecular weight such that it passes through the dialysis membrane, and relatively non-protein bound so that it’s actually freely available to be dialyzed. Doing a few of the specific agents I will talk about, the indications for hemodialysis.

Hemoperfusion is of little additional value to hemodialysis and most people would not advocate its use. Immunotherapy has a few specific indications. Certainly the most common is digoxin intoxications. Also rattlesnake envenomations where you can have the antivenom. They may be helpful to use immunotherapy.