2016 WINTER: Cabin Fever | Toxic World | Activated Charcoal | Gorilla Glue | Marijuana | Chocolate | Catheter Size
Cabin Fever 2016
Escape the winter blues and join us for a full day of CE and fun.
|January 31, 2016|
The Meadows Club
2950 W Golf Road
Rolling Meadows IL 60008
Registration is free, but a $20 donation for Frankie’s Friends charitable pet foundation would be greatly appreciated.
Click here to register: REGISTER
Click here for Agenda: AGENDA
Brought to you by our sponsors:
AVMA PLIT, CareCredit, Elanco, IDEXX, Metro Animal Service, Patterson, Purina, Stokes Pharmacy, Trupanion, Zoetis
It’s a Toxic World
It’s a toxic world if you think about it. And it is our job as veterinarians to look at the world that way. Not everything is toxic, you insist. How about the air that we breathe or the tap water we drink? Well I hate to break it to you, but have you ever heard of oxygen toxicity or water toxicity? Even the most common mundane chemicals in our environment, if taken in concentrations or quantities our bodies or those of our patients can’t handle, can be toxic.
Lucky for us, our pets, living in secure homes, are not exposed to as many toxins, or not in the concentrations required to cause illness. But toxicity is a relative thing. It’s not just about how much of the particular chemical that the pet was exposed to. It’s also about the means of exposure, the rate of exposure, and the ability of the patient to metabolize and excrete the chemical. Toxicology is really pharmacology. Even the medications we prescribe to our patients have the potential to be toxic if the pet can’t metabolize the chemical adequately. See what happens when you give a normal dose of ivermectin to an Australian shepherd with a MDR1 gene mutation or a NSAID to a dog with kidney failure. Lucky for us, the toxic potential and properties of a tremendous number of environmental and household chemicals have been studied and documented. Our own drug formularies are filled with listings of the toxic effects of the medications we use. We don’t need to figure out if a chemical is toxic. The challenge for us is recognizing when an ill patient is demonstrating a toxicity.
Trupanion’s list of top poison and toxicity claims in 2015
- Rat poison
- Common household drugs
- Grapes and raisins
- Onions and garlic
Charcoal: Not Just for the Barbecue
Activated charcoal is a mainstay of toxin therapy. Its properties can bind ingested chemicals and toxins within the lumen of the gastrointestinal tract before they have had a chance to be absorbed into the bloodstream.
What is activated charcoal?
Very similar to the charcoal you might use for grilling, activated charcoal is further processed. Wood and plant materials combined with other sources of carbon, such as coal and petroleum, are heated in the absence of oxygen to form charcoal. To activate the charcoal for medical use, it is heated to incredibly high temperatures and washed in an inorganic acid solution. The resultant product is extremely porous and has varying surface contours. This large surface area, as well as the varying molecular properties within the charcoal, enhances the capacity of the charcoal to bind chemicals and toxins. One gram of activated charcoal can have a surface area of 2000 square meters.
Activated charcoal comes in a variety of formulations: powders, granules, tablets, capsules and suspensions. The suspensions have proven to be most effective in small animal patients.
How does it work?
Activated charcoal will weakly bind ingested chemical compounds to its surface via a variety of chemical attractions (ion-ion hydrogen bonding, dipole and van der Waals forces) between the chemical and the charcoal components. This binding is reversible.
Not all chemicals and toxins have a chemical attraction to activated charcoal. Those toxins having a larger molecular size and lipophilic non-polar properties are better adsorbed than smaller water-soluble compounds. This includes organophosphates, carbamates, chlorinated hydrocarbons, inorganic and organic arsenical and mercurial compounds, and polycyclic organic pesticides. Toxins such as xylitol, alcohols, glycols and strong acids/bases are poorly bound by activated charcoal.
Why is activated charcoal combined with cathartics?
Activated charcoal can actually slow the speed of luminal contents through the GI tract. Consequently, cathartics such as sorbitol may be added to the product to speed the transit of the charcoal and its bound toxins through the GI tract. The sorbitol is converted to fructosamine, which acts to osmotically draw fluid into the lumen of the GI tract. Because repeated dosing with a sorbitol-containing product can lead to dehydration, use of a sorbitol-containing product should be limited to the first dosing only if multiple dosings are to be administered.
What about adding food to the activated charcoal to increase its palatability?
A recent study demonstrated that the addition of food (up to 15 g of food per 1 g of activated charcoal) decreased the adsorptive capacity of the activated charcoal for the drug acetaminophen but that this decrease was probably not clinically significant (<2%).
What could go wrong?
Activated charcoal is not absorbed into the general circulation so it does not pose a systemic risk. However, activated charcoal has poor palatability and must be force fed or administered by stomach tube to most patients. Inadvertent administration or aspiration of the suspension into the patient’s lungs is a potential risk. The administration of excessive volumes, especially in smaller patients, can cause severe electrolyte imbalances (hypernatremia). Excessive body fluid loss from the use of activated charcoal products containing a cathartic such as sorbitol can lead to dehydration. In addition, make certain to warn pet owners that the charcoal leaves a black stain on carpets, fabrics, and other surfaces. Also, inform the owners that charcoal can alter the consistency and color of their pet’s feces.
- A poison control center should be consulted for specific recommendations on the potential efficacy of activated charcoal for the specific toxin that has been ingested and whether dosing should be repeated.
- The recommended oral dose is 1 to 5g/kg.
- Activated charcoal should be administered as soon as possible after ingestion of the toxin before it has had the chance to be absorbed into the blood stream.
- Some chemicals (caffeine, theobromine, bromethalin, pyrethrins, organophosphate insecticides, ivermectin) undergo enterohepatic circulation, i.e. after being cleared from systemic circulation by the liver these chemicals are released back into the GI tract in the bile only to be absorbed into the systemic circulation again. Re-dosing of the activated charcoal may be warranted in these patients to bind toxins released back into the GI tract after the initial activated charcoal dose has already been cleared.
- Activated charcoal should be administered to asymptomatic patients, and preferably adequately hydrated patients, in order to reduce the risk of secondary complications (i.e. aspiration, severe hypernatremia).
A Sticky Situation
Kids aren’t the only ones who like the taste of paste. Some dogs like it, too. One of the oddest conditions that we run into, from a clinician’s perspective, results from the ingestion of either Gorilla Glue® or Elmer’s® Glue-All Max. Both glues contain an ingredient, diphenylmethane diisocyanate, which aggressively foams when it is exposed to moisture in the stomach. The foam expands rapidly, filling the stomach lumen and engulfing other gastric contents. The glue subsequently hardens into the perfect replica of the internal gastric lumen causing an obstruction. The process is believed to take only minutes to complete. It is not known how much glue must be ingested for an obstruction to occur.
Most dogs who have ingested one of these glues present with abdominal discomfort and retching from the obstruction. Radiographs demonstrate a full stomach containing contents of mixed contrast. Surgery is required to remove the foreign body. Mild abrasion and ulceration of the gastric mucosa may be seen. In most cases the glue can be easily peeled off the lumen mucosa.
Should you be presented with a dog, known to have eaten one of these glues, it is recommended that vomiting not be induced. Our concern is that the glue will solidify in the esophagus where it would be much more difficult to remove. Better to let it harden and then surgically remove it from the stomach.
A Growing Toxicity
Marijuana is believed to be the most commonly used illicit drug in the United States. With its legalization for medical use in humans and its recent decriminalization in Colorado and Washington, the frequency with which pets are being exposed to marijuana or one of its derivatives is increasing.
The toxic chemical in marijuana is delta 9-tetrahydrocannabinol or THC. Dried leaves and flowers of the hemp plant Cannabis sativa contain 1-8% THC. Hashish, compressed resin produced from the flowering tops of the plants, contains 10% THC. Hash oil or butter, a concentrated form of hashish or marijuana in which the cannabinoids are extracted into the fat of oil or butter, can have a THC concentration exceeding 50%.
The most common means by which dogs and, uncommonly, cats are exposed to marijuana is by ingestion of home cooked or commercial products containing THC. THC is stored in the tissues of the brain, liver and kidneys. Being highly lipid soluble the chemical is also stored in fat deposits where it can remain for days. The majority of the THC is excreted via the biliary system and eliminated via the feces.
Signs of marijuana intoxication typically occur within 60 minutes of exposure and can last several days. The THC binds to cannabinoid receptors in the brain where it interacts with the neurotransmitters norepinephrine, dopamine, serotonin and gamma-aminobutyric acid inducing varying stimulatory and inhibitory signs involving the GI, cardiovascular and neurologic systems.
Signs of marijuana intoxication
- Depression or dysphoria
- Hyperstartle response
- Urine dribbling
Is it marijuana?
The challenge in diagnosing marijuana toxicity is getting the pet owner to confirm the pet’s potential exposure. Routine blood testing and imaging typically fail to demonstrate significant abnormalities. Furthermore, over-the-counter drug tests as well as laboratory tests for THC have not yet been proven effective in pets. Luckily the signs of THC toxicity, i.e. dysphoria, drowsiness, a hyperstartle response and especially urine dribbling are pretty recognizable.
What’s the best treatment?
Treatment after immediate exposure to marijuana could include induction of emesis and the administration of activated charcoal. Both would be contraindicated if the clinician feels the patient’s mental state predisposes the pet to the possibility of aspiration pneumonia. Interestingly, induction of emesis may not be effective as one of the marijuana’s medical uses is to inhibit nausea and vomiting in human cancer patients. The repeat administration of activated charcoal 6-8 hours after an initial administration should be considered to reduce GI absorption of the THC as it goes through eneterohepatic circulation.
Symptomatic supportive care should be individualized to the patient and would typically include IV fluids to ensure hydration and perfusion, external heating or cooling as indicated, and anti-anxiety therapy. More severely affected patients may require cardiovascular medications, oxygen supplementation or even ventilation. Intralipid therapy should be considered in more severely affected patients and those with prolonged duration of signs. Because THC is lipid soluble, it can be leached from the body with intralipid therapy. Close monitoring of these patients is important. Luckily THC has a high safety margin. To be lethal most dogs must be exposed to greater than 3 g/kg.
Could marijuana be beneficial for treating ill pets?
In humans, marijuana and its derivatives have been shown or suggested to have many potential medical uses including
- Stimulating appetite and reducing nausea in cancer patients
- Treatment of glaucoma
- Increasing lung capacity
- Controlling epilepsy
- Reducing cancer spread
- Slowing the progression of Alzheimer’s disease
- Reducing the pain of multiple sclerosis
- Relieving arthritis discomfort
- Treating inflammatory bowel disease
Reports of marijuana’s effectiveness for treating ill pets are very limited and at best anecdotal. Marijuana is a Schedule I narcotic. Even if you live in a state where medical marijuana is sanctioned, as a veterinarian it remains illegal for you to prescribe or recommend it to treat a patient.
If you feel you may be dealing with a pet who has a potential toxicity or desire closer 24 hours or after-hours monitoring of your patient, please don’t hesitate to give us a call. Our emergency and critical care services have experience dealing with all types of toxicities.
Chocolate toxicity is one of the most commonly encountered poisonings in dogs. Chocolate is readily available, particularly during the holidays, and dogs (much like people) tend to find it irresistible.
Gastrointestinal, cardiac and neurological symptoms predominate. Mild symptoms include vomiting, restlessness, hyperactivity and polyuria. Moderate symptoms include tachycardia, arrhythmias, weakness, ataxia, diarrhea and muscle tremors. With severe intoxications, seizures and coma are possible. Hyperthermia, hypertension and hypokalemia can also develop. Pancreatitis is a possible sequela due to the high fat content in chocolate. The highest concentration of theobromine is found in cocoa, dark chocolate and baking chocolate, and the lowest in white and milk chocolates. As little as ¼ cups of semi-sweet chocolate chips is toxic to a 10 kg dog.
Mechanism of toxicity
Theobromine and caffeine belong to the methylated xanthine alkaloid family (methylxanthines), and they are the primary toxic principles in chocolate. Excessive ingestion of chocolate-containing products results in stimulation of the central nervous system, heart and skeletal muscle and causes smooth muscle relaxation. Methylxanthines inhibit the breakdown of cyclic AMP and antagonize adenosine receptors, resulting in alterations to neurotransmitter and hormone-mediated actions. The consequences include excessive stimulation of the cerebral cortex and myocardium (theobromine), and medulla, respiratory center and skeletal muscles (caffeine). These toxins also cause diuresis and increase the release of catecholamines, particularly norepinephrine. The half-life of elimination of theobromine (at 17.5 hours) is long in the dog, so symptoms can be prolonged.
Theobromine and caffeine content in chocolate products (mg/oz)
Note: 1 oz = 28.4 grams
|Type of Chocolate||Theobromine mgs/ounce||Caffeine mgs/ounce|
|Cocoa bean mulch||56-900||unknown|
|Mild signs (vomiting, hyperactivity||20 mg/kg theobromine|
|Cardio-toxicity||40 mg/kg theobromine|
|Seizures||60 mg/kg theobromine|
|LD50 theobromine||250-500mg/kg(dogs); 200 mg/kg (cats) theobromine|
|LD50 caffeine||140-150 mg/kg (dogs), 100-150 mg/kg (cats) theobromine|
- Induce vomiting, if vomiting has not yet occurred, with apomorphine 0.04 mg/kg IV/IM/subconjunctival (or 3% hydrogen peroxide 1 ml/lb if apomorphine is not available).
- Give activated charcoal (1-3 g/kg), repeated every 4-6 hours for a total of 2-3 doses due to enterohepatic recirculation. The first dose can contain sorbitol.
- Both ventricular and/or supraventricular tachycardia can occur. Ventricular tachycardia should initially be managed with lidocaine; however, a beta blocker is the drug of choice to treat supraventricular tachycardia. Although much of the literature supports the use of propranolol, there have been reports that it may delay renal excretion of methylxanthines; therefore, metoprolol succinate or tartrate are additional beta blocker blockade options.
- Hospitalize for monitoring, IV fluids, encourage frequent urination.
Note: Inducing emesis and oral administration of activated charcoal is contraindicated if the patient is mentally dull, unconscious, or having seizures, due to the risk of aspiration. Gastric lavage is recommended in these patients.
At BluePearl Veterinary Partners, our critical care service can provide emergency and around-the-clock intensive care of pets with chocolate toxicity. Therapy and monitoring can include gastrointestinal decontamination, gastric lavage, IV fluid therapy, continuous ECG monitoring, treatment of severe tachyarrhythmias, and seizure management. As methylxanthines can be reabsorbed across the bladder wall, for severe intoxications, urinary catheter placement can also be performed.
For support of the pet with chocolate toxicity or other poisonings, please contact our critical care service.
Gauging Your Catheter Size
It’s rare that a day goes by that we don’t place an IV catheter in one of our patients. But what size catheter is correct? Unfortunately, no clear guidelines exist in the veterinary or human medical fields when it comes to choosing what gauge and length of catheter to place.
Before picking a catheter size, consider Poiseuille’s law, which states
|Flow =||π(radius)4(pressure drop)|
In general terms, it states that the narrower the lumen or the longer the tube, the greater the resistance to fluid flow. A short, wider diameter catheter will have much greater flow than a long narrow one. In addition, the greater the viscosity of the fluid, the slower the fluid will flow.
Taking this law into consideration, if the desire is to be able to administer large volumes of fluids quickly or to administer more viscous fluids such as plasma, blood or parenteral nutrition, a shorter wider diameter catheter is preferred. Patients presenting in shock, at risk for requiring rapid fluid resuscitation or undergoing surgical procedures would therefore benefit from a lower gauge, i.e. larger diameter catheter, to facilitate rapid or viscous fluid flow. In addition, larger diameter catheters are less likely to kink or become plugged by a blood clot and are less likely to induce hemolysis or thrombosis when used for blood transfusions. A disadvantage to larger diameter catheters is the discomfort that occurs both during catheter placement and while the catheter is in place.
The size and fragility of the vein to be catheterized are also important factors when it comes to choosing a catheter gauge. It is obviously easier to place a narrower (higher gauge) catheter in the smaller veins found more peripherally in the body and in small patients. In addition, if the catheter is too large you risk directly damaging the vein from the catheter rubbing on the vessel walls. Fragile vessels, such as those found in patients with vasculitidies (think kidney failure or immune conditions) are also susceptible to injury from larger diameter catheters. A disadvantage to narrow lumen catheters is their tendency to kink and to become plugged.
How about the length of the catheter?
A distinct advantage to longer catheters is that they are less likely to become dislodged. This would be important in active patients where excessive movement of the catheter site is a concern or if administering medications that irritate surrounding tissues when leaked out of the vessel. The primary disadvantage to longer catheters is the additional resistance to fluid flow. This applies to even those catheters placed in larger central veins. It’s not the size of the vessel that affects the rate of potential fluid flow but the length of the catheter.
So before choosing a catheter gauge and length, consider the purpose and potential need of the catheter, the condition and size of the vessel to be catheterized, the status of the patient (underlying illness, activity level, potential complications), the medications and fluid types to be administered, and the fluid flow rates that might be required.
- Smaller diameter (higher gauge: 24 ga/22 ga) catheters are probably best reserved for patients who have very small or fragile veins or require short-term fluid or IV medical treatments.
- Medium diameter (20 ga/18 ga) catheters are useful in medium-sized to larger patients with healthy veins who may require moderate fluid rates or blood transfusions.
- Larger patients and those who may require rapid or high volume resuscitative fluid loads or viscous fluids (lipids/parenteral nutrition) would benefit from the largest catheter diameters (18 ga/16 ga).
Longer catheters are preferred if a prolonged duration of catheter use is expected, there is excessive mobility at the site which could dislodge the catheter, or to ensure the medication and/or fluids being administered is done so safely into the vessel lumen.
Note: Studies suggest that the length of the catheter probably has no effect on the risk of developing thrombophlebitis in the vein. The composition of the catheter, such as silicone or polyurethane, and the character of the fluid being infused (caustic medications and those with low pH or high viscosity) are more likely to play a role.
We are pleased to welcome Megan Kaplan, DVM, DACVECC, to our emergency and critical care services team in Northfield. With the addition of Dr. Kaplan, we will have critical care coverage seven days a week. And, David Wilson, DVM, DACVS-SA, is now seeing surgery appointments in Skokie on Thursdays. He will continue to see patients in Northfield Tuesday, Wednesday, Friday and Saturday.