2016 SPRING: Xylitol | GDV | Wound Management | Catheter Size | Component Blood Therapy | Hip Dysplasia | Continuing Education
Xylitol: A Not-So-Sweet Sweetener
Xylitol appears to be everywhere these days. It has become popular as a sugar substitute for human consumption. You can find it in chewing gum, baking products, sugar free candy and weight loss food items. The reason for xylitol’s popularity is that it is just as sweet as sucrose but lacks sucrose’s caloric content and insulin stimulating effects. Xylitol is naturally found in the fibers of many fruits and vegetables. It is presently produced for mass consumption by hydrogenation of xylose, which has been extracted from wood and corn sources.
Xylitol first became popular in the 1800s when it was determined it could be used as a sweetener for people with diabetes mellitus. More recently xylitol has been shown to have significant dental benefits.
Studies have shown xylitol to inhibit Streptococcus bacteria proliferation in the mouth thereby slowing plaque formation and tooth decay. By alkalinizing the saliva, xylitol also potentiates the deposition of calcium and phosphate salts into dental enamel. It has consequently been gaining use in such products as toothpaste, chewing gum and mouthwashes. Other studies have suggested that xylitol may be useful for inhibiting osteoporosis and the development of infections. In one study, cats who drank water supplemented with xylitol demonstrated reduced dental plaque and calculus formation.
Xylitol does not appear to be toxic to humans or cats. This is not the case in dogs where it appears to excessively stimulate insulin release. Severe hypoglycemia can develop as early as 30 minutes after ingestion or as late as 12 hours later, potentially leading to depression and seizures. The exact toxic dose for dogs has not been determined. Clinical signs of hypoglycemia have been reported in dogs ingesting >0.1 g/kg.
Recent reports also indicate that xylitol can cause liver necrosis in dogs. Hypoglycemia is not a prerequisite for liver damage to occur. Signs of liver failure could include loss of appetite, bleeding and gastrointestinal upset. Most dogs will demonstrate signs within 72 hours of xylitol ingestion. The toxic dose for potential liver failure has been reported to be >0.5 g/kg. The mechanism for liver necrosis remains undetermined.
The immediate treatment for xylitol ingestion, similar to other toxicities, should include the induction of emesis followed by the administration of activated charcoal. Unfortunately xylitol is absorbed very rapidly after ingestion.
- The ingestion of a subtoxic dose of xylitol warrants observation and monitoring of the dog for 24 hours.
- If a toxic dose of 0.1 – 0.5 g/kg is ingested, in-hospital observation and monitoring of glucose and liver values should be performed. In patients with significant hypoglycemia, intravenous fluids supplemented with glucose should be administered until normal glucose concentrations can be maintained without supplementation.
- For a toxic dose > 0.5 g/kg, at least 72 hours of intravenous fluid therapy, frequent monitoring of glucose and liver values, and the prophylactic administration of hepatoprotectants such as s-adenosylmethionine and N-acetylcysteine are suggested.
When in doubt about the quantity of xylitol ingested, aggressive treatment should be considered as a precaution. Additional treatments will depend on the patient’s clinical signs and lab results. Prolonged treatments will be required in patients with significant liver damage. The prognosis would be at best guarded in these patients.
Gastric Dilatation Volvulus
People often think that restricting exercise before or after eating, restricting water intake before and/or after feeding a meal, feeding two or more meals daily, or moistening dry kibble before feeding increases the risk of gastric dilatation volvulus (GDV) in large breed dogs. Contrary to popular belief, these activities do not increase the risk of GDV, also referred to as stomach bloat.
Factors that have been shown to increase the risk for GDV include raising the food dish (more than doubles the risk), fast eaters, age (20% increased risk per year of life), high stress dogs, and familial history. A first generation relative with bloat, such as a parent, sibling or offspring increases the dog’s risk by 63%.
In general, any large or giant breed dog has a 24% risk of developing GDV during their life. Overall, 42.4% of all great Danes will bloat during their lifetime. Other breeds also at high risk include German shepherds, standard poodles, Weimaraners, Saint Bernards, Gordon setters, Irish setters, and Rottweilers. Both males and females have the same risk of bloating, and the age at which bloat occurs ranges from 10 months to 14 years. Each year in the United States at least 60,000 dogs suffer from GDV.
Traditionally, most pet owners do not elect to have a prophylactic gastropexy performed. Rather, they wait until life-threatening GDV has occurred. Although the success rate of medical resuscitation and interventional surgery is about 90% with early treatment, some pet owners fail to find their bloated companion early, which results in high mortality risk. In addition, the cost for treatment once the pet has bloated can more than triple the cost of a prophylactic surgery. Open prophylactic gastropexy is an excellent modality to prevent life-threatening bloat; however, many pet owners will decline this procedure, as it is perceived as being highly invasive.
Laparoscopic gastropexy requires only a few small incisions for insertion of an operating laparoscope and forceps. Advantages of laparoscopic gastropexy include much less surgical trauma to the patient, shorter surgical and anesthesia times, and less pain to the patient than traditional surgery. The gastropexy performed laparoscopically has proven, in nearly all cases, to be strong enough to last the entire lifetime of the patient.
Wound Management: How Does Your Garden Grow?
In recent years, there has been a movement toward organic gardening without the use of harsh synthetic chemicals and pesticides. While there is no definitive evidence that organic is better for you or that it produces tastier food, most of us believe we will be healthier without subjecting our bodies to harmful substances.
Consider application of this concept to wound management. Treat your patient’s wound ‘organically’ by replacing harsh chemicals with treatments that tissues need and benefit from, and you are likely to be rewarded.
Maintaining a moist wound environment during healing must be the rule and is achieved with occlusive or semi-occlusive dressings. As plants need moisture, so too do all wounds and in all phases of healing. With loss of skin, wounds will desiccate quickly without a replacement barrier. Wounds kept in a moist wound environment have been proven to heal faster and have a lower infection rate. This occurs because a moist wound with a protective barrier achieves the following, to name a few benefits:
- Creates barrier to exogenous bacteria;
- Concentrates wound fluids in the bed containing growth factors & antibiotics;
- Lowers oxygen tension and pH slowing bacterial growth & favoring angiogenesis and collagen synthesis; and
- Enhances white blood cell activity and their enzymes.
A common misconception is that wet-to-dry bandages provide a moist wound environment, which they do not. These are not moisture-retentive dressings because they do not retain the wound’s own fluid in the bed. This type of dressing functions as a means of debridement and should be reserved for those wounds that cannot be surgically debrided early on. Wet-to-dry bandages pull the wound fluid out of the bed and into the dressing, initially macerating tissues with exogenous moisture then desiccating the tissue as the bandage dries out.
Wet-to-dry bandages have these disadvantages:
- Damage healthy tissues (as evidenced when you wear a wet Band-Aid® for several days);
- Are painful to wear and remove;
- Will delay the start of the repair phase of healing; and
- Are likely to rip out any healing tissue that may have managed to grow.
Not an organic approach, if a wet-to-dry is necessary, limit it to the first day or two or until surgical debridement can be achieved.
There are a number of moisture-retentive dressings available and choosing the correct one can be a daunting task. In a nutshell, each dressing has a varied ability to absorb wound fluid, retain moisture and even donate moisture. The amount of wound fluid production will dictate your choice, and your goal should be to maintain a moist wound but not wet enough to macerate the tissues.
The inflammatory, or debridement, phase begins the process of wound healing and is the phase in which we have the greatest influence in speeding things along. With surgical or biologic (maggot) debridement, we shorten the job for the inflammatory cells. Prevention of infection during this phase is important, so systemic antibiotics are essential during early management.
The use of topical antibiotics or antiseptics in most studies have not proven to lower the incidence of infection to any significant degree. In addition, most topical agents have been shown to impede various phases of wound healing.
In our search for an organic approach, it has been shown that sugar and Mānuka honey are topical agents that have good antimicrobial activity and may actually enhance healing. Not a high-tech approach; these agents were used prior to the advent of penicillin, but apparently there is some good chemistry behind the scenes.
Both of these agents have strong interactions with water molecules, pulling edema fluid out of the wound. The lack of ‘free’ water inhibits the growth of microorganisms. In addition, when honey or sugar is diluted by wound exudates, hydrogen peroxide is produced via a glucose oxidase enzyme reaction. This is released slowly to provide antibacterial activity but does not damage tissue like our topical chemical does.
It has also been found that honey has high levels of an antibacterial phytochemical termed “unique Mānuka factor” and is effective against over 250 strains of bacteria including resistant strains such as MRSA. This substance is yet unidentified but the thicker and darker the honey, the more of the substance is present and the more potent the antibacterial properties. The more potent the Mānuka, the more expensive, as well, and there is actually a rating system for the potency.
If you still have a difficult time with the concept of putting food into wounds, consider silver sulfadiazene. This topical antibiotic ointment may not have healing properties like honey but has a good spectrum of activity and has fewer negative effects on the healing process when compared to other topical antibiotics.
Once debridement is sufficient, inflammatory cells release cytokines and chemical mediators that signal angiogenesis, collagen deposition and epithelialization, marking the start of the proliferative phase and deposition of granulation tissue. The granulation tissue is the stroma over which the epithelial cells will migrate. Antibiotics are not necessary at this point. The high vascularity of a healthy granulation bed makes it very resistant to infection. It is essential again to maintain a moist wound environment, making it easier for the bed to contract and for epithelial cells to migrate across the wound. Gentle tissue handling and bandage changes only frequent enough to prevent maceration will suffice.
There are many approaches to managing a wound and probably many strong opinions as well on which approach is best. Although science has brought us a long way from the days of pouring boiling wine into a wound and cauterizing with a hot blade, science may also have moved us toward harsher chemical treatment in our struggle against infection and, most often, this is not necessary.
One of the first principles taught to students is gentle tissue handling. This should be an even more important principle to apply to the management of vulnerable wounds and, in my humble opinion, will lead to greater success.
We would like to thank our colleague from BluePearl in Florida, Helga Bleyaert, VMD, DACVS, for allowing us to use this article for Companion.
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.
Maximizing the Return: Component Blood Therapy
When a patient needs a blood product, it is not always easy to come by, nor is it inexpensive. Therefore, the judicious use of blood products is warranted.
Rarely does the patient need all the components present in whole blood. Separation of blood into its cellular and plasma components not only allows for more efficient replacement of the patient’s need, it reduces the likelihood of transfusion reactions resulting from unnecessary cellular or plasma protein administration. In addition, noncellular blood components can be stored for prolonged periods for later use.
By separating blood into its components, a single unit of blood can be used to treat numerous patients depending on their needs. Other than whole blood, which is used primarily to replace excessive blood loss, the most common components used in primary care practice are packed red blood cells, fresh frozen plasma, frozen plasma and cryoprecipitates.
Dogs with IMHA can benefit from pRBC transfusions.
Post-centrifugation, plasma has been separated from the red blood cells
Blood can be separated into numerous components.
Centrifugation is required to separate blood into components.
Centrifugation and refrigeration/freezing techniques are used to separate and store blood. Closed-bag blood collection systems make the process sterile and fairly easy, with the right equipment.
What are the most common uses of specific blood products?
Whole blood: Indications for whole blood use include excessive blood loss secondary to trauma, internal hemorrhage and clotting disorders. The goal in these patients is to replace the cellular components, fluid volume, plasma proteins and clotting proteins at the same time.
Packed red blood cells: For patients suffering from hemolytic anemia, packed red blood cells have the advantage of providing concentrated red blood cells without the risk of volume overload or reactions to the plasma component.
Fresh frozen plasma: Viable for 12 months, fresh frozen plasma is indicated in patients needing fluid volume expansion and/or coagulation proteins to treat clotting disorders associated with DIC or rodenticide ingestion.
Frozen plasma: Viable for up to 5 years, frozen plasma contains albumin and a few of the more stable coagulation proteins. It is used in patients needing fluid volume expansion.
Cryoprecipitate: Indicated for use in patients with von Willebrand’s disease and hemophilia due to factor VIII deficiency, cryoprecipitate is produced by the partial thawing and then refreezing of fresh frozen plasma.
Hip dysplasia is a complex disease with both genetic and environmental factors that affect expression in our patients. The actual incidence of canine hip dysplasia (CHD) is unknown, but the frequency of disease is much higher in our large and giant breed populations, with the exception of our sighthounds such as the greyhounds and Borzois. Male and female dogs are affected with equal frequency, which differs from the disease in humans where 80% of people affected are female. Puppies that are genetically predisposed to hip dysplasia, unlike humans, are normal at birth. Though the true cause of hip dysplasia is still unclear, stretching of the joint capsule and ligament of the femoral head is observed as early as two weeks of age. Joint effusion and progressive stretching of these structures are associated with increasing joint laxity. This allows the femoral head to subluxate when bearing weight and changes the forces acting on the plastic, immature skeleton. These abnormal forces lead to degenerative changes and bone remodeling. The rate and degree of disease progression vary with the individual. Direct cause and effect between instability and osteoarthritis has not been established. While dogs affected with osteoarthritis due to hip dysplasia show laxity, not all dogs that show laxity develop osteoarthritis.
Patients may initially present between 5-12 months of age with an acute unilateral or bilateral lameness; however, signs may be more subtle such as “bunny hopping,” difficulty rising, reluctance to run, jump, play or use the stairs. Owners may also present their pet at varying stages of chronic disease.
Observation and physical examination such as pain on hip manipulation and evidence of hip laxity “Ortolani sign” can arouse suspicion of hip dysplasia. However, the diagnosis is established by radiographic examination of the dog while under general anesthesia, or deep sedation, to ensure proper positioning. Currently Penn Hip radiographic evaluation offers the most objective evaluation of hip laxity particularly when compared to the OFA technique.
Dogs that have joint instability with minimal or no radiographic evidence of osteoarthrosis are usually immature or young adult animals. These dogs may not show any signs of hip pain, or they may exhibit a sudden onset of unilateral or bilateral hind limb lameness. In many cases, surgical treatment is the best option. Options for surgical treatment that we recommend are a triple pelvic osteotomy for patients with subluxated hips and otherwise good joint confirmation. In patients with degenerative changes, the recommended surgical procedure would be a total hip replacement or in some cases femoral head and neck excision if finances are an issue. Although conservative management may be effective in dysplastic dogs with mild to moderate osteoarthritis, the degree of coxofemoral incongruence and severity of osteoarthritis changes in some dogs may preclude alleviation of pain by conservative means. Conservative management consists of the administration of analgesics and/or chondro-protective agents, weight reduction and controlled exercise. As with many other musculoskeletal abnormalities, surgical intervention often carries the best results when performed earlier in the course of disease; however, total hip replacement may be the best option for patients with end-stage disease.
If you have questions about a patient case regarding hip dysplasia please call and speak to a member of our surgery team to discuss possible medical treatments.
CE Calendar of Events
BluePearl is strongly committed to the veterinary community. One of the ways we demonstrate this commitment is through our continuing education program, which is subsidized in part by our Partners in Education.
All BluePearl CE lectures are free and open to all area veterinary professionals. Registration is required, please; space is limited. Dinner will be provided. To register, please email Jackie Todd at email@example.com. For the most current information about BluePearl CE, please check our online calendar regularly for the latest information.
|Apr 14||7PM||Doctor/ Tech||A Clear Look at Glaucoma|
Nicole Scotty Trumble, DVM, DAVCO
|Broadway Pizza Blaine Conference||1 hr|
|May 4||7PM||Doctor/ Tech||Gallbladder Treatment|
Alyssa Mourning, DVM, DAVCIM
Heather Hadley, DVM, DAVCS-SA
|Minnetonka Community Center||2 hr|
|May 12||7PM||Doctor/ Tech||Gallbladder Treatment|
Alyssa Mourning, DVM, DAVCIM
Heather Hadley, DVM, DAVCS-SA
|Broadway Pizza Blaine Conference||2 hr|
|May 19||7PM||Tech||How Ready Is Your Operating Room?|
Ann Gaier, BS, CVT, VTS (Surgery)
|AEVS Conference Room||1 hr|
|June 1||7PM||Doctor/ Tech||Canine Joint Disease and Treatment|
Kathryn Kaufman, DVM, DAVCS-SA
|Minnetonka Community Center||1 hr|
|Canine Joint Disease and Treatment|
Kathryn Kaufman, DVM, DAVCS-SA
|Broadway Pizza Blaine Conference||1 hr|
|June 15||7PM||Tech||Into the Bowels of GI Disease|
Emily Chinn, CVT
|Blaine BluePearl Conference||1 hr|