2016 FALL: TPLO | Drug Dosing by Body Surface Area | Chemotherapy Safety | Nutritional Support of Ill Patients | ER Word Search
Explaining CCL Injury and TPLO to Your Client
Why is tearing the cranial cruciate ligament a problem?
Injury and tearing of the cranial cruciate ligament (CCL) is one of the most common causes of hind limb lameness, pain and progressive arthritis of the knee (also called the stifle) in dogs. Many ligaments support and stabilize the stifle allowing the bone above (femur) and below (tibia) the knee to bend without sliding forward or backwards against each other.
The surface of the tibia, called the tibial plateau, has a slope. When the dog bears weight, the tibia wants to slide forward on this slope. The CCL restrains this movement.
A knee with healthy ligaments can only flex, extend and minimally rotate. Tearing of the CCL allows the tibia to slide forward when weight is put on the leg causing instability, rubbing, and pain.
(image courtesy of VMSG)
Rupture of the CCL results in instability and abnormal sliding of the tibia forward with every weight-bearing step. Most dogs with this injury cannot walk normally and experience pain. The resulting instability damages the cartilage and surrounding structures and leads to progressive arthritis. Cartilage pads or cushions within the knee called menisci may also become damaged.
What are the signs of a cranial cruciate ligament tear?
Early signs of CCL damage or partial tears include stiffness or very mild lameness affecting one of the back legs, most noticeably after exercise. Dogs may show subtle changes in gait, a tendency to shift weight off the affected leg when standing in place, or the inability to sit straight. As the CCL continues to tear further, symptoms increase.
A full tear usually results in complete lameness in the affected leg. Many dogs refuse to walk on the affected leg and may hold the leg up in the air.
In some cases, the knee will make a clicking or popping sound as the dog walks. This often indicates damage to the cartilage pads (menisci) within the knee.
How is the diagnosis made?
A CCL tear is diagnosed by palpation and radiographs of the knee. Sliding of the tibia forward against the femur with manipulation (called a cranial tibial thrust or cranial drawer sign) indicates that the CCL has torn. Some dogs must be sedated to check for this abnormal motion.
Radiographs in patients with a torn CCL often demonstrate arthritis and joint effusion (swelling). The actual ligament cannot be seen on the radiographs.
How is a CCL tear best treated?
(Figures 1-3 courtesy of DePuy Synthes Vet)
Surgery is required to restore stability and minimize arthritis. A variety of surgical procedures are available. One such procedure is the TPLO (tibial plateau leveling osteotomy). Numerous reports indicate that dogs treated with the TPLO procedure have a better functional outcome and develop arthritis in their knee much more slowly than dogs treated with ‘traditional’ repairs.
To perform a TPLO, the surgeon will first examine the inside of the stifle joint arthroscopically or through a small incision in the joint allowing removal of the torn ends of the CCL. Portions of the menisci will also be removed if damage is found.
Next, the surgeon will make a curved cut through the tibia using a specially designed saw blade (figure 1). The top portion of the tibia is then rotated a precise number of degrees in order to change the angle of, thereby leveling, the slope of the tibial plateau to prevent the forward sliding that occurs with a CCL tear (figure 2). A bone plate and screws are then placed in the tibia to stabilize it and allow healing to occur (figure 3). The incision is closed with sutures or skin staples.
What happens if a CCL tear is not surgically treated?
Abnormal sliding of the bones within the knee will damage the cartilage and surrounding support structures. The initial pain may diminish with time; however, severe arthritis will develop more rapidly. Chronic and persistent discomfort, decreased ability to bend the knee, and loss of strength in the leg will develop. The dog’s willingness to play and exercise will likely diminish due to the loss of leg function and discomfort. Approximately 40% of dogs will tear the contralateral cruciate regardless if repaired or not.
Are there any risks or complications to the TPLO procedure?
Complications are seen in approximately 5% of dogs undergoing TPLO surgery. They are similar to those seen with other types of orthopedic procedures that utilize bone plates and screws. Infection, delayed healing of the bone, and irritation or tearing of other menisci or ligaments in the knee have all been reported. Many of these complications result from too much activity at home during the recovery period. Most of these complications can be treated successfully, allowing the patient to go on to a full recovery; however, occasionally, additional surgery may be needed to solve the problem.
What happens after the surgery?
Swelling and bruising of the surgical site is to be expected after surgery. Many dogs may be reluctant to bear weight on the injured leg for up to a week after surgery. Pain control will be addressed throughout the pet’s stay at the hospital and for the first few weeks of recovery at home.
Proper care of the pet at home is crucial to achieving a successful outcome. Patients must be confined to one level of the house, avoid jumping on or off of furniture, and should not be allowed off leash for at least eight weeks. With time the amount of activity allowed will slowly be increased as the healing progresses.
At two weeks after surgery, most dogs are bearing moderate to complete weight on the affected leg. By 10 weeks the majority of dogs can begin walking and playing normally, with only the most stressful activities restricted. Peak recovery (complete or near complete resolution of lameness, rear limb muscle symmetry, etc.) is generally not achieved until 4-6 months after surgery. All patients that experience a cruciate injury are prone to develop stifle osteoarthritis, but stabilization slows the progression significantly.
Do patients benefit from physical rehabilitation as people do?
Yes, multiple studies have shown that physical therapy speeds recovery and improves final outcome regardless of the chosen surgical technique. Range of motion exercises, controlled leashed walks and time in an underwater treadmill may be suggested.
A good resource for additional information on the TPLO procedure can be found at TPLOanswers.com
We are pleased to offer TPLO surgeries at both Town Center and Greenbrier hospitals. Please feel free to contact Dr. Frank Triveri at Town Center or Dr. Samson Daniel at Greenbrier for consultations regarding this procedure.
Why Dose Drugs by Body Surface Area?
Use of body surface area (BSA) to determine the appropriate drug dose was popularized in the first half of the 20th century. Studies at that time suggested that BSA, better than body weight, reflected physiologic parameters such as blood volume, renal function and basal metabolic rate. Body surface area was subsequently used to determine drug dosages in drug safety trials for which accurate dosing was deemed necessary to achieve the desired effect of the drug while avoiding over-dosage that could lead to toxicity. Based on the belief that BSA is a more accurate method for determining the ideal drug dose, it has come into greatest use in the oncology field where the range between anti-cancer drug efficacy and toxicity is narrow.
Determination of a patient’s true BSA is complicated. Consequently, numerous formulations have been developed to approximate the BSA of the patient, most based on a patient’s body weight and/or height. The calculated BSA will vary with the formula used and is at best an estimate of a patient’s true BSA. Body surface area is typically expressed in square meters (m2).
Recent studies have demonstrated that a drug’s blood concentration is not necessarily reflective of the patient’s BSA or body weight and can vary significantly among individuals. The pharmacokinetics of any particular drug, most notably its rate of metabolism and clearance, can be affected by a patient’s age, sex, cardiac output, renal function, genetics and even environmental factors. Because of the variability in how individuals may metabolize a medication, use of the BSA may be just as likely to underestimate or overestimate the amount of drug required in an individual as would use of body weight.
Which is better: BSA or body weight?
Neither BSA nor body weight are perfect predictors of appropriate medication dosing in an individual. However, right now in the veterinary field, these are all we really have. Individualizing drug dosages based on the drug concentrations that can be achieved in the bloodstream would be a better way to dose our patients.
However, until a means of determining the blood concentration of a particular medication in our patients becomes widely and inexpensively available, we are left with BSA and body weight as starting points. Realizing the limitations in these dosing schemes, individual adjustments in medication dosages may need to be made based on the clinician’s experience with the medication and the clinical response of the patient.
Chemotherapeutic agents kill cancer by directly damaging DNA. These drugs also affect normal tissues, so cancer patients that have survived treatment can have a number of long-term side effects including damage to organs such as the liver, kidneys, lungs, heart and bone marrow; effects on reproduction and the developing fetus; and hearing impairment. Nurses who handle and administer chemotherapy have been shown to have higher indicators of mutagenic substances and chemotherapy metabolites in their urine. It has also been demonstrated that some family members of people on chemotherapy are exposed and have chemotherapy metabolites in their urine. Potential health risks of chemotherapy exposure include
- Acute effects: skin rashes, allergies, hair loss, headaches
- Chronic effects: immune dysfunction, renal and liver dysfunction
- Effects on fertility and reproductive outcomes: infertility, spontaneous abortion, congenital malformations
- Associations with cancer: leukemia, carcinomas (breast, nasal, bladder)
In veterinary medicine we are at a unique and increased risk of exposure to these drugs because the most common practice is for one person to both prepare and administer the drugs. This is different from human medicine where the drug is usually prepared by a pharmacist and administered by a nurse. Another concern in veterinary medicine is the number of women of child-bearing age that are participating in patient care as spontaneous abortion has been a well-documented consequence of chemotherapy exposure. This could happen early in pregnancy prior to a woman knowing she is pregnant. Also with the increased use of oral chemotherapy agents in pets at home, there is a high risk of owners exposing themselves through improper drug or excrement handling.
It is important that PPE is worn to prevent inadvertent exposure to chemotherapy agents during drug preparation or administration.
Several groups have developed guidelines for the proper management of hazardous drugs including chemotherapeutic agents. These recommendations have been in place since the mid-1980s but there have been continued reports of occupational exposure. The National Institute for Occupational Safety and Health (NIOSH) issued an alert and developed guidelines to prevent exposure to hazardous drugs in the occupational setting.
It is important to remember that chemotherapeutic agents are not the only hazardous drugs on the list. The definition of a hazardous drug is any drug that is carcinogenic, teratogenic or genotoxic; causes reproductive toxicity in humans; or can cause organ toxicity at low doses in humans or animals. Other drugs that are listed as hazardous and commonly used in veterinary medicine are*
*Taken from the NIOSH list of antineoplastic and other hazardous drugs in healthcare settings, 2014.
There are many points of potential exposure to a hazardous drug that must be considered when developing a safety plan for your hospital:
- Manufacture and packaging
- Shipping and receiving
- Drug preparation
- Drug administration
- Drug disposal
- Drug spills
- Drug metabolites in patient urine/feces
Steps to ensure safety can be taken at each of the potential points of exposure. Some general guidelines for safety in the clinical setting are listed below:
- Prepare and administer chemotherapy drugs in a dedicated room where eating and drinking is strictly prohibited.
- Draw up drugs in a biologic safety cabinet (see the CDC/NIH document Primary Containment for Biohazards: Selection, Installation and Use of Biological Safety Cabinets). One study documented that pharmacists using only horizontal flow cabinets had mutagenic substances in their urine, but those who used vertical flow Class II B biological safety cabinets did not.
- Wear appropriate personal protective equipment (PPE) to prevent exposure, including but not limited to gowns, chemotherapy-grade gloves, eye mask, face mask or respirator if aerosolization is possible. Change gloves every 30 minutes or if there is a puncture or tear. Gloves should cover the cuff of the gown. Use a full face shield or eye protection. Use a respirator with drugs that may vaporize at room temperature (e.g. carmustine, cisplatin, fluorouracil, cyclophosphamide, Mustargen®). Respirators need to be professionally fitted once a year.
- Utilize a closed system for delivering chemotherapy. Three examples of those available in veterinary medicine are OnGuard®, Equashield® and PhaSeal®.
- Clean all surfaces and wash hands after chemotherapy administration.
- Dispose of chemotherapy agents and materials appropriately in closed hazardous waste bins NOT medical waste/sharps containers.
- Have a spill kit and plan available in the case that a spill should occur.
Protecting ourselves, our staff, our patients and clients can be achieved with careful implementation and monitoring of safety systems. It is a large undertaking, but the oncologists at BluePearl Veterinary Partners at Town Center – Virginia Beach and Greenbrier, can provide safely administered chemotherapy to your patients. Please contact us with any questions or for consultations.
Other helpful websites
- gov/niosh/docs/2014-138. This is the 2014 hazardous drugs list for 2014.
Connor, TH et. al. Preventing Occupational Exposures to Antineoplastic Drugs in Health Care Settings. CA: A Cancer Journal for Clinicians. 2006; 56:354-365.
Valanis, B et.al. Occupational Exposure to Antineoplastic Agents: Self-Reported Miscarriages and Stillbirths Among Nurses and Pharmacists. Journal of Occupational & Environmental Medicine: August 1999; Volume 41, Issue 8:632-638.
Yuki, M. et. al. Exposure of family members to antineoplastic drugs via excreta of treated cancer patients. J oncol Pharm Pract. 2013; 19 (3):208-17.
Nutritional Support of Ill Patients
Ill patients have a higher nutritional need than healthy animals. The presence of illness or trauma induces hormonal changes, which cause an increase in the pet’s metabolism. Additional calories are required to fuel the cells involved in healing and protecting the body. Should additional nutrition not be made available, the body will break down its own protein, carbohydrate and fat stores to provide the extra fuel.
Patients not receiving adequate nutrition to support their higher metabolic needs have been shown to develop infection more frequently and to be prone to wound dehiscence. Protein breakdown in the body for energy will adversely affect the functions of the heart, respiratory system and gastrointestinal tract. Compromise to the patient’s organ function further complicates the patient’s health. Studies demonstrate that patients receiving adequate nutritional support have more rapid and successful recoveries from episodes of illness, trauma, and surgery.
Technicians are in an advantageous position to identify patients who may not be receiving adequate nutrition. Within 3 to 5 days of a patient’s inappetance the protein and fat stores required to maintain the health of the patient start to become depleted. Weight loss, the absence of adequate food intake for more than 3 days, weakness and lethargy, low blood sugar levels, and low blood protein levels should all prompt a technician to inquire of the doctor whether additional nutritional support needs to be considered. The more severe the injury, the more compromised the patient’s health prior to the injury, and the chronicity of the injury also factor into the decision whether to pursue nutritional support.
How to Feed
A number of methods are available to feed patients who do not ingest an adequate amount of nutrition. Enteral feeding of patients, if possible, is recommended as it is less expensive and is more physiologic allowing the body to decide how many and which nutrients will be assimilated. Parenteral feeding is typically reserved for patients too debilitated to safely receive enteral feeding or those with nonfunctional gastrointestinal tracts.
The method of enteral feeding utilized in a particular patient varies with the pet’s underlying illness, the disposition and alertness of the pet, the type of feeding tube available, and the preferences of the veterinarian providing the patient’s healthcare. Each method of assisted feeding has its advantages and disadvantages. It is important that technicians overseeing the patient’s care understand the methods and risks associated with the feeding technique utilized.
Methods of Enteral Feeding
Many patients can be coaxed to eat by warming the food, providing a variety of diet types or spoon-feeding.
Appetite stimulants work best in cats with only mild illness. They appear to stimulate the appetite center of the brain. Appetite stimulants tend to be less effective in dogs.
Syringe feeding will work only in very cooperative patients. There is risk for the patient aspirating the food if the feedings are given too quickly.
Nasoesophageal tubes are most commonly used in smaller patients with lower caloric requirements. Limitations to the use of these tubes include the need for a liquid diet and the subsequent volume of food that can practically be administered by this technique. Nasoesophageal tubes are easy to place and require no anesthesia but can be irritating to the nose. Intermittent feedings or a continuous infusion of nutrition (pictured) can be provided by this method.
Esophagostomy tubes are placed into the cervical esophagus through a small incision in the overlying skin. They are easy to place, although general anesthesia is required. Esophagostomy tubes are very safe and allow for the infusion of larger volumes of fluid-based nutrients than can be achieved using smaller nasogastric tubes.
Gastrostomy tubes require specialized equipment to be placed. A number of methods for placement have been described. Mushroom-tipped feeding tubes empty directly into the stomach. Gastrostomy tubes have the advantage of not interfering or causing discomfort around the patient’s neck region. They are especially useful in patients with disease affecting the mouth, throat or esophagus.
Jejunostomy tubes must be placed surgically through the side of the abdomen into the small intestines. They are typically placed when there are concerns for gastric disease, problems with vomiting, or upper GI motility problems. Special diets containing more elemental nutrients which require less digestion must be utilized. A pump is used to continuously infuse small volumes of liquid nutrition so as not to overwhelm the intestines with too much volume.
Feeding tubes should be clearly marked so as to minimize complications associated with their use. An Elizabethan collar may be required to prevent the pet from bothering the tube.