April 2006 Issue

Featured case study: Two-and-a-half-year-old spayed female terrier mix, Rusty
by Peter Kintzer, DVM, DACVIM, Boston Road Animal Hospital, Springfield, Massachusetts

“This case illustrates why it is necessary to determine electrolytes whenever running a chemistry profile on a patient. They were critical clinical clues in this particular case that allowed us to reach the correct diagnosis in this patient.”

Physical Exam
Rusty was depressed, 5% dehydrated and thin. Mucous membranes were pink and the CRT was two seconds. Temperature, pulse and respiratory rate were normal. Rusty weighed 40.2 lb (weight was 49.0 lb six months previous). Auscultation of the chest was unremarkable. The abdomen was tense and uncomfortable on palpation. Blood pressure (Doppler) was 75.

Plan
Samples for baseline laboratory data, including a complete blood count (CBC), clinical chemistries with electrolytes and a complete urinalysis with a urine culture, were submitted.

Morphology comments: 1+ anisocytosis; adequate platelets

Erythron—There is only a slight increase in the red cell distribution width (RDW), which suggests mild variation in erythrocyte size (anisocytosis). Mild anisocytosis is confirmed with a short review of the blood film (note morphology comment).

Leukon—There is a mild lymphocytosis with no other quantitative leukocyte abnormalities. No immature neutrophil population (bands) and no neutrophil toxicity were noted during the short review of the blood film. In light of the clinical presentation, a condition where endogenous glucocorticoid influence would be commonly seen, the lack of a lymphopenia is a significant finding that indicates the lack of any significant endogenous glucocorticoid release by the adrenal glands.

Thrombon—Platelet numbers are within reference-range limits, which is confirmed during the short review of the blood film (note morphology comment).

Figure 1—Peripheral blood film, Wright’s stain: Note the mild anisocytosis, as well as several normal platelets, a normal neutrophil and a normal eosinophil.

Kidney panel—The mild increase in BUN and creatinine indicate a decreased glomerular filtration rate (GFR). The lack of a concentrated urine specimen would support renal insufficiency, however, in light of the significantly decreased sodium, the potential of medullary washout of sodium interfering with the concentrating ability of the kidney is highly likely. Both prerenal and renal azotemia must be considered at this time.

Electrolytes—There is a significant hyperkalemia and hyponatremia. The chloride appears to be following sodium appropriately, suggesting no primary significant metabolic acid-base disturbance. Potential causes for hyperkalemia include acute renal failure, chronic renal failure, urethral obstruction, uroperitoneum, metabolic acidosis, severe congestive heart failure, gastrointestinal diseases, pleural or peritoneal effusions, hypoadrenocorticism, pseudohyperkalemia and drug therapy. Potential causes of hyponatremia include diuretic therapy, congestive heart failure, renal disease, liver failure, gastrointestinal disease, urethral obstruction, uroperitoneum, hypoadrenocorticism, syndrome of inappropriate ADH secretion, primary polydypsia and pseudohyponatremia. The hypochloremia likely is a result of the hyponatremia.

Urinalysis—The urine specific gravity of 1.018 in the face of dehydration indicates that there is an impaired ability to concentrate urine in this patient. Both renal insufficiency and medullary washout of sodium must be considered. The finding of a few coccal bacterial forms in a free-catch urine specimen is unremarkable and likely associated with simple contamination from the external urogenital tract.

Next steps—Rusty was given a bolus of 0.9% NaCl intravenously followed by continued intravenous fluids, antibiotics and famotidine. Abdominal radiographs were requested to help investigate potential underlying gastrointestinal disease. Also, since there were no physical examination findings to support most of the other diseases that could cause the electrolyte abnormalities seen (see above), investigation into the potential of hypoadrenocorticism was performed.

Final diagnosis
Hypoadrenocorticism (Addison’s disease)—A pre- and one-hour post-value of less than 2.0 µg/dL indicates no adrenal response supportive of a diagnosis of Addison’s disease.

Clinical case outcome
Intravenous injections of dexamethasone sodium phosphate were added to the treatment protocol for the next 24 hours and then changed to a tapering dose of oral prednisone. By 24 hours after initiation of therapy, the electrolytes and creatinine were normal and the patient was bright, alert and responsive (BAR) and eating well. The patient made an uneventful recovery and was discharged three days after admission on a daily replacement dose of prednisone and monthly injections of desoxycorticosterone pivalate (DOCP; Percorten®).

Comment—The combination of a urine specific gravity of 1.018 and elevated BUN and creatinine in this patient could have been misinterpreted as resulting from primary renal disease. However, 50% or more of patients with hypoadrenocorticism have an impaired ability to concentrate their urine (specific gravity <1.030), with some falling in the isosthenuric range, in the presence of azotemia or dehydration. This decreased renal concentrating ability has been attributed to medullary washout of sodium and chloride (responsible for interstitial hyperosmolarity compared to plasma and urine) and decreased medullary blood flow. The recommendations contained in Diagnostic Edge educational materials are intended to provide general guidance only. As with any diagnosis or treatment, you should use clinical discretion with each patient based on a complete evaluation of the patient, including history, physical presentation and complete laboratory data. With respect to any drug therapy or monitoring program, you should refer to product inserts for a complete description of dosages, indications, interactions and cautions.

We want to hear from you. Let us know what you think about this case and tell us about any other case topics that you would like to see. E-mail us at diagnosticedge@idexx.com.

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Get Connected! Your VetStat® Electrolyte and Blood Gas Analyzer can now connect to the IDEXX VetLab® Station (LaserCyte®) computer.

By connecting your VetStat® analyzer to the IDEXX VetLab Station (LaserCyte) computer, you can have all your test results printed in one comprehensive report that can help you make the most accurate diagnoses and recommend the most effective treatment. The report is also a great way to help you talk with your clients about their pets’ health, the tests you run and your diagnosis and treatment decisions.

When you connect your VetStat analyzer to the IDEXX VetLab® Station (LaserCyte) computer, you open up a whole new world of information management for your practice. The IDEXX VetLab Station offers an unprecedented level of information consolidation, including a comprehensive record of each patient’s diagnostic history, parameter-trending capabilities, interpretive information and helpful video guides.

The VetStat® Electrolyte and Blood Gas Analyzer is an integral part of the IDEXX VetLab® system of in-house analyzers—the most comprehensive in-house testing solution available—for the most thorough patient care possible.

For more information or to request a demonstration or a quote, contact the IDEXX sales department at 1-800-814-1605 or e-mail diagnosticedge@idexx.com.

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Now running samples is even faster and easier with NEW lithium-heparin syringes and capillary tubes for the IDEXX VetStat® Electrolyte and Blood Gas Analyzer

The new lithium-heparin syringes and capillary tubes:

• Improve sample prep workflow
• Eliminate the need for a lithium-heparin tube for use with the VetStat® analyzer
• Allow you to go directly from the blood draw to running the sample

Vital Signs lithium-heparin syringe:

• Available directly from IDEXX or your authorized IDEXX distributor

Drummond lithium-heparin capillary tube:

• Available directly from IDEXX or your authorized IDEXX distributor

For easy instructions on how to use these beneficial accessories, see the NEW VetStat analyzer sample preparation poster enclosed in the VetStat® 1.02 software release.

If you have any questions about the VetStat analyzer lithium-heparin syringes, contact IDEXX Customer Support at 1-800-248-2483 or e-mail diagnosticedge@idexx.com.

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Kitten season is here! This is the first in our three-part series on quick tips for kitten season.*

Kitten quick tip 1—Blood-draw tips
by Michelle Kahn, MS, DVM

Blood collection in the kitten doesn't have to be a painful and difficult experience for the patient or for you. Here are some suggestions to help you quickly and easily obtain your kitten blood samples:

• Use a 1-mL syringe with either a 25-g or 26-g needle.

• Use water instead of alcohol to wet the haircoat.

• A slower aspiration of blood is essential to avoid collapsing the vein.

• If you are sampling from the jugular vein, extend the head, but keep the neck slightly relaxed.

• Try distracting the kitten by gently tapping on its head.

• In the worst case scenario, try using an insulin syringe and drawing your sample from the saphenous vein while keeping the kitten in a stretch-restraint.

*Watch for tip 2 in our May 2006 and tip 3 in our June 2006 issues.

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Strengthen your medication monitoring
by Wendy S. Myers, Communication Solutions for Veterinarians, Denver, Colorado

You can improve medication monitoring with protocols set by your doctors, automated reminders in your veterinary software and colored labels on prescription vials. Pharmaceutical manufacturers recommend monitoring to ensure safe administration and to identify any side effects or potential complications or interactions with other drugs. Routine monitoring of pets on long-term medications also helps veterinarians establish a baseline for patients and detect any changes early so medication adjustments can be made.

Many pharmaceutical package inserts and veterinary journals have suggested protocols you can reference when developing your guidelines.

You can improve compliance for patients with an effective reminder system. Send reminders weekly rather than monthly to keep a steady flow of clients booking appointments, even out cash flow and reduce stress for staff and doctors. Try a three-tiered approach:

To create your practice’s protocols for medication monitoring, have doctors discuss the type and frequency of tests for arthritis, heart, seizure, thyroid, urethral incontinence and allergy medications. Many pharmaceutical package inserts and veterinary journals have suggested protocols you can reference when developing your guidelines. For example, consider conducting liver- and kidney-function blood tests prior to administration of arthritis medication and repeat them every six months.

When educating clients about long-term medications and monitoring, use both verbal and written instructions. Give clients the brochure, Prescription Medications: Testing helps us choose the right medication—monitoring helps ensure lasting effectiveness from IDEXX Laboratories. (633 KB) Explain why you need to conduct blood tests prior to drug administration, as well as the intervals of routine retesting.

When the initial prescription for a long-term medication is filled, enter a reminder in your veterinary software for the follow-up blood test. Create a computer code such as “Arthritis Medication-Monitoring Blood Test” that has a six-month reminder. When refilling the prescription, if bloodwork will be due before the next refill, put a colored label on the prescription vial, such as “Blood test required before next refill.” Print sheets of fluorescent labels (available at office supply stores) and keep them in the pharmacy. With a postcard reminder and a fluorescent label on the bottle, you’ll help clients remember to schedule patients’ blood tests for medication monitoring before the last pill is gone.

When educating clients about long-term medications and monitoring, use both verbal and written instructions.

Protocols, automated reminders and stickers on prescription vials ensure your patients get the follow-up monitoring they need. As the pet population ages and the use of long-term medications grows, more patients will need routine testing to confirm the safe administration and proper dosing of long-term medications. Start your medication-monitoring program today.

Wendy S. Myers owns Communication Solutions for Veterinarians in Denver, Colorado, and provides consulting services on client service, marketing and hospital management. She is the author of two books and four videos. You can reach her at 1-720-344-2347 or visit www.mycommunicationsolutions.com.

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Education and Events

We offer a variety of training events about emerging trends and best practices in veterinary diagnostics in a forum designed to involve, educate and motivate you and your staff. Here are some of the upcoming educational events.
See a full listing.

Seminars

• Infectious Disease Update
  Richard Ford, DVM, MS, DACVIM, DACVPM
• Update on Feline Retroviruses
  Susan Little, DVM, DABVP
• Advances in Diagnosis, Prevention and Treatment of Lyme Disease and Lyme Nephritis
  Richard Goldstein, DVM, DACVIM, DECVIM-CA

Teleconference

• Ehrlichiosis and Anaplasmosis: Common Questions and Concerns
  Rick Alleman, DVM, PhD, DABVP, DACVP

Visit the education and events calendar, click the date to view the details, fill out and submit the form to register.

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NEW this month—FREE CE Credit!

Can you identify the cell types indicated and suggest an underlying cause for the process in this Diff Quik® stain of a fine-needle aspirate from a skin mass on a dog?

You're already stepping up to take the Interactive Challenge—and now you can step up your CE credits, too! Earn a half-hour of FREE CE credit for each month's challenge.*

Not a Diagnostic Edge subscriber? Subscribe now!

Questions:

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Thanks for taking the April Diagnostic Edge Interactive Challenge!

*Each interactive challenge meets the requirements for 0.5 hours of continuing education credit in jurisdictions that recognize AAVSB’s RACE approval; however, participants should be aware that some boards have limitations on the number of hours accepted in certain categories and/or restrictions on certain methods of delivery of continuing education.

AAVSB Provider Number 106

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