Peer Reviewed OCTOBER 2005 VOL 7.9 STANDARDS of CARE® EMERGENCY AND CRITICAL CARE MEDICINE FROM THE PUBLISHER OF COMPENDIUM STATUS EPILEPTICUS IN DOGS J. D. Smith, DVM Small Animal Intern T. W. Axlund, DVM, MS, DACVIM (Neurology) Associate Professor Department of Clinical Sciences College of Veterinary Medicine Auburn University tatus epilepticus (SE) refers to sustained focal or lying cause in young (<1 year) toy breeds. generalized seizure activity lasting longer than • Infectious inflammatory diseases can occur in dogs S5 minutes or cluster seizure activity (i.e., multiple of any age but are most common in dogs younger seizures characterized by lack of a defined interictal than 1 year. period). SE is a life-threatening emergency that requires • Idiopathic epilepsy should be considered as an immediate medical treatment. Initial management is underlying cause in dogs 1 to 5 years of age. focused on stopping seizure activity, most commonly • Intracranial neoplasia and metabolic diseases are with a benzodiazepine (e.g., diazepam, midazolam). most common in dogs older than 5 years. Untreated generalized seizure activity can result in seri- ous metabolic, cardiovascular, and respiratory dysfunc- • Toxic, metabolic, and noninfectious inflammatory tion; permanent brain damage; and/or death. disorders can occur at any age. Most dogs presenting with SE exhibit generalized Breed Predisposition: Breeds with a proven or highly motor seizure activity. Data gathered from limited epi- suspected genetic predisposition for idiopathic epilepsy demiologic studies regarding populations of dogs pre- include beagles, German shepherds, Labrador retriev- senting for SE indicate that the majority of dogs have ers, golden retrievers, vizslas, Belgian Tervurens, and primary (idiopathic) or secondary (acquired) epilepsy English springer spaniels, but the condition can occur (i.e., epilepsy secondary to intra- or extracranial dis- in any dog. ease). Gathering a thorough history from the client is imperative in determining the potential cause of SE in a Owner Observations given patient and will aid in formulating appropriate • Clients may observe either one continuous pro- diagnostic and therapeutic plans and in establishing the longed seizure episode (lasting longer than 5 min- prognosis. The longer SE remains untreated, the less the utes) or multiple seizures between which the dog chance for response to initial seizure control and the does not regain full consciousness. poorer the prognosis for a positive clinical outcome. • Seizure activity may consist of generalized convul- DIAGNOSTIC CRITERIA sive or focal seizures. Historical Information Other Historical Considerations/Predispositions • History of idiopathic (primary) epilepsy. Gender Predisposition: None. Age Predisposition Also in this issue: • Congenital abnormalities (e.g., portosystemic shunt, hydrocephalus) should be considered as an under- 7 Electrocution and Electrical Cord Injury 1 Questions? Comments? Email [email protected], fax 800-556-3288, or post on the Feedback page at www.SOCNewsletter.com. OCTOBER 2005 VOL 7.9 • History of known intracranial disease (e.g., previously diagnosed space- STANDARDS CARE® occupying lesion, meningoencephalitis). EMERGENCY AND CRITICALof CARE MEDICINE • Past history of SE. Editorial Mission: • Known toxin ingestion. To provide busy practitioners with concise, • Head trauma. peer-reviewed recommendations on current treatment standards drawn from published • Known metabolic disorder. veterinary medical literature. Physical Examination Findings This publication acknowledges that standards The presentation of SE and the associated physical examination findings may may vary according to individual experience and practices or regional differences. The differ from case to case because of the variable etiology and clinical behav- publisher is not responsible for author errors. ior of SE. • Continuous generalized or focal seizure activity may be observed on Compendium’s Standards of Care: presentation. Emergency and Critical Care Medicine® • In cases of prolonged SE in which cerebral autoregulation has failed, the is published 11 times yearly (January/February is a combined issue) patient may present in a comatose state and only occasional muscle by Veterinary Learning Systems, twitching may be observed. 780 Township Line Road, Yardley, PA 19067. • Focal or multifocal neurologic deficits may be present and may be attrib- The annual subscription rate is $83. utable to either the underlying cause of the seizures (especially with For subscription information, call 800-426-9119, fax 800-589-0036, intracranial disease) or to postictal neurologic impairment (cortical blind- email [email protected], or visit ness, disorientation, lethargy). www.SOCNewsletter.com. Copyright • An elevated rectal temperature may be present in cases of prolonged con- © 2005, Veterinary Learning Systems. vulsive seizures. Editor-in-Chief • External signs of cranial trauma, such as soft tissue injury, broken teeth, or Douglass K. Macintire, DVM, MS, palpable skull fractures, may be detected. DACVIM, DACVECC • It is important to note that in rare situations, mechanically “quiet” seizures Editorial, Design, and Production (nonconvulsive epilepsy) can occur, in which an animal shows no outward Lilliane Anstee, Vice President, signs of seizure (e.g., tonus, urination, defecation, clonus) but is still expe- Editorial and Design riencing the cerebral overactivity associated with a seizure. Thorough neu- Maureen McKinney, Editorial Director rologic examination may reveal neurologic deficits or other abnormalities Cheryl Hobbs, Senior Editor (e.g., pupil asymmetry or abnormal pupillary light reflex, abnormal oculo- Michelle Taylor, Senior Art Director cephalic reflex, subtle focal muscle twitching) in a nonresponsive patient, which may lead one to suspect this form of seizure is occurring. This type Bethany L. Wakeley, Studio Manager of seizure is as damaging to the cerebral cortex as the more common gen- Chris Reilly, Assistant Editor eralized (systemic) seizure and needs to be treated as aggressively. Unfor- Kristin Sevick, Editorial Assistant tunately, this electromechanical dissociation is impossible to diagnose Andrea Vardaro, Editorial Assistant without an electroencephalogram (EEG). Editorial Review Board Mark Bohling, DVM Laboratory Findings University of Tennessee Initial diagnostics should include a complete blood count, serum chemistry Harry W. Boothe, DVM, DACVS profile, urinalysis, electrocardiography (ECG), blood pressure measurement, Auburn University arterial or venous blood gas analysis, partial or complete coagulation profile Derek Burney, DVM, PhD, DACVIM (especially if the patient is significantly hyperthermic or signs of disseminated Houston, TX intravascular coagulation [DIC] are present), and measurement of antiepilep- Joan R. Coates, DVM, MS, DACVIM tic drug (AED) levels if the patient is receiving phenobarbital or potassium University of Missouri bromide (KBr). Depending on the underlying cause of SE, the following Curtis Dewey, DVM, DACVIM, DACVS abnormalities may be present on clinical laboratory testing: Plainview, NY Nishi Dhupa, DVM, DACVECC Cornell University D. Michael Tillson, DVM, MS, DACVS KEY TO COSTS Auburn University $ indicates relative costs of any diagnostic and treatment regimens listed. $ costs under $250 $$ costs between $250 and $500 $$$ costs between $500 and $1,000 $$$$ costs over $1,000 2 OCTOBER 2005 VOLUME 7.9 • Hypoglycemia: Generally accepted as glucose levels • Magnetic resonance imaging: Indicated in patients below 60 mg/dl (reference range, 80–100 mg/dl), suspected of having a structural intracranial abnor- although clinical signs may not be evident until mality and is preferred for visualization of parenchy- concentrations become extremely low (< 30 mg/dl). mal changes, such as soft tissue masses, vasogenic Also, the severity of central nervous system (CNS) edema, and potential focal or multifocal inflamma- signs is generally a result of the rapidity of the drop in tory lesions. Changes may also be evident due to the blood glucose rather than the actual concentration. seizure activity itself. Disadvantages include cost • Hypocalcemia (serum ionized calcium [iCa2+] < 0.8 and need for general anesthesia. $$$–$$$$ mg/dl; reference range, 1.34 ± 0.05 mg/dl). • EEG monitoring: This is generally performed in a spe- • Polycythemia (packed cell volume > 55%; reference cialized hospital setting and can be used to diagnose range, 37% to 55%) and hyperproteinemia (>7.5 nonconvulsive epilepsy and to monitor response to g/dl; reference range, 5.1–7.3 g/dl) may be present treatment in patients being treated for SE. $$–$$$ and indicate dehydration. • Elevated creatine kinase activity (>368 U/L; refer- Summary of Diagnostic Criteria ence range, 92–367 U/L) due to skeletal muscle dam- • Continuous focal or generalized seizure activity age secondary to prolonged generalized seizures. lasting longer than 5 minutes or a history of cluster Muscle damage may also result in myoglobinuria. seizures without return to full consciousness be- • Metabolic acidosis (blood pH < 7.31; reference tween episodes. range, 7.31–7.42; bicarbonate < 17 mEq/L; refer- • History of known primary or secondary epilepsy ence range, 17–24 mEq/L; or total carbon dioxide < (intracranial versus extracranial disease) or known 14 mEq/L; reference range, 14–26 mEq/L), espe- toxin ingestion. cially in cases of ethylene glycol toxicosis. • Clinical pathology findings consistent with