This lecture will discuss caring for the seizing cat, their presenting symptoms and medications that may be used to stabilise these patients. Cats are not small dogs and have their own particular considerations. Some of the learning objectives for this lecture are listed below.

• Recognise seizure behaviour in felines.
• List some of the common medications used to stabilise these patients.
• Understand the nursing considerations for these patients.
• Identify the common causes of epilepsy in cats.
• Describe the basics of how seizures affect the brain.

Introduction

A seizure is defined as "a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain".¹ The brain is normally kept in a state of equilibrium by the balance between excitatory (glutamate) and inhibitory (gamma-aminobutyric acid [GABA]) neurotransmitters. A change in this balance is what may often lead to a seizure. A seizure is normally transient and lasts between 2–3 minutes; any seizure lasting over 5 minutes, or two or more seizures with no recovery of consciousness in-between, can be classed as status epilepticus and is a life-threatening emergency.² If the patient continues to seizure, this can result in central nervous system damage as well as systemic injury.

The main categories for seizures in cats include idiopathic (primary—no underlying brain lesion present), symptomatic (secondary—underlying brain lesion), probable symptomatic and reactive epileptic seizures.

• Symptomatic epilepsy causes include hypertensive encephalopathy, polycythemia, coagulopathy, different forms of encephalitis, trauma and intracranial neoplasia, to name a few.
• Probable symptomatic seizures may be induced post-trauma, post hypoxic encephalopathy and postencephalitic seizures.
• Reactive epilepsy causes include a seizure caused by toxins (pyrethroids/ethylene glycol, etc.) and metabolic changes like hyperthyroidism, renal dysfunction leading to renal encephalopathy, hypoglycemia, electrolyte imbalance, infectious disease and hepatic encephalopathy (list not exhaustive).³

Seizure Stages

Seizures have four stages and a beginning and an end. The four stages are the prodrome, aura, ictus and postictal stages.

Prodrome: This is the time that leads up to a seizure and can last for various amounts of time. Behaviours in this stage can include attention-seeking and anxious behaviour.

Aura: This is the stage directly before what is known as a seizure (ictus). This can only be confirmed via EEG, which is difficult in the feline patient.

Ictus: This is the seizure event itself.

Postictal: The stage directly after the seizure; the behaviours in this stage and their consistencies can help reveal whether a seizure has really occurred. Some common behaviours include aggression, polyphagia, polydipsia and ataxia.

Seizure Presentation in Cats

Seizures in cats can present as focal and or generalised. Seizures in cats can begin with focal seizures, which may or may not lead to secondary generalised seizures;³ the focal seizures only affect part of the body and can be much more difficult to recognise. The complex focal seizures may be so subtle that they go unnoticed until generalised seizures occur. Examples of focal complex seizures in cats include excessive drooling/salivation, facial twitching, mydriasis, tremors among others. The patient may remain in sternal recumbency—making focal seizures difficult to spot even in the veterinary environment. The cat may exhibit climbing behaviour and may or may not lose control of its bladder or defecate during a focal seizure. All of these symptoms and lack of consistency from individual to individual makes monitoring and identifying seizures, especially when focal, difficult for the veterinary nurse.

Medications Used to Control Acute Seizures in the Cat

This list of medications is non-exhaustive and act only to highlight the rationale behind the use of certain drugs. When possible, it may be prudent to control blood pressure and glucose before the administration of antiepileptic drugs—as directed by the vet.

Benzodiazepines: These drugs are often the first port of call for the seizing patient, given as bolus therapy with the intention of stopping seizure activity. They have a short onset of action working almost instantaneously; however, they also have a short duration of action, and they can be administered in different forms. A couple of examples of benzodiazepines seen in practice are diazepam and midazolam.

Diazepam can be administered IV and rectally, and up to 2–3 boluses can be given; alternatively, diazepam can be delivered over a constant rate infusion (CRI). Due to the risk of CNS depression and cardiorespiratory collapse, it is not recommended to administer more than 2–3 boluses of diazepam to the cat or dog.² Hypotension and phlebitis may occur on rapid administration due to the agent diazepam is carried in.

Midazolam may be administered IV, intramuscularly, buccally or nasally; it can also be delivered via CRI. Midazolam may have decreased CNS and respiratory depression compared to diazepam.²

Barbiturates: Phenobarbital is a barbiturate regularly used in practice. It can be administered orally or intravenously (IV) and is used for the acute and ongoing management of epilepsy. For acute seizure management, IV injection is normally preferred. Phenobarbital can cause negative cardiovascular effects, including hypotension;² slow IV administration and cardiovascular and respiratory monitoring may be required.

Patients who are not already under phenobarbital therapy will often be given a loading dose. This dose should be split over 3 to 4 doses and administered every 30 minutes. Phenobarbital takes around 30 minutes to take effect.²

Levetiracetam: Levetiracetam is a relatively new drug used in the control of acute and chronic management of seizures in cats and dogs. Levetiracetam can be administered IV, PO, and IM;⁴ loading doses are indicated for acute seizure control; it is well-tolerated in cats and dogs and has minimal adverse effects.⁵

Propofol: Propofol may be necessary for refractory status epilepticus patients. Due to the adverse effects on cardiovascular and respiratory systems, patients being administered bolus therapy or, more likely CRI therapy of propofol, need to be monitored carefully; intubation and ventilation may be necessary to maintain a clear airway, avoid aspiration pneumonia and to ensure oxygen and carbon dioxide (CO₂) levels remain within a normal range. Cats receiving multiple propofol infusions may acquire Heinz body formation, which can increase the recovery time.²

Ketamine: Ketamine may be used for refractory seizures in cats, although its use is still controversial. Drug resistance may occur after the initial stages of treatment of status epilepticus with GABA-ergic drugs. Ketamine has a different mechanism of action for stopping seizure activity; it decreases glutamine activity (an excitatory neurotransmitter) and has neuroprotective properties.⁶

Nursing Considerations for Seizing Cats

Housing: It is important that the veterinary nursing staff have a good visual of high-risk patients. Feline patients who are likely to seizure should be in a kennel that is ideally eye level and close to the nursing station, whilst being in a quiet spot so that the cat has a calm space to rest.

Stress reduction: This is a consideration in all of our patients; cats can be especially sensitive to stressors like loud noises, bright lights and rough handling. Every consideration should be taken to make sure stress is reduced as much as possible by reducing the noise of personnel (that may include reducing the number of people allowed to enter a ward or room at any given time). Lights should be dimmable in the ward/ICU environment.

It goes without saying that our patients should be handled with utmost care and sensitivity. Towel wraps and potentially aides such as cat restraint bags should be used when handling patients should they become fractious. If possible, the patient should be allowed the opportunity to acclimatise to a situation and patience given for a procedure to take place; this, unfortunately, is not always possible in a busy veterinary hospital. If it is possible for the task to be delegated to the veterinary nursing team, in the author's experience, often the procedure can be undertaken at a quieter and less stressful time.

Where possible, patient treatments, monitoring and interventions should be bundled together to minimise patient stress.

Be prepared: Making sure doses of antiepileptic drugs (AEDs) such as midazolam are already calculated or drawn up on the kennels is very useful. If not already drawn up, then an ampoule of the medication and a prepared syringe and needle is helpful to have ready. Make sure these emergency medications go everywhere with the animal; for example, into other rooms where they may be being examined. Some cats show signs of aggression during aura, ictal and postictal phases; a thin extension line (normally under 2 ml volume) attached directly to the patient's IV catheter is particularly beneficial. AEDs can be administered through this line without having to get near the patient; this may significantly reduce potential injury to staff and quickly halt seizure activity.

Recumbent patients: Recumbent patients will need to be regularly turned (every 4 hours) to reduce the risk of decubitus ulcers and lung atelectasis. Soft bedding should be used. They must be kept clean and dry via bladder catheterisation or regular expression; other considerations are oral hygiene if necessary and eye lubricant, which should be applied every 2–4 hours depending on hospital protocols. Nutrition must be addressed in patients who are unable to eat and drink by themselves or where it is deemed unsafe to do so due to inadequate abilities to swallow.

Often, around-the-clock monitoring is necessary for these patients especially if they are being managed with sedatives and constant rate infusions. Monitoring with multiparameter devices can be especially useful, these regularly include an electrocardiogram (ECG), non-invasive blood pressure (NIBP), oxygen saturation (SPO₂), end-tidal CO₂ (If the patient is intubated) and temperature probes. Oxygen therapy, intubation ± ventilation may also be necessary, depending on the patient's needs and medications being administered. The patient position and posture should be observed and documented. Rigidity of all four limbs vs. forelimb rigidity with hind limb flexion could help the clinician with making a diagnosis and also indicate herniation of the cerebellar or brainstem compression.

Regular neurological examination and evaluation should be performed; modified Glasgow coma scores can be a useful aid when nursing these patients.

Reducing increased intracranial pressure (ICP): Avoiding procedures that could increase ICP is a must; this includes jugular blood sampling, tight restraint around the head and neck and placing nasal cannula. Any restrictive collars should be removed and the head elevated by 15–30 degrees if the patient is in lateral recumbency. Wooden boards can be useful for this rather than elevating the head alone with blankets or towels. Early extubation of intubated patients to avoid coughing may help reduce the risk of increased ICP.

Temperature control: Patients who arrive with cluster seizures or in status-epilepticus may have elevated body temperatures. These patients may need active cooling; however, the temperature could reduce via passive cooling once fluid therapy is initiated and the seizure activity is stopped via anti-epileptic drugs. The patient should have their temperature monitored regularly to ensure rebound hypothermia does not occur. It may be prudent to keep epileptic patients on the cooler side, as hypothermia can stimulate anticonvulsant and neuroprotective mechanisms in the brain and seizure activity has been shown to lessen in the presence of mild to moderate hypothermia (36.7–37.7°C) in experimental animals and in humans.⁶

Continuity: Continuity is important for all ICU patients; ideally, the same nurse should stay with these high-risk patients for the duration of their shift to give continuity of care. This allows for regular reports and discussions with the case vet and the ability to better track trends in the patient's vital signs.

References

1.  Fisher RS, van Emde Boas W, Blume W, Elger C, Genton P, Lee P, et al. Epileptic seizures and epilepsy: definitions proposed by the International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy (IBE). Epilepsia. 2005;46:470–472.

2.  Blades Golubovic S, Rossmeisl JH Jr. Status epilepticus in dogs and cats, part 2: treatment, monitoring, and prognosis: status epilepticus: treatment and monitoring. J Vet Emerg Crit Care. 2017;27:288–300.

3.  Pakozdy A, Halasz P, Klang A. Epilepsy in cats: theory and practice. J Vet Intern Med. 2014;28:255–263.

4.  Platt SR, Olby NJ, Others. BSAVA manual of canine and feline neurology. British Small Animal Veterinary Association. 2014.

5.  Silverstein D, Hopper K. Small Animal Critical Care Medicine - E-Book. Elsevier Health Sciences; 2014.

6.  Gioeni D, Di Cesare F, D'Urso ES, Rabbogliatti V, Ravasio G. Ketamine-dexmedetomidine combination and controlled mild hypothermia for the treatment of long-lasting and super-refractory status epilepticus in 3 dogs suffering from idiopathic epilepsy. J Vet Emerg Crit Care. 2020;30:455–460.