Signs of illness in the rabbit (Oryctolagus cuniculus), rodent, and other prey species can be fairly subtle, and individuals often mask signs of illness until disease is quite advanced. Therefore, it is not uncommon for rabbits, rodents, and other exotic companion mammals to present on an emergency basis for veterinary care. Although appropriate analgesia and fluid therapy are essential for all critical patients, this article will focus on nursing care tips that can vastly improve the likelihood of a positive clinical response.
Caging the critical small mammal
Rabbits, rodents, and other prey species are easily stressed in a hospital setting and should be housed separate from predator species like cats, dogs, ferrets (Mustela putorius furo), and wildlife. Small mammals should ideally be kept in a dim, quiet ward, or at least a quiet corner of intensive care. Provide some form of visual security or hiding place such as a cardboard box or a small surgical towel. Draping cloth over part of the incubator or taping newspaper over a portion of the cage front can also be helpful. Visual security can be particularly important for fearful rabbits that would otherwise choose hiding over access to food and water sources—or even a litter box. Ensure the litter material provided is safe if ingested by the rabbit, such as shredded newspaper or a commercial recycled paper product. Some social species, like rabbits, may also benefit from the presence of a companion animal (Bays 2012).
Critical patients may also require supplemental heat. See body temperature below.
Visit Basic Husbandry: Housing the Non-Traditional Pet for additional information.
If respiratory distress is evident, the patient should ideally be placed in an oxygen cage prior to handling or physical examination. If space allows, set the entire carrier into the intensive care unit (ICU) cage. If the patient must be handled for transfer into the oxygen cage, swiftly remove any nasal discharge present if patient status allows. As obligate nasal breathers, the breathing of dyspneic rabbits and rodents can significantly improve after gentle cleaning of purulent discharge from the nares.
If your practice lacks an oxygen cage, a makeshift unit can also be created with the use of an induction chamber connected to an oxygen line. Alternatively, a plastic bag can be placed around the carrier or over the front of the hospital enclosure. Oxygen tubing is then placed into the bag. Unfortunately, both of these improvised methods carry the serious risk of overheating, which can exacerbate the patient’s respiratory distress.
Medicating the critical small mammal
Parenteral medications in the form of subcutaneous injections are generally well tolerated in small mammals, particularly when the smallest gauge needle possible is used and injection sites are alternated.
Epaxial musculature is an excellent site for intramuscular injections in many critical rabbits since the muscle mass tends to be large and little manual restraint is required when compared to an injection into the thigh. When performing intramuscular injections in tiny patients, such as sugar gliders (Petaurus breviceps) or rats and mice, insert the needle at an angle that is relatively parallel, and not perpendicular, to the femur. This approach will minimize the risk of accidentally introducing the needle near bone or the femoral sheath.
Exotic companion mammals are almost invariably given oral suspensions or pediatric syrups when oral medication must be administered. As with cats and dogs, the flavor of the suspension can have a profound effect on patient acceptance and ease of drug administration. Sometimes owners can recommend a flavor their pet may enjoy; however, rabbits and rodents often accept fruit flavors. Ferrets will sometimes accept chicken flavored medications but they tend to prefer sweet flavors like bubblegum, grape, orange, banana, or even vanilla. Make sure the flavoring used for ferret patients is sugar-free because subclinical insulinoma is a common problem in middle-aged to older ferrets (see Sequelae below). Avoid using sugary items like Nutri-Cal® (Tomlyn) in the debilitated ferret.
Although a compounded suspension is a far superior method of drug delivery, a small pill that is not bitterly flavored can sometimes be finely ground using a mortar and pestle, then offered with a small amount baby food of appropriate flavor by syringe.
Remember that herbivores, such as the rabbit and some rodents like the guinea pig (Cavia porcellus), are acutely sensitive to antibiotics with a Gram-positive spectrum. These animals can develop potentially fatal enterotoxemia secondary to the overgrowth of “bad” bacteria like Clostridium spp. (Box 1).
|Box 1. Antibiotics most likely to disrupt the gastrointestinal flora of small herbivores|
Visit LafeberVet’s article: Antimicrobial Therapy and Dysbiosis in Rabbits and Rodents for additional information.
Feeding the critical small mammal
Regardless of the underlying medical problem, nutritional support is vital to the survival of the critically ill small mammal. As in all species, feeding of the critical patient should only be instituted when the animal is warm and hydrated. Assist feeding by syringe or even by hand is usually recommended for the mild to moderately ill patient with adequate perfusion and normal hydration. Nevertheless, this important technique requires time and abundant patience. Take care to only syringe a small amount of food at a time. If an anorectic small mammal is unwilling or unable to swallow, placement of an esophagostomy tube or nasogastric tube may be necessary.
Even when nutritional support is required, all but the most critical small mammals should also be offered appropriate food items and a source of water. Although owners should be encouraged to bring the “regular diet” from home, the exotic animal ward pantry should ideally include:
- Fresh hay for small herbivores
- Rodent block and/or pellets
- Chicken baby food (free of onion powder)
- Vegetable or fruit baby food
- Hulled sunflower seeds for omnivorous rodents
Also be prepared to visit your local grocery store to purchase greens, palatable herbs such as cilantro and parsley, or carrot tops. Soaking these items in water before offering them to a rabbit or rodent can increase acceptance because the vegetables tend to be more turgid, and this practice may also increase the amount of fluids delivered orally.
Although many exotic animal hospitals maintain a supply of mealworms or crickets, avoid feeding insect prey to the debilitated insectivore. The chitin in the insect exoskeleton is a source of non-protein nitrogen which may be deleterious to water balance and renal function in the critical patient (Donoghue 2006).
Offer food and water in sturdy crocks unless the patient normally receives a water bottle at home, and maintain a collection so that the appropriate sipper tube size is available. Placing a small plastic lid beneath the sipper bottle can also minimize the risk of drips or water bottle malfunctions getting your debilitated patient wet.
Monitoring the critical small mammal
Monitoring the critically ill exotic companion mammal is a challenging balancing act. With the exception of the ferret, a gregarious predator species, the need to closely monitor the patient must be balanced with the animal‘s need for quiet and their urge to hide.
Appetite and eliminations
Closely monitor patient appetite, urine output, and fecal production. Count fecal pellets every hour if necessary. Regardless of the underlying problem, anorexia can rapidly lead to hepatic lipidosis and gastrointestinal hypomotility or even ileus.
Signs of pain or illness
Observe the patient for signs of pain or illness, particularly before manual restraint.
- The painful rabbit or rodent may display a hunched posture, abdominal straining, and teeth grinding or bruxism.
- The ferret suffering from abdominal pain can also grind its teeth loudly and nauseous ferrets may drool copiously and/or paw vigorously at the mouth.
- It is not uncommon for the stressed prey species to merely sit quietly and tensely, interacting little with their environment and exhibiting few signs of discomfort, even with acute trauma. This means that signs of distress or decline can be extremely subtle such as keeping the eyes half-closed or a dull or distant gaze.
- Also look for evidence of grooming. A dull, greasy appearance or a clumped coat can indicate decreased grooming behavior. Reduced grooming will also allow porphyrin tears to accumulate around the eyes and nares in small rodents like rats and mice (see Sequelae below).
Finally, keep the natural history of your patient in mind. An ICU technician working third shift may observe significantly more activity in nocturnal species such as rats or hamsters. These species are naturally inactive during the day, making behavioral assessment even more difficult.
Weigh critical small mammals at least twice daily using an accurate digital scale. For tiny patients, the scale should ideally weigh within at least 1-gram increments, as small weight changes may be clinically significant.
Like behavioral assessment, measurement of vital signs is not necessarily a straightforward process in the exotic companion mammal.
Respiratory rate is the easiest and least stressful parameter to measure, assuming breaths can be observed from a distance.
The ferret heart rate is normally 180 to 250 beats per minute (bpm) but can spike higher with excitement or lower with this species’ normal marked respiratory sinus arrhythmia. Unlike most mammals, the ferret heart is located relatively caudal within the thorax and auscultation is best performed between the seventh and tenth intercostal space.
Normal rabbit heart rates can be pretty similar to those of the ferret, however smaller breeds tend to have higher heart rates that can reach the high 200’s or low 300’s (Box 2).
|Box 2. Reported normal heart rates in select species (Quesenberry 2012)|
|Species||Heart rate (beats per minute)|
|African pygmy hedgehog||180-280|
No matter the size of your patient or their degree of tachycardia, heart rates are never “too high to count”. To keep track of a rapid heart rate select a pre-determined time frame in which to count beats (usually 6 or 10 seconds). Then count the heartbeats ausculted in beats of eight:
When time is up, simply do the math to calculate the beats per minute (Box 3).
|Box 3. Example of counting and calculating a rapid heart rate|
|Our sugar glider patient is scruffed through his Royal Crown bag, allowing the cloth to be lifted off of part of his body and your pediatric stethoscope gently placed over his chest. While ignoring his sounds of supreme indignation as much as possible, you look at the clock on the wall while listening to his rapid heartbeat. As the second hand hits 12 you begin to count “1,2,3,4,5,6,7,8…2,2,3,4,5,6,7,8…3,2,3,4,5,6,7,8.” Just as you finish “4,2,3,4,5,6,7,8 “ your 6 seconds is up.
8 times 4 equals 32. So that’s 32 beats in 6 seconds or 320 beats per minute.
It is standard practice in many emergency hospitals for clearly defined values to be listed in ICU orders for which the veterinarian on duty should be contacted, and this rule of thumb should hold true for all of the larger, more easily ausculted species like ferrets and rabbits. Values will vary with the species, the animal’s habituation to handling and restraint, and of course the underlying health problem. For example, ICU orders of the “average” post-operative ferret might read, “contact DVM if the heart rate is greater than 240 bpm or less than 140 bpm”.
The body temperature of normal ferrets and rabbits typically ranges between 37.7-38.8°C (100-102°F) (Box 4). With excitement and struggling, body temperature can rise to 39.4°C (103°F) or even 39.7°C (103.5°F).
With the exception of the ferret, rectal (or cloacal) temperature measurements are often reserved for severely debilitated patients or for individuals under general anesthesia (Box 4). Use a small, soft, flexible rectal thermometer, plenty of lubricant, and gentle technique. Note that the rectal wall is considered particularly delicate in rabbits and can be punctured with rough technique.
|Box 4. Reported normal body temperature in select species (Quesenberry 2012)|
|° C||° F|
|African pygmy hedgehog||35.4-37.0||95.7-98.6|
Some exotic animal practices use tympanic infrared thermometers. Although there appears to be little correlation between ear and rectal thermometer readings, ear thermometers can possibly be used to detect trends. The use of noncontact infrared laser thermometry to monitor small mammals may also show promise; however some laboratory animal studies show poor agreement between rectal temperature and noncontact infrared values (Chen 2006, Devalle 2005, Saegusa 2003).
Most small mammals that present in hypovolemic shock demonstrate hypothermia or a temperature less than 36.6°C (98°F). These patients must be actively warmed using methods that warm not only the external surface of the patient but also core body temperature (Box 5).
|Box 5. External and core warming methods|
|*As in other species, conduction heating techniques like hot water bottles or rice bags can be used in small mammals but use caution. If these items are allowed to cool they will quickly direct heat away from a tiny patient.|
Temperature changes can occur rapidly in small patients or in the long, lean ferret. So monitor your patient carefully to ensure that temperature readings not only move in the desired direction but also that the animal does not begin to overheat. Signs of overheating, such as open mouth breathing or lying flat out, are most likely to be observed in patients that are overweight, heavily furred, or stressed.
Perfusion and hydration status
Mucous membrane color and capillary refill time (CRT) provide information on vascular perfusion or tissue blood flow (Box 6). Perfusion is a related but separate issue to hydration, which is a measure of interstitial fluid content (Hackett 2015) (Box 7).
|Box 6. Physical indicators of perfusion status|
|*Visualization of gum color can be stressful in the conscious rabbit or rodent, but gently pulling down on the lower eyelid can allow evaluation of mucous membrane color|
|Box 7. Physical indicators of patient hydration|
Most small mammals presented for hypovolemic shock demonstrate hypotension such as systolic blood pressure less than 90 mmHg. Systolic blood pressure for small mammals normally measures 90 to 120 mmHg (Lichtenberger 2012, Lichtenberger 2004).
Indirect blood pressure can be obtained by oscillometric or Doppler techniques. The crystal of a Doppler heart monitor (Parks Medical) can be placed on the tail base in ferrets or distal paw in rabbits and a sphygmomanometer is used to take blood pressure readings.
After prolonged anesthesia, it is not uncommon for the recovering small mammal to enter the “wet noodle phase”. This stage of recovery tends to be most profound in the ferret in which the long, wiggly body becomes limp or floppy. It may take anywhere from minutes to hours for the patient to stir. Although the patient’s underlying health status can play a role, this prolonged recovery period is often the result of failure to maintain normal body temperature, particularly during prolonged periods of anesthesia. Therefore, prevention through the use of supplemental heat is particularly important.
The limp patient will not begin to shiver, which generates body heat, until they begin to rouse. Therefore, monitor body temperature frequently. Insertion of a rectal temperature probe can minimize the discomfort associated with multiple insertions of a thermometer. In addition to standard monitoring techniques, be sure to turn the “wet noodle” patient frequently, at least every 1 to 2 hours. Frequent turning from left or right lateral recumbency serves to rouse the animal and is particularly important in patients receiving high fluid rates to minimize the risk of fluid pooling.
Fluid therapy for the critical small mammal
Intravenous or intraosseous fluid therapy is frequently indicated to aid in the stabilization of critical patients. Ensure the safe and accurate delivery of fluids to your small patient with the use of a syringe pump or fluid pump that can accurately deliver fluids down to 0.1 ml per hour. A burette can also be used, but by itself does not prevent the delivery of excess fluid volumes.
Monitor small mammals on fluids very closely as profound changes can occur rapidly unless one is vigilant. The initial signs of overhydration can be quite subtle. Signs of overhydration can include serous nasal discharge, chemosis or conjunctival swelling, and increased skin turgor. As the problem advances, the patient will develop peripheral edema and body weight increases. Subcutaneous tissues can even develop a “jelly-like” consistency. If left unchecked, overhydration can lead to increased respiratory rate (tachypnea) and even respiratory difficulty (dyspnea) (Box 8) (Hackett 2015).
|Box 8. Possible signs of overhydration|
The fluid line and catheter site must also be carefully monitored, as small catheters can easily become blocked. Furthermore, patients that are allowed toweling can quickly become entangled, causing the line to kink or even dislodging the catheter. This problem is particularly common in ferrets, which have an instinctive need to burrow. Provision of a small surgical towel will meet the ferret’s behavioral needs while minimizing the risk of these complications. The fluid line must also be protected from chewing by rabbits and some rodents. As their clinical status begins to improve, most rabbits receiving fluids require Elizabethan collars, extensive bandaging, or even sedation to prevent them from pulling out the catheter or chewing through the line. Of course, the stress of restraint collars must be weighed against the benefits of fluid therapy. Collars also prevent the normal ingestion of nutrient-rich cecotropes or “night feces”.
Finally, use caution when flushing catheters. Keeping track of the volume and frequency of flushes can ensure catheter patency while preventing the excess administration of heparin or fluids to your tiny patient.
Potential sequelae to the stress of hospitalization
Rabbits and rodents
The critically ill small herbivore is always at risk for gastrointestinal (GI) stasis, a potentially fatal condition. The development of GI stasis or ileus is usually multifactorial but can involve stress, pain, and dehydration. Therefore, any evidence of gastrointestinal hypomotility such as reduced appetite, scant feces, or absence of feces should be taken very seriously.
Red oculonasal discharge, or porphyrin secretions from the Harderian glands of the eye, is generally considered a non-specific response to stress or disease in small rodents.
Pancreatic beta cell tumor or insulinoma is extremely common in middle-aged to older ferrets, and the stress of hospitalization and critical illness can precipitate a hypoglycemic crisis in ferrets with subclinical disease. Signs of hypoglycemia in the ferret can include weakness, ataxia, stupor, posterior paresis, collapse, seizure activity, as well as signs of nausea. Nausea in the ferret typically manifests as copious drooling and/or pawing at the mouth.
Stress can also worsen or precipitate another common condition in the ferret: Helicobacter gastritis. Monitor patients for teeth grinding, signs of nausea, vomiting, or changes in stool such as diarrhea or even melena.
Because prey species often mask signs of illness, disease may be quite advanced by the time a rabbit or rodent is presented for care. Emergency medicine and critical care techniques are often required; however, treatment can only be as aggressive as patient personality will allow. Stress can play an important role in clinical outcome and therefore every effort should be made to minimize patient stress.