Abstract

Small mammals pose a challenge for veterinarians. In the treatment of these animals, new, innovative methods need to be employed in order to obtain the same quality workup as with larger, relatively more manageable animals. This review will offer several different methods in the handling and medical management of these creatures.

Introduction

Small exotic mammals are inherently challenging to work with because of the difficulty in safe handling and the low demand for tools designed to work with little species. The techniques and tools presented in this paper are intended to facilitate their medical care. Suppliers and manufacturers of products mentioned in this review are presented in Table 1.

Restraint

Gas anesthesia is often the best method for safe handling of small mammals. Induction chambers can be fashioned from large dog masks, acrylic boxes, or plastic bags. Several commercial chambers are available (Braintree, Stoelting) as well as small face masks (AM Bickford, MDS Matrx). Preparing face masks is possible by modifying syringe cases and small plastic bottles to fit at the end of anesthetic tubing; latex gloves can be placed across the face end as a seal. Endotracheal tubes (ET) tubes as small as 1 mm can be purchased (VSP); alternately, you can use red rubber catheters and IV catheters that can be attached to anesthetic non-rebreathing tubing. A penlite laryngoscope (Dr. G’s Unique Products) increases visibility in small oral cavities.

Manual restraint may be facilitated by laboratory animal products such as semicylindrical plastic restrainers for rodents (Braintree) which allow for observation and safe needle injections (IP, IV-tail). Plastic cake decorating bags can also be used for restraint, with the animal’s head placed at the tip.

Monitoring Equipment

• ECG monitors are available that read 10-999 BPM (Bioanalytical Systems). Needles can be used in lieu of clips, or gauze can be placed between clips to reduce tissue trauma. Doppler machine probes can be taped in place over the heart or vessels for audible heart beats.
• Pulse oximetry machines have various sized attachments that can wrap around a tail or foot; some small (1×1×0.3 cm) probes can be placed on the underside of a tail or other vascular surface (Nonin).
• A feline respiratory tidal volume monitor is available that attaches to an ET tube (Medical Engineering and Development, Inc.). A ventilator is available for small, intubated animals up to 10 kg (Vetronics by Bioanalytical Systems).

Physical Examination

Ocular head gear (MDS, Inc., Opticaid by Edroy, Orascoptic Research) increases magnification and provides appropriate light for good visualization of small anatomic features.

• Ocular exam: a handheld slit lamp (Eidolon) can be employed to visualize adnexa, a 26 mm lens (Volk) and transilluminator allow full fundic exams in the dilated patient. Ultrasound 10 MHz probes can be used on animals as small as 60 g.
• Aural: limited by the diameter of otoscope specula, 2 mm is the smallest available (Welch Allyn), or you can use a rigid endoscope (1.8 mm, Storz).
• Oral: items that assist opening the mouth include metal specula (Petiatric Supply Co.), mini rubber spatulas, radiograph film, guitar picks, rigid ID cards, pediatric/infant nasal specula (Spectrum), and non-slip cylindrical specula (Max Associates). Cotton-tipped applicators act as a great extension of your fingers; use an otoscope or rigid endoscope to increase visibility.

Diagnostic Sampling

• Blood: Venipuncture sites include jugular, cephalic, saphenous, femoral, tail, ear, and orbital sinus (some rodents). Collection method is as follows: (a) use a heparinized 0.5-ml insulin syringe (28-ga needle) or (b) insert a hubbed needle (25–28 ga) into the vessel and when a flash is seen, use a capillary tube to obtain the sample. There is a small centrifuge available that spins 10 µl HCT tubes (StatSpin, Inc.). A whole blood volume of 20 µl is enough for a CBC; 250 µl can give you about 20 serum chemistry tests (dependent on PCV) on most standard machines. A smear and a PCV tube get you a lot of valuable information. For immediate results on small volumes of blood, the i-Stat system (Heska) will run whole blood; three drops (∼60 µl ) will provide a mini-chemistry panel. Blood can be collected in 750 µl microtainers (Becton Dickinson).
• Tissue: Fine-needle aspiration using a 25 ga needle can achieve a good diagnostic sample. Punch biopsy tools are made as small as 2 mm (Fray). Endoscopic biopsy instruments as small as 3 Fr (1.8 mm trochar) are available (Storz). Touch preparations can be performed on any lesion on any size animal. After placement of an IO catheter, a bone marrow sample can often be obtained.
• Other: For a tracheal wash or rectal wash, use a 24–27 ga intravenous catheter. For gastric washes, a red rubber tube as small as 5 Fr micro-Culturettes (Becton Dickinson) is good for bacterial sampling of dental socket, rectums, etc. Nasolacrimal duct cannulas for nasal flushes are available in 21 and 23 ga sizes (Jorgenson Labs).

Diagnostic Imaging

• Radiographs: Radiographs without manual restraint can be accomplished using plastic boxes, bowls, plastic bags, and small cloth bags. If the patient is several inches away from the plate, magnification will occur. Mammography units provide excellent detail, but detail plates and dental radiographs are sufficient. Standing lateral films can be accomplished by placing an animal on a plastic box while supporting a film directly behind the animal. To shoot through a plastic kennel/crate, increase the kVP. In the anesthetized patient, use masking tape for positioning or boards fashioned with Velcro tape. For positioning, a 40×60 cm vacuum positioner is available (Hug-U-Vac).
• Ultrasound: 7.5 MHz probes can be used on many animals, although 10 MHz and even 16 MHz vascular probes are available (Neurosoft, Inc.). Stand-off pads (Aquaflex from Parker; ATS) facilitate the use of larger probes in small animals. Alternately, a thick gel layer and light pressure or a plastic bag filled with gel can be used as a makeshift stand-off pad.

Treatment Administration

• Oral: Tube feed with or without a speculum using an intravenous catheter, a steel gavage tube (smallest size is 24 ga) (Petiatric Supply, ACES, Braintree), a red rubber tube (5–10 Fr), or a tomcat catheter. Food items that can pass through most of these feeding tubes include A/D diet (Hill’s Science Diet), Herbivore Critical Care diet (OxBow Pet Products), baby food, Nutrical (ESCVO), ground insectivore diet (Reliable Protein Products), and CliniCare (Abbott). A coffee grinder, food processor, or blender can be used to grind dry pellets of any kind, for later mixture with water.
• Oral medications: suspensions of antibiotics can be obtained from many compounding pharmacies or can be made by mixing crushed tablets or capsules with a 1:9 mixture of KY jelly:water. Flavor additives (extracts and sugar-free drink mixes) may be added to increase palatability. Children’s formulations work well in many cases for palatability. Medicated gelatin may be made by following package instructions and adding oral medications (calculated by mg/ml gelatin); pureeing food items into gelatin can increase palatability.
• Topical: (a) Orabase (ConvaTec) can be mixed with ophthalmic ointments, which is great for mucosal surfaces; (b) ophthalmic solutions can be dropped onto wounds or lesions; and (c) Bag Balm (Dairy Association) and Preparation H can be used on non-ulcerated inflammation of soft tissue. Tuf-foot (Bonaseptic) has shown some efficacy in treating pododermatitis in rodents.
• Intravascular/intraosseous: Treatment can be facilitated using syringe pumps that can administer volumes as low as 0.01 ml/min (Braintree, Yale).
• Intralesional: Antibiotic impregnated methyl methacrylate beads can be made in any size.³

Surgery

• Instruments/materials:
  • A surgical tray is available for animals 300–2000 g with plastic bands for maintaining body position (Lone Star Medical Products, Inc). An operating board (Deltaphase by Braintree) maintains body temperature via special pads and has an 8×8 inch (20×20 cm) operating surface with instrument holding areas.
  • Surgical packs should include a microblade and handle, Stevens tenotomy scissors, Castroviejo or Derf needle holders, wire speculum, chalazion forceps, Bishop Harmon forceps (Spectrum, Braintree), cotton tip applicators, and small gauze.
  • Dental equipment (Jorgenson Laboratories, Spectrum) is available for medium-size rodents.¹ Two mm elevators (feline or microelevators) are available separately (Peerless International Inc., Spectrum). Small feline mouth gags or a 1 ml or 0.5 ml syringe can be cut and used as a mouth gag by placing the canines in either end.
  • Rigid endoscopes are available now as small as 1.9 mm telescope diameter with biopsy tools as small as 3 Fr (Storz).
  • Surgical preparation: Use moustache clippers to shave a small surgical area. Clear drapes allow full visualization of your patient during surgery (Veterinary Specialty Products) or use store bought oven bags.⁵
  • Closure: suture material 5–0 to 9–0 (Ethicon), tissue glue, and stainless steel suture.
• Hemostasis: Cotton swabs will hold off a bleeding vessel until you can permanently control the bleeding. Mechanical cautery can be accomplished using small 4 mm hemoclips (Weck) or standard ligation. Chemical cautery can include silver nitrate sticks or Monsel’s salts (ferrous sulfate powder). Clotting enhancers include Gelfoam (Pharmacia and Upjohn) and Clotisol (Benepet). Electric cautery using a handheld cautery pen can be handy (Petiatric Supply Co.). Radiosurgery units producing 3.8 MHz have less lateral heat and can be used on animals as small as rodents (Ellman).
• Hypothermia: A 250 ml fluid bag microwaved for 30–45 seconds and wrapped in a towel serves as a warm waterbed. Heated exam tables are helpful. Heating pads should be made with heated water coils to prevent burns. Pediatric quilts are available which blow warm air on the patient (Bair Hugger by Gaymar/Augustine).⁴ Isothermal reusable pads are available (Deltaphase by Braintree) which maintain 39°C for six hours via a chemical solution which is solid at room temperature and becomes fluid when heated.
• Fracture repair: Intramedullary pins can be made using cerclage wire, stylets from spinal needles or catheters, and needles. Splints can be made from sturdy bandage tape, toothpicks, paper clips, Vet-O-Plast (Orfit), syringes, or straws² with methyl methacrylate or epoxy in aquarium tubing or red rubber catheters.
• Wound treatment:
  • Sealants: tissue glue, Nu-Skin (available at pharmacies), surgical drape, and No-Sting Barrier film (3M Animal Care Products).
  • Granulation enhancers: BioSyst (Cook), IAMIN-vet (Procyte), Carravet (Veterinary Product Labs), Silvadene, or Granulex (Bertek).
  • Bandage material: VetRap precut into 0.6 cm pieces, Tegaderm, band aids.

Critical Care

Incubators/critical care chambers are available in many sizes with a variety of accessories (Petiatric Supply, Thermocare, HotSpot for Birds). Most critical care systems have nebulizer attachments available from the company. A 10-gallon aquarium can be modified with an ‘Aquatop’ which has a 17.5×20 cm access door and controls temperature and humidity (Petiatric Supply).

Summary

Small mammals can be successfully managed medically by stocking a few specialty items and modifying existing supplies into workable equipment for patients <500 g. The product manufacturers listed can provide further ideas for small patient management.

Acknowledgments

Special thanks to Joel Pond, CVT, and Julie Lemon, CVT, for their diligence and creativity when working with small animals.

Table 1. Product suppliers and manufacturers

Abbott Laboratories, Abbott Park, IL, www.abbott.com/animal_health/animal_health.html.
ACES (Animal Care Equipment and Services, Inc.), Crestline, CA; (800) 338-ACES (2237); www.animal-care.com/010.htm.
A.M. Bickford, Wales Center, NY; (800) 795-3062; www.ambickford.com.
ATS Laboratories, Inc., Bridgeport, CT; (203) 579-2700; www.atslabs.com/Contact%20Us%20ATS%20Laboratories.htm.
Augustine Medical, Inc., Eden Prairie, MN; (800) 800-4346; www.bairhugger.com.
Becton Dickinson, Franklin Lakes, NJ; (201) 847-6800; www.bd.com.
Benepet Pet Care Products, St. Joseph, MO; (816) 279-3449; (800) 825-0341.
Bertek Pharmaceuticals, Morgantown, WV; (304) 285-6420; www.bertek.com.
Bioanalytical Systems, Inc.,West Lafayette, IN; (765) 463-4527; (800) 845- 4246; www.bioanalytical.com/vetronics/cardio.htm#test.
Biopure, Cambridge, MA; (617) 234-6822; (888) 337-0929; www.biopure.com.
Bonaseptic Company, Atlanta, GA; (888) TUF-FOOT; www.tuffoot.com/about.htm.
Braintree Scientific, Inc.; (781) 843-2202; www.braintreesci.com.
CeramOptec Industries Inc., Biolitec Inc., East Longmeadow, MA; (413) 525-0600; www.ceramoptec.de/.
ConvaTec, Professional Services, Princeton, NJ; (800) 422-8811; www.convatec.com/en_US/contact/index.html.
Cook Veterinary Products, Bloomington, IN; (800) 826-2380; www.cookgroup.com.
Dairy Association Co, Inc.; Lyndonville, VT; (800) 232-3610; www.bagbalm.com/page5.htm.
Dr. G’s Unique Products; Avian Medical Center, Chantilly, VA; (800)478-0355; www.avianmedicalcenter.com/products.
Edroy Products Co., Nyack, NY; (914) 358-6600.Eidolon Corp, Natrick, MA; (800) 651-0015; www.slitlamp.com.
Ethicon, 1-800-862-2422; www.ethiconinc.com.
EVSCO Pharmaceuticals, Buena, NJ; (800) 225-0270, (856) 691-2411, ext 265; www.evscopharm.com/pages/nutrtion.html.
Fray Products Corp., Buffalo, NY; (800) 288-6580, (716) 837-2461; www.frayproducts.com/email.html.
Gaymar industries, Inc., Orchard Park, NY; (800) 828-7341; www.gaymar.com.
Heska Corporation; (800) 464-3752; www.heska.com/heskateam/product_catalog.asp.
HotSpot for Birds, Northridge, CA; (323) 851-1878, (888) 246-8776; hotspot@multiscope.com.
Hug-U-Vac (Sports Doc Emergency Response Systems), Salem, OR; (503) 364-4340; huguvac@aol.com.
Jorgenson Laboratories, Loveland, CO; (800) 525-5614; www.jorvet.com; info@jorvet.com.
Lone Star Medical Products, Inc., Houston, TX; (713) 796-0505, (800) 331-7427; www.lsmp.com/html/veterinary.html.
Max Associates; (301) 776-8824; maxassociates@erols.com.
MDS (Medical Diagnostics Services, Inc), Brandon, FL; (813) 653-1180.
MDS Matrx, (800) 847-1000, (716)716-662-6650; www.matrxmedical.com.
Medical Engineering and Development Inc., Jackson, MI; (517) 789-9060, (800) 784-9060; www.med-engrg.com.
Neurosoft, Inc., Sterling, VA, USA; (703) 904 9600; www.neuro.com/medsys/DWLtech2.htm.
Nonin Medical Inc., Plymouth, MN; (800) 356 8874; www.nonin.com.
Orascoptic Research; (800) 369-3698; (608) 831-2555; www.orascoptic.com/.
Orfit Industries n. v., Wijnegem-Belgium; (+32).3.326.20.26; www.orfit.be/.
Oxbow Pet Products, Murdock, NE; (800) 249-0366; www.oxbowhay.com.
Parker Laboratories, Inc.; Fairfield, NJ; (973) 276-9500, (800) 631-8888; www.parkerlabs.com/us4.htm.
Petiatric Supply Co., Wichita, KS; (316) 831-9500; www.petiatric.com.
Pharmacia and Upjohn, Peapack, NJ; (908) 901-8000, (888) 768-5501; www.pharmacia.com.
ProCyte Corporation, Redmond, WA; (425) 869-1239; www.procyte.com.
Reliable Protein Products, Palm Desert, CA; (760) 321-7533; www.zoofood.com/insectivore.shtm.
Spectrum, Stow, OH; (800) 444-5644; custserv@spectrumsurgical.com, www.spectrumsurgical.com.
StatSpin, Inc, Norwood, MA; (781) 551-0100, (800) STATSPIN; www.statspin.com/index.html.
Stoelting Co., Wood Dale, IL; (630) 860-9700.
Storz (Karl Storz Veterinary Endoscopy), Goleta, CA; (800) 955-7832; www.karlstorzvet.com.
ThermoCare Inc, Incline Village, NV; (800) 262-4020.
Volk; (800) 345-8655; www.volk.com.
Veterinary Products Laboratories, Phoenix, AZ; (888) 241-9545.
VSP (Veterinary Specialty Products), Boca Raton, FL; (561) 362-7340, (800) 362 8138; www.vet-products.com.
Welch Allyn, (800) 535-6663; www.welchallyn.com/misc/search/country.asp.
Weck Closure Systems, Research Triangle Park, NC; (800) 234-9325; www.weckclosure.com/products/7_1_5.html.
Yale Apparatus, (516) 221-0059; www.syringepump.com.

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