Ferret-evaluating And Stabilizing The Critical Ferret

V CE

Vol. 22, No. 5 May 2000

Refereed Peer Review

FOCAL POINT ★Ferrets have a number of diseases that require prompt recognition; familiarity with specific diagnostic and therapeutic techniques is necessary to ensure adequate critical care.

KEY FACTS ■ Ferret phlebotomy is most easily achieved using the jugular vein or cranial vena cava. ■ Thoracic radiography is a crucial diagnostic tool for evaluating ferrets that are weak, coughing, lethargic, and/or dyspneic. ■ The urethral opening of male ferrets is located on the ventral aspect of the penis several millimeters proximal to the glans. ■ When placing intravenous catheters, prepuncturing the skin is often recommended. ■ Intraosseous catheters in the tibia or femur are useful in ferrets, particularly small animals where intravenous access may be difficult to achieve.

Evaluating and Stabilizing the Critical Ferret:

Basic Diagnostic and Therapeutic Techniques* University of California, Davis

Indianapolis Zoo, Indianapolis, Indiana

Keith G. Benson, DVM

Jan C. Ramer, DVM

University of Wisconsin

Joanne Paul-Murphy, DVM ABSTRACT: Understanding the differences and similarities between ferrets and other domestic carnivores facilitates rapid acquisition of diagnostics as well as administration of life-saving measures. Restraint, phlebotomy, and tracheal wash techniques vary from those traditionally used in small animal medicine. Interpretation of radiographs and diagnostic ultrasonography requires familiarity with normal ferret anatomy. Furthermore, intravenous and intraosseous catheterization, urethral catheterization, fluid therapy, and nutritional support all have ferretspecific caveats; appreciation of these differences can ensure that ferrets receive high-quality care in a timely fashion.

D

omestic ferrets represent a healthy portion of small animal patient loads. Therefore, veterinarians must not only provide ferret owners with preventive care for their pets but also be able to deliver quality emergency care. This article describes some common diagnostic and therapeutic techniques used in emergency medicine, with focus on how the methodologies are adapted to the specific requirements of domestic ferrets.

RESTRAINT Most ferrets are amenable to simple, gentle, manual restraint. However, ferrets that are highly mobile or fractious or are in pain may require special handling to successfully restrain them. One technique involves grasping the ferret’s skin on the scruff of its neck and lifting all four limbs off the table; most ferrets immedi*A companion article entitled “Evaluating and Stabilizing the Critical Ferret: Initial Assessment, Differential Diagnosis, and Diagnostic Plan” appeared in the March 2000 issue (Vol. 22, No. 3) of Compendium.

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TABLE I Chemical Restraint Agents for Domestic Ferrets Protocol Acepromazine Isoflurane

Dose and Route of Administration 29

Ketamine–medetomidine Tiletamine–zolazepam

0.1–0.3 mg/kg IM 2% to 3% in O2 1 L/min, 3% to 3.5% in O2 induction, 0.5% to 2.5% in O2 maintenance 10–20 mg /kg8 IM, short duration; 30–60 mg/kg8 IM 1 mg/kg8 SC, IM 10–20 mg/kg ketamine,1–2 mg/kg diazepam7 IM; 25–35 mg/kg ketamine, 2–3 mg/kg diazepam30 IM 20–30 mg/kg ketamine, 0.2 mg/kg midazolam IM 10–30 mg/kg ketamine, 0.05–0.3 mg/kg acepromazine29 SC, IM 25 mg/kg ketamine, 2 mg/kg xylazine31 IM; 30 mg/kg ketamine, 0.3 mg/kg xylazine31 IM 5 mg/kg ketamine, 0.08 mg/kg medetomidine32 IM 12–22 mg/kg each33 IM

Reversal Agents Yohimbine Atipamazole Naloxone

0.5 mg/kg8 IM 0.4 mg/kg32 IM 0.04–0.1 mg/kg8 SC, IM, IC

Ketamine Xylazine Ketamine–diazepam Ketamine–midazolam Ketamine–acepromazine Ketamine–xylazine

IC = intracardiac; IM = intramuscularly; O2 = oxygen; SC = subcutaneously.

ately cease struggling when held in this position. Another approach is to place the ferret in dorsal recumbency, using one hand to hold the scruff of its neck and the other hand to hold its pelvic limbs and pelvis and then straightening the ferret’s body. In addition to physically restraining fractious ferrets, offering them a small amount of preferred pet food (Prescription Diet® a/d; Hill’s Pet Nutrition, Topeka, KS), Nutrical® (Evsco Pharmaceuticals, Buena Vista, NJ), or chicken baby food on a tongue depressor (held rostral to the nose) often distracts the animal during certain procedures, such as jugular or cranial vena caval venipuncture. Various chemical restraint protocols (Table I) can also be used for domestic ferrets. Isoflurane and a ketamine–benzodiazepine combination are the most common anesthetics used. Advantages of using sedation must be weighed against the potential complications that can occur in compromised patients. The rapid induction, recovery, and controlled depth of anesthesia make isoflurane an excellent choice for many critically ill ferrets. Inhalation anesthetics should be administered to ferrets using a nonrebreathing system. Because isoflurane reduces the number of circulating erythrocytes via splenic sequestration in ferrets, this agent should be used with caution in severely anemic animals.1–3 Isoflurane administration to domestic ferrets is associated with substantial decreases in arterial blood pressure. At 1.0 minimum alveolar concentration, the

mean arterial pressure of ferrets is less than 60 mm Hg. Thus the degree of hypotension is dose related.4

DIAGNOSTICS Phlebotomy Because ferrets have small superficial vessels and tough skin, phlebotomy becomes more challenging than it is in other companion animals. In ferrets, phlebotomy sites include the cephalic vein, lateral saphenous vein, femoral vein, jugular vein, cranial vena cava, and ventral tail artery.5–7 Small (0.1- to 0.3-ml) samples of blood can be withdrawn from the cephalic or lateral saphenous vein similar to the same procedure used in dogs and cats. Small needles (25 to 30 gauge) and syringes (0.5 to 1.0 ml) are recommended for these sites. Because withdrawing samples from the cephalic vein likely precludes subsequent catheterization of the vessel, veterinarians should consider whether the cephalic vein may be needed to administer fluids or medication. Withdrawing blood from the jugular vein is more common for larger sample volumes. The jugular vein has a narrow diameter and is superficial. This vein can be easily traversed when inserting a needle; thus bending it at an angle of 20˚ to 30˚ can facilitate venipuncture. Blood can also be collected from the cranial vena cava; fractious ferrets may require general anesthesia. A 1-inch, 22-gauge needle on a 3- or 5-ml syringe should be used to collect blood from this vessel. The ferret

CHEMICAL RESTRAINT ■ ISOFLURANE ■ BLOOD COLLECTION

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Figure 1B Figure 1—(A) Lateral and

(B) ventrodorsal radiographs showing the normal ferret thorax.

should be restrained in dorsal recumbency with its neck extended. The notch between the manubrium and first rib should be palpated—this is the site of entry for the needle. The needle should Figure 1A be angled approximately 10˚ from the horizontal plane and directed toward the contralateral coxofemoral joint. Slight negative pressure should be applied to the syringe and the needle advanced slowly until blood begins to flow. After the sample has been withdrawn, some veterinarians opt to apply direct pressure at the notch of the manubrium and first rib.

Tracheal Wash Because ferrets have a small-diameter trachea, the transglottal approach should be used for tracheal washes. Ferrets should be anesthetized and intubated using a sterile 2.5- to 4-mm diameter endotracheal tube.8 A sterile 3.5-Fr red rubber or polypropylene catheter should be advanced through the endotracheal tube to the level of the third to sixth intercostal space. From 2 to 3 ml of sterile 0.9% sodium chloride or lactated Ringer’s solution should be injected into the catheter and the fluid immediately withdrawn while the thorax is coupaged. The sample should be submitted for cytologic and microbiologic evaluations. If practitioners suspect systemic mycosis, fungal cultures should be specifically requested. Radiography Thoracic radiography is a crucial diagnostic tool for evaluating ferrets that are weak, coughing, lethargic, and/or dyspneic. The presence of thoracic effusions,

pulmonary edema, pulmonary infiltrates, and soft tissue masses can be determined from standard radiographic views of the thorax. The status, size, and shape of the heart, however, can be difficult to evaluate. The cardiac silhouette of ferrets is naturally globoid (Figure 1) and thus cannot be scrutinized with the same criteria used to judge canine and feline hearts.9 A contrast esophagram may be helpful to confirm a diagnosis of megaesophagus.10 Abdominal radiography can identify accumulations of fluid, organomegaly, space-occupying masses, and gastrointestinal foreign bodies. The intestine of normal ferrets should not contain intraluminal gas. Splenomegaly is a common, nonspecific finding in older ferrets because the splenic size gradually increases with age. The causes of splenomegaly include neoplasia, anemia, sepsis, chronic illness, and extramedullary hematopoiesis.11 Whereas 5% of ferrets with splenomegaly have splenic disease, most have extramedullary hematopoiesis and/or congestion.12 Plain radiography and contrast studies of the urinary tract can help veterinarians evaluate markedly enlarged prostates, cystic and urethral calculi, cystic kidneys, and bladder cysts.13

Ultrasonography Cardiac Ferrets in cardiac failure require minimal restraint for echocardiography. However, ferrets that are not in cardiac failure may be too fractious for thorough evaluation without anesthesia; isoflurane administered in oxygen via facemask is a safe and effective restraint method. Two-dimensional echocardiography should be used to measure chamber size, wall thickness, and shortening fraction and assess valvular function. Pleural effusions and masses in the cranial mediastinum are best evaluated using thoracic ultrasound imaging. Echocardiographic values for ferrets have been reported.12 Abdominal Ferrets are excellent subjects for abdominal ultrasonography because they usually can be manually restrained for the procedure. Linear-array probes are ideal, and a frequency of 7.5 MHz is recommended. The abdominal cavity can be evaluated for effusion, size, and architecture of the liver, spleen, adrenal glands, intestinal tract, regional lymph nodes, reproductive tract (prostate in male

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ferrets; ovaries, ovarian remnants, obtained, they may be hanuterus in intact jills), and pandled and analyzed as they are creas. The normal adrenal size in dogs and cats. in ferrets is 2 to 3 mm wide × Veterinarians are cautioned 8 to 10 mm long.13 Color flow to avoid overzealous flushing Doppler technology can be of IV or IO catheters with used to detect impingement of heparinized saline. Studies in an enlarged adrenal gland on humans have demonstrated the vena cava by measuring an little benefit in flushing catheincreased velocity of blood ters with heparinized saline, flow at that point. The normal and the potential for heparin mesenteric lymph node meaoverdose in ferrets is substansures 10 to 15.2 mm × 5.6 to Figure 2—Illustration depicting the correct placement of tial.20 We prefer to reserve heparinized saline flushes for in9.6 mm.15 Ultrasonography- an intraosseous catheter in the femur of a ferret. guided biopsy or fine-needle stances where catheters are being aspiration of the lymph nodes maintained without material can be performed with the flowing through them for 6 same techniques as those used hours or more. If heparinized in dogs and cats. saline is required for a heparin lock, only the volume THERAPEUTICS needed to fill the catheter itIntravenous self should be used. To avoid Catheterization injecting heparin into the aniBecause the skin of ferrets mal, this material should be is tough, prepuncturing it uswithdrawn before anything is ing a 20-gauge needle before administered by catheter. the catheter is placed can pre© 2000 R. Peterson Urethral Catheterization vent the catheter from becoming crimped along the Figure 3—Illustration depicting urethral catheterization of of Male Ferrets a male ferret. Catheterization of male ferstylet. All rubber connections rets has been described in the and injection ports should be literature.21 The distal aspect of the os penis should be covered with bandage material to prevent ferrets from hooked with the flexure curving dorsally. Because the urechewing and ingesting any rubber. thral opening is proximal to the hooked end and laying on Cephalic and saphenous catheters are well tolerated the ventral surface of the glans, it can be difficult to visualby ferrets. Jugular catheters are not well tolerated by ize (Figure 3). The use of magnifying loupes can thus be alert ferrets but have been used with success in dehelpful during the procedure. The small size of the urepressed patients.1,8,16 If intravenous (IV) catheterization is difficult or impractical (e.g., in ferrets with hypotenthral opening makes catheterization challenging, and a sion, small ferrets), intraosseous (IO) catheterization of well-lubricated 22- or 24-gauge IVcatheter may be needed the femur is a rapid, effective alternative.17 At the head to initially flush the urethra. Some male ferrets are large of the femur, an area measuring 2 × 2 inches should be enough to allow passage of a 3.5-Fr red rubber catheter. clipped and aseptically prepared. We prefer using a loThe use of an IV catheter guide wire or sterile guitar string cal anesthetic at the site and within the periosteum to within the lumen of the catheter facilitates passage around minimize discomfort; however, general anesthesia may the ischial arch.16 Because the urethra of male ferrets is long and acutely curved at the ischial arch, tomcat be required. A small incision should be made using a catheters are not appropriate because the stiffness of the No. 15 blade or 20-gauge needle. A 1.5-inch, 22-gauge material may lead to mucosal damage. A soft, 3.0-Fr urispinal needle should then be advanced medial to the nary catheter designed specifically for use in ferrets is also greater trochanter, in the trochanteric fossa, through available (Cook Veterinary Products, Bloomington, IA). the cortex, and into the medullary space (Figure 2). Male ferrets with severe dehydration or hyperkalemia Care must be taken not to pass through the greater require minimal restraint; generally, most ferrets must be trochanter and into the periosteal space along the distal sedated or anesthetized to safely manipulate genital tissue. femur. This technique can be used to obtain bone marWith the ferret in dorsal recumbency, the penis should be row samples for analysis.18,19 After samples have been TYPES OF CATHETERS ■ HEPARINIZED SALINE ■ MAGNIFYING LOUPES

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Fluid Composition Isotonic crystalloid solutions are the most Drug Dose and Route of Administration common fluids administered to ferrets. Lactated Aspirin 0.5–22 mg/kg30 PO Buprenorphine 0.01–0.03 mg/kg1 SC, IM, IV; 0.01 mg/kg8 SC, IM Ringer’s solution and Butorphanol 0.1–0.25 mg/kg34 SC, IM, IV; 0.05–0.1 mg/kg8 SC, IM 0.9% sodium chloride Carprofen 2.2 mg/kg every 12 hours PO are acceptable choices for Fentanyl citrate 0.2 ml/kg8 IM volume expansion. FerPhenylbutazone 100 mg/kg8 PO rets with hypoalbuminemia (serum albumin less IM = intramuscularly; IV = intravenously; PO = orally; SC = subcutaneously. than 2.0) may benefit from administration of gently exposed by pushing against the base of the os penis colloid solutions (e.g., hetastarch, dextrans). There are no while retracting the prepuce. In male ferrets with urinary published guidelines for administering colloids to ferrets; calculi or urethrospasm, open-ended catheters are often we recommend following guidelines developed for colloid easier to pass than are catheters with side ports. The open administration in cats. Hypoglycemic ferrets can benefit end allows retrograde flushing and distention of the urefrom the addition of dextrose to these solutions, and thra. Administration of IV diazepam or addition of dilute potassium supplementation in ferrets with hypokalemia lidocaine to the flush may help relax the urethra. The can be administered according to feline protocols.22 catheter should be advanced into the bladder. At this point, practitioners can (1) collect a urine sample, (2) Nutritional Support flush the bladder with sterile isotonic fluid (e.g., lactated Critically ill ferrets are frequently anorectic. In most Ringer’s solution, 0.9% sodium chloride), or (3) instill a ferrets, forced alimentation is possible with simple syradiopaque contrast medium as part of a diagnostic ringe feedings. Pureed ferret food, poultry baby foods, or study.21 The catheter can be affixed by adding “tape Prescription Diet® a/d (50 ml/kg/day23) are acceptable wings” to the catheter and suturing these to the abdomiand palatable to ferrets. Prescription Diet® a/d is soft nal skin just cranial to the prepuce. Closed drainage sysenough to be administered through a syringe. Percutatems are preferred, but ferrets can easily tangle lines. neous gastrostomy tubes can be used in ferrets as in other carnivores.24 Ferrets may resist abdominal wraps; we have Fluid Therapy found that using minimal bandaging material can lower Subcutaneous the animal’s distress level. Ferrets have a particular affiniSubcutaneous fluid administration is commonly used ty for chewing rubber items, including pezzer-type and quite helpful. An effective method that can be accatheters; thus care must be taken to protect the tube at complished by one staff member is to scruff the skin beall times. We use a small circumferential wrap that is aptween the shoulder blades and deposit fluid using a butproximately 3 inches wide and find this approach superiterfly catheter. Subcutaneous fluids are not indicated in or to applying a stockinet jacket or full abdominal wrap. ferrets with severe dehydration or in shock and should be reserved for ferrets with mild dehydration or for mainteAnalgesia nance after the hydration status has been normalized. Several analgesics, including butorphanol and buprenorphine (Table II), are appropriate for use in ferIntravenous and Intraosseous rets. The degree of sedation is lower with buprenorThe rate of fluid administration in ferrets is higher phine than with butorphanol. As with other species, than that administered to larger companion animals; veterinarians should be careful with NSAID adminisprecise rates for ferrets have not been determined, but tration in dehydrated patients and patients with preex75 to 100 ml/kg/day is commonly administered.16 Fluisting gastric mucosal disease (e.g., helicobacteriosis), id deficits should be corrected within 24 to 36 hours. coagulation disorders, or renal disease. Serum electrolyte levels should be monitored in patients receiving large volumes of fluids throughout the Thoracocentesis course of therapy. Postobstructive diuresis should be In addition to being a diagnostic tool, thoracocenteanticipated in male ferrets being treated for urethral obsis can be a useful therapeutic procedure. By reducing struction. Careful monitoring of body weight, skin turthe volume of pleural effusion, patients can ventilate a gor, urine output, and serum electrolytes is imperative. larger portion of their lungs and thus improve ventilaTABLE II Analgesic Drugs for Ferrets

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tion–perfusion matching and oxygenation of venous blood. Fluid removed during thoracocentesis should be submitted for cytologic and chemical evaluation, and cultures should be submitted if there is evidence of sepsis. The caudal placement of the heart in ferrets (between the sixth and eighth rib) must be considered when attempting this procedure. Ferrets should be lightly sedated or anesthetized with isoflurane. The lateral thorax should be clipped and aseptically prepared; a 21-gauge, 1-inch butterfly catheter and 20-ml syringe with a three-way stopcock should be used. The catheter should be passed approximately one third up the lateral thoracic wall from the sternum between the fourth and fifth or ninth and tenth ribs. The procedure requires two veterinary staff: one to direct the needle while another manipulates the syringe and stopcock.

Protocol for Collecting Blood from Ferret Donors ■ Assemble materials: clippers, cotton balls soaked in povidone–iodine solution and cotton balls soaked in alcohol; 22-gauge, 6-inch butterfly catheter; 12- or 20-ml syringe with 1 ml of acid citrate dextrose for every 6 ml of blood to be harvested. ■ Examine, weigh, and obtain a rectal temperature of the donor, recording values on the donor record sheet. ■ Sedate the donor with either 2% to 3% isoflurane in oxygen or 20 to 35 mg/kg intramuscular ketamine combined with 0.2 mg/kg intramuscular midazolam. ■ With the onset of sedation or anesthesia, apply sterile lubricant to the donor’s eyes. ■ Clip and aseptically prepare the area around the donor’s manubrium and the ventral cervical area. ■ Place the butterfly catheter into the jugular vein or cranial vein cava and slowly draw 5 to 7 ml/kg body weight into the syringe containing the acid citrate dextrose. ■ Remove the catheter, apply 2 minutes of direct pressure onto the site, and observe the donor’s recovery from sedation/anesthesia. ■ Do not harvest whole blood from healthy ferrets more often than every 21 days.

Blood Transfusions Blood transfusions in ferrets have been described in the literature.25 Transfusion should be considered when a patient’s hematocrit has dropped precipitously to 15% or gradually to 12%.16 Veterinarians may choose to transfuse a ferret before the hematocrit reaches these levels, depending on the patient’s clinical signs. Ferrets that are dyspneic or weak may benefit from additional erythrocytes, particularly if blood loss has been acute and there has been insufficient time to compensate for reduced oxygen-carrying capacity. Ferrets with coagulation disorders, jills with hyperestrogenemia and secondary aplastic anemia, and ferrets with substantial intraoperative hemorrhage are examples of candidates for whole blood transfusion. Ferrets lack distinct blood groups, thereby simplifying selection of blood donors.26 Ferrets can safely donate 5% to 7% of their blood volume (equivalent of 5 to 7 ml/kg body weight).25 Although there is no standard recommendation for the volume of whole blood to be delivered to ferrets, most authors suggest using canine or feline parameters.25,27 We recommend the following formula (PCV = packed cell volume)22: Blood Volume Donor (ml) = Blood Volume Recipient (ml) × Post PCV – Pre PCV Donor PCV Efficiency is important when collecting blood from ferret donors (see Protocol for Collecting Blood from Ferret Donors) because isoflurane anesthesia can reduce

the PCV of ferrets.3 Blood should be administered by very slow bolus or using a syringe pump shortly after the blood has been harvested from the donor. Whole blood should be passed through a filter to avoid inadvertently delivering thrombi to the patient. Although transfusion reactions have not been reported in ferrets, they should be monitored for hypotension, fever, urticaria, hemolysis, and emesis.22

Endotracheal Intubation The small oral cavity and caudal placement of the glottis in ferrets (Figure 4) make endotracheal intubation challenging. It is important for veterinarians to use a small-blade laryngoscope, such as a 2.5- to 4-mm endotracheal tube with stylet. The tongue should be manually retracted in a rostral direction and ventrally deflected, using the laryngoscope to reveal the glottis. Because the ostium generally cannot be visualized, the epiglottis should be depressed using the tube to allow airway visualization. If this approach is not possible, practitioners can occasionally deflect the tube off the caudal aspect of the soft palate, thereby positioning the tube down into the airway. To minimize laryngospasm, topical anesthetic agents can

BLOOD COLLECTION PROTOCOL ■ DONOR SELECTION ■ TRANSFUSION REACTIONS

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Figure 4—The normal ferret glottis.

be applied by swabbing the area using a cotton-tipped applicator saturated with 1% lidocaine solution or using sterile lidocaine gel.1 Application of benzocaine-containing sprays has been associated with methemoglobinemia in ferrets and thus is not recommended.28

Bandaging Ferrets have short, flexible limbs that decrease in diameter distally and offer few bony projections on which to anchor bandaging. The use of stirrups and Elastikon® (Johnson & Johnson, Arlington, TX), a highly adhesive material, can be helpful. Elastikon® can be gently warmed in a microwave to improve adhesive properties, making it more difficult for ferrets to remove. Because most bandage materials are too wide to be effective on ferrets, they must be cut into narrow (5 to 10 mm) strips. Occasionally, it may become necessary to lightly sedate a ferret to prevent it from chewing the bandage. SUMMARY Critically ill ferrets present veterinarians with some unique challenges because of their small body size and conformation. By devoting attention to some speciesspecific recommendations and requirements, veterinarians can effectively treat ferrets requiring emergency medicine. REFERENCES 1. Heard DJ: Principles and techniques of anesthesia and analgesia for exotic practice. Vet Clin North Am Small Anim Pract 23:1301–1327, 1993. 2. Marini RP, Callahan RJ, Jackson LR, et al: Distribution of technetium 99m-labeled red blood cells during isoflurane

anesthesia in ferrets. Am J Vet Res 58:781–785, 1997. 3. Marini RP, Jackson LR, Esteves MI, et al: Effect of isoflurane on hematologic variable in ferrets. Am J Veterinary Res 55: 1479–1483, 1994. 4. Imai A, Steffey EP, Farver TB, Ilkiw JE: Assessment of isoflurane anesthesia in ferrets and rats. Am J Vet Res 60:1579– 1585, 1999. 5. Brown SA: Basic anatomy, physiology and husbandry, in Hillyer EV, Quesenberry KE (eds): Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Philadelphia, WB Saunders Co, 1997, pp 3–13. 6. Bleakly SP: Simple technique for bleeding ferrets (Mustela putorius furo). Lab Anim 14:59–60, 1980. 7. Hillyer EV, Brown SA: Ferrets, in Birchard SJ, Scherding RG (eds): Saunders Manual of Small Animal Practice. Philadelphia, WB Saunders Co, 1994; pp 1317–1344. 8. Marini RP, Fox JG: Anesthesia, surgery, biomethodology, in Fox JG (ed): Biology and Diseases of the Ferret. Baltimore, Williams & Wilkins, 1998, pp 449–484. 9. Stepien RL, Benson KG, Forrest LJ: Radiographic measurement of cardiac size in normal ferrets. Vet Radiol Ultrasound 40:606–610, 1999. 10. Blanco MC, Fox JG, Rosenthal K, et al: Megaesophagus in nine ferrets. JAVMA 205:444–447, 1994. 11. Erdman SE, Li X, Fox JG: Hematopoietic diseases, in Fox JG (ed): Biology and Diseases of the Ferret. Baltimore, Williams & Wilkins, 1998, pp 231–246. 12. Stamoulis ME, Miller MS, Hillyer EV: Cardiovascular diseases, Hillyer EV, Quesenberry KE (eds): Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Philadelphia, WB Saunders Co, 1997, pp 63–76. 13. Fox JG, Pearson RC, Bell JA: Diseases of the genitourinary system, in Fox JG (ed): Biology and Diseases of the Ferret. Baltimore, Williams & Wilkins, 1998 pp 247–272. 14. O’Brien RT, Paul-Murphy J, Dubielzig RR: Ultrasonography of adrenal glands in normal ferrets. Vet Radiol Ultrasound 37:445–448, 1996. 15. Paul-Murphy J, O’Brien RT, Spaeth A, et al: Ultrasonography and fine needle aspirate cytology of the mesenteric lymph node in normal domestic ferrets (Mustela putorius furo). Vet Radiol Ultrasound 40:308–310, 1999. 16. Quesenberry K: Basic approach to veterinary care, in Hillyer EV, Quesenberry KE (eds): Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Philadelphia, WB Saunders Co, 1997, pp 14–25. 17. Anderson NL: Intraosseous fluid therapy in small exotic mammals, in Bonagura JD (ed): Kirk’s Currrent Veterinary Therapy XII. Philadelphia, WB Saunders Co, 1995, pp 1331–1336. 18. Palley LS, Marini RP, Rosenbald WD, Fox JG: A technique for femoral bone marrow collection in the ferret. Lab Anim Sci 40:654–655, 1990. 19. Morrisey JK, Ramer JC: Ferrets: Clinical pathology and sample collection. Vet Clin North Am Exotic Anim Pract 2:553–564, 1999. 20. Stevens LC, Haire WD, Tarantolo S, et al: Normal saline versus heparin slush for maintaining central venous pressure catheter patency during apheresis collection of peripheral blood stem cells. Transfusion Sci 18:187–193, 1997. 21. Marini RP, Esteves MI, Fox JG: A technique for catheterization of the urinary bladder in the ferret. Lab Anim (London) 28:155–157, 1994. 22. Kirk RW, Bistner SI, Ford RB: Clinical procedures, in Kirk RW, Bistner SI, Ford RB (eds): Handbook of Veterinary Procedures and Emergency Treatment. Philadelphia, WB Saunders Co, 1990.

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23. Harrenstien LA: Critical care of ferrets, rabbits, and rodents. Semin Avian Exotic Pet Med:217–226, 1994. 24. Benson K, Carr A, Steinberg S, Paul-Murphy J: Non-endoscopic placement of percutaneous gastrostomy tubes in normal domestic ferrets (Mustela putorius furo). Lab Anim, accepted for publication. 25. Hillyer EV: Blood collection and transfusion in ferrets, in Bonagura JD (ed): Kirk’s Currrent Veterinary Therapy XII. Philadelphia, WB Saunders Co, 1995, pp 1341–1344. 26. Manning DD, Bell JA: Lack of detectable blood groups in domestic ferrets: Implications for transfusion. JAVMA 197: 703–707, 1990. 27. Orcutt CJ: Emergency and critical care of ferrets. Vet Clin North Am Exotic Anim Pract 1:99–126, 1998. 28. Davis JA, Greenfield RE, Brewer TG: Benzocaine-induced methemoglobinemia attributed to topical application of the anesthetic in several laboratory animal species. Am J Vet Res 54:1322–1326, 1993. 29. Mason DE: Anesthesia, analgesia and sedation for small mammals, in Hillyer EV, Quesenberry KE (eds): Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Philadelphia, WB Saunders Co, 1997, pp 378–391. 30. Brown SA: Ferrets, in A Practitioner’s Guide to Rabbits and Ferrets. Lakewood, CO, American Animal Hospital Association, 1993, pp 43–111.

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31. Moreland AF, Glaser C: Evaluation of ketamine, ketaminexylazine and ketamine-diazepam anesthesia in the ferret. Lab Anim Sci 35:287–290, 1985. 32. Ko JCH, Heaton-Jones TG: Anesthetic effects of medetomidine, medetomidine-butorphanol, medetomidine-ketamine, and medetomidine-butorphanol-ketamine in the ferret. Vet Anesth 26:159, 1997. 33. Payton AJ, Pick JR: Evaluation of a combination of tiletamine and zolazepam as an anesthetic for ferrets. Lab Anim Sci 39:243–246, 1989. 34. Brown SA: Ferret drug dosages, in Bauk L, Boyer TH, Brown SA (eds): Exotic Animal Formulary. Lakewood, CO, American Animal Hospital Association, 1995, pp 5–11.

About the Authors Dr. Benson is a resident in Zoological Medicine, School of Veterinary Medicine, University of California, Davis, California. Dr. Ramer is a staff veterinarian at the Indianapolis Zoo, Indianapolis, Indiana. Dr. Paul-Murphy is the chief of service of the Special Species Health Service at the School of Veterinary Medicine, University of Wisconsin, Madison, Wisconsin.