EXOTİC-Evaluating and stabilizing critically Ill Rabbits.Part II

8/14/2019 EXOTC-Evaluating and stabilizing critically Ill Rabbits.Part II

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20TH ANNIVERSARY Vol. 21, No. 2 February 1999

Refereed Peer Review

FOCAL POINT

KEY FACTS

5Critically ill companion rabbitsmust be handled gently in quiet

environments using diagnostic

and therapeutic techniques

designed to provide comfortand reduce the stress of

hospitalization.

Evaluating andStabilizing CriticallyIll RabbitsPart II*University of Wisconsin University of California, Davis

Jan C. Ramer, DVM Keith G. Benson, DVMJoanne Paul-Murphy, DVM

ABSTRACT: Performing diagnostic procedures and stabilizing critically ill rabbits require

knowledge of their general temperament as well as proper restraint, diagnostic, and support-

ive care techniques. Part I of this two-part presentation reviewed recommendations for clinical

assessment, diagnostic differentials, and initial treatment plans. Many techniques used to

manage critically ill dogs and cats can be adapted to minimize stress in critically ill rabbits.

Part II provides general guidelines for handling hospitalized rabbits and describes such diag-

nostic and therapeutic techniques as venipuncture, radiography, fluid therapy, nutritional sup-

port, analgesia, and intubation.

Hospitalized critically ill rabbits need to be housed in a quiet, low-stressenvironment. For example, barking dogs or ferret scent can cause con-siderable stress in critically ill rabbits, thereby making evaluation of

their response to treatment difficult. If a hospitalized rabbit has a companionrabbit at home, it is sometimes comforting for the companion to accompany theill rabbit during the hospital stay.

Urgent care procedures can be accomplished more efficiently when practitio-ners utilize specific supplies and equipment. For example, digital gram scalesmake weighing accurate and quick, and a skid-resistant surface helps the rabbitsfeel more secure on the scale. Small-diameter feeding tubes (3.5 and 5.0 Fr) usedfor nasogastric intubation are also ideal for implementing nutritional support

measures or completing pneumogastrograms. Small endotracheal tubes with andwithout cuffs (2.0- and 2.5-mm outside diameter) should be used for endotra-cheal intubation. Body temperature can be taken quickly with an infrared tym-panic temperature scanner. A stainless-steel nasal speculum or specially madecheek dilators (Henry Schein) can facilitate dental examinations (Figure 1). Fi-nally, low-flow infusion pumps should be used for accurate intravenous or in-traosseous fluid therapy.

Mild sedation is recommended during some diagnostic procedures or if rabbits be-come panicky. Intramuscular or intravenous midazolam (1 to 2 mg/kg) is an excel-lent sedative in rabbits.1 It is fast acting and has shorter duration of action than di-*Part I of this two-part presentation appeared in the January 1999 issue (Vol. 21, No. 1)ofCompendium.

CE

s A few special pieces of

equipment can make urgent

care procedures more efficient.

s Midazolam can reduce anxiety

during stressful procedures.

s Cystocentesis is performed with

the rabbit in dorsal recumbency;

performing cystocentesis through

the lateral abdominal wall is not

recommended.

s Pain management is an important

aspect of rabbit critical care;

buprenorphine and fentanyl

patches are effective.

s Maintaining caloric and fiber

intake is an important aspect of

caring for critically ill rabbits.


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azepam. In addition, injec-tion of midazolam is lesspainful than that of diazepambecause water rather than pro-pylene glycol is the carrier.2

Rabbits in respiratory dis-tress must be stabilized in aquiet oxygen cage before anyprocedures can be performed.

A low flow (1 L/min) of oxy-gen held close to the nose isrecommended during any man-ipulations (including physicalexamination) of dyspneic rab-bits. This method is generallybetter tolerated than using amask.

DIAGNOSTICPROCEDURESRestraint and PhysicalExamination

Unless a rabbit requires im-mediate stabilization, physicalexaminations should begin

with visual evaluation of therabbit in its carrier. As dis-cussed in Part I, general atti-tude, respiratory rate and

character, and fecal and urineoutput and consistency shouldbe assessed in this manner.

A thorough physical exami-nation is best performed on askid-free surface. While therabbit is on the examinationtable, the practitioner shouldmaintain eye contact at alltimes, even if the rabbit is re-cumbent, because a startledrabbit can jump from the

table in seconds. Panicky rab-bits can be wrapped in a towel (Figure 2).Before performing procedures that might cause

stress, practitioners should obtain the respiratory rate,heart rate, and body temperature. Many rabbits toler-ate an infrared tympanic temperature scanner betterthan a rectal thermometer. When placed deep in theear canal, tympanic scanners are quite accurate or

within 1 F or 2F of rectal temperature readings. Be-cause rabbits are very heat sensitive, hyperthermia(temperatures of 106F or higher) is a common emer-gency presentation.

The heart rate of healthyrabbits can range from 130to 325 beats/min (see Nor-mal Physiologic Parametersfor Healthy Rabbits). A Dop-

pler blood flow monitor canbe used on the central auric-ular artery, radial artery, orplantar artery when pulsesare faint. Systolic blood pres-sures are measured indirectlyusing a 1-inch cuff above

where the Doppler monitorwas placed on the limb.

In conscious rabbits, thepinna can be used duringpulse oximetry to monitor

the percentage of availablehemoglobin saturated withoxygen; whereas in de-pressed or sedated rabbits,the probe can be placed onthe tongue or buccal mu-cosa. Thoracic auscultationof harsh, dry respiratorysounds can be caused by re-ferred upper airway noise,even in normal rabbits.Lack of auscultable sounds

over the lung fields may becaused by an area of pul-monary consolidation.

Aspects of the physical ex-amination that may be poor-ly tolerated (e.g., the oralexamination) should bedone at the end of the ex-amination to keep the rab-bit calm as long as possibleor done while the rabbit isunder mild sedation.

RadiographyRadiography is an important diagnostic tool for as-

sessing critically ill rabbits. Sedation can reduce stressand thereby quicken procedure time and improve radio-graphic quality. Highly detailed dental radiography us-ing small dental film in the mouth or for oblique skullpositions requires general anesthesia. Abdominal surveyradiographs can be obtained with an unanesthetized ormildly sedated rabbit resting on the film cassette in ven-tral recumbency. As discussed in Part I, consolidatedmaterial in the stomach is treated medically unless the

Compendium February 1999 20TH ANNIVERSARY Small Animal/Exotics

R E S P I R A T O R Y S T R E S S s P H Y S I C A L E X A M I N A T I O N s P H Y S I O L O G I C P A R A M E T E R S

Figure 1Buccal retractors provide the best visualization of thecheek teeth in sedated rabbits.

Figure 2A panicked rabbit can be wrapped in a towel for safe-ty during the physical examination.

Body temperature 101F104F

Heart rate 130325 beats/min

Respiratory rate 3060 breaths/min

Systolic blood pressure 90120 mm Hg

Normal Physiologic Parametersfor Healthy Rabbits


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pylorus is obstructed. It isnormal for hair, food, andfluid to be in the stomach;and plain films may not dis-tinguish these from a consol-

idated mass of dry material.Pneumogastrography shouldbe used with caution whenplain films or physical ex-aminations are inadequatefor diagnosis. To performpneumogastrography onrabbits, a small pediatricfeeding tube (3.5 to 5 Fr)can be passed into the ven-tral meatus of the nares (ap-plying lidocaine gel to the

tip of the tube and mucousmembranes before insertingthe tube can minimize irri-tation). The length of tubeneeded to span the distancebetween the nares and stom-ach should be measured andmarked. The tube should begently and rapidly advancedventrally and medially (keep-ing the head in a normal flexed position to help directthe tube into the esophagus rather than the trachea)3 and

20 to 40 ml of room air slowly injected into the stom-ach. Proper placement of the tube should be confirmedby radiographic evidence of air in the stomach. A consol-idated mass will be outlined by air contrast. If future gas-tric fluid therapy or feeding is necessary, the tube shouldbe secured to the side of the rabbits nose using a sutureor tissue adhesive and the tube taped between the ears.

VenipunctureRabbits have several accessible veins for venipunc-

ture, including the marginal ear, cephalic, lateral saphe-nous, and jugular veins. Restraint is important. Some

companion rabbits tolerate restraint in a towel, whereasothers are more fractious and may require mild seda-tion. Midazolam is recommended to reduce anxiety

when several diagnostic procedures must be performedon a frightened rabbit.

The approach to lateral saphenous and cephalic veinsis the same as that used for dogs and cats. Applying al-cohol to the fur without clipping it moistens the areasufficiently to visualize the vein. The marginal ear veinis useful for obtaining small quantities of blood. Largehematomas can, however, occur. In small breeds, ve-nous thrombosis and skin sloughing on the ear also are

possible.4 The jugular or lat-eral saphenous vein is the bestchoice for obtaining bloodsamples of 1 ml or more. For

jugular venipuncture, the

rabbit should be restrained atthe end of the examinationtable, with its head and legsextended for good access tothe jugular vein (Figure 3).Because drawing blood fromfemales with a large dewlapcan be difficult even if thedewlap is pulled tightly overthe jugular furrow, the dew-lap may require clipping,

which should be done cau-

tiously because the skin isvery thin in this region.A safe guideline for ob-

taining the maximum bloodvolume is to remove 1% ofthe body weight in grams.This benchmark is particu-larly important in dwarfbreeds. When the volume ofblood to be obtained is

small, the use of lithium heparin collection tubes in-stead of serum clot tubes can increase the volume of

plasma retrieved.

CystocentesisCystocentesis should be performed with the rabbit in

dorsal recumbency. We do not recommend attemptingcystocentesis through the lateral body wall because thececum may be encountered. Restraint is critical; the rab-bits body should be cradled with the handlers forearms

while the legs are being restrained with the handlershands. Although some rabbits relax or become mezmer-ized when the handler places a hand over their eyes, legrestraint is still necessary. The practitioner should then

rub alcohol in front of the pubis to allow visualization ofthe midline without the need for clipping. We recom-mend using a 23-gauge, 1-inch needle on a 5-ml syringe.

THERAPEUTIC PROCEDURESFluid Therapy

We recommend intravenous drug administration andfluid therapy for hospitalized rabbits in critical condi-tion. The fur over the vein should be clipped and thearea aseptically prepped. If time permits, a local anes-thetic consisting of 2.5% lidocaine and 2.5% prilocaine(EMLA CreamAstra USA, Westborough, MA) can be

Small Animal/Exotics 20TH ANNIVERSARY Compendium February 1999

P N E U M O G A S T R O G R A P H Y s J U G U L A R V E N I P U N C T U R E s M A X I M U M B L O O D V O L U M E

Figure 3Proper site for jugular venipuncture in a rabbit.


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generously rubbed over theveniclysis site to decrease theskin sensation 30 to 40 min-utes and thereby assist incatheter placement. A 24- or

27-gauge catheter can beplaced in most dwarfbreeds; whereas in large rab-bits, a 22-gauge cathetershould be used.

To facilitate fluid therapy,the largest-gauge catheterpossible in relation to therabbits size should be select-ed. Cephalic or lateral saphe-nous veins are well suited forindwelling catheters. Lateral

auricular veins can tolerate small-gauge catheters, butskin sloughing at the ear tip has been reported even withshort-term placement.4

If the ear is used, the pinna needs to be stabilized bytaping a roll of gauze along the inner surface and gentlytaping the pinna around the roll. The ears can be tapedtogether for extra stabilization. Indwelling cathetersshould be flushed frequently with saline. The use ofheparinized saline should be avoided in small breedsbecause excessive heparin exposure can occur withcatheter flushing.5

Critically ill rabbits may be hypotensive or have veins

that are too small or fragile for placing an intravenouscatheter. Use of an intraosseous catheter is preferred forthese rabbits. The proximal femur and tibia are recom-mended sites. The use of aseptic technique is essential,although osteomyelitis is a rare sequela of intraosseouscatheterization. A 20-gauge, 1-inch spinal needleshould be inserted into the greater trochanter of the fe-mur or into the tibial plateau and passed parallel to thelong axis of the femur or tibia, respectively.6When thestylet has been withdrawn, fluid should drip into themedullary space if the needle was properly placed. Theaccuracy of placement can be confirmed with radio-

graphs (Figure 4). The needle can then be secured witha skin suture. Although maintenance fluid requirements for criti-

cally ill rabbits are not well documented, 75 to 100ml/kg/day should be well tolerated as a continuous in-fusion. Crystalloids are most often indicated, but col-loids should be considered if the rabbit is hypopro-teinemic or when crystalloids fail to restore bloodpressure. Infusion pumps can help maintain an accu-rate flow rate, which is especially important in smallbreeds to avoid dangerous overhydration. Warm fluidscan help avoid hypothermia, which should be treated

aggressively with one bloodvolume (100 ml/kg) admin-istered over a 20-minute pe-riod. Whole blood transfu-sions are recommended when

the packed cell volume is12% or less. Blood typingfor rabbits has not been es-tablished.

For stable rabbits, subcuta-neous administration of ster-ile isotonic fluids one or twotimes daily at a rate of 50 to100 ml/kg can be consideredto provide the minimum dai-ly fluid requirement. Thetechnique followed is the

same as that used in dogs and cats. Because many own-ers are comfortable with this procedure after learningthe technique, it is a reasonable option for home care.

Oral fluids need to be provided at all times. Freshwater should always be available. Additional fluidchoices that rabbits will accept include Gatorade (TheGatorade Co., Chicago, IL), any over-the-counter oralpediatric electrolyte solution, and dilute apple or cran-berry juice; however, these choices should always be of-fered in addition to, not instead of, fresh water.

Analgesia

Pain management is an important aspect of rabbitcritical care. Signs of pain are subtle; as a prey species,rabbits conceal handicaps to escape predation. Rabbitsexperiencing pain may have a change in respiration, belethargic or anorectic, have constipation or diarrhea,show mild bruxism, or adopt a hunched posture. Othersigns of pain may include sudden aggression, inabilityto rest or sleep normally, or worried or anxious expres-sions.7 Because of the subtlety of these signs, the severi-ty of pain can be underevaluated and when it is recog-nized, often underestimated. As documented in humanand domestic animal literature, effective pain manage-

ment can facilitate the healing process, which also istrue for rabbits.8

Table I lists common opioid and antiinflammatoryanalgesics. In a limited number of cases, we have expe-rienced good results when using one half of a fentanylpatch to manage pain in a 3-kg rabbit during a 3-daypostoperative period.

Nutritional SupportAnorexia is a serious concern in rabbits when it extends

beyond 1 or 2 days. Because critically ill rabbits may bedehydrated, electrolyte imbalances worsen the problem.


C A T H E T E R I Z A T I O N s H Y P O V O L E M I A s P A I N C O N T R O L

Figure 4Radiograph showing placement of an intraosseouscatheter in the tibia of a rabbit.


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In addition, hepaticlipidosis can developrapidly when a rabbitstops eating; reversingthis metabolic process

can be difficult. Nutri-tional support needs tobe provided when arabbit has an acute lossof 10% of its body

weight or a chronic lossof 20%.9

Most commercialveterinary enteral dietsare produced for carni-vores and are unsuit-able for the herbivo-

rous rabbit. Humandiets tend to be toohigh in fat content andlow in fiber (nondi-gestible or insolublefiber) to meet the di-etary requirement ofrabbits. Rabbits, which(like horses) are hind-gut-fermenting herbi-vores, require high-fiber, low-fat diets. Low-fat enteralproducts for horses are commercially available and may

be better suited for other herbivores. Because 12% orless crude fiber has been associated with diarrhea in rab-bits, their dietary supplement should be high in fiber.10

Fiber is essential for the hind-gut production of short-chain fatty acids and stimu-lation of gastrointestinalmotility. Lack of insolublefiber is not resolved byadding soluble fibers (e.g.,psyllium). Although pelletscan be ground and added to

a liquid enteral product forsyringe feeding, the mixtureis too coarse for feeding viasmall-diameter nasogastrictubes. Osmotic diarrhea is apotential complication ofenteral support and may bethe result of elevated fat andcarbohydrates in the dietscommonly used for nutri-tional support; however, thiscomplication rarely merits

withdrawal of nutri-tional support.

Fluid and electro-lyte imbalances mustbe evaluated and cor-

rected before initiatingnutritional support,which must be startedgradually. Patients ingood condition canreceive 75% to 100%of their daily energyrequirement duringthe first 24 to 48hours. Debilitated pa-tients should receiveonly 40% to 70% of

their daily energy re-quirement during thefirst 24 hours, withthe amount graduallyincreased during thenext 3 to 5 days.9,10

Force or tube feedingsshould be divided intoa minimum of fourdaily feedings, and

food should be warmed. The caloric need for each pa-tient should be calculated using the following formula

for baseline metabolizable energy (ME) according tothe body weight (BW):

ME (kcal/day) =70 BW.75 (kg)

The range of estimatedcaloric requirement is 0.5 to3 times ME, but illnessmust be taken into consid-eration and is best calculat-ed as 1.25 to 2 times ME.

When selecting a diet, pro-

tein should be 26% of thetotal calories and fiber13.6% dry matter.10 Table IIlists options for enteral sup-port for rabbits.

As discussed in Part I,anorexia is often accompa-nied by a slow gastrointesti-nal transit time and inappro-priate motility of the cecumor stomach. Therefore, werecommend using motility-


L I Q U I D D I E T S s A N O R E X I A s F L U I D A N D E L E C T R O L Y T E I M B A L A N C E

TABLE I

Analgesic Agents Used in Rabbits

TABLE II

Examples of Liquid Enteral DietsUsed for Rabbit Critical Care

Dieta Manufacturer

NutriprimeTM Ken Vet, Ashland, OHJevityTMwith fiberb Ross Laboratories, Columbus, OH

Ensurewith fiberb Ross Laboratories, Columbus, OH

SusticalTMwith fiberb Ross Laboratories, Columbus, OHCriticare HNTM Mead Johnson Nutritionals,

Evansville, INVitalTM Ross Laboratories, Columbus, OHaCombine various components from blenderized rabbit pel-lets, powdered alfalfa, blenderized green leafy vegetables andfruits, or vegetable baby foods with a liquid diet from thistable to lower the kcal/ml while substantially increasing thefiber content.bThese formulations should be used with caution because theyare high-fat, low-fiber, highly digestible diets that can causediarrhea and/or loose stools.

Agent Dose (mg/kg) Route Interval

NSAIDsAcetaminophen16 200500 PO Every 6 hr

Aspirin17 100 PO Every 46 hr

Ibuprofen18 1020 PO Every 4 hr

Carprofen 24 PO, SC Every 1224 hr

Flunixin 1.1 SC, IM Every 1224 hr

meglumine18

Ketoprofen19 1.0 IM Every 1224 hr

Opioids

Buprenorphine17 0.010.1 SC, IV Every 612 hr

Butorphanol1 0.10.5 IM Every 34 hr

Oxymorphone20 0.050.2 SC, IM Every 812 hr

Meperidine20 510 SC, IM Every 23 hr

Pentazocine20 510 IM, IV Every 24 hr

Morphine20 25 SC, IM Every 24 hr

Naloxone18,20 0.010.1 IM, IV Reversal

IM= intramuscular; IV= intravenous; NSAID= nonsteroidal antiinflamma-tory drug; PO= oral; SC= subcutaneous.


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modifying agents (e.g., meto-clopramide or cisapride)

when administering enteralsupport. Regardless of theprimary cause of anorexia,

nutritional support is oftennecessary when rabbits are incritical condition.

Minimum SupportRabbits respond best when

in a familiar environment.Hospitalization can be stress-ful, and home care shouldbe considered when feasible.Minimum support may be optimal for mild to moder-ately ill patients that are hospitalized or being cared for

in the home. Rabbits receiving minimum supportshould be fed their customary diets (i.e., same brand,bowl, and amount). Fresh greens and timothy hayshould be part of a rabbits diet and can stimulate theappetite of anorectic rabbits.

If force feeding in the hospital or at home is required,syringe feeding of a blenderized diet, baby food vegeta-bles, or commercial liquid diets should be initiated. Sy-ringe feeding is the best way to maintain fiber in thediet if a rabbit is not eating on its own. The syringe tip

can be easily placed intothe diastema and the liquid

or slurry diet introducedslowly to avoid aspiration.Table II and In-HouseRecipe for Syringe Feedingoffer syringe- and tube-feeding formulas.

Orogastric Tube FeedingOrogastric tube feeding is

suitable only for single-epi-sode dosing during stabi-lization because if used re-

peatedly, it can result instress and considerable risk.Proper restraint is necessaryto prevent the rabbit frominjuring itself in attempts toescape the procedure; wrap-

ping a towel tightly around the rabbits body and tuckingit under the rump can be helpful during restraint. A

wooden or plastic dowel with a hole drilled through thecenter should be placed across the diastemas. We recom-mend using a round-tipped 18- to 22-Fr rubber catheter(Figure 5) to prevent entry into the trachea.

Before the tube is inserted,the distance from the mouthto the last rib should be pre-measured and marked on thetube. The tip of the catheter

should be lubricated andthen, with the neck flexed,passed through the hole inthe dowel, into the orophar-ynx, and into the stomach.Proper placement can be con-firmed by instilling a smallamount of saline into thecatheter. However, if the rab-bit begins to cough severely,

the tube has most likely penetrated the trachea. Suchpenetration can be verified by auscultating the stomach

and listening for bubbling noise while 3 to 5 ml of air isbeing injected into the tube or by pulling the tube backinto the esophagus and thereby causing suction and re-sultant negative pressure as the esophagus collapsesaround the tube opening. Verification of correct tubeplacement is essential before food is introduced.

Nasogastric Tube FeedingNasogastric tube feeding is warranted if pneumogas-

trograms of gastric contents are needed for radiographicevaluation, gastric bloat occurs, or multiple enteralfeedings are required. In such situations, having access

to a tube that can be manipulated behind the animalsvisual field is advantageous. The primary disadvantageof using nasogastric tubes for enteral feeding is theirsmall diameters, which make administering fibrous ma-terial difficult. This problem can be resolved somewhatby using an open-ended tube and cutting additionalholes along the tubes length, which minimizes thechance of clogging the tip.

The technique for placing nasogastric tubes is thesame as that for orogastric tubes. The accuracy of tubeplacement can be verified by lateral radiographs, fluor-oscopy of the thorax and cranial abdomen, or injection

of 10 ml of air while auscultating for gastric bubbles.The tube can then be secured with a drop of superglueon the furred skin above the nose and butterfly tapeglued or sutured at the top of the head between theears. To avoid leakage of gastric contents, a catheteradapter can be placed over the open end. When usingnasogastric tubes for alimentation, placement and pa-tency can be checked before each use by injecting asmall amount of saline as described in the section onOrogastric Tube Feeding. Tube obstruction can beavoided by flushing the tube with water before and af-ter administering medication or nutritional support.


S U P P O R T M E A S U R E S s E N T E R A L F E E D I N G s T U B E O B S T R U C T I O N

Figure 5Insertion of an orogastric tube in a rabbit.

8-oz can Ensure with fiber

(Ross Laboratories)

1 cup fruit yogurt

6 Tbsp alfalfa meal

Mix ingredients in a blender.

Total kcal = 1.4 kcal/ml with

13.6% fiber and 36%

protein. A critically ill rabbit

weighing 5 lb would need

approximately 1 oz of this

slurry every 3 hours.10

In-House Recipe for

Syringe Feeding


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Nasogastric tubes are generally tolerated by rabbits.Elizabethan collars can be stressful for rabbits andshould be used only if well tolerated. For rabbits thatdo not accept a nasogastric tube or Elizabethan collar,other options such as feeding via percutaneous tube or

force feeding with a syringe should be considered.

Percutaneous Gastrostomy Tube FeedingFeeding by percutaneous gastrostomy tube may be

necessary for some rabbits. Percutaneous placement ofgastrostomy tubes adapted to use in rabbits follows atechnique similar to that used for other companion ani-mals.11 Because rabbits have a small oral cavity, however,a bronchoscope rather than a small endoscope is neces-sary. Caution must be exercised when passing the bron-choscope over the base of the tongue (between the rab-bits sharp molar teeth). In addition, rabbits must be at a

surgical plane of anesthesia before tube insertion. Appli-cation of lidocaine gel on the tip of the bronchoscopeand the feeding tube facilitates insertion. The presenceof hair and digesta in the stomach should be anticipat-ed, even if a rabbit has been anorectic for several days.

Pharyngostomy Tube FeedingPharyngostomy tube feeding is apparently well toler-

ated by rabbits, although abscesses can develop alongthe subcutaneous tract of the catheter. Placement andmaintenance of pharyngostomy tubes have been de-scribed in the literature.12 We recommend practicing

pharyngostomy tube placement on cadavers before at-tempting the procedure on critically ill rabbits.

IntubationThe use of an uncuffed 1.0- to 2.5-mm endotracheal

tube (ET) is recommended for intubation of rabbitsweighing 3 kg or less.13 Blind intubation of small rabbitscan be either oral or nasal but should only be attemptedif the rabbit is breathing and not in respiratory arrest.

Anesthesia can be induced by slow injection of intra-venous propofol (2 to 4 mg/kg) or mask inhalation ofisoflurane. The rabbit should be placed in sternal recum-

bency with its head extended so the trachea is perpendic-ular to the table surface. To avoid laryngospasm, 1 ml oflidocaine should be applied topically to the larynx.

While advancing the ET to the proximal larynx, practi-tioners should listen at the end of the adapter for inspira-tion sounds. When the sound is at the loudest, the tubecan be slowly advanced into the trachea. In large rabbits(weighing 3 kg or more), the glottis can usually be visu-alized through a laryngoscope with a No. 1 Miller blade;however, the oral cavity is often too small to maintain vi-sualization when the ET has been inserted into theoropharynx. A 5- or 8-Fr, 56-cm long polypropylene uri-

nary catheter (flared end cut off after placement) can beadvanced into the trachea as a guide. The laryngoscopeblade should then be removed and the ET advanced overthe guide and into the trachea.14

Several other methods of endotracheal intubation de-

scribed in the literature involve insertion of a rigidbronchoscope through the ET for better visualizationof the vocal folds15 and use of a special stethoscope fit-ted with an ET for better auscultation of breathingsounds at intubation.16 Positive-pressure ventilation andchest excursions should never be used to test placementof the ET because air entering the stomach often mim-ics true chest excursion.

CardiopulmonaryResuscitation

Cardiopulmonary arrest is

the sudden cessation ofspontaneous, effective venti-lation and circulation. Re-spiratory arrest generally oc-curs first, followed by cardiacarrest several minutes later ifthe respiratory arrest is notresolved. The goal of car-diopulmonary resuscitation(CPR) of rabbits is similar tothat for other mammalsprovide ventilation and cir-

culatory support until spon-taneous functions have beenrestored. The chief differencebetween CPR for rabbits andthat for other companion an-imals involves the rabbitssmall size and rapid metabol-ic rate and the difficulty ofestablishing a patent airway.Because their rapid heart andrespiratory rates correlate

with more circulations per

minute, rabbits succumb tocardiopulmonary arrest morequickly than do larger mam-mals. The difficulty of estab-lishing a patent airway iscompounded by the in-creased urgency of time. Ifendotracheal intubation hasnot been accomplished with-in 60 seconds, the airwayshould be assessed via tra-cheostomy. Endotracheal in-


E N D O T R A C H E A L P R O C E D U R E S s R E S U S C I T A T I O N s T R A C H E O S T O M Y

Twenty years ago, domesticated

rabbits were not as popular

companion animals as were

dogs and cats, and

veterinarians therefore did not

have to address the issues raised

today. Because of our growing

awareness, however, today we

can utilize increased knowledge

of the gastrointestinal (GI)

system in general and therefore

of the nutritional needs of

rabbits. For example, we now

know that high fiber is

necessary for proper GI motility

and realize that the presence of

trichobezoars is not a signal for

surgery but is a result of

decreased GI motility. In fact,these rabbits generally do very

well with medical manage-

ment, an option not recognized

20 years ago.

A LookBack

COMP

ENDIUMS

20thANNIVERSARY

1 97 9 -

1 9 9 9


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6. Anderson NL: Intraosseous fluid therapy in small exotic ani-mals, in Kirks Current Veterinary Therapy. XII. Philadelphia,

WB Saunders Co, 1995, pp 13311335.7. Eisele PH: Signs of pain in small mammals. Proc TNAVC:795

796, 1997.8. Eisele PH: Analgesia in small mammals. Proc TNAVC:796

799, 1997.9. Donoghue S, Langenberg J: Clinical nutrition of exotic pets.

Aust Vet J71(10):337341, 1994.10. Donoghue S: Nutrition and pet rabbits, in Rosenthal KL (ed):

Practical Exotic Animal Medicine (The Compendium Collec-tion). Trenton, NJ, Veterinary Learning Systems, 1997, p107.

11. Smith DA, Olson PO, Mathews KA: Nutritional support forrabbits using a percutaneously placed gastrostomy tube: Apreliminary study.JAAHA33(1):4854, 1997.

12. Rogers G, Taylor C, Austin JC, et al: A pharyngostomytechnique for chronic oral dosing of rabbits. Lab Anim Sci38(5):619620, 1988.

13. Paul-Murphy J: Little critters: Emergency medicine for smallrodents. Proc Fifth Intl Vet Emerg Crit Care Symp:714718,

1996.14. Eisele PH: Anesthesia for the rabbit. Proc TNAVC:792794,

1997.15. Conlon KC, Corbally MT, Bading JR, Brennan MF: Atrau-

matic endotracheal intubation in small rabbits. Lab AnimSci40(2):221222, 1990.

16. Patil VU, Fairbrother C, Dunham BM: Endotracheal intu-bation in the rabbit: A quick, reliable method. Lab AnimFeb:2829, 1997.

17. Wixson SK: Anesthesia and analgesia, in Manning PJ, Ring-ler DH, Newcomer CE (eds): The Biology of the LaboratoryRabbit, ed 2. New York, Academic Press, 1994.

18. Flecknell PA: Post-operative analgesia in rabbits and rodents.Lab Anim20(2):3437, 1991.

19. Smith DA, Burgmann PM: Formulary, in Hillyer EV, Que-senberry KE (eds): Ferrets, Rabbits and Rodents: ClinicalMedicine and Surgery. Philadelphia, WB Saunders Co, 1997,pp 392403.

20. Perrin A, Milano G, Thyss A, et al: Biochemical and phar-macological consequences of the interaction between metho-trexate and ketoprofen in the rabbit. Brit J Cancer62:736741, 1990.

21. Mason DE: Anesthesia, analgesia, and sedation for smallmammals, in Hillyer EV, Quesenberry KE (eds): Ferrets, Rab-bits and Rodents: Clinical Medicine and Surgery. Philadelphia,

WB Saunders Co, 1997, pp 378391.


tubation can be extremely difficult when a rabbit is notbreathing.

Although a tracheostomy tube can be placed with therabbit under local anesthesia, often rabbits in cardiopul-monary arrest have lost consciousness and anesthesia is

unnecessary. Alcohol can be poured over the ventralneck region to part the hair and aid in visualization ofthe trachea. An incision should then be made over thetrachea immediately caudal to the larynx, the tracheapulled toward the incision, and retracting sutures placedin the third and fourth rings. Next, an incision shouldbe made between the cartilaginous rings and the retract-ing sutures gently pulled apart. We advise taking ex-treme caution and exerting minimal force while guidingthe sterile 2.0-mm tracheostomy tube into the distal tra-chea. After tube placement, oxygen should be providedand positive-pressure ventilation initiated.

SUMMARYBecause they can become stressed so quickly, critical-

ly ill rabbits can be challenging patients. The basicprinciples guiding emergency and critical care for rab-bits are the same as those used for other mammals;however, the presenting signs and diagnostic approach-es differ considerably. Practitioners need to assess a crit-ically ill rabbit while it remains in its cage We recom-mend evaluating the general attitude, respiratory rateand character, and fecal and urine consistency beforeremoving a companion rabbit from its cage. In addi-

tion, once rabbits has been removed from a familiar en-vironment, such as their cage, they can hide clinicalsigns that would be more apparent in other companionanimals. Thus, practitioners must look for subtle indi-cations of pain or discomfort.

When hospitalization is necessary, rabbits must behoused in a quiet, low-stress environment separate fromthe sounds and scents of other animals. Because rabbitscan become panicky or agitated, practitioners shouldmake special efforts to provide a calming atmosphere.

References

1. Carpenter JW, Mashima TY, Rupiper DJ: Exotic AnimalFormulary. Manhattan, KS, Greystone Publications, 1996.2. Plumb DC: Veterinary Drug Handbook.Ames, IA, Iowa State

University Press, 1995.3. Bennet RA: Nasogastric intubation for enteral alimentation.

Proc Fifth Intl Vet Emerg Crit Care Symp:723, 1996.4. Mader DR: Basic approach to veterinary care, in Hillyer EV,

Quesenberry KE (eds): Ferrets, Rabbits and Rodents: ClinicalMedicine and Surgery. Philadelphia, WB Saunders Co, 1997,pp 160168.

5. Stevens LC, Haire WD, Tarantolo S, et al: Normal salineverses heparin flush for maintaining central venous catheterpatency during apheresis collection of peripheral blood stemcells. Transfusion Sci18(2):187193, 1997.

About the Authors

When this article was accepted for publication, Dr. Ramerwas affiliated with the Department of Surgical Sciences,

School of Veterinary Medicine, University of Wisconsin,

Madison, Wisconsin; she is presently affiliated with the In-

dianapolis Zoo, Indianapolis, Indiana. Dr. Paul-Murphy is

affiliated with the Department of Surgical Sciences,

School of Veterinary Medicine, University of Wisconsin,

Madison, Wisconsin, and is a Diplomate of the American

College of Zoological Medicine. Dr. Benson is a resident

in Zoological Medicine at the School of Veterinary Medi-

cine, University of California, Davis, California.

Documents

EXOTİC-Evaluating and stabilizing critically Ill Rabbits.Part II