12
Fish Surgery MichaelJ. Murray, DVM As the number and value of captive fishes increases, so too will the indications for surgical intervention by the veterinarian. In general, the most difficult aspect of fish surgery is the provision of adequate and safe anesthe- sia, and several different anesthetic regimens are pro- vided. Once one is familiar with the normal anatomy of the piscine patient, the basic concepts of surgery pre- vail, including appropriate surgical approach, hemosta- sis, and gentle tissue manipulation. Specific surgical procedures, celiotomy, liver biopsy, renal biopsy, and laparoscopy are discussed. Finally, successful outcome of a surgical manipulation often rests in the postoper- ative management of the surgical patient. Suggestions for appropriate postoperative management are also discussed. Copyright 2002, Elsevier Science (USA). All rights re- served. Key words: Fish, surgery, anesthesia, laparoscopy, ce- liotomy, biopsy. increased. Public aquaria have increased in both number and complexity and often exhibit fish with substantial financial and genetic value. As a result, advances in fish surgery have become commonplace. A number of excellent reviews of surgery in the piscine patient have been published recently in the veterinary literature. 1,2 Much of the earli- est work published was directed towards and written by fish pathologists and biologists with particular emphasis on diagnostic sample collec- tion and transmitter implantation. ~-7An attempt will be made within this review to present a more traditional veterinary approach to fish surgery that includes discussion of anesthesia, patient preparation, instrumentation, surgical proce- dures, and postoperative management. ggVou can do that?" is probably one of the At most commonly encountered responses to clinicians advocating a surgical manipulation of a piscine patient. On the surface, one should not be terribly surprised at such a response; however, one need only look more carefully at the demographics associated with captive fish to understand some of the driving forces behind "pet" fish medicine. Although the exact num- bers are difficult to ascertain, the results of the 2001 pet ownership survey posted on the Amer- ican Pet Product Manufacturers Association Web site indicate that there are approximately 160 million pet fish. Many of these fish are dear pets to their owners, and the human-animal bond definitely influences the level of veterinary care expected. As life support systems for captive fish have improved and decreased in cost, both the value and longevity of many specimens has From the Monterey Bay Aquarium, Monterey, California. Address correspondence to Michael J. Murray DVM, Monterey Bay Aquarium, 886 Cannery Row, Monterey, CA 93940. Copyright 2002, Elsevier Science (USA). All rights resemed. 1055-937X/02/1104-0007535.00/0 doi:10.1053/saep. 2002.126571 Anesthesia Debate still occurs regarding the ability of fish to feel pain. Whether or not they feel pain, it is incumbent upon the veterinarian to err on the side of caution, assume pain can be experi- enced, and offer anesthesia during painful pro- cedures (Table 1). There can be no doubt, how- ever, regarding the often violent reaction that fish have to noxious stimuli. One must always recognize the potential for idiosyncratic problems with anesthetics in fish. For that reason, there are circumstances in which painless procedures, such as skin scrap- ings, may be carried out with gentle physical restraint. This does not imply, however, that physical restraint is appropriate for procedures that may be painful to the fish. Many elasmobranches are adequately sedated following immersion in a water column that is supersaturated with oxygen. Still other species may be adequately immobilized by physically holding them in dorsal recumbency via a process of tonic immobility. This practice should be used with caution because some species may experience adverse effects to extended periods of tonic immobility. 246 Seminars in Avian and Exotic Pet Medicine, Vol 11, No 4 (October), 2002: pp 246-257

FISH SURGERY

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Page 1: FISH SURGERY

Fish Surgery MichaelJ. Murray, DVM

As the number and value of captive fishes increases, so too will the indications for surgical intervention by the veterinarian. In general, the most difficult aspect of fish surgery is the provision of adequate and safe anesthe- sia, and several different anesthetic regimens are pro- vided. Once one is familiar with the normal anatomy of the piscine patient, the basic concepts of surgery pre- vail, including appropriate surgical approach, hemosta- sis, and gentle tissue manipulation. Specific surgical procedures, celiotomy, liver biopsy, renal biopsy, and laparoscopy are discussed. Finally, successful outcome of a surgical manipulation often rests in the postoper- ative management of the surgical patient. Suggestions for appropriate postoperative management are also discussed. Copyright 2002, Elsevier Science (USA). All rights re- served.

Key words: Fish, surgery, anesthesia, laparoscopy, ce- liotomy, biopsy.

increased. Public aquaria have increased in both n u m b e r and complexity and often exhibit fish with substantial financial and genetic value. As a result, advances in fish surgery have become commonplace .

A n u m b e r of excellent reviews of surgery in the piscine pat ient have been published recently in the veterinary literature. 1,2 Much of the earli- est work published was directed towards and written by fish pathologists and biologists with particular emphasis on diagnostic sample collec- tion and transmit ter implantation. ~-7 An a t tempt will be made within this review to present a more traditional veterinary approach to fish surgery that includes discussion of anesthesia, pat ient preparat ion, instrumentat ion, surgical proce- dures, and postoperative management .

g g V o u can do that?" is probably one of the At most commonly encounte red responses

to clinicians advocating a surgical manipula t ion of a piscine patient. On the surface, one should not be terribly surprised at such a response; however, one need only look more carefully at the demographics associated with captive fish to unders tand some of the driving forces behind "pet" fish medicine. Although the exact num- bers are difficult to ascertain, the results of the 2001 pe t ownership survey posted on the Amer- ican Pet Product Manufacturers Association Web site indicate that there are approximately 160 million pet fish. Many of these fish are dear pets to their owners, and the human-animal bond definitely influences the level of veterinary care expected. As life suppor t systems for captive fish have improved and decreased in cost, both the value and longevity of many specimens has

From the Monterey Bay Aquarium, Monterey, California. Address correspondence to Michael J. Murray DVM, Monterey

Bay Aquarium, 886 Cannery Row, Monterey, CA 93940. Copyright 2002, Elsevier Science (USA). All rights resemed. 1055-937X/02/1104-0007535.00/0 doi: 10.1053/saep. 2002.126571

Anesthesia

Debate still occurs regarding the ability of fish to feel pain. Whether or not they feel pain, it is incumbent upon the veterinarian to err on the side of caution, assume pain can be experi- enced, and offer anesthesia during painful pro- cedures (Table 1). There can be no doubt, how- ever, regarding the often violent reaction that fish have to noxious stimuli.

One must always recognize the potential for idiosyncratic problems with anesthetics in fish. For that reason, there are circumstances in which painless procedures, such as skin scrap- ings, may be carried out with gentle physical restraint. This does not imply, however, that physical restraint is appropr ia te for procedures that may be painful to the fish.

Many elasmobranches are adequately sedated following immers ion in a water column that is supersaturated with oxygen. Still o ther species may be adequately immobil ized by physically holding them in dorsal recumbency via a process of tonic immobility. This practice should be used with caution because some species may exper ience adverse effects to extended periods of tonic immobility.

246 Seminars in Avian and Exotic Pet Medicine, Vol 11, No 4 (October), 2002: pp 246-257

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Fish Surge U 247

Table 1. Anesthetic Doses

Anesthetic Agent Dose

Inhalant anesthetics Tricaine

methanesulfonate Induction Maintenance

Eugenol Induction Maintenance

Injectable anesthetics Ketamine

Teleost Elasmobranch

Ketamine/ medetomidine

Immobilization

Reversal, atipamezole

Ketamine/xylazine (sharks)

Ketamine Xylazine

100-200 mg/L 50-100 mg/L

100-120 mg/L 40 mg/L

66-68 mg/kg IM 12-20 mg/kg IM

Ket, 1-2 mg/kg IM Medet, 50-100 /xg/kg IM

200/,g/kg IM

12-20 mg/kg IM 6 mg/kg IM

Abbreviation: IM, intramuscularly. Table reprinted with permission, s

Inhalant Anesthetics

Not to be confused with the traditional inhal- ant agents used in terrestrial animal anesthesia, inhalants include those compounds added to the water that sedate or anesthetize the fish. Although a n u m b e r of compounds have been

' emp loyed in the past, the most commonly used agents currently in use are tricaine methanesul- fonate (MS-222 or Finquel; Argent Chemical Laboratories, Redmond, WA) and eugenol. Both compounds are readily available and have been evaluated for both efficacy and safety.

Generally, fish are initially placed in an induc- tion chamber that contains the p roper levels of anesthetic, with the appropr ia te temperature , pH, and oxygen levels, and is large enough to prevent excessive struggling but not so large as to permi t concussive injury. Once the fish reaches an appropr ia te level of anesthesia, it may be removed f rom the induction chamber for out-of-water procedures.

For procedures that are expected to be shorter in duration, such as gill or fin biopsies, no fur ther chemical restraint may be required. In general, the t ime that the fish is held out of water should be less than 5 minutes, s In more

p ro longed procedures a mechanism for main- taining respiratory suppor t and acceptable anes- thetic levels must be provided.

Inhalant anesthesia as described in this con- text may be mainta ined in one of t w o fashions. In smaller specimens, a non-rebreathing system may be used. Anesthetic- and oxygen-laden wa- ter appropriately p repared for the fish may be placed in a reservoir bag, such as an expended IV bag. Anesthetic-laden water may then be de- livered via gravity flow through an appropriately sized tube through the oral cavity directed over the gill filaments. Flow rates are easily control led with clamps on the tubing. Water that accumu- lates may be drained into ano ther reservoir but is not recycled over the fish's gills.

In larger specimens a rebreathing system is r ecommended . A variety of anesthetic delivery systems have been described. In the author ' s experience, the design described by Lewbart and Harms is prefer red and may be modif ied to anesthetize large specimens (Fig 1). sq~ In this system, anesthetic-laden water is p u m p e d f rom a reservoir across the fish's gills f rom where it drains back into a reservoir for recirculation to the patient. Such a system permits a p ro longed out-of-water p rocedure yet still maintains ade- quate respiratory suppor t and anesthesia. It is impor tan t that the flow be directed over both gill arcades and in a no rmograde fashion. Ret- rograde flow may compromise the normal counter-current mechanism of the gills and may actually ha rm the structures.

Figure 1. Piscine rebreathing anesthetic system. A side port off the power head (white arrow) is used to provide a trickle of water to keep the fish moist (black arrow). Reprinted with permission. 1~

Page 3: FISH SURGERY

248 Michael f Murray

Despite the apparen t "bullet-proof ' nature of these systems, there are areas of concern. First, one must be ever cautious of water quality. Pro- longed procedures may result in water that be- comes increasingly contaminated with nitroge- nous waste. Additionally, one should be certain that adequate gas exchange is occurring at the water 's surface. In some circumstances it may be necessary to percolate oxygen through the anes- thetic reservoir. In most cases, a dissolved oxy- gen concentra t ion of 6-10 p p m is adequate since p ro longed exposure to high oxygen levels may be damaging to the respiratory system (the gills). Finally, such a system has limits to varying the "anesthetic setting." One may modify the anesthetic concentra t ion of the reservoir by add- ing a known concentra t ion of anesthetic or a known volume of clean water to the system to ei ther raise or lower the anesthetic concentra- tion, respectively. Mternatives to such manipula- tions include multiple reservoirs of varying con- centrat ion or the use of an al ternating system of anesthetic provision at a steady level, followed by use of anesthetic-free water when the anesthetic depth becomes excessive.

Tricaine Methanesulfonate (MS-222)

MS-222 is probably the most commonly used fish anesthetic at this time. It is a water-soluble benzocaine derivative that is FDA-approved for use in food fish that require a 21-day withdrawal time. In aqueous solution, tricaine is acidic, with a p H of nearly 3.0. There fore buffering is nec- essary, typically with sodium bicarbonate, espe- cially in freshwater systems. Marine systems typ- ically contain adequate inherent buffering, but the p H should always be evaluated before the induct ion of fish with MS-222.

Tricaine is generally recognized to cause hyp- oxia, hypercapnia, and acidosis. 11 Secondary to these effects hyperglycemia and elevations of potassium, magnesium, hemoglobin, and he- matocr i t may also be noted. An increase in uri- nary output and subsequent electrolyte loss may be no ted for up to a week postanesthetic, lz

It is r e c o m m e n d e d that an aqueous stock so- lution (10 g in /L) of MS-222 be p repared for dosing anesthetic systems. Such stock solutions are unstable in light, necessitating storage in dark containers, and can be refrigerated or fro- zen for increased shelf life. Because of the acidic

nature of the solution, buffering of anesthetic systems should occur just before their use on fish. An oily residue noted on the surface of the stock solution indicates that desulfonation has occurred and that the solution has lost potency and should be replaced.

As a general guideline, MS-222 induction is carried out at concentrat ions of 100-200 m g / L . Anesthetic main tenance may then be accom- plished at 50-100 m g / L . It is imperative that the clinician develops a familiarity with the effects of the agent upon the species in question. Varying degrees of sensitivity to MS-222 have been ob- served, and margins of safety may vary depend- ing upon the water-quality parameters . In most cases, the rate of recovery is directly related to the length of anesthesia, anesthetic depth, and water quality. One would typically anticipate rapid recovery of less than 15 minutes in shorter procedures and pro longed recover?, periods (hours) in procedures of a longer duration.

Eugenol (Clove Oil)

The phenol ic c o m p o u n d eugenol is the active ingredient in clove oil, which has long been advocated as a safe and effective anesthetic by fish hobbyists and commercia l fish farmers. 1~ Because eugenol is not water-soluble, it must be diluted in 95% ethanol before use. Generally, it is diluted 1:10 in 95% ethanol to p roduce a stock solution of 100 m g / m L . A concentra t ion of 100- 120 m g / L is generally used for induction, 40 m g / L for maintenance.

When compared with MS-222, both com- pounds were found to contr ibute to hypoxemia, hypercapnia, acidosis, and hyperglycemia. 11 Eu- genol typically results in a more rapid induction and a more p ro longed recovery per iod than MS- 222. Eugenol has a more narrow range of safety and may in fact cause respiratory failure at higher doses. As with MS-222 one must be cog- nizant of the idiosyncratic reactions to eugenol, such as the cardiorespiratory depression and death noted anecdotally with Acanthuridae (tangs and doctorfish). 1

Injectable Anesthetics There are circumstances in which inhalation

anesthesia is inappropr ia te for use. It may not be possible to provide anesthetic induction cham-

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JFish Surgery 249

bers for very large specimens. Some species such as Scombridae do not tolerate conf inement , and "capture" of individuals in large aquaria may preclude induct ion with tricaine or eugenol. In those instances, parenteral administrat ion of agents may be indicated.

In t ramuscular injections are typically given in the dorsolateral musculature dorsal to the lat- eral line. Although intramuscular injections are not the ideal method, they may be necessary, particularly when injection with a pole syringe or Hawaiian sling is necessary in larger aquaria. When adminis ter ing intramuscularly, a deep in- ject ion may aid in minimizing the re t rograde drainage of the material f rom the injection site. I f possible, the needle should be directed crani- ally to minimize damage to the integument .

Ketamine

An injectable, short-acting, dissociative anes- thetic agent, ke tamine hydrochlor ide is rarely used alone, but ra ther in combinat ion with other agents, such as the ~-agonists medetomi- dine or xylazine hydrochloride. In most teleost fish, a relatively high dose is required for immo- bilization and therefore is often used as an "in- duction" agent. Elasmobranchs are typically much more sensitive to the effects of ke tamine and may require addit ion of an o~-agonist for adequate sedation, s

Propofol

The intravenous sedat ive/hypnot ic agent propofol has some potential use as an anesthetic despite its obvious limitation as an intravenous- only compound . O f particular interest is its ap- plication in tonically immobil ized fish such as elasmobranchs. It has several advantages when used, including rapid, smooth induction, rela- tively short durat ion of effect, and noncumula- tive effects. It has been used in sharks at a dose of 2.5 m g / k g adminis tered intravenously over a 30-second per iod into the caudal vein. TM Follow- ing administration, righting reflex is lost within 5 minutes and returns in approximately 75 min- utes.

Anesthetic Monitoring

As in traditional surgery, anesthetic monitor- ing in fish is as impor tan t as any o ther aspect of

the procedure . One may attribute a series of stages, planes, and descriptions to the events that occur as the fish proceeds f rom its normal state to the deepest state of anesthes ia--sedat ion followed by narcosis and finally anesthesia. 12 Care should be taken to prevent iatrogenic in- jury to the fish as it passes through the excitabil- ity phase of anesthesia. During this period, the fish may swim erratically and may even a t tempt to leap f rom the induction chamber . An exces- sive anesthetic time or dose results in medul lary collapse and respiratory arrest followed by car- diac arrest.

For procedures involving minimal t ime a n d / o r pain, a state of deep narcosis is typically adequate. At this level the fish does not respond to positional changes, has a nearly normal respi- ratory rate, shows no a t tempt to right itself, but may demonst ra te some reactivity to strong stim- uli. In a plane of surgical anesthesia, there is a total loss of reactivity, and the respiratory and cardiac rates are very slow but strong.

Several parameters are generally moni to red in an effort to gauge anesthetic level (Table 2). Respiratory rate, as evidenced by opercular movements , is probably the most important . Others include jaw tone, reaction to postural changes, muscle tone, and reaction to painful stimuli.

There has been little success to date in the use of pulse oximetry in fish anesthesia; however, a Doppler-flow probe over the hear t may be useful in de termining hear t rates. 8

Patient Preparation and Instrumentation

As in any surgical procedure , presurgical prepara t ion should enhance the pat ient 's ability to survive the p rocedure and re turn to normal function quickly. Presurgical m a n a g e m e n t of the piscine pat ient is no different (see Table 3). If possible, underlying aberrat ions in the pa- tient 's water quality, temperature , and so on should be corrected in an effort to make a more stress-tolerant anesthetic and surgical candidate.

Attempts should be made to minimize prean- esthetic stress on the fish. Fish that are "relaxed" tend to p roceed th rough anesthetic induction more smoothly than those that become excited. Food should be withheld for at least 1 feeding cycle to decrease both ni t rogenous waste prod-

Page 5: FISH SURGERY

250 Michael J. Murray

Table 2. Anesthetic Stages in Fish

Stage Plane Parameter Observed Effect

I Sedation Light Equilibrium Normal

Muscle tone Normal Respiratory rate Normal Cardiac rate Not determined Reaction to stimuli Slight loss

Deep

II Narcosis Light

Deep

III Anesthesia Light

Surgical

IV Medullary Collapse

Equilibrium Muscle tone Respiratory rate Cardiac rate Reaction to stimuli

Equilibrium Muscle tone Respiratory rate Cardiac rate Reaction to stimuli

Equilibrium Muscle tone Respiratory rate Cardiac rate Reaction to stimuli

Equilibrium Muscle tone Respiratory rate Cardiac rate Reaction to stimuli

Equilibrium Muscle tone Respiratory rate Cardiac rate Reaction to stimuli

Equilibrium Muscle tone Respiratory rate Cardiac rate Reaction to stimuli

Normal Slight decrease Slight decrease Not determined Lost, still reacts to postural changes

Loss, weak response to postural changes Decreased Increased, excitatory phase Not determined Excitement phase, increased

Loss, no response to postural changes Decreased Normal Normal Reaction to strong stimuli Suitable for minor sampling, biopsy

Loss, no response to postural changes Loss Decreased Decreased Respond to deep pressure Suitable for minor surgery

Loss Loss Very low Slow Total loss of reactivity Surgical plane of anesthesia

Loss Flaccid Total loss of gill movement, apnea Cardiac arrest follows resp arrest None Suitable for euthanasia ONLY!

Reprinted with permission. 12

uc t bu i ld -up a n d the pa r t i cu l a t e l oad to the wa- te r c o l u m n , which may c log the gill rakers .

O n e c a n n o t overs ta te the i m p o r t a n c e o f gen- tle h a n d l i n g o f the fish pa t i en t . R o u g h h a n d l i n g , especia l ly in abras ive nets, will resu l t in the loss o f excessive a m o u n t s o f the sur face p ro t ec t ive mucus a n d p r e d i s p o s e the fish to s e c o n d a r y cu-

t a ne ous infec t ions . Us ing plas t ic bags o r la tex e x a m gloves ( f rom which the p o w d e r has b e e n r insed) in t h e ' h a n d l i n g process will m i n i m i z e this d a m a g e .

O n c e the fish has b e e n sui tably anes the t i zed , it may be p l a c e d in a su i tab le s u p p o r t s t ruc tu re for the p r o c e d u r e . Any ma te r i a l tha t contac t s

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Fish Surgery 251

Table 3. Considerations for Fish Surgery

Preoperative

Intraoperative

Postoperative

Water quality Minimize stress Withhold food for 1 feeding cycle Gentle handling

Minimal skin preparation Pull scales individually Keep skin moist Monofilament suture

Recovery tank Resuscitation Increased oxygen saturation Minimize stress Analgesics Antibiotics

the fish's skin, such as the foam in V-troughs, must be moistened before introducing the ani- mal. It is often helpful to cover the fish's eyes as an aid to the anesthetic effects. When out-of- water surgery is being carried out, the skin must be kept moist th roughout the procedure. A va- riety of devices, including turkey basters, sy- ringes, and 1V bags may be used for this main- tenance technique.

Although there should be some form of pre- surgical preparat ion of the entry site, it should minimally disrupt the protective functions of the skin and mucus layer. In most instances, a cot- ton-tipped applicator moistened with sterile sa- line may be used to reduce the surface contam- ination. If antiseptics truly are indicated, they should be quite dilute, 1:20 povidone-iodine or 1:40 chlorhexidine being recommended. 1 Alco- hols should never be used because they tend to damage the skin. For fish with large scales, the scales should be gently removed individually along the incision line. Fine-scaled fish, such as the salmonids, need not have scales removed.

Clear plastic drapes are generally advocated for fish surgery. They tend to isolate the surgical site for aseptic procedures and help to keep the surrounding skin moist by reducing evaporation (Fig 2). A ring of pe t ro leum jelly a round the incision area is typically adequate for adhesion of the drape to the fish's skin.

A number of suture materials have been ad- vocated for use in fish. It is impor tant to recog- nize that between mammals and fish the absorb- ability and reactivity of many materials is not the same. Many synthetic "absorbable" suture mate-

rials have been recovered from the coelom years following surgical procedures. This prolonged retent ion time suggests that a monof i lament su- ture may be preferable to decrease the possibil- ity of secondary infection associated with the wick-like effect of braided materials. Studies of reactivity and incision-healing time also tend to favor monof i lament materials, with the greatest reactivity and longest healing time found to be with polyglactin 910, and the least and shortest with monofilament nylon and polydioxanone.m5

For the vast majority of surgical cases involv- ing fish, the instrumentation necessary is already present within the typical veterinary clinic. Some form of magnification is often necessary, partic- ularly with smaller patients. Similarly, ophthal- mic or microsurgical instrumentat ion may be indicated. Self-retaining retractors such as Gel- pi's are often helpful in coelomic procedures. An appropriately sized osteotome may be re- quired should pelvic girdle osteotomy be re- quired in large specimens.

Surgical Procedures In general, surgical manipulation of the fish is

little different f rom that of terrestrial verte- brates. The basic surgical axioms apply: know the anatomy; control hemorrhage; use a gentle touch when manipulating tissue; and, if you don ' t know what it is, don ' t cut it. The most problematic of these axioms is knowledge of the

Figure 2. Celiotomy in a starry flounder (Platichthys steUatus). Note the clear plastic drape used to isolate the surgical site, the retractor employed for maximum exposure, and the multicentric neoplasm of uncertain origin.

Page 7: FISH SURGERY

252 Michael J. Murray

anatomy. Although fish do tend to follow a rel- atively well-conserved vertebrate anatomic pat- tern, there is t r emendous variation in the spe- cific ana tomy across piscine taxa. It is therefore incumben t upon the pract i t ioner to gain a thor- ough knowledge of the anatomy through post m o r t e m examinat ions of similar specimens and reviews of appropr ia te ana tomy texts.

Historically, most of the surgical references to fish have involved ei ther the implantat ion of telemetry devices or the nonlethal collection of biopsy specimens by non-veterinarians. Over the past decade, in large par t due to the p ioneer ing work by Lewbart, Harms, Noga, Stoskopf, and others, a variety of surgical procedures have been documen ted in the veterinary litera- ture. 1,~,9,16q9 It is beyond the scope of this manu- script to review each of the publ ished references to piscine surgery. Instead, the reader is directed to cited references to specific surgical proce- dures for more detailed information.

Surgery of the Integument

A large n u m b e r of the fish surgeries carried out in private veterinary practices involve the removal of cutaneous masses. In many cases, these masses are in fact neoplastic. One may use a combinat ion of radiosurgery and cold steel in at tempts to remove these masses. In most cases a wide margin of tissue should be removed. Be- cause of the fish's tightly adhe ren t skin and min- imal subcutis, closure of these skin defects is often impossible. Therefore , second-intention healing is generally necessary. Topical antimi- crobials, such as silver sulfadiazine cream, ,nay be used postoperatively. Larger defects may be associated with exuberan t loss of fluid and elec- trolytes, the effects of which may be partially mit igated by increasing the salinity of the water system to 1-3 g / L (in freshwater systems).1

Laparoscopy

Although the use of endoscopy in fish is not a novel idea, the recent introduct ion into most veterinary clinics of quality, rigid, rod-lens sys- tems has made its use more practical. The indi- cations for laparoscopy in fishes mir ror those described for o ther species: sex identification in m o n o m o r p h i c or juvenile specimens, manage- men t of reproduct ion, examinat ion of coelomic viscera and collection of diagnostic specimens,

removal of foreign bodies, and the per formance of minimally invasive surgical techniques (Fig 3) .20

As with any other species, laparoscopy should be carried out using aseptic technique. The typ- ical insertion points for laparoscopy are deter- mined by the anticipated anatomic "target" as well as the anatomy of the fish under consider- ation (Fig 4, 5). The tightly packed, relatively fusiform shape of most fish precludes adequate visualization without some form of abdominal distension (Fig 6, 7). Tradit ional insufflation with carbon dioxide gas is the prefer red tech- nique; however, the author has used room air in numerous cases without incident.

A Veress needle is typically used for insuffla- tion into the per i toneal (or coelomic) cavity. It has a spring-loaded blunt obtura tor that is de- pressed and moves out of the way as the needle passes th rough tissue, yet it springs into place to protect the viscera once a cavity has been en- tered. The needle may be in t roduced at a 45 ~ angle near the targeted entry point (Fig 8). It is often preferable to make a small stab incision through the skin to facilitate p lacement of the needle. As the needle is advanced into the coe- lomic cavity, a discernible "pop" will be felt. It is exceptionally impor tan t to advance the needle carefully to prevent iatrogenic t rauma to viscera (Fig 9).

Figure 3. Collection of liver biopsy specimens from the liver (arrow) in the leopard shark (Triakis semifas- ciata) is generally not associated with substantial hem- orrhage.

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Fish Surgery 253

Figure 4. With a more lateral approach, the cranial aspect of the swim bladder (SB) is visible adjacent to the liver (L) in this Pacific mackerel (Scomberjaponi- s ,

Once the needle is in place within the coe- lom, the cavity may be insufflated to a pressure of 10 mm Hg. The needle may then be removed from the pressurized coelom. The 45 ~ tunneling through the body wall tends to prevent excessive loss of pressure. A trocar and sleeve may then be placed through the track created by the Veress needle. Again, caution must be exercised as this sleeve is placed. With the trocar removed, an appropriately sized rigid telescope may be in- serted.

Figure ~. Pyloric ceca (arrow) in Pacific mackerel (Scomberjaponicus) are also present in salmonid fishes.

In cases requiring multiple puncture ap- proaches, a second trocar/sleeve may be intro- duced. Should this be necessary, it is recom- mended that the entry point be planned to ac- commodate anatomy in conjunction with the need to triangulate between the second port, the telescope, and the target organ. Initial violation of the skin may be made with a scalpel blade, and a partial thickness dissection through the body wall made with fine mosquito forceps. The final placement of the second trocar/sleeve should be visualized with the telescope.

At the completion of the laparoscopic proce- dure, as much gas as possible should be removed from the body cavity with digital manipulation

Figure 6. A panoramic view of the coelom of a rock- fish (Sebastes spp) in dorsal recumbency. The liver is the dominant organ (white arrow) in this view. Large quantities of abdominal fat (black arrow), commonly encountered in captive specimens, are also promi- nent.

Figure 7. The tightly compacted visceral mass (larger black arrow) in the koi is difficult to manipulate en- doscopically. One typically sees multiple tendrils of connective tissue (white arrow) spanning the space between the viscera and the body wall and ribs (small black arrow)

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254 Michael J. Murray

Figure 8. Veress needle (white arrow) inserted on the midline near the pectoral fins of a leopard shark (Triakis semifasciata). In this instance, a second portal of entry is being made caudally. Anesthesia is being delivered via the clear tube inserted in the shark's mouth.

and pressure. The skin defects may then be closed routinely. Any residual gas remaining within the coelom should be absorbed relatively rapidly over several days. In those cases, aquar- ium furni ture should be placed in the recovery tanks to allow the fish to "wedge" itself to main- tain a comfortable posture for itself within the water column.

Celiotomy

In most cases, the surgical approach to the coelom of the fish is through a ventral midline incision. The incision extends f rom the caudal aspect of the pectoral girdle to approximate ly 1 cm cranial to the vent, depending upon the size of the fish. 1 Should additional exposure be re- quired, an os teotomy of the pectoral girdle may be carried out ei ther with an os teotome in larger specimens or simply with blade/scissors in smaller ones. The ventral midline may be fur- ther ex tended laterally if necessary. Use of self- retaining retractors such as Gelpi 's is often nec- essary for good exposure to coelomic viscera.

As previously indicated, a large body of pub- lished informat ion is available regarding the col- lection of biopsy specimens using nonlethal techniques, especially in sahnon fishes. One such technique is a lateral approach to the liver. 7 Access to the liver is made through an incision made just caudal to the opercu lum and dorsal to the pectoral fin (Fig 10). In most cases, an inci- sion length of 5-7 cm provides adequate expo- sure to the lateral aspect of the liver.

A similar technique for exposure of the dor- sally placed kidney has also been described. 7 In this instance the incision is started midway be- tween the lateral line and the left pelvic fin with care taken not to incise across the lateral line. The incision is then cont inued caudally and ven- trally to a poin t midway between the vent and the caudal bo rde r of the pelvic fin. With blunt dissection, retraction, and compression of the swim bladder, the caudal aspect of the left kid- ney may be exposed (Fig 11). The caudal pole of the swim bladder may need to be teased away f rom its a t t achment to the kidney; however, such dissection should be conservative. A Backhaus towel c lamp may be used to hold a sterilized stainless steel washer, which may then be placed upon the swim bladder as an aid in compres- s ion/re t ract ion. When carrying out renal biop- sies, one should a t tempt to collect small samples and recognize (and avoid if possible) the opis- thonephr ic ducts draining the kidneys.

Closure of the body wall is typically straight- forward. Depending upon the size of the fish and the thickness of the body wall, ei ther a single- or a double-layer closure may be used. In the first case, both the skin and muscle are in- corpora ted in the closure. Skin and muscle are closed separately in the double-layer technique (Fig 12). The suture pat tern employed is depen- dent upon personal preference. A continuous

Figure 9. Veress needle in place within the coelom of a rockfish (&bastes spp). The arrow points to the beveled edge of the sharp needle, which is protected by the retractable trocar once the needle enters the body cavity.

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Figure 10. With retractors, the liver (white arrow) and stomach (black arrow) are easily approached in the black rockfish (&bastes melan- o p s ) .

pa t te rn is adequa te in mos t cases, bu t inter- r up t ed sutures are similarly successful. Surgical staples have b e e n used successfully in bo th fresh- water and mar ine species. T h e na ture o f fish skin is such that p r o p e r p l acemen t o f staples is difficult, and surgical staples are therefore n o t of ten used.

Despite references to the contrary, the use o f cyanoacrylate adhesives is no t r e c o m m e n d e d , since they of ten incite a severe dermatitis. 9 In addi t ion, incisions closed with cyanoacrylate ad-

hesives have a h igher inc idence o f dehiscence than those closed with sutures. 91 This is no t sur- pris ing because cu taneous goble t cells p r o d u c e mucus , the p resence o f which adjacent to the incision site u n d e r m i n e s and elevates the adhe- sive, resul t ing in dehiscence.

Postoperative Management Recovery f rom an anesthet ic p r o c e d u r e may

be a p ro t rac ted event, part icularly when inject-

Figure 11. A caudal, lateral approach to the coelom exposes the compressed swim bladder (SB), abdomi- nal fat bodies (F), a loop of small intestine (SI), and the caudal pole of the kidney (K) in the black rockfish ( S&astes melanops).

Figure 12. Closure of a celiotomy incision in the starry flounder (Platichthys steUatus). The right hand aspect of the figure demonstrates the closure of the body wall, and the left side demonstrates skin closure; each is done in separate layers.

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256 Michael J. Murray

able agents are used (see Table 3). In the case of inhalant anesthesia, it is r e c o m m e n d e d that the "anesthetic setting" be turned down towards the end of a p rocedure that has been ei ther lengthy or has involved greater anesthetic depth. This may be accompl ished by ei ther diluting the con- centrat ion of anesthetic in the reservoir or by changing the over-the-gills infusion to ambien t water.

Postanesthetic fish should be permi t ted to recover totally in a recovery tank that is not its pr imary enclosure. This tank should be free of obstacles or furni ture that may injure or entan- gle the patient. Obviously, the water-quality pa- rameters should be appropr ia te and consistent with those found in the fish's pr imary tank. The fish should be gently restrained as it is placed in its recovery tank. Water flow should be directed into the pat ient 's oral cavity to facilitate resusci- tation as the gills are perfused. One may need to physically propel the fish fotavard to accomplish this perfusion for some specimens. The fish should not be pulled backwards because this dramatically decreases respiratory efficiency and may damage the gill filaments.

As the fish regains consciousness, there is an increase in jaw tone and opercular movements . Caution should be pract iced a round the oral cavity of fish with potentially dangerous teeth because jaw tone and biting may occur before the re turn of opercular movements . Once strong respiratory movements are detected, the fish should be released into the water column, even though it may not have regained its normal posture. The fish should be allowed to recover in a dimly lit, quiet area to minimize stress and to facilitate a more gentle recovery period. The recovery f rom some anesthetic agents may be ra ther violent and involve uncontrol led swim- ming and even porpois ing in the tank. Obvi- ously, ways of prevent ing injury should be con- sidered.

Some anecdotal evidence suggests that hypox- emia may be somewhat persistent following MS- 222 or eugenol anesthesia in freshwater fish. 22 For this reason ensuring adequate or even slightly elevated oxygen saturation of recover systems may be advantageous. One must bear in mind, however, that p ro longed exposure to dra- matically elevated levels of oxygen may result in damage to gill filaments.

There is an ongoing debate as to the ability of fish to exper ience pain. As a result, the indica- tion for postoperative analgesia is also debat- able. Despite the uncertainty, it seems appropri- ate that the clinician should err on the side of the pat ient and administer analgesics in those cases for which postoperative pain m a n a g e m e n t would be appropr ia te in o ther species. When adminis tered before cessation of anesthesia, bu- torphanol (0.4 m g / k g intramuscularly or subcu- taneously) produces no untoward effects. In fact, butorphanol- t rea ted koi re turned to nor- mal swimming and began eating sooner than koi given a placebo. 23

As in mammal ian patients, the administrat ion of postoperative antibiotics is controversial. It is agreed, however, that antibiotics are not a pan- acea for poor surgical technique. Because most piscine surgical techniques are not truly aseptic as a consequence of limited skin preparat ion, some prophylactic antibiotic administrat ion is probably justified. Generally, a single adminis- tration of a broad-spect rum antibiotic such as amikacin, enrofloxacin, or ceftazidime is ade- quate. One must bear in mind that most antimi- crobials are not approved for use in "food fish," and therefore only approved products should be used in those specimens that may ultimately be consumed by humans (eg, oxytetracycline hy- drochloride, 10 m g / k g intramuscularly). 1 One may also apply a thin layer of a povidone-iodine o in tment to the incision site to discourage the growth of fungi as healing proceeds. 1

The remainder of the recovery per iod should be relatively straightforward. Postoperative anti- biotics or analgesics should be cont inued as in- dicated. Water quality parameters within the re- covery area should be moni to red and main- tained. The elevated oxygen saturation of the system may be gradually reduced over t ime as well. One should not overlook the potentially detr imental effects of "exposure" in a recovery tank. Many fish benefi t f rom the provision of adequate hiding places and visual security once they have recovered f rom the effects of the an- esthetic.

As the numbers and the value of captive fish increase, the potential indications for surgical intervention in fish will increase. Although the concept of "out-of-water" surgery in this group of animals may be initially intimidating, fish are actually excellent surgical candidates. The clini-

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c l an m u s t b e a w a r e o f t h e i n t r i c a c i e s o f f i sh

a n e s t h e s i a a n d a n e s t h e t i c m o n i t o r i n g , h o w e v e r .

T h a t , c o u p l e d w i t h a s o u n d k n o w l e d g e o f t h e

p a t i e n t ' s a n a t o m y , s h o u l d a l low t h e p r a c t i t i o n e r

to a p p r o a c h f i sh s u r g e r y w i t h a m i n i m u m o f

t r e p i d a t i o n .

References 1. Harms CA, Lewbart GA: Surgery in fish. Vet Clin North

Am Exot Anim Pract 3:759-774, 2000 2. Stoskopf MK: Surgery, in Stoskopf MK (ed): Fish Medi-

cine. Philadelphia, PA, Saunders, 1993, pp 91-97 3. Helm WT, Tyus HM: Influence of coating type on reten-

tion of dummy transmitters implanted in rainbow trout. North AmJ Fish Manage 12:257-259, 1992

4. Martin SW, Long JA, Pearsons TN: Comparison of sur- vival, gonad development, and growth between rainbow trout with and without surgically implanted dummy ra- dio transmitters. North Am J Fish Manage 15:494-498, 1995

5. Mare/ GD, Summerfelt RC: Pathways and mechanisms for expulsion of surgically implanted dummy transmit- ters from channel catfish. Trans Am Fish Soc 115:577- 589, 1986

6. Summerfelt RC, Smith LS: Anesthesia, surgery, and re- lated techniques, in Schreck CB, Moyle PB (eds): Meth- ods for Fish Biology. Bethesda, MD, American Fisheries Society,, 1990, pp 213-272

7. Wooster GA, Hsu HM, Bowser PR: Nonlethal surgical procedures for obtaining tissue samples for fish health inspections. J Aquat Anita Health 5:157-164, 1993

8. Harms CA: Anesthesia in fish, in Fowler ME, Miller RE (eds): Zoo & Wild Animal Medicine Current Therapy (vol 4). Philadelphia, PA, Saunders, 1999, pp 158-163

9. Lewbart CA, Stone EA, Love NE: Pneumocystectomy in a midas cichlid. J Am Vet Med Assoc 207: 319-321, 1995

10. Lewbart GA, Harms CA: Building a fish anesthesia de- livery system. Exot DVM 1:25-28, 1999

11. Sladky KK, Swanson CR, Stoskopf MK, et al: Comparative efficacy of tricaine methanesulfonate and clove oil for

use as anesthetics in red pacu (Piaractus brachypomus). Am J Vet Res 62:33%342, 2001

12. Brown LA: Anesthesia and restraint, in Stoskopf MK (ed): Fish Medicine. Philadelphia, PA, Saunders, 1993, pp 79-90

13. GemmaJM, Dunn JL, Lewbart GA, et al: Evaluation of the anesthetic effects of eugenol with varying ratios of eugenol to ethanol in killifish (Fundulus heteroditus). Proc Am Assoc Zoo Vet and Int Assoc Aquat Anim Med Joint Conf, New Orleans, LA, 2000, pp 386-387

14. Mitchell MA, Miller S, Heatley JJ, et al: Clinical and cardiorespiratory effects of propofol in the spotted bam- boo shark ( Chylloscyllium plagiosum). Proc 26th Annu Am Coll Vet Anesthesiol, New Orleans, LA, 2001

15. Hurty C, Brazik D, LawJM, et ah Histologic evaluation of the tissue reaction to five suture materials in the body wall ofkoi (Cyprinus carpio). Proc Am Assoc Zoo Vet and Int Assoc Aquat Anita MedJoint Conf, New Orleans, LA, 2000, p 510

16. Harms CA, Bakal RS, Khoo LH, et ah Microsurgical excision of an abdominal mass in a gourami. J Am Vet Med Assoc 207:1215-1217, 1995

17. Miller SM: Surgical excision of a schwannoma in a buf- falo sculpin. Exotic DVM 2.2:41-43, 2000

18. Nadelstein R, Bakal, R, Lewbart GA: Orbital extenera- tion and placement of a prosthesis in fish. J Am Vet Med Assoc 211:603-606, 1997

19. Lewbart GA, Spodnick G, Barlow N, et ah Surgical re- moval of an undifferentiated abdominal sarcoma from a koi carp (Cyprinus carpio). Vet Rec 143:556-558, 1998

20. Murray MJ, Schildger B, Taylor M: Endoscopy in Birds, Reptiles, Amphibians, and Fish. Tuttlingen, Germany, Endo-Press, 1998, pp 59-75

21. Petering RW, Johnson DL: Suitability of a cyanoacrylate adhesive to close incisions in black crappies used in telemetry studies. Trans Am Fish Soc 120:535-537, 1991

22. Chittick EJ, Lewbart GA, Swanson C: Post-anesthetic hy- poxemia in freshwater fish. Proc Am Assoc Zoo Vet and Int Assoc Aquat Anita Med Joint Conf, New Orleans, LA, 2000, pp 372-373

23. Lewbart CA: Current approaches to anesthesia and an- algesia in fish. Proc Int Conf Exot, Fort Lauderdale, FL, 2001, pp 19-20.