Fluids
Various models have been used to investigate nociception, and nociceptive receptors are present in fish, predicating the importance to minimize noxious stimulations associated with fish surgery (Weber 2011a). The use of a perioperative opioid drug is currently recommended. Morphine 5 mg/kg intramuscularly (IM) has been proposed in koi (Cyprinus carpio) (Baker et al. 2013). Morphine at this dose caused temporary bouts of excitability and, if used, owners should be made aware of potential adverse effects (Baker et al. 2013). The pharmacokinetics of morphine have also been reported in goldfish (Carassius auratus) and salmon (Salmo salar) administered, respectively, 40 and 100 mg/kg IM and mean elimination half‐lives were 12.5–13.5 hours (Nordgreen et al. 2009). Nonsteroidal anti‐inflammatory drugs are used as part of multimodal analgesia in fish. Ketoprofen (Harms et al. 2005; Davis et al. 2006; Ward et al. 2012), carprofen (Mettam et al. 2011), and meloxicam (Larouche 2018; Fredholm et al. 2016) have been evaluated in fish. Adverse effects of other non steroidal anti‐inflammatory drugs have been reported and empirical use at high doses should be avoided (Schwaiger et al. 2004; Lovy et al. 2007). In‐depth reviews of fish anesthesia are available (Stoskopf and Posner 2014; Whiteside 2014). Perioperative fluids are chosen based on the plasma osmolarity of the species, ranging between 900 and 1500 mOsm/l in elasmobranchs (Hadfield et al. 2010).
Antibiotics
Only a few antibiotics are approved for specific species use in aquaculture, and these vary by country (Health Canada 2010; Tell et al. 2012). A growing number of pharmacokinetic studies evaluate therapeutic antibiotic use in ornamental fish (Nouws et al. 1988; Grondel et al. 1986; Lewbart et al. 1997; Yanong et al. 2011; Grosset et al. 2015).
Figure 5.1 (a) Positioning for a CT‐scan in an anesthetized koi (Cyprinus carpio) presented with an inability to close the mouth. The koi is kept anesthetized via a water‐circulating system over the gills and irrigation of the skin is provided with a syringe just before a very quick image‐acquisition period. Care should be taken to avoid any water leakage with the use of absorbing towels and foam. (b) Example of a CT‐scan of a koi (Cyprinus carpio) patient that presented for an inability to close the mouth: longitudinal section showing the ossicles (arrows), the globes (g), and opercular cavity (*).
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Surgical Table
Most fish surgeries are performed out of the water to facilitate visualization, tissue dissection, and suturing (Wildgoose 2000). Surgery tables adapted for fish should include a recirculating water system and a support element for the patient (Weber et al. 2009). The support element is typically made of nonabrasive material to preserve cutaneous mucus and should be permeable to allow water used for irrigation of the gills to return to a container placed underneath the table for recirculating systems (see Figure 5.2). For laterally compressed fish, a V‐shaped foam tray is useful to keep the fish in dorsal recumbency. Irrigation of the gills is performed using a Y‐shaped perforated tubing or two tubes connected to submersed pumps as previously described (Figure 5.2) (Weber et al. 2009; Mylniczenko et al. 2014). If an oral cavity procedure is performed, the tubing may be placed with retrograde flow in each opercular cavity with water irrigating the gills from their caudal aspect (Figure 5.3) (Mylniczenko et al. 2014).
Figure 5.2 Anesthetic equipment used for a large 8 kg koi (Cyprinus carpio) anesthetized for a surgical procedure: a Doppler probe protected by a glove filled with conducting gel is placed in the left opercular chamber for heart rate monitoring and two tubes, each connected to a submersible pump are placed in each opercular cavity.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Figure 5.3 Intervention in the oropharyngeal cavity of a Ranchu goldfish (Carassius auratus): a suture from a previous incisional biopsy is visible on the mass extending from the left commissure to left side of the face, ventral to the left eye. Irrigation of the gills is achieved with tubing placed caudally in each opercular cavity, which allows maintenance of anesthesia.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Surgical Modalities
Modalities such as cryosurgery and CO2 laser have been used extensively in fish for mass ablation (Figure 5.4) (Francis‐Floyd et al. 1993; Harms et al. 2008; Boylan et al. 2015). These modalities improve hemostasis but do not allow for histologic evaluation and no study has demonstrated superior results using these modalities in fish. Protocols are extrapolated from those used in mammals. Hand‐held electrocautery can be used for hemostasis, but electrosurgery should not be used due to the omnipresence of conductive water (Figure 5.5).
Wounds
Wound healing has been studied extensively in zebrafish (Danio rerio) (Rapanan et al. 2015). Fish have exceptional regenerative capability (Ochandio et al. 2015). Fish skin has intrinsic healing properties, and products derived from fish skin are under investigation for xenografts (Baldursson et al. 2015). Healing time depends on environmental parameters such as water temperature, alkalinity, pH, salinity, and photoperiod (Andrews et al. 2015). Skin healing may take months in a cold‐water species. Keeping the patient at the higher end of its temperature range hastens healing time (Andrews et al. 2015; Ang et al. 2021).
