PINNIPEDS
Under the Environment Protection and Biodiversity Conservation Act 1999, all marine mammal are protected in Australian waters. Interference or capture of free-ranging pinnipeds without a permit for any purpose other than rescue is illegal.
Under scientific licence, issued by the relevant state or territory, research may be conducted on free-ranging pinnipeds, which may involve capture and physical or chemical restraint. Gales et al. (2009) provide guidelines for the treatment of marine mammals in field research.12.1 Capture and physical restraint
The choice of capture and restraint method for free- ranging pinnipeds and those in managed care depends on species, age, sex, size and demeanour, availability and skill of personnel, ease of access to the animal, proximity to water and other hazards, ambient temperature and intent of the procedure. Capture in water is difficult and rarely attempted. Pinnipeds can be dangerous. Most can inflict severe bites if provoked and some, particularly otariids, are agile and fast. Working on large animals is physically demanding. Any procedure should be well planned and performed by experienced personnel. The environment may also present significant hazards, particularly in the field. Some pinniped species, fur-seals in particular, will often flee to water when approached (Barnes et al. 2008).
Several methods are used to capture and physically restrain pinnipeds (Table 9.5). Chemical restraint should be considered for larger pinnipeds, or for any pinniped where physical restraint alone is unlikely to achieve the desired outcome or is unsafe. Administration of a sedative (see Appendix 3) before capture can assist physical restraint in situations where anaesthesia is undesirable. For smaller seals, physical restraint alone can be used to facilitate minor procedures such a venipuncture, diagnostic sample collection, hand injection of chemical restraint agents or medications, force- or assisted feeding, microchipping, tagging, tuberculosis testing or mask induction of inhalation anaesthesia.
An advantage is that the animal can immediately be released without residual effect of chemical restraint agents. Limitations include limited duration, poor accessibility to some body parts, lack of analgesia, risk to animal and personnel and stress on the seal. Ambient temperature is an important consideration during any capture and transport of pinnipeds, as they are unable to use their normal behavioural means ofTable 9.5. Capture and physical restraint methods used in pinnipeds (Barnes etal. 2008; NHMRC 2014)
| Method | Technique | ||||||||||||||||||||||||
| Herding boards | Large, solid, smooth timber or plastic boards with handles. Used to move seals from one area to another, into a crate or squeeze cage, or block a seal from entering water or other area while providing protection for personnel. Injections (hand, pole syringe) can be given with animals pinned against a barrier | ||||||||||||||||||||||||
| Head bag | Conical hessian or ventilated canvas bag on a hoop placed over the animal's head, with or without a hole at the apex through which the muzzle protrudes; if long enough can also restrain pectoral flippers; smaller animals can be captured using the bag and then straddled to restrain. Head bags reduce visual stimuli and are also useful for anaesthetised seals (Fig. 9.10) | ||||||||||||||||||||||||
| Sausage nets | Long, large conical mesh net with wide opening (1 m) and flexible hoop; narrow apex with drawstring that can be opened to release the seal from the net; useful for phocids (Fig. 9.11) | ||||||||||||||||||||||||
| Hoop nets | Net size appropriate to size of seal; conical or tubular nets with a hole at the apex through which the muzzle protrudes are ideal; the body of the net should have a small mesh size (agents this tolerance cannot be relied on and hypoventilation will contribute to morbidity and mortality during pinniped anaesthesia. If not already intubated, the anaesthetist must be prepared to intubate and assist ventilation if hypoventilation becomes apparent. Either manual or mechanical intermittent positive pressure ventilation is often required to ensure adequate ventilation.
Fig. 9.11. Long, conical sausage net being used to capture a leopard seal (Hydrurga Ieptonyx). The hoop is placed in front of and then over the animal. As the animal moves forward into the net it becomes entrapped. A head bag is placed and the animal is then physically restrained. Photo: Taronga Zoo The effect of the dive response in pinnipeds and other aquatic mammals in relation to anaesthesia is poorly understood. The dive response is a group of physiological changes that occur during submersion in water and it has been described in a wide variety of aquatic and terrestrial vertebrate species. The changes consist of apnoea, bradycardia and compensatory redistribution of blood to the heart and CNS by peripheral vasoconstriction and pooling of blood in the caudal vena cava and hepatic sinus (Panneton 2013). Marine mammal anaesthesia poses several challenges (Table 9.6). It seems likely that anaesthetic-related mortalities may be at least in part associated with these other anaesthetic complications, rather than the influence of the dive response (Macgregor et al. 2014). Free-ranging pinnipeds are frequently presented in a debilitated state, often with wounds, injuries and high parasite burdens (particularly juveniles). Parasitic pneumonia may compromise ventilation during anaesthesia, and heavy hookworm burdens may result in significant anaemia and hypoxaemia (Haulena 2014). Some require chemical restraint for investigation or treatment. An indication for chemical restraint in seals housed in managed care is often investigation and treatment of illness. In a study of California sea-lions (Zalophus californianus) by Stringer et al. (2012), poor health status was associated with increased risk of anaesthetic-related mortality. This has been the author’s experience and that of others with anaesthesia of Australian pinnipeds.The use of atropine has historically been suggested to prevent and manage bradycardia in anaesthetised pinnipeds; however, there appears to be no benefit using it and has also been implicated as a risk factor in peri-anaesthetic mortality (Barnes et al. 2008; Stringer et al. 2012). Key considerations and risks for chemical restraint are covered in Table 9.6. Chemical restraint drugs and doses are included in Appendix 3. 12.2.1 Sedation Sedation before physical restraint for various procedures, including anaesthetic induction, is often beneficial (see Appendix 3). Sedation of pinnipeds held in managed care trained for hand injection may facilitate minor procedures (venipuncture, other sampling, insertion of contraceptive implants, catheter placement, tuberculosis testing, mask induction of inhalation anaesthesia) without the need for physical restraint.
Fig. 9.12. (a) Purpose-made seal restraint nets typically have a lightweight aluminium handle/hoop and 6-mm non-abrasive nylon netting for the body. The body of the net narrows, so that the animal can be moved towards the apex. (b) Juvenile Australian fur seal (Arctocephalus pusillus) restrained in a hoop net for removal of polypropylene fishing gear entanglement. The fore flippers are pinned against the trunk and the seal grasped behind the head. To allow access to the animal's head, a double-ended zipper positioned at the apex can be opened and the net is rolled back. Photos: Zoos Victoria 12.2.1 Anaesthesia A range of injectable anaesthetic agents has been used in Australian pinnipeds (see Appendix 3). Isoflurane or sevo- flurane in oxygen, administered via mask, is used in pinnipeds that can be safely physically restrained, or sedated and then physically restrained. Intubation is recommended if pinnipeds are to be maintained on inhalation anaesthesia rather than via a mask. The use of inhalation anaesthesia in remote field situations can be complex because the equipment can be cumbersome and in cold climates thermal management of the anaesthetic machine is required. Inhalation anaesthesia is considered safer than injectable for supplementation and maintenance, as the drug dose can be titrated to effect. Baylis et al. (2015) suggest that safety of tiletamine/zolazepam anaesthesia in otariid seals is improved when the induction dose is used to produce light anaesthesia and anaesthesia is then supplemented and maintained using inhalational agents. A multimodal approach to surgical anaesthesia and analgesia was used in a long-nosed fur seal (Arctocephalus forst- eri). The objectives were to provide multimodal surgical analgesia during a laparotomy; minimise cardiorespiratory depression and hypotension during anaesthesia; and facilitate a rapid, smooth recovery. At commencement of surgical preparation, a loading dose of fentanyl (2 μg∕kg) was given IV. A combined continuous rate infusion of fentanyl (2 μg∕kg∕hr), ketamine (0.3 mg/kg/hr) and lignocaine (1 mg∕kg∕hr) was administered via a secondary IV fluid line and syringe pump. The CRI was administered for the full duration of the surgery. Low-end canine dose rates were selected for each drug in the CRI due to the animal's poor health status at the time of the procedure. For post-operative analgesia, transdermal fentanyl patches were applied (equivalent to 50 μg∕kg∕hr), and a dose of methadone (0.2 mg∕kg) was given IM during anaesthetic recovery. Subjectively, adequate intraoperative and postoperative analgesia appeared to be achieved with this approach, based on clinical observations. Remifentanil CRI’s at 0.2-0.4 μg∕kg∕min have also been used in fur seals undergoing laparotomy procedures (C Cheng pers. comm.). Remifentanil has a shorter half-life than fentanyl, facilitating faster recoveries from anaesthesia.Standard monitoring equipment can be used. Pulse oximeter clips tend to slip off the short, thick tongue (particularly otariids). Probes are placed on the nasal septum, lip, penis, prepuce or vulva. Reflectance probes can be Table 9.6. Key considerations and Tiskfactorsforthechemical Testraintofpinnipeds (Barnes etal. 2008; Haulena 2014; Lynch and Bodley 2014;Trumbull etal. 2021)
π> Table 9.6. (continued)
placed rectally, vaginally or along the buccal or gingival mucosa. Capnometry is essential and standard equipment that samples expired gases from an endotracheal tube can be used. Capnometry using a small in-line capnometer attached to a face mask proved extremely useful in measuring ETCO2 and respiration rate in anaesthetised leopard seals (Vogelnest et al. 2010) (Fig. 9.13). Capnometry is essential with mechanically assisted ventilation to adjust tidal volume and rate to maintain normocapnoea (Haulena 2014). Oral mucosal colour and capillary refill time should be monitored. Flexible temperature probes are inserted at least 10 cm into the rectum or into the oesophagus to the level of the heart for more accurate core temperature readings (Haulena 2014). Hypotension is common in anaesthetised pinnipeds and likely contributes to poor anaesthetic outcomes. Blood pressure is difficult to monitor in pinnipeds. Non-invasive indirect blood pressure cannot be reliably measured due to challenges of using oscillometric cuffs on pinniped extremities. Indirect methods of arterial blood pressure monitoring have not yet been validated in pinnipeds (Bailey et al. 2013). The placement of arterial catheters can be achieved in the median artery in otariids and the superficial plantar metatarsal artery in phocids using ultrasound guidance (Trumbull et al. 2021). A retrospective case review found seven pinniped cases that demonstrated anaesthesia-associated hypotension diagnosed by direct blood pressure measurements (Trumbull et al. 2021). Treatment of hypotension in pinnipeds has included dobutamine (0.2-2.0 μ∕kg∕m IV) and dobutamine with
Fig. 9.13. Measurement of end-tidal CO2 and respiration rate in an anaesthetised leopard seal (Hydrurga Ieptonyx) using a small in-line capnometer attached to a face mask. Note the animal's head is covered with a bag to reduce visual stimulation during light anaesthesia. ephedrine (0.05 mg/kg IV) or ephedrine alone (0.1-0.2 mg∕kg). Dobutamine CRI at 1 μg∕kg∕min was used in response to a decreasing trend in blood pressure in a longnosed fur seal (C Cheng pers. comm.). 13. More on the topic PINNIPEDS:
-
Veterinarian -
|
