Oiled Sea Otter Capture Course

Treating the Medical Disorders of Oiled Sea Otters

Oiled otters brought to rehabilitation centers present a wide range of medical conditions varying in severity (Williams and Davis, 1990). During the first weeks following the EVOS, more than 36% of the captured sea otters were hypothermic, 27% were hyperthermic after transport, and more than 45% of the animals showed blood glucose concentrations below the minimum normal value (88 mg/ dl; Appendix 3 Download PDF). Also, nearly 70% of the otters that died during this period exhibited some form of emphysema.

Otters oiled during the first three weeks of a catastrophic spill show the severest medical problems, and consequently the highest mortality. As the oil dissipates and weathers, the incidence and severity many medical disorders will decline. Therefore, treatment regimes differ for otters contaminated during the Early and Late Phases of a spill.

Treatments for Early Phase Sea Otters

Otters arriving at the rehabilitation center during the Early Phase of an oil spill will require treatment for external and internal exposure to oil. Medical problems caused by exposure to oil will be exacerbated by the stress of capture, handling, and rehabilitation. However, it will be difficult to differentiate between the detrimental effects of oiling and the stress of captivity when treating oiled otters.

Treatment of Early Phase otters should begin during the cleaning process. The animals should be weighed and then sedated as required for handling. An ophthalmic ointment (Bacitracin) should be applied to the eyes to protect them from detergent and oily water. The flexible probe of an electronic digital thermometer should be inserted fifteen cm into the rectum to monitor core temperature.

Animals with core temperatures below 35°C (95°F) should 1 treated for severe hypothermia (see Chapter 5 for details). This procedure includes the intravenous infusion of warm (37-39°C or 98.6-102°F) fluids and warm water (37°C or 98.6°F) immersion. The animal’s vital signs (respiratory rate, heart rate, blood oxygen saturation) should be monitored during rewarming. A portable electrocardiograph (EKG) and pulse oximeter with a flexible probe that can be attached to the animal’s tongue are essential for monitoring heart rate and blood oxygen saturation, respectively. Ventricular arrhythmias and tachycardia may be treated with lidocaine hydrochloride (1-2 mg/kg IV bolus); atrial arrhythmias are controlled with propranolol (0.02-0.06 mg/kg slow IV infusion). Caution should be used when administering these drugs to hypothermic anima because over-medication can occur when the animal rewarms Hyperthermic otters (core temperature greater than 40°C or 104°F) should be cooled by placing ice packs on the hind flippers and by reducing the rinse water temperature to 10°C (50°F) during washing.

Hypoglycemia (plasma glucose less than 60 mg/ dl) should be treated with 5% dextrose (20 ml/kg SQ) or 10-20% dextrose (10-20 ml/kg IV to effect). For a more sustained effect, a 50% dextrose solution (1 ml/kg) should be given by stomach tube; this is followed by the subcutaneous infusion of 5% dextrose to maintain the blood glucose concentration at normal levels.

Oiled sea otters may be washed while their core temperature and blood glucose are being stabilized. Rinse water temperature should be adjusted to help maintain the otter’s core temperature at 37-39°C (98.6-102°F). During rinsing, prophylactic fluid therapy for dehydration (normal saline or a 1-to-1 mixture of 5% dextrose solution and normal saline; 20 ml/kg/ day) should be initiated with a subcutaneous line inserted between the shoulders or the loose skin behind the neck. Antibiotics, dexamethasone, and vitamin/ mineral supplements should be administered as described under the previous section on stabilization.

Fecal samples are easily collected while the otters are being washed and may be used to assess the ingestion of crude oil by suspending the sample in water. To mitigate the effects of ingested oil, all animals from the Early Phase of a spill may be treated with a petroleum hydrocarbon adsorbent. A slurry of activated charcoal (Toxiban TM, 6 ml/ kg) can be administered via stomach tube just prior to anesthetic reversal after cleaning. Care must be taken to prevent aspiration and gastric reflux during intubation. (See Petroleum Hydrocarbon Ingestion and Exposure in Chapter 5 for more details.)

Sea otters that are exposed to oil during the Early Phase of a spill may exhibit signs of respiratory distress associated with interstitial or subcutaneous emphysema. This condition may be diagnosed during physical examinations. The axillary area and neck of the otters should be palpated and the presence and location of subcutaneous air recorded on the animal’s medical chart. Crepitation in the axillary areas is an indicator of serious pulmonary damage (see Injuries to the Respiratory Tract in Chapter 5). Pulmonary distress, including hyperventilation, congested nasal passages, and diaphragmatic breathing, should also be noted. The interstitial form of emphysema can be confirmed only by radiography or during necropsy. Treatment of this condition is limited to supportive care. Diazepam (0.2 mg/kg PO or 0.1 mg/kg IM) may be administered to calm excited or agitated otters that exhibit labored breathing or hyperventilation. Diazepam should never be given to otters that show symptoms of shock. Positive pressure inhalation anesthetics or gases are contraindicated for otters with pulmonary disorders.

Treatments for Late Phase Sea Otters Sea otters contaminated during the Late Phase of a spill usually benefit from a twenty-four to thirty-six hour rest period before cleaning and treatment (see Chapter 11). Late Phase otters that have encountered light sheen oil that does not penetrate the underfur or disrupt the insulating air layer do not require cleaning. These otters should be placed in a holding pool for observation. If the otter’s fur appears normal and maintains its insulating properties, then the animal should be moved to a prerelease facility as soon as possible after physical examination and blood sampling (see Chapter 12). Sea otters are able to remove small amounts of crude oil from the surface of their fur during normal grooming. However, it will be necessary to clean small patches of oil if it has penetrated the underfur.

It is unlikely that Late Phase otters have ingested oil in sufficient amounts to cause a toxic effect. Unless fecal and blood tests indicate otherwise, activated charcoal adsorbents should not be administered. Likewise, interstitial and subcutaneous emphysema are rarely ob- served in otters during the Late Phase of a spill. Because this group of animals is less prone to shock and hypothermia, organ congestion and tissue damage associated with circulatory collapse are rare. Treatment protocols should be conservative and based on the results of a physical examination, blood analysis, and behavior.