Abstract

Euthanasia of stranded large whales poses logistic, safety, pharmaceutical, delivery, public relations, and disposal challenges. Reasonable arguments may be made for allowing a stranded whale to expire naturally. However, slow cardiovascular collapse from gravitational effects outside of neutral buoyancy, often combined with severely debilitating conditions, motivate humane efforts to end the animal's suffering. The size of the animal and prevailing environmental conditions often pose safety concerns for stranding personnel, which take priority over other considerations. When considering chemical euthanasia, the size of the animal also necessitates large quantities of euthanasia agents. Drug residues are a concern for relay toxicity to scavengers, particularly for pentobarbital-containing euthanasia solutions. Pentobarbital is also an environmental concern because of its stability and long persistence in aquatic environments. We describe a euthanasia technique for stranded mysticetes using readily available, relatively inexpensive, preanesthetic and anesthetic drugs (midazolam, acepromazine, xylazine) followed by saturated KCl delivered via custom-made needles and a low-cost, basic, pressurized canister. This method provides effective euthanasia while moderating personnel exposure to hazardous situations and minimizing drug residues of concern for relay toxicity.

INTRODUCTION

Euthanasia of stranded large whales poses logistic, safety, pharmaceutical, publicity, and disposal challenges. Once a baleen whale strands, gravitational effects leading to respiratory and circulatory collapse (Geraci and Lounsbury 2005) leave little doubt as to the eventual outcome, although it may take several days for death to ensue (Daoust and Ortenburger 2001; Kolesnikovas et al. 2012). Allowing a stranded whale to expire naturally can be reasonably argued. However, slow cardiovascular collapse, often combined with severe skin blistering, live animal scavenging, hyperthermia, distress, or serious injury, typically motivate humane efforts to end the animal's suffering. Animal size and environmental conditions can pose safety concerns for stranding personnel. Delivery of euthanasia agents requires custom-made, long needles for intramuscular (IM) and intracardiac (IC) injection sites (Geraci and Lounsbury 2005). Blowhole delivery of pentobarbital can circumvent thick blubber layers and avoid the dangers posed by the flukes in unsedated animals (Dunn 2006). Free-swimming right whales (Eubalaena glacialis) have been sedated to facilitate disentanglement (Moore et al. 2010), but the concentrated drugs require expensive compounding and special permitting. Etorphine has been employed as an intramuscular euthanasia agent for stranded large whales in the UK (Barnett et al. 1999; Moore 2010), but personnel safety concerns in an already hazardous stranding environment and controlled drug restrictions have inhibited widespread adoption of ultrapotent opioids for this application.

Relay toxicity to scavengers is a hazard, particularly with pentobarbital-containing euthanasia solutions (Geraci and Lounsbury 2005; Bischof et al. 2011). Pentobarbital is an environmental concern because of its stability and persistence in aquatic environments (Eckel et al. 1993; Peschka et al. 2006). Ballistics may be used by trained individuals to avoid drug residue problems but are not recommended for larger cetaceans (Greer et al. 2001; Geraci and Lounsbury 2005, Moore 2010; AVMA 2013). Cranial implosion of large whales using shaped explosive charges has been refined in Australia (Coughran et al. 2012). This method requires specialized training and appropriate crowd control. Lack of public acceptance, access to explosives, and required training makes this technique unlikely for large whales in the US in the near term.

We describe five cases in which stranded mysticetes were euthanized by a series of preanesthetic and anesthetic drugs followed by an adjunct method, resulting in minimal drug residues of concern for relay toxicity, using inexpensive, readily available agents. Case 1 was not satisfactory, merely preferable to the whale's continued suffering, and compelled consideration of other strategies that were employed to good effect in Cases 2–5.

CASES

The euthanasia decision in all cases was reached in consultation with National Marine Fisheries Service (NMFS) authorities, based on injuries, progressive physiologic decompensation, scavenger damage, failure to self-rescue during high tides, maternal separation, or some combination of these factors. Pentobarbital was not an option because of relay toxicity concerns and the unlikely possibility of proper carcass disposal in remote locations (North Carolina, USA; Fig. 1). Intramuscular, retrobulbar, and intrathoracic injections were performed with custom 31-cm, 16-gauge (ga), and 55-cm, 18-ga, needles (Fig. 2). A custom 103-cm long, 7-mm inner diameter, 9.5-mm outer diameter, stainless-steel needle was used for intracardiac injections in Cases 2 and 3 (Fig. 3). Custom, 100-cm long, 12-mm inner diameter, 21-mm outer diameter, and 167-cm long, 13-mm inner diameter, 20-mm outer diameter, stainless-steel needles were used for intracardiac injection in Case 5 (Fig. 4).

Figure 1. 

Locations of Mysticete strandings in North Carolina, USA, 2009–2013, detailed in this report. From south to north they were Case 1 Eubalaena glacialis CALO 0901, Case 4 Balaenoptera acutorostrata VGT 283, Case 3 Megaptera novaeangliae VGT 259, Case 2 M. novaeangliae MDB 090, and Case 5 M. novaeangliae CAHA 173.

Figure 1. 

Locations of Mysticete strandings in North Carolina, USA, 2009–2013, detailed in this report. From south to north they were Case 1 Eubalaena glacialis CALO 0901, Case 4 Balaenoptera acutorostrata VGT 283, Case 3 Megaptera novaeangliae VGT 259, Case 2 M. novaeangliae MDB 090, and Case 5 M. novaeangliae CAHA 173.

Figure 2. 

Custom-made, 31-cm, 16-gauge (ga), and 55-cm, 18-ga, needles used for intramuscular and retrobulbar injections for euthanasia of whales (Mysticeti) stranded in North Carolina, USA, 2009–2013, along with polyvinyl chloride (PVC) pipe carrying case. Ruler = 15 cm.

Figure 2. 

Custom-made, 31-cm, 16-gauge (ga), and 55-cm, 18-ga, needles used for intramuscular and retrobulbar injections for euthanasia of whales (Mysticeti) stranded in North Carolina, USA, 2009–2013, along with polyvinyl chloride (PVC) pipe carrying case. Ruler = 15 cm.

Figure 3. 

Euthanasia of a humpback whale (Megaptera novaeangliae) stranded in North Carolina, USA. Cardiac needle insertion following deep sedation and analgesia, low in the right axillary space, showing saturated KCl solution delivery system comprising a commercial garden sprayer, clear-plastic tubing, hose clamp, and custom-made needle (103 cm, 7-mm inner diameter, 9.5-cm outer diameter). Cables visible to the right of the picture connect portable electrocardiogram machine (out of view) to adhesive stick-on skin electrodes.

Figure 3. 

Euthanasia of a humpback whale (Megaptera novaeangliae) stranded in North Carolina, USA. Cardiac needle insertion following deep sedation and analgesia, low in the right axillary space, showing saturated KCl solution delivery system comprising a commercial garden sprayer, clear-plastic tubing, hose clamp, and custom-made needle (103 cm, 7-mm inner diameter, 9.5-cm outer diameter). Cables visible to the right of the picture connect portable electrocardiogram machine (out of view) to adhesive stick-on skin electrodes.

Figure 4. 

Newly developed, robust, customized needle and drug delivery system used in euthanasia of stranded whales (Mysticeti), North Carolina, USA, 2009–13. The needle is 1 m long, 21-mm outer diameter, 12-mm inner diameter, with a threaded point inserted at one end for ease of cleaning and safe transport and handling, six 3-mm side ports to avoid tissue coring, heavy gauge to reduce bending, a threaded plunger handle to facilitate insertion, and a quick disconnect coupling to allow for blood collection and drug delivery in the same insertion. The pressurized sprayer is commercially available and includes a control valve.

Figure 4. 

Newly developed, robust, customized needle and drug delivery system used in euthanasia of stranded whales (Mysticeti), North Carolina, USA, 2009–13. The needle is 1 m long, 21-mm outer diameter, 12-mm inner diameter, with a threaded point inserted at one end for ease of cleaning and safe transport and handling, six 3-mm side ports to avoid tissue coring, heavy gauge to reduce bending, a threaded plunger handle to facilitate insertion, and a quick disconnect coupling to allow for blood collection and drug delivery in the same insertion. The pressurized sprayer is commercially available and includes a control valve.

Case 1, field number CALO 0901

A 2-yr-old, male right whale calf (975 cm, estimated 10,000 kg; Moore et al. 2004) was reported stranded on 26 January 2009, but location and weather hampered access. At low tide, it was 95% emergent and, at high tide, 20% emergent. The first sustained access was on 29 January. It had caudal scoliosis, skin peeling, and scavenger damage by gulls. The following were administered retrobulbar trying to access vascular tissues: midazolam 90 mg (estimated 0.009 mg/kg, 18 mL of 5 mg/mL solution; Baxter Healthcare Corporation, Deerfield, Illinois, USA), diazepam 150 mg (0.015 mg/kg, 30 mL of 5 mg/mL solution; Baxter), acepromazine 450 mg (0.045 mg/kg, 45 mL of 10 mg/mL solution; Vedco Inc., St. Joseph, Missouri, USA), xylazine 13,000 mg (1.3 mg/kg, 130 mL of 100 mg/mL solution; Vedco), and medetomidine 22 mg (2.2 µg/kg, 22 mL of 1 mg/mL solution; Pfizer Animal Health, New York, New York, USA). That was followed by isoflurane (Piramal Healthcare Limited, Adhra Pradesh, India) by inhalation. Ten times in 9 min, approximately 20 mL of isoflurane (200 mL total) was delivered to a blowhole at peak inspiration, with apparent aerosolization. The palpebral reflex was diminished following isoflurane delivery. Considering that all available drugs had been administered, the whale would not reach a better state of analgesia that day, and it would otherwise suffer through another 24-hr period before additional drugs could be procured, the response team implemented an adjunct physical euthanasia technique of exsanguination. The caudal peduncle was severed 17 min after ceasing isoflurane. Arching occurred 46 min after cutting the caudal peduncle, coinciding with the whale's last breath. Time from first administration of sedative drugs until death was 2:03. The time from initiation of exsanguination until death was 64 min.

Gross necropsy, computed tomography, and histopathology confirmed the caudal scoliosis as a chronic, progressive process. An entanglement had been observed previously (2007), and scars were present around the flukes and peduncle. Entanglement was the probable cause of the scoliosis. Antemortem plasma and selected postmortem tissues were submitted to a commercial laboratory for drug residue analysis (NMS Labs, Willow Grove, Pennsylvania, USA). Methods of analysis, limits of detection, collection times postinjection, and plasma, serum, and tissue concentrations are listed in Table 1.

Table 1. 

Drug residues from three live-stranded, euthanized mysticete whales, North Carolina, USA, 2009–11. Case 1 is CALO 0901, a right whale (Eubalaena glacialis). Case 2 is MDB, a humpback whale (Megaptera novaeangliae). Case 3 is VGT 259, a humpback whale. Drug residues were not determined from Cases 4 and 5.a

Drug residues from three live-stranded, euthanized mysticete whales, North Carolina, USA, 2009–11. Case 1 is CALO 0901, a right whale (Eubalaena glacialis). Case 2 is MDB, a humpback whale (Megaptera novaeangliae). Case 3 is VGT 259, a humpback whale. Drug residues were not determined from Cases 4 and 5.a
Drug residues from three live-stranded, euthanized mysticete whales, North Carolina, USA, 2009–11. Case 1 is CALO 0901, a right whale (Eubalaena glacialis). Case 2 is MDB, a humpback whale (Megaptera novaeangliae). Case 3 is VGT 259, a humpback whale. Drug residues were not determined from Cases 4 and 5.a

The level of anesthesia, time to death, and aesthetics of Case 1 were unsatisfactory. The procedure was deemed acceptable only in the context of the alternative (i.e., continued suffering for several more days, humane killing versus euthanasia; AVMA 2013). This experience was strong incentive for the development of alternative strategies employed successfully in Cases 2–5.

Case 2, field number MDB 090

An 878-cm, estimated 9,500-kg (Lockyer 1976), juvenile, male humpback whale (Megaptera novaeangliae) was reported stranded on 15 May 2010, with responders reaching it the following day. At high tide, it was 20% emergent, and at low tide, it was nearly 100% emergent. It was heavily blistered and scavenged, with labored breathing. The peduncle had a deep encircling chronic wound from line entanglement.

Midazolam 400 mg IM (estimated dosage = 0.04 mg/kg, 80 mL, left epaxial muscles cranial to the scapula), acepromazine 1,950 mg intrathoracic (0.2 mg/kg, 195 mL caudal to the right pectoral fin), and xylazine 31,000 mg intravenously (IV) (3.4 mg/kg, 310 mL, right pectoral fin between radius and ulna), administered over 60 min rendered the whale minimally responsive (no palpebral or corneal reflexes). Intrathoracic acepromazine injections were delivered in an unsuccessful attempt to access great vessels near the heart, but at necropsy, it was evident that they entered consolidated lung tissue. Heart rate was 36 beats/min (electrocardiogram [ECG], Vet Biolog II, QRS Diagnostic, Plymouth, Minnesota, USA), and ECG signal appeared typical for smaller cetaceans (Hamlin et al. 1970). After 29 min from the last xylazine injection, saturated KCl solution (100 mg/kg or 1.3 mmol/kg; 3 L of approximately 300 mg/mL or 4 mmol/mL in tap water; K-Life water softener crystals, North American Salt Company, Overland Park, Kansas, USA) was administered within 3 min IC or IV near the heart from a 4-L commercial garden sprayer pressurized reservoir (Garden Plus Lawn & Garden Sprayer, Chapin International, Batavia, New York, USA; 2.5 atm = 1,875 mmHg maximum pressure) via a needle inserted through the right axillary space (Fig. 3). There was no response to needle insertion. Some fluke movements commenced shortly after starting KCl injection. The ECG signal transformed from normal sinus rhythm, to a sinusoidal wave, to ventricular fibrillation, to a flat line. Dorsal arching and gaping commenced 3 min after all KCl solution had been administered. The animal expired 7 min after the start, and 4 min after the completion, of KCl injection, and 1 hr 39 min from the first midazolam injection.

Antemortem and postmortem serum K+ concentrations were 3.5 and 11.4 mmol/L, respectively (North Carolina State University, College of Veterinary Medicine Diagnostic Laboratories, Raleigh, North Carolina, USA). Factors contributing to stranding included necrotic wounds at the base of the flukes, anemia, and pleuritis. Antemortem and postmortem plasma, liver, injection site lung, and noninjection site lung were submitted for drug residue analysis (NMS Labs; Table 1).

Case 3, field number VGT 259

An 830-cm, estimated 8,000-kg (Lockyer 1976), juvenile, male humpback whale was observed swimming in a sound on 7 March 2011 and was aground the following day. It was accessed the afternoon of 9 March 2011, 80% submerged in an area with minimal tides. Four fresh, deep, parallel, propeller gashes penetrated blubber into muscle cranial to the dorsal fin. Water depth created a personnel hazard, and along with limited remaining daylight, led to a decision to return the following morning and allow for the slight possibility that water depth would increase sufficiently for the whale to swim free. The next morning the animal was in the same location in deteriorating condition. Water depth was a hazard and complicated access to injection sites.

The following drugs were administered over 91 min, rendering the animal nonresponsive: midazolam 415 mg IM (estimated dosage 0.05 mg/kg, 83 mL), acepromazine 2,100 mg IM (0.25 mg/kg, 210 mL), and xylazine 30,000 mg (3.5 mg/kg, 300 mL) IM, retrobulbar, and IV. Saturated KCl (220 mg/kg or 3 mmol/kg) was delivered, as in Case 2, but from more difficult dorsal and lateral approaches because of the water depth, pericardially (about 80%) and IV, over the course of 22 min, followed by additional air to induce a possible embolism once all KCl solution had been delivered, and the animal expired 8 min later, preceded by 40 sec of terminal fluking. Time from first midazolam injection to death was 138 min, and from the first intrathoracic needle insertion for KCl delivery was 34 min.

Blood was collected twice antemortem and once postmortem. Antemortem and postmortem serum K+ concentrations were 4.0 and 4.6 mmol/L, respectively (Cornell University Animal Health Diagnostic Center, Ithaca, New York, USA). An in-water necropsy was performed immediately postmortem, subject to the limitations of the submerged conditions, and with safety spotters. Major findings included the deep lacerations, and muscle pallor consistent with blood loss. Plasma and serum, liver, and acepromazine muscle injection site were submitted for drug residue analysis (NMS Labs; Table 1).

Case 4, field number VGT 283

A 304-cm, 276-kg, male minke whale (Balaenoptera acutorostrata) calf stranded 25 January 2012. It was accessed later the same afternoon. The animal was completely emergent, and had been stranded for at least 7 hr. It had blistering over 35% of the dorsal body surface.

Total dosages of preeuthanasia drugs over 40 min were midazolam 0.14 mg/kg IM, acepromazine 1.6 mg/kg IM/IV, and xylazine 15.3 mg/kg IM/IV/IC, followed by saturated KCl approximately 168 mg/kg or 2.2 mmol/kg IC. An ECG showed normal sinus rhythm until KCl administration, then resolution into a flat line within 1 min. Time of death was 48 min after the initial dose of midazolam and 4 min after administration of KCl. Higher doses of acepromazine and xylazine were administered at shorter intervals than would otherwise have been employed to accelerate the process because of the short remaining daylight. Drug residues were not tested. Available boats permitted transport of the carcass off the barrier island. No major gross lesions were identified on necropsy, and milk was present in the stomach, leading to the presumptive diagnosis of maternal separation as a cause of stranding.

Case 5, field number CAHA 173

A 976-cm, estimated 13,000-kg (Lockyer 1976), juvenile, female humpback whale was reported stranded 10 June 2013 and was observed by volunteers until the response team reached it that afternoon. It was 95% emergent at low tide and had failed to float free during the high tide. Observers reported a marked decline in condition through the course of the day. The following drugs were administered over the course of 66 min, rendering the animal nonresponsive: midazolam 325 mg IM (estimated dosage 0.025 mg/kg, 65 mL), acepromazine 2,000 mg IM (0.15 mg/kg, 200 mL), and xylazine 33,500 mg IV (2.6 mg/kg, 300 mL in the right pectoral fin vessel, 50 mL in fluke vessel). Lidocaine (30 mL of 20 mg/mL solution; Sparhawk Laboratories, Inc., Lenexa, Kansas, USA) was infused into the blubber before insertion of a robust intracardiac needle (Fig. 4). Saturated KCl solution (150 mg/kg or 2 mmol/kg) was administered IC or IV near the heart, starting 18 min after the last xylazine injection and proceeding for 15 min. Vascular access was positional, requiring multiple adjustments. Minor fluke slapping occurred 4 min after completion of KCl injection, followed by cardiac arrest (as indicated by cessation of intracardiac needle movement) 5 min later. The animal expired 10 min after the completion of KCl injection and 1 hr 49 min from the first midazolam injection. At postmortem exam, the tip of the needle was found lodged in the aortic arch and carotid artery, where the KCl solution would have been carried away from the heart. Severe renal Crassicauda sp. infestation with fibrosis was the only major gross necropsy finding. Drug residues were not determined.

DISCUSSION

“Euthanasia is the act of inducing humane death in an animal,” and “should result in rapid loss of consciousness followed by cardiac or respiratory arrest and the ultimate loss of brain function” (AVMA 2013). Without the administration of preeuthanasia drugs, intracardiac insertion of the large bore needle and KCl administration would not meet the definition of euthanasia nor the criteria of acceptable euthanasia techniques (AVMA 2013), although field conditions involving free-ranging wildlife do not always permit true euthanasia, and humane killing may be necessary (AAZV 2006; AVMA 2013). In this case series, Case 1 was a humane killing that reduced pain and distress to the extent possible under the circumstances but demanded consideration of improved techniques, whereas Cases 2–5 met the definition of euthanasia.

Intravenous injection of a barbiturate, such as sodium pentobarbital, is the preferred method of euthanasia in most instances (AVMA 2013) but was not an option for these five cases because of relay toxicity concerns, given the difficulties of proper disposal for large carcasses in remote locations. Prolonged (36 hr) sedation occurred in a dog that consumed tissue possibly from a humpback whale euthanized with pentobarbital (and other drugs) 23 days previously in the same vicinity (Bischoff et al. 2011). Even when deep burial of euthanized animals is possible, detection of pentobarbital in surface waters and decades-long persistence in ground waters is a potential concern (Eckel et al. 1993; Peschka et al. 2006).

Exsanguination is an acceptable adjunct euthanasia method in otherwise unconscious animals but not as a sole method (AVMA 2013). Although, certainly, a low-residue technique, exsanguination is not rapid (approximately 1 hr in Case 1), can be visually distressing, and is potentially dangerous for personnel.

Determining an accurate weight estimate avoids excessive underdosing (prolonged animal suffering, possibility of an excitement phase affecting personnel safety) and overdosing (increased risk of relay toxicity and environmental contamination, tissue changes affecting pathologic interpretation, and cost; Barco et al. 2012). We used published species-specific length-weight formulas (Lockyer 1976; Moore et al. 2004). The animal's physiologic status must also be considered in determining suitable dosages. By using standard commercial drug concentrations for midazolam, acepromazine, and xylazine and by mixing water-softener–grade KCl, chemical expenses were modest. Drug costs for Cases 2 and 3 are compiled in Table 2.

Table 2. 

Drug costs (in US dollars) for euthanasia of the humpback whales MDB 090 and VGT 259, North Carolina, USA, 2010–11.

Drug costs (in US dollars) for euthanasia of the humpback whales MDB 090 and VGT 259, North Carolina, USA, 2010–11.
Drug costs (in US dollars) for euthanasia of the humpback whales MDB 090 and VGT 259, North Carolina, USA, 2010–11.

The small-gauge, long needles used for IM delivery of preeuthanasia drugs produced minimal response, allowing deep injections from a position of relative safety near the head. The sequence of drug delivery allowed the operator to advance to more-exposed positions as the whales became less responsive. Although the custom-made cardiac needle sufficed in Cases 2 and 3, tissue coring and needle bending were problems in both cases. To address those concerns, the authors designed and constructed more-robust needles to reduce bending, with a solid pointed tip and side ports to avoid tissue coring, and with a plunger handle to facilitate insertion through dense tissue (Fig. 4). These needles have been distributed strategically through the US Marine Mammal Health and Stranding Response Program, for use by trained personnel.

The drugs employed in these cases, although less of a concern for relay toxicity than pentobarbital, may carry some indeterminate risk to scavengers (AVMA 2013). We determined the drug residues in selected tissues of Cases 1–3 to assess risks to scavengers. We also determined plasma or serum drug concentrations to reinforce clinical assessments of efficacy. Circulating and tissue drug concentrations are presented in Table 1 and are detailed below.

Midazolam is a benzodiazepine anxiolytic dosed at 0.2–0.4 mg/kg IV or IM as a preanesthetic in dogs and cats and at 0.01–0.04 mg/kg IV as a preoperative agent in horses (Plumb 2011). An entangled right whale has been dosed with concentrated midazolam (compounded at 50–90 mg/mL), estimated at 0.03–0.1 mg/kg, along with butorphanol to facilitate disentanglement (Moore et al. 2010). Three gray whales (Eschrichtius robustus) were administered midazolam, estimated at 0.02–0.03 mg/kg IM, and were adequately sedated for IV euthanasia (Greer et al. 2001). Minimum effective plasma concentration in humans is 30–100 ng/mL (Crevoisier 1983). Plasma concentrations in that range were found in Cases 2 and 3, but not in Case 1. Injection site concentration in Case 1 was below the assay limit of detection (20 ng/g). Midazolam is well absorbed orally but poorly bioavailable because of first-pass effect (31–72%; Plumb 2011). No measured midazolam concentrations were sufficient to raise a concern of relay toxicity.

Acepromazine is a phenothiazine neuroleptic sedative with negligible analgesic effects, but it can potentiate analgesic effects of other drugs (Plumb 2011). It is dosed at 0.02–0.05 IM as a preanesthetic in horses and at 0.1–0.2 mg/kg IV or IM or 1–3 mg/kg orally as a preanesthetic in dogs (Plumb 2011). Oral bioavailability in dogs is 20% (Hashem et al. 1992). At clinically effective IM and IV dosages in large, domestic animals, plasma concentrations of acepromazine are low and difficult to detect (Ballard et al. 1982). Plasma concentrations in Cases 2 and 3 were comparable to those achieved in horses dosed higher at 0.3 mg/kg IV (Ballard et al. 1982). No measured acepromazine concentrations were sufficient to raise a concern of relay toxicity.

Xylazine is a sedative analgesic α2-adrenergic agonist (Plumb 2011). Xylazine is the key pain-relieving drug administered before cardiac puncture for KCl delivery in this protocol. Xylazine has been associated with excitement in a gray whale (Greer et al. 2001) and Risso's dolphins (Grampus griseus; Barco et al. 2012). When preceded by midazolam or acepromazine, no such adverse reaction has been observed in Risso's dolphins (C.A.H. pers. obs.), or in the cases in this current report. Xylazine is dosed at 0.2–1 mg/kg IM as a preanesthetic in dogs, at 0.1–0.3 mg/kg IM in cattle, and at 1–10 mg/kg IM in birds (Plumb 2011). Bioavailability following IM injection is variable: 52–90% in dogs and 40–48% in horses (Garcia-Villar et al. 1981). Plasma concentrations in Cases 2 (estimated dosage 3.4 mg/kg IV, 0.99 µg/mL in plasma) and 3 (estimated dosage 3.5 mg/kg IM; 0.24 µg/mL in plasma), both collected 49 min postadministration, indicate an adequate but relatively low IM bioavailability in cetaceans. Plasma concentrations corresponding to sedation and analgesia in other animals (Garcia-Villar et al. 1981; Rector et al. 1996; Lizarraga and Beths 2012) were achieved or exceeded in Cases 2 and 3, but not in Case 1. Oral bioavailability of xylazine is poor because of first pass metabolism, however, it may be directly absorbed from the oral and pharyngeal mucosa (Pawson 2008), making assessment of relay toxicity risk difficult. Acute oral toxicity of xylazine in rats (Rattus sp.) was considered moderate, with a 50% lethal dose (LD50) of 120–240 mg/kg (INCHEM 2013). Injection site concentration of xylazine in Case 1 was 630 µg/g (Table 1), which is sufficiently high to cause concern for relay toxicity. A 1-kg scavenger would have to consume 190 g, or 19% of body weight, to reach the rat LD50, but lethal effects in a smaller proportion could be reached with a normal meal size. It would, therefore, be prudent to trim xylazine IM injection sites for disposal. The highest noninjection site tissue concentration detected in these cases was 12 µg/g in the liver of Case 2. Xylazine tissue residues at noninjection sites are, therefore, a low risk for relay toxicity to scavengers at the dosages employed in Cases 1–3 (1.3–3.5 mg/kg) but might have been a concern in Case 4 if it had not been removed from the beach (total xylazine dosage 15.3 mg/kg).

Saturated KCl solution is acceptable in a two-step euthanasia when preceded by general anesthesia (AVMA 2013). It is not a controlled substance; it is inexpensive, does not induce histologic artifacts, and is a preferred technique to reduce risk of relay toxicity (AVMA 2013). Rapid IV or IC injection at 1–2 mmol/kg (75–150 mg/kg) causes prompt cardiac arrest (AVMA 2013). Commercial products are supplied at a 2 mmol/mL (150 mg/mL) concentration (Plumb 2011). Higher concentrations can be mixed, with temperature-dependent solubility: 281 mg/mL at 0 C, 360 mg/mL at 25 C (Lide 2004). Potassium chloride was dissolved to saturation at room temperature, but approximately 300 mg/mL (4 mmol/mL) was used for dosage calculations. In Case 2, the sharp rise in serum potassium concentration from 3.5 mmol/L antemortem to 11.4 mmol/L immediately postmortem, associated with ECG changes, provided evidence of successful intravascular delivery of a lethal dose of KCl. In Case 3, immediate postmortem serum potassium concentration increased to only 4.6 mmol/mL, indicating three possibilities: 1) the portion of the KCl deposited pericardially was ineffectual or less effective, 2) the portion of the KCl delivered IV had not completed a full circuit to the point of collection, or 3) the air delivery that followed KCl caused a fatal embolism equally or more responsible for death than the KCl in this case, with a similar lack of tissue residue concerns. In both cases, postmortem blood was collected at sites other than KCl injection, and hemolysis was undetectable (Case 3) or mild (Case 4), so neither a residual injection site KCl pool nor hemolysis were responsible for the high postmortem concentration in Case 2. We opted for the IC rather than IV route because it is more immediate, avoids the dilution that occurs with peripheral delivery (AVMA 2013), accommodates large volumes more rapidly, and can be administered from a position of relatively greater safety than from near the flukes.

Potassium chloride solution following premedication has been reported previously in mysticetes (Daoust and Ortenburger 2001; Kolesnikovas et al. 2012). A 10.5-m, estimated 10,000-kg, juvenile fin whale (Daoust and Ortenburger 2001) was treated with IV injection of xylazine (estimated 0.5 mg/kg), T-61 (euthanasia solution comprising embutramide 200 mg/mL, mebezonium iodide 50 mg/mL, and tetracaine hydrochloride 5 mg/mL; 0.01 mL/kg), and KCl solution (0.12 mmol/kg, or 9 mg/kg), and the animal expired approximately 1 hr later. A 13.5-m, estimated 40,000-kg, southern right whale (Kolesnikovas et al. 2012) was euthanized on day 7 of stranding using xylazine (estimated 0.5 mg/kg IM), ketamine (2.47 mg/kg IM), T-61 (0.018 mL/kg IC), and KCl solution (0.25 mmol/kg, or 19 mg/kg IC). Both cases employed T-61, which is not routinely available in the US, although it has been used successfully in a juvenile fin whale in Rhode Island, US (Dunn 2006). Both of those cases employed lower dosages of xylazine and KCl than that used in our cases. That they were both successful may be a function of the greater debilitation of those whales or the effects of T-61 or both. Likewise, dosages we report may be excessive for a moribund animal or insufficient for a strong freshly stranded animal.

The midazolam, acepromazine, xylazine, saturated KCl technique resulted in acceptable euthanasia of mysticetes, with relatively low cost and minimal risk of relay toxicity, although safe disposal of xylazine IM injection sites would be prudent. Drug delivery well away from the flukes resulted in reduced risk to personnel. Stepwise administration of anxiolytic, sedative, analgesic, and anesthetic drugs, by decreasing responsiveness, further reduced personnel risk leading up to intracardiac needle insertion. Midazolam could be omitted if controlled drugs are unavailable. Appropriately sized needles are required for intracardiac injection. Every large whale stranding event poses unique challenges. Depending on many variables, this protocol may be appropriate and helpful in some circumstances.

ACKNOWLEDGMENTS

Eric Anderson, Michele Bogardus, Heather Broadhurst, Karen Clark, Paul Doshkov, Kim Durham, Ari Friedlander, Robert George, Tripp Kolkmeyer, Gretchen Lovewell, Ray Mroch, Ann Pabst, Keith Rittmaster, Betsy Stringer, Jill Sullivan, Joshua Summers, Jennifer Hurley-Sanders, Dave Rotstein, Gwen Lockhart, Shannon Davis, Sarah Mallette, and additional personnel from Cape Lookout and Cape Hatteras National Seashores; the US Coast Guard; and the North Carolina Marine Patrol all provided invaluable assistance on one or more cases. We thank Robert Maclean in particular for providing the custom-made, small-gauge, long needles. Ryan McAlarney constructed the map in Figure 1. Funding for stranding responses and drug residue analyses came from Prescott Grants (NA04NMF4390040, NA08NMF4390590, NA09NMF4390226, NA09NMF4390215, NA10NMF4390238, NA11NMF4390065, NA12NMF4390165), and Prescott Emergency Grants (2005-0162-008 and 2005-0162-014). Erin Fougeres, NMFS Southeast Region, provided funding for the improved intracardiac delivery system.

LITERATURE CITED

American Association of Zoo Veterinarians
.
2006
.
Guidelines for euthanasia of nondomestic animals
.
AAZV
,
Yulee, Florida
,
111
pp.
American Veterinary Medical Association
.
2013
.
AVMA guidelines for the euthanasia of animals
.
AVMA
,
Schaumburg, Illinois
, .
Ballard
S
,
Shults
T
,
Kownacki
AA
,
Blake
JW
,
Tobin
T
.
1982
.
The pharmacokinetics, pharmacological responses and behavioral effects of acepromazine in the horse
.
J Vet Pharm Ther
5
:
21
31
.
Barco
SG
,
Walton
WJ
,
Harms
CA
,
George
RH
,
D'Eri
LR
,
Swingle
WM
.
2012
.
Collaborative development of recommendations for euthanasia of stranded cetaceans
.
Final report to NOAA/NMFS for John H. Prescott Award NA09NMF4390212. VAQF Scientific Report 2012-06
,
Virginia Beach, Virginia
,
183
pp.
Barnett
JE
,
Jepson
PD
,
Patterson
IA
.
1999
.
Drug induced euthanasia of stranded cetaceans [letter]
.
Vet Rec
145
:
292
.
Bischoff
K
,
Jaeger
R
,
Ebel
JG
.
2011
.
An unusual case of relay pentobarbital toxicosis in a dog
.
J Med Toxicol
7
:
236
239
.
Coughran
DK
,
Stiles
I
,
Mawson
PR
.
2012
.
Euthanasia of beached humpback whales using explosives
.
J Cetacean Res Manag
12
:
137
144
.
Crevoisier
Ch
,
Ziegler
WH
,
Eckert
M
,
Heizmann
P
.
1983
.
Relationship between plasma concentration and effect of midazolam after oral and intravenous administration
.
Br J Clin Pharmacol
16
:
15S
61S
.
Daoust
P-Y
,
Ortenburger
AI
.
2001
.
Successful euthanasia of a juvenile fin whale
.
Can Vet J
42
:
127
129
.
Dunn
JL
.
2006
.
Multiple-agent euthanasia of a juvenile fin whale, Balaenoptera physalus
.
Mar Mamm Sci
22
:
1004
1007
.
Eckel
WP
,
Ross
B
,
Isensee
RK
.
1993
.
Pentobarbital found in ground water
.
Ground Water
31
:
801
804
.
Garcia-Villar
R
,
Toutain
PL
,
Alvinerie
M
,
Ruckebusch
Y
.
1981
.
The pharmacokinetics of xylazine hydrochloride: An interspecific study
.
J Vet Pharmacol Ther
4
:
87
92
.
Geraci
JR
,
Lounsbury
VJ
.
2005
.
Marine mammals ashore: A field guide for strandings, 2nd Ed
.
National Aquarium in Baltimore
,
Baltimore, Maryland
,
371
pp.
Greer
LL
,
Whaley
J
,
Rowles
TK
.
2001
.
Euthanasia
.
In:
Marine mammal medicine, 2nd Ed
,
Dierauf
LA
,
Gulland
FMD
,
editors
.
CRC Press
,
Boca Raton, Florida
, pp.
729
238
.
Hamlin
RL
,
Jackson
RF
,
Himes
JA
,
Pipers
FS
,
Townsend
AC
.
1970
.
Electrocardiogram of bottle-nosed dolphin (Tursiops truncatus)
.
Am J Vet Res
31
:
501
505
.
Hashem
A
,
Kietzmann
M
,
Scherkl
R
.
1992
.
The pharmacokinetics and bioavailability of acepromazine in the plasma of dogs
.
Dtsch Tierarztl Wochenschr
99
:
396
398
.
International Programme on Chemical Safety
.
2013
.
Xylazine
, .
Kolesnikovas
CKM
,
Groch
KR
,
Groch
KR
,
de Moraes
AN
,
Flores
PAC
,
Pretto
DJ
,
Freitas
RR
,
Gaidzinski
MC
,
de P. Mreira
LM
,
da Rocha
MEC
.
2012
.
Euthanasia of an adult southern right whale (Eubalaena australis) in Brazil
.
Aquat Mamm
38
:
317
321
.
Lide
DR
.
2004
.
CRC handbook of chemistry and physics, 85th Ed
.
CRC Press
,
Boca Raton, Florida
, pp.
4
76, 8–125
.
Lizarraga
I
,
Beths
T
.
2012
.
A comparative study of xylazine-induced mechanical hypoalgesia in donkeys and horses
.
Vet Anaesth Analg
39
:
533
538
.
Lockyer
C
.
1976
.
Body weights of some species of large whales
.
ICES J Mar Sci
36
:
249
273
.
Moore
MJ
.
2010
.
Overview of euthanasia of large whales
.
International Whaling Commission, IWC/A10/E1, iwcoffice.org/_documents/sci_com/SC62docs/IWC-A10-E1Rev.pdf. Accessed March 2013
.
Moore
MJ
,
Knowlton
AR
,
Kraus
SD
,
McLellan
WA
,
Bonde
RK
.
2004
.
Morphometry, gross morphology and available histopathology in North Atlantic right whale (Eubalaena glacialis) mortalities (1970–2002)
.
J Cetacean Res Manag
6
:
199
214
.
Moore
M
,
Walsh
M
,
Bailey
J
,
Brunson
D
,
Gulland
F
,
Landry
S
,
Mattila
D
,
Mayo
C
,
Slay
C
,
Smith
J
,
Rowles
T
.
2010
.
Sedation at sea of entangled North Atlantic right whales (Eubalaena glacialis) to enhance disentanglement
.
PloS One
5
(
3
):
e9597
.
doi:10.1371/journal.pone.0009597
.
Pawson
P
.
2008
.
Sedatives
.
In:
Small animal clinical pharmacology, 2nd Ed.
,
Maddison
JE
,
Page
SW
,
Church
DB
,
editors
.
Saunders Elsevier
,
Philadelphia, Pennsylvania
, pp.
113
126
.
Peschka
M
,
Eubeler
JP
,
Knepper
TP
.
2006
.
Occurrence and fate of barbiturates in the aquatic environment
.
Environ Sci Technol
40
:
7200
7206
.
Plumb
DC
.
2011
.
Plumb's veterinary drug handbook, 7th Ed
.
Wiley-Blackwell
,
Ames, Iowa
,
1185
pp.
Rector
E
,
Otto
K
,
Kietzmann
M
,
Nolte
I
,
Lehmacher
W
.
1996
.
[Pharmacokinetics and effects of xylazine (Rompun) in dogs]
.
Berl Munch Tierarztl Wochenschr
109
:
18
22
.