Physiologic Evaluation of Medetomidine-Ketamine Anesthesia in Free-ranging Svalbard (Rangifer tarandus platyrhynchus) and Wild Norwegian Reindeer (Rangifer tarandus tarandus)

During the past 20 yr, a large number of free-ranging, wild Norwegian reindeer (WR, Rangifer tarandus tarandus) have been captured by aerial darting. Although early captures were done with etorphine, a better quality of anesthesia was found with medetomidine-ketamine (Arnemo et al., 2011). Arnemo and Aanes (2009) did a similar study on medetomidine-ketamine anesthesia in Svalbard reindeer (SR, Rangifer tarandus platyrhynchus). Hypoxemia (as indicated by pulse oximetry) following medetomidine-ketamine administration has also been reported for captive, semidomestic Norwegian reindeer, R. t. tarandus (Ryeng et al., 2001), WR (Arnemo et al., 2011), and SR (Arnemo and Aanes, 2009).

Inadequate arterial oxygenation results in tissue hypoxia, which can cause cell damage to vital organs, including the brain, heart, kidneys, and liver (Caulkett et al., 1994; McDonell and Kerr, 2007). Hypoxemia, often defined as an hemoglobin oxygen saturation <85%, is common during chemical capture of wildlife (Caulkett and Arnemo, 2007). Here, we follow up previous work (Arnemo and Aanes, 2009; Arnemo et al., 2011) by presenting more detailed clinical and physiologic effects of medetomidine-ketamine administered to free-ranging, wild Norwegian reindeer by dart syringe from a helicopter and Svalbard reindeer darted from the ground. We also evaluated intranasal insufflation of low-flow rates of oxygen for correction of arterial hypoxemia.

The study was conducted during October 2010 in Adventdalen, Svalbard, Norway (78°18′N, 16°33′E) and during March 2012 in Hardangervidda, Telemark, Norway (59°59′N, 7°44′E) and Setesdal (59°24′N, 7°30′E). Sixteen adult SR (four male, eight female) and 10 adult female WR were captured. Capture of WR was approved by the Norwegian Animal Research Authority and the Norwegian Directorate for Nature Management, whereas capture of SR was approved by The Norwegian Animal Research Authority and The Governor of Svalbard.

Capture of WR was done as described by Arnemo et al. (2011). They were immobilized with a combination of medetomidine (Zalopine® 10 mg/mL, Orion Corporation Animal Health, Espoo, Finland) and ketamine (Ketavet® 100 mg/mL, Parke-Davis GmbH, Berlin, Germany). An initial dose of 10 mg medetomidine and 200 mg ketamine per animal was used. Animals that were not recumbent within 20 min of drug administration were redarted with an additional full dose. Once reindeer were recumbent, the helicopter landed, and the capture team waited at least 5 min before approaching.

On Svalbard, reindeer were located using binoculars and approached on foot as described by Arnemo and Aanes (2009). An initial dose of 10 mg medetomidine and 200 mg ketamine per animal was used. Physiologic evaluation for both WR and SR was done as previously reported for moose (Evans et al., 2012). Recorded variables included time from sighting animal to successful darting (darting time) and time from darting to recumbency (induction time). All reindeer were maintained in sternal recumbency during immobilization. Heart rate (by auscultation of the heart), respiratory rate (counting breaths), and rectal temperature (digital thermometer) were measured immediately after capture. Animals were weighed with a portable scale. Immediately after capture and after 15 min of nasal oxygen insufflation, arterial blood samples were collected anaerobically from the auricular artery using self-filling arterial syringes with heparin (PICO™ 70, Radiometer Copenhagen, Brønshøj, Denmark) and analyzed immediately with an i-STAT® 1 Portable Clinical Analyzer and i-STAT CG4+, 6+, and EC8+ cartridges (Abbott Laboratories, Abbott Park, Illinois, USA). As previously reported (Evans et al., 2012), the i-STAT 1 analyzer was kept in an insulated box to keep it at optimum temperature (16–30 C), with warm water bottles used as needed. Wild reindeer were given 2 L/min of oxygen, except for one animal which received 1 L/min, and SR received 1 L/min. Measured variables included pH, hematocrit, partial pressure of arterial oxygen (PaO₂) and carbon dioxide (PaCO₂), and whole-blood concentrations of lactate, sodium (Na), potassium (K), chloride (Cl), urea, and glucose. In SR, lactate concentrations were measured with the Lactate Pro/LT-1710 (Arkray Factory Inc, KDK Corp., Japan). PaO₂, PaCO₂, and pH were corrected on the basis of rectal temperature. Calculated values included concentration of bicarbonate (HCO₃), hemoglobin, oxygen hemoglobin saturation (SaO₂%), and base excess (BE). Atipamezole (Antisedan® 5 mg/ml Orion Pharma Animal Health, Espoo, Finland) at 5 mg/1 mg medetomidine was used for reversal. Time from darting until time of administration of reversal drugs and time from reversal until standing were recorded. Hypoxemia was defined as mild (PaO₂ = 8.0–10.0 kPa), marked (PaO₂ = 5.5–8.0 kPa), or severe (PaO₂<5.5 kPa). Acidemia was defined as pH<7.35, and acidemia was considered marked if pH<7.20. Hypocapnia was defined as a PaCO₂<4.5 kPa, and hypercapnia was defined as mild (PaCO₂ = 6–8 kPa) or marked (PaCO₂>8 kPa). The target PaO₂ after oxygen supplementation was defined as 11–16 kPa.

Variables were first tested for normality using Shapiro-Wilk test (P<0.05). Results for the first and second sample (both measured and calculated values) were compared using a paired t-test for normally distributed variables and the Wilcoxon signed-rank test for variables not distributed normally. Statistics were carried out using JMP® 9.0.2 (SAS Institute, Cary, North Carolina, USA).

The ambient temperature ranged from 8±2 C (4–9 C) during WR captures, and −3±4 C (−9 C to +4 C) for SR captures. One WR and one SR required a second dart, and these animals were excluded from analysis. Two SR required extra drugs, and these were given 100 and 250 mg ketamine intramuscularly. In a previous study (Arnemo and Aanes, 2009), no significant differences between males and females were found, so data were pooled for SR. All animals were completely immobilized with good muscle relaxation. Recoveries were calm, and animals stood up and walked away in a coordinated manner. After 6 mo, all WR were alive with functioning GPS collars, except for one collar that stopped working after 3 mo. SR were in an area frequented by hikers and tourists, and no reports of dead reindeer were received.

Physiologic variables and arterial blood gas results are summarized in Tables 1 (WR) and 2 (SR). For WR, arterial samples were collected from seven animals immediately at capture and repeated after 15±4 (10–23) min with intranasal oxygen insufflation. Six SR were sampled initially and again after 21±8 (15–31) min with intranasal oxygen insufflation. In two SR, errors were received on the oxygen variables (PaO₂ and SaO₂): one on the presample and one on the postsample. These two animals were included in all analyses not involving PaO₂ and SaO₂. Wild reindeer had significantly higher body temperature than SR both before (P<0.0001) and after (P<0.0001) oxygen supplementation, although neither had a significant difference between the before and after sampling (Tables 1, 2).

On initial sampling, all seven WR were hypoxemic, with three classified as mild and four as marked. Four were acidemic. One of seven reindeer was mildly hypercapnic. After oxygen treatment in five animals (four receiving 2L/min and one receiving 1L/min), no animals were hypoxemic, three were mildly acidemic, and four were mildly hypercapnic. Only two were within the target range for PaO₂ (11.9 kPa for the one receiving 1 L/min and 14.9 kPa for one receiving 2 L/min). The other three were above the target (16.4, 17.7, and 19.6 kPa). In SR, on initial sampling, one animal had an erroneous PO₂ reading (air bubble in sample), and four of the six remaining were hypoxemic, with two animals exhibiting marked hypoxemia. Only one animal was mildly acidemic (pH 7.34). Five of seven were hypercapnic, with marked hypercapnia in one animal. Six of the seven were sampled after oxygen supplementation, with one sample giving an erroneous PaO₂ and SaO₂ reading. None of the remaining five were hypoxemic, with two being in the target range (12.9 and 13.9 kPa) and three being well above (16.3, 18.9, and 39.3 kPa). Four of six were hypercapnic, with marked hypercapnia in one animal (a different individual than before treatment). No animals were acidemic after treatment. The WR were visibly excited and stressed from helicopter darting, whereas the SR remained calm, and other members of the herd calmly walked away from the immobilized animal.

All reindeer in our study were hypoxemic upon capture, and all that received supplemental oxygen had normal to high oxygen levels afterward. With an oxygen flow rate of 1 L/min in SR (n = 5) and 2 L/min in WR (n = 4), animals were well within or above the target range, so it is likely that 0.5 L in SR and 1 L in WR would be sufficient; however, further studies are needed to confirm this.

The significantly higher body temperature in the WR can be attributed to stress associated with helicopter chasing and running. The Svalbard reindeer were calm and not concerned by the darter's presence and often walked only 10–20 m away when they noticed the presence of the researchers. The SR exhibited lower and the WR higher temperatures than found in captive semidomestic reindeer (mean 39.1 C, 95% CI, 38.9–39.3 C; Ryeng et al., 2001), likely indicating relative stress levels for captures in these three types of reindeer.

Medetomidine-ketamine is an effective drug combination for immobilization of free-ranging adult wild Norwegian reindeer and Svalbard reindeer (Arnemo and Aanes, 2009; Arnemo et al., 2011). However, all animals exhibited mild to marked hypoxemia, likely caused by the relatively high doses of medetomidine presented here, readily corrected with intranasal oxygen supplementation. Therefore, oxygen supplementation is recommended for these subspecies when anesthetized with medetomidine-ketamine.

We thank Marit Madderrom and Brage B. Hansen for contributing to the captures of Svalbard reindeer. This study was funded by the Norwegian Directorate for Nature Management, the Norwegian School of Veterinary Science, Hedmark University College Morris Animal Foundation, the Norwegian Polar Institute, and the Svalbard Science Forum (Arctic Field grant RIS 3753).