The Use of Midazolam, Isoflurane, and Nitrous Oxide for Sedation and Anesthesia of Ball Pythons (Python regius) by Cédric B. Larouche A Thesis presented to The University of Guelph In partial fulfilment of requirements for the degree of Doctor of Veterinary Science in Pathobiology Guelph, Ontario, Canada © Cédric B. Larouche, August, 2019 ABSTRACT THE USE OF MIDAZOLAM, ISOFLURANE, AND NITROUS OXIDE FOR SEDATION AND ANESTHESIA OF BALL PYTHONS (PYTHON REGIUS) Cédric B. Larouche Co-advisors: University of Guelph, 2019 Nicole Nemeth Dorothee Bienzle The objectives of this project were to characterize the pharmacodynamics and pharmacokinetics of midazolam in the ball python (Python regius), and to evaluate the effects of midazolam and nitrous oxide (N2O) on the minimum anesthetic concentration of isoflurane (MACIso) in this species. The pharmacodynamics of midazolam were evaluated in a blinded, randomized, crossover study comparing two dosages (1 and 2 mg/kg intramuscular [IM]) in ten ball pythons. There were no significant differences between the two dosages for any parameter evaluated. Midazolam provided moderate sedation and muscle relaxation in all snakes starting 10-15 min post-injection and lasting up to 3-5 days, with a peak effect 60 min post-injection. Heart rates were significantly lower than baseline from 30 min to 5.3 days post-injection with both dosages. In an open trial using 9 ball pythons, the reversal effect of flumazenil was evaluated by administering 0.08 mg/kg IM 60 min after the administration of 1 mg/kg IM of midazolam. Sedation and muscle relaxation were fully reversed within 10 min of administration, but all snakes fully resedated within 3 h. In a semi-blinded, randomized, crossover trial, nine ball pythons were used to evaluate the effects of 1 mg/kg IM midazolam and N2O mixed 50:50 with oxygen on the MACIso. Midazolam significantly decreased the MACIso from 1.11% (95% confidence interval [CI], 0.94-1.28%) to 0.48% (95% CI, 0.29-0.67%), and N2O decreased the MACIso to 0.92% (95% CI, 0.74-1.09%). No clinically relevant differences between treatments were noted regarding blood gases but isoflurane induction with face mask caused marked acidemia that resolved with mechanical ventilation. Central venous catheters were surgically placed in twelve ball pythons to evaluate the pharmacokinetics of midazolam. Snakes were randomly and equally divided into two groups receiving 1 mg/kg of midazolam either intracardiac (IC; group 1) or IM (group 2). Plasma concentrations of midazolam and its major metabolite 1- hydroxymidazolam were determined using high-performance liquid chromatography tandem-mass spectrometry. Mean bioavailability following IM administration was 89%. Mean ± SD clearance of midazolam was 0.053 ± 0.008 L/h/kg, leading to slow elimination half-lives (12.04 ± 3.25 h [IC] and 16.54 ± 7.10 h [IM]). iv ACKNOWLEDGEMENTS This thesis has been a series of mostly self-imposed, tight deadlines. I would therefore like to thank all the members of my advisory committee for dealing so brilliantly with all my last-minute questions and revision requests: Chris Dutton, Dorothee Bienzle, Nicole Nemeth, Hugues Beaufrère, Craig Mosley, and Ron Johnson. There are so many people I wish to thank for their contribution and support. If I have forgotten to mention you, please feel free to request a beer any time. I would like to thank the Toronto Zoo, OVC Pet Trust, and the Andrea Leger Dunbar Summer Research Studentship for providing funding for this DVSc. This project would have never been possible without their financial support. I would like to thank Chris Dutton and Pauline Delnatte for being my anchor from day 1 until the very end of my residency. With so many people coming and going, you two have been a constant I could always rely on throughout this project and residency. Chris, your enthusiasm is contagious and working with you is such a delight. You are a brilliant veterinarian and leader, and I consider myself extremely lucky to have been your resident for 3 years. Pauline, you are one of the most dedicated and talented veterinarians I know. Your trust in my skills and your desire to do what’s best for every single animal made every second spent with you a learning opportunity. I am very grateful to Dorothee Bienzle for her constant support. This project would not have been completed as smoothly without your advice and attention to my timeline. I would also like to thank Hugues Beaufrère for his major help in every step of the project, from providing the original idea to the statistical analyses, and the ACZM preparation classes. This project would have never been successful without the amazing work of the Toronto Zoo’s Wildlife Health Center staff. All of you either took care of my massive ball pythons, helped me in some way with the experimentation, and/or made my whole residency such a delight. Thank you Tasha Long, Rick Vos, Mark Bongelli, Andrea Dada, Dianne Morrison, Nigel Parr, Lydia Attard, Gerri Mintha, Margaret Kolakowski, Brian Telford, Charles Guthrie, Jason Dawes, Kerri Chase, and Julie Digiandomenico. I especially want to mention the invaluable help from the most amazing veterinary technicians I could have hoped for: Michelle Lovering, Dawn Mihailovic, Cassia Devison, and Stephanie Fleming. I would also like to thank Simon Hollamby and David McLelland for all the teaching opportunities. I would like to thank Kristopher Afshaun Zaman for his huge help and dedication to the project. You made my life so much easier with your exceptional technical and mental support during the summer 2018. These ball pythons are extremely grateful for the amazing care you provided. I am grateful for all the students who provided technical v support for the experimentation or care of these snakes, especially Hannah Bagnall and Sydney Swartz for their help with the pharmacokinetic project, and Malika Ladak for her help with my first side project on tarantulas. The last chapter of this thesis on the pharmacokinetics of midazolam would have never been possible without the dedication of Yu Gu. I would like to thank her, Ron Johnson, and everyone who helped with this assay. I am grateful to Francis Beaudry for his help with the pharmacokinetic analysis. I contacted you out of nowhere and you immediately helped. I would like to acknowledge again the support of my whole advisory committee. Craig, you offered me invaluable advices on the planning, execution, and analysis of this project. Nicole, your support during the preparation phase was highly appreciated. Your talent in writing and revising scientific manuscripts significantly improved the quality of this thesis. I am very grateful to Leonardo Susta for his incredible dedication to the zoo pathology program. With all the major changes that happened to the program during my residency, you took it upon yourself to make sure the quality of the teaching would be maintained, and I cannot express how much I learned screening and discussing with you. I would also like to thank all the other pathologists who taught me everything I know about pathology, especially Emily Brouwer, Nicole Nemeth, Dale Smith, and Rob Foster. My weekly trips to Guelph would have been much harder without the great comradery of the anatomical and clinical pathology residents in the microscope room. Thank you for being such an awesome team! I cannot mention all these people without naming my co-residents, who made this whole residency such a delight. Ellie Milnes, you are such a strong, confident, and talented person; nothing can stop you from accomplishing your dreams. Your informal help with every step of this project and my residency probably had the biggest influence on my success. Thank you so much for being that amazing! Jessica Aymen, we didn’t get to work very long together as co-residents, but I wanted to thank you as well for being such an amazing person. The young veterinary student I knew back in Saint- Hyacinthe has become a confident and very talented veterinarian in such a small period of time. This whole residency craziness started with my first partner in crime, Émilie L. Couture. You introduced me to the zoological medicine department and always pushed me to reach further. The whole team in Saint-Hyacinthe made the step into the residency so much smoother. I would like to thank especially Graham Zoller, Guy Fitzgerald, Isabelle Langlois, Stéphane Lair, Édouard Maccolini, Julie Hébert, Marion Desmarchelier, Marie-Josée Limoges, Shannon Ferrell, Valérie Lacasse, and Léa Ahmed. vi I am infinitely grateful to Adam McCall for his immense support throughout this residency. I have no idea how I could have gone through all of this without your help. Finally, I would like to thank my family that has always been there for me, supporting every choice and steps that I made. Without all the opportunities you have given me, all the lessons you’ve taught me, and all the love you’ve provided, none of this would have ever been possible. Cédric B. Larouche Scarborough, August 2019 vii TABLE OF CONTENTS Abstract ...........................................................................................................................ii Acknowledgements .......................................................................................................iv Table of Contents ......................................................................................................... vii List of Tables .................................................................................................................xi