Propofol-medetomidine-ketamine total intravenous anaesthesia in thiafentanil

59 Pages·2016·1.99 MB·English

Propofol-medetomidine-ketamine total
intravenous anaesthesia in thiafentanil-
medetomidine immobilised impala (Aepyceros
melampus) of 120 minute duration

By

ROXANNE KATE BUCK

Submitted in partial fulfilment of the requirements for the degree of Masters of Science (Veterinary
Science) in the Department of Companion Animal Clinical Studies in the Faculty of Veterinary
Science, University of Pretoria

Date Submitted: June 2015

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Acknowledgements
I would like to express my gratitude and appreciation to the following groups of people, without
whose help, this project would not have been a success:
The staff and students from the Onderstepoort Veterinary Academic Hospital and Faculty of
Veterinary Science, specifically from the Department of Paraclinical Science, who assisted with the
care of the impala as well as data collection.
Johan Steyl, Jacques O’Dell and the team of staff and students who assisted with the impala capture
and translocation before and after the trial.
Carien Muller and her team at the clinical pathology laboratory in the OVAH for their assistance with
running and storing blood samples for us.
The Department of Companion Animal Clinical Studies in the Faculty of Veterinary Science, University
of Pretoria, the University of Hannover, Wuppertal Zoo and the SAVA Wildlife Group for their
assistance with funding for the project.
Prof Fosgate, for his assistance with the statistical analysis and patience with the many questions I
kept asking him.
My co-investigators, Prof Stegmann, Prof Sabine Kästner, Dr Maya Kummrow and in particular Dr
Christina Gerlach for their assistance with study design and data collection.
My friends and family for their support and assistance, without whom I could not have undertaken
such a project.
Finally, to undoubtedly the best supervisors a person could ask for, I would like to say a special thank
you to Drs Gareth Zeiler and Leith Meyer; right from the beginning they broke down what seemed to
be a daunting task to manageable steps and ably guided me through the research process. This project
wouldn’t have been possible without them, and it definitely would have been a lot less enjoyable.

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Declaration of originality

Full name of student: Roxanne Kate Buck
Student number: 04388402

1. I understand what plagiarism is and am aware of the University’s policy in this regard.

2. I declare that this dissertation is my own original work. Where other people’s work has been
used (either from a printed source, Internet or any other source), this has been properly
acknowledged and referenced in accordance with departmental requirements.

3. I have not used work previously produced by another student or any other person to hand in as
my own.

4. I have not allowed, and will not allow, anyone to copy my work with the intention of passing it
off as his or her own work.

SIGNATURE STUDENT:
Roxanne Buck

SIGNATURE SUPERVISOR:
Gareth Zeiler

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Contents
Acknowledgements ................................................................................................................................ ii
Decleration of originality ...................................................................................................................... iii
List of tables............................................................................................................................................ v
List of figures .......................................................................................................................................... v
List of photos .......................................................................................................................................... v
List of abbreviations .............................................................................................................................. vi
Summary ................................................................................................................................................. 1
Literature review .................................................................................................................................... 3
Current practises in anaesthesia of wild ungulates ............................................................................. 3
Total intravenous anaesthesia ............................................................................................................. 4
Drugs of interest .................................................................................................................................. 4
Outcome of literature review .............................................................................................................. 9
Introduction .......................................................................................................................................... 10
Aims and objectives ........................................................................................................................... 11
Hypotheses ........................................................................................................................................ 12
Benefits arising from the study .......................................................................................................... 12
Materials and methods ........................................................................................................................ 13
Experimental design .......................................................................................................................... 13
Animals .............................................................................................................................................. 13
Housing .............................................................................................................................................. 13
Procedures ......................................................................................................................................... 14
Immobilisation ................................................................................................................................ 15
Instrumentation .............................................................................................................................. 17
Maintenance ................................................................................................................................... 19
Monitoring ...................................................................................................................................... 21
Recovery ......................................................................................................................................... 23
Rescue interventions ......................................................................................................................... 24
Statistics ............................................................................................................................................. 25
Results................................................................................................................................................... 27
Immobilisation phase ......................................................................................................................... 27
Maintenance phase ........................................................................................................................... 28
Recovery phase .................................................................................................................................. 32
Discussion ............................................................................................................................................. 34
Conclusion ............................................................................................................................................ 41
References ............................................................................................................................................ 42
Addendum ............................................................................................................................................ 45
Data collection form .......................................................................................................................... 46
Presentations and publications arising from the study ..................................................................... 52
Animal Ethics Approval Certificate .................................................................................................... 53
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List of tables
Table 1. Scoring system used to describe quality of capture. To allow better description, separate 16
scores were assigned for immobilisation quality and ability to intubate.
Table 2. Scoring system used for quality of recovery following antagonist administration. 24
Table 3. Time intervals and drug dosages reported as median (IQR) for ten impala (Aepyceros 28
melampus) undergoing immobilisation followed by propofol-medetomidine-ketamine TIVA of
120 minute duration.
Table 4. Physiological and calculated parameters of ten impala (Aepyceros melampus) 33
undergoing propofol-medetomidine-ketamine TIVA. Parameters reported as median (IQR) at 30
minute intervals for 120 minute duration of infusion.
List of figures
Figure 1. Spaghetti plots of the propofol infusion rate (mg kg-1 min-1) over time in ten impala 29
(Aepyceros melampus) undergoing a propofol-medetomidine-ketamine TIVA infusion of 120
minute duration. Infusion rate was either increased or decreased by a fixed 20% of the initial rate
(0.2 mg kg-1 min-1) in a stepwise manner in accordance to a positive or negative deep pain response
test, respectively, done at 15 minute intervals. Solid black vertical bars indicate a positive deep
pain response.
Figure 2. a) Heart rate (beats min-1), b) respiratory rate (breaths min-1) and c) mean arterial blood 30
pressure (mmHg) plotted against propofol infusion rate (mg kg-1 min-1; solid green line) over time.
Values are reported as median (IQR) at 5 minute intervals for the entire 120 minute propofol-
medetomidine-ketamine TIVA infusion in ten impala (Aepyceros melampus).
List of photos
Photo 1. The high-walled outdoor enclosure (boma) the impala were housed in for the duration 14
of the trial showing (a) home area and (b) capture area. (*) indicates interconnecting gates.
Photo 2. Setup of spirometer and sidestream gas sampler connected to the end of the ET-tube. 18
Oxygen supply (via feeding tube inserted through ET-tube to depth of thoracic inlet) indicated
by arrow.
Photo 3. Application of vulsellum forceps just below coronary band to test deep pain. 20
Photo 4. Positioning of an impala for recovery. 23

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List of abbreviations
% percentage
> greater than
< less than
= equal to
oC degrees Celsius
µg microgram(s)
boma high-walled outdoor enclosure for housing wild ungulates
cAMP cyclic adenosine monophosphate
ECG electrocardiogram
EDTA ethylenediaminotetreaacetic acid
EtCO end-tidal carbon dioxide tension
2
ET-tube endotracheal tube
F O fractional expired oxygen concentration
E 2
FiO fractional inspired oxygen concentration
2
GABA gamma-aminobutyric acid
HCO - bicarbonate ion
3
IM intramuscular
IQR interquartile range
IV intravenous
kg kilogram(s)
kPa kilo Pascals
L litre(s)
mg milligram(s)
min minute(s)
mL millilitre(s)
mmHg millimetres Mercury
mmol millimole(s)
n number of animals
NMDA N-methyl-D-aspartate
PaCO arterial carbon dioxide tension
2
pH negative log of hydrogen ion concentration
PaO arterial oxygen tension
2
SC subcutaneous
SpO peripheral oxygen haemoglobin saturation
2
Vd respiratory dead space volume (mL)
Vt tidal volume (mL)
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Summary
Propofol-medetomidine-ketamine total intravenous anaesthesia in
thiafentanil-medetomidine immobilised impala (Aepyceros melampus)
of 120 minute duration

By

ROXANNE KATE BUCK

Promoter: Dr Gareth Zeiler
Co-promoter: Dr Leith Meyer
Department: Companion Animal Clinical Studies
Degree: Master of Science (Veterinary Science)

Objective To characterise a propofol-medetomidine-ketamine total intravenous anaesthetic
protocol in impala (Aepyceros melampus).

Study design Prospective clinical study.

Animals Ten adult female impala, weighing 39 (±4) kg.

Materials and methods Impala were immobilised with 2 mg thiafentanil and 2.2 mg
medetomidine via projectile darts. Propofol was given to effect (0.5 mg kg-1 boluses) to allow
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endotracheal intubation, following which oxygen was supplemented at 2 L min-1. Anaesthesia
was maintained with a constant rate infusion of medetomidine and ketamine at 5 μg kg-1 h-1 and
1 mg kg-1 h-1, respectively, and propofol to effect (initially 0.2 mg kg-1 min-1) for a period of 120
minutes. The propofol infusion was titrated according to reaction to nociceptive stimuli every
15 minutes. Cardiopulmonary parameters were monitored continuously and arterial blood gas
samples analysed intermittently. At 120 minutes maintenance the thiafentanil and
medetomidine were antagonised using naltrexone (10:1 thiafentanil) and atipamezole (5:1
medetomidine), respectively, and recoveries scored.

Results All impala were successfully immobilised, with a median (IQR) time to recumbency of
9.6 (7.2-14.4) minutes. The median (IQR) dose of propofol required for intubation was 2.7 (1.9-
3.3) mg kg-1. The propofol-medetomidine-ketamine combination ensured recumbency for the
120 minute period. Propofol titration showed an erratic downward trend; a minimum infusion
rate was not determined. Heart rate, respiratory rate and arterial blood pressure were well
maintained. Arterial blood gas analysis indicated marked hypoxaemia, hypercapnia and acidosis.
All impala regurgitated frequently during the maintenance period. Recovery was calm and rapid
in all animals. Median (IQR) time to standing from antagonist administration was 9.4 (8.2-10.6)
minutes.

Conclusions and clinical relevance A propofol-medetomidine-ketamine combination can
provide adequate anaesthesia for invasive procedures in impala for up to 120 minute duration.
The propofol infusion should begin at 0.2 mg kg-1 min-1 and be titrated to clinical effect. Oxygen
supplementation and airway protection with a cuffed endotracheal tube are essential.

Keywords Aepyceros melampus, impala, ketamine, medetomidine, propofol, TIVA
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Literature review
Current practises in anaesthesia of wild ungulates
Many sedative and anaesthetic protocols have been used in wild ungulates. Traditionally,
injectable anaesthetic agents have been used for immobilisation and short surgical procedures,
with inhalation anaesthesia being used for maintenance during more invasive procedures (Auer
et al. 2010).

A number of drug combinations have been used for immobilisation and occasional maintenance
in wild ungulates. Potent opioids have been widely used to immobilise wild ungulates because
they result in quick immobilisation. However, their use is associated with poor respiration,
muscle rigidity and an inadequate plane of anaesthesia making them unsuitable for prolonged
and intensive surgical procedures (Meyer et al. 2008a). Alternatives, such as combinations of
ketamine and medetomidine have been shown to provide good respiration and muscle
relaxation but the level of anaesthesia may be insufficient for major surgical procedures (Bush
et al. 2004). Thus, despite wide-spread use of injectable agents for immobilisation, there is no
widely accepted injectable protocol for maintenance of anaesthesia.

Inhalation maintenance of anaesthesia in wild ungulates is also not without its disadvantages.
Inhalation agents have been shown to cause dose-dependent respiratory and cardiovascular
depression making their use in high quantities undesirable (Clarke et al. 2014, Dzikiti 2013).
Further, inhalation agents require bulky, sophisticated and expensive equipment such as
anaesthetic machines, which are often impractical in field and zoo settings (Dzikiti 2013).
Inhalation anaesthesia is also associated with increased atmospheric pollution and unscavenged
or incorrectly used machines represent significant occupation health hazards to medical
personnel (Dzikiti 2013).
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Total intravenous anaesthesia
Total intravenous anaesthesia (TIVA) uses only intravenous anaesthetic agents to maintain an
adequate depth of anaesthesia (Dzikiti 2013). TIVA requires less equipment than inhalation
maintenance, making it a feasible option for field use. In its simplest form, TIVA requires only an
intravenous catheter and drugs, although endotracheal intubation and oxygen supplementation
are recommended during anaesthesia (Larenza et al. 2005) and infusion pumps allow increased
precision in drug delivery (Dzikiti 2013). TIVA also lends itself to balanced anaesthesia protocols,
whereby several drugs are combined at lower than normal doses to decrease the adverse side
effects of each drug while still achieving the desired level of effect (Dzikiti 2013). TIVA protocols
are also often associated with a smoother recovery (Dzikiti 2013). Drugs used to maintain TIVA
should be short acting, non-accumulative, easy to titrate, quickly redistributed from the central
compartment or metabolised and have a high therapeutic index (Clarke et al. 2014). Currently,
there is scant information in the scientific literature detailing TIVA protocols in wild ungulates
(Auer et al. 2010).

Drugs of interest
A novel protocol for maintenance of anaesthesia in wild ungulates is a propofol-medetomidine-
ketamine total intravenous infusion.

Propofol (2,6-di-isopropylphenol) is an ultra-short acting injectable anaesthetic agent that
induces central nervous system depression by enhancing the effects of the inhibitory
neurotransmitter γ-aminobutyric-acid (GABA) through binding to GABA receptors (Clarke et al.
A
2014). GABA receptors are pentameric membrane proteins found throughout the central
A
nervous system that function as GABA-gated chloride channels, which when activated cause a
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