Biomedical Engineering Reference
In-Depth Information
extremely wide range of studies in the areas of funda-
mental biology, applied research, and toxicology
(
Academy of Medical Sciences, 2006
). The majority of
procedures carried out during the course of these studies
do not require anesthesia. However, when required, it is
essential that the most appropriate and effective methods
of anesthesia and analgesia be employed. As in other
species, refining research procedures by careful selection
of anesthesic and analgesic methods not only contributes
to improving animal welfare, but also improves the quality
of scientific data that is obtained, thereby maximizing the
benefit from the use of nonhuman primates in biomedical
research. The authors' aim in writing this chapter is to
provide a guide to the general principles of good anes-
thetic practice, indicate how this needs to be integrated
into an overall plan of perioperative care, and highlight
some of the challenges specific to anesthetizing nonhuman
primates.
Laule et al., 2003; Wolfensohn and Honess, 2005
). PRT
may also be used to increase cooperation with physical
restraint methods such as squeeze-back cages or pole
and collar methods during induction of anesthesia. This
not only lessens the stress associated with these
methods but may reduce variation in the physiological
response to anesthetic induction by attenuating the
release of cortisol (
Elvidge et al., 1976; Reinhardt
et al., 1991
) just prior to administration of the drugs;
although controlled studies of this have apparently not
been carried out in nonhuman primates.
Overall Aim of General Anesthesia
For procedures in which anesthesia is necessary, the choice
of anesthetic may be constrained by the requirements of the
specific procedure. In general, a balanced anesthetic
procedure, using a combination of drugs allowing a reduc-
tion in dosing of each individual drug, will produce optimal
results. The criteria for evaluating the success of an anes-
thetic is maintenance of normal physiology during anes-
thesia, with the exception of loss of consciousness, and
a return to normal behavior and physiology as soon as
possible after the procedure. Again, these criteria are con-
strained by the particular requirements of the procedure,
but they serve as useful guidelines for evaluating and
refining anesthetic protocols.
Is Anesthesia Necessary?
All anesthetic agents depress cardiovascular and respira-
tory function to a greater or lesser extent. In addition to this
dose-dependent physiological impairment, they disrupt
other homeostatic mechanisms such as thermoregulation
and electrolyte balance. Anesthetic agents also have indi-
rect effects, such as alterations in immune, inflammatory,
and metabolic processes and can be neurotoxic. These
effects can continue to disrupt normal function even after
the anesthetic agents have been excreted from the body.
For this reason, the first step in designing an anesthetic
protocol is to decide whether anesthesia is in fact
necessary.
There is currently no alternative to anesthesia for
the facilitation of invasive surgical procedures such as
deep vessel cannulation, implantation of telemetric
devices, organ transplantation, and the placement of
cranial or spinal implants. For these situations it is
important to focus on minimizing any unwanted effects
of anesthesia by choosing the most appropriate anes-
thetic regime for the procedure. It is equally important
to monitor the animal during anesthesia so that inter-
ventions can be made to minimize physiological
impairment and support physiological function, for
example by administering fluid or ventilatory support.
However, anesthesia is also used to provide humane
restraint for procedures such as blood sampling, the
administration of drugs, and imaging procedures that
might otherwise lead only to very mild transient pain
and/or distress. For some of these procedures positive
reinforcement training (PRT) to facilitate cooperation
and acclimation of primates to procedural techniques
may provide an alternative to general anesthesia
(
Reinhardt and Cowley, 1992; Reinhardt et al., 2002;
PREANESTHETIC CONSIDERATIONS
Health and Safety
In addition to the obvious risks of physical injury when
handling nonhuman primates, personnel may be exposed
to a number of hazardous and potentially fatal zoonotic
diseases (
Blanchard and Russell-Lodrigue, 2012
). Stan-
dard practice is to treat all macaques as if they may be
infected with Macacine herpesvirus 1(Bvirus)andtotake
relevant precautions in terms of personal protective
equipment (PPE), including gloves and mucous membrane
protection. In particular during induction of anesthesia
there are risks of being scratched, bitten, or contacting oral
secretions.
Other important aspects of health and safety relate
to the physical conditions in the operating theatre and
preparation area, as well as the specific anesthetic
equipment. Physical conditions include whether elec-
trical outlets are grounded and safe for use in “wet”
environments (
Barker and Doyle, 2010
), whether gas
cylinders are adequately secured to the wall or floor,
and so forth. The anesthetic equipment must be
checked, not only to confirm that anesthesia will be
delivered correctly but also to guard against leakage of
anesthetic gases and check for exhausted CO
2
absorber
