Biomedical Engineering Reference
In-Depth Information
procedures and other procedures requiring profound
muscular relaxation, such as the recording of visual evoked
responses where the eye must remain central and immobile.
A variety of nondepolarizing NMBAs have been used
successfully in nonhuman primates, including rocuronium
and its “reversal” agent sugammadex (
de Boer et al., 2006
),
which enable more rapid recovery of skeletal muscle
function than other reversal agents following cessation of
the blocking agent. Animals will need to be ventilated, and
it is essential to ensure that the blocking agent has worn off
or its action has been reversed (see section “Reversal
agents” above) before anesthesia is ceased. The degree of
blockade can be monitored using a peripheral nerve stim-
ulator (see
Martinez and Keegan, 2007
, for more details).
Placement on the medial aspect of the elbow or on the wrist
in larger primates allows both the degree of block and the
effects of reversal to be monitored reliably. The monitor
measures the reflex response of the muscle to a specific
pattern of electrical stimulation but does not give infor-
mation regarding the depth of anesthesia.
During neuromuscular blockade motor reflex responses
are absent and cannot be used to assess appropriate depth of
anesthesia, so it is important that personnel receive specific
training before using them. Neuromuscular blocking agents
must not be given until a steady state of sufficient depth of
anesthesia has been reached. Depth of anesthesia should be
monitored using a combination of autonomic reflex
responses to noxious stimuli (heart rate and blood pressure)
and electroencephalography (see section “Assessing anes-
thetic depth” below) if available.
For a guide to drug doses see
Table 17.5
.
additional incremental doses of propofol or alphaxalone
(approximately 10
e
20% of the initial induction dose) as
needed. Alternatively administer sevoflurane or isoflurane,
initially at low concentrations, 1% sevoflurane or 0.5%
isoflurane. Gradually increase the vaporizer setting as the
effects of the propofol or alphaxalone subside, typically to
2
e
3% sevoflurane, 1.5% isoflurane.
Medium Duration Procedures (1
e
4 Hours) Surgical
Anesthesia
Immobilization
See “Immobilization” above, but could
also use ketamine/medetomidine given as a single injection
(Old World primate).
Induction of Anesthesia
See “Induction of Anesthesia”
above.
Anesthetic Maintenance
See “Anesthetic Maintenance”
above, but could also concurrently administer a continuous
infusion of propofol (which enables reduction of volatile
agent) or a full mu opioid agonist (provides analgesia and
enables reduction of volatile agent). If an opioid is used do
not give buprenorphine as pre-anesthetic medication as it
will partially reverse the effect of the infused opioid.
Mechanical ventilation advised if continuous infusion of
propofol or opioid used and/or procedures lasting more
than 2
e
3 hours.
Long Duration Procedures (
4 Hours) Surgical
>
Anesthesia
Suggested Anesthetic Protocols
Brief Procedures (10
e
60 Minutes) Surgical Anesthesia
Pre-anesthetic Medication
See “Volatile liquid and gas
anesthetics” above.
Induction of Anesthesia
See “Injectable anesthetics”
above.
Immobilization
Ketamine (Old World Primate),
Alphaxalone (New World Primates) After immobilization/
sedation has been achieved, administer pre-emptive
analgesia (buprenorphine or meloxicam or both agents in
combination depending upon the anticipated degree of
postoperative pain).
Anesthetic Maintenance
See “Volatile liquid and gas
anesthetics” above. The amount of anesthetic agent
required depends on the level of surgical stimulation but
generally decreases during prolonged procedures. Reas-
sessment of physiological parameters and adjustment of
dose is therefore essential in order to avoid over anesthe-
tizing the animal. If buprenorphine is used, repeat admin-
istration every 6
e
8 h during the procedure. Mechanical
ventilation is advised.
Induction of Anesthesia
Place intravenous cannula,
deliver oxygen via a face-mask and administer either pro-
pofol (both groups) or additional alphaxalone (New World
Primates) to deepen anesthesia. Place an endotracheal tube,
connect to an appropriate breathing system (e.g. a T-piece
or Bain's circuit, see section “Endotracheal intubation”
below) and continue to administer oxygen.
Postoperative Analgesia
Administer buprenorphine (i.m.): usually every 8 hours for
1
e
2 doses beginning 8 hours after last intraoperative dose
and meloxicam (per os): usually every 24 hours for 2
e
3
doses beginning 24 hours after preoperative dose. Precise
Anesthetic Maintenance
No additional agents are likely
to be needed for very short (10
e
15 minute) procedures.
To
extend
the
duration
of
anesthesia,
administer
