anesthesia

1. Dr. Layth Mahmoud Alkattan

2. Types of animals were used
 Wide groups of lab animals were used in research
 Rodents and rabbits jointly made up 82.2 %of the
total number of animals used.
 In this group, mice and rats accounted for most of
the animals, comprising 59.4%.
 Cold-blooded organisms – which in this case
generally refers to fish, amphibians, and reptiles).
 The third-most common animals used were birds

4. Preparations for anesthesia
 Good pre-operative care will reduce the incidence
of many of the complications that can occur during
anesthesia, and thorough preparation of facilities
and equipment contributes to the smooth running
of a research protocol.

5.  It is important to consider preparation of not
only the animals to be anaesthetized but also
the equipment, drugs, facilities and personnel
involved in the procedure.

6. Categories of anesthetic risk
Categories Risk
ASAΙ Exultant anesthetic risk Healthy
ASAΙΙ Good anesthetic risk Mild systemic desease
ASAΙΙΙ Fair anesthetic risk Moderate
ASAΙV Poor anesthetic risk Life –threatening
ASAV Guarded anesthetic risk Life expectation during
24 H
ASAVΙ Emergency

7. Effects of anesthesia on the physiological processes
 Anesthesia has profound effects on the physiological
processes of animals, and this can have a marked
effect on experimental data.
 These effects can arise as a direct result of the
anesthetic agents used, for example, hyperglycemia
caused by medetomidine.
 Other effects such as hypothermia may be secondary
to the depression of various body systems.
 Some effects persist only during the period of
anesthesia, other effects may continue for hours or

8.  Sometimes, the effects of a poor choice of
anesthetic agent can be dramatic, for example, ileus
(gut stasis) after administration of chloral hydrate.
 More usually, the effects are less obvious, but
 even subtle changes can result in an increase in the
variability of study data.
 This increased variability can require an increased
number of animals to be used to demonstrate
treatment effects

9. Fasting
 Pre-anesthetic fasting is usually not necessary
for rats due to their inability to vomit.
 However, if fasting is employed limit to no more than
two to three hours due to the high metabolic rate of
small rodents.

10. Dose
 In general, smaller animals have higher metabolic rates and
 frequently require higher doses of anesthetics and analgesics at
more frequent intervals to achieve the desired effect.
 Species, strain and age differences often overshadow this
 general principle however.
 It is always best to start with a drug regimen developed in the sp
ecies, age and strain with which the Principal Investigator is
 working, rather than extrapolate from one species or strain to an
other.

11. Requirements for injectable anesthesia
 Plastic disposable syringes are almost universally used for
delivering anesthetics.
 These single-use syringes should not be resterilized for
further use.
 Ensure that an appropriate-volume syringe is used so that the
required dose of anesthetic can be administered accurately.
 The syringes designed for insulin administration to human
patients are particularly useful for administering small doses
of drugs to rodents

12.  Avoid using syringes which have been stored for a
length of time which exceeds the period
 recommended by the manufacturers, as the plastic
may have become brittle and can fracture during use.

13. Insulin syringe, ‘ butterfly ’ infusion set, catheters and
anesthetic extension line.

14.  Needles and Cannula
 Disposable hypodermic needles should be used and an
appropriate gauge selected for each purpose.
 Needles should never be resterilized, as they rapidly
 become blunt when used and injection with a blunt needle
can cause considerable discomfort.
 Successful venepuncture of small vessels is particularly
difficult to achieve if the needle has been blunted.
 For this reason, it is advisable to replace the needle after
drawing up liquid from a rubber-capped vial.

16. Method of anchoring intravenous catheters on a rabbit ear.
One wing of the catheter is removed, a piece of tape is
laid along the ear across the remaining wing and two
further pieces of tape are wrapped around the ear (c).

17. A double-chamber system that is designed to
minimize exposure of personnel to waste
anaesthetic gases

18.  Inhalant anesthetic :
 Anesthetic ether is now difficult to obtain, although the
agent can still be purchased from specialist suppliers.
 Induction of and recovery from anesthesia are
 relatively slow.
 This is advantageous for inexperienced anesthetists, as it
makes accidental overdose less likely.
 Conversely, a prolonged induction period can
 present problems in restraining the animal, particularly as
most animals strongly resent inhaling the vapor.

19.  Administration of ether stimulates catecholamine
release

20. Monitoring
 Monitoring of general anesthesia becomes more
difficult
 when the patient size is reduced.
 The laboratory animal veterinarian is uniquely tasked
with conducting anesthesia in a wide variety of
species, most of which are small.
 The nature of their small body size makes routine
techniques used to monitor anesthesia (i.e., manual
pulse, observations of respiratory effort, etc.) difficult.

21.  Minimum monitoring should include
 ◦ Heart rate/rhythm and pulse pressure
 ◦ Respiratory rate and pattern
 ◦ CRT/mucous membrane color
 ◦ Temperature
 ◦ Blood loss
 ◦ Anesthetic record

22.  Monitoring anesthesia includes:
 1. Assessing the animal’s responsiveness to painful
stimuli,
 2. Character of respiration, and color of the ears, tail,
mucous membranes, or foot pads, and adjusting
anesthetic depth as needed.
 Pedal withdrawal reflex (toe pinch) is recommended
for assuring adequate depth of anesthesia prior to first
incision and as a repeated check throughout the
procedure.
 Rectal temperature and heart rate should be
monitored electronically during long or involved
procedures.