Download effect of xylazine-ketamine on arterial blood pressure, arterial blood

Bull Vet Inst Pulawy 49, 481-484, 2005
EFFECT OF XYLAZINE-KETAMINE
ON ARTERIAL BLOOD PRESSURE, ARTERIAL BLOOD PH,
BLOOD GASES, RECTAL TEMPERATURE, HEART
AND RESPIRATORY RATES IN GOATS
FEREIDOON SABERI AFSHAR1, ALI BANIADAM1
AND SEYED PAYAM MARASHIPOUR2
1
Department of Clinical Sciences, 2Graduated of Veterinary Medicine,
Faculty of Veterinary Medicine, Shahid Chamran University, 61355-145 Ahwaz, Iran
e-mail: [email protected]
Received for publication January 24, 2005.
Abstract
The effects of xylazine-ketamine administration on
arterial blood pressure, arterial blood pH, blood gases, rectal
temperature, and heart and respiratory rates were recorded in 5
healthy female goats weighing 17-29 kg. Xylazine (0.2 mg/kg,
i.m.) was administered 15 min prior to ketamine (10 mg/kg,
i.v.). All baseline measurements were taken before the
xylazine administration and were repeated at 5, 15, 30, 45, and
60 min intervals after induction of anaesthesia with ketamine.
It was found that heart rate decreased at 15 to 60 min and
rectal temperature decreased significantly at 30 to 60 min but
respiratory rate did not change significantly. Mean arterial
blood pressure declined significantly at 15 to 60 min after
anaesthesia. PaO2 did not change significantly but PaCO2
values increased significantly at 5, 15, and 60 min. Values of
pH decreased significantly at 5 and 15 min. According to this
study, xylazine-ketamine combination is responsible for
declined arterial blood pressure, bradycardia, increased PaCO2,
decreased pH and hypothermia in anaesthetized goats.
Key words: goats, anaesthesia,
ketamine, physiological functions.
xylazine,
Ketamine can be used for anaesthesia in sheep and
goats without fear of convulsions. Muscle relaxation is
poor, but is improved by sedatives such as diazepam or
xylazine (8). Ketamine has been acclaimed on account
of its safety and its favorable effects upon
cardiovascular and respiratory systems and because of
its sympathomimetic and antiarrhythmic properties, it is
useful in poor-risk and hypovolaemic patients (13).
Xylazine hydrochloride is a typical α2-adrenoreceptor
agonist of the non-opioid group, having analgesic,
sedative and muscle relaxant effects and is used
commonly in clinical practice (16). Sheep and goats are
ideally suited to local anaesthetic techniques under
sedation or manual restraint (21). Ketamine is widely
applied in goat anaesthesia and can be used on its own,
or in combination with xylazine or diazepam (8, 21), in
order to minimize or eliminate some unpleasant effects
such as high muscle tone, trembling, increase in body
temperature, and in intraocular and arterial pressure (11,
12, 16-18, 21).
The aim of this study was to evaluate the effects of
xylazine and ketamine administration on arterial blood
pressure, blood gases, arterial pH, heart and respiratory
rates and rectal temperature in goats.
Material and Methods
This study was carried out on 5 healthy female
Iranian goats weighing 17-29 kg. The goats were placed
in left lateral recumbency for measuring arterial blood
pressures and collecting blood samples. Arterial
catheters flushed with 2/1000 heparin solution were
placed using local anaesthesia into the right carotid
artery via a 5 cm skin incision. Xylazine (0.2 mg/kg
i.m.) was injected 15 min prior to the administration of
ketamine (10 mg/kg, i.v.). All baseline measurements
were taken before the xylazine administration and were
repeated at 5, 15, 30, 45 and 60 min intervals after
induction of anaesthesia with ketamine. Heart and
respiratory rates were recorded with a stethoscope and
counting thorax respiratory movements/min. Rectal
temperature was taken with a digital thermometer.
Baseline heart and respiratory rates and rectal
temperatures were measured prior to the placement of an
arterial catheter under lidocaine induced local
anaesthesia. The blood samples were kept on ice and
blood gases (PaO2, PaCO2) and pH were measured by a
blood gas and acid-base analyzer within 60 min. Pairedsamples T test was used for the analysis of the data and
P value of less than 0.05 was considered to be
statistically significant.
Results
Serial changes of heart and respiratory rates, rectal
temperature, arterial blood pressure, blood gases (PaO2
and PaCO2) and pH values are presented in Table 1.
482
Table 1
Mean physiological values determined in goats before and after treatment
with xylazine (0.2 mg/kg, i.m.) and ketamine (10 mg/kg, i.v.)
Values
Breathing rate
(min-1)
Heart rate
(min-1)
Temperature
(ºC)
Arterial blood
pressure
(mmHg)
PaCO2 (mmHg)
PaO2 (mmHg)
pH
Anaesthesia time (min)
30
45
22.6 ± 15.38
19 ± 10.90
Baseline
20.2± 2.86
5
22.4 ± 9.60
15
25 ± 15.22
114.2 ± 7.09
84.8 ± 20.27
80 ± 17.49*
76.6 ± 11.73*
76 ± 13.26*
74.4 ± 7.79*
39.52 ± 0.35
39.38 ± 0.43
39.22 ± 0.46
38.96 ± 0.41
38.78 ± 0.49
38.48 ± 0.61
134.2 ± 6.83
105.2 ± 25.65
101.8 ± 14.72**
101.8 ± 17.87**
104.8 ± 15.04**
112.4 ± 16.29**
37.98 ± 3.21
57.48 ± 6.99**
54.46 ± 1.47**
50.82 ± 8.95
46.62 ± 7.00
45.64 ± 5.33*
105.54 ± 32.08
83.18 ± 47.50
84.88 ± 30.80
111.20 ± 23.97
98.84 ± 42.56
97.3 ± 31.85
7.345 ± 0.058
7.388 ± 0.059
7.404 ± 0.030
7.374 ± 0.043
7.266 ± 0.041
**
7.301 ± 0.042
**
60
17.1 ± 5.45
* P < 0.05; ** P < 0.01 compared to baseline; ± SD
Although there was no significant difference in
respiratory rate, the mean heart rate decreased
significantly at 15 to 60 min following ketamine
administration (P < 0.05). Mean arterial blood pressure
declined and the decline was highly significant at 15 to
60 min after anesthesia (P < 0.01). Mean PaO2 did not
change significantly but mean PaCO2 values increased at
5, 15 and 60 min (P < 0.05) and the increase was highly
significant (P < 0.01) at 5 and 15 min. Mean pH values
decreased highly significantly at 5 and 15 min (P <
0.01). The anaesthetic combination decreased
significantly the mean rectal temperature at 30 to 60 min
and the decline was highly significant (P < 0.01) at 60
min.
Discussion
The purpose of anaesthesia is to provide reversible
unconsciousness, amnesia, analgesia, and immobility
with minimal risk to the patient. Anaesthetic drugs and
adjutants may, however, compromise patient
homeostasis at unpredictable times and unpredictable
ways (10).
Mild respiratory depression has been reported in
ketamine administration and this is usually manifested
by an increased rate which does not compensate for a
decreased tidal volume. On the other hand, xylazine as a
member of adrenoceptor agonist may produce
tachypnoea (8). The breathing rate per second is of
limited value without some reference to tidal volume
and previous trends because normal rates can vary so
widely. A change in breathing rate is, however, often a
sensitive indicator to some physiologic changes (10). In
this study, the anaesthetic regimen had no significant
influence on respiratory rate, but Kul et al. (16) showed
significant changes at 15, 30 and 60 min after xylazineketamine administration in dogs. The decline of
respiratory rate in rabbits and cats had been showed
previously by Borkowski et al. (3) and Verstegen et al.
(22), respectively.
The results showed that mean heart rate decreased
significantly at 15 to 60 min after xylazine-ketamine
administration. The major side effects of α2adrenoreceptor agonists on the cardiovascular system
may have contributed to the decreased heart rate in this
anaesthetic regimen (8, 16). Although ketamine may
increase the heart rate by the increased sympathetic
activity and decreased vagal tone, xylazine overrides
these effects by excitatory carotid baroreceptor reflex
induced by hypotension and decreased sympathetic and
increased vagal activity. Kul et al. (16) found a
prolonged decrease in the heart rate to 120 min in their
study with xylazine-ketamine administration in dogs and
Moens and Fargetton (17) showed a 27% decrease in the
heart rate at 45 min. The same results in cats had been
obtained previously by Allen et al. (1).
The effects of xylazine on the arterial blood
pressure depend on the relative effects of the central and
peripheral stimulation. There is often an initial
hypertensive phase, followed by a more prolonged
period of arterial hypotension. The hypertensive phase is
not always evident after intramuscular injection,
possibly because of reduced peak blood concentrations
of the drug (8). Ketamine causes a short-lived
vasodepressor response that is followed by longerlasting potent pressor response (2). The depressor phase
of ketamine anaesthesia occurs within the first few
minutes of induction and is due to a direct relaxation of
vascular smooth muscles (2). There have been several
proposed mechanisms for the secondary pressor
response to ketamine, including direct central depression
of baroreceptor activity, thereby reflexively increasing
sympathetic tone and by direct inhibition of
norepinephrine uptake at adrenergic nerve endings,
producing peripheral sympathomimetic actions (23).
However, in the present study sympatholytic activity of
xylazine was more effective than the effects of ketamine
on arterial blood pressure, therefore mean arterial blood
483
pressure declined highly significantly at 15 to 60 min (P
< 0.01). Kul et al. (16) found that xylazine-ketamine
induced a decline in arterial blood pressure lasting 120
min. Kitzman et al. (14) showed that peripheral
vasopressor effects of ketamine are inhibited by xylazine
when two agents are combined, and this finding supports
the present results in the goats.
The analysis of carbon dioxide and oxygen in an
arterial blood sample defines pulmonary function (9).
Ketamine alone or in combination with xylazine has
been shown to cause hypercarbia, acidosis, and a 10% or
greater depression in the PaO2 (24). Both components of
this anaesthetic combination have been shown to cause
hypoventilation when used alone (20, 24). Grant and
Upton (6) did not find any significant changes in arterial
carbon dioxide tension after i.m. administration of
xylazine (50 µg/kg) in conscious sheep but a slight
degree of arterial hypoxaemia with a 10% reduction in
arterial oxygen tension values at 30 min was seen in
their study. In the present study, the anaesthetic
combination produced hypercarbia and acidosis
especially at 5 and 15 min after anaesthesia but PaO2 did
not change significantly. Hypercarbia and acidosis due
to ketamine-xylazine is in agreement with past reports in
rabbits and mice given this anaesthetic (5, 20). A lack of
changes in PaO2 levels, accompanied by a rapid increase
in PaCO2 which is reported in our study causes a
ventilation/perfusion mismatch and it was in accord with
Kolata (15) with diazepam-ketamine i.v. administration
in dogs. On the other hand, some researchers did not
find any change in PaCO2 and PaO2 after administration
of xylazine-ketamine or xylazine in cats and dogs,
respectively (1, 7). Ruminants, especially sheep and
goats, are highly sensitive to the effects of α2adrenoceptor agonists requiring a reduction in dose of
approximately 20 to 40 times when compared to species
such as the cat, dog or horse (6). The difference in drug
effects and drug sensitivity between species may be
responsible to variations in the physiological responses.
On the basis of literature, both ketamine and
xylazine may produce hypothermia (19). In our study
significant decrease in rectal temperature was observed
at 30 to 60 min after anesthesia and the decrease at 60
min was highly significant. The decline in body
temperature is in agreement with Bush et al. (4) when
ketamine was used in non-human primates but Kul et al.
(16) and Wyatt et al. (25) did not find any significant
changes in body temperature after ketamine-xylazine
administration in the dog and rabbit.
This study has shown that ketamine-xylazine
administration in goats depresses the cardiovascular
system and care must be taken in minimizing any
depression which may result from anaesthesia or
surgery. On the other hand, the decline in body
temperature may affect other physiologic parameters,
therefore monitoring of body temperature is essential for
anaesthetized patient.
Acknowledgments: This work was supported
by the Shahid Chamran University of Ahwaz for
Scientific Research, grant No. 111.
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