Anestesia em felinos

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Arq. Bras. Med. Vet. Zootec., v.77, n.1, e13090, 2025 
 
Echocardiographic evaluation of healthy cats under the effect of 
Dexmedetomidine and Butorphanol 
 
[Avaliação ecocardiográfica de gatos hígidos sob efeito de 
dexmedetomidina e butorfanol] 
 
L.I. Pereira
1
, M.C.R. Milano
2*
, C.H. Oliveira
3
, A.M. Amude
3
, 
A.K. Fabretti
3
, D.A.G. Kemper
3
 
 
1Universidade Pitágoras Unopar Anhanguera, Arapongas, PR, Brasil 
2Undergraduate, Universidade Pitágoras Unopar Anhanguera, Arapongas, PR, Brasil 
3Graduate, Universidade Pitágoras Unopar Anhanguera, Arapongas, PR, Brasil 

 
ABSTRACT 
 
The study aimed to evaluate the applicability of the association of two classes of drugs. Ten healthy cats 
were used, who underwent echocardiographic evaluation and measurement of systemic blood pressure at 
baseline and after administration of dexmedetomidine at a dose of (10 mcg/kg) and butorphanol at a dose 
of (0.4mg/kg) intramuscularly. In the results obtained, there was a 12% decrease in free wall thickness in 
diastole in M mode (p=0.017), in addition to a 47% decrease in heart rate (pin the 
radioulnar region, and the width of the cuff 
should correspond to 30% to 40% of that 
measurement. The Doppler probe was 
positioned in the palmar region of the 
metacarpa proximal to the pad, to identify the 
arterial pulse and subsequently the measurement 
was performed. 
 
 
Echocardiographic evaluation… 
Arq. Bras. Med. Vet. Zootec., v.77, n.1, 2025 3 
Table 1. Criteria for assessing the sedation score in cats 
Criteria Score 
No sedation, normal movement 0 
Slight ataxia, able to stand 1 
Severa ataxia, sternal recumbency 2 
Lateral recumbency, strong response to stimuli 3 
Lateral decubitus, moderate response to stimuli 4 
Lateral recumbency, no response to stimuli 5 
 
The cats were positioned in sternal decubitus and 
the measurement was performed on the left 
forelimb, with at least five consecutive 
measurements being taken, for late calculation of 
the mean arterial pressures. 
 
The echocardiographic examination, which was 
conducted by an experienced cardiologist 
veterinarian, with the MySono U6® 2 
equipment, using the pediatric sector transducer. 
 
The cats were positioned in lateral decubitus and 
the echocardiographic evaluation was performed 
using the transthoracic pattern using the M-
mode, two-dimensional mode and spectral 
Doppler techniques. The echocardiographic 
examination began in the right parasternal 
region, in the cross-section of the left ventricle 
(LV) at the level of the chorda tendineae, 
focusing the ultrasound beam between the 
papillary muscles for the M-mod analysis of the 
thickness of the interventricular septum in 
diastole (IVSd), diameter of the left ventricle in 
systole (DVEs), diameter of the left ventricle in 
diastole (DVEd) and free wall thickness in 
diastole (PLd) through the formula DVEd – 
DVEs / DVEd x 100 (Madron, 2016a). 
 
In two-dimensional mode in the right parasternal 
region in the cross-section at the level of the 
aortic valve, the left atrium diameter at the end of 
systole (AE), aortic diameter at the end of systole 
(Ao), left atrium and aorta ratio (AE/ Ao) (Selmi 
et al., 2003), and aortic valve area (AVA). The 
transpulmonary flow was analyzed using the 
pulsed spectral Doppler method, focusing the 
ultrasound beam between the pulmonary valve 
leaflets in a cross-section, thus obtaining the 
maximum velocity of this flow (Madron, 2016a), 
in addition to the acceleration time (TA), the 
time ejection (ET) and pulmonary TA/ET ratio 
(Chetboul, 2016a). And in the longitudinal 
section, the SIVd thickness, PLd thickness and 
LA diameter at the end of systole were measured 
(Freeman et al., 2015). 
In the left parasternal region, the transmitral flow 
was evaluated in the apical four- chamber view, 
using pulsed Doppler to obtain the E, A waves 
and the E/A ratio (Afonso and Reis, 2012). In 
the same image, the measurement of the time 
between closing and opening of the mitral valve 
(MCO) was performed, which was used to 
calculate the myocardial performance index 
(TEI) (Madron, 2016c). Subsequently, the 
Doppler beam was positioned so that it reached 
the aorta and mitral valve flows simultaneously, 
in the apical five-chamber position for measuring 
the isovolumetric relaxation time (IVRT) 
(Madron, 2016a). 
 
The transaortic flow was performed with the 
pulsed Doppler beam incident parallel to the 
aorta flow in the apical five-chamber view, to 
identify the maximum velocity of this flow 
(Madron, 2016c), and the TE of the aorta artery, 
thus being able to calculate the TEI index, for 
half of the TEI index formula = MCO – aortic 
TE / aortic TE (Madron, 2016b). With regard to 
pulsed tissue Doppler, the analysis was 
performed at the insertion of the mitral valve 
with the LV free wall in the apical four- chamber 
image, obtaining the E', A', S' waves and the 
A'/E' ratio (Chetboul, 2016b). 
 
The systolic volume (SV) value could be 
measured using the following formula: aortic 
velocity integral time (VTI) multiplied by the 
aortic valve area (AVA). And cardiac output 
(CO) was calculated using the formula CO 
volume = SV x HR. 
 
Statistical analysis of the echocardiographic 
parameters were performed using the GraphPad 
Prism® software, with the Student's t test, and 
for all analyzes a significance level of 5% of 
probability was considered. 
 
Pereira et al. 
4 Arq. Bras. Med. Vet. Zootec., v.77, n.1, 2025 
RESULTS AND DISCUSSION 
 
The study was carried out with 10 adult cats, 
healthy, 7 males and 3 females, castrated, mixed 
breed. The mean body weight was 4.28 kg ± 
0.70 and the mean age was 
34.7 months ± 25.16 and all cats were considered 
clinically healthy after performing the physical 
examination and laboratory tests. 
 
Sedation at 5 minutes reached a mean score of 
2.2 on the sedation table and at 10 minutes, a 
score of 3.6. Sedation was considered 
satisfactory, as it was possible to position the 
cats in lateral decubitus without resistance, only 
one cat had a score of 0 at 5 minutes and at 10 
minutes presented a score of 1 sedation. Good 
muscle relaxation was observed, but all cats 
maintained a slightly decreased muscle tone in 
the limbs. Side effects observed in all cats were 
mydriasis and pale mucous membranes, and one 
cat had nausea. 
 
The mean HR before sedation was 169.5 ± 44.73 
beats per minute (bpm), and after sedation the 
mean was 90 ± 15.19 bpm, demonstrating that 
there was a sharp drop in HR after sedation, with 
statistically significant difference (pin the experiment, in 
addition to promoting excellent muscle 
relaxation. The animals were easily positioned in 
lateral decubitus, with no need for additional 
physical restraint. This effect was possibly 
obtained due to the association of 
dexmedetomidine with butorphanol, as in a study 
carried out by Selmi et al. (2003), in which they 
compared sedation and muscle relaxation in cats 
under the effect of dexmedetomidine alone, at 
the same dose as used in the present study and 
associated with butorphanol (0.2 mg/kg) or 
ketamine (5mg/kg), the authors could conclude 
that dexmedetomidine associated with 
butorphanol or ketamine promoted muscle 
relaxation and significantly greater sedation 
when compared to isolated dexmedetomidine. 
 
 
Echocardiographic evaluation… 
Arq. Bras. Med. Vet. Zootec., v.77, n.1, 2025 5 
Table 2. Echocardiographic variables and systemic blood pressure at baseline and after sedation with 
dexmedetomidine and butorphanol 
Parameters Basal Post DB p- value 
E wave E – cm/s 69.28±13.26 65.87±11.87 0.384 
E wave A – cm/s 44.90±12.26 37.50±9.46 0.060 
E/A 1.58±0.26 1.81±0.34 0.059 
TRIV – ms 43.3±6.56 42.8±6.49 0.696 
E’ – cm/s 8.54±1.89 8.59±1.57 0.943 
A’ – cm/s 4.75±1.06 3.97±0.77 0.112 
E’/A’ 1.84±0.42 2.26±0.64 0.021* 
E’/E’ 8.36±2.15 7.86±1.89 0.387 
S’ – cm/s 6.92±1.90 4.53±1.06 0.007* 
SIVd (modo M0 – cm 0.47±0.06 0.43±0.03 0.166 
DVEd (modo M) – cm 1.56±0.30 1.63±0.22 0.209 
DVEs (modo M) – cm 0.75±0.22 0.97±0.18 0.0003* 
PLd (modo M) – cm 0.42±0.05 0.37±0.05 0.017* 
Maximum aortic velocity - cm/s 90.71±15.68 73.35±11.99 0.015* 
Max lung speed – cm/s 85.60±14.63 62.24±15.24study, the E'/A' ratio increased 
significantly after sedation, which may 
characterize a diastolic dysfunction, however, 
the evaluation of this function should be done 
together with other echocardiographic 
parameters, such as: IVRT, E, A waves and the 
E/A ratio (Madron, 2016b), and such parameters 
Echocardiographic evaluation… 
Arq. Bras. Med. Vet. Zootec., v.77, n.1, 2025 7 
were not altered after the use of associated 
dexmedetomidine to butorphanol in this study. 
 
Regarding the evaluation of the thickness of the 
myocardial wall, it is of great value to emphasize 
the importance of these parameters in felines, 
since most heart diseases in the species is of 
myocardial origin. In addition, the LA size and 
the LA/Ao ratio must be carefully analyzed, as 
they are criteria for classifying the stages of 
these diseases in cats (Fuentes et al., 2020). 
 
In our study, the measurements performed in 
two-dimensional mode of PLd and SIVd did not 
change statistically. In the M mode, the SIVd 
also did not undergo significant modification, 
however, an alteration in the PLd 
measurement was observed, with a value 12% 
lower after sedation. Kellihan et al. (2003) also 
obtained similar findings in dogs using the same 
protocol for sedation, which may suggest that 
due to the decrease in heart rate, the myocardial 
relaxation time is longer, thus being able to 
characterize more reliable measures of PLd. 
 
The measurements made of the LA and the aorta 
in B-mode in the cross-sectional view were not 
altered by the protocol used in this study, in 
agreement with Kellihan et al. (2003) who used 
the same protocol in dogs. And in another study 
that used (40 mcg/kg) dexmedetomidine 
associated with buprenorphine in cats, it also did 
not find alterations in the LA and aorta (Johard et 
al., 2018), seeming to have no important 
influence of dexmedetomidine in these sites. 
 
This work showed significant changes with the 
use of the association of dexmedetomidine with 
butorphanol in felines, but it also presented some 
limitations. The study evaluated the association 
of drugs, but it would be interesting to evaluate 
how each drug behaves individually in the face 
of this analysis. Furthermore, the reduced sample 
size may have interfered with other variables that 
did not show significant values. 
 
However, this work used drugs duly authorized 
and commonly used in association with felines. 
Thus, the results obtained in this study may 
impact the choice of the veterinary 
anesthesiologist regarding the use of this 
protocol for feline sedation. 
 
CONCLUSION 
 
There were changes in indirect 
echocardiographic signs that indicate an 
increased probability of pulmonary hypertension. 
 
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