The

The Veterinary Journal 166 (2003) 273–276

Veterinary Journalwww.elsevier.com/locate/tvjl

The effects of isoflurane anaesthesia on some Doppler-derivedcardiac parameters in the common buzzard (Buteo buteo)

Jens Straub a,*, Neil A. Forbes b, Jens Thielebein c, Michael Pees a,Maria-E. Krautwald-Junghanns a

a Department of Small Animal Medicine, Faculty of Veterinary Medicine, Clinic for Birds and Reptiles, University of Leipzig,

An den Tierkliniken 17, 04103 Leipzig, Germanyb Clockhouse Veterinary Hospital, Wallbridge, Stroud, Gloucestershire GL5 3JD, UK

c Martin-Luther-Universit€aat Halle/Wittenberg, Landwirtschaftliche Fakult€aat, Institut f€uur Tierzucht und Tierhaltung mit Tierklinik,

Emil-Abderhalden-Straße 28, 06108 Halle, Germany

Accepted 13 March 2003

Abstract

In order to gain an initial overview of the influence of anaesthesia on the results of Doppler-derived blood flow measurements in

raptors, the heart rate as well as three different sample volumes of pulsed-wave spectral Doppler-derived flow velocity (diastolic flow

across the left and right atrioventricular valve, systolic flow across the aortic valve) were determined in 10 common buzzards (Buteo

buteo). Measurements were taken once in conscious and once in anaesthetized birds.

Anaesthesia was shown to produce significant changes in cardiac parameters recorded in the same birds whilst conscious. When

comparing conscious birds with each other (with one exception for right sided ventricular inflow velocity) no correlation between the

heart frequency and measured blood flow velocities was evident. This was also the case under anaesthesia. However, significant

differences in these parameters were evident when comparing the results obtained before and under anaesthesia. The results suggest

that the influence of anaesthesia in raptors is more than a simple reduction of heart rate and that there is also reduction in blood flow

velocity.

� 2003 Elsevier Ltd. All rights reserved.

Keywords: Doppler echocardiography; Pulsed-wave spectral Doppler; Anaesthesia; Raptors; Common buzzard

1. Introduction

The establishment of echocardiographical reference

values in non-anaesthetized avian patients is problem-

atic. This is due to variations in levels of �handling-in-duced stress� which are not objectively measurable in

individual birds. To date, the majority of avian echo-

cardiography studies have been conducted under an-

aesthesia (Boskovic et al., 1999; Pees, 2001; Pees et al.,2001; Straub et al., 2001) and the effects of anaesthesia

in avian patients on the results of electrocardiography

are well documented (Altman and Miller, 1979; Harri-

son et al., 1985; Nap et al., 1992; Lumeij and Ritchie,

* Corresponding author. Tel.: +49-341-973-8400; fax: +49-341-973-

8409.

E-mail address: justraub@gmx.de (J. Straub).

1090-0233/$ - see front matter � 2003 Elsevier Ltd. All rights reserved.

doi:10.1016/S1090-0233(03)00074-1

1994; Lukasik et al., 1997; Jaensch et al., 1999). How-ever little is known about the influence of anaesthesia on

cardiology imaging techniques in birds, whereas in

mammals such effects are well described (Chaves et al.,

2001; Hart et al., 2001; Kiatchoosakun et al., 2001; Roth

et al., 2002).

The aim of the present study was to gain a pre-

liminary overview of the effect of anaesthesia on the

results of pulsed-wave spectral Doppler-derived bloodflow in raptors.

2. Materials and methods

Pulsed-wave spectral Doppler-derived blood flow

across heart valves was determined in 10 common buz-

zards (Buteo buteo). All birds were untrained aviary

274 J. Straub et al. / The Veterinary Journal 166 (2003) 273–276

birds. In each bird echocardiography was performedonce prior to induction and once under isoflorane in-

halation anaesthesia (Isoflo, Essex). Anaesthesia was

induced via a mask (5% isoflurane in 1L/min oxygen)

and maintained following intubation (2–3% isoflurane in

1L/min oxygen). All birds were healthy individuals

based on normal physical, B-mode echocardiographical,

electrocardiographical, and radiological examination.

None of the buzzards had a history of cardiovascular orother apparent internal disease.

Echocardiography was performed in dorsal recum-

bency. The bird�s head was covered with a towel and the

legs and wings restrained manually. Bipolar ECG leads

were attached and an electrocardiogram was recorded

continuously as described previously (Boskovic et al.,

1999). Feathers over the abdominal region were parted

and by using conventional water-soluble acoustic cou-pling gel, a micro-curved-array scanner with a frequency

of 7.5 MHz was coupled directly to the bird�s abdomen

just caudal to the sternum. Using a Sonoace 8800

(Kretz-Technik) unit, the ultrasound beam was directed

cranially and craniolaterally in a horizontal and vertical

direction. All examinations were carried out by the same

person in a dimly lit, quiet room.

Initially, vertical and horizontal B-mode images ofthe hearts were obtained. None of the images showed

any deviation from established reference values for

raptors (Boskovic et al., 1999). Pulsed-wave spectral

Doppler examinations were then carried out. Three

different sample volumes, diastolic flow across the left

and right atrioventricular valve, and systolic flow across

the aortic valve, were determined and quantitative

analysis of the blood flow patterns was performed. De-tection of pulmonary artery blood flow was attempted in

all birds.

Table 1

Cardiac parameters of conscious and anaesthetized common buzzards (Bute

No. Sex BM Non-anaesthetized

HF LV RV

1 m 840 420 0.18 0.1

2 m 700 390 0.23 0.2

3 m 890 390 0.22

4 f 1100 300 0.26 0.2

5 m 890 330 0.20 0.1

6 f 1050 390 0.22 0.1

7 f 990 330 0.24 0.1

8 f 1200 270 0.21 0.2

9 m 700 350 0.22 0.2

10 f 1000 360 0.21 0.2

Mean 936 353 0.22 0.2

Min 700 270 0.18 0.1

Max 1200 420 0.26 0.2

SD 155 44 0.02 0.0

No., number; BM, bodymass; HF, heart frequency; LV, Doppler-derived d

right ventricular inflow velocity; AO, Doppler-derived systolic aortic outflo

standard deviation.

For statistical evaluation the SPSS 10.0 program(Statistical Products and Service Solutions) was used.

Results obtained once under and once without anaes-

thesia were compared by ANOVA. A t test for paired

samples was used to evaluate any correlation between

heart frequency and blood flow velocity.

3. Results

Diastolic ventricular inflow into the left ventricle was

detectable in all birds prior to induction as well as under

anaesthesia. Right sided ventricular inflow was detect-

able in nine of 10 birds with or without anaesthesia.

Systolic aortic blood flow was measured in six birds

before and under anaesthesia but blood flow via the

pulmonary artery was not detectable in conscious or inanaesthetized birds.

Anaesthesia produced statistically significant differ-

ences between conscious and the anaesthetized buzzards

in all cardiac parameters determined (Table 1). The

mean heart frequency in non-anaesthetized birds was

110 beats/min (45.3 %) higher than in anaesthetized in-

dividuals (p6 0:001) (Fig. 1). The mean left sided as well

as right sided diastolic ventricular inflow in consciousbuzzards was within the same range (0.20 and 0.22 m/s,

respectively). Thus the increases in these parameters

were highly significant (57.1%, p6 0:001 and 42.9%,

p6 0:001) compared to anaesthetized birds, which

showed mean flow velocities for both areas examined of

0.14 m/s (Figs. 2 and 3). Mean systolic aortic flow prior

to anaesthesia was 0.22 m/s (18.6%) higher than after

induction (p ¼ 0:001) (Fig. 4).Under anaesthesia, no correlation between heart

frequency and measured blood flow velocities was

o buteo)

Anaesthetized

AO HF LV RV AO

5 240 0.11 0.12

1 1.24 210 0.14 0.16 1.20

240 0.15

5 1.27 270 0.13 0.17 1.20

8 1.60 270 0.14 0.15 1.15

9 240 0.15 0.12

8 1.52 240 0.12 0.11 1.25

3 1.35 210 0.14 0.13 1.10

1 260 0.13 0.13 1.15

0 1.40 250 0.14 0.14

0 1.40 243 0.14 0.14 1.18

5 1.24 210 0.11 0.11 1.10

5 1.60 270 0.15 0.17 1.25

3 0.12 20 0.01 0.02 0.05

iastolic left ventricular inflow velocity; RV, Doppler-derived diastoloic

w velocity; m, male; f, female; Min, minimum; Max, maximum; SD,

Fig. 2. Comparison of Doppler-derived diastolic left ventricular inflow

velocity of conscious and anaesthetized common buzzards (Buteo

buteo).

Fig. 3. Comparison of Doppler-derived diastolic right ventricular in-

flow velocity of conscious and anaesthetized common buzzards (Buteo

buteo).

Fig. 1. Comparison of heart frequency of conscious and anaesthetized

common buzzards (Buteo buteo).

Fig. 4. Comparison of Doppler-derived systolic aortic outflow velocity

of conscious and anaesthetized common buzzards (Buteo buteo).

J. Straub et al. / The Veterinary Journal 166 (2003) 273–276 275

evident. Prior to induction of anaesthesia for the com-parison of heart frequency and left sided ventricular

inflow velocity, no correlation was detectable. There was

also no correlation between heart frequency and aortic

blood flow velocity. Only a slight correlation (r ¼ 0:679,p ¼ 0:044) between heart frequency and inflow velocity

into the right ventricle could be shown.

4. Discussion

The practical use of Doppler echocardiography in

common buzzards was not influenced by isoflurane an-

aesthesia. As was suspected and is known in mammals

(Yoon and Yoon, 1998; Raisis et al., 2000; Chaves et al.,

2001; Hart et al., 2001; Kiatchoosakun et al., 2001; Roth

et al., 2002) anaesthesia had a significant influence on theresults of pulsed-wave spectral Doppler-derived blood

flow velocity as well as on the heart frequency in the birds.

All Doppler-derived blood flow velocities were sig-

nificantly lower under anaesthesia. Diastolic ventricular

inflow velocity in the anaesthetized buzzards was lower

than in anaesthetized Amazons (Straub et al., 2001)

(0.14 m/s for ventricular inflow on both sides in buz-

zards, 0.18 and 0.22 m/s for left and right sided inflow,respectively, in psittacines) whilst systolic aortic flow

velocity in the anaesthetized buzzards was higher than in

the unconscious psittacines (1.18 m/s versus 0.83 m/s).

Additional examinations should be undertaken to ex-

amine variations between different avian species; in

small mammals even within one species (e.g., genetically

different strains of mice) differences in Doppler-derived

blood flow measurements occur (Roth et al., 2002).As with blood flow velocities, heart rates were also

significantly lower in anaesthetized birds. Coherence of

heart rate and Doppler-derived velocity has been doc-

umented in dogs with increasing heart rates generally

resulting in increasing velocities. In dogs, the pulmonary

artery was statistically judged as the flow area most

susceptible to such influences. Unfortunately, we were

unable to detect pulmonary artery blood flow in any ofour birds.

Surprisingly neither under nor prior to anaesthesia

was there any correlation between the heart rate and the

measured blood flow velocities, with the exception of the

right sided ventricular inflow. Thus the results suggest

that the reduction of blood flow velocity under anaes-

thesia is most likely not simply the result of anaesthesia-

caused reduction of the heart rate.

Acknowledgements

This study was funded by the DFG (Deutsche Fors-

chungsgemeinschaft). The authors would like to thank

Mr. T Spretke (Halle Zoo) formaking the birds available.

276 J. Straub et al. / The Veterinary Journal 166 (2003) 273–276

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