Surgical Preparation of a Permanent Carotid Transposition in Sheep

doi:10.4236/ss.2011.27088

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Surgical Science, 2011, 2, 402-405

doi:10.4236/ss.2011.27088 Published Online September 2011 (http://www.SciRP.org/journal/ss)

Surgical Preparation of a Permanent Carotid

Transposition in Sheep

Liana V. Gouvêa, Ernane P. F. Novais, Ceci R. Leite, Fábio H. B. Ximenes,

Ricardo M. Almeida, R. B. Molás, J. G. C. Palermo, C. E. V. Silva,

Jose R. J. Borges, Eduardo M. M. Lima, Roberta Ferro Godoy

Large Animal Hospital, School of Veterinary Medicine, University of Brasilia, Brasilia, Brazil

E-mail: [email protected]

Received August 3, 2011; revised September 1, 2011; accepted September 10, 2011

Abstract

In large animal research, when frequent sampling of arterial blood is needed, the carotid artery transposition

is the most used technique. The objective of this paper is to describe a new technique for carotid artery

transposition in sheep and evaluate its effectiveness using the echo-Doppler ultrasound. The animals enrolled

in this study had their carotid surgically elevated to the subcutaneous level, by suturing underneath muscles

sternocephalic and brachiocephalic. None of the animals that underwent the procedure in this study had

trans- or postoperative complications. Six months after the suture removal, all animals presented patent ca-

rotids by echo-Doppler ultrasound. This is an easy and safe procedure for carrying out experiments that re-

quire the collection of arterial blood.

Keywords: Blood Gas Analysis, Eco-Doppler, Experimental Surgery

1. Introduction

Easy and rapid access to large-caliber arteries are fre-

quently needed in invasive studies about hemodynamics

and/or blood gas analysis in large animals, especially if

multiple samples are required. These arteries should be

accessible, but protected from trauma, and their patency

should be maintained for long periods [1]. Several de-

scriptions of displacement of the carotid artery to the

subcutaneous tissue of ruminants have been reported in

the literature [2-8]. Although this is a well studied tech-

nique, a new choice for this procedure allowing a patent

carotid artery for a prolonged time is presented, as well

as minimum complication is observed.

In the technique described in [4], an incision is made

parallel and ventral to the jugular vein, in the transition

between the midd le and d istal third of th e jugu lar groove.

The carotid artery is located and a 10 cm section is ex-

ternalized. The dorsal and the ventral margin of the

esternocephalic and brachiocephalic muscles are sutured

underneath the artery and above the jugular. The skin is

sutured over the carotid artery. The disadvantage of this

technique is that the carotid is not immobilized in the

subcutaneous tissue, hindering the collection of arterial

blood [1].

There is another described a technique [2] that differs

from the previous by suturing the skin under de carotid

artery, creating a skin tube containing the carotid artery.

This technique requires wrapping the animal’s neck to

prevent accidental puncture of the artery. Problems were

reported like skin necrosis and flow disturbances with

this technique, and the first two studies have reported

accidental carotid puncture [1,2,7].

A third technique described in [1], a modification of

the technique originally proposed in [3]. The incision

was made parallel and ventral to the jugular groove to

allow the identification of the jugular vein. The skin is

dissected, creating a flap which is folded dorsally. The

carotid artery is then isolated and displaced as in the

other techniques. The skin flap is returned to its original

position and the skin on top of the exposed carotid artery

is sutured around it. This technique has a lower risk of

accidental perforation of the carotid due to the way that

the artery is positioned.

A work [9] reported 94% success rate after surgery

relocation of carotid artery using the techniques from [2]

and [3]. However, it reported also complications includ-

ing skin necrosis and loss of arterial patency. The ideal

technique would be able to maintain the viability of the

carotid artery for a long period of time. The aim of this

L. V. GOUVÊA ET AL.

403

paper is to describe a new technique for transposition of

the carotid artery in sheep and evaluate its effectiveness

using the apparatus of ultrasound with echo-Doppler.

2. Material and Methods

This study was approved by the Ethics Committee on

Animal Use (CEUA), at the University of Brasília (Bra-

zil), under protocol 76850/2007.

2.1. Experimental Group

We used seven adult Santa Inês sheep with body mass

between 36 and 42 kg. Healthy status was determined by

physical exam, complete blood count, biochemistry

panel, and fecal flotation exam. Animals were kept in

confinement and were fed twice a day with Tifton grass,

water and salt ad libitum during the experiment. They

were monitored daily pre and postoperatively by physical

examination.

2.2. Anaesthetic Procedure and Monitoring

The animals were food fasted for 18 hours and water

fasted 8 hours before the procedure. The premedication

consisted of acepromazine (1% Acepran, Univet S/A, São

Paulo, Brazil) at the dose of 0.1 mg/Kg, IV. Anesthe- sia

was induced with propofol (Propovan, Crystal, Itapira,

Brazil) at the dose of 4.4 mg/Kg IV. The intubation time

provided by this protocol was 5 minutes. The animal was

intubated with the aid of a laryngoscope, endotracheal

tube 7.5 with an ext ensi on an d a g ui de wire.

Anesthesia was maintained with isoflurane (Isoforine,

Crystal, Itapira, Brazil) in 100% oxygen through a uni-

versal vaporizer and all animals were subjected to inter-

mittent positive pressure ventilation (Conquest Slim Fan,

HB Hospitalar, São Paulo, Brazil) with flow of 15

mL·kg·min–1 O2. The airway pressure was kept within 20

cm H2O, with a tidal volume of 15 mL/kg and I:E ratio

was 1:3.

Monitors with heart rate (CardioPET, R & D Mediq

Ltda., São Paulo, Brazil) and SpO2 measurements (Active

“ES”, Transform Advanced Technology Ltda., São Paulo,

Brazil) were used to monitor the anesthesia. Respiratory

rate and body temperature were also registered. Medium

arterial pressure (MAP) was measured with vascular

Doppler (Vet-Dop, VMED, Mill Creek, USA) positioned

over the right metatarsal artery.

2.3. Surgical Procedure

The animals were positioned in left lateral recumbency.

The animal’s head was positioned partly outside the sur-

gical bed providing a proper slope for drainage of the

saliva produced, preventing its accumulation.

Due to the proximity of left common carotid artery to

the esophagus, the right carotid artery was chosen for

this procedure which is easier to be exposed. An area of

about 15 × 20 cm in the region of the jugular groove, in

the right middle third of the neck, was shaved and pre-

pared for surgery with Polyvinylpyrrolidone topic (Rio-

deine, Rioquímica Pharmaceutical Industry, São Jose do

Rio Preto, Brazil) and iodine alcohol.

An incision of approximately 15 cm in a half-moon

shape was made in the skin (Figure 1) involving the

jugular groove. The skin and subcutaneous tissue was

retracted for the identification of th e jugular vein (Figure

2). The jugular was displaced dorsally to allow the ob-

servation of the carotid artery. In a segment of approxi-

mately 10 cm of the carotid artery, small branches from

the artery were sutured with Vicryl 2 - 0 (Vicryl Ethicon,

Johnson & Johnson, São José dos Campos, Brazil) to

prevent bleeding.

The vagosimpathetic branch passing close to the ca-

rotid artery was identified and carefully dissected dor-

sally to avoid injury. The dorsal margins of the esterno-

cephalic muscle fascia and brachiocephalic ventral mar-

gin were sutured underneath the carotid and over the

jugular vein with 2 - 0 Vicryl in a simple continuous

pattern, keeping the segment of the artery near the skin

and covering the jugular vein (Figure 3). Finally, the

reduction of subcutaneous space was performed with

Vicryl 2 - 0 and the epidermal suture with 0 nylon in a

simple continuous pattern concluded the procedure.

2.4. Post-Operative Care

After surgery, the animals received cryotherapy for 15

minutes at the site of transposition, 10 mg/animal of

Figure 1. Incision in a half-moon shape in the skin sur-

rounding the jugular groove (dashed line).

404 L. V. GOUVÊA ET AL.

Figure 2. Identification of the jugular vein (black arrow).

Figure 3. Isolation of the carotid artery and suture of

esternocephalic and brachiocephalic muscle fascias cover-

ing the jugular vein.

dexamethasone (Dexacort, Marcolab, Sao Sebastiao do

Paraiso, Brazil), IV, single dose, to avoid severe edema

of the manipulated area, and 5 mg/kg of enrofloxacin

(Zelotril 10%, National Union Pharmaceutical Chemistry,

Embu Guaçu, Brazil), IM, every 24 hours for seven days.

Dressings were applied daily with topical 0.1% polyvi-

nylpyrrolidone (Riodeíne, Rioquímica Pharmaceutical

Industry, São José do Rio Preto, Brazil), and the suture

was removed approximately ten days after the surgery.

Animals were examined by eco-Doppler ultrasono-

graphy (SonoHeart ELITE, SonoSite, USA) with a

transducer frequency bandwidth of 4 - 7 MHz after su-

ture removal and after six months of the surgical pro-

cedure to assess the p atency of carotid blood flow and to

measure the distance between the luminal and epidermis.

3. Results and Discussion

The technique used on this study was described in horses

[10] and was easily performed without major complica-

tions.

Other authors [1,2,7,9] described post-surgical com-

plications of arterial transposition, such as skin necrosis,

abscess formation, peri-arterial hematoma, and accident-

tal puncture of the carotid artery. None of the animals in

this experiment had postoperative complications, possi-

bly by postoperative procedures performed which in-

cluded the use of dexamethasone, antibiotic therapy, and

cryotherapy.

In all animals, blood flow in the carotid artery was

present, securing its patency. The distance between the

carotid artery and skin was measured and was less than

0.5 cm in all animals (Figure 4).

According to [1] the effectiveness of a transposition

technique is verified by the patency of the carotid artery

for a long time, allowing the animals to be used experi-

mentally. In our experiment the carotid artery was evalu-

ated for a period of six months, with maintenance of

patency in all animals (100%), while [9] had 94% suc-

cess with other technique.

So far, three years after the transposition, each animal

had the carotid catheterized approximately twenty times

for sequential collections during experiments involving

anesthesia and acid-base imbalances. In all these times

the artery was easily identified by its pulsation and no

difficulty found in placing the 16 G catheter. With an

aneroid sphygmomanometer (Premium Instruments Co.

Ltd., Wenzhou., China) arterial pressure could be meas-

ured and the blood flow obtained in all catheterizations

was similar to the first one, indicating that the artery’s

lumen was maintained.

The technique described in this work for permanent

carotid transposition in sheep proved to be easy to per-

form, allowing the adequate repositioning of the carotid

Figure 4. Image obtained with the echo-doppler ultrasound

system. Normal blood flow of carotid artery (in red) and the

distance between the carotid and skin (dashed line) of 0.48

cm are shown. Image obtained after suture removal.

L. V. GOUVÊA ET AL.

405

artery for experiments that require multiple and frequent

arterial blood collection.

4. Acknowledgements

The authors thank the Dean for Research and Graduate

College of the University of Brasília, CNPq for fellow-

ships and undergraduate research and FINATEC for fi-

nancial support.

5. References

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[8] G. L. McClymont, “A Note of the Establishment of Ca-

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