Cerebral protection for the preclinical evaluation of a vascular graft in sheep carotid artery model.
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2016-08
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Scandinavian Journal of Laboratory Animal Science
Abstract
A protocol for cerebral protection without systemic hypothermia to aid the safe, smooth and
fast recovery of sheep used for the preclinical evaluation of a prosthetic vascular graft in the
carotid artery is presented in this study. Ten adult Ramnad white sheep (33.8± 3.2 kg) were
green grass deprived and anticoagulated from 5 days prior to surgery with aspirin 150 mg and
clopidogrel 75 mg till the end of the study. Aft er anesthetic premedication and endotracheal
intubation, the animals were ventilated at the rate of 12 breaths/min and tidal volume of 12 ml/
kg. Ten minutes prior to carotid artery clamping (right unilateral internal carotid artery) which
was performed aft er heparinisation, pharmacologic mitigation was done for cerebral protection
with a total dose of thiopentone 50 mg (2.5%), 8 mg dexamethasone, 100 mg hydrocortisone
and 15 ml (7.5% w/v) sodium bicarbonate as i/v bolus and 250 ml dextran 40 (10% w/v) at 40
ml/hour as i/v drip. Mean values of arterial pressure and heart rate were 94±16 mmHg and
88±11 min-1 respectively, over the entire intra operative period. A moderate alkalosis which
occurred in all animals under anaesthesia was postulated to supplement cerebral protection
and was corrected by reducing the respiratory rate and tidal volume to 10 breaths/min and
10ml/kg respectively. Signifi cant variation in pH (p<0.05) was observed at 90, 120, 150 and 180
minutes aft er induction of anaesthesia. Signifi cant variation in MAP (p<0.05) was observed at
180 minutes aft er premedication, which was related to alkalosis and resultant hypokalemia and
was eff ectively corrected with 31±7 meq potassium chloride (40 meq in 500 ml ringer lactate).
Th e total procedure lasted 126±18 minutes and total unilateral right carotid arterial clamping
time was 36.7±6.5 minutes. 28±5 minutes aft er spontaneous respiration, the animals were extubated
and moved to the postoperative cage. Th ree doses of nadroparine 3800 IU s/c at 12
hour intervals were given postoperatively. All animals were free from any neurological defi cits,
which showed the eff ectiveness of the perioperative protocol encompassing the cerebral protective
medication
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Harikrishnan V S and Umashankar P R. Cerebral protection for the preclinical evaluation of a vascular graft in sheep carotid artery model. Scandinavian Journal of Laboratory Animal Science. 2015;41.