These in vitro results demonstrate that hydroxythyl starches especially compromise clot polymerisation. The new preparation HES 130/0.4 seems to inhibit platelet function to a lesser extent than hydroxyethyl starch preparations with a higher molecular weight and degree of substitution.

We have investigated the effects of isoflurane and desflurane on neurological outcome in a rat model of incomplete cerebral ischaemia. We studied 40 non-fasted male Sprague-Dawley rats, anaesthetized, intubated and ventilated mechanically with isoflurane and nitrous oxide in oxygen (FlO2 0.3). Arterial and venous catheters were inserted for measurement of arterial pressure, drug administration and blood sampling. A biparietal electroencephalogram (EEG) was recorded continuously using subdermal platinum electrodes. At completion of surgery, administration of isoflurane was discontinued (with the exception of those animals receiving isoflurane as treatment) and rats were allowed an equilibration period of 30 min according to the following procedure: group 1 (n = 10), 66% nitrous oxide in oxygen and fentanyl (bolus 10 micrograms kg-1 i.v. followed by infusion at a rate of 25 micrograms kg-1 h-1); group 2 (n = 10), 1.0 MAC of isoflurane in oxygen (FlO2 0.3) and air; groups 3 and 4 (n = 10 per group), 1.0 MAC or 1.5 MAC of desflurane in oxygen (FlO2 0.3) and air, respectively. Ischaemia was produced by combined unilateral common carotid artery ligation and haemorrhagic hypotension to 35 mm Hg for 30 min. Functional neurological deficit was evaluated for 3 days after cerebral ischaemia. At baseline, brain electrical activity was higher with fentanyl-nitrous oxide, 1.0 MAC of isoflurane and 1.0 MAC of desflurane (groups 1-3) compared with 1.5 MAC of desflurane (group 4). Neurological outcome was improved in isoflurane and desflurane anaesthetized animals (groups 2-4), regardless of the concentration used compared with fentanyl-nitrous oxide anaesthesia (group 1). The increase in plasma epinephrine and norepinephrine concentrations during ischaemia was significantly higher in fentanyl-nitrous oxide anaesthetized animals (group 1) compared with animals who received volatile anaesthetics (groups 2-4). These data suggest that cerebral protection produced by isoflurane and desflurane appears to be related to reduction in sympathetic activity rather than suppression of cerebral metabolic rate.

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572CAN J ANESTH 2000 / 47: 6 / pp [572][573][574][575][576][577][578] Purpose: To determine the effects of the non-competitive NMDA-receptor antagonist S(+)-ketamine on neurological outcome in a rat model of incomplete cerebral ischemia. Methods: Thirty rats were anesthetized, intubated and mechanically ventilated with isoflurane, O 2 30% and nitrous oxide 70%. Following surgery animals were randomly assigned to one of the following treatment groups: Rats in group 1 (n=10, control) received fentanyl (bolus: 10 µg·kg -1 iv; infusion 25 µg·kg -1 ·h -1 ) and N 2 O 70% / O 2 . Rats in group 2 (n=10) received O 2 30% in air and low-dose S(+)-ketamine (infusion: 0.25 mg·kg -1 ·min -1 ). Rats in group 3 (n=10) received O 2 30% in air and high-dose S(+)-ketamine (infusion: 1.0 mg·kg -1 ·min -1 ). Following 30 min equilibration period ischemia was induced by combined unilateral common carotid artery ligation and hemorrhagic hypotension to 35 mmHg for 30 min. Plasma catecholamines were assayed before and at the end of ischemia. Neurological deficit was evaluated for three postischemic days. Results: Neurological outcome was improved with high-dose S(+)-ketamine when compared to fentanyl / N 2 O -anesthetized controls (9 vs 1 stroke related deaths, P < 0.05). Increases in plasma catecholamine concentrations were higher in fentanyl / N 2 O -anesthetized (adrenaline baseline 105.5 ± 92.1 pg·ml -1 , during ischemia 948 ± 602.8 pg·ml -1 , P < 0.05; noradrenaline baseline 407± 120.2 pg·ml -1 , ischemia 1267 ± 422.2 pg·ml -1 , P < 0.05) than in high-dose S(+)-ketamine-treated animals (adrenaline baseline 71 ± 79.5 pg·ml -1 , ischemia 237 ± 131.9; noradrenaline baseline 317.9 ± 310.5 pg·ml -1 , ischemia 310.5 ± 85.7 pg·ml -1 ). Conclusion: Neurological outcome is improved following incomplete cerebral ischemia with S(+)-ketamine. Decreases in neuronal injury may be related to suppression of sympathetic discharge. Résultats : L'évolution neurologique a été meilleure avec de fortes doses de S(+)-kétamine qu'avec l'alfentanyl / N 2 O (9 vs 1 décès reliés à un accident ischémique cérébral, P < 0,05). L'augmentation des concentrations plasmatiques de catécholamines a été plus marquée avec l'alfentanyl / N 2 O (l'adrénaline de base à 105,5 ± 92,1 pg·ml -1 ; pendant l'ischémie, 948 ± 602,8 pg·ml -1 , P < 0,05; la noradrénaline de base à 407± 120,2 pg·ml -1 ; pendant l'ischémie, 1267 ± 422,2 pg·ml -1 , P < 0,05) qu'avec de fortes doses de S(+)-kétamine (l'adrénaline de base à 71 ± 79,5 pg·ml -1 ; pendant l'ischémie, 237 ± 131,9; la noradrénaline de base à 317,9 ± 310,5 pg·ml -1 ; pendant l'ischémie, 310,5 ± 85,7 pg·ml -1 ). Conclusion : L'utilisation de S(+)-kétamine permet une évolution neurologique supérieure après une ischémie cérébrale incomplète. Cette situation peut être reliée à la suppression de décharge sympathique.