Abstract
Purpose
To determine if central sympathetic blockade by dexmedetomidine, a selective alpha2 adrenergic receptor agonist, prevents cardiac dysfunction associated with intracranial hypertension (ICH) in a rat model.
Methods
Following intracisternal administration of dexmedetomidine (1 μg · μl−1, 10 μL volume) or the stereoisomer levomedetomidine (1 μg· μL−1, 10 μL volume) in halothane-anesthetized rats, a subdural balloon catheter was inflated for 60 sec to produce ICH. Intracranial pressure, hemodynamic, left ventricular (LV) pressures and electrocardiographic (ECG) changes were recorded. Plasma and myocardial catecholamines and malondialdehyde (MDA) levels were measured.
Results
After levomedetomidine administration, subdural balloon inflation precipitated an increase in mean arterial pressure (149 ± 33% of baseline), heart rate (122 ± 19% of baseline), LV systolic pressure (LVP), LV end-diastolic pressure (LVEDP), LV developed pressure (LVDP), LV dP/dtmax and rate pressure product (RPP) (132 ± 19%, 260 ± 142%, 119 ± 15%, 126 ± 24% and 146 ± 33% of baseline value, respectively). ICH decelerated LVP fall (τ), as t increased from 7.75 ± 1. 1 to 14.37 ± 4.5 msec. Moreover, plasma norepinephrine levels were elevated ( 169 ± 50% of baseline) and there was the appearance of cardiac dysrhythmias and other ECG abnormalities. This response was transient and cardiac function deteriorated in a temporal manner. Intracisternal dexmedetomidine prevented the rise in plasma norepinephrine, blocked the ECG abnormalities, and preserved cardiac function. Moreover, dexmedetomidine attenuated the rise in MDA levels.
Conclusions
The results demonstrate that dexmedetomidine attenuates cardiac dysfunction associated with ICH. Our results provide evidence for the role of central sympathetic hyperactivity in the development of cardiac dysfunction associated with ICH.
Résumé
Objectif
Déterminer si !e biocage sympathique central par ia dexmédétomidine, un agoniste sélectif des récepteurs alpha2 adrénergiques, prévient ia dysfonction cardiaque associée à l’hypertension intracrânienne (HIC) chez un modèle rat.
Méthode
Après l’administration intradstemale de dexmédétomidine (1 μg · μL−1, volume de 10μL) ou du stéréoisomère lévomédétomidine (1 μg · μL−1, volume de 10 μL) chez des rats anesthésiés à l’halothane, un cathéter sous-dural à ballonnet a été gonflé pendant 60 s pour produire une HIC. La pression intracrânienne, l’hémodynamique, les pressions ventriculaires gauches (VG) et les changements électrocardiographiques (ECG) ont été enregistrés. Les niveaux plasmatiques et myocardiques de catécholamines et de malondialdéhyde (MDA) ont été mesurés.
Résultats
Après l’administration de lévomédétomidine, le gonflement du ballonnet sous-dural a précipité une hausse de la tension artérielle moyenne (149 ± 33 % des mesures de base), de la fréquence cardiaque (122 ± 19 % de la base), la tension systolique VG (TVG), la tension télédiastolique VG (TTDVG), la tension développée du VG (TDVG), dP/dtmax VG et le produit tension-fréquence cardiaque PJF (132 ± 19%, 260 ± 142 %, 119 ± 15 %, 126 ± 24% et 146 ± 33% des valeurs de base, respectivement). L’HIC a décéléré la chute de la TVG (τ), à mesure que t augmentait de 7,75 ± 1,1 à 14,37 ± 4,5 msec. De plus, les niveaux plasmatiques de norépinéphrine étaient élevés (169 ± 50 % de la base) et des dysrythmies cardiaques sont apparues avec d’autres anomalies ECG. La réaction a été une détérioration transitoire de la fonction cardiaque d’une manière temporelle. La dexmédétomidine intracisternale a empêché l’élévation de norépinéphrine plasmatique, bloqué les anomalies ECG et préservé la fonction cardiaque. La dexmédétomidine a diminué la hausse des niveaux de MDA.
Conclusion
Les résultats démontrent que la dexmédétomidine atténue la dysfonction cardiaque associée à HIC. Ils mettent en évidence le rôle de l’hyperactivité sympathique centrale dans le développement de dysfonction cardiaque associée à l’HIC.
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Preliminary results of this study were previously presented at the 49th Annual Canadian Anesthesiologists’ Society (CAS) Meeting, June 1, 2002, Victoria, British Columbia, Canada.
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Hall, S.R.R., Wang, L., Milne, B. et al. Central dexmedetomidine attenuates cardiac dysfunction in a rodent model of intracranial hypertension. Can J Anesth 51, 1025–1033 (2004). https://doi.org/10.1007/BF03018493
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DOI: https://doi.org/10.1007/BF03018493