Effects of phenylephrine and clonidine on hypoxic hypoxia in anesthetized guinea pigs

Vlaicu Şandor¹, Barbu Cuparencu³, T. Trăistaru¹, M.Semenescu¹, Anca Buzoianu¹, Letiţia Palaghiţă-Banias², L.T.Krausz¹
1) Catedra de Farmacologie şi Toxicologie. 2) Catedra de Anatomie şi Clinica de Neurologie, Universitatea de Medicină şi Farmacie „Iuliu Haţieganu”, Cluj-Napoca. 3) Catedra de Farmacologie, Universitatea din Oradea

Abstract

Objectives. To study the influence of α1 and α2 adrenergic receptor mechanisms on electro-physiologic parameters of heart and brain in transient hypoxic hypoxia.

Material and method. We experimented on 3 groups of anesthetized and curarized guinea pigs in artificial respiration. Two episodes of hypoxic hypoxia were carried out by stopping artificial ventilation for 210 seconds. After 10 minutes from the first hypoxic period we administered intravenously single-doses of: saline (group I); 0.4 µmoles•kg-1 of phenylephrine (group II); 0.4 µmoles•kg-1 of clonidine (group III). After 20 minutes of this treatment we induced the second period of hypoxia. We recorded the latency of relevant ECG and EEG alterations. We used “ANOVA” and “t“ Student’s statistical tests, p < 0.05 being considered significant.

Results.Phenylephrine does not influence ECG and EEG alterations in hypoxic hypoxia. Clonidine delays the onset of hypoxic cardiac arrhythmias and enhances the reestablishment of sinus rhythm in reventilation. Clonidine has no influence on EEG in hypoxia.

Conclusions. α1 adrenergic stimulation by phenylephrine has no antihypoxic effects on the heart and brain. Clonidine, α2 and imidazolinic I1 agonist, has a mild heart-protective effect, but does not protect the brain.

Key words: cardioprotection, cerebroprotection, phenylephrine, clonidine, hypoxia, guinea pigs

Efectele fenilefrinei şi ale clonidinei asupra hipoxiei hipoxice la cobaii anesteziaţi

Jurnalul Român de Anestezie Terapie intensivă 2004 Vol.11 Nr.1, 44-50