José Carlos Dorsa PontesI; Carlos Geraldo Sobral MedeirosII; Otoni M GomesII
DOI: 10.1590/S0102-76381996000400012
RESUMO
OBJETIVO: Estudo experimental das ações farmacodinâmicas do propofol e sua interação com a dopamina e dobutamina em corações isolados de ratos. MÉTODO: Foram estudadas as variações da contratilidade miocárdica (dT/dt), em 30 corações isolados de ratos. Em todos os animais, após anestesia por inalação de éter, os corações foram excisados e perfundidos em sistema de Langendorff com solução de Krebs - Hensleit enriquecida com 95% O2 e 5% CO2, (pressão de 90 cm de H2O, temperatura constante de 37,0ºC ± 0,5ºC). Foram estudados 30 animais divididos em: Grupo I (controle) - 10 corações perfundidos durante 11 minutos com solução de Krebs - Hensleit; Grupo II (dopamina-propofol-dopamina) -10 corações onde foram administrados dopamina (50 mcg/ml) e analisados os resultados nos 1º, 3º e 5º minutos e, posteriormente, propofol, (25 mcg/ml) infundindo-se 1 minuto após, dopamina (50 mcg/ml) e analisando-se os 1º, 3º e 5º minutos. Grupo III (dobutamina-propofol-dobutamina) - diferiu do Grupo II pela substituição da dopamina por dobutamina (50 mcg/ml). RESULTADOS: No Grupo I observou-se que a dT/dt variou de 39,57 ± 3,97 (g.seg-1) a 39,37 ± 3,44 (g.seg-1) (p>0,05) no período estudado. No Grupo II observou-se que, após a administração de propofol e dopamina, a dT/dt em (g.seg-1) apresentou queda de 17,61% (p<0,05) no 1º minuto; 8,37% (p<0,05) no 3º minuto e 10,84% (p<0,05) no 5º minuto, comparado à injeção isolada da dopamina. No Grupo III observou-se que, após a administração de propofol e dobutamina a dT/dt em (g.seg-1) sofreu acréscimo de 6,16% (p>0,05) no 1º minuto; 3,62% (p>0,05) no 3º minuto e 3,08% (p>0,05) no 5º minuto, comparado à injeção isolada da dobutamina. CONCLUSÃO: O propofol (25 mcg/ml) não alterou a resposta contrátil do miocárdio à dobutamina (50 mcg/ml); no entanto, inibiu a resposta esperada pela ação da dopamina (50 mcg/ml) na contratilidade miocárdica.ABSTRACT
PURPOSE: Experimental investigation of the pharmacodynamic effects of propofol with and without simultaneous injections of dopamine or dobutamine in isolated hearts of rats. METHODS: In all animals under anaesthesia the hearts were removed and irrigated by a Krebs-Hensleit solution containing O2 (95%) and CO2 (5%), under constant pressure of 90 cm H2O and at 37ºC. After stabilization of the heart activity during 15 minutes, the control values were obtained. The following groups were considered: Group I (control) - 10 hearts perfused only with the Krebs-Hensleit solution during 11 minutes after the control values registration. Group II (dopamine-propofol-dopamine) -10 hearts with the following sequency of drug injections and results values registration: dopamine (50 mcg/ml), 1.3 and 5 minutes registration; propofol (25 mcg/ml), 1 minute period registration; dopamine again in the same dosis, 1.3 and 5 minutes values registration. Group III (dobutamine-propofol-dobutamine) -10 hearts with the following sequency of drug injections and results values registration: dobutamine (50 mcg/ml), 1.3 and 5 minutes registration: propofol (25 mcg/ml), 1 minute period registration; dobutamine again in the same dose and 1.3 and 5 minutes of registration. RESULTS: In Group I hearts, the dT/dt mean values changed only from 39.57 ± 3.97 to 39.37 ± 3.44 g.seg-1 (p>0.05). In Group II after propofol and dopamine the dT/dt fell 17.61 % (p<0.05) in the 1 min; 8.37% (p<0.05) in the 3 rd min and 10.84% (p<0.05) in 5 th min, when compared with the results from isolated dopamine injections. In Group III the dT/dt increased 6.16% (p>0.050) in the 1 st min; 3.62% (p<0.05) in 3 rd min and 3.08% (p>0.05) in the 5 th min, over the values from isolated dobutamine injections. CONCLUSIONS: The myocardial contractile response to dopamine (50 mcg-ml-1) was partially inhibited; by propofol (25 mcg/ml-1) action was not altered.REFERÊNCIAS
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