ARTIGO ORIGINAL

Emprego de uma nova emulsão de perfluorocarbonos (Oxygent MR) em circulação extracorpórea: estudo experimental em cães

Walter V. A Vicente^I; William L. HOLMAN^II; Russell D. SPRUELL^II; Edward R. FERGUSON^II; Janice J. Clymer^III; C. Patrie Murrah^II; Albert D. PACIFICO^II

DOI: 10.1590/S0102-76381995000100005

RESUMO

Testou-se uma nova emulsão de perfluorocarbonos (Oxygent^MR, Alliance Pharmaceutical, San Diego, CA 92121, EUA) em circulação extracorpórea (CEC) com hipotermia de 32ºC e hematócrito de 12%. Estudaram-se 42 cães, 12 dos quais não receberam a droga e serviram de controle (Grupo 1), enquanto os demais constituíram 3 grupos de 10 animais cada, tratados com doses de Oxygent de 1,5 ml/kg (Grupo 2), 3 ml/kg (Grupo 3) e 6 ml/kg (Grupo 4) as quais geraram fluorocritos de, respectivamente, 1 %, 2% e 3%. Foram analisadas variáveis do metabolismo do oxigênio (O₂) em 6 diferentes fluxos de perfusão (Q), ordenados ao acaso. Reaqueceram-se os cães, interrompeu-se a CEC e acompanharam-se os animais por 1 hora. Diferenças intergrupos foram analisadas pelo teste das médias dos quadrados mínimos e pelo teste de Duncan, considerando-se significantes os valores de p< 0,05. Embora algo maiores no Grupo 4, a pressão parcial bem como o conteúdo arterial de oxigênio (C_aO₂) foram estatisticamente semelhantes ao grupo controle. A pressão parcial de O₂ no sangue venoso misto (P_vO₂) do Grupo 4, em função do Q, mostrou-se significativamente maior (p < 0,03) que a do grupo controle, conquanto isto não tenha se repetido ao ser analisada em função da oferta tecidual de O₂ . Também não houve diferença quanto ao consumo de O₂ total e dissolvido, nem quanto aos gradientes sistêmico e miocárdico de lactato, porém a maior dose da emulsão (Grupo 4) expressa efeito dose-dependente benéfico, ainda que de natureza especulativa, do Oxygent sobre o metabolismo do oxigênio.

ABSTRACT

A novel perfluorocarbon emulsion (Oxygent^TM - Alliance Pharmaceutical Corp., San Diego, CA 92121, USA) was tested during hypothermic (32ºC) cardio pulmonary bypass (CPB) under severe hemodilution (Hto = 12%). Forty-two mongrel dogs were allocated to 4 groups. Group 1 (n=12) was not given Oxygent and served as control whereas Groups 2, 3, and 4 (10 animals each) were given a bolus dose of the emulsion (1.5,3.0, and 6.0 ml/kg, respectively) at the onset of CPB. O₂ metabolism variables were then studied at 6 randomized pump flow rates (Q) ranging from 0.25 to 3.0 l/min/m². After rewarming CPB was discontinued and the animals were followed-up for one hour and then killed by IV KGI injection. Differences between groups were evaluated by the least squares means and Duncan's tests and considered significant for p<0.05. Fluorocrit values remained stable on CPB Group 2 -1 %, Group 3 - 2%, and Group 4 - 3%). Although somewhat elevated, Group 4 arterial blood O₂ partial pressure and content (C_aO₂) didn't reach statistical significance versus control. Group 4 mixed venous blood O₂ partial pressure (PvO₂) regressed against Q was significantly higher (p < 0.03) than control, but there was no statistical difference when this variable was regressed against O₂ delivery rate. Groups were similar regarding total as well as dissolved O₂ consumption and systemic and transmyocardial lactate gradients. A trend towards lower mortality rates was noticed in Groups 3 (20%) and 4 (10%) versus control (41.6%). Group 4 trend towards both reduced mortality and higher C_aO₂ as well as its significant PvO₂ rise against Q suggest a beneficial, yet speculative, Oxygent dose dependent effect on O₂ metabolism.

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AGRADECIMENTOS: Aos Srs. Ronnie Brown, Jefferson Dudleston e Fred Wallace, pela inestimável assistência técnica. À Sras. Laucéa Conrado S. Porciúncula e Marlene Lúcio, pela edição do texto. Ao CNPq, pela bolsa de estudos.

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