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ORIGINAL ARTICLE

Use of a new perfluorocarbon emulsion (OxygentTM) in a profoundly anemic canine model of hypothermic cardiopulmonary bypass

Walter V. A VicenteI; William L. HOLMANII; Russell D. SPRUELLII; Edward R. FERGUSONII; Janice J. ClymerIII; C. Patrie MurrahII; Albert D. PACIFICOII

DOI: 10.1590/S0102-76381995000100005

ABSTRACT

A novel perfluorocarbon emulsion (OxygentTM - 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 (CaO2) 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 CaO2 as well as its significant PvO2 rise against Q suggest a beneficial, yet speculative, Oxygent dose dependent effect on O2 metabolism.

RESUMO

Testou-se uma nova emulsão de perfluorocarbonos (OxygentMR, 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 (CaO2) foram estatisticamente semelhantes ao grupo controle. A pressão parcial de O2 no sangue venoso misto (PvO2) 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.
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