Influence of hemorrhagic shock on the pharmacokinetics and pharmacodynamics of intravenous anesthetics

持续输注时的瑞芬太尼浓度比联合应用异丙酚时的血药浓度升高3倍。瑞芬太尼持续输注时的血药浓度受心输出量的影响，易受麻醉深度和/或正性肌力药的影响。心输出量对瑞芬太尼浓度的影响程度与联合应用异丙酚的程度相似，而这两种药物在失血性休克时的反应相反。心输出量减少对两种药物浓度的影响大于心输出量增加。这些结果表明，在低心输出量状态下，实际血药浓度可能显著偏离预期血药浓度。

The remifentanil concentration during continuous infusion undergoes an increase that is three times higher than that for co-administered propofol with progression of haemorrhage. This result indicates that the remifentanil dose should be reduced substantially compared with propofol for patients with significant blood loss.The remifentanil concentration during continuous infusion is affected by cardiac output, which changes easily in response to anaesthetic depth and/or administration of inotropic agents. The extent of the influence of cardiac output on the remifentanil concentration is similar to that on coadministered propofol, in contrast to the responses of these two drugs during haemorrhagic shock. The influence of decreased cardiac output on both drug concentrations is greater than that of increased cardiac output. These results indicate that the actual blood concentrations might substantially deviate from the expected concentrations in a low cardiac output state.