Lerou J G C
Radboud University Nijmegen, Department of Anaesthesia, Geert Grooteplein 10, 6500 HB Nijmegen, The Netherlands.
Br J Anaesth. 2004 Aug;93(2):288-91. doi: 10.1093/bja/aeh186. Epub 2004 Jun 25.
In clinical practice it is difficult to estimate rapidly two important values: (i) the total age-corrected MAC multiple from measured end-expired concentrations of volatile agent and nitrous oxide; (ii) the end-expired concentration of volatile agent needed to obtain a given total MAC multiple. We have developed a nomogram to do this.
We used standard nomogram methods to construct one single nomogram covering wide ranges of age (1-100 yr) and MAC (0.1-1.8 MAC) for halothane, enflurane, isoflurane, sevoflurane, and desflurane, alone or in combination with various concentrations of nitrous oxide. The user only has to draw two straight lines to obtain the desired result.
The nomogram is simple to use. End-expired concentrations of halothane 0.48%, enflurane 1.05%, isoflurane 0.75%, sevoflurane 1.18%, or desflurane 4.3% in the presence of nitrous oxide 50% will give 1.4 MAC in a patient of 75 yr vs 0.9 MAC in a 1-yr-old. A reverse example is: a total MAC of 1.3 when using sevoflurane and nitrous oxide 67% in oxygen, requires an end-expired sevoflurane concentration of 1.8% in a 3-yr-old whereas 0.55% is needed in a patient of 90 yr.
The nomogram gives accurate results if it covers a whole A4 sheet in landscape format and could be extended to apply to other agents, for example xenon.
在临床实践中，很难快速估算两个重要数值：（i）根据测得的挥发性麻醉剂和氧化亚氮的呼气末浓度计算出的年龄校正后总MAC倍数；（ii）获得给定总MAC倍数所需的挥发性麻醉剂呼气末浓度。我们开发了一种列线图来进行此项估算。
我们采用标准列线图方法构建了一张单一列线图，涵盖了广泛的年龄范围（1至100岁）和MAC范围（0.1至1.8 MAC），适用于氟烷、恩氟烷、异氟烷、七氟烷和地氟烷，单独使用或与不同浓度的氧化亚氮联合使用。使用者只需画两条直线即可获得所需结果。
该列线图使用简便。在50%氧化亚氮存在的情况下，75岁患者呼气末氟烷浓度为0.48%、恩氟烷浓度为1.05%、异氟烷浓度为0.75%、七氟烷浓度为1.18%或地氟烷浓度为4.3%时，将产生1.4 MAC，而1岁患者则为0.9 MAC。反之，例如：在3岁患者中，当使用七氟烷和67%氧化亚氮（氧气中）时，要达到总MAC为1.3，则呼气末七氟烷浓度需为1.8%，而90岁患者则需要0.55%。
如果该列线图以横向格式覆盖一整张A4纸，就能给出准确结果，并且可以扩展应用于其他麻醉剂，例如氙气。
