Borges Marisa Miziara Jreige, Saraiva Renato Angelo
Departamento de Anestesiologia da Rede SARAH de Hospitais, Brasilia, DF.
Rev Bras Anestesiol. 2002 Apr;52(2):146-55. doi: 10.1590/s0034-70942002000200002.
In a theoretical study, Mapleson using a multicompartmental pharmacokinetic model in a standard 40-year old and 70 kg man, has shown that with a fresh gas flow (FGF) initially equal to total pulmonary minute ventilation and then decreased to 1 L min(-1), and with fractional anesthetic administration (F(adm)) set to 3 MAC, the end fractional expired also expressed as alveolar (F(E')=F(A)) may reach 1 MAC in few minutes, according to the solubility of the inhaled agent. The purpose of this study was to clinically apply.
Twenty-eight patients of both genders, aged 18 to 55 years, scheduled to undergo general anesthesia, were randomly divided in four groups of seven patients each according to the anesthetic drug to be used (halothane, isoflurane, sevoflurane and desflurane). Anesthesia was induced with intravenous propofol, fentanyl and vecuronium, and maintained with the inhalational agent diluted in oxygen under mechanical ventilation. Gas parameters were set, according to the agent as follows: Halothane group: initial FGF of 5 L min(-1) up to the 4th minute, followed by 2.5 L min(-1) up to the 10th minute and 1.5 L min(-1) up to the 20th minute; F(adm) was 3 MAC during the first 20 minutes of anesthesia. Isoflurane group: initial FGF of 5 L min(-1) for 1.5 minute, followed by 1.5 L min(-1) up to the 7th minute and 1 L min(-1) up to the 20th minute. F(adm) was 3 MAC up to the 7th minute and 2.5 MAC up to the 20th minute. Sevoflurane group: initial FGF of 5 L min(-1) for 1 minute and 1 L min(-1) up to the 20th minute. F(adm) was 3 MAC for 1 minute, 2.5 MAC up to 7 minutes and 1.8 MAC up to the 20th minute. Desflurane group: initial FGF of 3.5 L min(-1) for 1 minute and 1 L min(-1) up to the 20th minute. F(adm) was 3 MAC for 1 minute followed by 1.5 MAC up to the 10th minute and 1.2 MAC up to the 20th minute. In addition to routine monitoring of physiological (cardiovascular and respiratory) variables, FI and FE (FA) of the inhaled agents were measured.
Halothane group: FA reached 1.15 MAC in 2 minutes and varied from 1.21 to 1.47 MAC until the 20th minute. Isoflurane group: FA reached 1.03 MAC in 1 minute and varied from 1.11 to 1.21 MAC until the 20th minute. Sevoflurane group: FA reached 1.53 MAC in 1 minute and varied from 1.10 to 1.34 MAC until the 20th minute. Desflurane group: FA reached 0.94 MAC in 1 minute and varied from 1.07 to 1.14 MAC until the 20th minute.
Results obtained confirm the clinical feasibility of Maplesons theoretical model. This way, a fast FA increase of the inhaled agent was achieved, which reached 1 MAC in 1 to 2 minutes and was maintained within this value with minor variations and low anesthetic consumption.
在一项理论研究中，梅普勒索恩使用多室药代动力学模型，以一名40岁、体重70千克的标准男性为对象，结果显示，初始新鲜气体流量（FGF）等于总肺分钟通气量，随后降至1升/分钟，吸入麻醉药浓度（F(adm)）设定为3倍最低肺泡有效浓度（MAC），根据吸入麻醉药的溶解度，呼气末分数（也表示为肺泡分数，F(E')=F(A)）在几分钟内可能达到1倍MAC。本研究的目的是进行临床应用。
28例年龄在18至55岁、计划接受全身麻醉的患者，根据所用麻醉药（氟烷、异氟烷、七氟烷和地氟烷）随机分为四组，每组7例。静脉注射丙泊酚、芬太尼和维库溴铵诱导麻醉，并在机械通气下用稀释于氧气中的吸入麻醉药维持麻醉。根据麻醉药设置气体参数如下：氟烷组：初始FGF为5升/分钟，持续至第4分钟，随后2.5升/分钟，持续至第10分钟，1.5升/分钟，持续至第20分钟；麻醉前20分钟F(adm)为3倍MAC。异氟烷组：初始FGF为5升/分钟，持续1.5分钟，随后1.5升/分钟，持续至第7分钟，1升/分钟，持续至第20分钟。至第7分钟F(adm)为3倍MAC，至第20分钟为2.5倍MAC。七氟烷组：初始FGF为5升/分钟，持续1分钟，随后1升/分钟，持续至第20分钟。F(adm)在1分钟时为3倍MAC，至7分钟为2.5倍MAC，至第20分钟为1.8倍MAC。地氟烷组：初始FGF为3.5升/分钟，持续1分钟，随后1升/分钟，持续至第20分钟。F(adm)在1分钟时为3倍MAC，随后至第10分钟为1.5倍MAC，至第20分钟为1.2倍MAC。除常规监测生理（心血管和呼吸）变量外，还测量了吸入麻醉药的吸入浓度（FI）和呼气末浓度（FE(FA)）。
氟烷组：FA在2分钟内达到1.15倍MAC，至第20分钟时在1.21至1.47倍MAC之间变化。异氟烷组：FA在1分钟内达到1.03倍MAC，至第20分钟时在1.11至1.21倍MAC之间变化。七氟烷组：FA在1分钟内达到1.53倍MAC，至第20分钟时在1.10至1.34倍MAC之间变化。地氟烷组：FA在1分钟内达到0.94倍MAC，至第20分钟时在1.07至1.14倍MAC之间变化。
所得结果证实了梅普勒索恩理论模型的临床可行性。通过这种方式，实现了吸入麻醉药FA的快速增加，在1至2分钟内达到1倍MAC，并在该值内保持微小变化且麻醉药消耗量较低。
