〒190-0004 東京都立川市柏町3丁目1-1

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麻酔によって起こるメトヘモグロビン血症の対策 – 英語論文の要約

  1. Benzocaine should no longer be used. Although it is well tolerated by the majority of individuals, some patients will develop methemoglobinemia upon exposure. It is not possible to predict who will be at risk. In susceptible individuals, there is no “therapeutic window” between the doses required to produce a therapeutic effect and those producing toxicity. Sensitive individuals may develop methemoglobinemia after a single benzocaine sprayベンゾカインは使用しないこと。大多数は十分な耐性を持つが、ベンゾカインへの曝露によってまれにメトヘモグロビン血症を発症する患者がある。リスク患者の予測は不可能である。影響を受けやすい患者の場合、治療効果の生成に要する用量と毒性を生成する用量の間に「治療濃度域」はない。敏感な患者であれば、1回のベンゾカインスプレーでメトヘモグロビン血症を発症する可能性がある。
  1. Prilocaine should not be used in infants of less than 6-months-of-age (except for transcutaneous anesthesia), in pregnant women, patients receiving other oxidizing drugs and patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency

    プリロカインは、生後6ヶ月未満の乳児(経皮麻酔を除く)、妊婦、他の酸化薬(oxidizing drug)を服用中の患者、グルコース6リン酸脱水素酵素(G6PD)欠乏症の患者には使用しないこと。

  • When prilocaine is used for transcutaneous anesthesia, strict adherence to the manufacturer’s recommendations (amount, surface and length of exposition) is mandatory and it should not be administered at the same time by any other route
  • When prilocaine is administered for peripheral nerve blocks or IV regional anesthesia, limiting the dose to 2.5 mg/kg should probably decrease the risk of inducing clinically symptomatic methemoglobinemia but may not abolish it entirely
    末梢神経ブロックやIV局所麻酔にプロリカインを使用する場合、用量を2.5 mg/kgに制限することで症候性メトヘモグロビン血症の発生リスクをおそらく低減できると考えられるが、完全には排除できない。
  1. Lidocaine has induced methemoglobinemia in patients receiving other oxidizing drugs (nitrate therapy, trimethoprim- sulfamethoxazole, dapsone, phenazopyridine, phenacetin), from chronic abuse, at high doses in young children (<18 mo) and also possibly rarely at clinical use without any obvious predisposing factor. Whenever feasible, lidocaine should probably be replaced by another local anesthetic in patients taking other oxidative drugs and in patients with congenital methemoglobinemia


  1. Chocolate-colored blood is suggestive of methemoglobinemia but its absence does not exclude methemoglobinemia. There are many variations in the reported color blood with high concentrations of methemoglobinemia


  1. A discrepancy between the pulse oximeter saturation and the measured Pao2 (Sao2 􏰀90% with Pao2 􏰁70 mm Hg) after exposure to a hemoglobin oxidizing drug is strongly suggestive of methemoglobinemia. Other possible causes of a discrepancy between oximeter-measured oxygen saturation and measured Pao2 include carboxihemoglobinemia, sulfhemoglobinemia, and congenital or acquired diseases with abnormal O2-Hb dissociation curve, or congenital methemoglobinemia

    ヘモグロビン酸化薬に曝露後のPaO2測定値とパルスオキシメータの飽和度との食い違い(PaO2>70mm HgでSaO2<90%)は、メトヘモグロビン血症を強く示唆するものである。オキシメータで測定した酸素飽和度とPaO2測定値の食い違いの原因として他に考えられるものには、カルボキシヘモグロビン血症、スルフヘモグロビン血症、酸素・ヘモグロビン解離曲線の異常を伴う先天性疾患や後天性疾患、先天性メトヘモグロビン血症がある。

  1. The definitive diagnosis of methemoglobinemia is direct methemoglobin measurement by co-oximetry (normal < 1%–2.2%)


  1. The treatment is both symptomatic (optimization of oxygen delivery to tissues including oxygen administration as well as respiratory and hemodynamic support as required) and specific (methylene blue and/or ascorbic acid)


  1. Methylene blue (which acts faster than ascorbic acid) should be administered to symptomatic individuals with local anesthetic-induced methemoglobinemia except in those with G-6PD deficiency, where it will be ineffective (low level of NADPH) and it may possibly induce hemolysis. It should be used with caution in patients with severe renal impairment and in pregnant or breast-feeding women

    局所麻酔薬誘発性メトヘモグロビン血症の症状のある患者にはメチレンブルー(アスコルビン酸よりも作用が速い)を投与すべきである。 ただし、G6PD欠乏症患者は除く。G6PD欠乏症患者に対しては効果がなく(NADPHレベルが低い)、しかも、溶血を誘発する可能性がある。重篤な腎機能障害のある患者や妊娠中あるいは授乳中の女性患者の場合は使用に注意が必要である。

  • For newborns (up to 2 mo old), the first dose should be limited to 0.5 mg/kg IV. This dose may be as effective as the 1.0 mg/kg dose which has sometimes induced hemolysis in this subpopulation
    新生児(生後2ヶ月まで)には、初回投与量を0.5 mg/kg IV に制限すべきである。この用量は、この亜集団で溶血誘発例のある1.0 mg/kgと同程度の有効性があると考えられる。
  • For older patients, the first dose may be 1.0–2.0 mg/kg IV (concentration<1%) administered over 5 min (preferentially diluted in 5% dextrose)
    高齢患者の場合、初回投与量は1.0–2.0 mg/kg IV(濃度<1%)とし、5分以上で投与する(優先的に5%デキストロースで希釈する)。
  • The same dose may be repeated every 60 min as required up to a total dose of 7 mg/kg
    必要な場合には、同じ用量を、60分ごとに、最大で計7 mg/kgまで反復可能である。
  • A transient false decrease of the PSaO2 value may be observed after methylene blue administration
  1. For severe or refractory cases, red blood cells transfusion (anemic patients) or exchange transfusion has been reported to be effective重症例や難治例には、赤血球輸血(貧血患者)あるいは交換輸血が効果的と報告されている。
  1. Hyperbaric oxygen administration has not been demonstrated to be effective


  1. For patients who have developed methemoglobinemia after benzocaine administration on a mucous membrane, the methemoglobin concentration should be monitored for at least 24 h after methylene blue administration to prevent rebound methemoglobinemia


  1. Investigation to detect ischemic damage, including myocardial injury, may be warranted in susceptible individuals and/or severe cases


  1. Hemolysis may happen with or without the administration of methylene blue. Hemolysis should be aggressively treated if it occurs.









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