一酸化炭素 (CO)中毒 (Carbon Monoxide Poisoning)

Carbon Monoxide Poisoning

Sometimes people attempt suicide using carbon monoxide and it's sometimes a theme in who-done-it TV dramas.

Carbon monoxide is a colorless tasteless gas that binds to hemoglobin with 240 times the affinity of oxygen, so even if oxygen is available the hemoglobin will choose to link with the carbon monoxide. It effectively reduces the oxygen content in the blood.(1)

A pulse oximeter will not give accurate reading in the case of carbon monoxide poisoning because the wavelengths it emits for measurement cannot identify the carbon monoxide bound to hemoglobin (COHb). Unlike a co-oximeter, it will give inaccurate high readings of SaO2 in CO poisoning. It does not affect PaO2. It inhibits cytochrome oxidase in the Electron Transport Chain (ETC). (2)

Findings include the familiar cherry red skin color shown in TV dramas, a headache at levels from 10-20%, dyspnea and dizziness at 20-30%, seizures and coma at 50-60%. There is also the lactic acidosis associated with hypoxia.(2) The hypoxia also causes the widespread ischemic changes in the CNS, especially in the basal ganglia and lenticular nuclei. (3)

Treatment is with 100% oxygen for 6 hours.(4)

References

(1) Davis, Jessica; King, Emily. Deja Review Pathology, Second Edition . McGraw-Hill Education. Kindle Edition.

(2) Goljan, Edward F.. Rapid Review Pathology Revised Reprint (Kindle Location 174, 356). Elsevier Health. Kindle Edition.

(3) Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon. Robbins & Cotran Pathologic Basis of Disease, (Robbins Pathology) (Kindle Location 20889). Elsevier Health. Kindle Edition.

(4) Roberts, James R.; Hedges, Jerris R.. Roberts and Hedges’ Clinical Procedures in Emergency Medicine E-Book (Roberts, Clinical Procedures in Emergency Medicine) (Kindle Location 39158). Elsevier Health Sciences. Kindle Edition.

一酸化炭素 (CO)中毒

COは練炭自殺などのテレビドラマのテーマでよく知られている。

一酸化炭素 (CO)は無色で無臭であるガス。酸素よりもヘモグロビンに240倍親和結合をするので酸素(O₂)が存在してもヘモグロビンはCOを選ぶ。従って、血中の酸素濃度を減らす。(1)

一酸化炭素中毒の際、パルスオキシメーターが正確な数値を出せない。なぜならば、測定に放射される波長がCOHb (ヘモグロビンに親和結合した一酸化炭素）を識別できないからだ。一酸化炭素中毒の場合には不正確な高いSaO2が表示される。他方では一酸化炭素中毒はPaO2数値には影響しない。

一酸化炭素中毒は電子伝達鎖(ETC)内のトクロムオキシダーゼを抑制する。(2)

所見には刑事ドラマでよく強調される赤い皮膚色、更に10%-20%のレベルでは頭痛、20%-30%では呼吸困難や眩暈、50%-60%では発作や昏睡がある。低酸素症に伴う乳酸アシドーシスもある。(2)低酸素症によって中枢神経系の虚血性変化も起こる、特に基底核とレンズ核が影響される。(3)

治療は6時間の100%酸素投与。(4)

参考

(1) Davis, Jessica; King, Emily. Deja Review Pathology, Second Edition . McGraw-Hill Education. Kindle Edition.

(2) Goljan, Edward F.. Rapid Review Pathology Revised Reprint (Kindle Location 174, 356). Elsevier Health. Kindle Edition.

(3) Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon. Robbins & Cotran Pathologic Basis of Disease, (Robbins Pathology) (Kindle Location 20889). Elsevier Health. Kindle Edition.

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