頭部外傷急性期のMetabolic Acidosis

METABOLIC ACIDOSIS IN ACUTE HEAD INJURY

I．緒言

　重症頭部外傷でmetabolic acidosisがおこることはすでに報告があり，Rowbotham^12）もその著書の中に，必須の検査項目として血液のHCO₃^—をあげている。Gordon^8）らは亜急性期にazotemic acidosisをみた2例について，Fisher^6）らも同じくazotemic acidosisをきたした脳幹部損傷の1例について報告した。Cook^4）らは急性期の重症頭部外傷18例の酸塩基平衡を検討し，respira—tory acidosis, respiratory alkalcsis, mixed acidcsisを示したものは全例死亡したと報告した。私達^16）も同様な症例16例について検討し，respiratory acidosisはほとんどみられないこと，respiratory alkalosisであつても救命しうること，metabolic acidosisをきたした症例の予後は不良であることを報告し，Cookらの報告との違いを指摘した。metabolic acidosisはcardiac arrest, shock，重症一般外傷におこる異常であり^9），頭部外傷急性期にくるものが，なんらかの特異性をもつかということについて検討したので報告する。

It has been reported that many of severe head injury had various types of alteration of acid-base balance in the acute phase and metabolic acidosis was the most common disorder in those who suc-cumbed or were in the prolonged unconscious state.

Twenty two patients who rendered comatose state over 24 hours following the head injury or the lucid interval after initial loss of consciousness, were stu-died of extraneous causes of the metabolic acidosis. Metabolic acidosis was defined as the occurrence of pH below 7.35 with base excess below -2.3 mEq/L and normal PCO₂, in patients without previous disease or associated injury of other organs.

Ten patients of whom 2 survived, revealed either one or more of low PO₂, temporal decrease of systolic blood pressure below 60 mmHg, shock and cardiac arrest before developement of the metabolic acidosis.

Six patients who all died, had acute and severe metabolic acidosis and the cause was considered to be the brain stem legion or acute intracranial hy-pertension. For example, a year old child who had fallen from 10 meter and had been restless without cyanosis, was in marked metabolic acidosis 1 hour after the injury.

In the remaining six patients, the extraneous cau-ses were left unknown clinically. The acidosis pro-gressed slowly and completed in about 24 hours after the head injury. They reacted well on the administration of NaHCO₃ or THAM. Some of them took immediate recovery to the normal level of pH and base excess, and remained in that state over 12 hours after the single administration of NaHCO₃. Three of them survived.

It was emphasized that the deliberation should be necessary on the use of hypothermia and the applica-tion of mechanical respirator in the treatment of head injury for they may induce metabolic acidosis.