Dauthier C, Gaudy J H, Ferracci F, Bonnet P
Can Anaesth Soc J. 1981 May;28(3):248-52. doi: 10.1007/BF03005509.
A few effects of carbon dioxide on pain threshold and acid-base balance are known. The purpose of this study was to investigate specifically the variations of analgesia in relation to hypercapnia during general anaesthesia and the respective roles played by carbon dioxide and [H+]. The nociceptive jaw opening reflex was studied on five beagle dogs anaesthetized with alfathesin administered at constant rate under acute hypercapnic conditions and acute metabolic acidosis. Acute hypercapnia did not decrease the jaw opening reflex significantly until a level was reached where PaCO2 values modified blood [H+] (pH) significantly (10 +/- 1.04 kPa corresponding to [H+] 91.5 +/- 13.24 nmol/l (pH 7.04 +/- 0.06) p less than 0.05)). At [H+] 176.2 +/- 42.77 nmol/l (pH 6.7 +/- 0.13) (p less than 0.01) the reflex was only 9.3 +/- 3.9 per cent (p less than 0.001) of its initial value. The infusion of decinormal solution of HCl during constant capnia caused an abrupt drop of the reflex. There was a correlation between reflex and metabolic acidosis (p less than 0.05). The authors conclude that modification of the jaw opening reflex occurs with extreme values of arterial [H+] incompatible with safe anaesthesia and they discuss the mechanisms involved.
二氧化碳对痛阈和酸碱平衡的一些影响已为人所知。本研究的目的是具体调查全身麻醉期间与高碳酸血症相关的镇痛变化，以及二氧化碳和[H⁺]各自所起的作用。在五只比格犬身上研究伤害性下颌张开反射，这些犬在急性高碳酸血症和急性代谢性酸中毒条件下，以恒定速率注射阿法沙辛进行麻醉。急性高碳酸血症在达到PaCO₂值显著改变血液[H⁺]（pH）的水平之前（10±1.04kPa，对应[H⁺]91.5±13.24nmol/L（pH7.04±0.06），p<0.05），并不会显著降低下颌张开反射。在[H⁺]176.2±42.77nmol/L（pH6.7±0.13）（p<0.01）时，反射仅为其初始值的9.3±3.9%（p<0.001）。在恒定二氧化碳分压期间输注十分之一当量的HCl溶液会导致反射突然下降。反射与代谢性酸中毒之间存在相关性（p<0.05）。作者得出结论，下颌张开反射的改变发生在与安全麻醉不相容的动脉[H⁺]极值时，并讨论了其中涉及的机制。
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