Hörnchen U, Tauberger G
Anaesthesist. 1980 Oct;29(10):547-51.
The effects of ketamine 5 mg/kg on blood pressure, heart-rate and the efferent action-potentials of the sympathetic and phrenic nerves were investigated in 17 relaxed and artificially ventilated cats. In part of the experiments (8 cats) ketamine was given as the sole narcotic agent, in the rest ketamine was applied a light basic as anaesthesia with N2O/O2 in relation of 2:1. The findings were, that ketamine given as monoanaesthetic agent increase blood pressure and heart-rate, as well as efferent sympathetic activity. The registration of the phrenic nerve activity showed a prolongation of the inspiratory periods, but no change of the general activity. In contrast, ketamine combined with nitrous-oxide resulted in a reduction of blood pressure and in a clear depression of the activity of both the sympathetic and phrenic nerves. These results may lead to the conclusion, that the blood pressure increasing effect of ketamine is, at least to a large extent, due to a suppression of inhibitory neurons in central-nervous sympathetic areas, whereas the increase of the heart-rate may be caused by a depression of parasympathetic centres. The characteristic changes of the inspiratory activity of the respiration centre may be due to a disinhibition of inspiratory neurons. Because these results were obtained after application of anaesthetically effective doses, these experiments lead to the conclusion, that after application of ketamine, effects were registered in the stage of tolerance, which with other anaesthetics only appear in the stage of excitation.
在17只处于放松状态并进行人工通气的猫身上，研究了5毫克/千克氯胺酮对血压、心率以及交感神经和膈神经传出动作电位的影响。在部分实验中（8只猫），氯胺酮作为唯一的麻醉剂使用；在其余实验中，氯胺酮与比例为2:1的N2O/O2联合使用作为轻度基础麻醉。研究结果表明，单独使用氯胺酮作为麻醉剂会使血压、心率以及交感神经传出活动增加。膈神经活动记录显示吸气期延长，但总体活动无变化。相比之下，氯胺酮与一氧化二氮联合使用会导致血压降低，同时交感神经和膈神经的活动明显受到抑制。这些结果可能得出如下结论：氯胺酮的升压作用至少在很大程度上是由于中枢神经交感区域抑制性神经元受到抑制，而心率增加可能是由副交感神经中枢受到抑制所致。呼吸中枢吸气活动的特征性变化可能是由于吸气神经元的去抑制作用。由于这些结果是在使用麻醉有效剂量后获得的，这些实验得出结论：使用氯胺酮后，在耐受阶段就出现了其他麻醉剂仅在兴奋阶段才会出现的效应。
