Neurological Manifestations of Hypoglycaemia

cases of this kind. This substance is dangerous if given too quickly or in too large amounts intravenously. If it must be given, electrocardiographic control of its effects is essential if tragedies are to be avoided. The accounts of cases of carbon dioxide narcosis have interested me greatly. While the article was in preparation I received as reports of neostigmine-resistant curarization accounts of four seemingly similar cases. These, however, had occurred in patients who were undoubtedly suffering from severe emphysema before anaesthesia was induced, and for this reason they were excluded. The differential diagnosis of the two conditions is, however, difficult and depends on the demonstration of myoneural block by an inadequate response to stimulating the motor point of a forearm muscle. In this connexion the progressive failure of the response to repeated stimuli or the inability to sustain a tetanus, so much more characteristic of competitive block, is more likely to be found than complete myoneural inexcitability. Indirect evidence of respiratory dysfunction shown by upsets of blood carbon-dioxide combining power and alterations of blood pH is also of value, but the loss of base associated with ileus in cases of this kind makes such results difficult to interpret. The essential practical point is that carbon dioxide narcosis is a rereversible and recoverable condition which responds to hyperventilation through soda lime, combined, perhaps, with the intravenous administration of sodium lactate. Two explanations offered by your correspondents of the syndrome have little evidence to support them. First, the assumption that trouble arose because a depolarizing drug was used to intubate and a compvtitive blocker during the operation itself is a misconception which was almost bound to arise from the enormous amount of conflicting experimental work in this field. There is no doubt that under certain circumstances depolarizing blockers antagonize, and under other circumstances their action sums with that of competitive blockers, but, except in the unusual circumstances described by Foldes and Hodges,' there is nothing mysterious in the response of experimental animals to two consecutive doses of relaxants of different types; at worst the effect is a simple summation both of intensity and duration of action. The idea that neostigmine can itself act in man as a myoneural blocking agent has also very little experimental evidence 10 support it. This action of the drug cannot be serious in view of Dr. M. F. McGrath's report (Journal, November 10, 1956, p. 1114) of giving 25 mg. of neostigmine in two hours without illeffect. Finally, it is to be emphasized that the problem of neostigmine-resistant curarization is by no means solved. If it is to be elucidated, the following investigations should be carried out in every case before blood transfusion or any other remedial measures are employed. First, myoneural block must be demonstrated by stimulating the motor point of a muscle. Secondly, sufficient blood must be removed to allow the estimation of the serum potassium, sodium, chloride, and carbon-dioxide combining power, together with the pH of the arterial or arterialized venous blood (this last may be rather difficult to obtain, but without it estimations of blood carbon-dioxide combin-ing power on their own are meaningless. For therapy, vigorous overventilation by hand for a period, and perhaps subsequently with an apparatus capable of producing negative pressure phase, should be employed. Sodium lactate may be given intravenously also. Adequate support to the failing circulation in the form of blood transfusion, digoxin intravenously, and vasopressors is also required. It is obviously desirable to avoid producing the state of neostigmine-resistant curarization altogether. Many techniques of anaesthesia which ensure that antidotes to relaxant drugs are not required have been described from time to time in the literature. It would be well in a dilapidated elderly patient with ileus to consider whether these means offer advantages over the use of D-tubocurarine right to the point of abdominal closure and thereafter administering neostigmine. It is also important to underline in this connexion the dangers of routine dosage of drugs, and especially of relaxants. Above all, an adequate interval of up to five minutes must be allowed for the development of relaxation after the injection of a myoneural blocking agent in a patient already suffering from circulatory depression. -I am, etc., Manchester. A. R. HUNTER.