Animal experiments, with general cooling, give grounds for believing that the intermediary metabolism is disturbed during drops in temperature; but this change is also discussed in connection with local freezing of the human being and has been proved to a certain extent. Furthermore, not only this disturbance shows a transition between general and local damage by cold. In both cases there occurs an increase in viscosity, which points to a change in the capillary walls and indicates the conclusion that there is a change in the permeability of those walls for protein and water.
The heart-death remains prominent, the regular increase of spinal fluid pressure with severe cooling of the neck and back of the head leaves it unsettled whether, in addition, this has pathognomonic significance for the outcome. With a fluid pressure of 420 mm. it must in fact be assumed that this participates in the development of bradycardia.
The detection of an increase in fluid pressure is also not without significance for therapy. One may think of a lumbar or suboccipital puncture as a measure to be prescribed. After a lumbar puncture there occurs a transformation of the slow form of arrhythmia into the rapid form. It must remain undecided whether such measures, which delay a rapid, active rewarming, are to be recommended for practical application in the sea-rescue service.
The idea that cold-death in water depends upon failure of the heart, accompanied or unaccompanied by breathing, is subject to limitation. One experiment among fifty-seven was typical. This involved survival of a cooling to 25.2° C. [77.4° F.] during a stay of 3 hours in water of 5.5° C. [41.4° F.]. The rectal temperature under these conditions remained constant within slight variations between 27° and 25° C. [81° and 77° F.] for the last hour and a half. Likewise, quite irregularly, no increase in blood sugar occurred. But most striking was the fact that until the end of the experiment and after its termination consciousness was undisturbed. The course of the experiment reminded one of the behavior of certain experimental animals which can withstand extremely low body temperatures for long periods of time. Lower, warm-blooded animals (for example, rats) can endure rectal temperatures of 20° C. [68° F.] for several hours. It is conceivable that this atypical experiment, had it been continued, would have shown also an atypical cause of death. Against this we have the fact that an irregularity had already set in but not before a temperature of 30.1° C. [86.2° F.] had been reached.
Also, aside from the fluid pressure increase, the part which the central nervous system plays in the outcome of the experiment seems to us to be secondary. The experiments with simultaneous cooling of the neck of course showed how the cooling of the neck and back of the head speeds up the lowering of temperature. This is to be explained by the fact that the counter-controls which are relayed from the temperature center to the periphery, either cannot exist further because of hypofunction of the centers (effect of oedema and cooling), or are no longer transmitted because of cold-blocking of the pathways. But likewise central counter-controls for the areas of the peripheral capillaries may fall; thus delaying the overloading of the heart by extended periphera vasco friction.
VII. The Influence of Pharmacology and the Question of Alcohol
Now experiments by Jarisch have shown that heart drugs like strophanthin and stimulants like cardiazol and coramine in therapeutic doses may react toxically upon cooled animals. These findings are a warning to be most careful in the medicinal treatment of severely cooled persons, though strophanthin and cardiazol have heretofore been expressly recommended in such cases.
In experiments with fatal outcome, the stopping of the heart occurred either in the water or after an interval of not more than 14 minutes after removal from the water. With such a rapid course of events it is unlikely that one can favorably influence the heart action by intravenous injections of strophanthin, especially because the circulation is at a very low ebb before the heart-death. For this reason, in a case whose condition was already very dangerous, strophanthin was given intracardially in a dose of 0.25 mg. Thereupon the heart condition grew still worse and after 5 minutes the heart stopped. One had the impression that the heart action was made worse by the intracardial injection of strophanthin. This is, however, the only case which left the possibility of damage by strophanthin in doubt. No such damage could ever be established in the intravenous injection of strophanthin. On the other hand no therapeutic effect, even with maximal doses of 0.5 mg., could be detected. Figure 11 [not reproduced], last section, shows the total duration in 10 cases of the irregularity observed without strophanthin dosage. This varies between 25 and 200 minutes. On the other hand in Figure 13 in the last section, first five cross-rows there are corresponding time values of 175 to 360 minutes. At various experimental time points during these experiments 0.25 to 0.5 of strophanthin were given. Accordingly, a shortening of the duration of the irregularity cannot be established. Furthermore no improvement of the pulse or general condition was ever noted. Obviously these experiments are too few to rule out a possible favorable effect in all cases. Several hundred experiments would be necessary to obtain statistically reliable data on this point. And so, since contrary to animal experimentation, we could not unquestionably establish damage following intravenous strophanthin dosage, we may leave it to the treating physician whether or not he may still want to make an experiment with strophanthin. To be sure, such an employment of it must be advised against in case of a very much decelerated form of irregularity. This will be observed when there is the greatest danger; under such circumstances time should never be lost by experimenting with drugs, but every effort should be made in the direction of intensive heat therapy.
Also in the experiments with cardiazol, coramin and lobeline we restricted ourselves primarily to determining whether injurious effects occurred in the case of relatively large doses. Four cc. of 10 percent coramin as well as 2 cc. of 1 percent lobeline were injected intravenously at various stages of recovery without any marked objective and subjective deterioration of the state of the heart, the breathing, and the general condition. But just as with strophanthin, it is impossible to rule out a possible therapeutically favorable effect because of the small number of experiments. We never observed such an effect. Especially the marked deepening of breathing and of the irritability of the trigeminal nerve which usually sets in very suddenly after coramin (for example, sneezing immediately after the injection) were always missing. Contrary to strophanthin, in the case of which we cannot advise against experimentation by intravenous injection under certain conditions, we believe on theoretical grounds that such experiments with peripheral circulatory drugs which may heighten the vessel tonus are not indicated because of the following considerations: The damage to the heart is to be attributed, among other things, to an overloading, which is caused by a blocking of enlarged vessel areas, aside from an increase in viscosity. If the vessel tonus is further increased in the areas which have remained unimpeded, the conditions for the heart are thereby made worse.
The sceptical attitude toward the effect of drugs is strengthened above all by the observation that in the majority of the experiments in which no drugs were given, even the most severe disturbances of the peripheral circulation were reduced remarkably rapidly under intensive heat treatment. In this connection it must be emphasized that besides the recovery of body temperature through heat therapy an unloading of the heart takes place because the blocked areas open up. Contrary to earlier concepts, according to which there was danger of hemorrhage into the periphery during rapid rewarming, and according to which one sought to avoid this hemorrhage by wrapping up the extremities as well as by very slow warming, the “venalous bleeding into the periphery” may be life-saving under some circumstances. An exception, namely, loval pyperacmia after considerable rise in temperature and corresponding reestablishment of circulation has already been described in the reference to the danger in some cases of very prolonged treatment in the light cradle.