Relapse in pneumonia is a rare event; it is quite phenomenal for it to occur four days after the crisis. The temperature suddenly rises, but usually returns to normal in three or four days.
Pulse.—The pulse in pneumonia varies with the type and extent, as well as with the stage, of the disease. In an ordinary mild case the pulse-rate is usually between 90 and 120 per minute. When the pulse-rate for any length of time is above 120, the case must be regarded as an exceedingly grave one.
The pulse at the onset of croupous pneumonia is usually full and soft. As the disease progresses it becomes small and feeble. In severe cases, and when the nervous system is markedly implicated, it is rapid, and may be 130 to 140, or even 160, at the onset of the disease. In such cases it will also be small and feeble.
A high temperature is usually accompanied by a rapid pulse, and a low temperature by a moderately frequent, full pulse. At the day of crisis, when the temperature falls, the pulse will fall; and this occurs in the severe as well as in the mild cases.
Subsequent to the third or fourth day in severe cases the pulse, in addition to its frequency and feebleness, may exhibit dicrotism, or it may be jerky, very compressible, and intermittent. Sometimes just before death the pulse becomes markedly slow. The feebleness of the pulse is ascribed by some to cardiac depression, the result of the high temperature; by others it is claimed that the afflux of blood to the left ventricle obstructs, and causes a deficiency in, the aortic circulation. In other words, hepatization is adduced as a cause of the feeble pulse. In chronic wasting diseases, in feeble, weak individuals, or in those already suffering from cardiac disease, weakness of the pulse is a very marked symptom.
I cannot regard a feeble pulse in pneumonia as due to the pulmonary hepatization, for it is not that pneumonia which is most extensive that is accompanied by the greatest heart-flagging. Heart-failure may exist before, or just as, consolidation is beginning. In many pulmonary affections the obstruction to the pulmonary circulation is greater than in pneumonia, and yet there is no heart-failure. The pneumonia with the highest temperature-range is not necessarily the pneumonia in which heart-failure is most marked or earliest to develop. There are many diseases in which there is a much higher range of temperature and yet no evidence of heart-failure occurs.
If a prolonged high temperature is the cause of feeble heart-power by the parenchymatous changes which it induces in its muscular fibres, such a high fever is not met with in pneumonia, and the heart is rarely found at post-mortem to exhibit such changes. May not the heart-failure, as indicated by a rapid, feeble, and intermittent pulse in pneumonia, be due to the presence in the blood of a morbific agent (as in certain infectious diseases) which so affects the nerve-centres which supply the heart that its contractile power is diminished and its rhythm disturbed? The pulse early shows commencing heart-failure by each cardiac pulsation producing a variable filling of the arteries with blood; hence the beats first vary in force, then waves occur, then true intermissions. I have been able to detect this heart-insufficiency by these variations of the pulse within twenty-four hours after the onset of a pneumonia, and occasionally during the initiatory chill.
In children the pulse-rate is greatly increased; it may reach 200 in a minute. It is very small, unequal and irregular, but never intermittent.
In senile pneumonia the pulse is not a reliable indication. The pulse may be only 50, and yet this would be a rapid pulse for the particular case in which it occurs.
In old age, both in health and in disease, the pulse has a fictitious hardness on account of arterial changes. The pulse may not be intermittent or irregular, yet the heart may be very irregular and intermittent in its action. Again, the pulse may be feeble and intermittent and the heart be acting regularly.