Loss of strength occurs earlier and is more marked in pneumonia than in any other acute disease except typhus fever. Pneumonia patients become very weak within the first five days. The recovery of strength during convalescence is rapid.
Urine.—The urine at the onset of pneumonia is scanty, high-colored, and of high specific gravity. The amount of urea excreted is twice or three times more than the normal. The excess of urea increases until the crisis, and then suddenly diminishes with the fall in temperature, often below the normal standard.37
37 The daily amount of urea normally excreted is subject to great variations: it ranges between 355 and 460 grains. Parkes gives the result of 25 different observations: the lowest estimate was 286.1 gr. and the highest 688.4 gr.
Uric acid is also increased, and follows the same course as that of the urea. The inorganic salts of the urine, especially the sodium chloride, are diminished, and during the height of the pneumonia may be wholly absent. Much has been written concerning this diminution, which is by no means peculiar to pneumonia, but in no other acute disease is its diminution so constant and marked a symptom. Sodium chloride is probably retained in the system, for when the salt has been administered in large quantities none has appeared in the urine. The reappearance of the chlorides in the urine marks the approach of convalescence, and when the crisis occurs they appear in excess, following an opposite course to the urea and uric acid.
Although these last two ingredients are in very rare cases retained, the same as the chlorides, to appear when the crisis occurs, their retention is usually accompanied by a critical diarrhoea, which is followed by a prolonged convalescence. The diarrhoea is undoubtedly due to the irritation caused by the urea.
Parkes38 states that sulphuric acid is increased and phosphoric acid is diminished, but Huss affirms that both acids are diminished. With the increase of the urea and uric acid, and diminution of chlorides, biliary pigment will appear in the urine, and occasionally the biliary acids.
38 On the Urine.
Slight albuminuria is an ordinary phenomenon of pneumonia, and, though usually met with in the second stage, it may appear at any time. This symptom is present in 35 per cent. of all cases. Its presence is a point of resemblance between pneumonia and other acute blood diseases. The more severe the pneumonia, the more marked is the albuminuria. Some have ascribed its presence to passive hyperæmia the result of the pulmonary obstruction. This is questionable, except in those rare cases where venous engorgement is indicated by cyanosis, enlargement of the liver, jugular pulsation, etc.
In children the amount of urine corresponds to the quantity of fluid taken.
Critical Phenomena.—At the end of the first week, during which all the symptoms have increased in severity, the continued fall of temperature tells us that convalescence is established. As the temperature falls, profuse (critical) sweating occurs. Both of these phenomena may occur to such an extent that for hours the condition of the patient is one of collapse.