THE INTRAVENOUS INJECTION OF FLUIDS 780 



tration of blood occurs are usually extreme clinical states which may have 

 been avoided by the administration of sufficient fluid. 



The intake of fluids is achieved normally by absorption from the 

 intestinal tract. This absorption occurs independent of the body needs, 

 and any excess fluid is readily eliminated by the kidneys. If the rate of 

 fluid intake exceeds the rate of elimination through the kidneys, the 

 tissues become a reservoir temporarily for such excess fluid which is later 

 reabsorbed from the tissue spaces into the blood and passed out through 

 the kidneys. The ingestion of large quantities of water, therefore, has 

 almost no effect in altering the quantity of circulating blood in the normal 

 individual, as shown by Haldane and Priestley. In pathological con- 

 ditions the same regulation of blood volume tends to occur. 



Fluid loss from the body occurs to a certain extent through the lungs 

 and skin. The bulk of fluid, however, is eliminated by the kidneys. The 

 kidneys are responsive to changes in the blood, and their activity in the 

 secretion of urine is the best index as to the state of water balance in the 

 body. Experience has shown that if the intake of food and fluids is 

 sufficient to produce a daily urine output of at least 1,500 c.c. (for an 

 adult), the total volume of body fluids is approximately normal. When 

 the daily urine output falls below 1,500 c.c. it usually does so because 

 the intake of fluids as such, together with the water contained in the 

 food ingested, is not great enough for the needs of the body. Cases of 

 anuria due to nephritis, and cases of cardiac failure of the congestion type, 

 for example, are exceptions to this rule for obvious reasons. The prac- 

 tical importance, therefore, of measuring the amount of urine voided in 

 twenty-four hours in almost all cases of acute illness is that it provides 

 direct evidence as to whether or not the body is being furnished with an 

 adequate supply of fluid. 



The Uses of Intravenous Infusions 



Intravenous injections are employed usually for four main purposes: 

 (1) to increase the volume of the blood and tissue fluids of the body; (2) 

 to increase the buffer action of the blood in acidosis; (3) to combat 

 toxemia by what is generally regarded as a washing out process; (4) to 

 assist in providing for the calorific requirements of the body. 



1. Intravenous Infusions to Increase the Volume of Blood and Tissue 

 Fluid. The following conditions may deplete the store of fluids in the 

 body: (A) fluid loss by (1) hemorrhage, (2) abnormal sweating, (3) 

 severe diarrhea, and (4) polyuria; (B) insufficient fluid intake by (1) 

 starvation, (2) inanition, (3) vomiting, (4) coma, and (5) delirium. 

 The chief symptom manifested as a result of dehydration of tissues in 

 these conditions is thirst, which constitutes nature's indication for treat- 



