It is unnecessary to discuss the propriety of having only well-trained nurses to take care of premature infants. When the danger of sepsis to these little ones is considered, especially in an incubator institution, only those trained in the principles of medical and surgical asepsis should be permitted to serve. The wet-nurses should have nothing to do with the incubators or their inmates.
As to the number of nurses necessary, the exigencies of different periods must decide. We had fourteen well-trained nurses. They worked in three shifts, each eight hours long; hence, there were four or five nurses on duty all the time. These nurses cared for twelve to fifteen babies, nearly half of which were "graduates," that is, babies out of the incubators. It will be seen that each nurse had under her care from three to five babies. As a rule, there was such a division of work that the nurse having the care of a very delicate infant, which demanded much attention, at the same time supplied the needs of older babies who needed less care.
It is a recognized rule in institutional nursing that the nurses who feed the babies should not handle the napkins or bathe the babies. This rule we did not follow, since rigid asepsis rendered it unnecessary and it was found more satisfactory that individual nurses look after all the wants of the infant.
The extreme susceptibility of the premature infant to atmospheric changes in temperature make the problem of heat supply one of the most important in their care. The protection of the newly born from the loss of heat is so generally recognized that the family physician or midwife usually makes some provision for its prevention. It is a mistake to assume that these babies always die from temperature reduction. In a few instances, when our physician arrived, the premature infant had been kept so warm that its temperature a short time after birth was over 100°.
Recognizing that the prevention of the initial heat-loss is most important the management early made provisions to minimize this danger. An ambulance and driver were provided which could be called upon day or night. A receptacle, in the nature of a small portable incubator, was utilized to keep the baby warm. The house physician and one of the nurses was usually dispatched to get the infant when a telephone message was received. Occasionally, due to a variety of causes, the infant could not be reached for three or four hours, but most commonly our physician, nurse and ambulance reached the premature infant in less than two hours, nevertheless, the number of infants for whom we were asked to send and had expired on arrival of the ambulance was very large. It is true that after it became generally known that the Incubator Institute was caring for all premature babies free of charge, physicians, midwives and parents would send for the baby ambulance for miscarriages of 4 1/2 to 6 months. Anything that moved was considered a sufficient subject to send to the incubators. But we gladly made an effort even in the most hopeless cases. One infant died on the way, many others which were in a hopeless prematurity arrived in fair condition to die a few hours later. During the three months of my service we received four infants each weighing less than 900 grams in very good condition, but who died shortly afterward.
As soon as the infant was reached, the rectal temperature was taken and it was quickly examined as to evidence of disease. It was then wrapped in cotton wool and placed into the portable incubator, a description of which follows, for which I am indebted to Dr. Gordon:
"This was designed for use in the ambulance and was made of enameled tin with a glass top. It is 12 inches wide, 18 long and 16 inches high. At the bottom is a sliding drawer which is pulled out by means of a handle. This is the bed and is composed of a strong wire netting held in a frame: a thick layer of cotton is put next to the wire netting, next a layer of several hot water bottles, next a still thicker layer of absorbent cotton upon which the baby, well rolled in cotton, lies. A thermometer lies beside the child. About 4 inches of the top is composed of the enameled tin through which are two holes 1 inch in diameter for the exit of air. The rest of the top is composed of a sliding glass door with a handle. The inlet of air was allowed for by opening the bottom drawer a trifle. Around the entire incubator goes an ordinary trunk strap which serves the double purpose of a handle and to hold the drawer and top in place.
"In the ambulance the incubator rested not on the floor but on a shelf suspended by springs and straps from the center of the roof of the ambulance. Near the front end of this shelf was an opening 3 inches in diameter; the open end of the sliding drawer was put just over this hole in the shelf, so there could be a free ingress of air. On a trip the temperature of the incubator was maintained, approximately at 92° to 94°."
The distance which the babies had to be carried was important. A long ride always had a pernicious influence, even when carried in our portable incubator. For example, Henry, gestation 7 1/2 months, weight 1733 grams, was brought six miles at night over very rough, unpaved streets and on arrival exhibited multitudinous hemorrhages from the skin and mucous membrane.
Quite a large number of premature infants came from places outside of St. Louis. Many times telegrams were received that Mr. ------ had started with an infant, asking us to meet him at the station, and although the ambulance never failed to be at the station only once out of perhaps six or eight such calls did the baby arrive. Most commonly the infant died after a short time and the parent would stop at the first station and return home.
A few infants were brought to the incubator in fair condition, wrapped in blankets, and during the warm weather such a method is practicable.
We found it inexpedient to encourage physicians outside of St. Louis to send babies to the institute.
As soon as the infant arrived its rectal temperature was taken and if this was below 96.5° a warm bath at 98° was given to restore the loss of heat, otherwise it was rubbed with warm oil, dressed and placed in the incubator.
Budin has laid great stress on the prevention of the initial loss of heat, and claims that of infants under 1500 grams with a temperature less than 32° C., 98 per cent die. Most of our infants arrived in good condition as regards the body temperature. The accompanying Table I, shows this.
It will be seen that three infants arrived with a temperature above normal; in all three instances the cause of this must have been the overheating of the portable incubator, although one of these had a temperature above normal when taken from home.
From all this I must conclude that the portable incubator should have a temperature of 90 to 94° for infants under 1800 grams, and 86 to 90° for infants weighing more than this. Of course, the temperature of the baby when first seen, the thickness of the clothing of the infant and the distance through which it is to be conveyed must all be considered.
In spite of much that has been written on this subject there is no unanimity as to the temperature at which the incubator should be kept. Heubner, in his recent textbook states that it has been found that a temperature of 30° C. (86° F.) is the proper temperature for premature infants, but such a general statement is insufficient for practical guidance. No doubt some of the differences in opinion may be attributed to the experience of physicians with infants of different ages. Probably, too, the variable amount of clothing used may partially account for these differences.
Finkelstein (Ther. d. Gegen., 1900) recommends 95° for very feeble and puny infants, in ordinary cases he uses 90° as the standard. This is much higher than some authorities. Voorhees claims that 86 to 92° is about correct. Rotch placed one infant, gestation 30 weeks, weight 2850 grams in the incubator at 94° and another weighing 2040 grams in the incubator at 90°.
All these figures, however, are outclassed by Blair (St. Louis Medical Review, May 21, 1904) who often starts with a temperature of 100°. He recommends a temperature of 93 to 97° for infants of 6 or 7 months' gestation. For 8 months' gestation he gives 88 to 95° as the proper temperature. Even for 9th month he uses as high as 90°. These figures are certainly higher than those given by most authorities and contrast strikingly with the temperature recommended by Budin and Rothschild.
Before stating the temperature of the incubator approved by Budin, it is well to point out that Monti erroneously declares that Budin keeps all his cases in the incubator at about 35° C. (Kinderheilkunde, Vol. III, page 635). This error induced me to try a higher temperature in one or two cases with results not encouraging.
Professor Budin has probably had more experience than any living authority and his results are so superior to others reported that his judgment in regard to any point regarding premature infants must receive the most respectful attention.
Budin (Le Nourrisson, 1900, page 18), in answer to the question concerning the proper temperature for the incubator, recites his experiences: It had been the custom at the Charité to keep the incubators at a temperature of 30° C. (86° F.), but he observed that the babies were very restless, cried and perspired easily; he concluded that the temperature was too high. Further experience only corroborated this surmise and he adopted the rule to keep the incubators at a temperature of 25 to 26° C. (77 to 79° F.). This was used in nearly every case except in a very few instances when the infant weighed less than 1000 grams. This is so much lower than what is generally given as the proper temperature that one might readily believe it to be an error if it were not repeated. A similar statement is found in the article by Perrett (Rev. d'Hygiene et de Med. Infant, Vol. II, No. 2, 1903, page 123) which is incorporated in the recent treatise by Rothschild.
It is obvious that the extremes -- 77° of Budin and 95° by Blair, show that this subject needs further investigation, or else we will have to conclude that the premature infant can survive a very wide range of atmospheric temperature. Now, what is the proper temperature?
The answer to this question is by no means as easy as would seem at first sight. It would be almost as difficult to give the proper temperature for the child or adult, and yet it is necessary to reach some sort of conclusion from the conflicting data.
Without attempting to draw any definite figures from the experience of the different authors, it is safe to assume that, partially at least, their different views are based on the practical results obtained in treating infants of different weight and age. Then, too, the bath treatment as practiced by Budin materially alters the danger of heat loss even with the incubator at the low temperature. But to use a uniform temperature of 77 to 79° for all cases, as he recommends, scarcely seems rational, as the metabolic activity in premature infants varies.
In the earlier months of this institution my predecessors used a much higher temperature for the incubators. Probably their practice was based on the experience of Rotch and the recommendations of Blair, whose paper had just appeared. We maintained a lower temperature of the incubators during my service and it may be instructive to study the results more carefully. It is an undisputed axiom that the incubator should be kept no higher than what is necessary for the individual infant. The heat in the incubator must be adjusted to the needs of the individual.
But how do we ascertain the needs of the infant; or, in other words, what are the criteria on which to base the temperature adjustment?
The final test, of course, is the number of recoveries, but the immediate indications are -- 1, the rectal temperature; 2, the warmth of the extremities; 3, cyanosis; 4, loss in weight; 5, restlessness; and 6, perspiration.
What is the proper rectal temperature? Several authorities (Monti, Budin) expect a subnormal temperature for a few days. Finkelstein warns us that overheating harms the babies and cites some experience. The experience of Rotch and Adriance also reveals the fact that the rectal temperature may readily be forced above normal by an overheated incubator and to the detriment of the infant.
Contrary to this, Blair states that he never permits the rectal temperature of a premature infant to fall below 99.5°, and declares that the rectal temperature may safely be maintained at 100 to 102°.
I tried to keep the rectal temperature between 97 and 99°. A temperature of over 100° or below 96.5° indicated that something was wrong. The temperature of the incubator at first was, as seen from the subjoined tables, from 88 to 92°. I repeat that I had to use a much higher temperature than I desired because the infants were clad very lightly.
For the purpose of proper study I have divided the infants into two series -- the first series being under the medical management of my predecessor (May to August), the second series were under my own direction (September - December). The first study is what effect has the temperature of the incubator on the rectal temperature (Tables 2 and 7).
It will be seen that the higher incubator temperatures of the first series usually resulted in fever in the infant. In the second series the temperatures were kept more normal. In both series all the babies died; the causes of death will be discussed later. In the first series the baby's temperature averaged about 5° above the surrounding temperature although there were, no doubt, feeble efforts on the part of the infant to keep its own normal temperature (Tables 2 and 3).
In the second series, with one exception, the difference also is about 4 or 5°. What feeble metabolism must that be which can not raise its temperature only 2° above the surrounding temperature?
From this it would appear that premature babies should be allowed from 5 to 6°, the difference between its temperature desired and the incubator. Hence the incubator should not be more than 92°. If the baby's temperature still falls, more clothing should be used, or warm baths should be given according to the method of Budin.
It was observed that the infants with an elevation of temperature were very restless, nervous and showed marked irritability. Two cases in the first series (not recorded in the table) had convulsions with the high temperature. I believe that these babies may be safely kept at 90° if well protected with clothing and a cap (Tables 4 and 5).
It is unfortunate that I find no records of the incubator temperature in the first series, but I have been assured that the babies were kept very warm (about 94°). Nearly all of them had fever and consequently did not do well.
In the second series, in spite of the fact that the incubators were kept at a much higher temperature than demanded by Budin, the infant's rectal temperature fell below the minimum point permissible (97°). (Tables 6 and 7).
A high temperature of the incubator and its results is exemplified in the case of Mildred of the first series (see chart 5). Owing to the incomplete data I have not tabulated additional cases. This case illustrates very forcibly the harmful effects of fever in the early stages. Even in the second series, in all instances there was a tendency to febrile movement, probably due to overheated incubators. Great precaution to prevent subnormal temperatures and consequent cyanosis suggested the temperatures (90-92°); yet, with the exception of the first few hours, this was too high, as evidenced by restlessness and perspiration.
Charts 1 to 7 illustrate the relation of the incubator and rectal temperatures in geometric curves. The upper curve gives the rectal temperature twice daily, while the lower zig-zag line illustrates approximately the temperature of the incubator. A complete correspondence is not seen, other factors enter into the augmentation of the temperature, such as the food supply, digestion, etc.
Judging from my own and the experience of the authorities mentioned above, the following conclusions may be offered.
1. The rectal temperature of the premature infant should be maintained at a temperature of 97 to 99°.
2. If the rectal temperature deviates from the standard it should be considered abnormal and measures taken to restore the normal heat.
3. Infants weighing less than 1000 grams should at first be placed in a temperature of 90 to 94°. However it is better to wrap the infant in a blanket and put on a cap; then an incubator temperature of 88 to 90° may be sufficient. Subnormal temperatures should be treated by warm baths according to the method of Budin.
4. Infants weighing from 1000 to 1500 grams (6 to 7 months gestation) should be kept at a temperature of 88 to 90°. If little clothing is placed upon them a temperature of 92° will often be necessary.
5. Infants weighing more than 1500 (1500 to 200 grams) show greater vitality and can be safely kept at 86°, if warmly clad.
6. All infants weighing more than 2000 grams (7 to 9 months gestation) should be warmly clad and kept at a temperature of 80 to 84°.
7. In all cases it is expedient to maintain the incubator temperature at the lowest point which the infant can comfortably bear. Higher temperatures predispose to indigestion, poor catabolism and cyanosis.
8. Attacks of cyanosis lead to depression of the body heat and should be treated by warm baths rather than an elevation of the incubator temperature.
Perspiration, sudamina, restlessness, and cutaneous hyperesthesia are indications of too much heat. The thermoregulating apparatus of the infant, however feeble it may be, is severely strained when the temperature is too high. Better results follow the lower temperatures. Excess of heat leads to a higher death rate.
Charts 1 and 2.
Charts 6 and 7.