While the rectal temperature must remain the most reliable criterion of the proper incubator temperature, it is by no means always accurate. The infant has a thermo-regulating mechanism, however feeble it may be in some, which controls to a certain extent the internal temperature. Thus, the lessened flow of blood to the extremities results in cold hands, which can be touched by the nurse at every feeding. Cold hands and feet may mean insufficient oxygenation, feeble circulation or an insufficiently heated incubator.
On the other hand, thermotaxis is strained by an incubator that is too warm, and perspiration may be found on the forehead of the feeblest infant. It is a sharp reproof that too much heat has been used. Often the perspiration in a warm incubator is not sensible, since the warm air favors rapid evaporation, and the activity of the sudoriferous glands is manifest by the appearance of sudamina and miliaria. Thus, in the case of St. Louis, who on account of a severe indigestion, had a subnormal temperature, the incubator heat was elevated to 92°, and on two or three occasions a very intense erythematous blush appeared, on the edges of which were typical sudamina and miliaria maculopapules. Yet this infant had suffered from hypothermia, with the incubator at 90°, for several days, caused by indigestion. When the incubator was elevated to 92 to 93°, the skin lesions appeared, without an abnormal rise in temperature, showing the adjustment of the organism to the increased heat supply.
It is obvious that the adjustment of the incubator temperature to the needs of the infant presents many difficulties. Different observers will regard the several indications with a varying importance, and hence, the great differences in opinion. There can be no question that the baby should be warm and comfortable. Some will feel most comfortable with a rectal temperature of 97°, others will need 99°, or even a fraction more. I shall refer to other phases of this in treating of special diseases.
While it was the rule to take the rectal temperature from two to four times daily, in every case of cyanosis the temperature was taken as an additional precaution (see Cyanosis). Repeated vomiting also should suggest a more careful watch. A very rapid loss in weight, when no other cause can be assigned, demands inquiry into the heat supply. Somnolence or cutaneous hyperesthesia are indications for inquiry into the bodily temperature. A convulsion may be the first sign of overheating.
While Rotch and Morse have had very good results in feeding premature infants on modified cows' milk, and in private practice it may at times be impossible to obtain a wet nurse, in an institution human milk is alone permissible. The advantages are so many that it does not seem worth the while to make comparisons. Rotch's argument that cows' milk can be accurately modified to the needs of the infant does not hold, since the human milk may also be modified. But the comparative sterile nature, the easier digestibility and the immunity-conferring properties of human milk are sufficient to counterbalance any possible advantage derived from an accurate control of any composition. Hence, wet-nurses must be obtained. We had five wet-nurses who, with their infants, slept in another part of the building. They furnished the milk but had nothing to do with the care of the incubator babies.
In the selection of wet-nurses I was guided by different principles than are usually expressed, since the assumption that a proper wet-nurse for such an infant is its mother or a wet-nurse whose infant is very young does not stand a critical analysis. It is a well-known clinical observation that young infants during the first few weeks of lactation are subject to a variety of dyspeptic disturbances, attributable to deleterious changes in the composition of mothers' milk. Reference to diarrhea, colitis, vomiting and flatulent colic is all that is necessary. Then, again, we know from the researches of Soldner and Camerer, Pfeiffer and others that human milk is strongest in the early days of lactation and gradually becomes weaker in proteids as the period advances. In a series of analyses they found the following averages (Zeitschr. f. Biologie, Band xxxiii):
Time of lactation, day.
8 to 11
20 to 40
70 to 120
Obviously, a wet-nurse whose infant is at least three months old, is most suitable for the premature baby.
Naturally, the general health of the wet-nurse must be carefully investigated, but local disease of any kind (nose, throat, skin, etc.)must also receive consideration. A small, well protuberant mammilla is desirable.
Our nurses had all passed the third month of lactation, and as far as could be ascertained, except in one instance, the milk was in every way suitable.
Another question is concerning the number of wet-nurses required. A wet-nurse should be able to supply the needs of two or three premature infants. Budin found that under proper feeding and increased demands of repeated nursing the milk gradually increased in quantity up to a certain limit.
Infants weighing less than 1800 grams are generally too feeble to nurse the breast and must be fed some other way, hence it was our custom to have the milk drawn and the prescribed quantity fed in other ways. The milk was occasionally drawn from the breast by means of the breast pump; generally the milk was drawn by manipulation, that is, a process of milking. It is really surprising, after a few days of practice, how readily the wet-nurse can "draw" her milk from her breast by "milking." The milk was drawn into sterilized glasses, poured into other sterilized glasses and kept in the ice box. This "milking" took place four or five times a day. In addition, the older infants were placed directly to the breast.
No chemical analysis was made of the milk; in our work, I assumed that the milk of five nurses at different periods would average a composition as follows: Proteids 1.50, sugar 6.50, and fat 3.75. This gives a caloric value of 670 large calories to the liter, or about 21 calories to the fluidounce. The calories were obtained in the usual way -- by regarding the heat value of fat as 9.3 to each gram; proteids and sugar each were calculated as 4.1 calories to the gram.
For practical purposes the assumptions of an average composition must be regarded as sufficient, as the daily variations are such that chemical analysis is almost impossible except in isolated cases where much milk is to spare.
Heubner considers the caloric value of mothers' milk as varying between 614 and 724 large calories (Kinderheilkunde, Vol. I) to the liter, and regards 650 calories as a fair average. I took a slightly higher average based on the analyses of American women (Rotch, Holt, etc.).
The methods of feeding varied with the needs of the patient. Very small infants -- under 1200 grams, were usually fed with the ordinary medicine dropper. The nurse fed the milk by dropping one drop after another on the tongue. In many cases the Breck feeder (see "Rotch's Text-Book") was used with good results. If the infant was very feeble, would swallow with difficulty or would be readily become cyanotic, gavage was employed. When the baby became more vigorous a small rubber nipple on a small bottle gave excellent satisfaction. A small nipple may easily be made by perforating the rubber cot on an ordinary medicine dropper. Later the infant was placed to the breast.
Monti recommends nasal feeding in premature infants. The milk is poured gradually into the nose by means of a small funnel. Finkelstein has also given his sanction to this method. Some writers, e.g. Batten, Lancet, 1899, have found nasal feeding very advantageous in persistent vomiting of the newly-born.
In older children -- after 2 years, this method is a well-recognized procedure, but in the premature the meatus is so narrow that it is exceedingly difficult to pass a catheter, while to permit its passage through the nose by gravity, subjects the infant to the dangers of an acute rhinitis from decomposed milk. It is impossible to cleanse the nose properly after feeding. In the nasopharynx, especially, particles of milk are likely to cling and by decomposition cause irritation, and a toxemia, more or less severe, may be a consequence.
The principle objection to nasal feeding is that it interferes with the respiratory tube. I have again and again observed cyanosis, even fatal, in very small infants result from milk running into the nasopharynx and nose when the head was kept down in oral feeding. These babies cannot breathe through their mouth and anything that tends to obstruct the nose jeopardizes its life.
For the reasons mentioned nasal feeding was not employed, but in all cases where swallowing could be done only with difficulty, feeding was accomplished by pouring the required amount of milk into the stomach through a catheter.
While this does not seem to disturb these infants, in spite of care, regurgitation with its attendant evils frequently follows the withdrawal of the tube. The milk should not be forced, but should be permitted to flow into the stomach slowly by the force of gravity. A too rapid flow is resented by the stomach. The infant should be held upright when the tube is introduced, since the recumbent position favors the flow of the regurgitated milk into the nasopharynx. Still, in very feeble, cyanotic infants the recumbent position only may be feasible. In withdrawing the tube great care should be taken that a drop does not fall into the larynx, which may cause fatal cyanosis.
From our experience I can not help but feel that gavage should be the preferable method of feeding in infants weighing less than 1200 grams (22 to 26 weeks gestation). In fact, in these cases it should be used at once without trying the drop method. As will be seen these feeble infants will become cyanotic on the slightest provocation, even the act of swallowing inhibiting the respiratory center. Deglutition is a dangerous act in these infants.
While it is the custom with infants born at term to give them very little food until the milk secretion is established, it is a safer rule in premature infants to begin administering water and milk a few hours after birth. Then life depends entirely on the reception of food, since there is little stored in the tissues.
Before estimating the quantity to be given at each feeding and the interval between the feedings, it is best to decide how much milk is to be given in the twenty-four hours. This is a most important matter, since insufficient nourishment is followed by rapid loss in weight, hypothermia, cyanosis and death. On the other hand, overfeeding brings on disastrous results from indigestion, intestinal putrefaction, somnolence, loss in weight, and fatal atrophy. It is the duty of the physician, therefore, to adjust the amount of milk to the digestive power and the needs of the individual infant. The digestive ability is judged from the condition of the digestive tract, the character of the stools, the presence or absence of vomiting, and the approximate amount of urine passed. The needs of the infant is estimated from its weight, its appetite, and the rectal temperature.
Most authors find it sufficient to give the quantity at a feeding and the intervals. Budin, however, lays down definite rules, and from his large experience these rules must be considered most precise and extremely practicable. It should be remembered, however, that this physician only considers infants weighing more than 1200 grams at birth.
Because time must be allowed for a certain degree of adaptation of the digestive apparatus to the milk, it is evident that during the first few days proportionately less nourishment must be administered; hence, Budin distinguishes two periods in the food adjustment:
1. During the first ten days of life.
2. After ten days.
The first division he again divides into three classes:
a. Infants weighing less than 1800 (1350 to 1800) grams.
b. Infants weighing from 1800 to 2200 grams.
c. Infants weighing more than 2200 grams.
In the accompanying Table 8, I reproduce the average amount of milk which he gives during the first ten days of life, but have taken the liberty to annex the caloric value, based on an average composition (650 calories to the kilogram).
While the amount in these tables seems somewhat arbitrary, it should be remembered that these figures are averages in quite a number of cases. It is obvious that the quantity of milk is progressively increased, so that the infant takes about three times as much on the tenth day as on the second day. If we calculate the energy quotient in these quantities with reference to the average weight (assuming 650 calories to 1000 grams of milk) the figures indicated in Table 9 are obtained.
I shall have occasion to refer to this table again.
Budin gives a very clear rule by which the proper amount of milk to be given after ten days' of life may be determined. It may be stated as follows: Take one-fifth of the weight of the infant, this gives the quantity of milk to be given to the premature infant in twenty-four hours. Or, multiply the infant's weight by two and take one-tenth.
If we assume any weight of an infant as N, one-fifth of this would be N/5, which is the quantity of milk to be given to any premature infant. Then 1000/N/5*650 = the number of daily calories ingested, and N/1000 = the number of kilograms in the infant's weight.
Hence the energy quotient is 130, that is, 130 calories are given for each kilogram of weight in twenty-four hours. As I shall discuss the caloric needs at length later on, it is only necessary to state that this is approximately the proper amount, as has been demonstrated clinically in many ways. If there is an error at all, it is on the side of liberality. As we shall see, my own experience teaches that this energy quotient at ten days is too high, since indigestion is the rule if food is given in such large quantities.
We shall next examine some records of the amounts given during my service (Table 10).
If these figures are compared with those of Budin (Table 8), it will be seen that the quantities we gave were considerably less for the corresponding period. And yet, vomiting and indigestion occurred in several cases. Thus, about the eighth day, St. Louis showed indigestion as shown by the character of the stools. On the twelfth day John H. had to have his food reduced for a similar cause. In the case of John M. there was in the beginning a too rapid increase, so that a subsequent increase could not be made for many days. In the case of Bernice, who commenced to vomit on the ninth day, the reduction in quantity was probably too great, since she cried with hunger after every feeding.
Perhaps, I was too cautious, but the previous poor results with overfeeding forced me to go to the other extreme. I shall give only three examples, and this is not with a view of criticising but rather to assist in arriving at a satisfactory conclusion as to the proper quantity to give (Table 11).
From this Table it is seen that the quantity given, with the exception of the first baby, was less than the averages laid down by Budin. Still most of these were near 1350 grams in weight. Mildred was overfed the first day and, consequently showed marked dyspeptic symptoms lasting for many days, in spite of the reduction of the daily quantity.
I refrain from giving any more figures from the first series for the simple reason that the larger infants had to be put on mixed feeding. Altogether, from this study the conclusion is justifiable that Budin's figures in regard to the daily quantity of milk are somewhat high for feeble infants, while for those weighing more than 1800 grams his averages, no doubt, are correct. Still I would prefer to make the daily increment less large so that at least two weeks would elapse before the infant gets one fifth of its body weight in milk for twenty-four hours.
During the latter part of the season I was enabled to draw a definite formula based on the caloric needs. This gives us a general rule for the feeding of those babies, which is eminently practical and, when properly controlled by noting the digestive functions of the infant, will lead to excellent results. Hence, I offer the following rules for the feeding of premature infants, and reserve the following Section (V) for discussing its value and practicability.
1. During the first day of life the premature infant should receive sufficient human milk diluted with an equal quantity of water, or 3 per cent sugar solution, so that the energy quotient shall be thirty calories. Any fractional part of the first day should receive a proportionate part of the energy quotient.
2. On the following days the energy quotient should receive an increment of ten every day, so that an energy quotient of 120 calories is reached by the tenth day. The quantities are represented in Table 12.
3. In many cases it is best to increase more gradually, especially if slight dyspeptic symptoms occur. It will be found more safe to keep the energy quotient the same for two or three days after reaching eighty, as indicated in Table 13.
4. After two weeks the energy quotient should be maintained near one hundred and twenty calories.
5. In all cases the stools must be watched for signs of indigestion. When the stools become greenish, or contain undigested curds it is best not to increase the energy quotient over eighty until these symptoms disappear.
The practice of making the energy quotient the basis of infant feeding is entirely rational, and its value has, as yet, been scarcely appreciated. While it is true that the length of gestation must also be considered, the weight must be the most practical guide.
I will give two examples of this method of feeding:
Baby A, arrived at 4 p.m.; weight, 1250 grams. Since its weight was one and one-fourth kilos, its daily amount of milk must be one and one-fourth times its energy quotient in calories. And since there are 670 calories (21 in an ounce) in a liter, the calculation is easily made, as follows (Table 14).
Of course, all these figures are given in round numbers, I can not claim that extreme accuracy is necessary. It should also be noticed that this is a hypothetical case, calculated on the basis of birthweight; but as the weight decreases during the first week the figures are somewhat too large. Each time the baby is weighed, and as we shall see, it should be weighed every day, the quantity of food for the next twenty-four hours should be calculated. Now, while this may seem very complex, in a given case a more simple rule can be followed, but this rule should remain the standard by which other milk schedules may be judged. Here is an example from actual life at the Baby Incubators (Table 15) and illustrates the harmful results of trying to feed too much.
I cite the case of Omega to illustrate how one may begin by adhering to the rule, but because the vigorous baby seemed so hungry on the fourth day the food was increased beyond the prescribed limits and in three days, as marked dyspeptic symptoms appeared, the food had to be reduced in amount.
From a study of Budin's figures and my own experience, I am convinced that the schedule given is about correct.
Note -- the first few days the total calories were increased by giving sugar-water. Where a discrepancy between the milk and calories appears it is due to the calculated calories in the 5 per cent sugar water.
Now, since there is a gradual increase of daily allowance of milk, and the amount the first day is represented by an energy quotient of 30, the daily increment is 10 calories. Moreover, since there are 670 calories in one liter, any quantity of milk is found by taking one and one half times the calories wanted. Hence, to obtain the quantity desired for any day (during the first ten days) we have the following algebraic equation:
x = 3w / 2000 [30 + 10(a-1)]
Whence, x = 3w / 200 (2+a)
Where w stands for the weight of the infant, and a represents the day of life.
Therefore, I offer the following practical rules to those who do not wish to calculate the amount of daily feeding on the basis of the energy quotient:
1. Before the tenth day -- Divide the weight of the infant by seventy (70) and multiply the quotient by the age plus two (2).
2. After the tenth day -- Divide the body weight by five (5).
These are simple and practical rules, -- the second rule is that of Budin.
It is curious how different physicians take different means of determining the capacity of the stomach. Rotch has depended mostly on post-mortem examination of the premature stomach; he reports three cases. One was a fetus, seven and a half month's gestation, weighing 1930 grams and having a gastric capacity of 18 cc. In another case, eight month's gestation, while the fetus weighted only 1230 grams, the stomach could hold 22 cc. In the third case, gestation thirty-two weeks, weight 1440 grams, the size of the stomach was much smaller, holding only 8 cc (2 drams).
Voorhees also recommends that the first quantities should be 1 to 2 drams (4 to 8 cc.) and gradually increased.
Perret states that having determined the quantity of milk (method of Budin) it is easy to decide the quantity of each feeding by dividing it by the number of feedings daily. He regards ten feedings as the proper number. Hence, the total quantity divided by ten will give the amount at each feeding. Budin has a very similar rule.
Monti recommends quantities from 20 to 40 grams.
We followed Voorhees' directions, mainly, beginning with one-half to two drams (2 to 8 cc.) at a feeding and rapidly increasing. Efforts at larger quantities frequently resulted in vomiting, which is dangerous in such infants.
As there is still so much uncertainty concerning the size of the stomach, considerable latitude must be allowed. I still believe that having decided the total quantity to be given, we best decide on the number of feedings daily and divide the quantity of milk by this. This is a very practical rule.
As to the interval, no definite rule exists. Rotch and Voorhees feed every hour. Perrett, Budin and Monti insist on two hour intervals. In fact, Monti finds the hourly feedings of Passini wrong (theoretically?), an infant should not be fed so often and so much. In artificially-fed infants he recommends three hour intervals. How he can get enough food into a premature infant in these intervals is a mystery. Our rule was about as follows:
Infants weighing less than 1500 grams were fed every hour in day time, sometimes less often at night (20 to 22 feedings daily).
Infants weighing 1500 to 2500 grams received their food every one and one-half hours (14 to 16 feedings daily).
Infants weighing more than 2500 grams can receive their food at two hour intervals.
Of course, the age of the patient must always be considered.
The infant weighs 1350 grams (about 3 pounds), 28 week's gestation. How much food should it receive on the third day of life?
Twenty feedings daily. Energy quotient 50, daily calories 66. This equals 100 cc. of milk -- each feeding 5 cc.
Table 9. Showing energy quotient in the amount of milk, as recommended by Budin, for premature infants during the first ten days of life.