Physiological changes in the heart rate, respiratory rate, blood pressure and peripheral blood flow in low birth wight premature infants following oral gavage feedings

Preterm infants demonstrate physiologic instability during handling. The purpose of this study was to describe physiologic changes that occur before transfer, during transfer, and after transfer of the premature intubated and mechanically ventilated very-low-birth-weight (VLBW) infant. A secondary analysis of previously acquired data from an experimental study of 14 ventilated VLBW infants during skin-to-skin (SSC) holding was conducted. The results of this study reveal that the preparation for transfer and the transfer are physiologically stressful to the premature intubated VLBW. Minimizing nursing-care activities, excessive handling, and transfer of these infants until they are more stable or mature may be more favorable for their growth and welfare.

PHYSIOLOGICAL CHANGES IN THE HEART RATE, RESPIRATORY RATE, BLOOD PRESSURE AND PERIPHERAL BLOOD FLOW IN LOW BIRTH WEIGHT PREMATURE INFANTS FOLLOWING ORAL GAVAGE FEEDINGS by Patricia Cima Isaacs A thesis submitted to the faculty of the University of Utah in partial fulfillment of the requirements for the degree of Master of Science College of Nursing University of Utah June 1977 Copyright @ Patricia Cima Isaacs 1977 All Rights Reserved THE UNIVERSITY OF UTAH GRADUATE SCHOOL SUPERVISORY COMMITTEE APPROVAL of a thesis submitted by Patricia Cima Isaacs I have read this thesis and have found it to be of satisfactory quality for a master's degree. Beryl • Peters Chairman. Super\>isory Committee I have read this thesis and have found it to be of satisfactory quality for a master's degree. � .:2? Dal 1777 / Linda S. Book Member. Supervisory Committee I have read this thesis and have found it to be of satisfactory quality for a master's degree. �z�) Itt77 Dale . Supervisory Commillee THE UNIVERSITY OF UTAH GRADUATE SCHOOL FINAL READING APPROVAL To the Graduate Council of The University of Utah: I have read the thesis of Patricia Cima Isaacs In Its final form and have found that (I) its format, citations, and bibliographic style are consistent and acceptable; (2) its illustrative materials including figures, tables, and charts are in place; and (3) the final manuscript is satisfactory to the Supervisory Committee and is ready for submission to the Graduate School. �� 'i, '�'1 Date oved for the Major Department Chairman Dt:an Approved for the Graduate Council ABSTRACT Twelve clinically stable infants with weights ranging from 1110 to 2000 grams and with ages ranging from five to 31 days. were evaluated to determine their physiological response to oral gavage feedings. Follow- ing feedings of l2-calorie and 24-calorie-per-ounce cows'-milk formula there was no significant change in heart rate, respiratory rate, or blood pressure. eral blood flow in all 12 infants increased. Periph- These infants demonstrated a strikingly different response from that of full term infants who are breast or bottle fed. ACKNOWLEDGEMENT This author expresses appreciation to the members of her committee: Dr. Beryl Peters. Dr. Linda Book, and Ms. Joan Uhl for their guidance. encouragement and support during this study. Gratitude is expressed to Mr. Richard Chang for his technical assistance and advice which greatly facilitated this study. and to Dr. Miriam James for her encouragement and guidance .. Deepest thanks and gratitude are expressed to my children. Timothy, Tamara and Teri Lou. Linda Book and to the National Also to Dr. Foundation-rt~arch of Dimes t Northern Utah Chapter, for their help and encouragement throughout my education. 'would have been possible . Without them none of this TABLE OF CONTENTS Abstract Acknowledgement iv v Chapter I II III IV Introduction Problem Purpose Review of Literature Definition of Terms Research Questions 8 10 Method 11 Results and Discussion 15 Summary Conclusions Nursing Implications Recommendations 25 1 2 2 .3 27 29 29 References .31 Appendices 1 Peripheral blood flow tracing 2 Data sheet .3.3 .34 Vita CHAPTER I INTRODUCTION Provision of an adequate nutritional and caloric requirements for the low birth-weight premature infant is essential because of his rapid rate of growth. The premature infant requires increased calories per unit of body weight, compared with the normal full term infant (Babson, 1971). Oral feeding is the usual method of providing nutritional requirements for an infant. Previous investigations have shown that oral feedings of the full term newborn can cause significant alterations in peripheral blood flow (Yao, Wallgren, Sinha & Lind, 1971) . Alterations in peripheral blood flow in the in- fant suffering from nutritional depletion carries the constant risk of interruption in growth and brain cell division at a critical period in his development (Babson, 1971) . A premature infant is known to be physiologically more labile than the normal newborn; therefore he may demonstrate even more dramatic changes in his peripheral blood flow, heart rate, respiratory rate and blood pressure. Marked alterations in these parameters could be detrimental to him as a cause of, for example, hypo- 2 tension and acidosis produced by decreased respiratory effort. Such deviations from the normal contribute to the development of necrotizing enterocolitis and intraventricular hemorrhage (Book, Herbst, Atherton & Jung, 1975). Studies in animals and humans have shown that hypertonic elemental diets in premature infants are associated with an increased incidence of necrotizing enterocolitis (Book et ale 1975). It is possible that this disease may be attributed to the exaggerated physiological changes produced by hypertonic formulas. in contrast to those resulting from an isotonic formula. in the small birth-weight infant. For this reason, the osmolarity of the formula should be considered when feeding the premature infant. Problem To determine whether there are physiological changes in the heart rate, respiratory rate, blood pressure and peripheral blood flow in low birth-weight infants following oral gavage feeding. Purpose To determine the effect of oral gavage feedings of 24-calorie-per-ounce and l2-calorie-per-ounce formulas on the peripheral blood flow, heart rate, respiratory rate and blood pressure of low birth-weight infants. J Review of Literature No studies were found, after a search of the literature, to support the theory that feedings in low birth-weight premature infants produced a physiological change in heart rate, respiratory rate, blood pressure and peripheral blood flow. However, it has been report- ed that feeding the low birth-weight premature infant by gavage is associated with a high incidence of side effects. Such side effects include irritation of muc- ous membranes, stomatitis and perforation of the stomach. The most common hazard of tube feeding appears to be an improper rate of feeding flow which ideally should result in Sec entering the stomach in S to 10 minutes (Chinn, 1971). If the rate of flow is too rapid it will interfere with peristalis, causing abdominal distention and excessive regurgitation. This hazard can be prevent- ed by care in selection of catheter size, the amount of fluid per feeding, the rate of flow and the frequency of the feeding (Chinn, 1971). Controversy still exists regarding the feeding of low birth-weight premature infants. Babson, (1971) pre- sented evidence which suggests that a prolonged delay in providing the low birth-weight infant with calories and water will lessen his chance for normal development. The infant who is premature and has a low birth-weight has an increased requirement for calories per unit of 4 body weight. This need is based on a potentially more rapid rate of growth, comparable to that of the fetus rather than to that of the mature infant (Babson, 1971). Since the need for volume in relation to body weight is much greater for the healthy mature newborn, it could be hypothesized that the infant who is premature, or low birth-weight, with an increased caloric requirement might have distention of the viscera which could interfere with blood flow, venous return and respiratory volume. An investigation by Yao et al. (1971) evaluated the peripheral circulatory response to feeding in the normal healthy newborn infant. The investigators observed that oral feedings in the healthy newborn produced a substantial decrease in peripheral blood flow within a half-hour after ingestion. Riley (1954) and Celander (1960) statec that the circulatory system or the newborn infant is characterized by a relatively greater blood flow and less vascular resistance compared to the adult, and that the newborn infant is capable of efficient vasomotor control or its peripheral circulation. Their findings were fur- ther supported by Wallgren and Lind (1967) whose research indicated that the blood flow in the extremities is greater and the resistance to flow is less in the newborn than in the adult; also that this difference is more pronounced in the premature infant. These invest- igations have raised questions regarding the effect of 5 feeding on the peripheral blood flow in low birth-weight premature infants. Research by Yao et ala (1971) also analyzed the peripheral vascular response in relation to feeding in the newborn. They believed that observations of the blood flow in limbs might contribute to an understanding of the changing circulatory demands associated with ingestion and digestion of food during the early days of life. The study comprised of 39 full term infants, ranging in weight from 2460 grams to 5000 grams ( mean weight was 3600 grams). Sexes were equally distributed; ages at the time of the investigation ranged from 24 hours to nine days. All were fed breast milk. The mid- portion of the calf was used to measure the peripheral blood flow. Recordings were made immediately prior to a feeding and were repeated every )0 minutes for three hours during the post-prandial period. Yao et ala (1971) found that, while the infant's blood pressure remained unchanged during the survey there was a marked drop in perfusion, averaging 49 percent of the control value in the first post-prandial observation at )0 minutes. They attributed this change entirely to increased regional vascular resistance. In addition, they stated that the post-prandial vasoconstriction in the lower leg appears to be unique to the newborn and has not been reported in the adult human or in other mammals. They further suggested that the early 6 circulatory demands provoked by feeding are relatively greater in the newborn" than in the adult, and that this increase may be partially at the expense of the lower limb perfusion. Their study also reported that the vaso- constrictive response is unique to the newborn; it may be that the feeding during the neonatal period is associated with greater muscular effort than later in life. Perhaps the demand for increased blood perfusion during food ingestion and digestion, involving the muscular groups engaged in this activity, is responsible for the changes in the circulatory pattern. noted that the newborn inf~~t In addition, they usually ingests a larger volume of food relative to its body weight than does the adult. Wallgren and Lind (1967), postulated that the cardiovascular system of the newborn infant may be less capable of coping with circulatory situations which occur after meals. to They noted that the acute withdrawal of 10 15 percent of the estimated blood volume of the new- born is followed by an immediate drop in cardiac output which is considerably greater than that of an adult after a meal. If it is assumed that there is a significant relationship between vascular response and digestion, it is possible that the pooling of blood which occurs in the gastrointestinal tract of the newborn after a meal would have a similar effect, if blood were to be withdrawn from from the infant's circulation. This withdrawal would 7 result in a drop in cardiac output and could explain the characteristic early vasoconstrictive pattern observed in the newborn by Yao et ale (1971) as· opposed to the adult pattern. Wallgren and Lind (1967), using a plethysmograph, made quantitative studies on the human neonatal circulation. They adapted the occlusion plethysmograph for use in newborn infants in which the peripheral circulation was analyzed. The most commonly-used technique for the study of peripheral circulation is that of the venous occlusion plethysmograph, where the arterial flow to a limb is measured by volume increase of the segment after occlusion of the venous outflow. It has been demonstrated that blood flow in the extremities is greater and resistance to flow less in the newborn than in the adult. This difference has also been reported to be con- siderably more pronounced in the premature infant. Reininger and Sapirstein (1957), described the effect of digestion on the distribution of blood flow in the rat. The study involved 117 rats and demonstrated that during digestion there was a uniform increase in the blood flow to all organs. The splanchnic organs did not gain an increased blood supply at the expense of the supply to other organs; on the contrary, all organs benefited from the increased cardiac output associated with digestion. Yao et ale (1971), noted that feeding provoked a 8 considerable change in the circulatory pattern of the newborn, including that of the lower leg. Their investi- gation indicates that the normal infant appears capable of coping with the circulatory demand via peripheral vasomotor control. Smallpeice and Davies (1964), and Wu and Teilmann (1967), suggested that there were metabolic advantages to early and adequate feeding in infants of low birthweight. Whether feedings caused any respiratory diff- iculty in these infants however, remain controversial (Barrie, 1968). It has been demonstrated that the circulatory response to feeding of the newborn differs from that of the adult. Previous studies have dealt only with the mature infant. It could be hypothesized that the prem- ature infant who is known to have greater lability of its autonomic nervous system, temperature stability, and vascular stability, may have more marked changes in circulatory and respiratory responses to feedings than the mature infant. Definition of Terms Physiological Changes Changes in parameters of the heart rate, respiratory rate, blood pressure and peripheral blood flow before and after feeding of the low birth-weight premature infant. 9 Premature Infant Infants in this study were those weighing less than 2000 grams whose clinical condition was stable. stud:y Patients· Patients for this study were premature infants hospitalized at the Intermountain Newborn Intensive Care Center. Clinical Stabilit:y Assessment was made of the absence of vomiting, diarrhea, abdominal distention, or severe respiratory disease requiring mechanical ventilation and oxygen concentrations of greater than 40 percent. Feedings Infants studied were fed by the oral gavage method, receiving eight feedings per day. In the event that an infant under investigation had not previously received that volume of formula (20cc/kg) the maximum amount known to be tolerated by the infant was given. Formula The results of two milk formulas currently used at the Intermountain Newborn Intensive Care Center was investigated: (1) 24-calorie-per-ounce Similac. (2) 1:1 dilution of this formula, resulting in 12calorie-per-ounce Similac. The effects of both formulas were evaluated on the same day for each infant under investigation. 10 Research Questions The research questions proposed in this study are: 1. What is the peripheral blood flow response to oral gavage feeding of milk formula in premature infants who weigh less than 2000 grams? 2. What changes occur in respiratory rate, heart rate, and blood pressure following oral-gavage feedings? J. Do the physiological changes and peripheral blooe flow response differ ·in infants whose weight is less than 2000 grams, when they are fed a low density 12-calorie-per-ounce formula compared to a high density 24-calorie-per-ounce formula? CHAPTER II METHOD The study sample consisted of 12 premature infants whose weights ranged between 1110 and 2000 grams, with a mean weight of 1790 grams. The infants were clinically stable and were hospitalized in the Intermountain Newborn Intensive Care Center, University Medical Center, Salt Lake City, Utah during the period of June 1976 and January 1977. The age and sex of the infants in the sample were not controlled. Permission for participation in the study was obtained from the parents. Impedence electrodes were placed on the infant's chest for the purpose of recording the respiratory rate and the heart rate. An infant blood pressure cuff and a Doppler ultrasound instrument, which is specifically designed for measurement of infants blood pressure (Dweck, Reynolds, & Cassady 1974) was used. Blood flow was measured, using the principles of venous occlusion plethysmography (Yao et ale 1971), with a mercury-in-silicone rubber strain gauge (Whitney, 1949). The mercury-in-silicone rubber strain gauge used ranged in size from 2.5 ems. to 5 ems. in diameter and was 12 selected in accordance with the size of the infant. The gauge was placed around the midcalf of the leg and connected to the plethysmograph, which was attached to an oscilloscope to record flow of blood~ A rubber latex blood pressure cuff was placed around the mid-thigh and was used to occlude venous blood flow by inflating the pressure in the cuff to 50 mmHg. flow was occluded for 10 seconds. The venous blood The leg was raised to a level at which the measured section of the limb was at the anterior axillary line, which is at the level of the right atrium, to insure equal venous flow and pressure. The mean of three consecutive, technically- good tracings were taken as representative of the calf blood flow. A polaroid camera was used and the tracings were photographs of the periperal blood flow as it appeared on the oscilloscope screen. (Appendix 1) Heart rate, respiratory rate and blood pressure were recorded 15 minutes prior to the feeding for the purpose of establishing a baseline for the infants vital signs and then were taken immediately following the feeding. Two readings were taken at 15 minute intervals and four at 30 minute intervals there~after. Recordings of peripheral blood flow were taken 30 minutes prior to the feeding for the establishment of a baseline and then four times at 30 minute intervals post-prandial. When- ever spontaneous limb movement occured, time was allowed I) for the infant to regain a steady state before blood flow was recorded. This completed the data gathering process for the first feeding; the process was repeated immediately for the second feeding because two hours and )0 minutes had elapsed and the infants were fed every three hours. The baselines for the heart rate, resp- iratory rate, blood pressure and peripheral blood flow was re-established before giving the second feedings. All data was recorded on the infant's data sheet. (Appendix 2) The 12 premature infants were randomly divided into two groups. The first group of six infants were fed; (1) a standard commercial 24-calorie formula, with an osmolarity of )40 m Osm/l first, followed by (2) a 12calorie formula, with an osmolarity of 170 m Osm/l. The second group of six infants were fed; (1) a 12-calorie formula, with an osmolarity of 170 m Osm/l first, followed by (2) a standard commerical 24-calorie formula, with an osmolarity of )40 m Osm/l. Feedings were given by oral gavage, the usual method of feeding an infant of this size. The effects of both formulas were recorded for each infant on the same day. The volume of formula fed to each infant was equal to 20cc/kg of body weight. If the infant under investigation had not received that volume of formula previously, the maximum amount known to be tolerated was given. The amount chosen was the 14 minimum volume of formula meeting the nutritional demands of an infant of this size, when fed every three hours. CHAPTER III RESULTS AND DISCUSSION Analysis of the data was performed on the.Canola 167 P electronic calculator. The paired t-test was used for the statistical operation. The infants were kept in a thermoneutral environ~ent; their skin temperatures ranged between 92 to 99 cegrees Fahrenheit. The isolette temperatures ranged between 88 and 92 degrees Fahrenheit. The mean birth weight of the infants was 1790 grams, ~\,i th a range between 1110 and 2000 grams. Four of the subjects were females and eight subjects were males. ~ean The age of the infants was 21 days (minimum age five days, maximum age )1 days). All the infants were judged to be clinically stable by the investigator. The mean values of heart rate, respiratory rate and blood pressure as related to time intervals and type of formula given the infants at the first feeding are shown in Tables I and II. The mean value of the heart rate in the group of six infants who were first fed a 12-calorie-per-ounce formula ranged from 144 to 155 beats per minute for the 16 complete time period of the study. The mean value of the heart rate for the second group of six infants. who were fed 24-calorie-per-ounce formula first, ranged from 142 to 155 beats per minute for the same complete time interval. Post-feeding heart rates did not differ significantly from the pre-feeding values in any of the 12 infants studied. (Tables I and II) The mean values of respiratory rate in the six infants d 12-calorie-per-ounce formula first ranged from 32 to 42 breaths per minute. In the second group of six infants who were fed a formula of 24-calorie-perounce formula first, the mean values of respiratory rate ranged from 31 to 48 breaths per minute. The respiratory rate showed no substanial change in the post-prandial values of the 12 infants studied, compared to pre-prandial values. (Tables I and II) The mean blood pressure of the infants fed l2-calorie formula first ranged from 82 to 93 mmHg. The range in the second group of six infants, who were first fed 24-calorie-per-ounce formula varied between 86 and 99 mmHg. Blood pressures did not change significantly during the period of the study in either group of infants. (Tables I and II) All infants in the study, regardless of the type of formula fed first, whether 12-calorie-per-ounce or 24calorie-per-ounce. demonstrated an increase in peripheral blood flow following the feedings. In those infants re- 17 Table 1 Changes in Heart Rate, Respiratory Rate and Blood Pressure Following Feedings in Six Infants Receiving 12-Calorie-Per-Ounce Formula Time Period Mean Heart Rate Mean Respiratory Rate Mean Blood. Pressure *-30ac 148 40 83 0 152 42 82 15pc 152 42 78 30pc 149 41 82 60pc 145 40 91 90pe 145 37 88 120pe 144 32 86 *-30ae 149 37 82 0 155 40 89 15pe 148 43 85 30pe 153 46 84 60pc 155 42 93 90pc 153 41 8) 120pc 151 40 85 **Abbreviations: ae=before feeding, pc=after 0 = feeding time * = baseline· values eding 18 Table 2 Changes in Heart Rate, Respiratory Rate and Blood Pressure Following Feedings in Six Infants Receiving 24-Ca1orie-Per~Ounce Formula Time Period Mean Heart Rate Mean Respiratory Rate Mean Blood Pressure *-30ae 148 37 94 0 1.53 48 88 l.5pe 1.50 38 92 JOpe 1.51 37 93 60pe 1.50 J7 86 90pc 1.56 41 89 120pe 146 3.5 92 *-30ac 146 J8 91 0 1.52 39 96 l.5pc 1.53 4J 99 JOpe 148 41 94 60pc 142 J1 98. 90pc 149 41 91 120pe 1.5.5 40 97 **Abbreviations: ac=before feeding, pe=after feeding 0 * :::; feeding time baseline values 19 ceiving 12-calorie-per-ounce formula followed by 24calorie-per-ounce formula the maximum increase in blood flow was 80 percent over the pre-feeding value as observed at 90 minutes post-prandial. The increase in peripheral blood flow from the baseline value was statistically significant at the 0.01 level. The per- ipheral blood flow at 60 minutes showed a 62 percent increase over the feeding value (p<0.05). At 120 minutes the peripheral blood flow was still 25 percent greater than the pre-feeding values with a statistical significance at the 0.05 level. (Figure I) The group of infants who received a 24-calorie-per ounce formula first showed their maximum increase in peripheral blood flow of 47 percent at 30 minutes postprandial which was significant at the 0.05 level. The blood flow at 60 minutes post-prandial returned to the pre-feeding baseline value. The cause for this change has not been determined at this time but could be attri- buted to the small size of the study sample. The in- fants further demonstrated an increase of 35 percent at 90 minutes and a 41 percent increase at 120 minutes. These increases showed no statistically significant value during the feeding. (Figure I) Infants receiving 12-calorie-per-ounce formula at the second feeding showed increases in blood flow of 5 percent at 30 minutes, 32 percent at 60 minutes, 42 20 12 CALORI ES VERSUS 24 CALORI E PER OUNCE FORMULA -1st FEEDING 12 CALORIE 1st FEEDING 100 100 + 80 24 CALOR IE 1st FEEDI NG 80 60 PERCENT INCREASE IN PER IPHERAL BLOOD FLOW 40 OVER PRE-FEEDING VALUE 60 20 20 40 O-t--~~~~~ * O-+-~--~~~ TIME IN MINUTES FOLLOWING FEEDING * p S • .05 pS=+.OI 12 CALOR 1ES VERSUS 24 CALOR I E PER OUNCE - 2nd FEEDI NG 12 CALORIE 2nd FEEDI NG 100 100 80 80 PERCENT INCREASE IN 60 PERIPHERAL BLOOD FLOW OVER PRE-FEEDING VALUE 40 60 20 20 24 CALORIE 2nd FEEDI NG * 40 o -I--LL..JI.,.......K....A......It....U.-...IL...oI.- 30 60 90 120 o NC Nt 30 60 90 120 TIME IN MI NUTES FOLLOWING FEEDING PERCENT INCREASE IN PBF FROM BASELINE PRE-FEEDING VALUES WITH PAIRED T-TEST LEVEL TO DETERMINE SIGNIFICANCE OF ALTERATION FROM PRE-FEED VALUE. FIGURE I 21 percent at 90 minutes, and J2 percent at 120 minutes. These increases were not statistically significant. (Figure I) Infants who received a 24-calorie-per-ounce formula at the second feeding showed no increase in blood flow from pre-feeding baseline values at JO or at 120 minutes. At 60 minutes the increase was 38 percent, with the maximum increase of 45 percent reached at 90 minutes, which was statistically significant at the 0.05 level_. (Figure I) Figure II illustrates a comparison of changes in peripheral blood flow when a 12-calorie-per-ounce formula was fed to the infants first, followed by a 24~ calorie-per-ounce formula in contrast to a first feeding of a 24-calorie-per-ounce formula followed by a 12calorie-per-ounce formula. The statistically signifi- cant values are the same as those shown in Figure I. Figure III illustrates the increase in peripheral blood flow over the pre-prandial values of: (1) 12calorie-per-ounce formula at both first and second feedings, and (2) 24-calorie-per-ounce formula at both first and second feedings. The statistically significant values are the same as those shown in Figure I. To determine significant differences between peripheral blood flow of those infants receiving first feeding of -either 12-calorie-per-ounce formula or 24- 22 calorie-per-ounce formula at 30, 60, 90, and 120 minutes post-prandial, paired sts were computed. Significant differences were found (Figure I) between peripheral blood flow levels which sUbstantiate the results shown in Figures I, II, and III. 23 12 CALORIE-1st VERSUS 24 CALOR I E PER OUNCE FORMULA -2nd FEEDING 12 CALOR I E 1st FEEDING 100 PERCENT I NCREASE IN PERIPHERAL BLOOD FLOW OVER PRE-FEEDING VALUE 100 80 80 60 40 60 20 20 24 CALORI E 1st FEEDING 40 o -+-..I..L..L.......L..A~.J.-M;....a..... 30 60 90 120 O-+-~~.....a...~~ TINE IN MINUTES FOLLOWING FEEDING 24 CALORIE-1st VERSUS 12 CALORIE PER OUNCE FORMULA-2nd FEEDING 24 CALORIE 2nd FEED I NG 100 100 80 80 PERCENT INCREASE IN 60 PERIPHERAL BLOOD FLOW OVER PRE- FEEDING VA LUE 40 60 20 20 40 o -I---'-'-'-----.......Io'-l......K:;..L_ 30 60 90 120 FIGURE 2 12 CALORI E 2nd FEED I NG o -+--U-4--lC...A-.l.c......I-...I..L..L_ 30 60 90 120 TIME IN MINUTES FOLLOWING FEEDING 24 12 CALOR 1E PER OUNCE FORMULA 100 12 CALORIE 1st FEED ING 100 80 80 60 PERCENT INCREASE IN PE R IPHERAL BLOOD FLOW 40 OVER PRE-FEEDING VALUE 60 20 20 o 12 CALORIE 2nd FEEDING 40 -+-~--L,..,jL.....L...£.-II~ O-+-~~:..I.-..IiC....I..--&....tI1.... 30 60 90 120 30 60 90 120 TIME IN MINUTES FOLLOWING FEEDING 24 CALOR I E PER OUNCE FORMU LA I 00 24 CALORIE 1st FE ED I NG 100 80 80 PERCENT INCREASE IN 60 PER I PHERAL BLOOD FLOW OVER PRE- FEED I NG VA LU'E 40 60 40 20 20 o -+-~--II:Ia........I~~_ 30 60 90 120 o 24 CALOR IE 2nd FEEDING NC NC 30 60 90 120 TIME IN MINUTES FOLLOWING FEEDING FIGURE 3 CHAPTER IV StJMMARY An investigative study was done with regard to the following questions: 1. What is the peripheral blood flow response to oral gavage feeding of milk formula in premature infants who weigh less than 2000 grams? 2. lNhat changes occur in respiratory rat"e, heart rate. and blood pressure following oral-gavage feedings? 3. Do the physiological changes and peripheral blood flow response differ in infants whose weight is less than 2000 grams, when they are fed a low density 12calorie-per-ounce formula compared to a high density 24calorie-per-ounce formula? Following oral gavage feedings of 12 clinically stable premature infants \-'lhose weight was less than 2000 grams, there were no significant changes in heart rate, respiratory rate or blood pressure in either group of infants when fed a 12-calorie-per-ounce formula compared to a 24-calorie-per-ounce formula at the first feeding. The means, baseline values and time intervals are shovnn in Tables 1 and 2. 26 The premature infants studied demonstrated significant increases in peripheral blood flow to the lower limb when fed either 12-calorie-per-ounce or 24-calorieper-ounce formula. The group of six inrants who were fed 12-calorie-per-ounce formula at the first feeding showed a significant increase of up to 80 percent in peripheral blood flow to the lower limb; this value was the maximum increase and was observed at 90 minutes post-prandial. The group of six infants who were fed 24-calorie-perounce formula at the first feeding demonstrated their maximum increase in peripheral blood flow to the lower limb of 47 percent at )0 minutes post-prandial. which was a statistically significant value. The values and increases in peripheral blood flow as related to time, formula, and first or second feeding comparisons are given in Figures I, II, and III. The increase in per- ipheral blood flow in the premature infant is strikingly different from that of the term infants studied by Yao et al. (1971), using a similar method of measuring peripheral blood flow. That study showed decreases in per- ipheral perfusion of up to 50 percent. The physiological changes in heart rate, respiratory rate and blood pressure demonstrated by the premature infants were within normal parameters when the infants were fed a low-density12-calorie.-per-ounce formula compared to a high-density 24~calorie-per-ounceformula. The 27 changes in blood flow response were greater in the group of infants receiving the low-density 12-calorie-perounce formula first feeding. Conc~usions Conclusions which can be drawn from the data collected during this study are: 1. The premature infant appears to differ from the adult and full term infant. Studies in adults indicate that there is an increase in cardiac output and heart rate with concomitant increases in peripheral blood flow following ingestion of high protein-content meals. An increase in perfusion to the gut is assumed to occur at the same time but has not been demonstrated (Abramson & Fierst, 1941). Yao et al. (1971) in a study involving term infants who were fed breast milk, stated that the term infant demonstrated an increase in heart rate with no change in respiratory rate or blood pressure and showed a decrease in peripheral perfusion to the lower limb. 2. The premature infant appears to differ from the adult and from the full term-infant in that heart rate does not increase after feeding as in the adult and full term infant but peripheral blood flow increases in amounts similar to that of the adult. One might hypothe- size that the full ,term infant develops a vasoconstrictive response to the peripheral vessels- to insure 28 adequate perfusion of the gastrointestinal tract during digestion. The adult appears to increase cardiac output to the entire body following ingestion. Because the heart rate recordings in the premature infant remained stable during the study it would be difficult to assume that the premature infant's cardiac output increased; since this was not measured it remains speculative. The absence of peripheral vasoconstriction in the premature may indicate that he is incapable of shunting increased volumes of blood to the gastrointestinal tract, in contrast to the term infant. 3. Another reason for the increase in peripheral blood flow in premature infants may be the method of feeding. Breast or nipple feeding introduces milk grad- ually into the gastrointestinal tract so that gradual digestion and assimilation of nutrients can occur. Gavage feeding necessary because of the absence of suck reflex in prematures, may produce an unusual demand on the circulation via a larger quantity of milk suddenly entering the gastrointestinal tract. 4. The cause of the increase in peripheral blood flow in the adult or the premature infant is not known. It is possible that distention of the intestinal lumen may result in a release of gastrointestinal hormones producing, a pe~ipheral vasodi,latory ef:fect. 5. 'The observation that peripheral blood flow in 29 those infants studied remained at a higher level over pre-feeding values has important nursing implications with regard to the timing of the next feeding. It may be inadvisable to initiate feedings before the circulatory system has stabilized at the pre-feeding values. This study did not establish the ideal time interval between feedings, as peripheral blood flow measurement was carried out only to two hours post-prandial. The data suggest that two hours may be too short an interval between feedings for the low birth-weight premature infant. Nursing Implications Nursing implications which should be considered when feeding the low birth-weight premature infant are: (1) the method and route used in gavage feeding the infant; (2) the rate of flow at which the formula is entering the stomach; (3) the selection of catheter size; (4) the caloric requirements of the infant; (5) the volume of fluid given to the infant; and (6) the frequency or the time interval between the feedings. Recommendations The investigator suggests the following for further research in the low birth...,weight.premature infant. (1) a larger sample of low·birth.;..weight premature infants; 30 plus grouping of these infants according to age and weight; (2) determination of baseline values for peripheral blood flow by first feeding the infants sterile water; (J) a longer time interval between feedings, perhaps four to six hours; (4) a first feeding followed by a 24-hour interval before the second, in contrast to two feedings on the same day; (5) a wider variety of feedings with different caloric values, such as 12, 20, 24, and JO-calorie-per-ounce formulas and feedings of 5 and 10 percent solutions of glucose. REFERENCES Abramson, D.I., & Feirst, S.M., Peripheral Vascular Response in Man During Digestion, American Journal Physiology, 111:686, 1941 . Babson, S.G., Feeding the Low Birth Weight Infant, Fetal and Neonatal Medicine, Journal of Pediatrics, 12:4, 694-701, October 1971 Barrie, H., Effect of Feeding on Gastric and Oesophageal Pressure in the Newborn, Lancet i: 1158-1160, 1968 Book. L.S., Herbst, J.J., Atherton, S.O., & Jung, A.L., Necrotizing Enterocolitis in Low Birth Weight Infants Fed an Elemental Formula, Journal of Pediatrics, §Z:4, 602-605, October 1975 Brandt, L.J., Castleman, L., Ruskin, H.D., Greenwald, J., Kelly, J.J. Jr., The Effect of Oral Protein and Glucose Feeding on Splanchinic Blood Flow and Oxygen Utilization in Normal Cirrhotic Subjects. J. Clinics Invest. ~:1017, 1955 Celander, 0., Blood Flow in the Foot and Calf of the Newborn. Acta Paed. Scand, 12:480-488, 1960 Celander, 0., studies of Peripheral Circulation. D.E. Cassels Edition. The Heart and Circulation in the Newborn and Infant. 98-110,.1966 Chinn, P.L., Infant Gavage Feeding, American Journal of Nursing. 21:10, October 1971 Dweck, H. S., Reynolds, D.W., Cassady, G., Indirect Blood Pressure Measurement in Newborns, American Journal Diseases of Children, 127:492:494, April 1974 Feather, E., Russell, G., Respiratory Mechanics in Infants of Low Birth Weight and the Effects of Feeding. Biology Neonate, 24:117-127, 1974 32 Kidd, L., Sevison, H., Gemmel, P., Aharom, A., Swyer, P.R., Limb Blood Flow in the Normal and Sick Newborn, American Journal Disease of Children, 112:402-407, November 1966 Kleinberg, F., Newman. L.L., Long, L., Phibbs, R.H., Iisplacement Plethysmograph To Measure Limb Blood Flow in the Newborn Infant, Mayo.Clin.Proc. ..ih:430432, July 1976 t Reininger, E.J., & Saperstein L.A., Effects of Digestion on Distribution of Blood Flow in the Rat, Science, 126:1176, 1957 Riley, I. D., Hane and Forearm Blood Flow in Full Term and Premature Infants, Clinical Science, 11:317 1954 Smallpeice, v., & Davies P.A., Immediate Feedings of Premature Infants with Undiluted Breast Milk. Lancet, ii:1349-1J52, 1964 Wallgren, G., Lind, J., Quantitative StUdies of the Human Neonatal Circulation. Acta. Paed, Scand. (Supple. 179) 22: 4 3, 1967 Whitney, R.J., Measurement of Changes in Human Limb Volume by Means of A Mercury-in-rubber Strain Gauge, Journal Physiology, 102:5-5, 1949 ~Vhi tney, R. J ., The Measurement of Volume Change s in Human Limbs, Journal Physiology. 121:1-27, 195J iJ'Jong, W. H., Wu, P.Y.K., Kafka, H., Freedman, R.I., Levan, N.E., Blood Flow and Venous Distensibility in the Upper and Lower Extremities of Newborn Infants Acta Paediatric Scand, 65:571-575, 1976 Yao, A., Wallgren, G., Sinha, S.N., Line, J. Feeding in Newborn Infants, Pediatrics, 1971 t Response to ~:378-J8J, Yu, V.Y.H., Cardiorespiratory Response to Feeding in Newborn Infants, Archives of Disease in Childhood, .il:-)05-J09, 1976 33 PERI PHERAL BLOOD FLOW TRAC I NG DURING FEEDING. OCCLUSIO N t 10 see t BEFORE t OCCLUSION 10see t AFTER DEMONSTRATION OF TRACING I'N INFANTS FOLLOW I NG OCCLUS ION OF VENOUS RETURN. APPENDIX No.1 34 APPENDIX 2 DATA SHEET Infant Data Collection Sheet I. Name VI ~ Age II. Date VII. Sex I. IV. lllJeight VIII. Hospital # IX. Birth Date Feeding Factors Measured at Intervals Time H.R. R.R. B.P. Tem12 .. Baby I Corn..ment . *Abbreviations:H.R. B.P. Temp = Heart = Blood Respiratory Rate, R.R. Pressure~ Temperature I = Isolette,'