base homeostasis in the newborn child

Effects of Major Surgery on the Acid/Base Homeostasis in the Newborn Child H. C. BORRESEN AND O. KNUTRUD INTRODUCTION

H E E F F E C T S O F major surgery on w a t e r and electrolyte metabolism as well as on the nitrogen balance in the n e w b o r n infant has b e e n the subject of a previous study from this hospital3 A slight postoperative decrease of the average blood p H was found, b u t a resolution of this aeidemia into metabolic and respiratory components was omitted. The purpose of the present study is to establish the "normal" effects of major surgery on the a c i d / b a s e status of n e w b o r n infants, in order to provide a b a c k g r o u n d for the evaluation of complicating a c i d / b a s e disturbances. Of particular relevance to the present p a p e r is the work of Rogner and Frenzel, 2 in which they pointed out that in the first w e e k of life a c i d / b a s e equilibrium is normally established through a series of oscillations of the a c i d / b a s e p a r a m e t e r s from day to day in the same individual, due to sequences of regulation and counterregulation. Such oscillations contribute to the widening of the normal ranges of the a c i d / b a s e parameters in infants as c o m p a r e d to adults. Young has recently presented a lucid discussion of neonatal a c i d / b a s e disturbances, 3 in which he emphasizes that the causes of such disturbances should be diagnosed and treated rather than directing fluid treatment primarily against the symptomatic changes in p H and base excess ( B E ) or standard bicarbonate.

T

MATEI~IALS AND METHODS

The control material consists of 10 normal healthy children, born to healthy mothers with uncomplicated delivery. There was no intake on the day of birth. Later on they were fed breast milk, the amounts increasing from 50 ml. on the second day to 400 ml. on the sixth day of life. Blood samples for examination of the acid/base status were taken within one hour after birth, and on the following days in the morning. The postoperative material consists of 16 newborn children admitted to the Paediatric Service of the Rikshospital, Oslo, for operative treatment of congenital anomalies endangering life. Infants selected at random who underwent such surgery within an 11 month period were included in this investigation to obtain a material of the same type as analyzed previously by Knutrud. 1 Thirteen of the children were operated upon during the first 5 days of life and all of them in the first week. Sixteen infants were operated for the following congenital lesions: 6, esophageal atresia; 2, duodenal atresia; 3, ileal atresia; 1, ileal fishda; 2, exomphalos; 1, biliary atresia with perforation; 1, Hirschsprung's disease. Two of the From the Institute of- Clinical Biochemistry and The Pediatric Surgical Service, University Clinic, Rikshospitalet, Universit~ of Oslo, Oslo, Norway. H. C. BORBESEN, M.D.: Research Fellow of the Norwegian Cancer Society, Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Oslo, Norway. 0. KNUTRUD, M.D.: Chief, Pediatric Surgical Departement, Rikshospitalet, Oslo, Norway; Dr. reed., University of Oslo, Oslo, Norway. 493

JOURNALOF PEDIATRICSURGERY,VOL, 2, No. 6 (DECEMBER), 1967

494

BORBESEN AND KNUTttUD

Born

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Fig. 1.--Acid/base parameters of the control material. The means are indicated by horizontal bars. Vertical bars cover the ranges mean ---2 standard deviations. patients were slightly premature with birth weights of 2.200 Gin. The others were fullborn with birth weights between 2.500 Gm. and 3.800 Gin. All the infants were operated upon under general anesthesia (Fluothane/NzO) with tracheal intubation. The body weight, food intake, diuresis and aspirate were measured daily, as were the serum electrolytes. Blood samples for the examinations of acid/base status were taken from a heel stab preoperatively, shortly after the operation and then on the following days up to the ninth postoperative day. The blood loss during operation was replaced and the patients were given 5 per cent glucose intravenously during the first 2-3 days after the operation, normally between 50 and 100 ml. per day, until breast milk feeding could be started. In some patients 50 ml. plasma was given daily in addition to the 5 per cent glucose because oral feeding had to be delayed more than the usual 2-3 days. Methods. Standard bicarbonate (or base excess), pCO_~ and pH were determined with the micro-Astrup technique? By definition the base excess (BE) is zero for blood which has a pH of 7.40 after equilibration with an atmosphere with oCO_~of 40 mm. Hg. RESULTS AND DISCUSSION

Control Material Figure 1 shows that the slight metabolic acidosis observed a few hours after birth (average BE about - 5 m E q . / L . ) gradually subsides, the base excess being on the average - 2 m E q . / L by the end of the first week. The average pCO2 was close to 40 ram. H g except for the first day where the high pCO2 values of two patients increased the average to 47 ram. Hg. These findings are similar to the data reported by Rogner and Frenzel.'-' Figure 1 further demonstrates, however, that the spread of the normal acid/base parameters was so large that average values cannot be very informative as to the course to be expected for normal infants from day to day. The standard deviations observed are shown in Table 1. The data

495

EFFECTS OF M A J O R SURGERY ON ACID/BASE HOMEOSTASIS

Table 1.--Standard Deviations of Acid/Base Parameters.

The table is arranged to allow comparison of the average standard deviation of pH, pCO e and standard bicarbonate of normal controls and of operated infants. Data on adults (means of males and females) are taken from Siggaard-Andersen. 5 Standard Deviation

Postoperative material Control material Normal newborn infants (Rogner and Frenzel2) Adults

Standard bicarbonate, mEq./1.

pI-I

pCO2, mm. Hg.

0.049 0.047

7.1 7.8

3.03 1.4

0.039 0.015

6.2 2.75

2.2 0.9

of Rogner and Frenzel 2 obtained from a larger, but similar material, as well as the values given by Siggaard-Andersen5 for adults, are included in the table for eomparison, The agreement between our results and the data of Rogner and Frenzel is satisfactory. It is evident that the level of respiratory activity, as expressed through pCO2, is considerably more variable in infants than in adults. The variability of the BE value is also larger in infants than in adults, the standard deviation being about twice as great in the former group. The comparatively large spread in acid/base parameters in our material was due both to oscillations, from day to day, of the values of individual patients, and to differences in the average levels of different patients. Such oscillations were not, however, exhibited by all individuals, and when observed the periods of the oseillations were irregular. The possible occurrence of more regular oscillations in a shorter period than 48 hours was not investigated. Our results indicate that it is not abnormal for a child to remain at one end of the normal range of one or more aeid/base parameters for several days. Postoperative Material

The two patients who suffered from duodenal atresia were excluded from the calculations of "normal" postoperative averages and ranges because they were expected to exhibit not only the usual acid/base disturbances due to the operation and starvation, but also a component of metabolic alkalosis due to loss of gastric contents. Figure 2 shows that the effects of operation on the average values of the acid/base parameters were small compared to the ranges of the control material. The slight metabolic acidosis before and in the first few days after the operation was followed by a slight tendency to metabolic alkalosis in the last half of the first postoperative week. Presumably this increase in average standard bicarbonate reflects the combined effect of two mechanisms: First, any pre-existing hunger acidosis would tend to disappear 2-4 days after the operation due to the increased intake of food and fluids; secondly, the average postoperative loss of about 5 per cent of the total body potassium 1 probably leads to a slight

496

BORRESEN AND KNUTRUD Oper(ation

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Fig. 2.--Acid/base parameters of the postoperative material. Same meaning of symbols as in Fig. 1. Empty circles: duodenal atresia. extracellular metabolic alkalosis. The occurrence of significant increases of pCO2 to compensate for the metabolic alkalosis is difficult to detect due to the wide ranges of pCO2. Table 1 documents that a conspicious effect of operation was to increase the standard deviation of the standard bicarbonate by a factor of about 2 compared to the control material, while pCO~ was not so affected. The course, from day to day, of the acid/base parameters of individual postoperative patients is shown in Figure 3. The plots illustrate that the large postoperative ranges of pCO2 and standard bicarbonate are only partly due to excessive fluctuations from time to time in individual patients. Hence the material does not justify a conclusion to the effect that it would be definitely abnormal for the acid/base parameters of a patient to remain at one border of the normal range for two or more consecutive days.

Acid/Base Disturbance Associated With Duodenal Atresia. The two patients with duodenal atresia are illustrated in Fig. 2 (nonfilled circles) and Fig. 3 (No. 2 and 6). Both patients had somewhat elevated values of standard bicarbonate in the first two days following the operations. This alkalosis was slight, i.e., with standard bicarbonate close to the borderline between the "normal" and abnormal postoperative ranges, presumably because the infants were operated early (3 and 6 days old). The more profound metabolic alkalosis due to duodenal atresia (BE z q- 17 mEq./L.) reported by Young3 occurred in a 14 day old infant prior to operation. Figures 2 and 3 show that the standard bicarbonate of our two patients slowly approached the mean of the "normal" postoperative group during the first postoperative week. This approach took place not because the standard bicarbonate of the two patients decreased, but rather because the mean standard bicarbonate of the "normal" postoperative group increased.

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Ranges of Acid/Base Parameters in the Postoperative Period In the newborn infant values of standard bicarbonate between about 15 and 27 mEq./L, or base excess between -12 and + 4 mEq./L, must be accepted as "normal" in the sense that such values are frequently found in the absence of other pathological processes than the operation itself and the associated starvation, and that such values are compatible with a favorable postoperative course. The meaning of these ranges is that the standard bicarbonate or BE must be outside them before a complicating specific acid/ base disturbance, e.g., metabolic alkalosis due to vomiting, can be diagnosed with reasonable certainty. It should be appreciated, however, that values of standard bicarbonate or BE inside the above ranges do not preclude the occurrence of abnormal processes leading to acid/base disturbances of mild degree. The capillary pCO2 of infants operated in the first two weeks of life, must be outside the range 20-60 mm. Hg before it can be accepted as definitely abnormal. The same limits appear to be valid for nonoperated normal infants as well.

Diagnostic and Therapeutic Implications Due to the wide ranges and the occasional oscillations of acid/base parameters occurring normally in operated infants with uncomplicated recovery, the diagnosis of moderate acid/base disturbances is difficult, even if data

498

t3ORRESEN A N D K N U T R U D

from several consecutive days are considered. The wide ranges are particularly useful, however, as they discourage unnecessary corrections of the acid/base status of infants. It should be appreciated, though, that the normal, favorable postoperative courses stated above to b e compatible with rather wide ranges of acid/base parameters, do not imply that the treatment and recovery of these infants were optimal. It may well be that more adequate nutrition in the immediate postoperative period would influence the recovery favorably and reduce the incidence a n d / o r seriousness of complications. Thus it is possible that intravenous feeding with calories, amino acids, vitamins and minerals in adequate amounts will necessitate the investigation of "optimal" ranges of acid/base parameters in the postoperative phase rather than the "usual" ranges described in this paper. SUMMARIO IN INTERLINGUA Parametros de aeido e base esseva studiate in infantes subjicite a interventiones chirurgie durante le prime septimana del vita. A1 media, un leve acidosis metabolic esseva eonstatate, con un mareate extension del variabilitate del concentrationes del electrolytos post le operation. A causa del extense gamma de valores e del non infrequente oscillationes ab un die al proxime, 94 diagnose de moderate disturbationes del balancia acido-base es difficile. Tamen, lo hic-notate extense gammas de valores es utile in tanto que illos representa un potente argumento contra le effeetuafion de non-necessari correctiones del stato aeido-base in infantes subjicite a operationes ehirurgie. REFERENCES

1. Knutrud, O.: The Water and Electrolyte Metabolism in the Newborn Child after Major Surgery. Universitetsforlaget, Oslo, 1965. 2. Rogner, G., and Frenzel, J.: Kinderheilk. 97:39, 1966. 3. Young, D. G.: Arch. Dis. Childh. 41:

201 (1966). 4. Siggaard-Andersen, O., Engel, K., Jorgensen, K., and Astrup, P.: Scand. J. Clin. lab. Invest. 12:172, 1960. 5. Siggaard-Andersen, O.: The Acid-Base Status of the Blood. Munksgaard, Copenhagen, 1964, p. 28.