Postnatal Weight Loss in Preterm Neonates <1500 g is Due to Isotonic Dehydration of the Extracellular Volume

Bauer, K. and Versmold, H. (Division of Neonatology, Department of Obstetrics and Gynecology, University of Munich, Munich, FRG). Postnatal weight loss in preterm neonates < 1 500 g is due to isotonic dehydration of the extracellular volume. Acta Paediatr Scand Suppl 360: 37, 1989.
Weight, extracellular volume (ECV, distribution volume of sucrose) and renal function were studied in 13 preterm infants at birth (age 6 h (2–12); median, range) and again when postnatal weight loss exceeded 5% of birth weight (age 84 (64–97) h). Gestational age was 28 (26–32) weeks, and birthweight was 1170 g (810–1455). The infants were nursed in incubators and mechanically ventilated. Fluid therapy allowed a weight loss of up to 10% of birthweight. Body weight decreased significantly from 1101 ± 2202g at birth to 1016 ± 2198 g at day 3 and ECV from 499 ± 155 ml to 413 ± 118 ml. Mean weight loss of 85 ± 50g was the same as mean ECV loss of 86 ± 48 ml, suggesting that postnatal weight loss is water loss from the ECV. Weight loss was preceeded by a marked increase in diuresis, exceeding fluid intake on day 2. Creatinine clearance did not change. The increased urine output led to a significant increase of sodium excretion without inducing hyponatremia but resulted in an isotonic reduction of ECV.     

小剂量多巴胺联用酚妥拉明治疗原发性肾病综合征患儿水肿的临床研究

目的 探讨小剂量多巴胺联用等量酚妥拉明对原发性肾病综合征(PNS)患儿水肿的疗效及安全性.方法 采取回顾性对照研究的方法.在常规综合治疗的基础上,对155例PNS并发水肿患儿(联用治疗组)给予小剂量多巴胺联用等量酚妥拉明治疗,并与128例单用呋塞米患儿(呋塞米治疗组)对照.结果 联用治疗组治疗后尿量、尿钠均高于治疗前,差异有显著性(P＜0.01),而血钾、血钠及尿钾虽高于治疗前,但差异无显著性(P＞0.05).呋塞米治疗组治疗后尿量、尿钾、尿钠均高于治疗前,差异有显著性(P＜0.01),而血钾、血钠均低于治疗前,差异有显著性(P＜0.01).联用治疗组治疗后水肿减轻率、尿量、尿钠、血钾及血钠均高于呋塞米治疗组,差异有显著性(P＜0.01);而尿钾低于呋塞米治疗组,差异有显著性(P＜0.05).治疗后药物不良反应发生率方面,联用治疗组低于呋塞米治疗组,差异有显著性(P＜0.01).结论 小剂量多巴胺联用等量酚妥拉明治疗小儿PNS水肿安全、有效,适用于不同血容量状态的患儿,可替代呋塞米等利尿剂作为一线用药.

Abstract：

Objective To explore the efficacy and safety of low dose dopamine combined with phentolamine in the treatment of primary nephrotic syndrome (PNS) with edema. Methods Retrospective control studies were performed in 155 patients of PNS with edema, who received comprehensive treatment with small dose dopamine combined with phentolamine (group A). Patients treated with furosemide infusion were recruited as control (group B). Results The urinary output, urinary sodium increased after therapy in group A, showing significant differences (P ＜ 0. 01). But urinary potassium excretion, serum sodium and potassium showed no significant difference after therapy in group A. The urinary output, urinary sodium and potassium excretion increased and the serum sodium and potassium decreased after therapy in group B, all showing significant differences between before and after treatment (P ＜0. 01). The edema relief rate,urinary output, urinary sodium excretion, serum sodium and potassium in group A was significantly higher whereas urinary potassium excretion were significantly lower than those of group B(P ＜0. 01). The rate of drug adverse reaction in group A was significantly lower than that of group B. Conclusion Low dose dopamine combined with phentolamine in PNS with edema is safe and effective,which may be a substitute of diuretic like furosemide in the treatment of edema of patients with different blood volume.     

Atrial natriuretic peptide in the preterm infant. Lack of correlation with natriuresis and diuresis

We assessed the relation of atrial natriuretic peptide (ANP) to renal function on postnatal day 2 and day 5 in preterm infants. Plasma ANP concentration was measured by radioimmunoassay in two groups of preterm infants: group 1, gestational age less than 30 weeks, n = 10; and group 2, gestational age 30-34 weeks, n = 11. The identity of the immunoreactivity as ANP-28 was confirmed by HPLC. Plasma ANP was significantly higher in group 1 than in group 2 on day 2 and day 5 (p < 0.01) and ANP concentration decreased by day 5 in both groups (group 1, p < 0.01; group 2, p < 0.02). The results showed no correlation between plasma ANP concentration and urinary sodium excretion or creatinine clearance, which may be due to a blunted renal response to ANP, but other factors may be involved also. We conclude that preterm infants are able to release large amounts of ANP, but a high plasma ANP concentration does not correlate directly with renal regulation of sodium and water balance.     

Blood pressure in the neonate: three non-invasive oscillometric pressure monitors compared with invasively measured blood pressure

AIM: To compare blood pressure in neonates obtained from three different oscillometer blood pressure monitors (Dinamap, Criticare, Hewlett-Packard) with arterial blood pressure (Hewlett-Packard' invasive unit). STUDY DESIGN: A total of 32 randomized, non-invasive blood pressure series, each consisting of three measurements from each monitor, were obtained from 20 neonates (birthweight 531-4660 g). Each measurement was compared with the invasive pressure. RESULTS: Two factors appear to have a systematic effect on the difference between oscillometric and invasive pressure (the measurement deviance): the size of the infant, e.g., the arm circumference, and the monitor system. For small infants, the non-invasively measured value tends to be too high. The deviance is partly reversed for larger infants (dependency on size significant for mean and diastolic pressure, p < 0.001). The difference between monitor systems is clearly significant (p < 0.001). Hewlett-Packard gives the lowest pressure values for all pressures. Thus, Criticare and Dinamap tended to show values too high in the smallest infants, while Hewlett-Packard tended to give values too low in larger infants. Birthweight, present weight and arm circumference affected measurement deviance approximately equally strongly, while factors such as the infant's sex, need of breath support and umbilical or radial arterial line were non-significant. CONCLUSIONS: Blood pressure should preferably be measured invasively in severely ill neonates and preterm infants, being aware of pitfalls with measurements using different oscillometer monitors and the size/arm circumference of the infant.     

Acute Oliguria in Preterm Infants with Hyaline Membrane Disease:

ABSTRACT. Ten premature infants with hyaline membrane disease and with acute oliguria were treated with furosemide or furosemide and dopamine. Furosemide alone did not increase diuresis. Furosemide when combined with dopamine, however, caused significant increases in urine output, sodium excretion, fractional sodium excretion and creatinine clearance. These data suggest that the increase in the sodium excretion was due not only to a reduction in the tubular sodium reabsorption but also to an increase in the glomerular filtration rate. Since in premature neonates the creatinine clearance is not a very precise index of the glomerular filtration rate, the extent of contribution of the increase in the glomerular filtration rate to the enhanced sodium excretion cannot be determined. Despite the increase in the sodium excretion, the serum sodium concentration did not fall significantly. We conclude that the combined treatment with dopamine and furosemide is useful for treating furosemide-resistant, severe functional renal failure in preterm infants with hyaline membrane disease.     

Effect of low-dose dopamine infusion on urinary prostaglandin E2 excretion in sick,preterm infants

In pharmacological doses dopamine (DA) will interact with several endocrine systems and both inhibit (prolactin, thyrotropin) and enhance (renin, angiotensin) hormonal release. In this study we have examined whether DA given to preterm neonates will influence prostaglandin (PG) production. The question is of importance since vasodilatator PGs play a role in postnatal adaptation. We determined the effect of low dose DA infusion on the 24 h urinary PGE₂ excretion rate (an index of renal PGE₂ synthesis) in preterm infants. Six preterm neonates, with a 24-h requirement of 2 g/kg per min DA treatment for oedema, moderate oliguria, poor peripheral perfusion and/or mild systemic hypotension were studied on days 2 (Day 1), 3 (Day 2, the day of DA infusion), and 4 (Day 3, DA discontinued) of life. Six preterm infants (control group) that did not require DA infusion were also studied to monitor possible spontaneous changes in the renal PGE₂ production on days 2, 3 and 4 of life. In the control group urine output (U_v) and PGE₂ excretion rate remained unchanged during the study. In the study group DA administration resulted in nearly two-fold increases in both the U_v (194%) and PGE₂ excretion (182%). Urinary PGE₂ excretion was, however, closely related to urine flow in both the control infants (Day 1–3) and the study group infants (Day 1–2). Since increased diuresis stimulates renal PGE₂ production, our data suggest that the increased PGE₂ excretion on Day 2 in the study group was not due to a direct effect of DA on PGE₂ synthesis. On Day 3, however, urinary PGE₂ excretion in the study group decreased out of proportion to that of the U_v (-66% vs-23%), indicating that discontinuation of the drug infusion directly decreases renal PGE₂ synthesis. In conclusion, the findings of the present study indicate that low dose DA does not directly trigger renal PGE₂ production in the sick preterm infant.Abbreviations DA dopamine - PG prostaglandin - U_v urine output - PGE₂ excr PGE₂ excretion rate - PGE₂ conc PGE₂ concentration - SD standard deviation - U_Na, U_K urinary sodium, potassium excretion     

Preterm male infants need more initial respiratory and circulatory support than female infants

AIM: The aim of this study was to investigate possible gender-related differences in clinical parameters during the first week of life that could explain the higher morbidity and mortality of preterm male infants. METHODS: In total, 130 clinical variables were collected from 236 inborn infants (130 male and 106 female infants) with gestational age (GA) < 29 wk. A subgroup of 175 extremely low birthweight infants (ELBW) < 1000 g (n = 86 males; n = 89 females) was analysed separately. RESULTS: At 6 postnatal h, 60.8% of the male infants needed mechanical ventilation versus 46.2% of the females (p = 0.026). Chronic lung disease (CLD) developed in 36.2% of males versus 9.8% of female infants (p = 0.004). Inotrope support with dopamine was used in more than 50% of the infants; additional inotrope support to dopamine was needed by 19.4% of male and 9.7% of female infants (p = 0.041). The gender-related difference in need for inotrope support was more evident among the ELBW infants; 67.1% of male infants needed inotrope support versus 50.6% of females (p = 0.028). At 12-24 h, male ELBW infants had lower minimum mean arterial blood pressure (mean (SD) 25(4) mmHg vs 28(6) mmHg, p = 0.004)) and lower minimum PaCO2 than females infants (4.3 (1.1) kPa vs 4.7 (0.9) kPa, p = 0.043). CONCLUSIONS: There are early gender-related differences in need for ventilatory and circulatory support that may contribute to the worse long-term outcome in prematurely born male infants.     

Randomized trial comparing dopamine and dobutamine in preterm infants

The aim of this study was to compare the efficacy of two inotropic infusions in treating low BP in preterm neonates. Forty infants with median gestational age 27 weeks (range 23–33) were studied. At trial entry the infants, who all had a systolic BP<40 mmHg despite receiving a colloid infusion, were randomized to receive either a dopamine or dobutamine infusion. The infusions were commenced at a rate of 5 g/kg per min and, if necessary, this was increased over the 3 h study period to 15 g/kg per min. There was no significant difference in the gestational or postnatal age or baseline BP of the 20 infants who received dopamine and those 20 who received dobutamine. Three hours after commencing the infusions, although there was no difference in the rate of inotrope infusion between the two groups, the infants who received dopamine had a significantly higher systolic BP, a median of 39 mmHg (range 30–58) compared to a median of 34 mmHg (range 21–46) in the dobutamine group,P<0.05. In addition, 10 infants who received dopamine, but only 3 who received dobutamine, had a systolic BP>40 mmHg (P<0.05). We conclude that dopamine rather than dobutamine infusion is more efficacious in improving the BP of preterm neonates.     

Changes in cerebral,renal and mesenteric blood flow velocity during continuous and bolus infusion of indomethacin

Vasoconstriction induced by bolus injection of indomethacin reduces organ perfusion and has been related to the well-known side effects of indomethacin given for closure of the patent ductus arteriosus (PDA). The aim of the study was to compare the changes in cerebral, renal and mesenteric blood flow velocities after continuous infusion versus bolus injection of indomethacin for closure of the PDA. Thirty-two preterm infants (range 26-35 wk gestational age) with PDA were randomly assigned to receive the same amount of indomethacin either as three bolus injections (n = 14) or as a continuous infusion (n = 18) over 36 h. Blood flow velocities were measured in the internal carotid, right renal and superior mesenteric arteries at baseline and serially at 10, 30, 60 and 120 min and 12, 24, 36 and 48 h after the start of indomethacin treatment. There were no differences in blood flow velocities between both groups at baseline. During continuous infusion of indomethacin there was no significant change in the cerebral, renal and mesenteric blood flow velocities, whereas the flow velocities in the infants receiving bolus injections decreased significantly during the first 2 h after indomethacin administration in all arteries measured. There was a transient, but significant reduction in urine output after bolus injection of indomethacin. Conclusion: In contrast to bolus injections, decrease of organ blood flow and impairment of urine output do not accompany continuous infusion of indomethacin over 36 h.     

Effect of low-dose dopamine infusion on prolactin and thyrotropin secretion in preterm infants with hyaline membrane disease

The effect of low-dose (2-4 micrograms/kg/min) and long-term (greater than or equal to 46 h) dopamine infusion on serum prolactin and thyrotropin concentrations was investigated in 8 preterm infants with hyaline membrane disease. Dopamine was administered for systemic hypotension and/or for impending renal failure. Serum prolactin decreased from 1,314.5 +/- 422.7 microU/ml to 489.9 +/- 464.1 microU/ml (p less than 0.005), while serum thyrotropin fell from 3.77 +/- 2.27 microU/ml to 1.01 +/- 0.25 microU/ml (p less than 0.025) during dopamine infusion. Our data indicate that exogenous dopamine exerts an inhibitory effect on the secretion of prolactin and thyrotropin even in the sick preterm neonate. The role of prolactin in fetal lung maturation and in regulation of the neonatal tissue water stores is discussed. The results of the present study are also useful in explaining the renal effects of long-term low-dose dopamine infusion in the sick preterm infant.     

Noradrenaline for management of septic shock refractory to fluid loading and dopamine or dobutamine in full-term newborn infants

AIM: To determine the effects of noradrenaline in full-term newborns with refractory septic shock. METHODS: Newborns of >35 weeks' gestation with persistent septic shock, despite adequate fluid resuscitation and high dose of dopamine/dobutamine were eligible. In this prospective observational study, we recorded respiratory and hemodynamic parameters prior to and 3 h after starting noradrenaline infusion. RESULTS: Twenty-two newborns were included (gestational age [GA] 39 +/- 1.7 weeks, birth weight (BW) 3110 +/- 780 g). Before starting noradrenaline, the infants received a mean volume expansion of 31 +/- 15 mL/kg and a mean infusion rate of dopamine of 14 +/- 5 microg/kg/min or dobutamine of 12 +/- 6 microg/kg/min. Three hours after starting noradrenaline (rate 0.5 +/- 0.4 microg/kg/min), the mean arterial blood pressure rose from 36 +/- 5 to 51 +/- 7 mmHg (p < 0.001). Urine output increased from 1 +/- 0.5 to 1.7 +/- 0.4 mL/kg/h (p < 0.05). Blood lactate concentration decreased from 4.8 +/- 2.3 to 3.3 +/- 1.8 mmol/L (p < 0.01). Despite an initial correction of hypotension, four infants died later. CONCLUSION: Noradrenaline was effective in increasing systemic blood pressure. An increase in urine output and a decrease in blood lactate concentration suggest that noradrenaline may have improved cardiac function and tissue perfusion.     

Dopamine versus dobutamine in very low birthweight infants: endocrine effects

OBJECTIVES: To compare the endocrine effects of dopamine and dobutamine in hypotensive very low birthweight (VLBW) infants. DESIGN: Non-blinded randomised prospective trial. SETTING: Level III neonatal intensive care unit. PATIENTS: 35 hypotensive VLBW infants who did not respond to volume loading, assigned to receive dopamine or dobutamine. Measurements: Haemodynamic variables and serum levels of thyroid stimulating hormone (TSH), total thyroxine (T(4)), prolactin (PRL) and growth hormone were assessed during the first 72 h of treatment and the first 72 h after stopping treatment. RESULTS: Demographic and clinical data did not significantly differ between the two groups. Necessary cumulative and mean drug doses and maximum infusion required to normalise blood pressure were significantly higher in the dobutamine than in the dopamine group (p<0.01). Suppression of TSH, T(4) and PRL was observed in dopamine-treated newborns from 12 h of treatment onwards, whereas levels of growth hormone reduced significantly only at 12 h and 36 h of treatment (p<0.01). TSH, T(4) and PRL rebound was observed from the first day onwards after stopping dopamine. Dobutamine administration did not alter the profile of any of the hormones and no rebound was observed after stopping treatment. CONCLUSION: Dopamine and dobutamine both increase the systemic blood pressure, though dopamine is more effective. Dopamine reduces serum levels of TSH, T(4) and PRL in VLBW infants but such suppression is quickly reversed after treatment is stopped. Further research is required to assess if short-term iatrogenic pituitary suppression has longer-term consequences.     

Intraosseous infusion of hypertonic glucose and dopamine

Intraosseous infusion of drugs for resuscitation and of fluids has been advocated as an alternate emergency technique to intravenous infusion. The reliability of intraosseous infusion of many substances has not been established. Glucose and dopamine hydrochloride are two commonly used emergency drugs in pediatric practice that have not been carefully studied when administered into the bone marrow. In an animal model, we compared the response of an intraosseous injection of hypertonic glucose with that of an intravenous injection of hypertonic glucose. Serum glucose measurements following the injection revealed both routes of administration to be effective. A dopamine infusion was then administered through the bone marrow for 20 minutes. A statistically significant rise in blood pressure was observed two minutes after initiation of the infusion. Intraosseous infusion of hypertonic glucose and dopamine is an effective route by which to administer these medications and is potentially useful in emergency situations in which intravascular access is delayed.     

Exercise capacity and blood pressure response in children and adolescents after renal transplantation

Physical working capacity and cardiovascular response to graded exercise on a bicycle ergometer were investigated in 70 children and adolescents (33F, 37M) after renal transplantation. Results of static and dynamic lung function tests were within the normal range in all patients. Systolic blood pressure, heart rate, pulmonary ventilation and oxygen uptake increased with workload and returned to pre-exercise levels after 5 m of rest. During exercise, blood pressure values were within the normal range in almost all patients. The increase in heart rate and respiratory frequency was blunted in patients receiving beta blocking agents. Maximum workloads (Wmax) were 2.00 × 0.48 W/kg in females and 2.38 × 0.54 W/ kg in males, which are 78 × 18% and 84 × 18% of the normal values predicted for age. Maximum oxygen consumption (VO₂max) was 23.2 × 5.8 ml/min/kg in females and 28.3 × 5.8 ml/min/kg in males. Half of the patients had height below the third percentile. For this reason exercise capacity in relation to height is probably a more relevant parameter than age. Using actual height, Wmax was 102 f 20% and 102 f 29%, and VO₂max 74 f 14% and 80 f 18% of predicted values, respectively. We conclude that the adaption of the cardiovascular and respiratory system to graded exercise was influenced by beta blocking agents. Wmax and VO₂max were significantly reduced for age in pediatric patients after renal transplantation. Wmax was normal, but VO₂max was still reduced if corrected for height.     

Studies in Renal Response to Various Protein Intakes in Preterm Infants

ABSTRACT. The renal effects of two diets—breast-milk and breast-milk with extra human protein (7 g/l breast-milk)—were compared in very low birth weight infants with a gestational age of 26 to 30 weeks. When the infants were given the high protein diet for one week the glomerular filtration rate (GFR) increased significantly more than when breast-milk alone was given. Sodium clearance showed a similar increase in proportion to the GFR during the two diets. The high protein diet raised the urine osmolality moderately in all individuals, while the diuresis remained unchanged. The data in the present study indicate that the function of the immature kidney is influenced by the amount of protein in the diet. However, the long-term renal effects in preterm infants maintained on a high protein intake remain unknown.     

Successful thrombolysis by prolonged low-dose alteplase in catheter-directed infusion

Catheter-directed thrombolysis is a sophisticated method in the treatment of thromboembolism with maximum effect on the thrombus and minimal systemic effect. The consequences are enhanced local thrombolysis and a reduction in general bleeding tendency, compared with systemic thrombolysis. At our institution, two children had successful thrombolysis by prolonged continuous catheter-directed low-dose alteplase. The first patient, a boy with Fontan physiology, was successfully treated for a massive pulmonary thromboembolism by catheter-directed very low-dose alteplase for five days. The second patient, who suffered from relapsing nephrotic syndrome, achieved satisfactory thrombolysis of an arterial leg thrombosis after four days of continuous catheter-directed low-dose alteplase.

Conclusion: Although catheter-directed thrombolysis seems to be a valuable method in thrombolytic therapy, there is a lack of evidence-based recommendations concerning dosage, effect of bolus, simultaneous anticoagulation and duration of treatment for children.     

Measurement of Ventilation and Respiratory Mechanics during Continuous Positive Airway Pressure (CPAP) Treatment in Infants

ABSTRACT. A new method has been evaluated for measuring ventilation and lung mechanics in spontaneously breathing infants by means of a face chamber. Airway flow is measured with a pneumotachograph inserted between the face chamber and a stable pressure source. Oesophageal pressure is measured via a water-filled oesophageal catheter. The method is suitable for use in conjunction with continuous positive airway pressure (CPAP) treatment in neonatal intensive care. A flat frequency response curve up to 15 Hz for the two measuring systems (i.e., airway flow and oesophageal pressure), and a time shift between the two respective signals of less than 2 msec are prerequisites for correct evaluation of respiratory mechanics. In preterm infants with chest distortion, the inhomogeneity of pleural pressure affects the significance of resistance and compliance values, as calculated from oesophageal pressure. Supra-diaphragmatic pressure variations reflect the resistive and elastic load on the diaphragm exerted by the lungs and thorax. Thus, oesophageal pressure is still useful in studies of respiratory mechanics in preterm infants.     

Renal functional changes in relation to hemodynamic parameters during exercise test in normoalbuminuric insulin-dependent children

AIM: To examine the relationship between filtration fraction and systemic vasculopathy, in normoalbuminuric insulin-dependent diabetic adolescents. METHODS: We calculated filtration fraction from measured glomerular filtration rate and renal plasma flow during a hypotonic saline perfusion test in 30 normotensive adolescent diabetic patients (9-19 years), with a mean duration of diabetes of 7.4 years. Blood pressure and heart rate were measured in basal conditions, during a 24-h ambulatory monitoring and during a dynamic exercise test on a cycle ergometer and peripheral vascular resistance was calculated. RESULTS: Filtration fraction was increased in the diabetic children compared with controls (30+/-6% vs. 22+/-4%, p<0.001), while renal plasma flow was significantly lower (453+/-133 mL/min/1.73 m2 vs. 593+/-155 mL/min/1.73 m2, p<0.001). Peripheral vascular resistance was significantly higher at peak exercise in diabetic children compared to controls (16.3+/-1.3 mmHg/L min m2 vs. 11.4+/-0.5 mmHg/L min m2, p<0.01). CONCLUSION: These results indicate that in young patients with IDDM, without apparent nephropathy or apparent systemic vasculopathy, filtration fraction is increased, suggesting an increased intraglomerular pressure. The associated reduced decrease of peripheral vascular resistance (increased diastolic blood pressure during exercise) suggests that renal functional abnormalities may be partly explained by a systemic vasculopathy, also present in the kidney.     

Plasma concentration and acute clinical effects of docarpamine,orally active dopamine prodrug,in infants

Currently, there are no data available on the optimal doses and efficacy of docarpamine in infants. In the present study, three doses of docarpamine, 15.0–20.4 (19.0 ± 1.9; mean ± SD) mg/kg per dose every 8 h to 10 infants suffering heart failure. Age and bodyweight were from 1 to 4 (1.4 ± 1) months and 2960–5160 (3350 ± 872) g, respectively. In all infants, plasma concentrations of free dopamine were measured 1, 2 and 3 h after the first administration. Heart rate and systolic blood pressure were examined before and at the same time as the first administration. In seven infants, the 24 h urinary output and urinary excretion of electrolytes and creatinine before and during docarpamine were measured. Peak plasma concentration of free dopamine (ng/mL) was achieved after 1 or 2 h of administration, 0–163.1 (37.9 ± 47.2) and 0–105.0 (37.8 ± 39.3), respectively. The concentration had decreased rapidly by 3 h to 0–34.2 (12.4 ± 11.0). Both heart rate (b.p.m.) and blood pressure (mmHg) tended to increase from 120–154 (140 ± 15) and 56–90 (76 ± 11) to a peak of 124–162 (148 ± 14) and 70–92 (79 ± 8), respectively (P = 0.197, P = 0.289). There were no significant changes in urinary output or excreta. Oral docarpamine of 15–20 mg/kg per dose can achieve plasma free concentrations of dopamine that increase heart rate and systolic blood pressure.     

DEVELOPMENTAL STUDY OF THE RENAL RESPONSE TO AN ORAL SALT LOAD IN PRETERM INFANTS

ABSTRACT. Aperia, A., Broherger, O., Thodenius, K. and Zetterström, R. (Department of Paediatrics, Karolinska Institutet, S:t Göran's Children's Hospital, Stockholm, Sweden). Developmental study of the renal response to an oral salt load in preterm infants. Acta Paediatr Scand 63: 517, 1974.—An evaluation of sodium homeostasis in 44 preterm infants with gestational ages between 29 and 37 weeks has been carried out during the first week after birth and until time of expected term. The natriuretic response to an oral sodium load has been studied in all infants and the GFR (single injection technique of inulin) in 17 infants. The results are compared with those previously found in full-term infants. The natriuretic response was highest and the GFR was lowest in the very preterm neonates. In the very preterm infants the values for sodium excretion and GFR was just about the same at the time of expected term as in full-term newborns. Various explanations for the difference between the very preterm neonates and full-term neonates are discussed. One factor of importance might he the anatomical development. The immature kidney has in comparison to the adult kidney relatively larger glomerular than tubular mass. Extra-uterine life seems to have little influence on the development of GFR as well as on the development of the response to the oral salt load. Thus in the very preterm infants, the postmenstrual rather than the postnatal age should be considered when prescribing fluid, electrolytes and drugs.