The response of infants to a large dose of water

Fluid therapy in paediatric trauma

Trauma is the most common cause of death in children over one year of age. Hypovolaemic shock is a life-threatening consequence following trauma. Hypovolaemia may be difficult to identify in children, with hypotension being a late and critical sign. Delayed capillary refill time is a useful clinical adjunct to identify hypovolaemic shock in children. This article reviews paediatric and neonatal maintenance and resuscitation fluid requirements. Fluid therapy is addressed in specific trauma circumstances including head injury, burns, and near drowning. Methods of gaining circulatory access and complications of fluid therapy are also discussed.

Developmental changes in renal tubular transport-an overview

The adult kidney maintains a constant volume and composition of extracellular fluid despite changes in water and salt intake. The neonate is born with a kidney that has a small fraction of the glomerular filtration rate of the adult and immature tubules that function at a lower capacity than that of the mature animal. Nonetheless, the neonate is also able to maintain a constant extracellular fluid volume and composition. Postnatal renal tubular development was once thought to be due to an increase in the transporter abundance to meet the developmental increase in glomerular filtration rate. However, postnatal renal development of each nephron segment is quite complex. There are isoform changes of several transporters as well as developmental changes in signal transduction that affect the capacity of renal tubules to reabsorb solutes and water. This review will discuss neonatal tubular function with an emphasis on the differences that have been found between the neonate and adult. We will also discuss some of the factors that are responsible for the maturational changes in tubular transport that occur during postnatal renal development.

Postnatal developmental renal physiology: a study of historic significance

This essay looks at the historic significance of an APS classic paper ( http://www.the-aps.org/publications/classics/ ) that is freely available online:

Falk G. Maturation of renal function in infant rats. Am J Physiol 181: 157–170, 1955 ( http://ajplegacy.physiology.org/cgi/reprint/181/1/157 ).

Management of fluid balance in the very immature neonate

Preterm birth requires rapid adaptation from a liquid to a gaseous, low humidity environment. There are several ways in which this can be facilitated. The management of sodium and water balance is considered here.

Clinical implications of postnatal alterations in body water distribution

Substantial alterations take place in the quantity and distribution of body water compartments after birth. Clinical management must be tailored to the pace of postnatal adaptation, and the neonatal physician must be aware of these alterations in order to promote both normal physiological change and growth.

Imaging the kidneys and urinary tract in the neonate with acute renal failure

Transitional nephrology seriously affects the manner in which radiological investigations and other forms of imaging are undertaken in the neonate. When this is complicated by acute renal failure then caution must be exerted in taking care of the neonate. The use of ultrasound and micturating cystourethrography are well described and form the baseline for all imaging of the renal tract. The physiological handling of TC99m DTPA and the contrasts used for IVU are described as well as the normal appearances of these techniques in the neonate. TC99m DMSA is also included, as are other modalities of imaging.

Effect of varying water intake on renal function in healthy preterm babies

Renal control of water and electrolyte homeostasis was studied in 10 healthy babies (gestation 29 to 34 weeks; birthweight 1.19 to 2.19 kg) while water intake was varied. Glomerular filtration rate and urine flow were estimated daily from spot plasma and urine samples for six days using a constant inulin infusion, and simultaneous sodium, potassium, osmolar, and free water clearances were calculated. The infusion was started at an average age of 14 hours. Each baby received a total fluid intake of 96 ml/kg daily on study days 1, 2, and 5, and about 200 ml/kg on study days 3, 4, and 6. Daily sodium intake was kept constant at 3 mmol/kg. At the end of the first study day the babies were undergoing a diuresis, but thereafter their estimated daily water balances remained stable regardless of intake. Glomerular filtration remained stable; alterations in urine flow reflected a change in the percentage of filtrate excreted. Plasma electrolytes and osmolality were stable throughout, and on study days 2 to 6 the urinary excretion rates of sodium, potassium, and other osmoles remained the same regardless of urine flow. The delivery of sodium to the distal tubule was estimated to be between 17 and 20% of the filtered load. Well preterm babies can cope with daily water intakes between 96 and 200 ml/kg from the third day of life.

Diagnosis, treatment, and follow-up of neonatal mepivacaine intoxication secondary to paracervical and pudendal blocks during labor

Seven infants developed mepivacaine intoxication secondary to accidental injection during paracervical or pudental blocks or both. All presented with unexplained neonatal depression at birth, tonic seizures (often with apnea) within six hours, and characteristic neurologic findings. Twenty-four-hour urinary excretion produced 12.7 to 37.4 mg, exchange transfusions less than 1.02 to 3.5 mg, and gastric drainage or lavage or both 0.63 to 1.26 mg of mepivacaine. Thus promotion of urinary excretion is the treatment of choice. All six survivors are seizure free and neurologically and developmentally normal at one to 4 1/2 years. With early diagnosis and prevention of severe perinatal hypoxia, the prognosis from intoxication alone is very good.

The effects of large volume intravenous fluid infusion on neonatal renal function

Twenty healthy infants weighing less than 2,000 gm were studied at low (3.6 ml/kg/hr) or high (10.3 ml/kg/hr) rates of intravenous infusion. Inulin clearance determined by the constant infusion method was greater at the high rate of infusion (p = less than 0.05). Inulin clearance in two groups of infants over 2,000 gm studies at the same low or high rates of infusion did not increase at the higher rate of infusion. Since the GFR in infants less than 2,000 gm depends partially on the rate of intravenous infusion, small, healthy preterm infants may benefit from a rate of fluid administration greater than the low rate. When studies at low and high rates of infusion were compared in the 20 infants less than 2,000 gm, the fractional urinary sodium excretion increased with the increased fluid load. Delivery of fluid from the proximal tubule (CH2O =Na per dl GFR) increased (p less than 0.005). Free-water clearance and the absolute volume of urine increased at the high rate of infusion. These data indicate that the healthy preterm infant less than 2,000 gm, like the adult, compensates by increasing free-water clearance and urine volume when challenged with a large fluid load. Although fluid changes of short duration are appropriately handled, the effect of continuous rapid infusion on water and sodium balance in infants of this size remains to be determined.

Renal physiology in children

The human kidney may not reach functional maturity until the age of 18 months. In the preceding months there are limitations in response to such stresses as salt and water loading, acidosis and dehydration. It is seen that these limitations must not be taken out of context of the overall situation of health or disease and of actual solute load. Almost all drug dosages for children are calculated on the basis of body size, and it should be recalled that in the first months of life there exists relative renal insufficiency on the basis of body weight or surface area in comparison with older children and adults.

Precise physiologic data are necessary for completely successful management of the critically ill patient. It is seen from this review that not only are there gaps in our knowledge of developmental renal physiology, but also the process of development has introduced another variable into the evaluation of the individual patient.

Action potentials of the pyramidal neurones in the hippocampus of the rabbit

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