Rex Baker

Acute effects of albumin infusion on blood volume and renal function in premature infants with respiratory distress syndrome

The purpose of this study was to determine the acute effects of albumin infusion on blood volume and renal function in preterm infants with RDS and low total serum protein values. Ten infants (gestational age 28 to 36 weeks, body weight 0.88 to 2.46 kg) were given albumin 1 gm/kg (as 25% iv solution) over a ten-minute period. Within ten minutes after infusion was completed, total serum protein concentration, colloid osmotic pressure, and blood volume rose significantly while hematocrit fell from their preinfusion levels (P < 0.0005). Mean arterial blood pressure showed a smaller and less clear-cut increase (P < 0.05). Creatinine clearance rose significantly with infusion; even though preinfusion clearances correlated poorly with gestational age (r = 0.43), postinfusion clearances correlated well (r = 0.92). No significant rises in urinary flow rate Uosm/Posm, or free-water clearance were observed. These results indicate that albumin infusion acutely increases both blood volume and glomerular filtration in premature infants with RDS.

Renal Tissue Oxygenation During Hypoxic Hypoxia

No evidence was found to support the existence of changes in the intrarenal flow pattern among the different areas or of a compensatory redistribution of microcirculation in the renal cortex under hypoxia induced by breathing 10 % oxygen. It seems that under these conditions the kidney is able to preserve its basic metabolism by diminishing its oxygen consumption.

Erythropoietin and Intrarenal Oxygenation in Hypercapnic Versus Normocapnic Hypoxemia

That the kidney plays the major role in production or activation of erythropoietin (Ep) in adult mammals has been well established through a variety of methods (Krantz and Jacobson, 1970). Although a decrease in intrarenal tissue O2 availability (AO2) has been suggested as the stimulus for Ep production, no measurements of this parameter in Ep studies have been done to date.

Effect of Norepinephrine and Angiotensin II on Intrarenal Oxygen Availability

Oxygen availability (O2a) in the cortex, outer medulla, inner medulla, and papilla of the left kidney was measured in 12 unanesthetized rabbits implanted with O2 sensitive electrodes. Each was injected with a single i.v. bolus of either norepinephrine (NE) or angiotensin II (AII) in equipressor doses, and intrarenal O2a was continuously recorded. The NE response consisted of parallel and proportional intrarenal O2a decreases and overshoots in all zones; AII response consisted of progressively smaller O2a decreases from outer to inner zones during maximum response and smaller increases during maximum overshoot. These response differences may be important under various physiologic or pathologic conditions.

Sickle Cell Nephropathy

The pathophysiology of sickle cell nephropathy is still unclear (1,2); until recently, even the histopathology, electronmicroscopy and immunofluorescence microscopy were uncertain (3,4). Therefore, means of prevention and effective treatment have not yet been established. This paper reviews the data of various experimental studies, mainly ours, and relates them to findings already reported in patients with sickle cell disease and trait. Finally, a hypothesis will be advanced for a pathophysiological explanation of sickle cell nephropathy, and based on this, a rational approach to prevention, identification, and treatment will be presented.

1083 EFFECT OF ALBUMIN ADMINISTRATION ON RENAL FUNCTION IN PREMATURE INFANTS

This study was done to determine effect of salt-poor albumin on blood volume (BV) and renal function in ten premature infants (GA 28-36 weeks, body weight 1.43 ± 0.15 SE kg) with total serum protein (TSP) < 4.5 g/dl. They were given 1 g/kg albumin as 25% salt-poor solution iv in 5-10 min. Urine was obtained in a bag applied to the infant; the bladder was creded after each voiding and when collection periods ended. Initial BV was measured using Evans blue; changes over a 40-min period were estimated from changes in hematocrit (Hct). Mean arterial blood pressure (MABP) was continuously monitored through an umbilical arterial catheter. Serum and urine osmolarities and creatinines, TSP, colloid osmotic pressure (COP), BV, and MABP were measured and creatinine clearance (CCr) calculated before and after albumin infusion. An increase in BV from 88 ± 5 to 100 ± 8 ml/kg (P<.0005) was first observed 10 min after infusion and then remained unchanged during the study; this was paralleled by increases in TSP from 4.4 ± 0.1 to 4.8 ± 0.1 g/dl (P<.0005) and COP from 20 ± 1 to 25 ± 1 cm H2O (P<.0005). However, MABP was not significantly changed. There was an increase in CCr from .42 ± .09 to .89 ± .17 ml/min (P< .0005), but CH2O and Uosm/Posm did not significantly change. Apparently, observed changes in MABP, BV, and Hct had a greater influence in increasing GFR than increases in COP had in decreasing it. In conclusion, albumin infusion may help improve GFR in hypoproteinemic premature infants.

Relationship between Erythropoietin Levels and Intrarenal Oxygenation during Anuric Hemorrhagic Shock

It has been shown that the kidney plays a major role in the production (Jacobson and Krantz, 1970) and perhaps inactivation (Fisher et al, 1968a) of erythropoietin (erythropoietic stimulating factor, ESF). Although most investigators believe that the renal cortex is the site controlling ESF production (Jacobson and Krantz, 1970), the evidence is not conclusive. Increase in ESF levels has been observed under a variety of stimuli including production of renal infarcts (Abbrect et al, 1966), constriction of the renal artery (Fisher et al, 1968b; Fisher and Samuels, 1967), infusion of vasopressors (Fisher et al, 1968b), hypoxic hypoxia (Murphy et al, 1971), and normovolemic anemia (Naets, 1959). However, this increase is not always present after renal arterial constriction (Murphy et al, 1967a) and hemorrhage (Murphy et al, 1967b). In addition, tissue oxygenation measurements have brought further questions about the relationship between hypoxia and ESF production (Hardwick et al, 1963). The present study was undertaken to evaluate the relationship between intrarenal oxygen availability (O2a) and consumption (VO2) and serum ESF levels during anuric hemorrhagic shock in rabbits.

EFFECT OF VASOPRESSORS AND HEMORRHAGE ON INTRARENAL OXYGENATION

Hemorrhagic hypotension has been reported to be accompanied by liberation of catecholamines (1) and angiotensin (2). Aukland observed parallel blood flow decreases in cortex and outer medulla during hemorrhage and the injection of various vasopressor agents (3). From these data he suggested that vasopressors may be largely responsible for the increased renal vascular resistance of hemorrhagic hypotension. On the other hand, Rector et al. (4) observed intracortical blood flow redistribution during hemorrhage, but none during norepinephrine or angiotensin infusion. This suggested that the observed hemorrhagic intrarenal redistribution was due to factors other than humoral release of either norepinephrine or angiotensin. Grandchamp et al. (5) have suggested that the simultaneous action of both norepinephrine and local angiotensin are needed to produce the intrarenal blood flow redistribution of hemorrhagic hypotension.

Local and Whole Organ Renal Oxygenation under Hemorrhagic Shock

Reports of various authors on the use of different techniques for assessing tissue oxygenation under a variety of hemorrhagic shock conditions abound in this symposium and in the literature (1,2). Undoubtedly these add to our knowledge of this exciting and complex clinical and experimental state. Our hope is that coordinated efforts will be undertaken to compare techniques and experimental designs and thus facilitate interpretation of results. In this way the role played by anesthesia, surgical trauma, temperature, and degree and duration of shock, among other variables, can be evaluated. In addition, changes in results due to changes in size, location, and type of electrodes as well as duration and type of polarographic voltage can be identified. This report is about one of our attempts in this direction: the comparison of local renal oxygenation changes with those of the whole kidney under hemorrhagic shock.

Measurement of Oxygen in the Newborn

Numerous conditions endanger the life or the health of the newborn baby apparently through decreased or increased oxygen supply to various organs. Shortly after birth cardio-respiratory embarrassment leads to hypoxia and creates the need for increased oxygen concentration in the inspired gas (FIO2). Subsequently, as the baby improves, the need to regulate oxygen intake persists mainly because of the detrimental effects of high oxygen in the environment or in the blood and the dependency on external support of respiration.