This thesis describes an observational study of renal
function in preterm babies. During the course of the study
no attempt was made to manipulate clinical conditions. The
study was performed in three parts.The principal portion of the work was an observation
of renal function during the first week of life, in a group
of infants between 25 -34 weeks gestation, who required
intensive care; the influence of gestational age, postnatal
age, birth weight and respiratory adaptation were explored.
Comparison is made with published parameters of renal
function derived from healthy preterm neonates.Glomerular filtration rate was assessed as endogenous
creatinine clearance during prolonged urine collection. No
increase in glomerular filtration rate was shown between
days 2 -7 of life. The population of infants studied here,
who required intensive care, showed little difference from
published parameters of glomerular filtration rate measured
in healthy preterms.Creatinine excretion rate was used to derive a regression equation predicting muscle mass from weight and
gestational age. Muscle mass was found to increase from 12%
of birth weight at 25 weeks gestation to 19% at 34 weeks
5
and 24% at 40 weeks. This is in agreement with classic
dissection studies which have shown muscle mass to be 25%
of body weight at term.Changes in urine flow rate, urine osmolality and
sodium balance were studied. The influence of respiratory
adaptation on various parameters of renal function and
particularly on sodium handling was investigated. Positive
sodium retention was seen in babies with respiratory
disease; sodium retention changed to sodium loss at a point
coinciding with improvement in respiratory function. The
diuresis that accompanied the improvement in respiratory
function, in infants with hyaline membrane disease, was
characterised as a natriuresis, with increased creatinine
clearance and osmolar clearance but unchanged free water
clearance.Renal function was compared during periods of
hyperglycaemia and normoglycaemia. The degree of
hyperglycaemia observed did not result in an osmotic
diuresis but was associated with a significant decrease in
fractional sodium excretion and urinary sodium loss.The second part of the study determined the incidence,
aetiology, diagnostic indices and outcome of acute renal
failure in a series of 388 consecutive admissions. The
incidence in this tertiary referral centre was found to be
6
6.2 %. The difficulties involved in making an accurate
diagnosis of acute renal failure are examined.In the third part of this work serum
beta -2- microglobulin was studied in a group of 'well'
preterm babies and its value as an index of glomerular
filtration rate assessed
