paediatric clinical chem Flashcards
what are the common problems of LBW babies
resp distress syndrome (RDS)
retinopathy of prematurity - SE of oxygen toxicity
intraventricular haemorrhage
patent ductus arteriosus
necrotising enterocolitis
what is respiratory distress syndrome
breathing problem
common less than 34wks
lack surfactant
rx of RDS
surfactant
oxygen
mechanical ventilation
what is intraventricular haemorrhage
usually happens in 1st 3 days
most are mild and self resolve
some cause pressure -> brain damage
then need to drain blood/use med to reduce fluid build up
when does NEC normally develop
2-3 wks after birth
what is retinopathy of prematurity
an abnormal growth of blood vessels in the eye -> vision loss.
less than 32 weeks.
Most cases heal themselves with little or no vision loss.
In severe cases - laser or with cryotherapy (freezing) to preserve vision.
what is NEC
inflammation bowel wall -> necrosis and perf
bloody stools
abdo distension
intramural air
when does renal function develop
nephrons from wk 6
produce urine from wk 10
full complement from wk 36
functional maturity of GFR not reached until 2yrs
consequence of renal function developing late
low GFR for surface area ->
* slow excretion of solute load
* limited Na for H+ change -> acidosis
short prox tubule ->
* lower reabsorptive capacity (although adequate for the small filtered load)
* renal threshold for glycosuria is lower – plasma glucose >7
* Reabsorption of bicarb is not as effective -> risk of acidosis
Loops of Henle/distal collecting ducts are short and juxtaglomerular ->
* reduced concentrating ability with a maximum urine osmolality of 700 mmol/kg
Distal tubule is relatively unresponsive to aldosterone:
* leads to a persistent loss of sodium of c.1.8 mmol/kg/day
* -> reduced K secretion
proportion of ECF in adult, term baby and prem
Babies more extracellular fluid than an adult does
When born - Pul resistance goes down - Release AMP – redistribution of fluid -> wht loss in 1st wk of life.
how much wht loss is allowed in the 1st week of life
10%
should regain by day 7-10
na and k requirements in neonates
Requirements build up with days
Na higher when less than 30wks – because of leak from the kidney – persistent Na loss
Check K daily in prem infant when we give fluids
Don’t rely on spot urine in neonate
Only give K after achieved a urine output – if give before then you risk hypernatraemia and all those difficulties
They need about 6x more fluid than adult etc
causes of electolyte disturbances in neonates
high water loss from high
* surface area
* skin blood flow
* metabolic/resp rate
* transepidermal fluid loss (skin isnt keritinised at birth)
drug causes of electrolyte disturbance in neonates
Bicarbonate (for acidosis)
* High Na content
Antibiotics
* high Na content
Caffeine/theophylline (for apnoea)
* Renal Na loss
Indomethacin (forPDA)
* oliguria
note: if keep replacing Na you risk hypernatraemia
causes of hypernatraemia in neonates
rare after 2 wks - normally due to dehydration
rarely - salt poisening and osmoregulatory dysfunction - consider if repeated w/o obv cause
how do you differentiate rare causes of hypernatraemia in the neonate
Routine measurement of urea, creatinine and electrolytes on paired urine and plasma on admission
pathway of aldosterone production
cause of hyponatraemia in neonate
rare
congenital adrenal hyperplasia
loss of 21-hydroxylase
* -> low aldosterone
-> Na loss (hypoNa)
- also loss of cortisol -> hypoglycaemia
- high level precursers - high androgens
-> ambiguous genitalia
growth accelaration - rare presentation
physiological causes of high BR in neonate
ucBR
* High level of synthesis (rbc breakdown)
* Low rate of transport into liver
* Enhanced enterohepatic circulation
problem with high BR in neonate
1g/L albumin binds 10micromol/L BR
Average albumin at term 34 g/l (lower in prem)
Free bilirubin crosses the blood brain barrier and causes Kernicterus (bilirubin encephalopathy)
in prem the levels for exchange transfusion and phototherapy are much lower
causes of high BR less than 24hrs
Haemolytic disease (ABO, rhesus etc)
G-6-PD deficiency
Crigler-Najjar syndrome – metabolic high BR, deficiency of conjugation
definition of prolonged jaundice
jaundice that lasts for more than
* 14 days in term babies
* 21 days in preterm babies.
causes of prolonged jaundice
Prenatal infection/sepsis/hepatitis
Hypothyroidism - screened in Guthrie
Breast milk jaundice
causes of raised cBR >20umol/L
always pathological
biliary atresia
ascending cholangitis in TPN - related to lipid content
metabolic disorder
* galactosaemia,
* alpha-1-AT deficiency
* tyrosinaemia 1 - plasma amino acids
* peroxisomal dis - very long chain fatty acid profile
