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 Medical Care of Neonatal Jaundice
Medical Care
- Phototherapy
- Exchange transfusion
- Drugs
- Diet
Phototherapy
Photo therapy is the primary treatment, was discovered serendipitously in England in the 1950s.
Why Phototherapy is effective?
Three reactions can occur when bilirubin is exposed to light:
1- photooxidation.
2- Configurational Isomerization.
3- Structural Isomerization.
1-Photooxidation
Was believed to be responsible for the beneficial effect of phototherapy. Although bilirubin is bleached through the action of light, the process is slow and is now believed to contribute only minimally to the therapeutic effect of phototherapy.
2-Configurational Isomerization
Is a very rapid process that changes some of the predominant bilirubin isomer to water-soluble isomers. The isomer constitutes 20% of circulating bilirubin after a few hours of phototherapy. This proportion is not influenced significantly by the intensity of light.
3-Structural Isomerization
Consists of intramolecular cyclization, resulting in the formation of lumirubin.
This process is enhanced by increasing the intensity of light.
During phototherapy, lumirubin may constitute 2-6% of the total
serum bilirubin concentration.
Bear in mind:
When initiating phototherapy, lowering of the total serum bilirubin concentration is only part of the therapeutic benefit. 75-80% of the total bilirubin is present in a form that can enter the brain.
So Phototherapy reduces the risk of bilirubin-induced neurotoxicity as soon as the lights are turned on.
Factors That Affect the Dose and Efficacy of Phototherapy
- Wavelength:
Bilirubin absorbs light primarily around 450 nm. Typically 425 to 475 nm
In practice, light used in wavelengths (white, blue, and green).
- Irradiation Level:
A dose-response relationship exists
- 30-40 mW/cm2/nm.
- 6 mW/cm2/nm.
- Distance:
Distance should not be greater than 50 cm (20 in) and can be less if the infant's temperature is monitored.
Energy delivered decreases with increasing distance.
- Bilirubin Concentration:
The efficiency of phototherapy increases with:
- Serum Bilirubin concentration.
- Skin surface.
- Nature and character of the light source:
Different light sources can be used:
- Quartz halide spotlights.
- Green light.
- Blue fluorescent tubes.
Narrow-Spectrum Ordinary: - White (daylight) fluorescent tubes.
- White quartz lamps.
- Fiber optic light.
Historical data
Derived from infants with hemolytic jaundice suggest that:
Total serum bilirubin levels greater than (20 mg/dL) were associated with increased risk of neurotoxicity, at least in full-term infants.
Autopsy findings suggested that:
Immature infants were at risk of bilirubin encephalopathy at lower total serum bilirubin levels than mature infants.
But unfortunately, because the endpoint of bilirubin neurotoxicity is permanent brain damage, a randomized study to reassess the guidelines is ethically unthinkable.
Indications for phototherapy
In most neonatal wards, total serum bilirubin levels are used as the primary measure of risk for bilirubin encephalopathy. Test for serum albumin have failed to gain widespread acceptance.
Physicians in different ethnic or geographic regions must consider factors that are unique to their medical practice settings.
Such factors may include:
- racial characteristics.
- prevalence of congenital hemolytic disorders.
- environmental concerns.
Key points in the practice
- Maximizing energy delivery.
1- Distance should be no greater than 50 cm and may be reduced down to 10-20 cm if temperature homeostasis is monitored to reduce the risk of overheating.
2- Cover the inside of the bassinet with reflecting material; white linen works well.
3- Hang a white curtain around the phototherapy unit and bassinet.
These simple expedients can multiply energy delivery by several folds.
- Maximizing the available surface area.
The infant should be naked except for diapers and the eyes should be covered to reduce risk of retinal damage.
Intermittent Versus Continuous Phototherapy.
Clinical studies have produced conflicting results. Individual judgment should be exercised.
If the infant’s bilirubin level is approaching the exchange transfusion zone, phototherapy should be administered continuously until a satisfactory decline in the serum bilirubin level occurs or exchange transfusion is initiated.
Insensible water loss
New data suggest that if temperature homeostasis is maintained, fluid loss is not increased significantly by phototherapy.
In infants who are fed orally, the preferred fluid is milk, since milk serves as a vehicle to transport bilirubin out of the gut.
Timing of follow-up serum bilirubin?
- In infants admitted with extreme serum bilirubin values (30 mg/dL): monitoring should occur every hour or every other hour. Reductions in serum bilirubin values (5 mg/dL/h).
- In infants with more moderate elevations of serum bilirubin: monitoring every 6-12 hours.
Expectations regarding efficacy of phototherapy
- Bilirubin concentrations are still rising.
(A significant reduction of the rate of increase)
- Bilirubin concentrations are close to their peak
(Phototherapy should result in measurable reductions in serum bilirubin levels within a few hours)
In general, the higher the starting serum bilirubin concentration, the more dramatic the initial rate of decline.
When discontinuation of phototherapy?
When serum bilirubin levels fall (1.5-3 mg/dL) below the level that triggered the initiation of phototherapy. Serum bilirubin levels often rebound , and follow-up tests should be obtained within 6-12 hours after discontinuation.
What about prophylactic Phototherapy ?
In general, the lower the serum bilirubin level, the less efficient the phototherapy.
Phototherapy complications
Phototherapy is very safe, and it may have no serious long-term effects in neonates.
- Insensible water loss is not as important as previously believed.
- Loose stools.
- Retinal damage
- Effects on cellular genetic material (In vitro and animal data have not been shown any implication for treatment of human neonates. However, most hospitals use cut-down diapers during phototherapy).
- Skin blood flow is increased therefore redistribution of blood flow may occur in small premature infants which will cause Increased incidence of patent ductus arteriosus (PDA) has been reported But this effect is less pronounced in modern servocontrolled incubators.
- Hypocalcemia in premature infants. It has been suggested that this is mediated by altered melatonin metabolism.
- Deterioration of certain amino acids in total parenteral nutrition (TPN) solutions. Shield TPN solutions from light as much as possible.
- Accidents have been reported, including burns resulting from failure to replace UV filters.
Exchange transfusion
What are indications of Exchange transfusion?
- Avoiding bilirubin neurotoxicity when other therapeutic modalities have failed.
- In addition, even in the absence of high serum bilirubin levels, the procedure may be indicated in infants with erythroblastosis.
Exchange transfusion has been performed because of:
- Cord hemoglobin (<11 g/dL).
- Cord bilirubin (>4.5 mg/dL).
- Rapid rate of increase in bilirubin (>1 mg/dL/h).
- More moderate rate of increase in bilirubin (> 0.5)
In the presence of moderate anemia (Hb=11-13).
- Hemolytic jaundice with bilirubin (>20) or a rate of increase that Predicted this level (fear of 20).
Why Exchange transfusions become a rare procedure?
Immunotherapy in Rh-negative women so, ABO incompatibility has become the most frequent cause of hemolytic disease in industrialized countries.
Effective phototherapy:
Recently, immunotherapy has been introduced as treatment in the few remaining sensitized infants. Results are promising.
When exchange transfusion should be performed?
- When phototherapy does not significantly lower serum bilirubin levels.
- Intensive phototherapy is strongly recommended in preparation for an exchange transfusion. Do not await laboratory test results in these cases.
Does nonhemolytic jaundice cause Neurotoxicity?
Many physicians believe that hemolytic jaundice represents a greater risk for neurotoxicity than nonhemolytic jaundice, although the reasons for this belief are not obvious.
In animal studies, bilirubin entry into the brain was not affected by the presence of hemolytic anemia.
DRUGS
- Phenobarbital (an inducer of hepatic bilirubin metabolism)
Several studies have shown that phenobarbital is effective.
Phenobarbital may be administered:
- Pre-natally in the mother
- Post-natally in the infant.
However, concerns exist regarding the long-term effects of phenobarbital on these children.
- IV immunoglobulin (500 mg/kg)
Significantly reduce the need for exchange transfusions in infants with isoimmune hemolytic disease.
The mechanism is unknown. Experience is somewhat limited, but it does not appear risky.
- New therapy :Mesoporphyrins and Protoporphyrins
Currently under development,I nhibition of bilirubin production through blockage of heme oxygenase.
Apparently, heme can be excreted directly through the bile.
This approach may virtually eliminate neonatal jaundice as a clinical problem.
But there are important questions before the treatment can be applied.
- Long-term safety?
- Complete understanding of putative role for bilirubin in light of data suggesting that bilirubin may play an important role as a free radical quencher (anti-oxidant)?
DIETE
- Temporary interruption of breastfeeding is not recommended unless serum bilirubin levels reach 20 mg/dL.
- Supplementation with dextrose solution is not recommended because:
- It may decrease milk production
- It may accelerate entero_hepatic circulation and consequently
delay the drop in serum bilirubin concentration.
So what is the recommendation?
Increase breastfeeding to 8-12 times per day
Breastfeeding can also be supported with manual or electric pumps and the pumped milk given as a supplement to the baby.
Some questions
- When infants can be discharged?
When they are feeding adequately and demonstrating a trend towards lower values.
An auditory function test prior is advisable in infants who have had severe jaundice.
- How to manage infants released within the first 48 hours of life?
In the era of early discharge in recent years, a number of infants have developed kernicterus therefore infants need to be reassessed for jaundice within 1-2 days.
Use of hour-specific bilirubin nomogram may assist in selecting infants .
- Do infants need follow-up obsevation after Bilirubin falls?
Infants with hemolytic jaundice require follow-up observation for several weeks because hemoglobin levels may fall lower than seen in physiologic anemia.
Erythrocyte transfusions may be required if infants develop symptomatic anemia.
- Finally…What about Prognosis?
Prognosis is excellent if the patient receives treatment according to accepted guidelines.
The increased incidence of kernicterus in recent years may be due to the misconception that jaundice in the healthy full-term infant is not dangerous and can be disregarded.
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