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OUTLINE• HISTORICAL NOTES
• MECHANISM-HOW IT WORKS
• EFFICACY DATA
• SIDE EFFECTS
• LONG TERM OUTCOME
HISTORICAL NOTEHISTORICAL NOTEFIRST PAPER ON PHOTOTHERAPY
PUBLISHED IN 1958 (CREMER,LANCET) BASED ON THEIR IN VITRO
OBSERVATION OF FALLING VALUES OF BILIRUBIN WHEN SERUM SAMPLES
WERE EXPOSED TO LIGHT
HISTORICAL NOTES-CONT’D
• SEVERAL CLINICAL TRIALS IN THE ’60s CONFIRMED THE EFFICACY OF PHOTOTHERAPY LEADING TO ITS USE AS STANDARD CARE
TRIALS ALSO SHOWED MORE EFFICACY AMONG LOW BIRTH WEIGHT INFANTS
MECHANISM• BILIRUBIN ABSORS PHOTON FROM
LIGHT AT 450 nm ( IN VITRO)
• PHOTOCHEMICAL REACTIONS
• FORMATION OF THREE MAJOR PRODUCTS THAT ENHANCES ELIMINATION
ABSORPTION OF LIGHT BY BILIRUBIN IN VIVO
• BECAUSE BILIRUBIN IN VIVO IS BOUND TO ALBUMIN ,SPECTRUM OF MAXIMUM ABSORPTION IS SHIFTED TO THE RIGHT ( 450 TO 475 nm)
• THIS EXPLAINS THE VARIABLE EFFICACY OF LIGHT USED IN CLINICAL SETTING
PHOTOCHEMICAL REACTIONS
LIGHTBILIRUBIN ABSORBS PHOTON ‘ EXCITED’ BILIRUBIN ↓ ↓ ↓ ↓ PHOTO-OXIDATION
↓ STRUCTURAL ISOMEZARATION
(LUMIRUBIN) ↓ CONFIGURATIONAL ISOMERIZATION ( 4E,15Z,4Z,15E AND 4E,15E PHOTOISOMERES)
PHOTO-OXIDATION
• SINCE CREMER’S REPORT(1958), IT HAS BEEN ASSUMED THAT PHOTO-OXIDATION IS THE MECHANISM FOR BILIRUBIN EXCRETION
• 1984, ISOMERE FORMATION FOUND TO BE THE MAJOR MECHNISM
PHYSICAL PROPERTY OF BILIRUBIN AND ITS PRODUCT• NATIVE BILIRUBIN ( 4Z,15Z)
HYDROPHOBIC AND LIPOPHYLIC
• BILIRUBIN ISOMERES ARE LESS LIPOPHYLIC AND HYDROPHOBIC
• ENHANCE ELIMINATION VIA BILE AND URINE
RATE OF FORMATION & ELIMINATION OF
BILIRUBIN
• RATE OF FORMATION:4Z,15E ISOMERES > LUMIRUBIN > PHOTO-OXIDATION PRODUCTS
• RATE OF EXCRETION:LUMRUBIN >4Z,15E > PHOTOOXIDATION PRODUCTS
• LUMIRUBIN APPEARS TO BE THE MAJOR FORM OF ELIMIATION
FACTORS AFFECTING EFFICACY OF
PHOTOTHERY • DEPENDENT ON
– TYPE OF LIGHT USED
– LIGHT INTENSITY
– SURFACE AREA OF SKIN EXPOSED TO LIGHT
– DISTANCE FROM LIGHT TO BABY
TYPES OF PHOTOTHERAPY
DEVICE• FLUORESCENT TUBES
– DAYLIGHT(WHITE)– BLUE– GREEN
• HALOGEN LAMPS
• FIBEROPTIC SYSTEM
• GALLIUM NITRIDE LIGHT EMITTING DIODES (L.E.D)
COMPARISON OF DIFFERENT LIGHTS
0
10
20
30
40
SPECIAL BLUE GREEN DAYLIGHT
% REDUCTION IN SERUM BILIRUBIN
TAN KL ET AL: PEDIATRICS,114:132,1989
P<0.05
CONCLUSION (TAN)• PREFERABLE TO USE EITHER
DAYLIGHT( PROVIDES ENHANCED CLINICAL OBSERVATION AND ADEQUATE EFFICACY) OR BLUE LIGHT (BETTER EFFICACY)
• NOT GREEN LIGHT WHICH PROVIDES NEITHER
HALOGEN LAMPS
• MORE COMPACT THAN FLORESCENT LAMP
• CAN NOT BE BROUGHT TOO CLOSE TO INFANT ( RISK OF BURN)
FIBEROPTIC SYSTEM (WALLABY)
• ADVANTAGES– NO EYE PATCH NECESSARY– MORE PORTABLE– CONVENIENT FOR MOTHER AND
HOME THERAPY
• DISADVANTAGE– LOW SPECTRAL POWER
FIBEROPTIC VS. CONVENTIONAL
0
0.5
1
1.5
2
2.5
GALE HOLTROP
FIBER
CONV.
N.S. P<0.05
DECLINE IN SERUM BILIRUBIN (M/L/HR)
LIGHT EMITTING DIODES
• NARROW BAND OF LIGHT SPECTRUM( BLUE-GREEN)
• POWER EFFICIENT AND LOW HEAT EMISSION
• SOMEWHAT EYE-IRRITATING TO THE STAFF
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