PHOTOTHERAPY-A REVIEW

Srichakra Scientifics Pvt. Ltd.

OUTLINE• HISTORICAL NOTES

• MECHANISM-HOW IT WORKS• EFFICACY DATA• SIDE EFFECTS• LONG TERM OUTCOME

HISTORICAL 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 SPECTRUM OF

BILIRUBIN

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

CONFIGURATIONAL ISOMERIZATION (4Z,15E)

STRUCTURAL ISOMERIZATION

(LUMIRUBIN)

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

PHOTO-CHEMICAL REACTION & ELIMINATION

OF BILIRUBIN

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

LIGHT SPECTRUM OF LED

RCT FOR LED VS HALOGEN LAMP

220

230

240

250

260

LED HALOGEN

ENTRY

DURING

SERUM BILIRUBIN (µM/L)

SEDMAN, DS ET AL J PEDTRIC136:771,2000

(N=34) (N=35)