INTRAVENOUS IMMUNE GLOBULIN IN NEONATAL ABO ISOIMMUNIZATION - FACTORSASSOCIATED WITH CLINICAL EFFICACY

Objective: Intravenous immune globulin (IVIG) reduces jaundice in many but not all cases of neonatal isoimmunization. We sought to elucidate the type of infant most likely to benefit from IVIG administration by attempting to define pretreatment parameters associated with both cli nical symptomatology and therapeutic responsiveness to IVIG. Methods: Term, healthy Coombs-positive infants were studied prospectively. IVIG was administered if, despite phototherapy, serum bilirubin reached gr eater than or equal to 222 mu mol/l (13 mg/dl) at less than or equal t o 24 h of age and/or greater than or equal to 274 mu mol/l (16 mg/dl) at > 24 h of age. Clinical data including serial serum total bilirubin levels, rate of bilirubin rise on day 1 of life, serial corrected car boxyhemoglobin levels (a sensitive indicator of hemolysis) and total h emoglobin (tHb) levels were collected. Results: Infants were classifie d as IVIG responders (n = 18), those in whom total serum bilirubin lev els either remained stable or decreased following IVIG administration; IVIG nonresponders (n = 5), those who developed a total serum bilirub in of greater than or equal to 2 mg/dl greater than pre-IVIG bilirubin levels within the first 24 h after IVIG administration, or nontreated , those not meeting IVIG treatment criteria (n = 13). Four of the five nonresponders proceeded to require exchange transfusion vs. none of t he others (p < 0.001). Four of the five nonresponders had a pretreatme nt rate of bilirubin rise of greater than or equal to 1 mg/dl/h as com pared with only 1 of 18 responders and none of the nontreated (p < 0.0 01). Pretreatment tHb levels were also different (13.2 +/- 1.3 vs. 15. 5 +/- 2.3 vs. 17.7 +/- 2.4 g/dl for nonresponders vs. responders vs, n ontreated infants, respectively; p < 0.005). The highest pretreatment COHbc levels were seen in the nonresponders (1.8 +/- 0.7 vs. 1.4 +/- 0 .3 vs. 0.9 +/- 0.3% tHb, respectively). Conclusions: Our 3 groups repr esent a spectrum of hemolysis, ranging from severe to moderate to mild . This spectrum appears to relate not only to the severity of hemolysi s, but also to the therapeutic responsiveness to IVIG. We speculate th at some or all of the factors identified can be used prospectively to predict the subsequent clinical course of ABO-incompatible infants and to facilitate optimal management.