Indo is widely used for noninvasive closure of PDA in preterm infants and is known to decrease blood flow in several organs. Side effects of Indo are probably related to the changes in organ blood flow.

Purpose of this study was to determine whether continuous infusion of Indo minimizes changes in cerebral, renal and mesenteric blood flow velocity.

Methods: Twenty one preterm infants (range 26-35 wks GA) with PDA confirmed by pulsed Doppler ultrasound were enrolled into the study. They were randomized into two groups: 1. Continous infusion (Cont) of 0.4mg/kg Indo during 36 hours. 2. Three bolus injections (Bolus) of Indo (t0 0.2mg/kg; t12h 0.1mg/kg; t36h 0.1mg/kg). Pulsed Doppler ultrasound measurements of the mean blood flow velocity in the internal carotid artery (cbfv), right renal artery(rbfv) and superior mesenteric artery (mbfv) were performed at baseline and serially after initiating of Indo administration at 10, 30, 60, 120 min and 12, 24, 36, 48h. Heart rate, blood pressure, SaO2, tcpO2, tcp and CO2 were recorded continuously.

Results: Cont: n = 13, mean ±SD BW 1084 ±311g; GA29.6 ±2.2 wks. Bolus: n = 8; BW 1410 ±652g; GA 30.8±2.6 wks. No significant changes from baseline were seen for cbfv, rbfv, and mbfv in Cont. Compared to Cont, in Bolus cbfv, rbfv, and mbfv were significantly lower after the first bolus with a maximal decrease at 30 min; cbfv: p 0.006; rbfv: p 0.025; mbfv: p 0.046. Cbfv, rbfv, and mbfv did return to baseline in bolus 12h after the onset of Indo, and remained stable thereafter. Changes in cbfv, rbfv and mbfv were not related to changes in blood pressure and bloodgases. Succesful closure of PDA was similar in both groups: Cont 8/13(62%), Bolus 5/8(63%); P:NS.

Conclusion: In contrast to bolus injection, continuous infusion of Indo does not cause significant changes in cbfv, rbfv and mbfv and appears to be as effective as bolus injection for closure of PDA.