Changes in cerebral, renal and mesenteric blood flow velocity during continuous and bolus infusion of indomethacin. Continuous versus multiple rapid infusions of indomethacin: effects on cerebral blood flow velocity.
Vasoconstriction induced by bolus injection of indomethacin reduces organ perfusion and has been related to the well-known side effects of indomethacin given for closure of the patent ductus arteriosus (PDA). The aim of the study was to compare the changes in cerebral, renal and mesenteric blood flow velocities after continuous infusion versus bolus injection of indomethacin for closure of the PDA. Thirty-two preterm infants (range 26-35 wk gestational age) with PDA were randomly assigned to receive the same amount of indomethacin either as three bolus injections (n = 14) or as a continuous infusion (n = 18) over 36 h. Blood flow velocities were measured in the internal carotid, right renal and superior mesenteric arteries at baseline and serially at 10, 30, 60 and 120 min and 12, 24, 36 and 48 h after the start of indomethacin treatment. There were no differences in blood flow velocities between both groups at baseline. During continuous infusion of indomethacin there was no significant change in the cerebral, renal and mesenteric blood flow velocities, whereas the flow velocities in the infants receiving bolus injections decreased significantly during the first 2 h after indomethacin administration in all arteries measured. There was a transient, but significant reduction in urine output after bolus injection of indomethacin. Conclusion: In contrast to bolus injections, decrease of organ blood flow and impairment of urine output do not accompany continuous infusion of indomethacin over 36 h. Therapeutic administration of indomethacin for patent ductus arteriosus (PDA) closure has been documented to decrease cerebral blood flow velocity which may be harmful to the vulnerable premature neonate. We have therefore compared the effects of administering indomethacin by rapid injection versus slow, continuous indomethacin infusion at the same total therapeutic dose on middle cerebral artery (MCA) systolic and diastolic flow velocity, resistance index, and cerebral blood flow (as reflected by the integrated area under the curve).
                Premature neonates (< 1750 g) documented echocardiographically to have a PDA were randomized to receive indomethacin either by three rapid injection doses or by continuous intravenous infusion over the ensuing 36 hours, providing an equivalent total dose. Echocardiograms and transcranial color flow mapping of the MCA flow velocity were measured at baseline and serially following initiation of therapy in both groups. Effects on cerebral blood flow velocity are presented.
                Eighteen infants [rapid injection-1.2 +/- 0.3 kg (n = 9) and continuous-1.1 +/- 0.2 kg (n = 9)] were studied. In the rapid injection treated infants decreased flow velocity in the MCA as manifested by abrupt, significant decreases in systolic (to 70 +/- 8% baseline) and diastolic (to 65 +/- 13% baseline) flow velocity and area under the curve (to 60 +/- 10% of baseline) were evident by 4 minutes and progressed to 30 minutes after treatment initiation. These changes were not observed in the group treated with continuous indomethacin. Both therapeutic modalities were equally successful in closing the ductus, although the numbers are too small to definitively determine therapeutic efficacy.
                Slow, continuous infusion eliminated the decrease in cerebral flow velocity and appears to be effective in closing the PDA.
The available data is insufficient to draw conclusions regarding the efficacy of continuous indomethacin infusion vs. bolus injections for the treatment of PDA. Although continuous indomethacin seems to cause less alterations in cerebral, renal and mesenteric circulations, the clinical meaning of this effect is unclear. Definitive recommendations about the preferred method of indomethacin administration in premature infants cannot be made based on the current findings of this review.