This study evaluated the efficacy of intraarterial papaverine infusion after pediatric cardiac catheterization in reducing the incidence of lost pulse. This study was conducted at a teaching pediatric hospital and was designed as a randomized, prospective, double-blind, placebo-controlled study. Patients were children 5 years old or less undergoing antegrade and retrograde heart catheterization. The intervention used was an intraarterial infusion of placebo or 1.5 mg/kg papaverine after catheterization. Bilateral femoral artery ultrasound study was performed pre- and postcatheterization, including two-dimensional, color, spectral, and pulsatility index analysis. Outcome measures included clinical loss of pulse, ultrasound findings, plus other clinical factors. Fifty-six patients participated in the study (28 per group). Six patients clinically lost the pulse in the catheterized arteries [four in the papaverine and two in the placebo groups (p > 0.64)]. Clinical loss of pulse correlated with diminished pulsatility index (p < 0.035). The use of papaverine did not prevent decreased pulse or pulsatility index (p > 0.79). Increased arterial time was the only clinical factor associated with lost pulse (p < 0.0004). Pulsatility index <3.34 correlated with loss of pulse in the catheterized artery. The results indicated that intraarterial papaverine infusion after femoral artery catheterization does not prevent loss of pulse in the catheterized artery, and decreased pulsatility index correlates with diminished pulse and represents a good noninvasive method of evaluating femoral artery patency and flow.