Background: A single high loading dose of 25 mg/kg caffeine has been shown to be effective for the prevention of apnoea, but may result in considerable reduct ions in blood flow velocity (BFV) in cerebral and intestinal arteries. Objective : To assess the effects of two loading doses of 12.5 mg/kg caffeine given four h ours apart on BFV in cerebral and intestinal arteries, left ventricular output (LVO), and plasma caffeine concentrations in preterm infants. Design: Sixteen pre term neonates of < 34 weeks gestation were investigated one hour after the first oral dose and one, two, and 20 hours after the second dose by Doppler sonograph y. Results: The mean (SD) plasma caffeine concentrations were 31 (7) and 29 (7) mg/l at two and 20 hours respectively after the second dose. One hour after the first dose, none of the circulatory variables had changed significantly. One hou r after the second caffeine dose, mean BFV in the internal carotid artery and an terior cerebral artery showed significant reductions of 17%and 19%(P=0.01 and P=0.003 respectively). BFV in the coeliac artery and superior mesenteric artery, LVO, PCO2, and respiratory rate had not changed significantly. Total vascular r esistance, calculated as the ratio of mean blood pressure to LVO, had increased significantly one and two hours after the second dose (P=0.049 and P=0.023 respe ctively). Conclusion: A divided high loading dose of 25 mg/kg caffeine given fou r hours apart had decreased BFV in cerebral arteries after the second dose, wher eas BFV in intestinal arteries and LVO were not affected.
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