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Is mesenteric blood flow compromised during phototherapy in preterm neonates?
  1. R Kadalraja,
  2. S K Patole,
  3. R Muller,
  4. J S Whitehall
  1. Department of Neonatology, Kirwan Hospital for Women, and School of Public Health and Tropical Medicine, James Cook University, Queensland, Australia
  1. Correspondence to:
    S Patole
    Department of Neonatal Paediatrics, KEM Hospital for Women, University of Western Australia, Perth, Western Australia 6008; skpatolehotmail.com

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We have previously reported that abdominal distension, visible “ropy” bowel loops, and bile stained gastric aspirates (manifestations of ileus) without loose watery stools are more often observed in preterm neonates having conventional phototherapy (CPT) than in those not having this treatment.1 Reported changes in the mesenteric blood flow as well as peripheral blood flow and cardiac output during CPT indicate that mesenteric ischaemia may occur during CPT in preterm neonates.2–4 We hypothesised that mesenteric blood flow may be compromised during CPT in preterm neonates who are not being fed. If our hypothesis was true, mesenteric ischaemia may explain ileus during CPT in preterm neonates.

In a prospective observational study, superior mesenteric artery blood flow (maximum, minimum) velocity and resistive index (RI) were measured by ultrasound pulsed Doppler in 14 consecutive preterm neonates before and 8–12 hours after the start of CPT. At the time of the study, they did not have associated common risk factors for ileus such as patent ductus arteriosus, indomethacin, sepsis, electrolyte imbalance, and enteral feeds. Their ventilatory/oxygen needs were minimal, and cardiovascular support was not required. The birth weight, gestational age, and postnatal age of the enrolled neonates were 885–1410 g, 27–29 weeks, and 2–4 days respectively. The mean (SD) maximum velocity (Vmax) and RI before and after the start of CPT were not significantly different: Vmax, 0.41 (0.13) v 0.50 (0.11) m/s (p  =  0.10); RI, 0.73 (0.08) v 0.70 (0.08) (p  =  0.10). Minimum velocity after CPT was, however, significantly increased: 0.06 (0.04) v 0.16 (0.05) m/s (p < 0.001). Ileus developed 4.8 (2.1) days after the initiation of CPT in 8/14 neonates despite the absence of the risk factors studied.

Increased superior mesenteric artery end diastolic blood flow velocity may indicate photorelaxation of the mesenteric vascular smooth muscle during CPT.5 CPT per se may be a risk factor for ileus in preterm neonates.

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