Regional blood flow response to hypothermia in premature, newborn, and neonatal piglets

Background/Purpose: Hypothermia (HT) remains a significant stress to the ne wborn and has been implicated in the pathogenesis of necrotizing enterocoli tis (NEC). The authors assessed the effect of transient HT (32 degrees C) o n regional organ blood flow in anesthetized piglets at age 7 to 10 days pre term (PREM), 1 to 2 days (NB), and 1 to 2 weeks (NEO). Methods: Radiolabeled microspheres were used to determine organ blood flows (mL/min/g) at baseline, 15, and 60 minutes after HT and 60 minutes after r ewarming to baseline core temperature. Results: Heart rate and cardiac output decreased significantly in all group s. Cardiac flow decreased significantly in the NEO group, and central nervo us system (CNS) flow decreased significantly in the NE and NEO groups. Both returned to baseline levels after rewarming. The PREM group experienced de creased cardiac, CNS, and intestinal blood flows but not to significant lev els. NE and NEO intestinal blood flow showed significant decreases, which r emained so after rewarming (a response not seen in hypoxia or hypovolemia). Cardiac output did not return to baseline levels in any group. Conclusions: HT causes derangements in organ blood flows that differ from o ther deleterious stimuli such as hypoxia and hypovolemia. The prolonged int estinal ischemia supports HT as a factor in the development of NEC. This de lay may offer opportunity to intervene in an attempt to lessen ischemia-rep erfusion injury. J Pediatr Surg 34:193-198. Copyright (C) 1999 by W.B. Saun ders Company.