Rachel Garner

The University of Arizona, Tucson, Arizona, United States

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Publications (4)10.32 Total impact

  • Rachel S Garner · David J Burchfield
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    ABSTRACT: Context Previous studies have correlated poor neurological outcomes with hypotension. Treatment of hypotension in very low birthweight (VLBW) infants is common, and most often is based solely on the blood pressure measurement. Whether treatment improves cerebral oxygenation is unclear. Objective To determine if treatment of hypotension in VLBW neonates results in an increase in cerebral oxygenation. Patients and methods In this single centre observational study, neonates <30 weeks and <1500 grams, blood pressure and regional cerebral oximetry (rCSO2) with near infrared spectroscopy were continuously monitored and digitally recorded. If patients were treated for hypotension during the first 3 days of life, effects of treatment on blood pressure and regional cerebral saturation were determined. Results Twenty-eight of 50 patients were treated by the medical team for hypotension, of which 22 had accurate data recorded for analysis. Both normal saline 10 ml/kg, and dopamine 2.5–5 mcg/kg per min significantly increased blood pressure, (saline 26.8±3.5 to 28.8±4.2 mm Hg, p<0.005; dopamine 27.6±1.9 to 29.5±3.2 mm Hg, p<0.02). Pre-treatment values of rCSO2 were similar to published normative values and treatment with either normal saline or dopamine had no effect on rCSO2. Conclusion These results suggest that treating hypotension in VLBW neonates based solely on a blood pressure measurement of less than 30 mm Hg, while increasing blood pressure, may not increase cerebral oxygenation, possibly because many of these patients are in the autoregulatory zone for cerebral blood flow.
    No preview · Article · Jul 2012 · Archives of Disease in Childhood - Fetal and Neonatal Edition
  • R S Garner · C Miller · D J Burchfield
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    ABSTRACT: Intraventricular hemorrhage (IVH) occurs in up to 25% of very low birth weight (VLBW) preterm neonates. Previous studies found that indomethacin administered in the first 6 h of life reduces the incidence of severe IVH in VLBW neonates and decreases cerebral blood flow, suggesting a decrease in cerebral oxygen delivery. Using near-infrared spectroscopy (NIRS), we monitored cerebral oxygenation before, during and after slow indomethacin infusion in extremely low birth weight (ELBW) neonates to determine whether indomethacin decreases cerebral oxygen saturation and increases cerebral oxygen extraction. Twenty-seven ELBW neonates less than 30 weeks gestational age treated with indomethacin for IVH prophylaxis were monitored for arterial oxygen saturation (SaO(2)) and NIRS-determined regional cerebral oxygen saturation (rSO(2)). At 30 to 60 s intervals, SaO(2), rSO(2) and mean arterial pressure (MAP) were recorded using a VitalSync. Average fractional cerebral oxygen extraction was calculated for the hour before indomethacin infusion, during the infusion and 2 h after infusion. Fractional cerebral oxygen extraction increased from baseline after indomethacin administration from 0.23±0.11 to 0.25±0.10 (P=0.034). Fractional cerebral oxygen extraction increased 9% with indomethacin 0.1 mg kg(-1) given over 1 to 2 h. However, the clinical implications of this small increase in extraction, likely representative of decreased cerebral perfusion, are unknown but may be harmful to the developing brain.
    No preview · Article · Jan 2012 · Journal of perinatology: official journal of the California Perinatal Association
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    ABSTRACT: Although neonatal platelets have been shown to be hyporesponsive to most agonists in vitro, several groups have reported shorter closure times (CT) in term cord blood samples than in children and adults. It is unknown whether this is also true for preterm neonates, or for neonates of any gestational age (GA) during the 1st week of life, since limited studies have evaluated neonatal blood samples. We designed this study to determine the effects of GA and postconceptional age on platelet function using the platelet function analyzer PFA-100. We measured CTs in cord blood samples and in neonatal blood samples of varying GAs on days of life 1-2, and > or = 7. CTs were determined in 51 cord blood samples, 34 neonatal blood samples obtained on day of life 1-2, 16 neonatal blood samples from preterm neonates > or = 7 days old, and 10 adults. We found a significant inverse relationship between ADP CTs and GA in both cord blood and neonatal blood day of life 1-2 samples (p = 0.02 and p = 0.01, respectively). When cord blood samples were compared with neonatal and adult blood, epinephrine and ADP CTs were significantly longer in adult blood as well as in neonatal samples obtained at either of the two time points (p < or = 0.01 for all). Platelet function in response to ADP appears to improve with advancing GA. The differences between cord blood and neonatal blood CTs indicate that substantial changes in primary hemostasis occur shortly after birth. The reasons underlying these changes are unknown.
    No preview · Article · Oct 2009 · Neonatology
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    ABSTRACT: Little is known about the sites and kinetics of thrombopoiesis following bone marrow transplant. The spleen is a site of hematopoiesis in a healthy mouse, and hematopoietic activity increases in response to stress. We hypothesized that the spleen is a major site of early post-transplant thrombopoiesis. We transplanted whole bone marrow (WBM) or lineage depleted progenitor subsets fractionated based on expression of c-kit and Sca-1 from transgenic mice expressing green fluorescent protein into lethally irradiated C57BL/6 recipients. We also transplanted whole bone marrow cells into healthy and splenectomized mice. Post-transplant megakaryopoiesis was assessed by measuring circulating platelet number, percent donor-derived platelets, bone marrow cellularity, splenic weight, megakaryocyte size, and megakaryocyte concentration from hour 3 to day 28 post transplant. Following transplant, circulating donor-derived platelets were derived only from c-kit expressing subsets. Donor-derived platelets first appeared on post-transplant day five. Splenectomy reduced the number of these earliest circulating platelets. Splenic megakaryopoiesis increased dramatically from day 7-14 post-transplant. However, splenectomy accelerated platelet engraftment during this time frame. Overall, these results demonstrate that the first platelets are produced by c-kit expressing megakaryocyte progenitors in the bone marrow and spleen. After post-transplant day 5, the net effect of the spleen on thrombopoiesis is to slow engraftment due to immune effects or hypersplenism.
    No preview · Article · Nov 2007 · Experimental Hematology