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Papers by HELENA PEREZ MARTIN

Ultrasound in Obstetrics and Gynecology, 2003

Oral communication abstracts 3 weeks interval associated with dz/dt <−1, presents a clinically ac... more Oral communication abstracts 3 weeks interval associated with dz/dt <−1, presents a clinically acceptable false-positive rate for IUGR diagnosis.

Pediatrics, 2001

Objective. To evaluate the diagnostic value of peripheral circulatory reactive hyperemia and seru... more Objective. To evaluate the diagnostic value of peripheral circulatory reactive hyperemia and serum levels of interleukin-6 (IL-6), IL-8, and tumor necrosis factor-α (TNF-α) in early-onset neonatal sepsis. Methods. Reactive hyperemia in the dorsal hand and serum levels of IL-6, IL-8, and TNF-α were studied in newborn infants (n = 32; gestational age 39 ± 3 weeks) who had been admitted to the neonatal unit because of suspected sepsis <48 hours after birth. On admission, reactive hyperemia after a standardized arterial occlusion was measured with laser Doppler technique, and blood samples were taken for cytokine analyses. On the basis of predetermined criteria, the infants subsequently were classified as septic (n = 12) or not (n = 20). Results. The degree of reactive hyperemia was higher in the group with sepsis (median + 170% perfusion increase) than in that without (+37%). On admission, serum levels of IL-6, IL-8, and TNF-α all were higher in septic (median values: 1620, 331, and...

Pediatrics, 2007

OBJECTIVE. Low maternal folate levels during pregnancy correlate with low birth weight, a perinat... more OBJECTIVE. Low maternal folate levels during pregnancy correlate with low birth weight, a perinatal risk factor for later cardiovascular disease. We studied relationships between red blood cell folate levels, birth weight, and vascular endothelial function (a key factor in the early pathophysiologic processes of heart disease) in newborn infants. METHODS. We included 82 infants (30 low birth weight) and their mothers. A laser Doppler technique was used to measure skin perfusion during transdermal iontophoresis of acetylcholine (an endothelium-dependent vasodilator). Red blood cell folate, vitamin B12, and homocysteine levels were determined. RESULTS. The perfusion response to acetylcholine was lower in low birth weight infants than in normal birth weight control subjects (mean: 35 vs 76 perfusion units). The neonatal acetylcholine response correlated with red blood cell folate levels in both infants and their mothers. The folate levels of low birth weight and control infants did not...

Pediatric Research, 2005

Preterm birth might induce permanent changes in vascular structure and function as well as in blo... more Preterm birth might induce permanent changes in vascular structure and function as well as in blood pressure. To elucidate this hypothesis and underlying mechanisms in girls born before term, the authors correlated neonatal data, including estradiol levels, with vascular function and structure and with blood pressure after puberty. In a case-control study design, 34 girls born before term and 32 gender-and age-matched control infants born at term were included. Pulse wave analysis was used to determine aortic pressure profiles and overall arterial compliance. Stiffness of the carotid artery and abdominal aorta was measured with ultrasonography. Pulse wave velocity in the forearm was measured with photoplethysmography. A laser Doppler technique was used to determine skin perfusion before and after transdermal delivery of acetylcholine, an endothelium-dependent vasodilator. It was found that preterm girls had significantly higher brachial and aortic blood pressure, a narrower but less stiff abdominal aorta, and lower peripheral skin blood flow than did control infants. Augmentation index, carotid stiffness, pulse wave velocity, endothelium-dependent vasodilatation, and heart rate were similar in the two groups. In the preterm group, blood pressure and vascular functions showed no association with intrauterine growth retardation or neonatal estradiol levels. In conclusion, preterm girls have higher blood pressure and an increased resistance in the vascular tree after puberty. These findings may have implications for future cardiovascular risk in the growing adult population surviving preterm birth. (Pediatr Res 58: 845-849, 2005) Abbreviations Ach, acetylcholine AGA, appropriate for gestational age AI, augmentation index BMI, body mass index BP, blood pressure CV, coefficient of variation PU, perfusion unit PWV, pulse wave velocity SGA, small for gestational age

Circulation, 2000

Background —Low birthweight (LBW) has been associated with an increased incidence of adult cardio... more Background —Low birthweight (LBW) has been associated with an increased incidence of adult cardiovascular disease. Endothelial dysfunction and loss of arterial elasticity are early markers of hypertension and atherosclerosis. We studied the prevalence of these markers in 44 healthy, prepubertal (age 9±1.3 years) children, 22 with LBW for age. Methods and Results —Endothelial function in skin was tested with the local application of acetylcholine (inducing endothelium-dependent vasodilation) and nitroglycerin (endothelium-independent vasodilation), and local perfusion changes were measured with the laser Doppler method. The elastic properties of the abdominal aorta and common carotid artery were measured with an ultrasonic vessel-wall tracking system. Endothelium-dependent vasodilation was lower in children with LBW (88±33 perfusion units [PU]) than in normal-birthweight controls (133±34 PU, P <0.001). There was no difference in aortic or carotid elasticity between the 2 groups, b...

Circulation, 2003

Background— Low birth weight predisposes to later coronary disease. To further elucidate the mech... more Background— Low birth weight predisposes to later coronary disease. To further elucidate the mechanisms behind this association and their timing, vascular endothelial function—a key factor in early pathophysiology of atherosclerosis—was studied in 54 infants born either before the third trimester or at term. Methods and Results— All subjects were studied at 3 months of postnatal age. A laser-Doppler technique was used to measure skin perfusion before and after transdermal iontophoresis of acetylcholine (ACh; an endothelium-dependent vasodilator). In infants born at term (n=19; birth weight range: 2230 to 4205 g), maximum perfusion after ACh was 109±8 perfusion units (PU, mean±SEM) in normal–birth weight controls compared with 56±13 PU among those who had been small for gestational age at birth ( P <0.01). In infants born preterm (n=35; birth weight range, 722 to 1868 g), ACh induced similar perfusion responses among subjects appropriate for gestational age (113±16 PU) and in thos...

Anesthesia & Analgesia, 1997

PLg to hyperbaric bupivacaine 10.5-12.5 mg increases the intraoperative and early postoperative q... more PLg to hyperbaric bupivacaine 10.5-12.5 mg increases the intraoperative and early postoperative quality of subarachnoid block (1,2). More recently, sufentanil in intrathecal doses of 10, 15, or 20 PLg added to hyperbaric bupivacaine 10.5 mg was equally effective in the perioperative period (3). In analgesia for cesarean section, it is particularly important to use

Acta Paediatrica, 1995

Several studies of the neonatal skin microcirculation published recently (1 -9) used the laser Do... more Several studies of the neonatal skin microcirculation published recently (1 -9) used the laser Doppler (LD) technique to measure skin perfusion changes. LD determinations of the magnitude of skin perfusion changes rely on a well-defined zero point. The zero definition in LD perfusion measurements, however, is complicated. Although the LD output has been found to correlate with skin blood flow, a residual LD signal, greater than the instrumental zero, has been recorded in situations of completely ceased skin blood flow (10). This biological zero (BZ) perfusion signal is believed to be generated by flow independent movements in the tissue, such as Brownian molecular motion (10). On this basis, most investigators measure BZ and subtract it from the total LD output. BZ in the skin of adult humans has been found to exhibit temporal and spatial variations. This can be explained partly by variations in biological factors such as local skin temperature (lo), blood and water content of the skin (1 l), degree of local skin perfusion and vasomotor activity (1 2, 13). In neonates, several of these factors, as well as the skin microvascular density and architecture (14), differ from the conditions in adults. Moreover, the different techniques used to measure BZ (15), the type of LD instrument (10,16) and the geometry of the probe (17) may add to further variation in BZ determinations. There are few and seemingly contradictory data regarding BZ in neonates. Beinder et al. have recently reported that the LD signal from the skin in healthy neonates could be approximated to zero during arterial occlusion (9). This could mean that the concept of BZ is of less significance in neonates than in adults, possibly due to the age-specific differences in the skin microvascular morphology and haemodynamics. However, although systematic documentation is lacking, the LD recordings presented in other neonatal studies show a residual LD signal during obstruction of skin blood flow that clearly differs from zero (3, 4, 6, 8). This flowindependent BZ level may in fact amount to up to 85% of the total LD signal under low perfusion conditions (7). The objective of this article was to present information about the BZ value when applying the LD method in neonatology. The first specific aim was to evaluate the reproducibility and stability of the BZ signal in neonates. Second, we compared BZ values in neonates and adults. Third, the significance of the probe geometry for the BZ value was test.ed by comparing LD recordings performed with a standard and an integrating probe, respectively. As previous neonatal LD studies have been performed in different skin areas, we also compared BZ values obtained from the hand and heel. Finally, two different methods of measuring BZ in neonates were compared.

Acta Obstetricia et Gynecologica Scandinavica, 2005

To investigate whether intrauterine growth retardation (IUGR) and preterm delivery in a poor popu... more To investigate whether intrauterine growth retardation (IUGR) and preterm delivery in a poor population of South Asia was associated with altered maternal and fetal levels of folate, vitamin B12, and homocysteine. Hundred and twenty-eight pregnant women from a low socio-economic strata in the city of Lahore, Pakistan were followed with ultrasound of fetal growth from the 12th week of pregnancy. Blood samples were drawn from the woman and the cord at delivery. Serum was analyzed by a chemiluminescent immunoassay for folate and vitamin B12 and by fluorescence polarization immunoassay for total homocysteine (tHcy). Fourty-six infants showed IUGR. In term, but not preterm, deliveries with IUGR, maternal and cord blood folate levels were half of those in deliveries of normal birth weight infants (P=0.004 and P=0.005). The risk of IUGR was reduced among women with folate levels in the highest quartile (OR 0.31, 95% CI 0.10--0.84). There was no association between vitamin B12 and IUGR. Total homocysteine levels were higher in women delivering IUGR infants (P=0.02). There was an inverse correlation between cord blood folate and tHcy levels (r=-0.26, P=0.006). We also found increased risks for hypertensive illness (OR 3.5, 95% CI 1.4--8.6) and premature delivery (OR 2.5, 95% CI 1.1--6.2) in women in the highest quartile of tHcy. The occurrence of IUGR increased with low maternal and cord concentrations of folate and high maternal levels of tHcy. Further studies on the effects of vitamin B supplementation through pregnancy are warranted.