Etiology and Mechanism of Intermittent Hypoxemia Episodes in Spontaneously Breathing Extremely Premature Infants.

OBJECTIVE: To evaluate the mechanisms leading to intermittent hypoxemia (IH) episodes in spontaneously breathing extremely premature infants at 32 weeks and 36 weeks postmenstrual age (PMA). METHODS: We studied spontaneously breathing premature infants born at 23-28 weeks of gestational age who presented with IH episodes while on noninvasive respiratory support at 32 or 36 weeks PMA. Daytime recordings of arterial oxygen saturation (SpO2), esophageal pressure, respiratory inductive plethysmography of the abdomen, chest wall, and their sum were obtained during 4 hours at 32 weeks and 36 weeks PMA. IH episodes (SpO2 <90% for ≥5 seconds) and severe IH episodes (SpO2 < 80% for ≥5 seconds) were classified as resulting from apnea, active exhalation and breath holding, reduced tidal volume (VT), or reduced respiratory rate (RR) during the preceding 60 seconds. RESULTS: Fifty-one infants with a mean gestational age of 25.9 ± 1.5 weeks and a mean birth weight of 846 ± 185 g were included. Of these, 31 and 41 were included in the analysis at 32 weeks and 36 weeks PMA, respectively. At both 32 weeks and 36 weeks PMA, greater proportions of all IH episodes and severe IH episodes were associated with active exhalation and breath holding than with apnea, reduced RR, or reduced VT. The severity and duration of the IH episodes did not differ between mechanisms. CONCLUSIONS: In this group of premature infants, the predominant mechanism associated with daytime IH was active exhalation and breath holding. This etiology is more closely associated with behavioral factors than abnormal respiratory control and can have implications for prevention.

Identificación del nervio frénico con tomografía computarizada cardiaca multidetector / Phrenic nerve identification with cardiac multidetector computed tomography

La crioablación con balón de las venas pulmonares es una técnica novedosa que se ha demostrado útil para prevenir las recurrencias de la fibrilación auricular paroxística y persistente. Una de las complicaciones más relevantes del procedimiento es la parálisis del nervio frénico derecho. Se ha descrito recientemente la utilidad de la tomografía computarizada multidetector para localizar el recorrido de la arteria y el nervio frénico y predecir el riesgo de parálisis frénica durante la crioablación, según la distancia del paquete vasculonervioso frénico derecho al ostium de la vena pulmonar superior derecha. A 55 pacientes consecutivos con fibrilación auricular paroxística (media de edad 52±12 años) sometidos a crioablación con balón, se les realizó estudio previo con tomografía computarizada multidetector para medir el tamaño de las venas pulmonares. Se pudo identificar algún fragmento de la arteria pericardiofrénica derecha en 10 pacientes (20%), con una longitud media de 25 (7-68) mm (AU)

Cryoballoon ablation of the pulmonary veins is a new technique that has proven useful in preventing paroxysmal and persistent atrial fibrillation recurrence. One of the most serious complications of this method is right phrenic nerve palsy. The usefulness of multidetector computed tomography to locate the right phrenic nerve and artery and predict the risk of phrenic nerve palsy during cryoablation according to the distance between the right phrenic neurovascular bundle and the right superior pulmonary vein ostium has recently been described. Fifty-five consecutive patients with paroxysmal atrial fibrillation (52±12 years) underwent balloon cryoablation, following multidetector computed tomography to measure the pulmonary veins. We were able to identify segments of the right pericardiacophrenic artery (mean length 25mm [range 7-68mm]) in only 10 patients (20%) (AU)

[Phrenic nerve identification with cardiac multidetector computed tomography]. / Identificación del nervio frénico con tomografía computarizada cardiaca multidetector.

Cryoballoon ablation of the pulmonary veins is a new technique that has proven useful in preventing paroxysmal and persistent atrial fibrillation recurrence. One of the most serious complications of this method is right phrenic nerve palsy. The usefulness of multidetector computed tomography to locate the right phrenic nerve and artery and predict the risk of phrenic nerve palsy during cryoablation according to the distance between the right phrenic neurovascular bundle and the right superior pulmonary vein ostium has recently been described. Fifty-five consecutive patients with paroxysmal atrial fibrillation (52 ± 12 years) underwent balloon cryoablation, following multidetector computed tomography to measure the pulmonary veins. We were able to identify segments of the right pericardiacophrenic artery (mean length 25 mm [range 7-68 mm]) in only 10 patients (20%).

Mankind's first natural stem cell transplant.

The timing of the umbilical cord clamping at birth is still controversial. In the modern era of medicine, the cord has been clamped early to facilitate resuscitation and stabilization of infants. However, recently delayed cord clamping has been supported by physicians because it allows for the physiological transfer of blood from the placenta to the infant. Many clinical studies have revealed that the delayed cord clamping elevates blood volume and haemoglobin and prevents anaemia in infants. Moreover, since it was known that umbilical cord blood contains various valuable stem cells such as haematopoietic stem cells, endothelial cell precursors, mesenchymal progenitors and multipotent/pluripotent lineage stem cells, the merit of delayed cord clamping has been magnified. In this review, we discuss the advantages and disadvantages of delayed cord clamping at birth. We highlight the importance of delayed cord clamping in realizing mankind's first stem cell transfer and propose that it should be encouraged in normal births.

Calidad bacteriológica del agua utilizada en clínicas odontológicas / Bacteriological quality of the water used in dental clinics

Se evaluó la calidad bacteriológica del agua de 8 clínicas odontológicas de la FESI UNAM, determinándose Coliformes fecales y Coliformes totales, por medio de la técnica de filtro de membrana. Realizándose de 2 a 4 muestreos semanales, en cada clínica se tomaron muestras de la jeringa triple y el llena vasos de 10 unidades dentales, además del suministro de entrada. Se tomaron 188 muestras, a cada una se le efectuaron 2 determinaciones (Coliformes totales y Coliformes fecales), haciendo un total de 376 análisis. De las muestras analizadas únicamente 8 presentaron contaminación bacteriana; 7 correspondieron al primer muestreo realizado en la Clínica de Acatlán después de un periodo vacacional; la contaminación fue consecuencia del prolongado estancamiento del agua debido a la inactividad clínica, lo cual contribuyó a la presencia de Coliformes fecales y Coliformes totales. Posteriormente a ese periodo vacacional los siguientes muestreos salieron negativos. En la clínica Ecatepec una muestra proveniente de una unidad dental que contaba con el sistema Flush, también resultó positiva para Coliformes totales. En las clínicas odontológicas se atiende anualmente más de 30,000 pacientes de diversas edades y estados de salud, a quienes se efectúan diversos tratamientos odontológicos que van desde extracciones hasta cirugías maxilofaciales.

The bacteriological quality of the water of 8 dental clinics of FESI UNAM, was evaluated determining total and fecal coliforms, by means of the technique of membrane filter. They were made 2 to 4 weekly samplings, and in each clinic, were taken samples of the triple syringe and the flood glasses of 10 dental units, in addition water tap. 188 samples were taken and both determinations of coliforms were made to each sample, making a total of 376 analyses. From all the analyzed samples only 8 presented bacterial pollution; 7 of them, corresponded to the first sampling made in Acatlán clinic after a vacational period; the pollution was consequence of the prolonged water stagnation due to the clinical inactivity, which contributed to the presence of fecal and total coliforms. After vacations the following samplings were negatives. In Ecatepec clinic one sample which came from a dental unit that with a Flush system, also was positive for total coliforms. The dental clinics, annually give service of more than 30.000 patients of diverse ages and states of health, offering diverse types of dental treatments since extractions to some maxilofacial surgeries. It was conclude that in general, the bacteriological quality of the water used in the dental clinics is good, which is very important, because water makes directly contact with the mucous membrane of oral cavity, dental structures, blood and saliva of the patient, avoiding infectious processes that could put in risk their integral health.

Ontogeny of retrograde labeled chemoafferent neurons in the newborn rat nodose-petrosal ganglion complex: an ex vivo preparation.

Hypoxic chemosensitivity of the peripheral arterial chemoreceptors in the carotid body is developmentally regulated. Essential neural elements of the chemotransducing unit in the carotid body consist of the Type I cell that depolarizes and releases neurotransmitters in response to hypoxemia and the chemoafferent fibers which form synapses with Type I cells, contain postsynaptic receptors and have cell bodies in the petrosal ganglion. While many properties of the Type I cells have been characterized during postnatal development, less is known about the effect of development on the number and properties of the chemoafferents since localization of the cell bodies of chemoafferents are intermingled with the cell bodies of other sensory neurons that innervate the upper airway. Here, we describe a novel ex vivo preparation that we have developed to retrogradely label cell bodies of chemoafferents in the petrosal ganglion with rhodamine dextran. With this technique, in newborn rats, we show that there is a three-fold increase in retrogradely labeled neurons in the nodose-petrosal ganglion complex from postnatal day (PND) 3-7 with a three-fold decrease by PND 14 (P < 0.001, ANOVA). Furthermore, greater than 85% of these retrogradely labeled neurons co-express TH mRNA in all age groups. This novel ex vivo technique circumvents many of the technical difficulties encountered with retrogradely labeling chemoafferents in small newborn animals in vivo, and provides a method to identify and characterize essential neural components of the chemotranductive unit of the peripheral arterial chemoreceptors.

Maturation of peripheral arterial chemoreceptors in relation to neonatal apnoea.

Apnoea and periodic breathing are the hallmarks of breathing for the infant who is born prematurely. Sustained respiration is obtained through modulation of respiratory-related neurons with inputs from the periphery. The peripheral arterial chemoreceptors, uniquely and reflexly change ventilation in response to changes in oxygen tension. The chemoreflex in response to hypoxia is hyperventilation, bradycardia and vasoconstriction. The fast response time of the peripheral arterial chemoreceptors to changes in oxygen and carbon dioxide tension increases the risk of more periodicity in the breathing pattern. As a result of baseline hypoxaemia, peripheral arterial chemoreceptors contribute more to baseline breathing in premature than in term infants. While premature infants may have an augmented chemoreflex, infants who develop bronchopulmonary dysplasia have a blunted chemoreflex at term gestation. The development of chemosensitivity of the peripheral arterial chemoreceptors and environmental factors that might cause maldevelopment of chemosensitivity with continued maturation are reviewed in an attempt to help explain the physiology of apnoea of prematurity and the increased incidence of sudden infant death syndrome (SIDS) in infants born prematurely and those who are exposed to tobacco smoke.