Los predictores en el retiro de la ventilación mecánica ¿resultan suficientes para el paciente neurocrítico? / Predictors in the retirement of mechanical ventilation: are they enough to neurocritical patient?

Resumen La ventilación mecánica prolongada incrementa el riesgo de complicaciones; asimismo, el retiro temprano de la misma expone al paciente a los riesgos que tenía antes de iniciarla. Cuando hablamos de ventilación mecánica prolongada y retiro temprano, el equilibrio sigue siendo controvertido, además de ser un tema no resuelto, más aun al referirnos al paciente neurológico. La protección de la vía aérea y evitar mayor afectación de la distensibilidad cerebral son los propósitos de la ventilación mecánica invasiva en el paciente con deterioro neurológico, además de acoplar al paciente con el ventilador, en particular ante patrones respiratorios anormales. De los pacientes que requieren ventilación mecánica en la unidad de cuidados intensivos, alrededor de 20% corresponde a padecimientos neurológicos. El momento apropiado para la extubación puede estar basado en una decisión clínica, que puede considerarse subjetiva; por esta razón, se han propuesto parámetros objetivos para tomar esta decisión, éstos permitirán identificar a los pacientes aptos para realizar prueba de ventilación espontánea con gran posibilidad de éxito. La búsqueda de un parámetro que evalúe el éxito o fracaso de la extubación en el paciente neurológico es un problema no resuelto hasta el momento, por lo que deberá ser tema de más estudios; hasta el día de hoy la Escala de Coma de Glasgow (EC) es la variable asociada con buenos o malos resultados.

Abstract Long mechanical ventilation (MV) increases the risk of complications; moreover, early retirement of it exposes the patient to the risks presented before starting. The balance in speaking of prolonged mechanical ventilation and early retirement remains controversial, besides being an unresolved issue, even more so when speaking of neurological patients. Protection of the airway and prevention of further compromised brain compliance are the purposes of initiating invasive mechanical ventilation in patients with neurological impairment in addition to engaging the patient with particular fan under the presence of abnormal breathing patterns. Of patients requiring mechanical ventilation in the Intensive Care Unit (ICU), about 20% are due to neurological diseases. The appropriate time for extubation may be based on a clinical decision, which may be considered subjective, for this reason objective parameters have been proposed to make such a decision, they will identify candidates to perform test of spontaneous ventilation with great chance of success. The search for a parameter to evaluate the success or failure of extubation in neurological patient is a problem not solved so far, so it should be the subject of further studies, until today the Glasgow Coma Scale (SCG) is the variable associated with good or bad results.

The evaluation of a novel haptic-enabled virtual reality approach for computer-aided cephalometry.

BACKGROUND AND OBJECTIVE: In oral and maxillofacial surgery, conventional radiographic cephalometry is one of the standard auxiliary tools for diagnosis and surgical planning. While contemporary computer-assisted cephalometric systems and methodologies support cephalometric analysis, they tend neither to be practical nor intuitive for practitioners. This is particularly the case for 3D methods since the associated landmarking process is difficult and time consuming. In addition to this, there are no 3D cephalometry norms or standards defined; therefore new landmark selection methods are required which will help facilitate their establishment. This paper presents and evaluates a novel haptic-enabled landmarking approach to overcome some of the difficulties and disadvantages of the current landmarking processes used in 2D and 3D cephalometry. METHOD: In order to evaluate this new system's feasibility and performance, 21 dental surgeons (comprising 7 Novices, 7 Semi-experts and 7 Experts) performed a range of case studies using a haptic-enabled 2D, 2½D and 3D digital cephalometric analyses. RESULTS: The results compared the 2D, 2½D and 3D cephalometric values, errors and standard deviations for each case study and associated group of participants and revealed that 3D cephalometry significantly reduced landmarking errors and variability compared to 2D methods. CONCLUSIONS: Through enhancing the process by providing a sense of touch, the haptic-enabled 3D digital cephalometric approach was found to be feasible and more intuitive than its counterparts as well effective at reducing errors, the variability of the measurements taken and associated task completion times.

High maternal cortisol levels during pregnancy are associated with more psychiatric symptoms in offspring at age of nine - A prospective study from Nicaragua.

Maternal exposure to stress or adversity during pregnancy has been associated with negative health effects for the offspring including psychiatric symptoms. Programming of the hypothalamic-pituitary-adrenal (HPA) axis has been suggested as one mediating process. In order to investigate possible long term effects of stressors during pregnancy, we followed 70 children and their mothers from pregnancy up to nine years aiming to investigate if maternal cortisol levels and distress/exposure to partner violence were associated with child psychiatric symptoms and child cortisol levels at follow-up. Maternal distress was evaluated using The Self Reporting Questionnaire, exposure to partner violence by an instrument from WHO and child psychiatric symptoms with Child Behavior Checklist (CBCL). We adjusted the analyses for gestational week, gender, SES, perinatal data and maternal distress/exposure to partner violence at child age of nine years. Elevated maternal cortisol levels during pregnancy, as a possible marker of maternal stress load, were correlated with higher CBCL-ratings, especially concerning externalizing symptoms. Maternal cortisol levels during pregnancy were not associated with child cortisol levels at child age of nine years. Maternal distress and exposure to partner violence during pregnancy were neither associated with child psychiatric symptoms nor child cortisol levels. To conclude, intrauterine exposure to elevated cortisol levels was associated with higher ratings on offspring psychopathology at nine years of age. The lack of association between maternal cortisol levels during pregnancy and child cortisol levels does not support the hypothesis of fetal programming of the HPA-axis, but reliability problems may have contributed to this negative finding.

Estado nutricional y características del consumo alimentario de la población aguaruna. Amazonas, Perú 2004 / Nutritional status and food consumption patterns in Aguaruna natives. Amazonas, Peru 2004

Objetivos: Identificar el estado nutricional y frecuencia del consumo alimentario de los niños menores de tres años y mujeres en edad fértil (MEF) de la población aguaruna del departamento de Amazonas, Perú 2004. Materiales y métodos: Estudio transversal realizado con una muestra representativa de 478 MEF y 465 niños aguarunas seleccionados por muestreo bietápico probabilístico. Se realizó la toma medidas antropométricas, dosaje de hemoglobina aambos grupos y finalmente una encuesta de consumo de alimentos a una submuestra de 290 hogares. Resultados:La prevalencia de desnutrición crónica en niños fue de 33,4 por ciento. Se encontró asociación estadística entre el distrito de residencia y la desnutrición crónica en niños. La prevalencia de anemia fue de 76,5 por ciento. El 89 por ciento de las MEF presentaronun IMC ideal, sin embargo, la talla promedio de la mujer aguaruna fue de 148 cm. La prevalencia de anemia en MEF fue de 50,2 por ciento. Se listaron más de 100 alimentos locales y foráneos que forman parte de la dieta de las familias aguarunas; sin embargo, sólo se consume diariamente la yuca y plátanos; y con alguna frecuencia semanal el arroz, la carachama, gusano, huevo de gallina y verduras como la chonta y sachaculantro. Conclusiones: La evaluación nutricional indica un déficit nutricional para los niños y la deficiencia de hierro expresada en anemia afecta a la mitad de las MEF y a dos de cada tres niños. Esta situación podría atribuirse, entre otras causas al consumo de una dieta basada principalmenteen yuca y plátanos con escasa presencia de alimentos de origen animal.

Objectives: To identify nutritional status and alimentary patters in less than three-year-old children and fertile women in Aguaruna natives in Amazonas department, Peru, 2004. Materials and methods: Cross-sectional study performed using a representative sample composed of 478 fertile women and 465 children, who were previously selected using a probabilistic two-staged sampling procedure. Anthropometric measurements and hemoglobin determinations were performed in both groups, and a food consumption survey was carried out in a sample comprising 290 households. Results: The prevalence of chronic malnutrition was 33,4%. A statistical association between district of residence and chronic malnutrition in children was found. The prevalence of anemia was 76,5%. 89% of fertile women had an ideal body mass index; however, average height in Aguaruna women was 148 cm. The prevalence of anemia in fertile women was 50,2%. A list comprising more than 100 local and foreign foods eaten by Aguaruna people as part of their usual diet was elaborated; however, only cassava and bananas are eaten daily; and rice, carachama (a river fish), worms, eggs and certain native vegetables (chonta and sachaculantro) are eaten weekly. Conclusions: This assessment indicates there are nutritional deficits in children; and iron deficiency anemia affects half of fertile women and two of every three children. This situation may be attributed to consumption of diet based mainly in cassava and bananas, with insufficient poor animal protein contents.

Determinants of heart rate variability in obstructive sleep apnea syndrome during wakefulness and sleep.

Heart rate variability (HRV) is mediated by at least three primary mechanisms: 1) vagal feedback from pulmonary stretch receptors (PSR), 2) central medullary coupling between respiratory and cardiovagal neurons (RCC), and 3) arterial baroreflex (ABR)-induced fluctuations. We employed a noninvasive experimental protocol in conjunction with a minimal model to determine how these sources of HRV are altered in obstructive sleep apnea syndrome (OSAS). Respiration, heart rate, and blood pressure were monitored in eight normal subjects and nine untreated OSAS patients in relaxed wakefulness and stage 2 and rapid eye movement sleep. A computer-controlled ventilator delivered inspiratory pressures that varied randomly from breath to breath. Application of the model to the corresponding subject responses allowed the delineation of the three components of HRV. In all states, RCC gain was lower in OSAS patients than in normal subjects (P < 0.04). ABR gain was also reduced in OSAS patients (P < 0.03). RCC and ABR gains increased from wakefulness to sleep (P < 0.04). However, there was no difference in PSR gain between subject groups or across states. The findings of this study suggest that the adverse autonomic effects of OSAS include impairment of baroreflex gain and central respiratory-cardiovascular coupling, but the component of respiratory sinus arrhythmia that is mediated by lung vagal feedback remains intact.

Closed-loop minimal model analysis of the cardiovascular response to transient arousal from sleep in healthy humans.

In a previous work we reported discrepancies in the cardiovascular response to arousal from NREM sleep between OSAS patients and healthy controls. The long lasting cardiac sympathetic increase observed in normals was not present in the OSAS group, whereas the peripheral vasculature reaction was similar between the two groups. Analysis of REM arousal revealed that there was a similar temporary cardiac sympathetic impairment in the control group. In this work we have implemented a model-based time domain system identification method to assess the mechanisms involved in this reaction to arousal from both NREM and REM sleep in a group of healthy subjects. The use of time-varying techniques has enabled us to characterize the arousal reaction by analyzing the change in shape of the impulse responses of the system. The mechanisms regulating respiration and vascular effects on heart rate (respiratory sinus arrhythmia or RSA and arterial baroreflex or ABR, respectively) were the most affected by NREM arousal, likely as a result of the return of the wakefulness stimulus. The effect observed on the cardiac influence on the vasculature (circulatory dynamics, CID) was attributed to a change in the dominant mechanism prevailing in its dynamics.

Occurrence, co-occurrence and topographic distribution of choline acetyl transferase, Met-enkephalin and neurotensin in the stellate ganglion of the cat.

The presence of the classical ganglionic transmitter acetylcholine (ACh), its occurrence and possible co-occurrence with the neuromodulator peptides methionine enkephalin (Met-ENK) and neurotensin (NT), as well as the possible coexistence of these peptides in the preganglionic axon terminals of the cat stellate ganglia were investigated with light and confocal microscopy using immunofluorescence. Choline acetyltransferase (ChAT), Met-ENK, and NT immunoreactivity was detected with light microscopy in axon terminals near tyrosine hydroxylase (TH) immunoreactive (IR) cells. Cell bodies immunopositive for ChAT or Met-ENK were also detected and were TH-negative or TH-positive. Denervation by sectioning preganglionic axons produced two effects: the almost complete elimination of IR fibers and an increase in the number of ChATIR and Met-ENKIR cell bodies, together with the appearance of NTIR cell bodies. Preganglionic ChATIR fibers and boutons form a dense network throughout the entire ganglion, with a homogeneous regional distribution. ChAT, Met-ENK, and NT are essentially stored in different nerve endings, although a low level of co-occurrence was detected. NTIR and Met-ENKIR networks of boutons were observed to have independent and somewhat complementary regional distributions. Further analysis with simultaneous triple labeling for NT, Met-ENK, and TH, and confocal microscopy showed fibers and boutons containing Met-ENK or NT reached distinct neurons separately, or both converge onto the same cells. This finding suggests that modulation (the facilitation-inhibition balance) of ganglionic transmission is achieved mainly by the selective and complementary innervation of boutons containing NT (facilitation) and Met-ENK (inhibition) and only rarely by terminals which coexpress both peptides.

The use of a bioactive skin substitute decreases length of stay for pediatric burn patients.

BACKGROUND: To optimize burn care for children, the authors introduced a protocol incorporating the use of a bioactive skin substitute, TransCyte (Advanced Tissue Sciences, La Jolla, CA). This study was designed to determine whether this management plan was safe, efficacious, and decreased hospital inpatient length of stay (LOS) compared with conventional burn management in children. METHODS: All pediatric burns greater than 7% total body surface area (TBSA) that occurred after October 1999 underwent wound closure with TransCyte (n = 20). These cases were compared with the previous 20 consecutive burn cases greater than 7% TBSA that received standard therapy. Standard therapy consisted of application of antimicrobial ointments and hydrodebridement. The following information was obtained: burn mechanism, age, size of burn, requirement of autograft, and LOS. Data were analyzed using the student's t test. RESULTS: Data for age, percent TBSA burn and LOS are reported as means +/- SEM. The children who received standard therapy were 2.99 +/- 0.7 years compared with those receiving TransCyte were 3.1 +/- 0.8 years. There was no difference between the treatment groups with regard to percent TBSA burn: standard therapy, 14.3 +/- 1.4% TBSA versus TransCyte, 12.7 +/- 1.3% TBSA. There was no difference in the type of burns in each group, the majority were liquid scald type, 70% in the standard therapy group versus 90% in the TransCyte group. Only 1 child in the TransCyte group required autografting (5%) compared with 7 children in the standard therapy group (35%). Children treated with TransCyte had a statistically 6 significant decreaed LOS compared with those receiving standard therapy, 5.9 +/- 0.9 days versus 13.8 +/- 2.2 days, respectively (P =.002). CONCLUSIONS: This is the first study using TransCyte in children. The authors found that this protocol of burn care was safe, effective, and significantly reduced the LOS. This new approach to pediatric burn care is effective and improves the quality of care for children with burns.

Decreased CSF pH at ventral brain stem induces widespread c-Fos immunoreactivity in rat brain neurons.

Physiological evidence has indicated that central respiratory chemosensitivity may be ascribed to neurons located at the ventral medullary surface (VMS); however, in recent years, multiple sites have been proposed. Because c-Fos immunoreactivity is presumed to identify primary cells as well as second- and third-order cells that are activated by a particular stimulus, we hypothesized that activation of VMS cells using a known adequate respiratory stimulus, H(+), would induce production of c-Fos in cells that participate in the central pH-sensitive respiratory chemoreflex loop. In this study, stimulation of rostral and caudal VMS respiratory chemosensitive sites in chloralose-urethane-anesthetized rats with acidic (pH 7.2) mock cerebrospinal fluid induced c-Fos protein immunoreactivity in widespread brain sites, such as VMS, ventral pontine surface, retrotrapezoid, medial and lateral parabrachial, lateral reticular nuclei, cranial nerves VII and X nuclei, A(1) and C(1) areas, area postrema, locus coeruleus, and paragigantocellular nuclei. At the hypothalamus, the c-Fos reaction product was seen in the dorsomedial, lateral hypothalamic, supraoptic, and periventricular nuclei. These results suggest that 1) multiple c-Fos-positive brain stem and hypothalamic structures may represent part of a neuronal network responsive to cerebrospinal fluid pH changes at the VMS, and 2) VMS pH-sensitive neurons project to widespread regions in the brain stem and hypothalamus that include respiratory and cardiovascular control sites.

Release-depletion and receptor-mediated neuronal internalization of endogenous neurotensin in the stellate ganglion of the cat.

The release and depletion of neurotensin in sympathetic preganglionic axon terminals and internalization in principal ganglion cells were investigated in the cat stellate ganglion by means of combined immunohistochemical staining, image analysis and confocal microscopy. Neurotensin stored in preganglionic boutons was released by 40 or 5 Hz electrical stimulation of preganglionic nerves, being depleted to 7.4 and 19.2% of control levels by continuous stimulation lasting 20 or 160 min (both stimuli delivered 48,000 pulses). Once released, neurotensin was internalized by the principal ganglion cells as evidenced by a ring of bright spot-like granules in the perinuclear region indicating the sites of intracellular neurotensin accumulation. Neurotensin internalization was time-dependent, thus, different content was found when the time between the end of stimulation and start of perfusion was varied. The onset of neurotensin internalization appeared in the first minutes, intracellular accumulation was evident at 20 min, maximal internalization occurred at 120 min and, 24 h later internalized neurotensin content had faded. Internalization was partially blocked by the nonpeptide neurotensin antagonist SR48692. These data provide evidence of presynaptic neurotensin release and depletion by electrical stimulation with varied frequencies. They also provide evidence for in situ receptor-mediated internalization of endogenously released neurotensin, raising the possibility that internalization may represent, in addition to some kind of turnover dynamics, an important part of the mechanisms of neuropeptide signaling.