RESUMO
Near-infrared spectroscopy (NIRS) could be a useful continuous, non-invasive technique for monitoring the effect of partial pressure of carbon dioxide (PaCO2) fluctuations in the cerebral circulation during ventilation. The aim of this study was to examine the efficacy of NIRS to detect acute changes in cerebral blood flow following PaCO2 fluctuations after confirming the autoregulation physiology in piglets. Fourteen piglets (<72 h of life) were studied. Mean arterial blood pressure, oxygen saturation, pH, glycemia, hemoglobin, electrolytes, and temperature were monitored. Eight animals were used to evaluate brain autoregulation, assessing superior cava vein Doppler as a proxy of cerebral blood flow changing mean arterial blood pressure. Another 6 animals were used to assess hypercapnia generated by decreasing ventilatory settings and complementary CO2 through the ventilator circuit and hypocapnia due to increasing ventilatory settings. Cerebral blood flow was determined by jugular vein blood flow by Doppler and continuously monitored with NIRS. A decrease in PaCO2 was observed after hyperventilation (47.6±2.4 to 29.0±4.9 mmHg). An increase in PaCO2 was observed after hypoventilation (48.5±5.5 to 90.4±25.1 mmHg). A decrease in cerebral blood flow after hyperventilation (21.8±10.4 to 15.1±11.0 mL/min) and an increase after hypoventilation (23.4±8.4 to 38.3±10.5 mL/min) were detected by Doppler ultrasound. A significant correlation was found between cerebral oxygenation and Doppler-derived parameters of blood flow and PaCO2. Although cerebral NIRS monitoring is mainly used to detect changes in regional brain oxygenation, modifications in cerebral blood flow following experimental PaCO2 changes were detected in newborn piglets when no other important variables were modified.
Assuntos
Hipocapnia , Respiração Artificial , Animais , Animais Recém-Nascidos , Dióxido de Carbono , Circulação Cerebrovascular/fisiologia , Hipercapnia , Oxigênio , SuínosRESUMO
Introduction: Cerebral edema (CE) is the most severe complication of diabetic ketoacidosis (DKA) in children. There is no accurate knowledge of CE pathogenesis and its onset has been related to intravenous rehydration therapy during the initial treatment. Objectives: To estimate the prevalence of CE among DKA patients treated at Hospital General de Niños Pedro de Elizalde with intravenous rehydration and analyze potential risk factors for the development of CE. Materials and methods: Cross-sectional prevalence study and exploratory analysis to compare clinical and laboratory characteristics between patients with and without CE. Patients aged 1-18 years hospitalized with the diagnosis of DKA between January 1st, 2005 and December 31st, 2014 were included. Results: A total of 693 DKA events from 561 medical records were analyzed. Ten patients had evidence of CE (1.44 %; 95 % confidence interval: 0.8-2.6). Patients with CE had higher serum urea levels (p < 0.001), lower carbon dioxide pressure (p < 0.001), and lower serum sodium levels (p < 0.001) than those without CE. Conclusion: The prevalence of CE among DKA patients was 1.44 %, smaller than that reported in our country (1.8 %). The risk factors at admission associated with CE development were high serum urea levels, hyponatremia, and hypocapnia.
Introducción. El edema cerebral (EC) es la complicación más grave de la cetoacidosis diabética (CAD) en niños. La patogénesis del EC no se conoce con exactitud y su aparición ha sido relacionada con la terapia de rehidratación endovenosa en el tratamiento inicial. Objetivos. Estimar la prevalencia de EC en pacientes con CAD tratados en el Hospital General de Niños Pedro de Elizalde mediante rehidratación endovenosa y analizar potenciales factores de riesgo para el desarrollo de EC. Materiales y método. Estudio de diseño transversal para prevalencia y un análisis exploratorio para comparar las características clínicas y de laboratorio entre los pacientes con y sin EC. Se incluyeron pacientes de 1 a 18 años hospitalizados con diagnóstico de CAD desde el 1 de enero de 2005 hasta el 31 de diciembre de 2014. Resultados. Se analizaron 693 episodios de CAD en 561 historias clínicas. En 10 pacientes, se evidenció EC (el 1,44 %; intervalo de confianza del 95 %: 0,8-2,6). Los pacientes con EC presentaron mayor uremia (p < 0,001), menor presión de dióxido de carbono (p < 0,001) y menor natremia (p < 0,001) que aquellos pacientes sin EC. Conclusión. La prevalencia de EC en pacientes con CAD fue del 1,44 %, menor que la reportada en nuestro país (del 1,8 %). Los factores de riesgo al ingresar asociados a su desarrollo fueron la presencia de uremia elevada, hiponatremia e hipocapnia.
Assuntos
Edema Encefálico/etiologia , Cetoacidose Diabética/complicações , Hidratação/efeitos adversos , Adolescente , Argentina , Edema Encefálico/epidemiologia , Criança , Pré-Escolar , Estudos Transversais , Cetoacidose Diabética/epidemiologia , Cetoacidose Diabética/terapia , Feminino , Hidratação/métodos , Humanos , Hipocapnia/epidemiologia , Hiponatremia/epidemiologia , Lactente , Masculino , Prevalência , Fatores de Risco , Ureia/sangueRESUMO
The time constant of the cerebral arterial bed ("tau") estimates how fast the blood entering the brain fills the arterial vascular sector. Analogous to an electrical resistor-capacitor circuit, it is expressed as the product of arterial compliance (Ca) and cerebrovascular resistance (CVR). Hypocapnia increases the time constant in healthy volunteers and decreases arterial compliance in head trauma. How the combination of hyocapnia and trauma affects this parameter has yet to be studied. We hypothesized that in TBI patients the intense vasoconstrictive action of hypocapnia would dominate over the decrease in compliance seen after hyperventilation. The predominant vasoconstrictive response would maintain an incoming blood volume in the arterial circulation, thereby lengthening tau. We retrospectively analyzed recordings of intracranial pressure (ICP), arterial blood pressure (ABP), and blood flow velocity (FV) obtained from a cohort of 27 severe TBI patients [(39/30 years (median/IQR), 5 women; admission GCS 6/5 (median/IQR)] studied during a standard clinical CO2 reactivity test. The reactivity test was performed by means of a 50-min increase in ventilation (20% increase in respiratory minute volume). CVR and Ca were estimated from these recordings, and their product calculated to find the time constant. CVR significantly increased [median CVR pre-hypocapnia/during hypocapnia: 1.05/1.35 mmHg/(cm3/s)]. Ca decreased (median Ca pre-hypocapnia/during hypocapnia: 0.130/0.124 arbitrary units) to statistical significance (p = 0.005). The product of these two parameters resulted in a significant prolongation of the time constant (median tau pre-hypocapnia/during hypocapnia: 0.136 s/0.152 s, p Ë .001). Overall, the increase in CVR dominated over the decrease in compliance, hence tau was longer. We demonstrate a significant increase in the time constant of the cerebral circulation during hypocapnia after severe TBI, and attribute this to an increase in cerebrovascular resistance which outweighs the decrease in cerebral arterial bed compliance.
Assuntos
Velocidade do Fluxo Sanguíneo/fisiologia , Lesões Encefálicas Traumáticas/fisiopatologia , Circulação Cerebrovascular/fisiologia , Hipocapnia/fisiopatologia , Pressão Intracraniana/fisiologia , Ultrassonografia Doppler Transcraniana/métodos , Adolescente , Adulto , Idoso , Pressão Arterial , Pressão Sanguínea , Volume Sanguíneo , Encéfalo/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento , Adulto JovemRESUMO
PURPOSE: Carbon dioxide (CO2) is a potent cerebral vasomotor agent. Despite reduction in CO2 levels (hypocapnia) being described in several acute diseases, there is no clear data on baseline CO2 values in acute stroke. The aim of the study was to systematically assess CO2 levels in acute stroke. MATERIAL AND METHODS: Four online databases, Web of Science, MEDLINE, EMBASE and CENTRAL, were searched for articles that described either partial pressure of arterial CO2 (PaCO2) and end-tidal CO2 (EtCO2) in acute stroke. RESULTS: After screening, based on predefined inclusion and exclusion criteria, 20 studies were retained. There were 5 studies in intracerebral hemorrhage and 15 in ischemic stroke, totalling 660 stroke participants. Acute stroke was associated with a significant decrease in CO2 levels compared to controls. Cerebral haemodynamic studies using transcranial Doppler ultrasonography demonstrated a significant reduction in cerebral blood flow velocities and cerebral autoregulation in acute stroke patients. CONCLUSION: The evidence from this review suggests that acute stroke patients are significantly more likely than controls to be hypocapnic, supporting the value of routine CO2 assessment in the acute stroke setting. Further studies are required in order to evaluate the clinical impact of these findings.
Assuntos
Circulação Cerebrovascular/fisiologia , Hipocapnia/complicações , Hipocapnia/fisiopatologia , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/fisiopatologia , Dióxido de Carbono/sangue , HumanosRESUMO
Central chemoreceptors are highly sensitive neurons that respond to changes in pH and CO2 levels. An increase in CO2/H+ typically reflects a rise in the firing rate of these neurons, which stimulates an increase in ventilation. Here, we present an ionic current model that reproduces the basic electrophysiological activity of individual CO2/H+-sensitive neurons from the locus coeruleus (LC). We used this model to explore chemoreceptor discharge patterns in response to electrical and chemical stimuli. The modeled neurons showed both stimulus-evoked activity and spontaneous activity under physiological parameters. Neuronal responses to electrical and chemical stimulation showed specific firing patterns of spike frequency adaptation, postinhibitory rebound, and post-stimulation recovery. Conversely, the response to chemical stimulation alone (based on physiological CO2/H+ changes), in the absence of external depolarizing stimulation, showed no signs of postinhibitory rebound or post-stimulation recovery, and no depolarizing sag. A sensitivity analysis for the firing-rate response to the different stimuli revealed that the contribution of an applied stimulus current exceeded that of the chemical signals. The firing-rate response increased indefinitely with injected depolarizing current, but reached saturation with chemical stimuli. Our computational model reproduced the regular pacemaker-like spiking pattern, action potential shape, and most of the membrane properties that characterize CO2/H+-sensitive neurons from the locus coeruleus. This validates the model and highlights its potential as a tool for studying the cellular mechanisms underlying the altered central chemosensitivity present in a variety of disorders such as sudden infant death syndrome, depression, and anxiety. In addition, the model results suggest that small external electrical signals play a greater role in determining the chemosensitive response to changes in CO2/H+ than previously thought. This highlights the importance of considering electrical synaptic transmission in studies of intrinsic chemosensitivity.
Assuntos
Dióxido de Carbono/metabolismo , Células Quimiorreceptoras/fisiologia , Locus Cerúleo/fisiologia , Modelos Neurológicos , Potenciais de Ação , Animais , Biologia Computacional , Estimulação Elétrica , Fenômenos Eletrofisiológicos , Humanos , Concentração de Íons de Hidrogênio , Hipercapnia/fisiopatologia , Hipocapnia/fisiopatologia , Locus Cerúleo/citologia , Transmissão SinápticaRESUMO
ResumenIntroducción:La dinámica cardíaca ha sido caracterizada a partir de la teoría de los sistemas dinámicos y la geometría fractal, permitiendo generar metodologías de aplicación clínica.Objetivo:desde los sistemas dinámicos, se desarrollará una metodología de evaluación de los pH y presiones de dióxido de carbono arteriales y venosos para pacientes de la Unidad de Cuidados Intensivos.Materiales y Métodos:se escogieron 10 pacientes con diversas patologías de la Unidad de Cuidados Intensivos Postqui rúrgicos del Hospital Militar Central, registrando pH y presiones de dióxido de carbono arteriales y venosas durante su tiempo de estancia; posteriormente se construyeron atractores, determinando su tipo de trayectoria y estableciendo los valores máximos y mínimos de estas variables en el mapa de retardo.Resultados:se encontró un comportamiento caótico de las variables evaluadas, hallando valores mínimos y máximos de 7,01 y 7,59 para pH arterial, 6,97 y 7,53 para pH venoso, 14,40 y 73,70 para presión arterial de dióxido de carbono, y 19,20 y 97,90 para presión venosa de dióxido de carbono.Conclusiones:La evaluación de los valores máximos y mínimos del atractor en el mapa de retardo constituye un nuevo método, objetivo y reproducible, para la evaluación matemática de cada una de las variables estudiadas, de utilidad para el seguimiento de pacientes en UCI.
SummaryIntroduction:Cardiac dynamics has been characterized from the theory of dynamical systems and fractal geometry, allowing to generate methodologies with clinical application. Objective: from dynamic systems, a methodology for evaluating the arterial and venous pH and dioxide of carbon pressures for patient in Intensive Care Unit will be developed.Materials and Methods:10 patients with various pathologies were selected from Post-surgical Intensive Care Unit of the Central Military Hospital, recording arterial and venous pH and dioxide of carbon pressures of during its stay; attractors were built subsequently, determining the type of path and setting the maximum and minimum values of these variables on the delay map.Results:chaotic behavior of the variables evaluated was found, finding maximum and minimum values of 7,01 and 7,59 for arterial pH values, 6,97 and 7,53 for venous pH, 14,40 and 73,70 for arterial dioxide of carbon pressure, and 19,20 and 97,90 for venous dioxide of carbon pressure.Conclusions:The evaluation of the maximum and minimum values of the attractor on the delay map is a new method, objective and reproducible for the mathematical evaluation of each of the variables studied, useful for monitoring patients in Intensive Care Unit.
Assuntos
Humanos , Pressão Venosa , Gasometria , Dióxido de Carbono , Hipocapnia , Cuidados Críticos , Pressão Arterial , Hipercapnia , Unidades de Terapia IntensivaRESUMO
Antecedentes: El Síndrome de Apnea Hipopnea durante el sueño puede producir trastornos de la conducción cardiaca que pueden conducir a la muerte súbita. Objetivo: Determinar las alteraciones electrocardiográficas y del ritmo cardíaco en sujetos con Síndrome de Apnea-Hipopnea del Sueño (SAHS) y apnea central inducida. Métodos: Evaluación clínica y electrocardiográfica de 50 sujetos aparentemente sanos con SAHS, mediante maniobra de Mueller y con apnea central postespiratoria. Se comparan resultados basales, durante y después de la maniobra mediante análisis de varianza para mediciones repetidas. Resultados: El 60 por ciento de casos fueron varones y 40 por ciento mujeres, con edades promedio de 36 años para varones y de 35,55 años para mujeres (p>0,05). Con la maniobra de Mueller no hubo efecto sobre la duración de la onda P (101,5 ms antes y durante la maniobra, 101,6 ms luego; p>0,05). El complejo QRS tampoco se afectó de manera significativa (90,7 ms antes, 90,9 ms durante y 90,6 ms después; p>0,05). El intervalo QTc aumentó de 413,3 ms antes, a 423,3 ms durante y 423,1 ms después de la maniobra (p0,05), pero la PAM descendió de 89,7 mmHg en el basal a 88,2 mmHg durante el procedimiento y ascendió a 93,6 mmHg después de la misma (p<0,05); no hubo efecto sobre la frecuencia cardiaca y no hubo contracciones supraventriculares...
Background: Obstructive Sleep Apnea can cause cardiac conduction disorders that can lead to sudden death. Objective: To determine the electrocardiographic changes and heart rate in subjects with Obstructive Sleep Apnea and central apnea induced. Methods: Clinical and electrocardiographic evaluation of 50 apparent1y healthy subjects with OSA, using Mueller maneuver and central apnea post-expiratory. Baseline values are compared, during and after the maneuver by analysis of variance for repeated measurements. Results: 60 per cent of cases were male and 40 per cent female mean age of 36 years for males and 35.55 years for females (p>0.05). With Mueller maneuver had no effect on P-wave duration (101.5 msec before and during the maneuver, 101.6 msec following, P>0.05). The QRS wave is not significantly affected (90.7 msec before and 90.6 msec, 90.9 msec after, P>0.05). The QTc raised from 413.3 to 423.3 msec before and 423.1 msec after the maneuver msec (p0.05), but MAP decreased from 89.7 mmHg at baseline to 88.2 mmHg during the procedure and amounted to 93.6 mmHg (p<0.05), there was no effect on heart rate and no supraventricular or ventricular premature contractions with the maneuver. Conclusions: Patients with SAHS QT prolongation and Tp-Tec, and increase in MAP with Mueller maneuver, and only affected the PAM with central apnea postespiratory.
Assuntos
Masculino , Feminino , Humanos , Adulto , Pessoa de Meia-Idade , Idoso , Apneia do Sono Tipo Central , Arritmias Cardíacas , Eletrocardiografia , Hipocapnia/mortalidade , Morte Súbita Cardíaca , Estudo Observacional , Estudos TransversaisRESUMO
OBJECTIVE: To evaluate the association between early hypocarbia and 18- to 22-month outcome among neonates with hypoxic-ischemic encephalopathy. STUDY DESIGN: Data from the National Institute of Child Health and Human Development Neonatal Research Network randomized, controlled trial of whole-body hypothermia for neonatal hypoxic-ischemic encephalopathy were used for this secondary observational study. Infants (n = 204) had multiple blood gases recorded from birth to 12 hours of study intervention (hypothermia versus intensive care alone). The relationship between hypocarbia and outcome (death/disability at 18 to 22 months) was evaluated by unadjusted and adjusted analyses examining minimum PCO(2) and cumulative exposure to PCO(2) <35 mm Hg. The relationship between cumulative PCO(2) <35 mm Hg (calculated as the difference between 35 mm Hg and the sampled PCO(2) multiplied by the duration of time spent <35 mm Hg) and outcome was evaluated by level of exposure (none-high) using a multiple logistic regression analysis with adjustments for pH, level of encephalopathy, treatment group (± hypothermia), and time to spontaneous respiration and ventilator days; results were expressed as odds ratios and 95% confidence intervals. Alternative models of CO(2) concentration were explored to account for fluctuations in CO(2). RESULTS: Both minimum PCO(2) and cumulative PCO(2) <35 mm Hg were associated with poor outcome (P < .05). Moreover, death/disability increased with greater cumulative exposure to PCO(2) <35 mm Hg. CONCLUSIONS: Hypocarbia is associated with poor outcome after hypoxic-ischemic encephalopathy.