Medición de gasto cardíaco con ecocardiogafía transtorácica durante anestesia espinal en pacientes sanos / Measurement of cardiac expenditure with transtoracial echocardiography during spinal anesthesia in healthy patients

Introducción: La anestesia espinal produce cambios hemodinámicos como hipotensión (descrita hasta en un 30% de los pacientes) y bradicardia. La fisiología de estos cambios fue estudiada hace años en modelos animales y humanos experimentales. En la actualidad la ecocardiografia transtorácica (ETT) puede ser un monitor no invasivo útil y moderno para estudiar qué ocurre con el gasto cardíaco (GC) luego de un bloqueo subaracnoideo en la práctica clínica diaria. Objetivo : Evaluar el comportamiento del GC con el uso de ETT luego de la instalación de una anestesia espinal. Material y Método : En forma prospectiva se estudiaron pacientes ASA I propuestos para cirugía bajo anestesia espinal. El GC basal se estudió utilizando la ventana paraesternal izquierda donde se midió el diámetro del tracto de salida del ventrículo izquierdo y se le calculó su área. Luego desde la ventana apical en cinco cámaras se midió con Doppler continuo la integral de la velocidad máxima del tracto de salida (IVT). Al multiplicar IVT por su área se obtuvo el volumen de eyección (VE) que se multiplicó por la frecuencia cardíaca (FC), obteniéndose el GC. Luego se instaló la anestesia espinal utilizando una mezcla estandarizada con chirocaína al 0,5% y fentanyl 20 microgramos en un volumen entre 2,5 y 3 ml. El mismo examen ecocardiográfico para medir GC se realizó una vez comprobada la instalación del bloqueo espinal. Resultados : Se estudiaron 52 enfermos; en sólo 2 no hubo ventanas ecocardiográficas satisfactorias. La edad promedio fue de 44,8 ± 11 años. En todos los casos se realizó la cirugía con el bloqueo espinal. El nivel de bloqueo alcanzado fue T6 en un 36,36% de los casos y T4 en un 32,73%. Las variaciones de la presión arterial sistólica, diastólica y frecuencia cardíaca tuvieron una disminución estadísticamente significativa. No se observó una diferencia significativa en el GC previo y posterior a la anestesia espinal. La altura sensitiva máxima del bloqueo subaracnoideo tampoco se correlacionó con la disminución de la presión arterial media (PAM) ni con los parámetros ecocardiograficos. Conclusión : La anestesia espinal produjo disminución de los parámetros hemodinámicos. El uso de ecocardiografía transtorácica intraoperatoria permitió el estudio directo y real de la fisiología cardiovascular y demostrar que pese a la baja de la presión arterial y frecuencia cardíaca el GC tendió a mantenerse, probablemente por otros mecanismos de compensación como aumento de la contractilidad miocárdica y mejoría de la función diastólica. En el futuro la ETT puede ser una herramienta de estudio para evaluar qué ocurre con diferentes fármacos anestésicos y diferentes tipos de pacientes (obstétricas, cardióptas).

Background: Spinal anesthesia produces hemodynamic changes such as hypotension (described in up to 30% of patients) and bradycardia. The physiology of these changes was studied years ago in animal and experimental human models. At present, transthoracic echocardiography (TTE) can be a useful and modern noninvasive monitor to study what happens with cardiac output (CO) after a subarachnoid block in daily clinical practice. Objective : To evaluate the behavior of the CO with the use of TTE after the installation of a spinal anesthesia. Material and Method : We prospectively studied ASA I patients proposed for surgery under spinal anesthesia. The baseline CO was studied using the left parasternal window where the diameter of the left ventricular outflow tract was measured and its area was calculated. Then from the apical window in five chamber view the integral of the maximum velocity of the outflow tract (IVT) was measured with continuous Doppler. When IVT was multiplied by its area, the ejection volume (VE) was multiplied by heart rate (HR), obtaining the CO. Spinal anesthesia was then installed using a mixture standardized with 0.5% chirocaine and 20 micrograms fentanyl in a volume between 2.5 and 3 ml. The same echocardiographic examination was done once the installation of the spinal block was verified. Results : We studied 52 patients, in only 2 there were no satisfactory echocardiographic windows. The average age was 44.8 ± 11 years. In all cases, surgery was performed with the spinal block. The level of blockade reached was T6 in 36.36% of the cases and T4 in 32.73%. The variations of the systolic, diastolic and heart rate had a statistically significant decrease. No significant difference was observed in the CO before and after spinal anesthesia. The maximum sensory height of the subarachnoid block did not correlate with the decrease in MAP or echocardiographic parameters. Conclusion : Spinal anesthesia produced decreased hemodynamic parameters. The use of intraoperative transthoracic echocardiography allowed the direct and real study of cardiovascular physiology and showed that despite the drop in blood pressure and heart rate, the CO tended to remain, probably due to other compensation mechanisms such as increased myocardial contractility and improvement of diastolic function. In the future, TTE can be a study tool to evaluate what happens with different anesthetic drugs and different types of patients (obstetric, cardiopathic).

Characterization of mandibular molar root and canal morphology using cone beam computed tomography and its variability in Belgian and Chilean population samples

PURPOSE: This study used cone-beam computed tomography (CBCT) to characterize mandibular molar root and canal morphology and its variability in Belgian and Chilean population samples. MATERIALS AND METHODS: We analyzed the CBCT images of 515 mandibular molars (257 from Belgium and 258 from Chile). Molars meeting the inclusion criteria were analyzed to determine (1) the number of roots; (2) the root canal configuration; (3) the presence of a curved canal in the cross-sectional image of the distal root in the mandibular first molar and (4) the presence of a C-shaped canal in the second mandibular molar. A descriptive analysis was performed. The association between national origin and the presence of a curved or C-shaped canal was evaluated using the chi-squared test. RESULTS: The most common configurations in the mesial root of both molars were type V and type III. In the distal root, type I canal configuration was the most common. Curvature in the cross-sectional image was found in 25% of the distal canals of the mandibular first molars in the Belgian population, compared to 11% in the Chilean population. The prevalence of C-shaped canals was 10% or less in both populations. CONCLUSION: In cases of unclear or complex root and canal morphology in the mandibular molars, CBCT imaging might assist endodontic specialists in making an accurate diagnosis and in treatment planning.