Carbonic anhydrase inhibitor acetazolamide shifts synaptic vesicle recycling to a fast mode at the mouse neuromuscular junction

Acetazolamide (AZ), a molecule frequently used to treat different neurological syndromes, is an inhibitor of the carbonic anhydrase (CA), an enzyme that regulates pH inside and outside cells. We combined fluorescent FM styryl dyes and electrophysiological techniques at ex vivo levator auris longus neuromuscular junctions (NMJs) from mice to investigate the modulation of synaptic transmission and vesicle recycling by AZ. Transmitter release was minimally affected by AZ, as evidenced by evoked and spontaneous end-plate potential measurements. However, optical evaluation with FM-styryl dyes of vesicle exocytosis elicited by 50 Hz stimuli showed a strong reduction in fluorescence loss in AZ treated NMJ, an effect that was abolished by bathing the NMJ in Hepes. The remaining dye was quenched by bromophenol, a small molecule capable of diffusing inside vesicles. Furthermore, in transgenic mice expressing Synaptophysin-pHluorin (SypHy), the fluorescence responses of motor nerve terminals to a 50 Hz train of stimuli was decrease to a 50% of controls in the presence of AZ. Immunohistochemistry experiments to evaluate the state of the Myosin light chain kinase (MLCK), an enzyme involved in vesicle recycling, demonstrated that MLCK phosphorylation was much stronger in the presence than AZ than in its absence in 50 Hz stimulated NMJs. We postulate that AZ, via cytosol acidification and activation of MLCK, shifts synaptic vesicle recycling to a fast (kiss-and-run) mode, which changes synaptic performance. These changes may contribute to the therapeutic action reported in many neurological syndromes like ataxia, epilepsy, and migraine.Fil: Bertone Cueto, Nicolás Iván. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Groisman, Ayelén Ivana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Mazzone, Graciela Luján. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cano, Raquel. Universidad de Sevilla; EspañaFil: Tabares, Lucía. Universidad de Sevilla; EspañaFil: Uchitel, Osvaldo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentin

Noninvasive monitoring of lung recruitment maneuvers in morbidly obese patients: the role of pulse oximetry and volumetric capnography

BACKGROUND: We conducted this study to determine whether pulse oximetry and volumetric capnography (VCap) can determine the opening and closing pressures of lungs of anesthetized morbidly obese patients. METHODS: Twenty morbidly obese patients undergoing laparoscopic bariatric surgery with capnoperitoneum were studied. A lung recruitment maneuver was performed in pressure control ventilation as follows: (1) During an ascending limb, the lungs? opening pressure was detected. After increasing positive end-expiratory pressure (PEEP) from 8 to 16 cm H2O, fraction of inspired oxygen (FIO2) was decreased until pulse oximetric arterial saturation (SpO2) was <92%. Thereafter, end-inspiratory pressure was increased in steps of 2 cm H2O, from 36 to a maximum of 50 cm H2O. The opening pressure was attained when SpO2 exceeded 97%. (2) During a subsequent decreasing limb, the lungs? closing pressure was identified. PEEP was decreased from 22 to 10 cm H2O in steps of 2 cm H2O. The closing pressure was determined as the PEEP value at which respiratory compliance decreased from its maximum value. We continuously recorded lung mechanics, SpO2, and VCap. RESULTS: The lungs' opening pressures were detected at 44 (4) cm H2O (median and interquartile range) and the closing pressure at 14 (2) cm H2O. Therefore, the level of PEEP that kept the lungs without collapse was found to be 16 (3) cm H2O. Using respiratory compliance as a reference, receiver operating characteristic analysis showed that SpO2 (area under the curve [AUC] 0.80 [SE 0.07], sensitivity 0.65, and specificity 0.94), the elimination of CO2 per breath (AUC 0.91 [SE 0.05], sensitivity 0.85, and specificity 0.98), and Bohr's dead space (AUC 0.83 [SE 0.06], sensitivity 0.70, and specificity 0.95] were relatively accurate for detecting lung collapse during the decreasing limb of a recruitment maneuver. CONCLUSIONS: Lung recruitment in morbidly obese patients could be effectively monitored by combining noninvasive pulse oximetry and VCap. SpO2, the elimination of CO2, and Bohr's dead space detected the individual's opening and closing pressures.Fil: Tusman, Gerardo. Fundacion Medica de Mar del Plata. Hospital Privado de Comunidad; ArgentinaFil: Groisman, Iván. Fundacion Medica de Mar del Plata. Hospital Privado de Comunidad; ArgentinaFil: Fiolo, Felipe E.. Fundacion Medica de Mar del Plata. Hospital Privado de Comunidad; ArgentinaFil: Scandurra, Adriana. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Martinez Arca, Jorge. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Krumrick, Gustavo. Fundacion Medica de Mar del Plata; ArgentinaFil: Bohm, Stephan H. Swisstom AG; SuizaFil: Suarez-sipmann, Fernando. Instituto de Investigación Santinaria. Fundación Jiménez Díaz; Españ

The sensitivity and specificity of pulmonary carbon dioxide elimination for noninvasive assessment of fluid responsiveness

BACKGROUND: We sought to determine whether the response of pulmonary elimination of CO2 (Vco2) to a sudden increase in positive end-expiratory pressure (PEEP) could predict fluid responsiveness and serve as a noninvasive surrogate for cardiac index (CI).METHODS: Fifty-two patients undergoing cardiovascular surgery were included in this study. By using a constant-flow ventilation mode, we performed a PEEP challenge of 1-minute increase in PEEP from 5 to 10 cm H2O. At PEEP of 5 cm H2O, patients were preloaded with 500 mL IV salinesolution after which a second PEEP challenge was performed. Patients in whom fluid administration increased CI by ≥15% from the individual baseline value were defined as volume responders.Beat-by-beat CI was derived from arterial pulse contour analysis, and breath-by-breath Vco2 data were collected during the protocol. The sensitivity and specificity of Vco2 for detecting thefluid responders according to CI was performed by the receiver operating Characteristic curves.RESULTS: Twenty-one of 52 patients were identified as fluid responders (40%). The PEEP maneuver before fluid administration decreased CI from 2.65 ± 0.34 to 2.21 ± 0.32 L/min/m2 (P = 0.0011) and Vco2 from 150 ± 23 to 123 ± 23 mL/min (P = 0.0036) in responders, whereas the changes in CI and Vco2 were not significant in nonresponders. The PEEP challenge afterfluid administration induced no significant changes in CI and Vco2, in neither responders nor nonresponders. PEEP-induced decreases in CI and Vco2 before fluid administration were well correlated (r2 = 0.75, P < 0.0001) but not thereafter. The area under the receiver operating characteristic curves for a PEEP-induced decrease in ΔCI and ΔVco2 was 0.99, with a 95% confidence interval from 0.96 to 0.99 for ΔCI and from 0.97 to 0.99 for ΔVco2. During the PEEP challenge,a decrease in Vco2 by 11% predicted fluid responsiveness with a sensitivity of 0.90 (95% confidence interval, 0.87?0.93) and a specificity of 0.95 (95% confidence interval, 0.92?0.98).CONCLUSIONS: PEEP-induced changes in Vco2 predicted fluid responsiveness with accuracy in patients undergoing cardiac surgery. (Anesth Analg 2016;122:1404?11)Fil: Tusman, Gerardo. Fundación Medica de Mar del Plata. Hospital Privado de Comunidad; ArgentinaFil: Groisman, Ivan. Fundación Medica de Mar del Plata. Hospital Privado de Comunidad; ArgentinaFil: Maidana, Gustavo A.. Fundación Medica de Mar del Plata. Hospital Privado de Comunidad; ArgentinaFil: Scandurra, Adriana G.. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Electronica; ArgentinaFil: Martinez Arca, Jorge. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Electronica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Bohm, Stephan H.. University Hospital; SueciaFil: Suarez-Sipmann, Fernando. Instituto de Salud Carlos III; Españ