Índice de colapsabilidad de la vena cava inferior como predictor de hipotensión intraoperatoria / Inferior vena cava collapsibility index of the as a predictor of intraoperative hypotension

OBJECTIVE: To evaluate the lower vena cava Collapse Index (CI) as a predictor parameter of hypotensive episodes after general anesthesia induction in ASA I and II patients who were scheduled for elective surgery. MATERIALS AND METHODS: A prospective, observational and simple blind study was designed. A sample of 80 patients was recruited. In the preoperative stage, they underwent protocolarized sedation and CI was obtained. Prior to induction, the baseline values ​​of heart rate, non-invasive mean arterial pressure and continuous electrocardiographic tracing in DII were noted. In the post-orotracheal intubation stage, the aforementioned hemodynamic monitoring variables were recorded manually for 10 minutes. RESULTS: The data of 78 individuals are presented. After anesthetic induction, 8 (10.3%) patients developed hypotension. The adjustment of the univariate logistic regression model for CI shows a good diagnostic capacity, with the area under the ROC curve equal to 0.76. The chance of presenting hypotension is increased by 62% by increasing the CI by 5 points (p = 0.003). Regarding the negative predictive value, we found that with values ​​corresponding to the cutoff points between 39% and 46%, a probability of at least 93.1% of not presenting hypotension was obtained. The optimal cutoff point of the CI to predict hypotension is estimated at 43%, with a sensitivity of 62.5% and a specificity of 92.9%. CONCLUSION: A lower IC was associated with a lower probability of developing intraoperative hypotension. The use of this tool could be useful to anticipate which patients will be prone to intra-surgical hypotension.

OBJETIVO: Evaluar el índice de colapsabilidad (IC) de la vena cava inferior (VCI) como predictor de episodios hipotensivos posinducción de anestesia general en cirugía electiva de pacientes ASA I y II. MATERIALES Y MÉTODOS: Se diseñó un estudio prospectivo, observacional y simple ciego. Se reclutó una muestra de 80 pacientes. En etapa preoperatoria fueron sometidos a una sedación protocolizada y se obtuvo el IC. Previo a la inducción, se anotaron los valores basales de la frecuencia cardíaca, la presión arterial media y el trazado electrocardiográfico continuo en DII. Posintubación orotraqueal, se registraron manualmente las variables hemodinámicas mencionadas durante 10 minutos. RESULTADOS: Se presentan datos de 78 individuos. Luego de la inducción, 8 (10,3%) pacientes desarrollaron hipotensión. El ajuste del modelo de regresión logística univariado para IC muestra una buena capacidad diagnóstica, siendo el área bajo la curva ROC igual a 0,76. La chance de presentar hipotensión se incrementa en un 62% al aumentar el IC en 5 puntos (p = 0,003). En cuanto al valor predictivo negativo, encontramos que con valores correspondientes a los puntos de corte entre 39% y 46%, se obtenía una probabilidad de 93,1% de no presentar hipotensión. El punto de corte óptimo del IC para predecir hipotensión se estima en 43%, con una sensibilidad del 62,5% y una especificidad del 92,9%. CONCLUSIÓN: Un menor IC se asoció con una menor probabilidad de desarrollar hipotensión intraoperatoria. El uso de esta herramienta podría ser de utilidad para anticipar qué pacientes serán propensos a hipotensión intraquirúrgica.

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 saline solution 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 the fluid 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/m (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 after fluid 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 (r = 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.

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.