Arterial dP/dtmax accurately reflects left ventricular contractility during shock when adequate vascular filling is achieved

Background: Peak first derivative of femoral artery pressure (arterial dP/dt max) derived from fluid-filled catheter remains questionable to assess left ventricular (LV) contractility during shock. The aim of this study was to test if arterial dP/dt maxis reliable for assessing LV contractility during various hemodynamic conditions such as endotoxin-induced shock and catecholamine infusion.Methods: Ventricular pressure-volume data obtained with a conductance catheter and invasive arterial pressure obtained with a fluid-filled catheter were continuously recorded in 6 anaesthetized and mechanically ventilated pigs. After a stabilization period, endotoxin was infused to induce shock. Catecholamines were transiently administrated during shock. Arterial dP/dt maxwas compared to end-systolic elastance (Ees), the gold standard method for assessing LV contractility.Results: Endotoxin-induced shock and catecholamine infusion lead to significant variations in LV contractility. Overall, significant correlation (r = 0.51; p < 0.001) but low agreement between the two methods were observed. However, a far better correlation with a good agreement were observed when positive-pressure ventilation induced an arterial pulse pressure variation (PPV) ≤ 11% (r = 0.77; p < 0.001).Conclusion: While arterial dP/dt maxand Ees were significantly correlated during various hemodynamic conditions, arterial dP/dt maxwas more accurate for assessing LV contractility when adequate vascular filling, defined as PPV ≤ 11%, was achieved. © 2012 Morimont et al; licensee BioMed Central Ltd

High levels of B-type natriuretic peptide predict weaning failure from mechanical ventilation in adult patients after cardiac surgery

OBJECTIVE: The failure to wean from mechanical ventilation is related to worse outcomes after cardiac surgery. The aim of this study was to evaluate whether the serum level of B-type natriuretic peptide is a predictor of weaning failure from mechanical ventilation after cardiac surgery. METHODS: We conducted a prospective, observational cohort study of 101 patients who underwent on-pump coronary artery bypass grafting. B-type natriuretic peptide was measured postoperatively after intensive care unit admission and at the end of a 60-min spontaneous breathing test. The demographic data, hemodynamic and respiratory parameters, fluid balance, need for vasopressor or inotropic support, and length of the intensive care unit and hospital stays were recorded. Weaning failure was considered as either the inability to sustain spontaneous breathing after 60 min or the need for reintubation within 48 h. RESULTS: Of the 101 patients studied, 12 patients failed the weaning trial. There were no differences between the groups in the baseline or intraoperative characteristics, including left ventricular function, EuroSCORE and lengths of the cardiac procedure and cardiopulmonary bypass. The B-type natriuretic peptide levels were significantly higher at intensive care unit admission and at the end of the breathing test in the patients with weaning failure compared with the patients who were successfully weaned. In a multivariate model, a high B-type natriuretic peptide level at the end of a spontaneous breathing trial was the only independent predictor of weaning failure from mechanical ventilation. CONCLUSIONS: A high B-type natriuretic peptide level is a predictive factor for the failure to wean from mechanical ventilation after cardiac surgery. These findings suggest that optimizing ventricular function should be a goal during the perioperative period

Automatic detection of ventilatory modes during invasive mechanical ventilation

Background: Expert systems can help alleviate problems related to the shortage of human resources in critical care, offering expert advice in complex situations. Expert systems use contextual information to provide advice to staff. In mechanical ventilation, it is crucial for an expert system to be able to determine the ventilatory mode in use. Different manufacturers have assigned different names to similar or even identical ventilatory modes so an expert system should be able to detect the ventilatory mode. The aim of this study is to evaluate the accuracy of an algorithm to detect the ventilatory mode in use. Methods: We compared the results of a two-step algorithm designed to identify seven ventilatory modes. The algorithm was built into a software platform (BetterCare® system, Better Care SL; Barcelona, Spain) that acquires ventilatory signals through the data port of mechanical ventilators. The sample analyzed compared data from consecutive adult patients who underwent >24 h of mechanical ventilation in intensive care units (ICUs) at two hospitals. We used Cohen’s kappa statistics to analyze the agreement between the results obtained with the algorithm and those recorded by ICU staff. Results: We analyzed 486 records from 73 patients. The algorithm correctly labeled the ventilatory mode in 433 (89 %). We found an unweighted Cohen’s kappa index of 84.5 % [CI (95 %) = (80.5 %: 88.4 %)]. Conclusions: The computerized algorithm can reliably identify ventilatory mode. Electronic supplementary material The online version of this article (doi:10.1186/s13054-016-1436-9) contains supplementary material, which is available to authorized users