A comparison of the NeurOs® and the INVOS 5100C® cerebral oximeter during variations of the partial pressure of carbon dioxide and fractional inspiratory concentration of oxygen.

This prospective method comparison study compared cerebral oxygen saturation (ScO2) measurement performance of the new cerebral oximeter (NeurOs®, Mespere LifeSciences, Ontario, Canada) in comparison to the established INVOS 5100C® (Medtronic, Boulder, USA) cerebral oximeter. We performed measurements during different levels of carbon dioxide pressure (PaCO2) during hyper- and hypoventilation and different levels of arterial oxygen saturation (SaO2) induced by variation of the inspiratory fraction of oxygen (FiO2). 59 anesthetized cardiac and vascular surgical patients were studied during hemodynamically stable conditions. Two versions of the NeurOs® oximeter were used in 39 and 20 patients, respectively: an older version with one bi-hemispherical sensor attached to the midline of the forehead and a newer version with two sensors that were attached to the left and right forehead. Alternating measurements of ScO2 with the INVOS® oximeter (bifrontal sensors) and the NeurOs® oximeter were performed during baseline conditions and after PaCO2 had been randomly in- and decreased by changes in ventilation (constant FiO2) and SaO2 had been randomly modified by variations in FiO2 (constant PaCO2). Employing the most recent NeurOs® version, measurements were additionally performed in a default and a high penetration mode. Bland-Altman analyses revealed comparable bias and limits of agreement for INVOS® and NeurOS® measurements during baseline conditions when using the bi-hemispherical sensor and the version with two sensors, respectively. Consequently, further analyses were performed on the pooled data of 59 patients. Bland-Altman analysis for repeated measurements revealed a bias of - 0.5%, a lower limit of agreement of - 16.3% (95% CI - 19.6 to - 13.7%) and an upper limit of agreement of 15.4% (95% CI 12.8 to 18.8%) during variations of PaCO2. The respective analysis during changes in SaO2 induced by variation of the FiO2 revealed a bias of - 0.8%, a lower limit of agreement of - 16.3% (95% CI - 19.7 to - 13.6%) and an upper limit of agreement of 14.7% (95% CI 12.1 to 18.2%). Both analyses showed a proportional error. No significant differences in ScO2 were observed during measurements with the bi-frontal sensors in the default as well as the high penetration mode. The ScO2 measurement performance of the NeurOs® cerebral oximeter is not interchangeable with the INVOS® cerebral oximeter during variations of ventilation and oxygenation in elective cardiac or vascular surgical patients. The lack of reactivity to changes in ventilation (by variation of PaCO2) and oxygen delivery (by variation of FiO2) question the reliability of NeurOs® measurements to reflect changes in cerebral blood flow and cerebral oxygen balance. This holds true not only for different sensor positions at the forehead but also for different modes of penetration.

[Cardioanaesthesiology - What's new?] / Kardioanästhesie ­ Was gibt es Neues?

The still unchanged high morbidity and mortality of patients undergoing complex cardiac surgical procedures as well as developments in minimally invasive cardiac surgery are not only an ongoing challenge for all working in cardiac anaesthesia but also a chance for further developing this anaesthetic subdiscipline. Alongside the presentation of a case report, the present article gives an overview about recent developments in inotropic therapy, monitoring, the rational use of mechanical circulatory support, volume therapy, sedation, analgesia, and point-of-care coagulation monitoring in cardiac anaesthesia.

Still a place for aortic counterpulsation in cardiac surgery and patients with cardiogenic shock?

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2021. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2021 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from https://link.springer.com/bookseries/8901 .

The effects of systemic oxygenation on cerebral oxygen saturation and its relationship to mixed venous oxygen saturation: A prospective observational study comparison of the INVOS and ForeSight Elite cerebral oximeters.

PURPOSE: The present study aimed to test the hypothesis that cerebral oxygen saturation (ScO2) measurements with the INVOS-5100-C and the ForeSight-Elite cerebral oximeters vary in their correlation with mixed venous oxygen saturation (SvO2) upon changes in systemic oxygenation in extubated cardiac surgical patients. Additionally, we aimed to elucidate whether the ScO2 measurements of both devices can be used interchangeably to detect reduced SvO2. METHODS: Forty-eight spontaneously breathing patients extubated after cardiac surgery were included in this prospective observational study. The patients were exposed to both high (10 oxygen L·min-1 via face mask) and low (room air) inspiratory oxygen concentrations. Bi-hemispherical ScO2 was determined with the INVOS and ForeSight Elite cerebral oximeters. The SvO2 was measured with a pulmonary artery catheter. RESULTS: Significant changes in oxygen delivery, ScO2 (by both cerebral oximeters), and SvO2 were observed upon variation of oxygenation. The minimum mean (standard deviation) ScO2 (ScO2min) using the INVOS and ForeSight did not differ significantly during high oxygen delivery [63.1 (8.6) % vs 65.8 (4.7) %, respectively; P = 0.07], but during low oxygen delivery, the INVOS value was significantly lower than that of the ForeSight oximeter [56.7 (8.9) % vs 61.3 (4.4) %, respectively; P = 0.003]. Both devices differed in the correlation between ScO2min and SvO2 for the combined oxygenation data (0.59, INVOS vs 0.28, ForeSight; correlation difference, 0.31; Bonferroni-adjusted 95% confidence interval [CI], 0.08 to 0.54; P = 0.008). The receiver-operating curve analysis revealed an area under the curve of 0.83 (95% CI, 0.74 to 0.9; P = 0.005) for detecting an SvO2 below 50% by ScO2min with the INVOS and 0.51 (95% CI, 0.41 to 0.62; P = 0.92), respectively, with the ForeSight. CONCLUSIONS: These findings suggest that the cerebral oximeters tested react differently to variations in systemic oxygenation and in their relationship with SvO2 and thus give different information on cardiopulmonary function. These findings raise doubt about whether these devices should be used interchangeably.

Preoperative plasma growth-differentiation factor-15 for prediction of acute kidney injury in patients undergoing cardiac surgery.

BACKGROUND: Growth-differentiation factor-15 (GDF-15) is an emerging humoral marker for risk stratification in cardiovascular disease. Cardiac-surgery-associated acute kidney injury (CSA-AKI), an important complication in patients undergoing cardiac surgery, is associated with poor prognosis. The present secondary analysis of an observational cohort study aimed to determine the role of GDF-15 in predicting CSA-AKI compared with the Cleveland-Clinic Acute Renal Failure (CC-ARF) score and a logistic regression model including variables associated with renal dysfunction. METHODS: Preoperative plasma GDF-15 was determined in 1176 consecutive patients undergoing elective cardiac surgery. Patients with chronic kidney disease stage 5 were excluded. AKI was defined according to Kidney-Disease-Improving-Global-Outcomes (KDIGO) - creatinine criteria. The following variables were screened for association with development of postoperative AKI: age, gender, additive Euroscore, serum creatinine, duration of cardiopulmonary bypass, duration of surgery, type of surgery, total circulatory arrest, preoperative hemoglobin, preoperative oxygen-supplemented cerebral oxygen saturation, diabetes mellitus, hemofiltration during ECC, plasma GDF-15, high sensitivity troponin T (hsTNT), and N-terminal prohormone of B-type natriuretic peptide (NTproBNP). RESULTS: There were 258 patients (21.9 %) with AKI (AKI stage 1 (AKI-1), n = 175 (14.9 %); AKI-2, n = 6 (0.5 %); AKI-3, n = 77 (6.5 %)). The incidence of AKI-1 and AKI-3 increased significantly from the lowest to the highest tertiles of GDF-15. In logistic regression, preoperative GDF-15, additive Euroscore, age, plasma creatinine, diabetes mellitus, and duration of cardiopulmonary bypass were independently associated with AKI. Inclusion of GDF-15 in a logistic regression model comprising these variables significantly increased the area under the curve (AUC 0.738 without and 0.750 with GDF-15 included) and the net reclassification ability to predict AKI. Comparably, in receiver operating characteristic analysis the predictive capacity of the CC-ARF score (AUC 0.628) was improved by adding GDF-15 (AUC 0.684) but this score also had lower predictability than the logistic regression model. In random forest analyses the predictive capacity of GDF-15 was especially pronounced in patients with normal plasma creatinine. CONCLUSION: This suggests that preoperative plasma GDF-15 independently predicts postoperative AKI in patients undergoing elective cardiac surgery and is particularly helpful for risk stratification in patients with normal creatinine. TRIAL REGISTRATION: NCT01166360 on July 20, 2010.

Postoperative intubation time is associated with acute kidney injury in cardiac surgical patients.

INTRODUCTION: Acute kidney injury (AKI) is a frequent complication after cardiac surgery and is associated with a poor prognosis. Mechanical ventilation is an important risk factor for developing AKI in critically ill patients. Ventilation with high tidal volumes has been associated with postoperative organ dysfunction in cardiac surgical patients. No data are available about the effects of the duration of postoperative respiratory support in the immediate postoperative period on the incidence of AKI in patients after cardiac surgery. METHOD: We performed a secondary analysis of 584 elective cardiac surgical patients enrolled in an observational trial on the association between preoperative cerebral oxygen saturation and postoperative organ dysfunction and analyzed the incidence of AKI in patients with different times to extubation. The latter variable was graded in 4 h intervals (if below 16 h) or equal to or greater than 16 h. AKI was staged according to the AKI Network criteria. RESULTS: Overall, 165 (28.3%) patients developed AKI (any stage), 43 (7.4%) patients needed renal replacement therapy. Patients developing AKI had a significantly (P <0.001) lower renal perfusion pressure (RPP) in the first 8 hours after surgery (57.4 mmHg (95% CI: 56.0 to 59.0 mmHg)) than patients with a postoperatively preserved renal function (60.5 mmHg ((95% CI: 59.9 to 61.4 mmHg). The rate of AKI increased from 17.0% in patients extubated within 4 h postoperatively to 62.3% in patients ventilated for more than 16 h (P <0.001). Multivariate logistic regression analysis of variables significantly associated with AKI in the univariate analysis revealed that the time to the first extubation (OR: 1.024/hour, 95% CI: 1.011 to 1.044/hour; P <0.001) and RPP (OR: 0.963/mmHg; 95% CI: 0.934 to 0.992; P <0.001) were independently associated with AKI. CONCLUSION: Without taking into account potentially unmeasured confounders, these findings are suggestive that the duration of postoperative positive pressure ventilation is an important and previously unrecognized risk factor for AKI in cardiac surgical patients, independent from low RPP as an established AKI trigger, and that even a moderate delay of extubation increases AKI risk. If replicated independently, these findings may have relevant implications for clinical care and for further studies aiming at the prevention of cardiac surgery associated AKI.

Perioperative hemodynamic monitoring: Still a place for cardiac filling pressures?

The clinical usefulness of the so-called "static" cardiac filling pressures - central (CVP) and pulmonary-artery-occlusion-pressure (PAOP) - has come into question for guiding hemodynamic therapy due to their poor ability to predict fluid responsiveness in comparison with other monitoring modalities such as transpulmonary thermodilution-derived volumetric measurements, dynamic variables for assessing fluid responsiveness, and the potential risks associated with pulmonary artery catheterization. This contrasts with observations in multiple patient populations showing a clear association between increased CVP and PAOP levels and poor outcomes, probably due to a reduction in effective perfusion pressure (mean arterial pressure minus CVP) and their role as effectiveness parameters of the cardiovascular system. Furthermore, clinical studies have revealed beneficial effects when interpreting CVP and PAOP dynamically and combining them with flow-related hemodynamic variables. Taking into account the additional information derived from bedside CVP and PAOP pulse curve interpretation, cardiac filling pressures remain an important hemodynamic monitoring tool.