The results of this cross-sectional study reflect how hemodynamic monitoring is performed in reality in ICUs in the three European countries Germany, Austria, and Switzerland. In fact, all patients were monitored with basic hemodynamic monitoring consisting of ECG, blood pressure measurements, and pulse oximetry. Also the majority of patients received invasive arterial and central venous catheterization. Extended hemodynamic monitoring, and in particular monitoring of cardiac output, although widely available, was performed all over in less than 15 %. Mechanical ventilation, treatment backed by protocols, and the need for catecholamine therapy were the factors independently associated with the use of advanced hemodynamic monitoring. This was also validated in subgroup analyses of patients treated by mechanical ventilation or vasoactive agents. The most frequently used method for preload monitoring was the assessment of filling pressures. The use of volumetric or dynamic parameters of preload was rare. In 71.6 % of patients, in whom extended hemodynamic monitoring was added during the study period, this addition of monitoring led to direct changes in treatment. The vast majority of ICUs reported that protocols for hemodynamic treatment were available, and in nearly 60 % of patients, hemodynamic management was reported to be performed according to an implemented treatment protocol. In particular, treatment protocols for patients with sepsis were established. Whether quality of cardiovascular treatment was influenced by the use of specific treatment protocols cannot be assessed on the basis of the present data.
The acknowledgement that hemodynamic instability influences morbidity and mortality of critically ill patients has led to the development of various techniques of advanced hemodynamic monitoring and cardiovascular imaging. Further, many technical approaches have been taken to measure even complex physiological signals with low or even no invasiveness in order to reduce the monitoring-associated risks [11]. Finally, guidelines, treatment protocols, and consensus-based recommendations for several major diagnoses relevant for intensive care treatment have been developed in order to secure the transfer of best practice of hemodynamic management based on pathophysiological rationale and scientific evidence. But how this has influenced practice of hemodynamic monitoring and management in reality has only scarcely been investigated. Data regarding availability of monitoring equipment based on smaller surveys were published earlier from Switzerland including 55 medical and surgical ICUs, from Germany in 55 cardiac surgery ICUs, as well as from Italy again in 71 cardiac surgery centers [12–14]. Strength of our data set is that it represents data from a broad spectrum of ICUs of different sizes and a balanced proportion of ICUs at both university hospitals and non-university hospitals. This allows a comparison between different disciplines and institutions. Furthermore, we collected not only data on general availability of monitoring equipment but also real patient data, showing which monitoring was actually used. This, in combination with a high number of patients included, allowed further identification of factors that independently triggered the use of extended hemodynamic monitoring.
Our data show that technical requirements for basic hemodynamic monitoring, i.e., ECG, noninvasive blood pressure monitoring, and pulse oximetry, were given on all units. Noninvasive, extended hemodynamic monitoring (finger plethysmography waveform analysis, continuous blood pressure monitoring by volume clamp methods, or esophageal Doppler) was only available in very few of the studied ICUs, which is in line with earlier data from Switzerland [12]. Of note, there was obviously no relevant difference between the unit-leading disciplines regarding availability of these noninvasive technologies. Whether this low availability was caused by missing confidence in monitoring accuracy or by other reasons (for example economic) was beyond the scope of the present study.
In contrast, availability of echocardiography was much higher. Transthoracic echocardiography was available in more than 90 % of all units, with no major differences between different sizes of hospitals, between university hospitals and non-university hospitals, or between the different unit-leading disciplines. Obviously, today also transesophageal echocardiography is widely available (i.e., in more than 80 % of the units). This underlines the high acceptance and appreciation of this technology in intensive care medicine also outside cardiac surgery [13, 14]. But this high availability and the strong recommendations for its use [4, 15] are in contrast to the very low number of patients (34 out of 1790 patients, i.e., 1.9 %) that were actually reported to be investigated by echocardiography during the 24-h study period. Interestingly, Boulain et al. demonstrated comparable numbers specifically regarding the use of echocardiography for hemodynamic management of shock [16]. Further, echocardiography is only scarcely used in practice in Europe for guiding fluid therapy as Cecconi et al. recently showed [17].
We defined semi-invasive extended hemodynamic monitoring as monitoring modalities which use either peripheral arterial or central venous vascular access for further analyses besides pressure monitoring (i.e., autocalibrated arterial pulse contour analysis) or continuous central venous oximetry. It is of interest that, although nearly all of the investigated patients had arterial and central venous catheters in place, these monitoring modalities were only available in the minority of units.
Invasive extended hemodynamic monitoring based on thermodilution was widely available. Besides in cardiac surgery, which seems to remain a leading domain of the pulmonary artery catheter, the most frequent technology was transpulmonary thermodilution. However, the actual all-over use of both monitoring modalities is comparably low, as reflected in table a1 (Additional file 1: Table a1). This low use is supported also by the recent data from French ICUs, which points out the divergence between subjective perception of higher use reflected in the results of surveys among ICU physicians and the objective assessment based on patient data [12–14, 16].
Adequate monitoring and management of cardiac preload, and in particular the inaccuracy of the cardiac filling pressures CVP and PAOP as the rationale for guiding fluid therapy, have recently led many scientific discussions. Although filling pressures can offer additional and relevant physiological information, current consensus statements based on recently published data recommend not to manage fluid therapy primarily by filling pressures [1, 18]. From that perspective, it is interesting that still filling pressures were the main tool for the assessment of preload, whereas volumetric or functional parameters of preload played only a minimal role. This is again in line with the French findings of Boulaint et al. in patients with septic shock [16] and also with a recently published French study by Preau et al. investigating the use of static and dynamic hemodynamic parameters for predicting fluid responsiveness prior to volume expansion [19]. One explanation may be the frequently stressed limitations for the use of automated functional parameters of preload, i.e., the necessity of controlled mechanical ventilation and the absence of significant arrhythmias. This can be partly substantiated by our data. Although more than 80 % of all patients presented with a cardiac rhythm that allowed interpretation of those parameters (sinus rhythm, pacer rhythms), only 22.9 % of patients were on fully controlled mechanical ventilation. In contrast, in the group of hemodynamic unstable patients that received vasoactive agents, though the rate of arrhythmias was comparable, a higher ratio of 30.9 % fulfilled criteria for the assessment of functional preload parameters due to more frequent controlled mechanical ventilation. But even in this group, only about every second of these patients that fulfilled the criteria was monitored by dynamic preload parameters. Furthermore, thinking of the other two-thirds not fulfilling the criteria, it stresses the need for further development of functional parameters of preload that operate independently from the presence of ventilation mode. This is important as one can argue that those patients reflected presumably the group of patients with the highest need for differentiated cardiovascular management, because of the severity of their disease.
In particular, it is remarkable that the over-all fraction of patients monitored with cardiac output monitoring was as low as reported in 2003, i.e., more than 10 years ago, by Oldner et al. from 114 patients on Scandinavian ICUs [20]. Although in cardiac surgery patients and in patients receiving vasoactive agents, serving as a sign of hemodynamic instability, the proportion of patients in which cardiac output was monitored was now with 24 % slightly higher, the availability of novel and less invasive modalities for cardiac output monitoring has not extensively increased the use of this parameter so far. It is further remarkable that also the affiliation to a university hospital compared with a non-university hospital was no independent predictor for the use of extended hemodynamic monitoring.
The present study has limitations given by the fact that it was a point prevalence study, and should therefore be primarily understood as an initial assessment of status quo of hemodynamic monitoring and management. Further, inter- and intrapersonal reliability of the online CRF was not tested. Also the absence of more detailed background information on the specific hemodynamic protocols used in each individual institution, and the lacking information of clinical outcome limits further conclusions. Furthermore, the non-implementation of a standardized protocol cannot be automatically equated with the absence of knowledge on current guidelines or lower quality of patient care. However, treatment protocols were identified as one of the independent factors triggering the use of extended hemodynamic monitoring. Thus, they might moreover serve as an additional trigger for a closer hemodynamic evaluation in particular groups of patients. Here, further studies are desirable.
