key: cord-0873122-j3gm9vpz
authors: Michard, Frédéric; Malbrain, Manu LNG; Martin, Greg S; Fumeaux, Thierry; Lobo, Suzana; Gonzalez, Filipe; Pinho-Oliveira, Vitor; Constantin, Jean-Michel
title: Haemodynamic Monitoring and Management in COVID-19 Intensive Care Patients: An International Survey
date: 2020-08-09
journal: Anaesth Crit Care Pain Med
DOI: 10.1016/j.accpm.2020.08.001
sha: a5d5d1084770048de4becc974ee6bf8408e8c9a6
doc_id: 873122
cord_uid: j3gm9vpz

PURPOSE: To survey haemodynamic monitoring and management practices in ICU patients with the coronavirus disease 2019 (COVID-19). METHODS: A questionnaire was shared on social networks or via email by the authors and by Anaesthesia and/or Critical Care societies from France, Switzerland, Belgium, Brazil, and Portugal. Intensivists and anaesthetists involved in COVID-19 ICU care were invited to answer 14 questions about haemodynamic monitoring and management. RESULTS: Globally, 1000 questionnaires were available for analysis. Responses came mainly from Europe (n = 460) and America (n = 434). According to respondents, a majority of COVID-19 ICU patients frequently or very frequently received continuous vasopressor support (56%) and had an echocardiography performed (54%). Echocardiography revealed a normal cardiac function, a hyperdynamic state (43%), hypovolaemia (22%), a left ventricular dysfunction (21%) and a right ventricular dilation (20%). Fluid responsiveness was frequently assessed (84%), mainly using echo (62%), and cardiac output was measured in 69%, mostly with echo as well (53%). Venous oxygen saturation was frequently measured (79%), mostly from a CVC blood sample (94%). Tissue perfusion was assessed biologically (93%) and clinically (63%). Pulmonary oedema was detected and quantified mainly using echo (67%) and chest X-ray (61%). CONCLUSION: Our survey confirms that vasopressor support is not uncommon in COVID-19 ICU patients and suggests that different cardiac function phenotypes may be observed. Ultrasounds were used by many respondents, to assess cardiac function but also to predict fluid responsiveness and quantify pulmonary oedema. Although we observed regional differences, current international guidelines were apparently followed by most respondents.

Little is known about the haemodynamic consequences of the coronavirus disease 2019 and the haemodynamic management of patients requiring intensive care unit (ICU) admission. These patients have several reasons to become haemodynamically unstable. First, they may be hypovolaemic because of fever and fluid restriction, which has been recommended from hospital admission to limit the development of pulmonary oedema [1, 2] . Like any patients with systemic inflammation, they may also have some degree of vasodilation, which may be amplified by sedative drugs during mechanical ventilation. Circulating cytokines may induce ventricular dysfunction [3] , and, although postmortem studies suggest it is uncommon, coronavirus-induced myocarditis may be a cause as well of systolic and diastolic dysfunction [4] [5] [6] . Mechanical ventilation with positive endexpiratory pressure (PEEP) may impede right ventricular ejection and induce ventricular dilation, which may in turn decrease left ventricular filling (acute cor pulmonale) [7, 8] .

Finally, coagulation disorders are common in COVID-19 patients and pulmonary embolism seems to be more frequent than on the general ICU population [9, 10] .

Despite these pathophysiological considerations, large observational studies published so far focused on lung injury [11] , mentioned myocardial injury and arrhythmia as possible complications [12] , but did not report much information about the haemodynamic status and management of critically ill COVID-19 patients. According to a few studies, the proportion of ICU patients requiring vasopressor support may range between 35 and 95% [13] [14] [15] .

The WHO (https://www.who.int/publications-detail/clinical-management-of-severe-acuterespiratory-infection-when-novel-coronavirus-(ncov)-infection-is-suspected) and the NIH (https://covid19treatmentguidelines.nih.gov/critical-care/hemodynamics/) released recommendations for the haemodynamic management of COVID-19 patients. The Surviving J o u r n a l P r e -p r o o f Sepsis Campaign guidelines were quickly updated [1] . The Asian Critical Care Clinical Trials group also published guidelines based on their experience with the COVID-19 pandemic from the very beginning [2] . They all emphasised the importance of ultrasounds to assess cardiac function and the need to predict fluid responsiveness to rationalise fluid management.

An electronic survey was designed to investigate current haemodynamic monitoring and management practices in COVID-19 ICU patients, as well as alignment with recent guidelines. Questionnaires not filled by an intensivist or anaesthetist (certified or trainee), or that did not contain the geographical information, or with more than three unanswered questions were considered invalid. Responses were monitored on a daily basis and the database was J o u r n a l P r e -p r o o f locked for analysis after receiving 1000 valid questionnaires. Data are presented as numbers and percentages. Multiple answers were allowed for several questions (see Appendix A) so that cumulative percentages presented in the text or the figures may exceed 100%.

Comparisons between regions were done with a Chi-square test. A p value < 0.05 was considered statistically significant.

The survey database was closed on May 16 after receiving 1064 responses. Thirty-four questionnaires were filled by non-intensivists or non-anaesthetists, 28 questionnaires contained more than three unanswered questions and two questionnaires did not contain the geographical information. The remaining 1000 valid questionnaires were used for analysis. Responses came mainly from Europe (n = 460) and America (n = 434) (figure 1).

Most responders were intensivists (n = 649), 157 were intensivists and anaesthetists, 114 were anaesthetists, and 80 were trainees. Two hundred thirty-seven respondents had more than 10 years of experience working in the ICU. A comparison between the three main geographical areas (Europe, South America and North America) is presented in figure 5 . To monitor blood pressure, the first choice was the radial catheter in the three main regions. The femoral catheter was less often used in North America (8%) than in Europe (17%, p < 0.01) or in South America (21%, p < 0.01). To measure cardiac output, ultrasounds were the first choice in the three main regions. Transpulmonary thermodilution was less often used in North America (18%) than in Europe (51%, p < 0.01) or in South America (41%, p < 0.01). To predict fluid responsiveness, ultrasounds were also the first choice in the three main regions, followed by the pulse pressure variation (PPV) and the passive leg-raising (PLR) manoeuvre in comparable proportions. To assess pulmonary J o u r n a l P r e -p r o o f oedema, ultrasounds were the first choice in Europe and in South America, and the second choice after chest X-ray in North America. Extravascular lung water measurements were more often used in Europe (29%) and in South America (21%) than in North America (8%, p < 0.01).

Our survey confirms that haemodynamic instability is not uncommon in COVID-19 ICU patients and that different cardio-vascular profiles or phenotypes may be observed with echocardiography. From a monitoring standpoint, SvO2 was reported to be frequently measured from central venous catheters, and ultrasounds were reported to be widely used, not only to assess cardiac function but also to predict fluid responsiveness and to assess pulmonary oedema. Therefore, current guidelines regarding the use of echocardiography and the need to predict fluid responsiveness were apparently followed by most respondents.

Echocardiographic patterns reported by survey respondents were consistent with cardiovascular clusters recently described in septic shock [16] and underscore the value of ultrasound evaluations to identify the underlying mechanisms of shock and select the most appropriate therapy. Only a minority of echocardiographic evaluations were done using a transesophageal approach. Obesity (frequently reported in COVID-19 patients), mechanical ventilation and prone positioning may render the transthoracic approach challenging.

However, the proximity of airways, the risk of aerosol generation and contamination, uncertainties regarding the optimal modalities for probe cleaning, as well as time constraints may have restricted the use of transesophageal echocardiography (TEE). Our survey also J o u r n a l P r e -p r o o f suggests that hand-held or pocket echo devices were not widely adopted. This may be explained by the fact that these tools are relatively new and that many ICUs have high-end trolley ultrasound machines readily available (e.g. to guide CVC insertion).

One factor that may have influenced the importance of ultrasounds in the haemodynamic management of COVID-19 patients is the lack of availability of haemodynamic monitors.

Echo evaluations usually take less than 30 minutes so that, pending proper cleaning, the same device can be used for the haemodynamic assessment of several patients. In contrast, hemodynamic monitors are dedicated to the monitoring of a single patient and are often used several consecutive days. Therefore, the shortage of haemodynamic monitors may have magnified the role of ultrasound techniques in this pandemic context. Another contributing factor is the ability to gather a lot of information from a single echo evaluation.

Many respondents used echo not only to assess biventricular function but also to measure cardiac output, to predict fluid responsiveness and to detect lung B lines.

Cardiac output was frequently measured (69%). For many respondents (figure 4), and across the three main regions (figure 5), measurements were performed during echocardiographic evaluations. Otherwise, transpulmonary thermodilution was used by a significant number of respondents, with the exception of North America where uncalibrated pulse contour methods were used more often ( figure 5 ). This is somewhat surprising given the fact that uncalibrated pulse contour methods are known to have limited accuracy and precision to measure cardiac output in septic shock [17] , and their use is not recommended beyond the surgical population [18] . The Swan Ganz catheter was rarely used. Although pulmonary thermodilution remains a monitoring option in patients with septic shock [19, 20] , this finding is aligned with the global decline of this invasive tool [21] for which the new J o u r n a l P r e -p r o o f generation of intensivists did not receive much training. In addition, some clinicians may be reluctant to use a pulmonary artery catheter in the context of hypercoagulability and thromboembolic complications associated with COVID-19 [9, 10] .

The prediction of fluid responsiveness was adopted by a vast majority of respondents (84%).

This finding contrasts with the results of a worldwide observational study suggesting that the prediction of fluid responsiveness is not routinely done in ICUs [22] . However, this study done seven years ago may not reflect current practice anymore. The behaviour of our respondents is supported by recent studies showing outcome benefits when predicting fluid responsiveness in septic patients [23, 24] . Echo was ranked #1 for the prediction of fluid responsiveness, globally and in the three main regions. It was mainly performed with a transthoracic probe (TTE). The prediction of fluid responsiveness with TTE requires the evaluation of the inferior vena cava (IVC) respiratory variations [25] or of the velocity-time integral (VTI) respiratory variations recorded at the level of the left ventricular outflow tract [26] . It is worth noticing that the fully automatic calculation of these variables is not available and that they have a limited sensitivity in patients ventilated with a low tidal volume for protective mechanical ventilation. Indeed, in this context, large IVC or VTI respiratory variations are highly suggestive of fluid responsiveness, but small variations cannot exclude it (false negative). The same limitation applies to PPV and stroke volume variation (SVV) that were also popular methods among our respondents (figure 3) [27] . The passive leg-raising manoeuvre is an alternative to TTE-derived variables, PPV and SVV to predict fluid responsiveness during protective mechanical ventilation [28] . It was used by 378 of the 835 respondents (45%) who predicted fluid responsiveness. The use of the PLR manoeuvre requires the simultaneous use of a fast response cardiac output monitoring J o u r n a l P r e -p r o o f system (typically a pulse contour technique) in order to capture transient changes in stroke volume or cardiac output during the manoeuvre [29] .

Venous oxygen saturation was very frequently measured from a central venous catheter.

The three main determinants of venous oxygen saturation are haemoglobin, cardiac output and arterial oxygen saturation. Assuming haemoglobin stability, measuring venous oxygen saturation is a simple way to ensure that fluid restriction and positive end-expiratory pressure (PEEP) application do not decrease oxygen delivery. Both are used in an attempt to increase arterial oxygenation, but at the same time they are susceptible to decrease cardiac output. Therefore, at least from an oxygen delivery standpoint, the right volume status and the right PEEP level are those associated with the highest venous oxygen saturation [30] .

This might be the reason why venous oxygen saturation was so popular among our respondents, but this remains a hypothesis. Indeed, our survey was a snapshot of current behaviours and was not designed to explain these behaviours.

The assessment of tissue oxygenation was almost exclusively based on clinical (e.g. capillary refill time) and biological (e.g. kidney function, lactates) evaluations. New techniques such as NIRS and video-microscopy were rarely used. They are probably considered as research tools [31, 32] and one may imagine they were not available in many ICUs from many countries.

Our study has limitations. In addition to emails that are clearly targeted, we used social networks (LinkedIn, Twitter, WhatsApp) to invite clinicians answer the survey and share the link. Therefore, we were not able to control the number of clinicians who received the survey and hence to determine the percentage of respondents. Because the survey was built on a Google platform, it was not accessible from China and we were not able to include the J o u r n a l P r e -p r o o f feedback from Chinese doctors who have been involved in the pandemic from the very beginning. However, this is one of the largest surveys ever published in critical care [33] and we have been able to collect almost 900 responses from Europe and America, which are critical areas of the pandemic as well. Finally, this is a survey and not an audit nor an observational study. Therefore, the feedback gathered from clinicians reflects the perception they have of what is done or should be done in their unit, which may sometimes differ from reality [34] . In any case, our survey results remain of interest to understand where clinicians see value in haemodynamic monitoring tools and practice.

According to the 1000 intensivists and anaesthetists who sent back a valid questionnaire, vasopressor support was not uncommon in COVID-19 ICU patients. Several cardiac function phenotypes were reported, highlighting the importance of echocardiography. Ultrasounds were used by many respondents, not only to assess cardiac function but also to predict fluid responsiveness and quantify pulmonary oedema. Venous oxygen saturation measurements from a central venous catheter were also reported to be common practice. Although we observed regional differences, current international guidelines were apparently followed by most respondents.

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: 

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