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[...]radial arterial catheterization reports the same MAP as sensed in the aorta. [...]there is both arterial resistance in the small arteries that define a given arterial pressure-flow relation and a Pcc which defines the effective back pressure to that flow. [...]microcirculatory flow, as a direct measure of tissue blood flow, should vary independent of global changes in cardiac output and arterial pressure, as those changes are proportional changes in local metabolic demand [7].

BackgroundThe same principle behind pulse wave analysis can be applied on the pulmonary artery (PA) pressure waveform to estimate right ventricle stroke volume (RVSV). However, the PA pressure waveform might be influenced by the direct transmission of the intrathoracic pressure changes throughout the respiratory cycle caused by mechanical ventilation (MV), potentially impacting the reliability of PA pulse wave analysis (PAPWA). We assessed a new method that minimizes the direct effect of the MV on continuous PA pressure measurements and enhances the reliability of PAPWA in tracking beat-to-beat RVSV.MethodsContinuous PA pressure and flow were simultaneously measured for 2–3 min in 5 pigs using a high-fidelity micro-tip catheter and a transonic flow sensor around the PA trunk, both pre and post an experimental ARDS model. RVSV was estimated by PAPWA indexes such as pulse pressure (SVPP), systolic area (SVSystAUC) and standard deviation (SVSD) beat-to-beat from both corrected and non-corrected PA signals. The reference RVSV was derived from the PA flow signal (SVref).ResultsThe reliability of PAPWA in tracking RVSV on a beat-to-beat basis was enhanced after accounting for the direct impact of intrathoracic pressure changes induced by MV throughout the respiratory cycle. This was evidenced by an increase in the correlation between SVref and RVSV estimated by PAPWA under healthy conditions: rho between SVref and non-corrected SVSD – 0.111 (0.342), corrected SVSD 0.876 (0.130), non-corrected SVSystAUC 0.543 (0.141) and corrected SVSystAUC 0.923 (0.050). Following ARDS, correlations were SVref and non-corrected SVSD – 0.033 (0.262), corrected SVSD 0.839 (0.077), non-corrected SVSystAUC 0.483 (0.114) and corrected SVSystAUC 0.928 (0.026). Correction also led to reduced limits of agreement between SVref and SVSD and SVSystAUC in the two evaluated conditions.ConclusionsIn our experimental model, we confirmed that correcting for mechanical ventilation induced changes during the respiratory cycle improves the performance of PAPWA for beat-to-beat estimation of RVSV compared to uncorrected measurements. This was demonstrated by a better correlation and agreement between the actual SV and the obtained from PAPWA.

An international team of experts in the field of fluid resuscitation was invited by the ESICM to form a task force to systematically review the evidence concerning fluid administration using basic monitoring. The work included a particular emphasis on pre-ICU hospital settings and resource-limited settings. The work focused on four main questions: (1) What is the role of clinical assessment to guide fluid resuscitation in shock? (2) What basic monitoring is required to perform and interpret a fluid challenge? (3) What defines a fluid challenge in terms of fluid type, ranges of volume, and rate of administration? (4) What are the safety endpoints during a fluid challenge? The expert panel found insufficient evidence to provide recommendations according to the GRADE system, and was only able to make recommendations for basic interventions, based on the available evidence and expert opinion. The panel identified significant gaps in the scientific evidence on fluid administration outside the ICU (excluding the operating theater). Globally, scientific communities and health care systems should address these critical gaps in evidence through research on how basic fluid administration in resource-rich and resource-limited settings can be improved for the benefit of patients and societies worldwide.

Phenylephrine is an α1-adrenergic receptor agonist widely used to treat perioperative hypotension. Its other hemodynamic effects, in particular on preload and contractility, remain controversial. We, therefore, investigated the effect of continuously applied phenylephrine on central hemodynamics in eight mechanically ventilated domestic pigs. Mean arterial pressure (MAP) was increased in steps by 50%, and 100% using phenylephrine. Besides stroke volume (SV), cardiac output (CO), and MAP, mean systemic vascular resistance (SVR) and dynamic arterial elastance (Eadyn) were assessed for characterization of afterload. Changes in preload were assessed by central venous pressure (CVP), global end-diastolic volume (GEDV), mean systemic filling pressure analog (Pmsfa), pulse pressure variation (PPV), and stroke volume variation (SVV). Further, cardiac function index (CFI), global ejection fraction and dPmax were measured as markers of preload dependent contractility. MAP, SV, and CO significantly increased following both interventions, as did SVR. In contrast, Eadyn did not show significant changes. Although the volumetric preload variable GEDV increased after the first step of phenylephrine, this was not reflected by significant changes in CVP or Pmsfa. CFI and dPmax significantly increased after both steps. Phenylephrine does not only affect cardiac afterload, but also increases effective preload. In contrast to CVP and Pmsfa, this effect can be monitored by GEDV. Further, phenylephrine affects contractility.

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Purpose A number of studies performed in the operating room evaluated the hemodynamic effects of the fluid challenge (FC), solely considering the effect before and after the infusion. Few studies have investigated the pharmacodynamic effect of the FC on hemodynamic flow and pressure variables. We designed this trial aiming at describing the pharmacodynamic profile of two different FC infusion times, of a fixed dose of 4 ml kg −1 . Methods Forty-nine elective neurosurgical patients received two consecutive FCs of 4 ml kg −1 of crystalloids in 10 (FC 10 ) or 20 (FC 20 ) minutes, in a random order. Fluid responsiveness was defined as stroke volume index increase ≥ 10%. We assessed the net area under the curve (AUC), the maximal percentage difference from baseline (d max ), time when the d max was observed (t max ), change from baseline at 1-min (d 1 ) and 5-min (d 5 ) after FC end. Results After FC 10 and FC 20, 25 (51%) and 14 (29%) of 49 patients were classified as fluid responders (p = 0.001). With the exception of the AUCs of SAP and MAP, the AUCs of all the considered hemodynamic variables were comparable. The d max and the t max were overall comparable. In both groups, the hemodynamic effects on flow variables were dissipated within 5 min after FC end. Conclusions The infusion time of FC administration affects fluid responsiveness, being higher for FC 10 as compared to FC 20 . The effect on flow variables of either FCs fades 5 min after the end of infusion.

Despite the increasing evidence of the benefit of corticosteroids for the treatment of moderate-severe coronavirus disease 2019 (COVID-19) patients, no data are available about the potential role of high doses of steroids for these patients. We evaluated the mortality, the risk of need for mechanical ventilation (MV), or death and the risk of developing a severe acute respiratory distress syndrome (ARDS) between high (HD) and standard doses (SD) among patients with a severe COVID-19. All consecutive confirmed COVID-19 patients admitted to a single center were selected, including those treated with steroids and an ARDS. Patients were allocated to the HD (≥ 250 mg/day of methylprednisolone) of corticosteroids or the SD (≤ 1.5 mg/kg/day of methylprednisolone) at discretion of treating physician. Five hundred seventy-three patients were included: 428 (74.7%) men, with a median (IQR) age of 64 (54–73) years. In the HD group, a worse baseline respiratory situation was observed and male gender, older age, and comorbidities were significantly more common. After adjusting by baseline characteristics, HDs were associated with a higher mortality than SD (adjusted OR 2.46, 95% CI 1.59–3.81, p < 0.001) and with an increased risk of needing MV or death (adjusted OR 2.35, p = 0.001). Conversely, the risk of developing a severe ARDS was similar between groups. Interaction analysis showed that HD increased mortality exclusively in elderly patients. Our real-world experience advises against exceeding 1–1.5 mg/kg/day of corticosteroids for severe COVID-19 with an ARDS, especially in older subjects. This reinforces the rationale of modulating rather than suppressing immune responses in these patients.