Elevated central venous pressure is associated with impairment of microcirculatory blood flow in sepsis: a hypothesis generating post hoc analysis

Nitroglycerin challenge identifies microcirculatory target for improved resuscitation in patients with circulatory shock

BACKGROUND

Circulatory shock and multi-organ failure remain major contributors to morbidity and mortality in critically ill patients and are associated with insufficient oxygen availability in the tissue. Intrinsic mechanisms to improve tissue perfusion, such as up-regulation of functional capillary density (FCD) and red blood cell velocity (RBCv), have been identified as maneuvers to improve oxygen extraction by the tissues; however, their role in circulatory shock and potential use as resuscitation targets remains unknown. To fill this gap, we examined the baseline and maximum recruitable FCD and RBCv in response to a topical nitroglycerin stimulus (FCDNG, RBCvNG) in patients with and without circulatory shock to test whether this may be a method to identify the presence and magnitude of a microcirculatory reserve capacity important for identifying a resuscitation target.

METHODS

Sublingual handheld vital microscopy was performed after initial resuscitation in mechanically ventilated patients consecutively admitted to a tertiary medical ICU. FCD and RBCv were quantified using an automated computer vision algorithm (MicroTools). Patients with circulatory shock were retrospectively identified via standardized hemodynamic and clinical criteria and compared to patients without circulatory shock.

RESULTS

54 patients (57 ± 14y, BMI 26.3 ± 4.9 kg/m2, SAPS 56 ± 19, 65% male) were included, 13 of whom presented with circulatory shock. Both groups had similar cardiac index, mean arterial pressure, RBCv, and RBCvNG. Heart rate (p < 0.001), central venous pressure (p = 0.02), lactate (p < 0.001), capillary refill time (p < 0.01), and Mottling score (p < 0.001) were higher in circulatory shock after initial resuscitation, while FCD and FCDNG were 10% lower (16.9 ± 4.2 and 18.9 ± 3.2, p < 0.01; 19.3 ± 3.1 and 21.3 ± 2.9, p = 0.03). Nitroglycerin response was similar in both groups, and circulatory shock patients reached FCDNG similar to baseline FCD found in patients without shock.

CONCLUSION

Critically ill patients suffering from circulatory shock were found to present with a lower sublingual FCD. The preserved nitroglycerin response suggests a dysfunction of intrinsic regulation mechanisms to increase the microcirculatory oxygen extraction capacity associated with circulatory shock and identifies a potential resuscitation target. These differences in microcirculatory hemodynamic function between patients with and without circulatory shock were not reflected in blood pressure or cardiac index.

Association between early central venous pressure measurement and all-cause mortality in critically ill patients with heart failure: A cohort of 11,241 patients

Background

The timing of central venous pressure (CVP) measurement may play a crucial role in heart failure management, yet no studies have explored this aspect.

Methods

Clinical information pertaining to patients in critical condition with a diagnosis of heart failure was retrieved from the MIMIC-IV database. The association between initial measurements of central venous pressure (CVP) and the incidence of mortality from all causes was analyzed using the Cox proportional hazards approach. Subgroup analysis and propensity score matching were conducted for sensitivity analyses.

Results

This study included 11,241 participants (median age, 75 years; 44.70 % female). Utilizing restricted cubic spline and Kaplan-Meier survival analyses, it was determined that prognostic outcomes were better when CVP was measured within the initial 5-h window. Multivariate-adjusted 1-year (HR: 0.69; 95 % CI: 0.61-0.77), 90-day (HR: 0.70; 95 % CI: 0.62-0.80), and 30-day (HR: 0.67; 95 % CI: 0.57-0.78) all-cause mortalities were significantly lower in patients with early CVP measurement, which was proved robustly in subgroup analysis. Subsequent to the application of propensity score matching, a cohort of 1536 matched pairs was established, with the observed mortality rates continuing to be significantly lower among participants who underwent early CVP assessment.

Conclusions

Early CVP measurement (within 5 h) demonstrated an independent correlation with a decrease in both immediate and extended all-cause mortality rates among patients in critical condition suffering from heart failure.

Association Of Estimated Plasma Volume with New Onset Acute Kidney Injury in Hospitalized COVID-19 Patients

PURPOSE

To explore the association of estimated plasma volume (ePV) and plasma volume status (PVS) as surrogates of volume status with new-onset AKI and in-hospital mortality among hospitalized COVID-19 patients.

MATERIALS AND METHODS

We performed a retrospective multi-center study on COVID-19-related ARDS patients who were admitted to the Mayo Clinic Enterprise health system. Plasma volume was calculated using the formulae for ePV and PVS, and longitudinal analysis was performed to find the association of ePV and PVS with new-onset AKI during hospitalization as the primary outcome and in-hospital mortality as a secondary outcome.

RESULTS

Our analysis included 7616 COVID-19 patients with new-onset AKI occurring in 1365 (17.9%) and a mortality rate of 25.96% among them. A longitudinal multilevel multivariate analysis showed both ePV (OR 1.162; 95% CI 1.048-1.288, p=0.004) and PVS (OR 1.032; 95% CI 1.012-1.050, p=0.001) were independent predictors of new onset AKI. Higher PVS was independently associated with increased in-hospital mortality (OR 1.038, 95% CI 1.007-1.070, p=0.017), but not ePV (OR 0.868, 95% CI 0.740-1.018, p=0.082).

CONCLUSION

A higher PVS correlated with a higher incidence of new-onset AKI and worse outcomes in our cohort of hospitalized COVID-19 patients. Further large-scale and prospective studies are needed to understand its utility.

Exploring the optimal range of central venous pressure in sepsis and septic shock patients: A retrospective study in 208 hospitals

BACKGROUND

The aim of this study was to investigate the optimal CVP range in sepsis and septic shock patients admitted to intensive care unit.

METHODS

We performed a retrospective study with adult sepsis patients with CVP records based on the eICU Collaborative Research Database. Multivariable logistic regression was performed to explore the associations between CVP level and hospital mortality. Non-linear correlations and optimal CVP range were explored using restricted cubic splines (RCS).

RESULTS

A total of 5302 sepsis patients were included in this study. Patients in 4-8 mmHg group owned the lowest odds ratio for raw hospital mortality (19.7%). The logistic regression analyses revealed that hospital death risk increased significantly when mean CVP level exceeds 12 mmHg compared to 4-8 mmHg level. U-shaped association of CVP with hospital mortality was revealed by RCS model in septic shock patients and the optimal range was 5.6-12 mmHg. While, there was a J-shaped trend for non-septic shock patients. For non-septic shock patients, patients had an increased risk of hospital death only if CVP exceeded 11 mmHg.

CONCLUSIONS

We observed U-shaped association between mean CVP level and hospital mortality in septic shock patients and J-shaped association in non-septic shock patients. This may imply that patients with different severity of sepsis have different CVP requirements. We need to monitor and manage CVP according to the circulatory status of the sepsis patient.

What every intensivist should know about the IVC

Assessment of the IVC by point-of-care ultrasound in the context of resuscitation has been a controversial topic in the last decades. Most of the focus had been on its use as a surrogate marker for fluid responsiveness, with results being equivocal. We review its important anatomical aspects as well as the physiological rationale behind ultrasound assessment and propose a new way to do so, as well as explain its central role in the concept of fluid tolerance.

Non-invasive assessment of sublingual microcirculation using flow derived from green light PPG: evaluation and reference values

Significance

The study of sublingual microcirculation offers valuable insights into vascular changes and overcomes some limitations of peripheral microcirculation assessment. Videomicroscopy and pulse oximetry have been used to assess microcirculation, providing insights into organ perfusion beyond macrohemodynamics parameters. However, both techniques have important limitations that preclude their use in clinical practice.

Aim

To address this, we propose a non-invasive approach using photoplethysmography (PPG) to assess microcirculation.

Approach

Two experiments were performed on different samples of 31 subjects. First, multi-wavelength, finger PPG signals were compared before and while applying pressure on the sensor to determine if PPG signals could detect changes in peripheral microcirculation. For the second experiment, PPG signals were acquired from the ventral region of the tongue, aiming to assess the microcirculation through features calculated from the PPG signal and its first derivative.

Results

In experiment 1, 13 out of 15 features extracted from green PPG signals showed significant differences (p < 0.05 ) before and while pressure was applied to the sensor, suggesting that green light could detect flow distortion in superficial capillaries. In experiment 2, 15 features showed potential application of PPG signal for sublingual microcirculation assessment.

Conclusions

The PPG signal and its first derivative have the potential to effectively assess microcirculation when measured from the fingertip and the tongue. The assessment of sublingual microcirculation was done through the extraction of 15 features from the green PPG signal and its first derivative. Future studies are needed to standardize and gain a deeper understanding of the evaluated features.

Transfusion increased skin blood flow when initially low in volume-resuscitated patients without acute bleeding

Background

Alterations in skin blood flow is a marker of inadequate tissue perfusion in critically ill patients after initial resuscitation. The effects of red blood cell transfusions (RBCT) on skin perfusion are not described in this setting. We evaluated the effects of red blood cell transfusions on skin tissue perfusion in critically ill patients without acute bleeding after initial resuscitation.

Methods

A prospective observational study included 175 non-bleeding adult patients after fluid resuscitation requiring red blood cell transfusions. Using laser Doppler, we measured finger skin blood flow (SBF) at skin basal temperature (SBFBT), together with mean arterial pressure (MAP), heart rate (HR), hemoglobin (Hb), central venous pressure (CVP), lactate, and central or mixed venous oxygen saturation before and 1 h after RBCT. SBF responders were those with a 20% increase in SBFBT after RBCT.

Results

Overall, SBFBT did not significantly change after RBCT [from 79.8 (4.3-479.4) to 83.4 (4.9-561.6); p = 0.67]. A relative increase equal to or more than 20% in SBFBT after RBCT (SBF responders) was observed in 77/175 of RBCT (44%). SBF responders had significantly lower SBFBT [41.3 (4.3-279.3) vs. 136.3 (6.5-479.4) perfusion units; p < 0.01], mixed or central venous oxygen saturation (62.5 ± 9.2 vs. 67.3% ± 12.0%; p < 0.01) and CVP (8.3 ± 5.1 vs. 10.3 ± 5.6 mmHg; p = 0.03) at baseline than non-responders. SBFBT increased in responders [from 41.3 (4.3-279.3) to 93.1 (9.8-561.6) perfusion units; p < 0.01], and decreased in the non-responders [from 136.3 (6.5-479.4) to 80.0 (4.9-540.8) perfusion units; p < 0.01] after RBCT. Pre-transfusion SBFBT was independently associated with a 20% increase in SBFBT after RBCT. Baseline SBFBT had an area under receiver operator characteristic of 0.73 (95% CI, 0.68-0.83) to predict SBFBT increase; A SBFBT of 73.0 perfusion units (PU) had a sensitivity of 71.4% and a specificity of 70.4% to predict SBFBT increase after RBCT. No significant differences in SBFBT were observed after RBCT in different subgroup analyses.

Conclusion

The skin blood flow is globally unaltered by red blood cell transfusions in non-bleeding critically ill patients after initial resuscitation. However, a lower SBFBT at baseline was associated with a relative increase in skin tissue perfusion after RBCT.

Effect of norepinephrine on the vascular waterfall and tissue perfusion in vasoplegic hypotensive patients: a prospective, observational, applied physiology study in cardiac surgery

BACKGROUND

Norepinephrine is a commonly used drug for treating vasoplegic acute circulatory failure in ICU. The prediction of norepinephrine macro- and micro-circulatory response is complicated by its uneven receptors' distribution between the arterial and the venous structures, and by the presence of a physiological vascular waterfall (VW) that disconnects the arterial and the venous circulation in two pressure systems. The objectives of this study were to describe the VW in patients with arterial hypotension due to vasodilatory circulatory shock, and its behavior according to its response to norepinephrine infusion.

METHODS

A prospective, observational, bi-centric study has included adult patients, for whom the physician decided to initiate norepinephrine during the six first hours following admission to the ICU after cardiac surgery, and unresponsive to a fluid challenge. The mean systemic pressure (MSP) and the critical closing pressure (CCP) were measured at inclusion and after norepinephrine infusion.

RESULTS

Thirty patients were included. Norepinephrine increased arterial pressure and total peripheral resistances in all cohort. The cohort was dichotomized as VW responders (patients with a change of VW over the least significant change (≥ 93% increase in VW)), and as VW non-responders. In 19 (63%) of the 30 patients, VW increased from 3.47 [- 14.43;7.71] mmHg to 43.6 [25.8;48.1] mmHg, p < 0.001) with norepinephrine infusion, being classified as VW responders. The VW responders improved cardiac index (from 1.8 (0.6) L min-1 m-2 to 2.2 (0.5) L min-1 m-2, p = 0.002), capillary refill time (from to 4.2 (1.1) s to 3.1 (1) s, p = 0.006), and pCO2 gap (from 9 [7;10] mmHg to 6 [4;8] mmHg, p = 0.04). No baseline parameters were able to predict the VW response to norepinephrine. In comparison, VW non-responders did not significantly change the VW (from 5 [-5;16] mmHg to -2 [-12;15] mmHg, p = 0.17), cardiac index (from 1.6 (0.3) L min-1 m-2 to 1.8 (0.4) L min-1 m-2, p = 0.09) and capillary refill time (from 4.1 (1) s to 3.7 (1.4), p = 0.44).

CONCLUSIONS

In post-cardiac surgery patients with vasoplegic arterial hypotension, the vascular waterfall is low. Norepinephrine did not systematically restore the vascular waterfall. Increase of the vascular waterfall was associated with an improvement of laboratory and clinical parameters of tissue perfusion.

The Eight Unanswered and Answered Questions about the Use of Vasopressors in Septic Shock

Septic shock is mainly characterized-in addition to hypovolemia-by vasoplegia as a consequence of a release of inflammatory mediators. Systemic vasodilatation due to depressed vascular tone results in arterial hypotension, which induces or worsens organ hypoperfusion. Accordingly, vasopressor therapy is mandatory to correct hypotension and to reverse organ perfusion due to hypotension. Currently, two vasopressors are recommended to be used, norepinephrine and vasopressin. Norepinephrine, an α₁-agonist agent, is the first-line vasopressor. Vasopressin is suggested to be added to norepinephrine in cases of inadequate mean arterial pressure instead of escalating the doses of norepinephrine. However, some questions about the bedside use of these vasopressors remain. Some of these questions have been well answered, some of them not clearly addressed, and some others not yet answered. Regarding norepinephrine, we firstly reviewed the arguments in favor of the choice of norepinephrine as a first-line vasopressor. Secondly, we detailed the arguments found in the recent literature in favor of an early introduction of norepinephrine. Thirdly, we reviewed the literature referring to the issue of titrating the doses of norepinephrine using an individualized resuscitation target, and finally, we addressed the issue of escalation of doses in case of refractory shock, a remaining unanswered question. For vasopressin, we reviewed the rationale for adding vasopressin to norepinephrine. Then, we discussed the optimal time for vasopressin administration. Subsequently, we addressed the issue of the optimal vasopressin dose, and finally we discussed the best strategy to wean these two vasopressors when combined.

Prevalence of systemic venous congestion assessed by Venous Excess Ultrasound Grading System (VExUS) and association with acute kidney injury in a general ICU cohort: a prospective multicentric study

BACKGROUND

The importance of assessing venous congestion in ICU patients is widely acknowledged, but its study is hampered by the lack of a practical evaluation tool. The Venous Excess Ultrasound Grading System (VExUS), based on a semi-quantitative combined ultrasound assessment, has been associated with acute kidney injury (AKI) in cardiac ICU patients. The objectives of this study were to assess the prevalence of congestion using VExUS in general ICU patients, and to evaluate the association between VExUS, AKI and death.

METHODS

This prospective, observational study included adult patients within 24 h of ICU admission. VExUS and hemodynamic parameters were measured four times during the ICU stay: within 24 h of ICU admission, after day 1 (between 24 and 48 h), after day 2 (between 48 and 72 h), and last day of ICU stay. The prevalence of AKI during the first week in ICU and 28-day mortality were assessed.

RESULTS

Among the 145 patients included, the percentage of patients with a VExUS score of 2 (moderate congestion) and 3 (severe congestion) was 16% and 6%, respectively. The prevalence did not change over the study period. There was no significant association between admission VExUS scores and AKI (p = 0.136) or 28-day mortality (p = 0.594). Admission VExUS ≥ 2 was not associated with AKI (OR 0.499, CI_95% 0.21-1.17, p = 0.109) nor 28-day mortality (OR 0.75, CI_95% 0.2-2.8, p = 0.669). The results were similar for VExUS scores measured at day 1 and day 2.

CONCLUSIONS

In general ICU cohort the prevalence of moderate to severe venous congestion was low. Early assessment of systemic venous congestion using VExUS scores was not associated with the development of AKI or with 28-day mortality.

Impact of central venous pressure during the first 24 h and its time-course on the lactate levels and clinical outcomes of patients who underwent coronary artery bypass grafting

Purpose

Previous studies have revealed that elevated mean central venous pressure (CVP) was associated with poor prognosis in specific patient groups. But no study explored the impact of mean CVP on prognosis of patients who underwent coronary artery bypass grafting surgery (CABG). The purpose of this study was to investigate the impacts of elevated CVP and its time-course on clinical outcomes of patients who underwent CABG and potential mechanisms.

Methods

A retrospective cohort study was performed based on the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. We first identified the CVP during specific period with the most predictive value. Patients were categorized into the low-CVP and high-CVP group on the basis of the cut-off value. A propensity score matching was used to adjust covariates. The primary outcome was a 28-day mortality. The secondary outcomes were 1-year mortality and in-hospital mortality, the length of intensive care unit (ICU) stay and hospitalization, acute kidney injury incidence, use of vasopressors, duration of ventilation and oxygen index, and lactate levels and clearance. Patients in the high-CVP group were categorized into the "second day CVP ≤ 13.46 mmHg" group and the "second day CVP > 13.46 mmHg" group, respectively, and the clinical outcomes were the same as before.

Results

A total of 6,255 patients who underwent CABG were picked from the MIMIC-IV database, of which 5,641 CABG patients were monitored by CVP measurement during the first 2 days after ICU admission and 206,016 CVP records were extracted from the database. The mean CVP during the first 24 h was the most correlative and statistically significant for the 28-day mortality. The risk of the 28-day mortality was increased in the high-CVP group [OR 3.45 (95% CI: 1.77-6.70; p < 0.001)]. Patients with elevated CVP levels had worse secondary outcomes. The maximum of lactate levels and lactate clearance were also poor in the high-CVP group. For patients in the high-CVP group during the first 24 h, whose mean CVP during the second day lowered to less than the cut-off value, had better clinical outcomes.

Conclusions

An elevated mean CVP during the first 24 h was correlated with poor outcomes in patients who underwent CABG. The potential mechanisms may be influencing the lactate levels and lactate clearance through the impact on afterload of tissue perfusion. Patients whose mean CVP during the second day dropped to less than the cut-off value had favorable prognosis.

Microcirculatory dysfunction in cardiogenic shock

Cardiogenic shock is usually defined as primary cardiac dysfunction with low cardiac output leading to critical organ hypoperfusion, and tissue hypoxia, resulting in high mortality rate between 40% and 50% despite recent advances. Many studies have now evidenced that cardiogenic shock not only involves systemic macrocirculation, such as blood pressure, left ventricular ejection fraction, or cardiac output, but also involves significant systemic microcirculatory abnormalities which seem strongly associated with the outcome. Although microcirculation has been widely studied in the context of septic shock showing heterogeneous alterations with clear evidence of macro and microcirculation uncoupling, there is now a growing body of literature focusing on cardiogenic shock states. Even if there is currently no consensus regarding the treatment of microcirculatory disturbances in cardiogenic shock, some treatments seem to show a benefit. Furthermore, a better understanding of the underlying pathophysiology may provide hypotheses for future studies aiming to improve cardiogenic shock prognosis.

Novelties in the evaluation of microcirculation in septic shock

Microvascular alterations were first described in critically ill patients about 20 years ago. These alterations are characterized by a decrease in vascular density and presence of non-perfused capillaries close to well-perfused vessels. In addition, heterogeneity in microvascular perfusion is a key finding in sepsis. In this narrative review, we report our actual understanding of microvascular alterations, their role in the development of organ dysfunction, and the implications for outcome. Herein, we discuss the state of the potential therapeutic interventions and the potential impact of novel therapies. We also discuss how recent technologic development may affect the evaluation of microvascular perfusion.

Diuretics depletion improves cardiac output and ventriculo-arterial coupling in congestive ICU patients during hemodynamic de-escalation

PURPOSE

Congestion was shown to hamper organ perfusion, but the exact timing of diuretic initiation during hemodynamic de-escalation in shock is unclear. The aim of this study was to describe the hemodynamic effects of diuretic initiation in the stabilized shock.

METHODS

We performed a monocentric, retrospective analysis, in a cardiovascular medico-surgical ICU. We included consecutive resuscitated adult patients, for whom the clinician decided to introduce loop diuretic treatment for clinical signs of fluid overload. The patients were hemodynamically evaluated at the moment of diuretic introduction and 24 h later.

RESULTS

Seventy ICU patients were included in this study, with a median duration of ICU stay before diuretic initiation of 2 [1-3] days. 51(73%) patients were classified as congestive (central venous pressure > 12 mmHg). After treatment, the cardiac index increased towards normal values in the congestive group (2.7 ± 0.8 L min^- 1 m^- 2 from 2.5 ± 0.8 L min^- 1 m^- 2, p = 0.042), but not in the non-congestive group (2.7 ± 0.7 L min^- 1 m^- 2 from baseline 2.7 ± 0.8 L min^- 1 m^- 2, p = 0.968). A decrease in arterial lactate concentrations was observed in the congestive group (2.1 ± 2 mmol L^- 1 vs. 1.3 ± 0.6 mmol L^- 1, p < 0.001). The diuretic therapy was associated with an improvement of ventriculo-arterial coupling comparing with baseline values in the congestive group (1.69 ± 1 vs. 1.92 ± 1.5, p = 0.03). The norepinephrine use decreased in congestive patients (p = 0.021), but not in the non-congestive group (p = 0.467).

CONCLUSION

The initiation of diuretics in ICU congestive patients with stabilized shock was associated with improvement of cardiac index, ventriculo-arterial coupling, and tissue perfusion parameter. These effects were not observed in non-congestive patients.

How I personalize fluid therapy in septic shock?

During septic shock, fluid therapy is aimed at increasing cardiac output and improving tissue oxygenation, but it poses two problems: it has inconsistent and transient efficacy, and it has many well-documented deleterious effects. We suggest that there is a place for its personalization according to the patient characteristics and the clinical situation, at all stages of circulatory failure. Regarding the choice of fluid for volume expansion, isotonic saline induces hyperchloremic acidosis, but only for very large volumes administered. We suggest that balanced solutions should be reserved for patients who have already received large volumes and in whom the chloremia is rising. The initial volume expansion, intended to compensate for the constant hypovolaemia in the initial phase of septic shock, cannot be adapted to the patient's weight only, as suggested by the Surviving Sepsis Campaign, but should also consider potential absolute hypovolemia induced by fluid losses. After the initial fluid infusion, preload responsiveness may rapidly disappear, and it should be assessed. The choice between tests used for this purpose depends on the presence or absence of mechanical ventilation, the monitoring in place and the risk of fluid accumulation. In non-intubated patients, the passive leg raising test and the mini-fluid challenge are suitable. In patients without cardiac output monitoring, tests like the tidal volume challenge, the passive leg raising test and the mini-fluid challenge can be used as they can be performed by measuring changes in pulse pressure variation, assessed through an arterial line. The mini-fluid challenge should not be repeated in patients who already received large volumes of fluids. The variables to assess fluid accumulation depend on the clinical condition. In acute respiratory distress syndrome, pulmonary arterial occlusion pressure, extravascular lung water and pulmonary vascular permeability index assess the risk of worsening alveolar oedema better than arterial oxygenation. In case of abdominal problems, the intra-abdominal pressure should be taken into account. Finally, fluid depletion in the de-escalation phase is considered in patients with significant fluid accumulation. Fluid removal can be guided by preload responsiveness testing, since haemodynamic deterioration is likely to occur in patients with a preload dependent state.

Fluid management in septic patients with pulmonary hypertension, review of the literature

The management of sepsis in patients with pulmonary hypertension (PH) is challenging due to significant conflicting goals of management and complex hemodynamics. As PH progresses, the ability of right heart to perfuse lungs at a normal central venous pressure (CVP) is impaired. Elevated pulmonary vascular pressure, due to pulmonary vasoconstriction and vascular remodeling, opposes blood flow through lungs thus limiting the ability of right ventricle (RV) to increase cardiac output (CO) and maintain adequate oxygen delivery to tissue. In sepsis without PH, avoidance of volume depletion with intravascular volume replacement, followed by vasopressor therapy if hypoperfusion persists, remains the cornerstone of therapy. Intravenous fluid (IVF) resuscitation based on individualized hemodynamic assessment can help improve the prognosis of critically ill patients. This is accomplished by optimizing CO by maintaining adequate preload, afterload and contractility. Particular challenges in patients with PH include RV failure as a result of pressure and volume overload, gas exchange abnormalities, and managing IVF and diuretic use. Suggested approaches to remedy these difficulties include early recognition of symptoms associated with pressure and volume overload, intravascular volume management strategies and serial lab monitoring to assess electrolytes and renal function.

Effects of Fluids on the Sublingual Microcirculation in Sepsis

Sepsis is one of the most common and deadly syndromes faced in Intensive Care settings globally. Recent advances in bedside imaging have defined the changes in the microcirculation in sepsis. One of the most advocated interventions for sepsis is fluid therapy. Whether or not fluid bolus affects the microcirculation in sepsis has not been fully addressed in the literature. This systematic review of the evidence aims to collate studies examining the microcirculatory outcomes after a fluid bolus in patients with sepsis. We will assimilate the evidence for using handheld intra vital microscopes to guide fluid resuscitation and the effect of fluid bolus on the sublingual microcirculation in patients with sepsis and septic shock. We conducted a systematic search of Embase, CENTRAL and Medline (PubMed) using combinations of the terms "microcirculation" AND "fluid" OR "fluid resuscitation" OR "fluid bolus" AND "sepsis" OR "septic shock". We found 3376 potentially relevant studies. Fifteen studies published between 2007 and 2021 fulfilled eligibility criteria to be included in analysis. The total number of participants was 813; we included six randomized controlled trials and nine non-randomized, prospective observational studies. Ninety percent used Sidestream Dark Field microscopy to examine the microcirculation and 50% used Hydroxyethyl Starch as their resuscitation fluid. There were no clear effects of fluid on the microcirculation parameters. There was too much heterogeneity between studies and methodology to perform meta-analysis. Studies identified heterogeneity of affect in the sepsis population, which could mean that current clinical classifications were not able to identify different microcirculation characteristics. Use of microcirculation as a clinical endpoint in sepsis could help to define sepsis phenotypes. More research into the effects of different resuscitation fluids on the microcirculation is needed.

Impact of central venous pressure on the mortality of patients with sepsis-related acute kidney injury: a propensity score-matched analysis based on the MIMIC IV database

Background

Sepsis has long been a life-threatening organ dysfunction. Sepsis associated acute kidney injury (SA-AKI) is an important complication of sepsis, as an important hemodynamic index, the impact of central venous pressure (CVP) on sepsis patients needs to be explored. Thus this study aimed to investigate the relationship between CVP and the mortality of SA-AKI.

Methods

Clinical data of adult patients with sepsis-related acute kidney injury, defined as met both the Sepsis 3.0 criteria and the Kidney Disease Improving Global Outcomes Clinical Practice Guideline (KDIGO) criteria, were obtained from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database. The included cohort was divided into a high CVP and a low CVP group were determined based on the cuf-off value from receiver operating characteristic curve, with propensity score-matched analysis of the 28-day mortality for both groups and sensitivity analysis using inverse the probability-weighting model, multifactorial regression, and doubly robust estimation, patients acquired chronic coronary syndrome (CCS) and diabetes were also taken into consideration.

Results

Of 1,377 patients with sepsis-related acute kidney injury, low CVP group (<13 mmHg) was 67.4% (n=928) and high CVP group (≥13 mmHg) was 32.6% (n=449). The two groups were matched 1:1 by propensity score to obtain a matched cohort (n=288). The mortality rates in the low versus high CVP group (19.4% vs. 34.7%) were statistically difference (odds ratio OR: 0.454; 95% confidence interval 0.263, 0.771). Moreover, the bistable analysis of logistic regression of the matched cohort (OR: 0.434; 95% CI: 0.244, 0.757), propensity score inverse probability weighting (IPW) (OR: 0.547; 95% CI: 0.454, 0.658), and multifactorial logistic regression (OR: 0.352; 95% CI: 0.127, 0.932) all yielded the same results.

Conclusions

In patients with sepsis-related acute kidney injury, a lower CVP level (<13 mmHg) is an independent variable associated with decreased mortality. The threshold of CVP needs to be controlled in clinical work to improve the prognosis of patients with SA-AKI.

[The role of the microcirculation in the pathogenesis of organ dysfunction]

The microcirculation includes all blood and lymph vessels with a diameter < 100 µm. Microcirculatory dysfunction is common in critically ill patients and is closely associated with both the severity of (multi-)organ dysfunction and mortality. The nature and extent of microcirculatory dysfunction differ depending on the underlying disease and are most pronounced in patients with systemic inflammation (e. g. sepsis), specific infections (e. g. malaria, dengue) or thrombocytopenia-associated multiple organ failure. This manuscript provides an overview of the pathophysiology, monitoring and therapy of microcirculatory dysfunction in the critically ill patient.

High Central Venous Pressure after Cardiac Surgery Might Depict Hemodynamic Deterioration Associated with Increased Morbidity and Mortality

Background: Cardiac surgery patients represent a high-risk cohort in intensive care units (ICUs). Central venous pressure (CVP) measurement seems to remain an integral part in hemodynamic monitoring, especially in cardio-surgical ICUs. However, its value as a prognostic marker for organ failure is still unclear. Therefore, we analyzed postoperative CVP values after adult cardiac surgery in a large cohort with regard to its prognostic value for morbidity and mortality. Methods: All adult patients admitted to our ICUs between 2006 and 2019 after cardiac surgery were eligible for inclusion in the study (n = 11,198). We calculated the median initial CVP (miCVP) after admission to the ICU, which returned valid values for 9802 patients. An ROC curve analysis for optimal cut-off miCVP to predict ICU mortality was conducted with consecutive patient allocation into a (a) low miCVP (LCVP) group (≤11 mmHg) and (b) high miCVP (HCVP) group (>11 mmHg). We analyzed the impact of high miCVP on morbidity and mortality by propensity score matching (PSM) and logistic regression. Results: ICU mortality was increased in HCVP patients. In addition, patients in the HCVP group required longer mechanical ventilation, had a higher incidence of acute kidney injury, were more frequently treated with renal replacement therapy, and showed a higher risk for postoperative liver dysfunction, parametrized by a postoperative rise of ≥ 10 in MELD Score. Multiple regression analysis confirmed HCVP has an effect on postoperative ICU-mortality and intrahospital mortality, which seems to be independent. Conclusions: A high initial CVP in the early postoperative ICU course after cardiac surgery is associated with worse patient outcome. Whether or not CVP, as a readily and constantly available hemodynamic parameter, should promote clinical efforts regarding diagnostics and/or treatment, warrants further investigations.

Clinical applications of the venous excess ultrasound (VExUS) score: conceptual review and case series

The importance of functional right ventricular failure and resultant splanchnic venous congestion has long been under-appreciated and is difficult to assess by traditional physical examination and standard diagnostic imaging. The recent development of the venous excess ultrasound score (VExUS) and growth of point-of-care ultrasound in the last decade has made for a potentially very useful clinical tool. We review the rationale for its use in several pathologies and illustrate with several clinical cases where VExUS was pivotal in clinical management.

The use of pulse pressure variation for predicting impairment of microcirculatory blood flow

Dynamic parameters of preload have been widely recommended to guide fluid therapy based on the principle of fluid responsiveness and with regard to cardiac output. An equally important aspect is however to also avoid volume-overload. This accounts particularly when capillary leakage is present and volume-overload will promote impairment of microcirculatory blood flow. The aim of this study was to evaluate, whether an impairment of intestinal microcirculation caused by volume-load potentially can be predicted using pulse pressure variation in an experimental model of ischemia/reperfusion injury. The study was designed as a prospective explorative large animal pilot study. The study was performed in 8 anesthetized domestic pigs (German landrace). Ischemia/reperfusion was induced during aortic surgery. 6 h after ischemia/reperfusion-injury measurements were performed during 4 consecutive volume-loading-steps, each consisting of 6 ml kg⁻¹ bodyweight⁻¹. Mean microcirculatory blood flow (mean Flux) of the ileum was measured using direct laser-speckle-contrast-imaging. Receiver operating characteristic analysis was performed to determine the ability of pulse pressure variation to predict a decrease in microcirculation. A reduction of ≥ 10% mean Flux was considered a relevant decrease. After ischemia–reperfusion, volume-loading-steps led to a significant increase of cardiac output as well as mean arterial pressure, while pulse pressure variation and mean Flux were significantly reduced (Pairwise comparison ischemia/reperfusion-injury vs. volume loading step no. 4): cardiac output (l min⁻¹) 1.68 (1.02–2.35) versus 2.84 (2.15–3.53), p = 0.002, mean arterial pressure (mmHg) 29.89 (21.65–38.12) versus 52.34 (43.55–61.14), p < 0.001, pulse pressure variation (%) 24.84 (17.45–32.22) versus 9.59 (1.68–17.49), p = 0.004, mean Flux (p.u.) 414.95 (295.18–534.72) versus 327.21 (206.95–447.48), p = 0.006. Receiver operating characteristic analysis revealed an area under the curve of 0.88 (CI 95% 0.73–1.00; p value < 0.001) for pulse pressure variation for predicting a decrease of microcirculatory blood flow. The results of our study show that pulse pressure variation does have the potential to predict decreases of intestinal microcirculatory blood flow due to volume-load after ischemia/reperfusion-injury. This should encourage further translational research and might help to prevent microcirculatory impairment due to excessive fluid resuscitation and to guide fluid therapy in the future.

The contemporary pulmonary artery catheter. Part 2: measurements, limitations, and clinical applications

Nowadays, the classical pulmonary artery catheter (PAC) has an almost 50-year-old history of its clinical use for hemodynamic monitoring. In recent years, the PAC evolved from a device that enabled intermittent cardiac output measurements in combination with static pressures to a monitoring tool that provides continuous data on cardiac output, oxygen supply and-demand balance, as well as right ventricular performance. In this review, which consists of two parts, we will introduce the difference between intermittent pulmonary artery thermodilution using bolus injections, and the contemporary PAC enabling continuous measurements by using a thermal filament which heats up the blood. In this second part, we will discuss in detail the measurements of the contemporary PAC, including continuous cardiac output measurement, right ventricular ejection fraction, end-diastolic volume index, and mixed venous oxygen saturation. Limitations of all of these measurements are highlighted as well. We conclude that thorough understanding of measurements obtained from the PAC is the first step in successful application of the PAC in daily clinical practice.

Inferior vena cava dilation predicts global cardiac dysfunction in acute respiratory distress syndrome: A strain echocardiographic study

PURPOSE

Limited data exist on the utility of ultrasonographic evaluation of inferior vena cava (IVC) in acute respiratory distress syndrome (ARDS). We studied the value of IVC diameter in assessing cardio-circulatory performance in ARDS using strain echocardiography.

MATERIALS AND METHODS

Retrospective cross-sectional analysis of Doppler echocardiograms of patients with moderate-severe ARDS was performed. Right ventricle (RV) parameters, IVC diameter, and left ventricle (LV) systolic and diastolic parameters were collected. RV free wall strain (RVFWS) and LV global longitudinal strain (LVGLS) were calculated.

RESULTS

Fifty-one patients were dichotomized into two groups: with IVC > 2.1 cm (dilated) and with IVC ≤ 2.1 cm (nondilated). The dilated IVC group presented worse hypoxemic profile, hypotension, and poor perfusion markers. No significant associations with positive end-expiratory pressure or lung mechanics were observed. Dilated IVC was associated with impaired RV function, high central venous pressure, elevated pulmonary artery pressure, and LV systolic and diastolic dysfunctions. Strongest predictors of a dilated IVC were RVFWS, LVGLS, and tissue Doppler mitral annular early diastolic velocity. Dilated IVC predicted a global cardiac dysfunction defined by strain echocardiography (GCDS) with high sensitivity and specificity.

CONCLUSIONS

In ARDS, strain echocardiography analyses demonstrated that a dilated IVC is associated with GCDS and impaired hemodynamics independent of lung mechanics. A dilated IVC should be considered a marker of circulatory distress, signaling the potential necessity for improved hemodynamic optimization.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Monitoring coherence between the macro and microcirculation in septic shock

PURPOSE OF REVIEW

Currently, the treatment of patients with shock is focused on the clinical symptoms of shock. In the early phase, this is usually limited to heart rate, blood pressure, lactate levels and urine output. However, as the ultimate goal of resuscitation is the improvement in microcirculatory perfusion the question is whether these currently used signs of shock and the improvement in these signs actually correspond to the changes in the microcirculation.

RECENT FINDINGS

Recent studies have shown that during the development of shock the deterioration in the macrocirculatory parameters are followed by the deterioration of microcirculatory perfusion. However, in many cases the restoration of adequate macrocirculatory parameters is frequently not associated with improvement in microcirculatory perfusion. This relates not only to the cause of shock, where there are some differences between different forms of shock, but also to the type of treatment.

SUMMARY

The improvement in macrohemodynamics during the resuscitation is not consistently followed by subsequent changes in the microcirculation. This may result in both over-resuscitation and under-resuscitation leading to increased morbidity and mortality. In this article the principles of coherence and the monitoring of the microcirculation are reviewed.

Monitoring peripheral perfusion in sepsis associated acute kidney injury: Analysis of mortality

Microcirculatory disorders have been consistently linked to the pathophysiology of sepsis. One of the major organs affected is the kidneys, resulting in sepsis-associated acute kidney injury (SA-AKI) that correlates considerably with mortality. However, the potential role of clinical assessment of peripheral perfusion as a possible tool for SA-AKI management has not been established. To address this gap, the purpose of this study was to investigate the prevalence of peripheral hypoperfusion in SA-AKI, its association with mortality, and fluid balance. This observational cohort study enrolled consecutive septic patients in the Intensive Care Unit. After fluid resuscitation, peripheral perfusion was evaluated using the capillary filling time (CRT) and peripheral perfusion index (PI) techniques. The AKI was defined based on both serum creatinine and urine output criteria. One hundred and forty-one patients were included, 28 (19%) in the non-SA-AKI group, and 113 (81%) in the SA-AKI group. The study revealed higher peripheral hypoperfusion rates in the SA-AKI group using the CRT (OR 3.6; 95% CI 1.35-9.55; p < 0.05). However, this result lost significance after multivariate adjustment. Perfusion abnormalities in the SA-AKI group diagnosed by both CRT (RR 1.96; 95% CI 1.25-3.08) and PI (RR 1.98; 95% CI 1.37-2.86) methods were associated to higher rates of 28-day mortality (p < 0.01). The PI's temporal analysis showed a high predictive value for death over the first 72 h (p < 0.01). A weak correlation between PI values and the fluid balance was found over the first 24 h (r = - 0.20; p < 0.05). In conclusion, peripheral perfusion was not different intrinsically between patients with or without SA-AKI. The presence of peripheral hypoperfusion in the SA-AKI group has appeared to be a prognostic marker for mortality. This evaluation maintained its predictive value over the first 72 hours. The fluid balance possibly negatively influences peripheral perfusion in the SA-AKI.

Microcirculation-guided protection strategy in hemodynamic therapy

Microcirculatory shock is a condition defined by the presence of tissue hypoperfusion despite the normalization of systemic and regional blood flow. Currently, more evidence shows that intrinsic septic shock is microcirculatory shock, which results in septic shock that is difficult to resuscitate. At present, treatments are aimed at recovering macro-circulation functions and include fluid resuscitation, vasoactive drugs, positive inotropic drugs, de-obstruction, and even mechanical assistance to improve oxygen delivery. However, the application of these treatments to more accurately improve microcirculation or avoid further microcirculatory damage is more important in clinics. In this article, we discuss the need for microcirculation protection and microcirculation-guided protection strategies in hemodynamic therapies.

A narrative review of pharmacologic de-resuscitation in the critically ill

Despite evidence highlighting harms of fluid overload, minimal guidance exists on counteraction via utilization of diuretics in the de-resuscitation phase. While diuretics have been shown to decrease net volume and improve clinical outcomes in the critically ill, a lack of standardization surrounding selection of diuretic regimen or monitoring of de-resuscitation exists. Current monitoring parameters of de-resuscitation often rely on clinical signs of fluid overload, end organ recovery and other biochemical surrogate markers which are often deemed unreliable. The majority of evidence suggests that achieving a net-negative fluid balance within 72 h after shock resolution may be of benefit; however, approaches to such goal are uncertain. Loop diuretics are a widely available type of diuretic for removal of volume in patients with sufficient kidney function, with the potential for adjunct diuretics in special circumstances. At present, administration of diuretics within the broad critically ill population fails to find uniformity and often efficacy. Given the lack of randomized controlled trials in this susceptible population, we aim to provide a thorough therapeutic understanding of diuretic pharmacotherapy which is necessary in order to achieve desired goal of fluid balance and improve overall outcomes.

Assessment of sublingual microcirculation in critically ill patients: consensus and debate

The main concern in shock and resuscitation is whether the microcirculation can carry adequate oxygen to the tissues and remove waste. Identification of an intact coherence between macro- and microcirculation during states of shock and resuscitation shows a functioning regulatory mechanism. However, loss of hemodynamic coherence between the macro and microcirculation can be encountered frequently in sepsis, cardiogenic shock, or any hemodynamically compromised patient. This loss of hemodynamic coherence results in an improvement in macrohemodynamic parameters following resuscitation without a parallel improvement in microcirculation resulting in tissue hypoxia and tissue compromise. Hand-held vital microscopes (HVMs) can visualize the microcirculation and help to diagnose the nature of microcirculatory shock. Although treatment with the sole aim of recruiting the microcirculation is as yet not realized, interventions can be tailored to the needs of the patient while monitoring sublingual microcirculation. With the help of the newly introduced software, called MicroTools, we believe sublingual microcirculation monitoring and diagnosis will be an essential point-of-care tool in managing shock patients.

Fluid resuscitation in sepsis: the great 30 mL per kg hoax

Large volume fluid resuscitation is currently viewed as the cornerstone of the treatment of septic shock. The surviving sepsis campaign (SSC) guidelines provide a strong recommendation to rapidly administer a minimum of 30 mL/kg crystalloid solution intravenously in all patients with septic shock and those with elevated blood lactate levels. However, there is no credible evidence to support this recommendation. In fact, recent findings from experimental, observational and randomized clinical trials demonstrate improved outcomes with a more restrictive approach to fluid resuscitation. Accumulating evidence suggests that aggressive fluid resuscitation is harmful. Paradoxically, excess fluid administration may worsen shock. In this review, we critically evaluate the scientific evidence for a weight-based fluid resuscitation approach. Furthermore, the potential mechanisms and consequences of harm associated with fluid resuscitation are discussed. Finally, we recommend an individualized, conservative and physiologic guided approach to fluid resuscitation.

Early initiation renal replacement therapy for fluid management to reduce central venous pressure is more conducive to renal function recovery in patients with acute kidney injury

Background:

Acute kidney injury (AKI) is a serious complication in critically ill patients with septic shock treated in the intensive care unit. Renal replacement therapy (RRT) is a treatment for severe AKI; however, the time of initiation of RRT and factors that affect the recovery of kidney function remains unclear. This study was to explore whether early initiation of RRT treatment for fluid management to reduce central venous pressure (CVP) can help to improve patients’ kidney function recovery.

Methods:

A retrospective analysis of septic patients who had received RRT treatment was conducted. Patients received RRT either within 12 h after they met the diagnostic criteria of renal failure (early initiation) or after a delay of 48 h if renal recovery had not occurred (delayed initiation). Parameters such as patients’ renal function recovery at discharge, fluid balance, and levels of CVP were assessed.

Results:

A total of 141 patients were eligible for enrolment: 40.4% of the patients were in the early initiation group (57 of 141 patients), and 59.6% were in the delayed initiation group (84 of 141 patients). There were no significant differences in the characteristics at baseline between the two groups, and there were no differences in 28-day mortality between the two groups (χ² = 2.142, P = 0.143); however, there was a significant difference in the recovery rate of renal function between the two groups at discharge (χ² = 4.730, P < 0.001). More importantly, early initiation of RRT treatment and dehydration to reduce CVP are more conducive to the recovery of renal function in patients with AKI.

Conclusion:

Compared with those who received delayed initiation RRT, patients who received early-initiation RRT for dehydration to reduce CVP have enhanced kidney function recovery.

Postoperative diastolic perfusion pressure is associated with the development of acute kidney injury in patients after cardiac surgery: a retrospective analysis

Background

We aimed to investigate the relationship between the perioperative hemodynamic parameters and the occurrence of cardiac surgery-associated acute kidney injury.

Methods

A retrospective study was performed in patients who underwent cardiac surgery at a tertiary referral teaching hospital. Acute kidney injury was determined according to the KDIGO criteria. We investigated the association between the perioperative hemodynamic parameters and cardiac surgery-associated acute kidney injury to identify the independent hemodynamic predictors for acute kidney injury. Subgroup analysis was further performed in patients with chronic hypertension.

Results

Among 300 patients, 29.3% developed acute kidney injury during postoperative intensive care unit period. Multivariate logistic analysis showed the postoperative nadir diastolic perfusion pressure, but not mean arterial pressure, central venous pressure and mean perfusion pressure, was independently linked to the development of acute kidney injury after cardiac surgery (odds ratio 0.945, P = 0.045). Subgroup analyses in hypertensive subjects (n = 91) showed the postoperative nadir diastolic perfusion pressure and peak central venous pressure were both independently related to the development of acute kidney injury (nadir diastolic perfusion pressure, odds ratio 0.886, P = 0.033; peak central venous pressure, odds ratio 1.328, P = 0.010, respectively).

Conclusions

Postoperative nadir diastolic perfusion pressure was independently associated with the development of cardiac surgery-associated acute kidney injury. Furthermore, central venous pressure should be considered as a potential hemodynamic target for hypertensive patients undergoing cardiac surgery.

Fluid balance correlates with clinical course of multiple organ dysfunction syndrome and mortality in patients with septic shock

Introduction

Positive fluid balance is a prognostic factor for mortality in patients with sepsis; however, the association between cumulated fluid balance (CFB) and sepsis-induced multi-organ dysfunction syndrome (MODS) has yet to be elucidated. In this study, we sought to determine whether CFB is correlated with MODS and mortality in cases of septic shock.

Methods

The study retrospectively recruited patients with septic shock from the intensive care unit of a tertiary care hospital. Multiple organ dysfunction syndrome (MODS) was identified as sequential organ failure assessment (SOFA) score ≥ 2 in more than one organ system. The CFB is the sum of all daily intake and output. An independent t-test, single and multivariate logistic regression, the receiver operating characteristic (ROC) curves, and the Pearson correlation coefficient were used to determine whether a relationship exists between CFB and the development of MODS and mortality.

Results

Among the 104 patients enrolled in the study, 58 (55.8%) survived more than 28 days, and 73 (70.2%) developed MODS on day 3. The values of CFB in the first 24 hours and 72 hours after diagnosis of septic shock in patients with MODS were higher than these in patients without MODS (1086.6 ± 176.3 vs. 325.5 ± 205.7 ml, p = 0.013 and 2408 ± 361 vs. 873.1 ± 489 ml, p < 0.0001). In a multivariate logistic regression, the independent factors associated with the development of MODS on day 3 were APACHE II score at ICU admission (27.6 ± 7.6 in patients with MODS vs. 20.5 ± 6.4 in those without; O.R. 1.18; 95% C.1 I. 1.08–1.30; p < 0.001), disseminated intravascular coagulopathy (DIC) (n = 28; 38.4% vs. n = 2; 6.5%; O.R. 23.67; 95% C.I. 3.58–156.5; p = 0.001), and CFB in the first 72 hours (72-hr CFB) > median (1767.50ml) (n = 41; 56.2% vs. n = 11; 35.5%; O.R. 3.67; 95% C.I., 1.18–11.40; p = 0.024). Moreover, a multivariate logistic regression also identified neoplasm (n = 25; 54.3% vs. n = 17; 29.3%; O.R. 3.45; 95% C.I. 1.23–10.0; p = 0.019) and 72-hr CFB > median (n = 30; 65.2% vs. n = 21; 36.2%; O.R. 4.13; 95% C.I. 1.34–12.66; p = 0.013) as independent factors associated with 28-day mortality. 72-hr CFB values were strongly correlated with the SOFA score (r = 0.445, p < 0.0001). The area under the ROC curve revealed that 72-hr CFB has good discriminative power in associating the development of MODS (0.644, p = 0.002) and predicting subsequent 28-day mortality (0.704, p < 0.0001).

Conclusions

72-hr CFB appears to be correlated with the likelihood of developing MODS and mortality in patients with septic shock. Thus, it appears that 72-hr CFB could perhaps be used as an indicator for MODS and a predictor for mortality in those patients.

Central Venous Pressure (CVP) Reduction Associated With Higher Cardiac Output (CO) Favors Good Prognosis of Circulatory Shock: A Single-Center, Retrospective Cohort Study

Background: The Frank-Starling curve is the basis of hemodynamics. Changes in cardiac output (CO) caused by central venous pressure (CVP) are the most important concerns in the treatment of critically ill patients.

Objectives: To explore the use of CVP and its relevant mechanisms with respect to CO in the clinic.

Methods: A total of 134 patients with circulatory shock were retrospectively included and analyzed. Hemodynamic data were recorded and analyzed at PICCO initiation and 24 h after PICCO. Data regarding 28-day mortality and renal function were also collected.

Results: The patients were divided into a CVP↑+ CO↑ group (n = 23), a CVP↑+ CO↓ group (n = 29), a CVP↓+ CO↑ group (n = 44), and a CVP↓+ CO↓ group (n = 38) based on values at PICCO initiation and 24 h after PICCO. Post- hoc tests showed that the CVP↓+ CO↑ group had a higher 28-day survival than the other groups [log-rank (Mantel-Cox) = 8.758, 95%, CI, 20.112–23.499, P = 0.033]. In terms of hemodynamic characteristics, the CVP↓+ CO↑ group had a lower cardiac function index (CFI) (4.1 ± 1.4/min) and higher extravascular lung water index (EVLWI) (11.0 ± 4.7 ml/kg) at PICCO initiation. This group used more cardiotonic drugs (77.3%, P < 0.001) and had a negative fluid balance (−780.4 ± 1720.6 ml/24 h, P = 0.018) 24 h after PICCO than the other three groups. Cardiotonic drug use and dehydration treatment were associated with increased CFI (from 4.1 ± 1.4 /min to 4.5 ± 1.3/min, P = 0.07) and reduced ELVWI (from 11.0 ± 4.7 ml/kg to 9.0 ± 3.5 ml/kg, P = 0.029). Renal function tests showed that SCr and BUN levels in the CVP↓+ CO↑ group were significantly improved (SCr from 197.1 ± 128.9 mmol/L to 154.4 ± 90.8 mmol/L; BUN from 14.3 μmol/L ± 7.3 to 11.6 ± 7.0 μmol/L, P < 0.05).

Conclusions: Lower CVP was associated with increased CO, which may improve the 28-day prognosis in patients with circulatory shock. Notably, higher CO derived from lower CVP may also contribute to renal function improvement.

Microcirculation in Cardiovascular Diseases

Microcirculation is a system composed of interconnected microvessels, which is responsible for the distribution of oxygenated blood among and within organs according to regional metabolic demand. Critical medical conditions, e. g., sepsis, and heart failure are known triggers of microcirculatory disturbance, which usually develops early in such clinical pictures and represents an independent risk factor for mortality. Therefore, hemodynamic resuscitation aiming at restoring microcirculatory perfusion is of paramount importance. Until recently, however, resuscitation protocols were based on macrohemodynamic variables, which increases the risk of under or over resuscitation. The introduction of hand-held video-microscopy (HVM) into clinical practice has allowed real-time analysis of microcirculatory variables at the bedside and, hence, favored a more individualized approach. In the cardiac intensive care unit scenario, HVM provides essential information on patients' hemodynamic status, e. g., to classify the type of shock, to adequate the dosage of vasopressors or inotropes according to demand and define safer limits, to guide fluid therapy and red blood cell transfusion, to evaluate response to treatment, among others. Nevertheless, several drawbacks have to be addressed before HVM becomes a standard of care.

Serum heart-type fatty acid-binding protein as a predictor for the development of sepsis-associated acute kidney injury

Background: We analyzed the correlation between heart-type fatty acid-binding protein (HFABP) and the development of acute kidney injury (AKI) in patients with sepsis and estimated the predictive capacity of HFABP for sepsis-associated acute kidney injury (SAKI). Methods: In this retrospective observational study, we screened 2,452 patients who received the HFABP test in the emergency department. 442 admitted patients with sepsis were finally enrolled. Based on the diagnostic criteria for AKI in Kidney Disease: Improving Global Outcomes (KDIGO) guidelines, patients were divided into the no-AKI group (n = 317) and AKI group (n = 125). We analyzed the correlation between HFABP and SAKI occurrence by logistic regression analysis and evaluated the predictive ability of HFABP to SAKI using c-index, net reclassification improvement index (NRI) and integrated discrimination improvement index (IDI). Results: Patients in the AKI group with significantly higher the level of HFABP and in-hospital mortality. HFABP concentration is an independent risk factor for SAKI (OR: 11.398; 95% CI: 6.218-20.891, P < 0.001), but not for in-hospital mortality (OR: 1.189, 95%CI: 0.954-2.607, P = 0.076). The addition of HFABP to the prediction model significantly improved the ROC area (0.867 vs 0.755, P < 0.001), NRI 25.03% (95% CI 9.72-38.51%) and IDI 14.33 (95% CI 11.04-17.62). Conclusion: Serum HFABP is correlated with SAKI development and could become a potential predictive biomarker.

Effects of high PEEP and fluid administration on systemic circulation, pulmonary microcirculation, and alveoli in a canine model

This study aimed to determine the response of systemic circulation, pulmonary microcirculation, and alveoli to high positive end-expiratory pressure (PEEP) in a canine model. This study was conducted in nine mixed-breed dogs on mechanical ventilation under anesthesia. The PEEP was initially set at 5 cmH₂O (PEEP₅), the PEEP was then increased to 25 cmH₂O (PEEP₂₅), and then saline was used for fluid loading. Data were obtained at the following time points: PEEP₅; PEEP₂₅ prefluid loading; and PEEP₂₅ postfluid loading. The images of subpleural lung microcirculation were assessed by sidestream dark-field microscopy, and the hemodynamic data were collected from pulse contour waveform-derived measurements. Compared with PEEP_5, the lung microvascular flow index (MFI, 2.3 ± 0.8 versus 0.9 ± 0.8, P = 0.001), lung perfused vessel density (PVD, 4.2 ± 2 versus 1.5 ± 1.8, P = 0.004), lung proportion of perfused vessel (PPV, 93 ± 14 versus 40 ± 4, P = 0.003), cardiac output (2.5 ± 0.6 versus 1.4 ± 0.5, P = 0.001), and mean blood pressure (116 ± 24 versus 91 ± 31, P = 0.012) were significantly lower at PEEP₂₅ prefluid loading. After fluid loading, there were no significant differences in cardiac output or mean arterial pressure between the PEEP₅ and PEEP₂₅ postfluid loading levels. However, the lung microcirculatory MFI, PVD, and PPV at PEEP₂₅ postfluid loading remain lower than at PEEP₅. A significant increase in septal thickness was found at PEEP₂₅ postfluid loading relative to septal thickness at PEEP₂₅ prefluid loading (25.98 ± 5.31 versus 40.76 ± 7.9, P = 0.001). Under high PEEP, systemic circulation was restored after fluid loading, but lung microcirculation was not. Moreover, the septal thickness of alveoli significantly increased after fluid loading.NEW & NOTEWORTHY An excessively high positive end-expiratory pressure (PEEP) can impair the systemic circulation and alveolar microcirculation. In the high-PEEP condition, fluid loading restored the systemic circulation but did not affect the impaired lung microcirculation. The septal thickness of the alveoli significantly increased after fluid loading in the high-PEEP condition.

Influence of systemic hemodynamics on microcirculation during sepsis

PURPOSE

During sepsis, improvement of hemodynamic may not be related to improvement of microcirculation. The aim of this study was to investigate influence of systemic circulation on microcirculation in septic ICU patients.

METHODS

This is a prospective cohort study of septic ICU patients. Microcirculation was investigated with Near infrared spectrometry (NIRS) measuring tissue oxygen saturation (StO₂). StO₂ desaturation (desStO₂) and resaturation (resStO₂) slopes were determined. Analyses were made at baseline and after fluid challenges.

RESULTS

Seventy-two patients were included. One hundred and sixty measures were performed at baseline. StO₂ was 77.8% [72.4-85.0] and resStO₂ was 87.3%/min [57.8-141.7]. Univariate analysis showed an association between resStO₂ and diastolic arterial pressure (DAP) (p = .001), and norepinephrine dose (p = .033). In multivariate linear regression, there was an association between resStO₂ and DAP (β = 1.85 (0.64 to 3.08), p = .004)_. Fluid challenges (n = 60) increased CO, and resStO₂ (all p < .001). In multivariate analysis, variation of stroke volume was associated with variation of resStO₂ (p = .004) after fluid challenge. There was no association between CVP and resStO₂.

CONCLUSIONS

DAP was the only independent determinant of resStO2 in septic patients. Fluid challenges may improve microcirculation. CVP did not influence resStO₂.

Fluid therapy in non-septic, refractory acute decompensated heart failure patients - The cautious role of central venous pressure

PURPOSE

Fluid therapy in congestive acute decompensated heart failure (ADHF) patients might be inappropriate and worsening the prognosis. The aim of our study was to analyze the effect of fluid administration on mortality in non-septic, ADHF patients with reduced ejection fraction.

MATERIAL AND METHODS

We analyzed 41 ADHF consecutive 'cold-wet' patients (mean age 69.3 ± 14.9 years, 27 men, LVEF 22.8 ± 11.1%, lactates 2.2 ± 1.6 mmol/L) without sepsis. At admission central venous pressure (CVP) was measured (17.6 ± 7.2 cm H₂O), and ultrasound examination of inferior vena cava (IVC) was performed (IVC min. 18.6 ± 7.3 mm and IVC max. 24.6 ± 4.3 mm). Moreover, the groups were compared (survivors vs. non-survivors as well as 1st and 4th quartile of CVP).

RESULTS

Altogether 17 (41%) patients died: 16 (39%) during a mean of 11.2 ± 7.8 days of hospitalization and 1 during a 30-day follow up. Patients in the lowest CVP quartile (<13 cm H₂O) had significantly worse in-hospital survival as compared to patients in the highest quartile (>24 cm H₂O), P = 0.012. Higher intravenous fluid volumes within the first 24 h were infused in patients in the lowest CVP quartile as compared to the highest CVP quartile (1791.7 ± 1357.8 mL vs. 754.5 ± 631.4 mL, P = 0.046). Moreover, more fluids were infused in a group of patients who died during a hospital stay and at 30-day follow up (1362.8 ± 752.7 mL vs. 722.7 ± 1046.5 mL, P = 0.004; 1348.8 ± 731.0 mL vs. 703.6 ± 1068.4 mL, P = 0.002, respectively).

CONCLUSIONS

CVP-guided intravenous fluid therapy is a common practice which in high risk ADHF 'cold-wet' patients might be harmful and should rather be avoided. Lower CVP seems to be related with worse prognosis.

Impaired right ventricular ejection fraction after cardiac surgery is associated with a complicated ICU stay

Background

Right ventricular (RV) dysfunction is a known risk factor for increased mortality in cardiac surgery. However, the association between RV performance and ICU morbidity is largely unknown.

Methods

We performed a single-centre, retrospective study including cardiac surgery patients equipped with a pulmonary artery catheter, enabling continuous right ventricular ejection fraction (RVEF) measurements. Primary endpoint of our study was ICU morbidity (as determined by ICU length of stay, duration of mechanical ventilation, usage of inotropic drugs and fluids, and kidney dysfunction) in relation to RVEF. Patients were divided into three groups according to their RVEF; < 20%, 20-30%, and > 30%.

Results

We included 1109 patients. Patients with a RVEF < 20% had a significantly longer stay in ICU, a longer duration of mechanical ventilation, higher fluid balance, a higher incidence of inotropic drug usage, and more increase in postoperative creatinine levels in comparison to the other subgroups. In a multivariate analysis, RVEF was independently associated with increased ICU length of stay (OR 0.934 CI 0.908-0.961, p < 0.001), prolonged duration of mechanical ventilation (OR 0.969, CI 0.942-0.998, p = 0.033), usage of inotropic drugs (OR 0.944, CI 0.917-0.971, p < 0.001), and increase in creatinine (OR 0.962, CI 0.934-0.991, p = 0.011).

Conclusions

A decreased RVEF is independently associated with a complicated ICU stay.

Risk indicators for acute kidney injury in cardiogenic shock

PURPOSE

In critical illness, the relation between the macrocirculation, microcirculation and organ dysfunction, such as acute kidney injury (AKI), is complex. This study aimed at identifying predictors for AKI in patients with cardiogenic shock.

MATERIALS AND METHODS

Thirty-nine adult cardiogenic shock patients, with an admission creatinine <200 μmol l^-1, and whose microcirculation was measured within 48 h were enrolled. Patient data were analyzed if AKI stage ≥1 developed according to the Kidney Disease/Improving Outcomes classification within 48 h after admission. Variables with a p < .05 in the univariate analysis were considered for analysis with logistic regression.

RESULTS

Twenty-four patients (61.5%) developed AKI within 48 h. The group that developed AKI had higher central venous pressures (CVP), lower diastolic arterial blood pressures and mean perfusion pressures, higher maximum ventilator pressures as well as positive end expiratory pressures and were treated with higher dosages of dobutamine. There was no difference of the microcirculation. In the multivariate logistic regression analysis, CVP was the only independent predictor for AKI (OR 1.241; 95% CI 1.030-1.495; p = .023).

CONCLUSIONS

In this population of patients with cardiogenic shock, CVP was associated with the development of AKI.

High central venous pressure is associated with acute kidney injury and mortality in patients underwent cardiopulmonary bypass surgery

PURPOSE

We sought to investigate the relationship between high CVP, AKI, and mortality in patients undergoing cardiac surgery with cardiopulmonary bypass.

MATERIALS

All patients aged 18 years or older who underwent cardiac surgery with CPB were prospectively reviewed. Patients were excluded when renal artery were involved before and during surgery. Patients were dichotomized into high CVP group(>10 mmHg) and low CVP group(<10 mmHg). All patients were followed by telephone.

RESULTS

A total of 1941 patients were included in observed study. In high CVP group, three hundred forty-seven patients (43.32%) developed AKI, while eighty-six (7.543%) in low CVP group(P <0.0001). Furthermore, in every KDIGO stage, patients of AKI in high CVP group were more than those in low CVP group(P <0.0001). The incidence of AKI increased as CVP increased, especially when CVP was higher than 10cmH2O. In a median follow-up time of 9.2 months, Crude mortality is 8.365% in the high CVP group compared to 1.929% in the low CVP group (p<0.0001). In multivariate analysis, CVP remained the independent predictor of survival.

CONCLUSIONS

High CVP is associated with AKI , and it is independently related to all-cause mortality in patients underwent cardiovascular surgery with cardiopulmonary bypass.

Effect of pneumoperitoneum and steep reverse-Trendelenburg position on mean systemic filling pressure, venous return, and microcirculation during esophagectomy

Background

Keeping adequate tissue perfusion during high-risk abdominal surgery is of utmost importance to decrease postoperative complications. The objective was to investigate the alteration in mean systemic filling pressure (MSFP), venous return (VR) and sublingual microcirculation during pneumoperitoneum and steep reverse-Trendelenburg position during thoracolaparoscopic esophagectomy.

Methods

This is a single-center prospective observational study in operating room at a university hospital. Eleven consecutive patients undergoing minimally invasive esophagectomy. Intraoperative hemodynamic and sublingual microcirculatory variables were simultaneously measured within 5 minutes at the following time points: T1, baseline supine position before the start of surgery; T2, pneumoperitoneum in supine position; T3, steep reverse-Trendelenburg position after the pneumoperitoneum. The cardiac output (CO) was obtained with continuous pulse contour waveform-derived measurements, and the MSFP was estimated with the analogue method.

Results

The pneumoperitoneum and reverse-Trendelenburg caused an increase in stroke volume variation (SVV), MSFP and central venous pressure (CVP), and a decrease in the microcirculatory perfusion index (MFI, <0.05). However, changes in CO, pressure gradient of VR, resistance of VR and blood pressure were not consistent and did not differ significantly across timepoints. Moreover, MFI is significantly related to CVP and MSFP but not to CO and blood pressure (BP). Measurements with MFI ≤2 have a higher CVP and MSFP compared to those with MFI >2. Using a CVP ≥23 mmHg to detect MFI ≤2 results in a sensitivity of 61.54% and a specificity of 100%.

Conclusions

A high CVP is related to poor microcirculatory flow perfusion even if the macrocirculation has been maintained during pneumoperitoneum.

Monitoring microcirculation in critical illness

PURPOSE OF REVIEW

Critical illness includes a wide range of conditions from sepsis to high-risk surgery. All these diseases are characterized by reduced tissue oxygenation. Macrohemodynamic parameters may be corrected by fluids and/or vasoactive compounds; however, the microcirculation and its tissues may be damaged and remain hypoperfused. An evaluation of microcirculation may enable more physiologically based approaches for understanding the pathogenesis, diagnosis, and treatment of critically ill patients.

RECENT FINDINGS

Microcirculation plays a pivotal role in delivering oxygen to the cells and maintains tissue perfusion. Negative results of several studies, based on conventional hemodynamic resuscitation procedures to achieve organ perfusion and decrease morbidity and mortality following conditions of septic shock and other cardiovascular compromise, have highlighted the need to monitor microcirculation. The loss of hemodynamic coherence between the macrocirculation and microcirculation, wherein improvement of hemodynamic variables of the systemic circulation does not cause a parallel improvement of microcirculatory perfusion and oxygenation of the essential organ systems, may explain why these studies have failed.

SUMMARY

Critical illness is usually accompanied by abnormalities in microcirculation and tissue hypoxia. Direct monitoring of sublingual microcirculation using hand-held microscopy may provide a more physiological approach. Evaluating the coherence between macrocirculation and microcirculation in response to therapy seems to be essential in evaluating the efficacy of therapeutic interventions.