Accuracy of Mean Value of Central Venous Pressure from Monitor Digital Display: Influence of Amplitude of Central Venous Pressure during Respiration

Background A simple measurement of central venous pressure(CVP)-mean by the digital monitor display has become increasingly popular.However,the agreement between CVP-mean and CVP-end(a standard method of CVP measurement by analyzing the waveform at end-expiration)is not well determined.This study was designed to identify the relationship between CVP-mean and CVP-end in critically ill patients and to introduce a new parameter of CVP amplitude(ΔCVP=CVPmax-CVPmin)during the respiratory period to identify the agreement/disagreement between CVP-mean and CVP-end.Methods In total,291 patients were included in the study.CVP-mean and CVP-end were obtained simultaneously from each patient.CVP measurement difference(|CVP-mean-CVP-end|)was defined as the difference between CVP-mean and CVP-end.TheΔCVP was calculated as the difference between the peak(CVPmax)and the nadir value(CVPmin)during the respiratory cycle,which was automatically recorded on the monitor screen.Subjects with|CVP-mean-CVP-end|≥2 mm Hg were divided into the inconsistent group,while subjects with|CVP-mean-CVP-end|2 mm Hg were divided into the consistent group.ResultsΔCVP was significantly higher in the inconsistent group[7.17(2.77)vs.5.24(2.18),P0.001]than that in the consistent group.There was a significantly positive relationship betweenΔCVP and|CVP-mean-CVP-end|(r=0.283,P 0.0001).Bland-Altman plot showed the bias was-0.61 mm Hg with a wide 95%limit of agreement(-3.34,2.10)of CVP-end and CVP-mean.The area under the receiver operating characteristic curves(AUC)ofΔCVP for predicting|CVP-mean-CVP-end|≥2 mm Hg was 0.709.With a high diagnostic specificity,usingΔCVP3 to detect|CVP-mean-CVP-end|lower than 2mm Hg(consistent measurement)resulted in a sensitivity of 22.37%and a specificity of 93.06%.UsingΔCVP8 to detect|CVP-mean-CVPend|8 mm Hg(inconsistent measurement)resulted in a sensitivity of 31.94%and a specificity of 91.32%.Conclusions CVP-end and CVP-mean have statistical discrepancies in specific clinical scenarios.ΔCVP during the respiratory period is related to the variation of the two CVP methods.A highΔCVP indicates a poor agreement between these two methods,whereas a lowΔCVP indicates a good agreement between these two methods.

Role of Combining Peripheral with Sublingual Perfusion on Evaluating Microcirculation and Predicting Prognosis in Patients with Septic Shock

Background： Measurement of general microcirculation remains difficult in septic shock patients. The peripheral perfusion index （PI） and sublingual microcirculation monitoring are thought to be possible methods. This study was pertbrmed to determine whether assessing microcirculation by PI and a new parameter, proportion of perfusion vessel change rate （APPV） from sublingual microcirculation monitoring, can be associated with patients＇ outcome. Methods： A prospective observational study was carried out, including 74 patients with septic shock in a mixed intensive care unit. Systemic hemodynamic variables were obtained at TO and 6 h after （T6）. PI and sublingual microcirculation indicators were obtained using a bedside monitor and a sidestream dark-field device, respectively. The t-test, analysis of variance, Mann-Whitney U-test, Kruskal- Wallis test, receiver operating characteristic curve analysis with the Hanley-McNeil test, survival curves using the Kaplan-Meier method, and the log-rank （Mantel-Cox） test were used to statistical analysis. Results： Systemic hemodynamics and microcirculation data were obtained and analyzed. Patients were divided into two groups based on whether the first 6 h lactate clearance （LC） was 〉20%; PI and APPV were lower at T6 in the LC 〈20% group compared with LC ≥20% （PI： 1.52 [0.89, 1.98] vs. 0.79 [0.44, 1,81], Z = -2.514, P - 0.012; APPV： 5.9 ±15.2 vs. 17.9 ± 20.0, t = -2.914, P = 0.005）. The cutoff values of PI and APPV were 1.41% and l 2.1%, respectively. The cutoff value of the combined indicators was 1.379 according to logistic regression. Area under the curve demonstrated 0.709 （P 〈 0.05）, and the sensitivity and specificity of using combined indicators were 0.622 and 0.757, respectively. Based on the PI and APPV cutoff; all the participants were divided into the following groups： （1） high PI and high APPV group, （2） high PI and low APPV group, （3） low PI and high zXPPV group, and （4） low PI and low APPV group. The highest Sequential Organ Failure Assessment score （14.5 ± 2.9） was in the low P1 and low APPV group （F = 13.7, P 〈 0.001）. Post hoc tests showed significant differences in 28-day survival rates among these four groups （log rank [Mantel-Cox], 20.931 ; P 〈 0.05）. Conclusion： Pl and APPV in septic shock patients are related to 6 h LC, and combining these two parameters to assess microcirculation can predict organ dysfunction and 28-day mortality in patients with septic shock.

Positive End-expiratory Pressure Titration after Alveolar Flecruitment Directed by Electrical Impedance Tomography

Background： Electrical impedance tomography （EIT） is a real-time bedside monitoring tool, which can reflect dynamic regional lung ventilation. The aim of the present study was to monitor regional gas distribution in patients with acute respiratory distress syndrome （ARDS） during positive-end-expiratory pressure （PEEP） titration using EIT. Methods： Eighteen ARDS patients under mechanical ventilation in Department of Critical Care Medicine of Peking Union Medical College Hospital from January to April in 2014 were included in this prospective observational study. After recruitment maneuvers （RMs）, decremental PEEP titration was performed from 20 cmH20 to 5 cmH20 in steps of 3 cmH20 every 5-10 min. Regional over-distension and recruitment were monitored with EIT. Results： After RMs, patient with arterial blood oxygen partial pressure （PaO2） ＋ carbon dioxide partial pressure （PaCO2） 〉400 mmHg with 100% of fractional inspired oxygen concentration were defined as RM responders. Thirteen ARDS patients was diagnosed as responders whose PaO2 ＋ PaCO2, were higher than nonresponders （419 ± 44 mmHg vs. 170 ±73 mmHg, P 〈 0.0001）. In responders, PEEP mainly increased-recruited pixels in dependent regions and over-distended pixels in nondependent regions. PEEP alleviated global inhomogeneity of tidal volume and end-expiratory lung volume. PEEP levels without significant alveolar derecruitment and over-distension were identified individually. Conclusions： After RMs, PEEP titration significantly affected regional gas distribution in lung, which could be monitored with EIT. EIT has the potential to optimize PEEP titration.

Effect of mean arterial pressure change by norepinephrine on peripheral perfusion index in septic shock patients after early resuscitation

Background:The peripheral perfusion index(PI),as a real-time bedside indicator of peripheral tissue perfusion,may be useful for determining mean arterial pressure(MAP)after early resuscitation of septic shock patients.The aim of this study was to explore the response of PI to norepinephrine(NE)-induced changes in MAP.Methods:Twenty septic shock patients with pulse-induced contour cardiac output catheter,who had usual MAP under NE infusion after early resuscitation,were enrolled in this prospective,open-label study.Three MAP levels(usual MAP-10 mmHg,usual MAP,and usual MAP+10 mmHg)were obtained by NE titration,and the corresponding global hemodynamic parameters and PI were recorded.The general linear model with repeated measures was used for analysis of variance of related parameters at three MAP levels.Results:With increasing NE infusion,significant changes were found in MAP(F=502.46,P<0.001)and central venous pressure(F=27.45,P<0.001)during NE titration.However,there was not a significant and consistent change in continuous cardiac output(CO)(F=0.41,P=0.720)and PI(F=0.73,P=0.482)at different MAP levels.Of the 20 patients enrolled,seven reached the maximum PI value at usual MAP-10 mmHg,three reached the maximum PI value at usual MAP,and ten reached the maximum PI value at usual MAP+10 mmHg.The change in PI was not significantly correlated with the change in CO(r=0.260,P=0.269)from usual MAP-10 mmHg to usual MAP.There was also no significant correlation between the change in PI and change in CO(r=0.084,P=0.726)from usual MAP to usual MAP+10 mmHg.Conclusions:Differing MAP levels by NE infusion induced diverse PI responses in septic shock patients,and these PI responses may be independent of the change in CO.PI may have potential applications for MAP optimization based on changes in peripheral tissue perfusion.

Resuscitation incoherence and dynamic circulation-perfusion coupling in circulatory shock

Objective: Poor tissue perfusion/cellular hypoxia may persist despite restoration of the macrocirculation (Macro). This article reviewed the literatures of coherence between hemodynamics and tissue perfusion in circulatory shock. Data sources: We retrieved information from the PubMed database up to January 2018 using various search terms or/and their combinations, including resuscitation, circulatory shock, septic shock, tissue perfusion, hemodynamic coherence, and microcirculation (Micro). Study selection: The data from peer-reviewed journals printed in English on the relationships of tissue perfusion, shock, and resuscitation were included. Results: A binary (coherence/incoherence, coupled/uncoupled, or associated/disassociated) mode is used to describe resuscitation coherence. The phenomenon of resuscitation incoherence (RI) has gained great attention. However, the RI concept requires a more practical, systematic, and comprehensive framework for use in clinical practice. Moreover, we introduce a conceptual framework of RI to evaluate the interrelationship of the Macro, Micro, and cell. The RI is divided into four types (Type 1: Macro-Micro incoherence + impaired cell;Type 2: Macro-Micro incoherence + normal cell;Type 3: Micro-Cell incoherence + normal Micro;and Type 4: both Macro-Micro and Micro-cell incoherence). Furthermore, we propose the concept of dynamic circulation-perfusion coupling to evaluate the relationship of circulation and tissue perfusion during circulatory shock. Conclusions: The concept of RI and dynamic circulation-perfusion coupling should be considered in the management of circulatory shock. Moreover, these concepts require further studies in clinical practice.

Analysis of factors influencing 3-and 6-h compliance with the surviving sepsis campaign guidelines based on medical-quality intensive care unit data from China

To the Editor:In the past decades,there were at least 31.5 million sepsis patients worldwide.Of these patients,5.3 million sepsis patients face death every year.[1]Studies have shown the mortality from sepsis can be reduced by compliance with the surviving sepsis campaign guidelines(C_(ssc)).[2]Compliance with guidelines depends on the execution of the medical team.We assume that the medical quality of the intensive care unit(Q_(ICU))will have an important impact on the C_(ssc).

Lactate induces alternative polarization (M2) of macrophages under lipopolysaccharide stimulation in vitro through G-protein coupled receptor 81

To the Editor:Sepsis is a life-threatening systemic inflammatory response syndrome caused by the host’s maladjusted immune response to infection.Hyperlactatemia is an important manifestation of severe sepsis.Initial hyperlactatemia is associated with increased mortality in sepsis.[1]Hyperlactatemia and immunosuppression often occur simultaneously in the late stage of sepsis.G-proteincoupled receptor 81(GPR81)is a cell-surface G-protein coupled receptor,which is activated by lactate.It has been reported that lactate inhibits the function of macrophages through GPR81,and alleviates liver injury in immune hepatitis.[2]In sepsis,alternative polarization(M2)of macrophages reduces the production of pro-inflammatory factors,weakens the phagocytosis of macrophages,and inhibits the immune response.GPR81 pathway is closely related to M2 polarization of macrophages.Therefore,we designed this experiment to explore the relationship between lactate and M2 of macrophages and further explored the relationship between this effect and the GPR81 pathway in sepsis.

Progress of mechanical power in the intensive care unit

Mechanical power of ventilation,currently defined as the energy delivered from the ventilator to the respiratory system over a period of time,has been recognized as a promising indicator to evaluate ventilator-induced lung injury and predict the prognosis of ventilated critically ill patients.Mechanical power can be accurately measured by the geometric method,while simplified equations allow an easy estimation of mechanical power at the bedside.There may exist a safety threshold of mechanical power above which lung injury is inevitable,and the assessment of mechanical power might be helpful to determine whether the extracorporeal respiratory support is needed in patients with acute respiratory distress syndrome.It should be noted that relatively low mechanical power does not exclude the possibility of lung injury.Lung size and inhomogeneity should also be taken into consideration.Problems regarding the safety limits of mechanical power and contribution of each component to lung injury have not been determined yet.Whether mechanical power-directed lung-protective ventilation strategy could improve clinical outcomes also needs further investigation.Therefore,this review discusses the algorithms,clinical relevance,optimization,and future directions of mechanical power in critically ill patients.

Passive Leg Raising in Intensive Care Medicine

Fluid challenge is a common diagnostic method to help the physician detennine fluid responsiveness, which is an important component of fluid management in critically ill patients）H Raising legs of a patient induces the transfer of a variable amount of blood （approximately 200-300 ml） contained in the venous reservoir from the limb to central venous compartment. According to Franck-Starling curve, this transient increase of preload might lead to an increase in cardiac output （CO） in thture responders resulting from their preload-reserve status. Many clinical studies have validated passive leg raising （PLR）, and the advantage of PLR is attractive in Intensive Care Unit （ICU）. Recently, PER has been suggested as a simple and potential method to predict fluid responsiveness, which is similar to an ＂auto-fluid challenge＂ without a drop of fluid. However, one study revealed poor application of PLR in the real world, We acknowledged that the lack of education on PLR would result in the current practice. On the other hand, the application of PLR might be not simple in clinical practice, and the holy grail of fluid responsiveness still needs to be discovered. The standard of PLR has not been established, and some questions of PLR merit discussion.