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.

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.