Resuscitation incoherence and dynamic circulation-perfusion coupling in circulatory shock

Resuscitating the macro- vs. microcirculation in septic shock

PURPOSE OF REVIEW

This review summarizes current literature about the relationships between macro and microcirculation and their practical clinical implications in children with septic shock.

RECENT FINDINGS

Current evidence from experimental and clinical observational studies in children and adults with septic shock reveals that the response to treatment and resuscitation is widely variable. Furthermore, there is a loss of hemodynamic coherence, as resuscitation-induced improvement in macrocirculation (systemic hemodynamic parameters) does not necessarily result in a parallel improvement in the microcirculation. Therefore, patient-tailored monitoring is essential in order to adjust treatment requirements during resuscitation in septic shock. Optimal monitoring must integrate macrocirculation (heart rate, blood pressure, cardiac output, and ultrasound images), microcirculation (videomicroscopy parameters and capillary refill time) and cellular metabolism (lactic acid, central venous blood oxygen saturation, and difference of central venous to arterial carbon dioxide partial pressure).

SUMMARY

There is a dire need for high-quality studies to assess the relationships between macrocirculation, microcirculation and tissue metabolism in children with septic shock. The development of reliable and readily available microcirculation and tissue perfusion biomarkers (other than lactic acid) is also necessary to improve monitoring and treatment adjustment in such patients.

Sublingual microcirculation: comparison between the 415 nm blue light and 520 nm green light of sidestream dark field videomicroscopes

Green light with a wavelength of 520 nm is commonly used in sidestream dark field (SDF) video microscopes for sublingual microcirculation assessment in clinical practice. However, blue light could obtain a clearer microcirculatory image due to a higher light absorption coefficient of hemoglobin. The aim of this study was to compare the sublingual microcirculatory image quality acquisition and related microcirculatory parameters between 520 nm green light and 415 nm blue light probes in the SDF device named MicroSee V100. Sublingual microcirculation films from twenty-one healthy volunteers were prospectively collected by blue light and green light probes, and only one video of each wavelength was recorded and analyzed in each volunteer. Moreover, 200 sublingual microcirculation films (100 by blue light probe and 100 by green light probe) of ICU patients were retrospectively scored for microcirculation image quality. Compared to green light, an increase in the perfused vessel density (paired t test, increased by 4.6 ± 4.7 mm/mm², P < 0.0001) and total vessel density (paired t test, increased by 5.1 ± 4.6 mm/mm², P < 0.0001) was observed by blue light in the healthy volunteers. The blue light probe had a significantly lower rate of unacceptable films than the green light probe in the 200 films of ICU patients (10/100 vs. 39/100, P < 0.0001). Blue light provides a higher microcirculatory vessel density and image quality than the existing SDF probe using green light.

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.

Point-of-care microcirculation evaluated with sidestream dark field technology: agreement and comparison between sublingual and sublabial mucosa

To investigate whether sublabial mucosa is more suitable for evaluation of microcirculation than commonly used sublingual mucosa in ICU patients, we enrolled 57 adults (47 critically ill patients and 10 volunteers) at convenience from Oct 2018 to Jan 2019. Videomicroscopy images at both sublingual mucosa and sublabial mucosa were acquired at the same time in each enrollee. Qualified images were recorded for later analysis. Four video clips of the same site were comprehensively evaluated to yield one Point Of carE Microcirculation (POEM) score by blinded investigator; POEM scores at both sites were statistically analyzed for correlation and agreement. Procedure time needed to acquire qualified images was also compared. POEM scores between the two sites showed no significant difference and a statistically significant correlation (Spearman correlation coefficient 0.716, P < 0.001). The intra-class correlation coefficient was 0.866 (95% C.I. 0.774, 0.921), suggesting good to excellent consistency and agreement between the POEM scores at the two sites. The procedure time needed to acquire 4 clips of qualified images at sublingual and sublabial sites were 10.5±3.9 minutes and 7.1±3.3 minutes respectively, P < 0.001. This study indicates that point of care evaluation of microcirculation by POEM score shows good to excellent agreement between sublingual mucosa and sublabial mucosa. It is easier to acquire qualified videomicroscopy images at sublabial mucosa than at sublingual mucosa. Therefore, sublabial mucosa might be more suitable for bedside evaluation of microcirculation with handheld SDF device in ICU.