The response of the microcirculation to mechanical support of the heart in critical illness

[Relationship between cardiac output, heart rate and microcirculation in patients with multiorgan dysfunction syndrome]

BACKGROUND

Multiple organ dysfunction syndrome (MODS) is one of the main causes of death in intensive care units. There is evidence that microcirculation in sepsis and coronary shock is regulated separately from hemodynamics. This study investigates the relationship between heart rate (HR), cardiac output (CO) and microcirculation in patients with MODS.

METHODS

This is a partial analysis of the "MODIFY study" (Reducing Elevated Heart Rate in Patients With Multiple Organ Dysfunction Syndrome [MODS] by Ivabradine). During the period 05/2010-09/2011, the microcirculation of 46 patients with septic and coronary MODS was measured using the sidestream dark field technique on the day of inclusion and 96 h later. Patients were randomized into a control and ivabradine treatment group.

RESULTS

Overall, there is a relevant improvement in microcirculation over time small perfused vessels, SPV [%] on day 0, d0:56.5 ± 34.2/d4:73.2 ± 22.1 (p = 0.03); perfused vessel density, PVDsmall [1/mm2] d0:7.5 ± 5.0/d4:9.8 ± 3.4 (p = 0.04); proportion of perfused vessels, PPVsmall [%] d0:51.6 ± 31.6/d4:66.7 ± 21.8 (p = 0.04); microcirculatory flow index, MFI d0:1.7 ± 1.0/d4:2.2 ± 0.7 (p = 0.05). Administration of ivabradine shows no effect. In patients with coronary MODS, there is a relevant correlation between microcirculatory parameters and cardiac output (SPV [%]: r = 0.98, p = 0.004). Patients with coronary MODS show better microcirculation values at high heart rates (> 100 bpm), while patients with septic MODS show an opposite relationship.

CONCLUSION

The results indicate that in critically ill patients, depending on the genesis of the MODS, there are different relationships between HF or CO values, on the one hand, and the parameters of the microcirculation, on the other.

Evaluation of Team-Based Learning to Increase Nurses' Knowledge of the Ventricular Assist Device

Ventricular assist devices (VAD) are used to extend life expectancy for patients with advanced heart failure. Approximately 102 hospitals nationwide have a VAD program, but the majority implant only a small number of devices each year. This low-volume and high-acuity patient population can create concerns for maintaining nursing knowledge skill levels. Nursing staff from a step-down telemetry floor in a large urban hospital completed an Individual Readiness Assessment Test to assess their knowledge and accuracy in the care of mechanical circulatory support patients using the Immediate Feedback Assessment Technique. The nurses were then assigned to small groups and worked as a team to complete the same test known as the Group Readiness Assessment Test. Study results suggest that team-based learning was effective in increasing knowledge of mechanical circulatory support. [J Contin Educ Nurs. 2021;52(1):13-20.].

Feasibility study of incident dark-field video microscope for measuring microcirculatory variables in the mouse dorsal skinfold chamber model

Background

Despite the importance of microcirculation in organ function, monitoring microcirculation is not a routine practice. With developments in microscopic technology, incident dark field (IDF) microscopy (Cytocam) has allowed visualization of the microcirculation. Dorsal skinfold chamber (DSC) mouse model has been used to investigate microcirculation physiology. By employing Cytocam-IDF imaging with DSC model to assess microcirculatory alteration in lipopolysaccharide (LPS)-induced endotoxemia, we attempted to validate availability of Cytocam-IDF imaging of microcirculation.

Methods

DSC was implanted in eight BALB/c mice for each group; control and sepsis. Both groups were given 72 hours to recover from surgery. The sepsis group had an additional 24-hour period of recovery post-LPS injection (4 mg/kg). Subsequently, a video of the microcirculation was recorded using Cytocam. Data on microcirculatory variables were obtained. Electron microscopy was implemented using lanthanum fixation to detect endothelial glycocalyx degradation.

Results

The microcirculatory flow index was significantly lower (control, 2.8±0.3; sepsis, 2.1±0.8; P=0.033) and heterogeneity index was considerably higher (control, 0.10±0.15; sepsis, 0.53±0.48; P=0.044) in the sepsis group than in the control group. Electron microscopy revealed glycocalyx demolishment in the sepsis group.

Conclusions

Cytocam showed reliable ability for observing changes in the microcirculation under septic conditions in the DSC model. The convenience and good imaging quality and the automatic analysis software available for Cytocam-IDF imaging, along with the ability to perform real-time in vivo experiments in the DSC model, are expected to be helpful in future microcirculation investigations.

Assessment of microcirculation in cardiogenic shock

PURPOSE OF REVIEW

Adequate tissue perfusion is of utmost importance to avoid organ failure in patients with cardiogenic shock. Within the recent years, the microcirculation, defined as the perfusion of the smallest vessels, has been identified to play a crucial role. Microcirculatory changes may include capillary flow disturbances as well as changes in the density of perfused vessels. Due to the availability of new technologies to assess the microcirculation, interesting new data came up and it is the purpose of this review to summarize recent studies in the field.

RECENT FINDINGS

Nowadays, an increasing number of studies confirm parameters of the microcirculation, derived by intravital microscopy, to represent strong outcome predictors in cardiogenic shock. In addition, microcirculation as read-out parameter in innovative clinical studies has meanwhile been accepted as serious endpoint. Treatment strategies such as mechanical assist devices, blood pressure regulating agents or fluids use tissue perfusion and microcirculatory network density as targets in addition to clinical perfusion evaluation and decreasing serum lactate levels.

SUMMARY

The parameter most frequently used to detect tissue malperfusion is serum lactate. Novel, noninvasive methods to quantify microvascular perfusion have the potential to guide treatment in terms of optimizing organ perfusion and oxygenation probably paving the way for an individualized therapy.

A novel mortality risk score predicting intensive care mortality in cardiogenic shock patients treated with veno-arterial extracorporeal membrane oxygenation

PURPOSE

Mortality after veno-arterial extracorporeal membrane oxygenation (VA-ECMO) implantation remains a major problem in patients with cardiogenic shock. Our objective was to assess the utility of the SOFA score in combination with markers of right ventricular (RV) dysfunction in predicting mortality in the ICU.

MATERIALS AND METHODS

Data were retrospectively obtained from all adult patients (n=103) who were treated with VA-ECMO between November 2004 and January 2016. The primary outcome of this study was ICU mortality after VA-ECMO implantation. Using the clinical, demographic and echocardiographic data, we developed a novel mortality risk score, the SOFA-RV score, which combine RV-function to the SOFA score at the time of VA-ECMO implantation.

RESULTS

Out of 103 patients, 37 (36%) died in the ICU. The median duration of VA-ECMO support was 7 days [IQR 4-11], mean age 49 ± 16 years, and 54% were male. SOFA-RV score has an AUC of 0.70, and was significantly better than SOFA alone (AUC of 0.57) in predicting ICU mortality. In addition, SAVE and MELD scores were not able to predict ICU mortality.

CONCLUSION

Adding RV-function to the existing SOFA score improves significantly the prediction of ICU mortality in patients on VA-ECMO. Dedicated evaluation of RV function in patients with VA-ECMO is therefore recommended.

Prognostic implications of microcirculatory perfusion versus macrocirculatory perfusion in cardiogenic shock: a CULPRIT-SHOCK substudy

BACKGROUND

After early revascularisation, restoration of macrocirculatory perfusion parameters is the primary objective in the management of cardiogenic shock complicated acute myocardial infarction. Nevertheless, vital organ perfusion may be compromised at the systemic microcirculatory level, even in patients with preserved macrohaemodynamics. Microvascular perfusion was shown to have independent prognostic value for early mortality. The present study aims to compare the prognostic value of microcirculatory versus macrocirculatory perfusion parameters.

METHODS

This substudy of the culprit lesion-only percutaneous coronary intervention versus multivessel percutaneous coronary intervention in cardiogenic shock (CULPRIT-SHOCK) trial examined the sublingual capillary network using videomicroscopy post-percutaneous coronary intervention to determine the proportion of perfused capillaries (<20 µm) and perfused capillary density. Thirty-day follow-up was performed to obtain the occurrence of a combined clinical endpoint of all-cause death and renal replacement therapy.

RESULTS

Videomicroscopy measurements were performed in 66 patients. There was a significant adjusted association between microcirculatory perfusion parameters and the combined clinical endpoint (proportion of perfused capillaries: P=0.020; perfused capillary density: P=0.035), whereas there was no significant adjusted association between macrocirculatory perfusion parameters and the combined clinical endpoint (systolic blood pressure: P=0.205). Normotensive patients with compromised microcirculatory perfusion parameters had a higher risk of the combined clinical endpoint than normotensive patients with preserved microcirculatory perfusion parameters (proportion of perfused capillaries: Breslow P=0.014; perfused capillary density: Breslow P=0.076).

CONCLUSIONS

There is a significant and independent association between microcirculatory perfusion parameters perfused capillary density and proportion of perfused capillaries and the combined clinical endpoint of all-cause death and renal replacement therapy at 30 days follow-up. In patients with loss of haemodynamic coherence between microcirculatory and macrocirculatory perfusion parameters, microcirculatory perfusion parameters confer dominant prognostic value.

Functional evaluation of sublingual microcirculation indicates successful weaning from VA-ECMO in cardiogenic shock

Background

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly adopted for the treatment of cardiogenic shock (CS). However, a marker of successful weaning remains largely unknown. Our hypothesis was that successful weaning is associated with sustained microcirculatory function during ECMO flow reduction. Therefore, we sought to test the usefulness of microcirculatory imaging in the same sublingual spot, using incident dark field (IDF) imaging in assessing successful weaning from VA-ECMO and compare IDF imaging with echocardiographic parameters.

Methods

Weaning was performed by decreasing the VA-ECMO flow to 50% (F₅₀) from the baseline. The endpoint of the study was successful VA-ECMO explantation within 48 hours after weaning. The response of sublingual microcirculation to a weaning attempt (WA) was evaluated. Microcirculation was measured in one sublingual area (single spot (ss)) using CytoCam IDF imaging during WA. Total vessel density (TVDss) and perfused vessel density (PVDss) of the sublingual area were evaluated before and during 50% flow reduction (TVDss_F50, PVDss_F50) after a WA and compared to conventional echocardiographic parameters as indicators of the success or failure of the WA.

Results

Patients (n = 13) aged 49 ± 18 years, who received VA-ECMO for the treatment of refractory CS due to pulmonary embolism (n = 5), post cardiotomy (n = 3), acute coronary syndrome (n = 2), myocarditis (n = 2) and drug intoxication (n = 1), were included. TVDss_F50 (21.9 vs 12.9 mm/mm², p = 0.001), PVDss_F50 (19.7 vs 12.4 mm/mm², p = 0.01) and aortic velocity–time integral (VTI) at 50% flow reduction (VTI_F50) were higher in patients successfully weaned vs not successfully weaned. The area under the curve (AUC) was 0.99 vs 0.93 vs 0.85 for TVDss_F50 (small vessels) >12.2 mm/mm², left ventricular ejection fraction (LVEF) >15% and aortic VTI >11 cm. Likewise, the AUC was 0.91 vs 0.93 vs 0.85 for the PVDss_F50 (all vessels) >14.8 mm/mm², LVEF >15% and aortic VTI >11 cm.

Conclusion

This study identified sublingual microcirculation as a novel potential marker for identifying successful weaning from VA-ECMO. Sustained values of TVDss_F50 and PVDss_F50 were found to be specific and sensitive indicators of successful weaning from VA-ECMO as compared to echocardiographic parameters.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1855-2) contains supplementary material, which is available to authorized users.