Perspectives on peripheral perfusion assessment

Point of View: A Holistic Four-Interface Conceptual Model for Personalizing Shock Resuscitation

The resuscitation of a patient in shock is a highly complex endeavor that should go beyond normalizing mean arterial pressure and protocolized fluid loading. We propose a holistic, four-interface conceptual model of shock that we believe can benefit both clinicians at the bedside and researchers. The four circulatory interfaces whose uncoupling results in shock are as follows: the left ventricle to arterial, the arterial to capillary, the capillary to venular, and finally the right ventricle to pulmonary artery. We review the pathophysiology and clinical consequences behind the uncoupling of these interfaces, as well as how to assess them, and propose a strategy for approaching a patient in shock. Bedside assessment of shock may include these critical interfaces in order to avoid hemodynamic incoherence and to focus on microcirculatory restoration rather than simply mean arterial pressure. The purpose of this model is to serve as a mental model for learners as well as a framework for further resuscitation research that incorporates these concepts.

Capillary refill time and tissue oxygen saturation as factors influencing lower limb ischemia in VA-ECMO: a case-control study

BACKGROUND AND OBJECTIVES

Venous-Arterial Extracorporeal Membrane Oxygenation (VA-ECMO) is a pivotal means for rapid cardiopulmonary support, yet it may result in lower limb ischemia. This study aims to explore the high-risk factors for lower limb ischemia following VA-ECMO.

METHODS

117 patients who received VA-ECMO treatment at Guangxi Zhuang Autonomous Region People's Hospital from June 2022 to December 2023 were divided into lower limb ischemia group and non ischemia group for case-control analysis.

RESULTS

In this case-control study of 117 VA-ECMO patients, 22 (18.80%) experienced lower limb ischemia. Patients with ischemia had significantly lower body surface area (BSA) and lower tissue oxygen saturation (StO2) levels, but higher capillary refill time (CRT) levels compared to those without ischemia (P < 0.05). Spearman correlation analysis showed that StO2 and CRT had strong correlations with ischemia. Binary logistic stepwise regression analysis identified CRT and StO2 as independent risk factors for lower limb ischemia. Specifically, lower StO2 levels were associated with an increased risk of ischemia (OR = 0.615, P < 0.05), while higher CRT levels were also associated with an increased risk (OR = 27.571, P < 0.05). The Receiver Operating Characteristic (ROC) curve shows that the areas of CRT and StO2 are 0.924 (P < 0.001, 95% CI 0.866-0.983) and 0.951 (P = 0.023, 95% CI 0.906-0.997), respectively.

CONCLUSIONS

StO2 reflects real-time tissue perfusion adequacy, whereas CRT serves as a marker of microvascular dysfunction. Lower StO2 levels (indicating impaired oxygenation) and higher CRT levels (suggesting delayed capillary refilling) were independently associated with an increased risk of lower limb ischemia, suggesting that monitoring these parameters may be useful in identifying patients at higher risk for this complication. These findings provide valuable insights for risk stratification and potential intervention strategies in the management of VA-ECMO patients.

Statistical analysis plan for hemodynamic phenotype-based, capillary refill time-targeted resuscitation in early septic shock: the ANDROMEDA-SHOCK-2 randomized clinical trial

BACKGROUND

ANDROMEDA-SHOCK 2 is an international, multicenter, randomized controlled trial comparing hemodynamic phenotype-based, capillary refill time-targeted resuscitation in early septic shock to standard care resuscitation to test the hypothesis that the former is associated with lower morbidity and mortality in terms of hierarchal analysis of outcomes.

OBJECTIVE

To report the statistical plan for the ANDROMEDA--SHOCK 2 randomized clinical trial.

METHODS

We briefly describe the trial design, patients, methods of randomization, interventions, outcomes, and sample size. We portray our planned statistical analysis for the hierarchical primary outcome using the stratified win ratio method, as well as the planned analysis for the secondary and tertiary outcomes. We also describe the subgroup and sensitivity analyses. Finally, we provide details for presenting our results, including mock tables, baseline characteristics, and the effects of treatments on outcomes.

CONCLUSION

According to best trial practices, we report our statistical analysis plan and data management plan prior to locking the database and initiating the analyses. We anticipate that this practice will prevent analysis bias and improve the utility of the study's reported results.

A New Approach to Non-Invasive Microcirculation Monitoring: Quantifying Capillary Refill Time Using Oximetric Pulse Waves

(1) Background: To develop a novel capillary refill time measurement system and evaluate its reliability and reproducibility. (2) Methods: Firstly, the utilization of electromagnetic pressure technology facilitates the automatic compression and instantaneous release of the finger. Secondly, the employment of pressure sensing technology and photoelectric volumetric pulse wave analysis technology enables the dynamic monitoring of blood flow in distal tissues. Thirdly, the subjects were recruited to compare the average measurement time and the number of measurements required for successful measurements. The satisfaction of doctors and patients with the instrument was investigated through the administration of questionnaires. Finally, 71 subjects were recruited and divided into two groups, A and B. Three doctors repeated the measurement of the right index fingers of the subjects. In Group A, the same measuring instrument was used, and the consistency of the measurements was evaluated using the intragroup correlation coefficient. In Group B, one doctor repeated the measurement of each subject three times using the same measuring instrument, and the reproducibility of the CRT was evaluated using the analysis of variance of the repeated measurement data. (3) Results: The development of the capillary refill time meter was successful, with an average measurement time of 18 s and a single measurement. This study found that doctor-patient satisfaction levels were 98.3% and 100%, respectively. The intraclass correlation coefficient was 0.995 in Group A, and the p-value was greater than 0.05 in Group B. (4) Conclusions: The non-invasive monitoring of microcirculation has been rendered both rapid and effective, thus paving the way for the further mechanization and standardization of this process. The CRT, when measured using the capillary refill time meter test machine, demonstrated consistent and reproducible results, both when assessed by different researchers and when evaluated across varying measurement sets.

Correlation of HCT-ALB, SmtO2, CRT and LAC with renal impairment and prognosis in patients with septic shock

Background

This study investigates the correlation between the difference in hematocrit (HCT) and serum albumin (ALB) levels (HCT-ALB), muscle tissue oxygen saturation (SmtO2), capillary refill time (CRT), and blood lactate (Lac) with the severity of renal function damage and prognosis in patients with septic shock.

Methods

Conducted from February 2022 to February 2024, this study included 116 septic shock patients treated at the First Affiliated Hospital of Anhui Medical University. Patients were divided into groups based on whether they developed acute kidney injury: 40 patients were included in the acute kidney injury group, and the remaining 76 were placed in the non-kidney injury group. The levels of HCT-ALB, SmtO2, CRT, and Lac were compared between the groups. Patients were followed up to assess their 28day survival outcomes; 75 surviving patients were placed in the survival group, and 41 deceased patients were in the death group. Differences in clinical data and levels of HCTALB, SmtO2, CRT, and Lac between the two groups were analyzed to explore the relationship of these indicators with patient prognosis.

Results

Levels of HCT-ALB, CRT, and Lac were higher, while SmtO2 was lower in the acute kidney injury group compared to the non-kidney injury group (P<0.05). Similarly, the death group exhibited higher levels of HCTALB, CRT, and Lac and lower SmtO2 levels compared to the survival group (P<0.05). Univariate and multivariate analyses revealed that HCT-ALB, SmtO2, CRT, and Lac significantly impact patient survival outcomes, demonstrating high predictive value for patient mortality with respective AUC values of 0.834, 0.782, 0.903, and 0.918. The combined application of these indicators for predicting patient mortality had an AUC value of 0.985, which is higher than when the indicators were used individually.

Conclusions

HCT-ALB, SmtO2, CRT, and Lac are significantly elevated in patients with acute kidney injury and deceased patients, closely correlating with the severity and prognosis of septic shock. These indicators can serve as essential biomarkers for assessing the condition and prognosis of these patients.

Prospective Evaluation of the Peripheral Perfusion Index in Assessing the Organ Dysfunction and Prognosis of Adult Patients With Sepsis in the ICU

Background: The peripheral perfusion index (PI) reflects microcirculatory blood flow perfusion and indicates the severity and prognosis of sepsis. Method: The cohort comprised 208 patients admitted to the intensive care unit (ICU) with infection, among which 117 had sepsis. Demographics, medication history, ICU variables, and laboratory indexes were collected. Primary endpoints were in-hospital mortality and 28-day mortality. Secondary endpoints included organ function variables (coagulation function, liver function, renal function, and myocardial injury), lactate concentration, mechanical ventilation time, and length of ICU stay. Univariate and multivariate analyses were conducted to assess the associations between the PI and clinical outcomes. Sensitivity analyses were performed to explore the associations between the PI and organ functions in the sepsis and nonsepsis groups. Result: The PI was negatively associated with in-hospital mortality (odds ratio [OR] 0.29, 95% confidence interval [CI] 0.15 to 0.55), but was not associated with 28-day mortality. The PI was negatively associated with the coagulation markers prothrombin time (PT) (β -0.36, 95% CI -0.59 to 0.13) and activated partial thromboplastin time (APTT) (β -1.08, 95% CI -1.86 to 0.31), and the myocardial injury marker cardiac troponin I (cTnI) (β -2085.48, 95% CI -3892.35 to 278.61) in univariate analysis, and with the PT (β -0.36, 95% CI -0.60 to 0.13) in multivariate analysis. The PI was negatively associated with the lactate concentration (β -0.57, 95% CI -0.95 to 0.19), mechanical ventilation time (β -23.11, 95% CI -36.54 to 9.69), and length of ICU stay (β -1.28, 95% CI -2.01 to 0.55). Sensitivity analyses showed that the PI was significantly associated with coagulation markers (PT and APTT) and a myocardial injury marker (cTnI) in patients with sepsis, suggesting that the associations between the PI and organ function were stronger in the sepsis group than the nonsepsis group. Conclusion: The PI provides new insights for assessing the disease severity, short-term prognosis, and organ function damage in ICU patients with sepsis, laying a theoretical foundation for future research.

Quantitative Evaluation of Microcirculatory Alterations in Patients with COVID-19 and Bacterial Septic Shock through Remote Photoplethysmography and Automated Capillary Refill Time Analysis

Background and Objectives: Sepsis, a leading global health challenge, accounts for around 20% of deaths worldwide. The complexity of sepsis, especially the difference between bacterial and viral etiologies, requires an effective assessment of microcirculation during resuscitation. This study aimed to evaluate the impact of infusion therapy on microcirculation in patients with sepsis, focusing on bacterial- and COVID-19-associated sepsis using remote photoplethysmography (rPPG) and the automated capillary refill time (aCRT). Materials and Methods: This single-center prospective study was conducted in the ICU of Pauls Stradins Clinical University Hospital, including 20 patients with sepsis/septic shock. The patients were selected based on hemodynamic instability and divided into COVID-19 and Bacterial Septic Shock groups. Fluid responsiveness was assessed using the Passive Leg Raising Test (PLRT). Systemic hemodynamics and microcirculation were monitored through MAP CRT, rPPG, and serum lactate levels. Statistical analyses compared responses within and between the groups across different stages of the protocol. Results: The Bacterial group exhibited higher initial serum lactate levels and more pronounced microcirculatory dysfunction than the COVID-19 group. rPPG was more sensitive in detecting perfusion changes, showing significant differences between the groups. The automated CRT demonstrated greater sensitivity compared to the manual CRT, revealing significant differences during PLRT stages between bacterial- and COVID-19-associated sepsis. Both groups had a transient hemodynamic response to PLRT, with subsequent stabilization upon fluid infusion. Conclusions: When managing patients with sepsis in intensive care, monitoring microcirculation is of paramount importance in infusion therapy. Our study highlights the potential of rPPG and aCRT as tools for this purpose. These techniques can be used in conjunction with routine parameters, such as lactate levels and systemic hemodynamic parameters, to provide a comprehensive assessment of a patient's condition.

Early peripheral perfusion monitoring in septic shock

Septic shock is a frequent critical clinical condition and a leading cause of death in critically ill individuals. However, it is challenging to identify affected patients early. In this article, we discuss new perspectives on the methods and uses of peripheral perfusion monitoring, considering the concept of a dysregulated response. Physical examination, and visual and ultrasonographic techniques are used to measure peripheral microcirculatory blood flow to reflect tissue perfusion. Compared with other monitoring techniques, peripheral perfusion monitoring has the benefits of low invasiveness and good repeatability, and allows for quick therapeutic judgments, which have significant practical relevance. Peripheral perfusion monitoring is an effective tool to detect early signs of septic shock, autonomic dysfunction, and organ damage. This method can also be used to evaluate treatment effectiveness, direct fluid resuscitation and the use of vasoactive medications, and monitor vascular reactivity, microcirculatory disorders, and endothelial cell damage. Recent introductions of novel peripheral perfusion monitoring methods, new knowledge of peripheral perfusion kinetics, and multimodal peripheral perfusion evaluation methods have occurred. To investigate new knowledge and therapeutic implications, we examined the methodological attributes and mechanisms of peripheral perfusion monitoring, in this study.

Microvascular Autoregulation in Skeletal Muscle Using Near-Infrared Spectroscopy and Derivation of Optimal Mean Arterial Pressure in the ICU: Pilot Study and Comparison With Cerebral Near-Infrared Spectroscopy

IMPORTANCE

Microvascular autoregulation (MA) maintains adequate tissue perfusion over a range of arterial blood pressure (ABP) and is frequently impaired in critical illness. MA has been studied in the brain to derive personalized hemodynamic targets after brain injury. The ability to measure MA in other organs is not known, which may inform individualized management during shock.

OBJECTIVES

This study determines the feasibility of measuring MA in skeletal muscle using near-infrared spectroscopy (NIRS) as a marker of tissue perfusion, the derivation of optimal mean arterial pressure (MAPopt), and comparison with indices from the brain.

DESIGN

Prospective observational study.

SETTING

Medical and surgical ICU in a tertiary academic hospital.

PARTICIPANTS

Adult critically ill patients requiring vasoactive support on the first day of ICU admission.

MAIN OUTCOMES AND MEASURES

Fifteen critically ill patients were enrolled. NIRS was applied simultaneously to skeletal muscle (brachioradialis) and brain (frontal cortex) while ABP was measured continuously via invasive catheter. MA correlation indices were calculated between ABP and NIRS from skeletal muscle total hemoglobin (MVx), muscle tissue saturation index (MOx), brain total hemoglobin (THx), and brain tissue saturation index (COx). Curve fitting algorithms derive the MAP with the lowest correlation index value, which is the MAPopt.

RESULTS

MAPopt values were successfully calculated for each correlation index for all patients and were frequently (77%) above 65 mm Hg. For all correlation indices, median time was substantially above impaired MA threshold (24.5-34.9%) and below target MAPopt (9.0-78.6%). Muscle and brain MAPopt show moderate correlation (MVx-THx r = 0.76, p < 0.001; MOx-COx r = 0.69, p = 0.005), with a median difference of -1.27 mm Hg (-9.85 to -0.18 mm Hg) and 0.05 mm Hg (-7.05 to 2.68 mm Hg).

CONCLUSIONS AND RELEVANCE

This study demonstrates, for the first time, the feasibility of calculating MA indices and MAPopt in skeletal muscle using NIRS. Future studies should explore the association between impaired skeletal muscle MA, ICU outcomes, and organ-specific differences in MA and MAPopt thresholds.

Association between peripheral perfusion index and postoperative acute kidney injury in major noncardiac surgery patients receiving continuous vasopressors: a post hoc exploratory analysis of the VEGA-1 trial

BACKGROUND

The peripheral perfusion index is the ratio of pulsatile to nonpulsatile static blood flow obtained by photoplethysmography and reflects peripheral tissue perfusion. We investigated the association between intraoperative perfusion index and postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions.

METHODS

In this exploratory post hoc analysis of a pragmatic, cluster-randomised, multicentre trial, we obtained areas and cumulative times under various thresholds of perfusion index and investigated their association with acute kidney injury in multivariable logistic regression analyses. In secondary analyses, we investigated the association of time-weighted average perfusion index with acute kidney injury. The 30-day mortality was a secondary outcome.

RESULTS

Of 2534 cases included, 8.9% developed postoperative acute kidney injury. Areas and cumulative times under a perfusion index of 3% and 2% were associated with an increased risk of acute kidney injury; the strongest association was observed for area under a perfusion index of 1% (adjusted odds ratio [aOR] 1.32, 95% confidence interval [CI] 1.00-1.74, P=0.050, per 100%∗min increase). Additionally, time-weighted average perfusion index was associated with acute kidney injury (aOR 0.82, 95% CI 0.74-0.91, P<0.001) and 30-day mortality (aOR 0.68, 95% CI 0.49-0.95, P=0.024).

CONCLUSIONS

Larger areas and longer cumulative times under thresholds of perfusion index and lower time-weighted average perfusion index were associated with postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions.

CLINICAL TRIAL REGISTRATION

NCT04789330.

Capillary refill time response to a fluid challenge or a vasopressor test: an observational, proof-of-concept study

BACKGROUND

Several studies have validated capillary refill time (CRT) as a marker of tissue hypoperfusion, and recent guidelines recommend CRT monitoring during septic shock resuscitation. Therefore, it is relevant to further explore its kinetics of response to short-term hemodynamic interventions with fluids or vasopressors. A couple of previous studies explored the impact of a fluid bolus on CRT, but little is known about the impact of norepinephrine on CRT when aiming at a higher mean arterial pressure (MAP) target in septic shock. We designed this observational study to further evaluate the effect of a fluid challenge (FC) and a vasopressor test (VPT) on CRT in septic shock patients with abnormal CRT after initial resuscitation. Our purpose was to determine the effects of a FC in fluid-responsive patients, and of a VPT aimed at a higher MAP target in chronically hypertensive fluid-unresponsive patients on the direction and magnitude of CRT response.

METHODS

Thirty-four septic shock patients were included. Fluid responsiveness was assessed at baseline, and a FC (500 ml/30 mins) was administered in 9 fluid-responsive patients. A VPT was performed in 25 patients by increasing norepinephrine dose to reach a MAP to 80-85 mmHg for 30 min. Patients shared a multimodal perfusion and hemodynamic monitoring protocol with assessments at at least two time-points (baseline, and at the end of interventions).

RESULTS

CRT decreased significantly with both tests (from 5 [3.5-7.6] to 4 [2.4-5.1] sec, p = 0.008 after the FC; and from 4.0 [3.3-5.6] to 3 [2.6 -5] sec, p = 0.03 after the VPT. A CRT-response was observed in 7/9 patients after the FC, and in 14/25 pts after the VPT, but CRT deteriorated in 4 patients on this latter group, all of them receiving a concomitant low-dose vasopressin.

CONCLUSIONS

Our findings support that fluid boluses may improve CRT or produce neutral effects in fluid-responsive septic shock patients with persistent hypoperfusion. Conversely, raising NE doses to target a higher MAP in previously hypertensive patients elicits a more heterogeneous response, improving CRT in the majority, but deteriorating skin perfusion in some patients, a fact that deserves further research.

Risk factors for poor performance in finger cuff non-invasive monitoring of arterial pressure: A prospective multicenter study

BACKGROUND

Compared to the invasive technique, non-invasive monitoring of arterial pressure favors easier and faster implementation while potentially sacrificing some reliability. This may be particularly true for the Clearsight™ system (Edwards Lifesciences), which enables continuous monitoring. We evaluated the risk factors for its poor performance.

METHODS

Patients with an arterial catheter and stable mean arterial pressure (MAP) over a 5-min period were included. Six pairs of invasive and Clearsight measurements of MAP were collected and the bias between the two techniques was calculated. Poor performance of the Clearsight™ system was defined as either a failure to measure and display MAP or displaying an erroneous MAP (individual bias > 5 mmHg). Fingertip perfusion was assessed using the plethysmographic perfusion index (PI) and the capillary refill time (CRT).

RESULTS

Among 152 ICU patients (MAP of 81 ± 14 mmHg, norepinephrine in 78 [51%]), 78 (51%) experienced a poor performance of the Clearsight™ system: failure to display MAP in 19 (13%) patients, and erroneous value displayed in 59 (44%). In multivariate analysis, PI ≤ 0.85% (adjusted odds ratio [aOR] = 2.94 [95% confidence interval (95%CI):1.34;6.45]), CRT > 4 s (aOR = 5.28 [95%CI 1.39;20.05]), and the presence of hand edema (aOR = 2.06 [95%CI 1.01;4.21]) were associated with a higher likelihood of poor performance. Cardiac arrhythmia (aOR = 1.39 [95%CI 0.64;3.02]) and other tested variables were not associated with poor performance.

CONCLUSIONS

Half of the included patients exhibited poor Clearsight™ system performance. Our results caution against using finger cuff arterial pressure monitoring in patients with low PI (≤0.85%), protracted CRT (>4 s), or hand edema.

REGISTRATION

ClinicalTrials.gov, NCT04269382, Dr. G. Muller, February 13, 2020. https://classic.

CLINICALTRIALS

gov/ct2/show/NCT04269382.

Effect on capillary refill time of volume expansion and increase of the norepinephrine dose in patients with septic shock

BACKGROUND

Capillary refill time (CRT) has been suggested as a variable to follow during the course of septic shock. We systematically investigated the effects on CRT of volume expansion and norepinephrine.

METHODS

In 69 septic shock patients, we recorded mean arterial pressure (MAP), cardiac index (CI), and 5 consecutive CRT measurements (video method, standardized pressure applied on the fingertip) before and after a 500-mL saline infusion in 33 patients and before and after an increase of the norepinephrine dose in 36 different patients. Fluid responders were defined by an increase in CI ≥ 15%, and norepinephrine responders by an increase in MAP ≥ 15%.

RESULTS

The least significant change of CRT was 23%, so that changes in CRT were considered significant if larger than 23%. With volume expansion, CRT remained unchanged on average in patients with baseline CRT < 3 s (n = 7) and in all but one patient with baseline CRT ≥ 3 s in whom fluid increased CI < 15% (n = 13 "fluid non-responders"). In fluid responders with baseline CRT ≥ 3 s (n = 13), CRT decreased in 8 patients and remained unchanged in the others, exhibiting a dissociation between CI and CRT responses. The proportion of patients included > 24 h after starting norepinephrine was higher in patients with such a dissociation than in the other ones (60% vs. 0%, respectively). Norepinephrine did not change CRT significantly (except in one patient) if baseline CRT was ≥ 3 s and the increase in MAP < 15% (n = 6). In norepinephrine responders with prolonged baseline CRT (n = 11), it increased in 4 patients and remained unchanged in the other ones, which exhibited a dissociation between MAP and CRT responses.

CONCLUSIONS

In septic shock patients with prolonged CRT, CRT very rarely improves with treatment when volume expansion increases cardiac output < 15% and increasing norepinephrine increases MAP < 15%. When the effects of fluid infusion on cardiac output and of norepinephrine on MAP are significant, the response of CRT is variable, as it decreases in some patients and remains stable in others which exhibit a dissociation between changes in macrohemodynamic variables and in CRT. In this regard, CRT behaves as a marker of microcirculation.

TRIAL REGISTRATION

ClinicalTrial.gov (NCT04870892). Registered January15, 2021. Ethics committee approval CE SRLF 21-25.