When to stop septic shock resuscitation: clues from a dynamic perfusion monitoring

Monitoring peripheral perfusion and microcirculation

PURPOSE OF REVIEW

Microcirculatory alterations play a major role in the pathogenesis of shock. Monitoring tissue perfusion might be a relevant goal for shock resuscitation. The goal of this review was to revise the evidence supporting the monitoring of peripheral perfusion and microcirculation as goals of resuscitation. For this purpose, we mainly focused on skin perfusion and sublingual microcirculation.

RECENT FINDINGS

Although there are controversies about the reproducibility of capillary refill time in monitoring peripheral perfusion, it is a sound physiological variable and suitable for the ICU settings. In addition, observational studies showed its strong ability to predict outcome. Moreover, a preliminary study suggested that it might be a valuable goal for resuscitation. These results should be confirmed by the ongoing ANDROMEDA-SHOCK randomized controlled trial. On the other hand, the monitoring of sublingual microcirculation might also provide relevant physiological and prognostic information. On the contrary, methodological drawbacks mainly related to video assessment hamper its clinical implementation at the present time.

SUMMARY

Measurements of peripheral perfusion might be useful as goal of resuscitation. The results of the ANDROMEDA-SHOCK will clarify the role of skin perfusion as a guide for the treatment of shock. In contrast, the assessment of sublingual microcirculation mainly remains as a research tool.

Assessment of Regional Perfusion and Organ Function: Less and Non-invasive Techniques

Sufficient organ perfusion essentially depends on preserved macro- and micro-circulation. The last two decades brought substantial progress in the development of less and non-invasive monitoring of macro-hemodynamics. However, several recent studies suggest a frequent incoherence of macro- and micro-circulation. Therefore, this review reports on interactions of macro- and micro-circulation as well as on specific regional and micro-circulation. Regarding global micro-circulation the last two decades brought advances in a more systematic approach of clinical examination including capillary refill time, a graded assessment of mottling of the skin and accurate measurement of body surface temperatures. As a kind of link between macro- and microcirculation, a number of biochemical markers can easily be obtained. Among those are central-venous oxygen saturation (S_cvO₂), plasma lactate and the difference between central-venous and arterial CO₂ (cv-a-pCO₂-gap). These inexpensive markers have become part of clinical routine and guideline recommendations. While their potential to replace parameters of macro-circulation such as cardiac output (CO) is limited, they facilitate the interpretation of the adequacy of CO and other macro-circulatory markers. Furthermore, they give additional hints on micro-circulatory impairment. In addition, a number of more sophisticated technical approaches to quantify and visualize micro-circulation including video-microscopy, laser flowmetry, near-infrared spectroscopy (NIRS), and partial oxygen pressure measurement have been introduced within the last 20 years. These technologies have been extensively used for scientific purposes. Moreover, they have been successfully used for educational purposes and to visualize micro-circulatory disturbances during sepsis and other causes of shock. Despite several studies demonstrating the association of these techniques and parameters with outcome, their practical application still is limited. However, future improvements in automated and “online” diagnosis will help to make these technologies more applicable in clinical routine. This approach is promising with regard to several studies which demonstrated the potential to guide therapy in different types of shock. Finally several organs have specific patterns of circulation related to their special anatomy (liver) or their auto-regulatory capacities (brain, kidney). Therefore, this review also discusses specific issues of monitoring liver, brain, and kidney circulation and function.

Narrative review: clinical assessment of peripheral tissue perfusion in septic shock

Sepsis is one of the main reasons for intensive care unit admission and is responsible for high morbidity and mortality. The usual hemodynamic targets for resuscitation of patients with septic shock use macro-hemodynamic parameters (hearth rate, mean arterial pressure, central venous pressure). However, persistent alterations of microcirculatory blood flow despite restoration of macro-hemodynamic parameters can lead to organ failure. This dissociation between macro- and microcirculatory compartments brings a need to assess end organs tissue perfusion in patients with septic shock. Traditional markers of tissue perfusion may not be readily available (lactate) or may take time to assess (urine output). The skin, an easily accessible organ, allows clinicians to quickly evaluate the peripheral tissue perfusion with noninvasive bedside parameters such as the skin temperatures gradient, the capillary refill time, the extent of mottling and the peripheral perfusion index.

Haemodynamic assessment and support in sepsis and septic shock in resource-limited settings

Background

Recommendations for haemodynamic assessment and support in sepsis and septic shock in resource-limited settings are largely lacking.

Methods

A task force of six international experts in critical care medicine, all of them members of the Global Intensive Care Working Group of the European Society of Intensive Care Medicine and with extensive bedside experience in resource-limited intensive care units, reviewed the literature and provided recommendations regarding haemodynamic assessment and support, keeping aspects of efficacy and effectiveness, availability and feasibility and affordability and safety in mind.

Results

We suggest using capillary refill time, skin mottling scores and skin temperature gradients; suggest a passive leg raise test to guide fluid resuscitation; recommend crystalloid solutions as the initial fluid of choice; recommend initial fluid resuscitation with 30 ml/kg in the first 3 h, but with extreme caution in settings where there is a lack of mechanical ventilation; recommend against an early start of vasopressors; suggest starting a vasopressor in patients with persistent hypotension after initial fluid resuscitation with at least 30 ml/kg, but earlier when there is lack of vasopressors and mechanical ventilation; recommend using norepinephrine (noradrenaline) as a first-line vasopressor; suggest starting an inotrope with persistence of plasma lactate >2 mmol/L or persistence of skin mottling or prolonged capillary refill time when plasma lactate cannot be measured, and only after initial fluid resuscitation; suggest the use of dobutamine as a first-line inotrope; recommend administering vasopressors through a central venous line and suggest administering vasopressors and inotropes via a central venous line using a syringe or infusion pump when available.

Conclusion

Recommendations for haemodynamic assessment and support in sepsis and septic shock in resource-limited settings have been developed by a task force of six international experts in critical care medicine with extensive practical experience in resource-limited settings.

Effect of a Resuscitation Strategy Targeting Peripheral Perfusion Status vs Serum Lactate Levels on 28-Day Mortality Among Patients With Septic Shock: The ANDROMEDA-SHOCK Randomized Clinical Trial

IMPORTANCE

Abnormal peripheral perfusion after septic shock resuscitation has been associated with organ dysfunction and mortality. The potential role of the clinical assessment of peripheral perfusion as a target during resuscitation in early septic shock has not been established.

OBJECTIVE

To determine if a peripheral perfusion-targeted resuscitation during early septic shock in adults is more effective than a lactate level-targeted resuscitation for reducing mortality.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, randomized trial conducted at 28 intensive care units in 5 countries. Four-hundred twenty-four patients with septic shock were included between March 2017 and March 2018. The last date of follow-up was June 12, 2018.

INTERVENTIONS

Patients were randomized to a step-by-step resuscitation protocol aimed at either normalizing capillary refill time (n = 212) or normalizing or decreasing lactate levels at rates greater than 20% per 2 hours (n = 212), during an 8-hour intervention period.

MAIN OUTCOMES AND MEASURES

The primary outcome was all-cause mortality at 28 days. Secondary outcomes were organ dysfunction at 72 hours after randomization, as assessed by Sequential Organ Failure Assessment (SOFA) score (range, 0 [best] to 24 [worst]); death within 90 days; mechanical ventilation-, renal replacement therapy-, and vasopressor-free days within 28 days; intensive care unit and hospital length of stay.

RESULTS

Among 424 patients randomized (mean age, 63 years; 226 [53%] women), 416 (98%) completed the trial. By day 28, 74 patients (34.9%) in the peripheral perfusion group and 92 patients (43.4%) in the lactate group had died (hazard ratio, 0.75 [95% CI, 0.55 to 1.02]; P = .06; risk difference, -8.5% [95% CI, -18.2% to 1.2%]). Peripheral perfusion-targeted resuscitation was associated with less organ dysfunction at 72 hours (mean SOFA score, 5.6 [SD, 4.3] vs 6.6 [SD, 4.7]; mean difference, -1.00 [95% CI, -1.97 to -0.02]; P = .045). There were no significant differences in the other 6 secondary outcomes. No protocol-related serious adverse reactions were confirmed.

CONCLUSIONS AND RELEVANCE

Among patients with septic shock, a resuscitation strategy targeting normalization of capillary refill time, compared with a strategy targeting serum lactate levels, did not reduce all-cause 28-day mortality.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03078712.

Prognostic relevance of serum lactate kinetics in critically ill patients

PURPOSE

Changes of lactate concentration over time were reported to be associated with survival in septic patients. We aimed to evaluate delta-lactate (ΔLac) 24 h after admission (Δ24Lac) to an intensive care unit (ICU) in critically ill patients for short- and long-term prognostic relevance.

METHODS

In total, 26,285 lactate measurements of 2191 patients admitted to a German ICU were analyzed. Inclusion criterion was a lactate concentration at admission above 2.0 mmol/L. Maximum lactate concentrations of day 1 and day 2 were used to calculate Δ24Lac. Follow-up of patients was performed retrospectively. Association of Δ24Lac and both in-hospital and long-term mortality were investigated. An optimal cut-off was calculated by means of the Youden index.

RESULTS

Patients with lower Δ24Lac were of similar age, but clinically sicker. As continuous variable, higher Δ24Lac was associated with decreased in-hospital mortality (per 1% Δ24Lac; HR 0.987 95%CI 0.985-0.990; p < 0.001) and an optimal Δ24Lac cut-off was calculated at 19%. Δ24Lac ≤ 19% was associated with both increased in-hospital (15% vs 43%; OR 4.11; 95%CI 3.23-5.21; p < 0.001) and long-term mortality (HR 1.54 95%CI 1.28-1.87; p < 0.001), even after correction for APACHE II, need for catecholamines and intubation. We matched 256 patients with Δ24Lac ≤ 19% to case-controls > 19% corrected for APACHE II scores, baseline lactate level and sex: Δ24Lac ≤ 19% remained associated with lower in-hospital and long-term survival.

CONCLUSIONS

Lower Δ24Lac was robustly associated with adverse outcome in critically ill patients, even after correction for confounders. Δ24Lac might constitute an independent, easily available and important parameter for risk stratification in the critically ill.

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 performed to determine whether assessing microcirculation by PI and a new parameter, proportion of perfusion vessel change rate (ΔPPV) 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 T0 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 ΔPPV 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; ΔPPV: 5.9 ± 15.2 vs. 17.9 ± 20.0, t = −2.914, P = 0.005). The cutoff values of PI and ΔPPV were 1.41% and 12.1%, 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 ΔPPV cutoff, all the participants were divided into the following groups: (1) high PI and high ΔPPV group, (2) high PI and low ΔPPV group, (3) low PI and high ΔPPV group, and (4) low PI and low ΔPPV group. The highest Sequential Organ Failure Assessment score (14.5 ± 2.9) was in the low PI and low ΔPPV 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:

PI and ΔPPV 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.

Oxygen-Flow-Pressure Targets for Resuscitation in Critical Hemodynamic Therapy

Far from traditional "vital signs," the field of hemodynamic monitoring (HM) is rapidly developing. However, it is also easy to misunderstand hemodynamic therapy as merely HM and some concrete bundles or guidelines for circulation support. Here, we describe the concept of "critical hemodynamic therapy" and clarify the concepts of the "therapeutic target" and "therapeutic endpoint" in clinical practice. Three main targets (oxygen delivery, blood flow, perfusion pressure) for resuscitation are reviewed in critically ill patients according to the sepsis guidelines and hemodynamic consensus. ScvO2 at least 70% has not been recommended as a directed target for initial resuscitation, and the directed target of mean arterial pressure (MAP) still is 65 mmHg. Moreover, the individual MAP target is underlined, and using flow-dependent monitoring to guide fluid infusion is recommended. The flow-directed target for fluid infusion might be a priority, but it remains controversial in resuscitation. The interpretation of these targets is necessary for adequate resuscitation and the correction of tissue hypoxia. The incoherence phenomenon of resuscitation (macrocirculation and microcirculation, tissue perfusion, and cellular oxygen utilization) is gaining increased attention, and early identification of these incoherences might be helpful to reduce the risk of over-resuscitation.

Skin mottling score and capillary refill time to assess mortality of septic shock since pre-hospital setting

OBJECTIVES

The early identification of septic shock patients at high risk of poor outcome is essential to early initiate optimal treatments and to decide on hospital admission. Biomarkers are often used to evaluate the severity. In prehospital settings, the availability of biomarkers, such as lactate, is restricted. In this context, clinical tools such as skin mottling score (SMS) and capillary refill time (CRT) are more suitable. In this study, we describe prehospital SMS and CRT's ability to predict mortality of patients with septic shock initially cared in the prehospital setting by a mobile intensive care unit.

METHODS

Patients with septic shock who received prehospital medical care admitted to the intensive care unit were retrospectively analyzed.

RESULTS

Sixty-three patients were included. The origin of sepsis was mainly pulmonary (67%). Overall mortality reached 36%. No significant difference was observed in the duration of prehospital medical care between alive and deceased patients. Mean prehospital value of SMS was 3 ± 2 and mean prehospital value of CRT was 5 ± 1 s. A significant association was found between mortality and prehospital SMS (p = 0.02, OR[CI95] = 1.50 [1.08-2.15]) and prehospital CRT (p = 0.04, OR[CI95] = 1.53 [1.04-2.37]). After adjusting for confounding factors using propensity score, the relative risk of death was 6.58 for SMS > 2 and 2.03 for CRT > 4 s.

CONCLUSION

In this study, we report an association between prehospital SMS and CRT, and mortality of patients with septic shock. SMS and CRT are simple tools that could be used to optimize the triage and to decide early intensive care admission.

Monitoring of the physical exam in sepsis

PURPOSE OF REVIEW

Monitoring of mental status and peripheral circulatory changes can be accomplished noninvasively in patients in the ICU. Emphasis on physical examination in conditions such as sepsis have gained increased attention as these evaluations can often serve as a surrogate marker for short-term treatment efficacy of therapeutic interventions. Sepsis associated encephalopathy and mental status changes correlate with worse prognosis in patients. Evaluation of peripheral circulation has been shown to be a convenient, easily accessible, and accurate marker for prognosis in patients with septic shock. The purpose of this article is to emphasize the main findings according to recent literature into the monitoring of physical examination changes in patients with sepsis.

RECENT FINDINGS

Several recent studies have expanded our knowledge about the pathophysiology of mental status changes and the clinical assessment of peripheral circulation in patients with sepsis. Sepsis-associated encephalopathy is associated with an increased rate of morbidity and mortality in an intensive care setting. Increased capillary refill time (CRT) and persistent skin mottling are strongly predictive of mortality, whereas temperature gradients can reveal vasoconstriction and more severe organ dysfunction.

SUMMARY

Monitoring of physical examination changes is a significant and critical intervention in patients with sepsis. Utilizing repeated neurologic evaluations, and assessing CRT, mottling score, and skin temperature gradients should be emphasized as important noninvasive diagnostic tools. The significance of these methods can be incorporated during the utilization of therapeutic strategies in resuscitation protocols in patients with sepsis.

Lactate and microcirculation as suitable targets for hemodynamic optimization in resuscitation of circulatory shock

PURPOSE OF REVIEW

A discussion of recent research exploring the feasibility of perfusion-guided resuscitation of acute circulatory failure with a focus on lactate and microcirculation.

RECENT FINDINGS

Upon diagnosis of shock, hyperlactemia is associated with poor outcome and, under appropriate clinical circumstances, may reflect inadequate tissue perfusion. Persistent hyperlactemia despite resuscitation is even more strongly correlated with morbidity and mortality. Importantly, there is minimal coherence between lactate trends and static hemodynamic measures such as blood pressure, especially after the initial, hypovolemic phase of shock. During this early period, lactate guided-resuscitation is effective and possibly superior to hemodynamic-guided resuscitation. Similar to hyperlactemia, impaired microcirculation is ubiquitous in shock and is evident even in the setting of hemodynamic compensation (i.e., occult shock). Moreover, persistent microcirculatory derangement is associated with poor outcome and may reflect ongoing shock and/or long-lasting damage. Although the wait continues for a microcirculation-guided resuscitation trial, there is progress toward this goal.

SUMMARY

Although questions remain, a multimodal perfusion-based approach to resuscitation is emerging with lactate and microcirculation as core measures. In this model, hyperlactemia and microcirculatory derangement support the diagnosis of shock, may help guide resuscitation during the initial period, and may reflect resuscitation efficacy and iatrogenic harm (e.g., fluid overload).

Early goal-directed therapy using a physiological holistic view: the ANDROMEDA-SHOCK-a randomized controlled trial

Background

Septic shock is a highly lethal condition. Early recognition of tissue hypoperfusion and its reversion are key factors for limiting progression to multiple organ dysfunction and death. Lactate-targeted resuscitation is the gold-standard under current guidelines, although it has several pitfalls including that non-hypoxic sources of lactate might predominate in an unknown proportion of patients. Peripheral perfusion-targeted resuscitation might provide a real-time response to increases in flow that could lead to a more timely decision to stop resuscitation, thus avoiding fluid overload and the risks of over-resuscitation. This article reports the rationale, study design and analysis plan of the ANDROMEDA-SHOCK Study.

Methods

ANDROMEDA-SHOCK is a randomized controlled trial which aims to determine if a peripheral perfusion-targeted resuscitation is associated with lower 28-day mortality compared to a lactate-targeted resuscitation in patients with septic shock with less than 4 h of diagnosis. Both groups will be treated with the same sequential approach during the 8-hour study period pursuing normalization of capillary refill time versus normalization or a decrease of more than 20% of lactate every 2 h. The common protocol starts with fluid responsiveness assessment and fluid loading in responders, followed by a vasopressor and an inodilator test if necessary. The primary outcome is 28-day mortality, and the secondary outcomes are: free days of mechanical ventilation, renal replacement therapy and vasopressor support during the first 28 days after randomization; multiple organ dysfunction during the first 72 h after randomization; intensive care unit and hospital lengths of stay; and all-cause mortality at 90-day. A sample size of 422 patients was calculated to detect a 15% absolute reduction in mortality in the peripheral perfusion group with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle.

Conclusions

If peripheral perfusion-targeted resuscitation improves 28-day mortality, this could lead to simplified algorithms, assessing almost in real-time the reperfusion process, and pursuing more physiologically sound objectives. At the end, it might prevent the risk of over-resuscitation and lead to a better utilization of intensive care unit resources.

Trial registration ClinicalTrials.gov Identifier: NCT03078712 (registered retrospectively March 13th, 2017)

Capillary refill time during fluid resuscitation in patients with sepsis-related hyperlactatemia at the emergency department is related to mortality

INTRODUCTION

Acute circulatory dysfunction in patients with sepsis can evolve rapidly into a progressive stage associated with high mortality. Early recognition and adequate resuscitation could improve outcome. However, since the spectrum of clinical presentation is quite variable, signs of hypoperfusion are frequently unrecognized in patients just admitted to the emergency department (ED). Hyperlactatemia is considered a key parameter to disclose tissue hypoxia but it is not universally available and getting timely results can be challenging in low resource settings. In addition, non-hypoxic sources can be involved in hyperlactatemia, and a misinterpretation could lead to over-resuscitation in an unknown number of cases. Capillary refill time (CRT) is a marker of peripheral perfusion that worsens during circulatory failure. An abnormal CRT in septic shock patients after ICU-based resuscitation has been associated with poor outcome. The aim of this study was to determine the prevalence of abnormal CRT in patients with sepsis-related hyperlactatemia in the early phase after ED admission, and its relationship with outcome.

METHODS

We performed a prospective observational study. Septic patients with hyperlactemia at ED admission subjected to an initial fluid resuscitation (FR) were included. CRT and other parameters were assessed before and after FR. CRT-normal or CRT-abnormal subgroups were defined according to the status of CRT following initial FR, and major outcomes were registered.

RESULTS

Ninety-five hyperlactatemic septic patients were included. Thirty-one percent had abnormal CRT at ED arrival. After FR, 87 patients exhibited normal CRT, and 8 an abnormal one. Patients with abnormal CRT had an increased risk of adverse outcomes (88% vs. 20% p<0.001; RR 4.4 [2.7-7.4]), and hospital mortality (63% vs. 9% p<0.001; RR 6.7 [2.9-16]) as compared to those with normal CRT after FR. Specifically, CRT-normal patients required less frequently mechanical ventilation, renal replacement therapy, and ICU admission, and exhibited a lower hospital mortality.

CONCLUSIONS

Hyperlactatemic sepsis patients with abnormal CRT after initial fluid resuscitation exhibit higher mortality and worse clinical outcomes than patients with normal CRT.

CE: Assessing Patients During Septic Shock Resuscitation

: In 2015, the Surviving Sepsis Campaign six-hour bundle was updated. The revised version now recommends documenting the reassessment of volume status and tissue perfusion after initial fluid resuscitation through a repeated focused examination. This article addresses the practice and interpretation of two components of this examination in adults: capillary refill time and skin mottling score. It further discusses how to best integrate these noninvasive parameters into the care of patients undergoing resuscitation for septic shock.

How to assess hemodynamic status in very preterm newborns in the first week of life?

BACKGROUND

Assessing hemodynamic status in preterm newborns is an essential task, as many studies have shown increased morbidity when hemodynamic parameters are abnormal. Although oscillometric monitoring of arterial blood pressure (BP) is widely used due to its simplicity and lack of side effects, these values are not always correlated with microcirculation and oxygen delivery.

OBJECTIVES

This review focuses on different tools for the assessment of hemodynamic status in preterm newborns. These include the measurement of clinical (BP, capillary refill time and urinary output (UO)) or biological parameters (lactate analysis), functional echocardiography, and near-infrared spectroscopy (NIRS). We describe the concepts and techniques involved in these tools in detail, and examine the interest and limitations of each type of assessment.

CONCLUSIONS

This review highlights the complementarities between the different parameters used to assess hemodynamic status in preterm newborns during the first week of life. The analysis of arterial BP measured by oscillometric monitoring must take into account other clinical data, in particular capillary refill time and UO, and biological data such as lactate levels. Echocardiography improves noninvasive hemodynamic management in newborns but requires specific training. In contrast, NIRS may be useful in monitoring the clinical course of infants at risk of, or presenting with, hypotension. It holds the potential for early and noninvasive identification of silent hypoperfusion in critically ill preterm infants. However, more data are needed to confirm the usefulness of this promising tool in significantly changing the outcome of these infants.

Perfusion indices revisited

Monitoring of tissue perfusion is an essential step in the management of acute circulatory failure. The presence of cellular dysfunction has been a basic component of shock definition even in the absence of hypotension. Monitoring of tissue perfusion includes biomarkers of global tissue perfusion and measures for assessment of perfusion in non-vital organs. The presence of poor tissue perfusion in a shocked patient is usually associated with worse outcome. Persistently impaired perfusion despite adequate resuscitation is also associated with worse outcome. Thus, normalization of some perfusion indices has become one of the resuscitation targets in patients with septic shock. Although the collective evidence shows the clear relation between impaired peripheral perfusion and mortality, the use of different perfusion indices as a resuscitation target needs more research.

A hypoperfusion context may aid to interpret hyperlactatemia in sepsis-3 septic shock patients: a proof-of-concept study

Background

Persistent hyperlactatemia is particularly difficult to interpret in septic shock. Besides hypoperfusion, adrenergic-driven lactate production and impaired lactate clearance are important contributors. However, clinical recognition of different sources of hyperlactatemia is unfortunately not a common practice and patients are treated with the same strategy despite the risk of over-resuscitation in some. Indeed, pursuing additional resuscitation in non-hypoperfusion-related cases might lead to the toxicity of fluid overload and vasoactive drugs. We hypothesized that two different clinical patterns can be recognized in septic shock patients through a multimodal perfusion monitoring. Hyperlactatemic patients with a hypoperfusion context probably represent a more severe acute circulatory dysfunction, and the absence of a hypoperfusion context is eventually associated with a good outcome. We performed a retrospective analysis of a database of septic shock patients with persistent hyperlactatemia after initial resuscitation.

Results

We defined hypoperfusion context by the presence of a ScvO₂ < 70%, or a P(cv-a)CO₂ ≥6 mmHg, or a CRT ≥4 s together with hyperlactatemia. Ninety patients were included, of whom seventy exhibited a hypoperfusion-related pattern and 20 did not. Although lactate values were comparable at baseline (4.8 ± 2.8 vs. 4.7 ± 3.7 mmol/L), patients with a hypoperfusion context exhibited a more severe circulatory dysfunction with higher vasopressor requirements, and a trend to longer mechanical ventilation days, ICU stay, and more rescue therapies. Only one of the 20 hyperlactatemic patients without a hypoperfusion context died (5%) compared to 11 of the 70 with hypoperfusion-related hyperlactatemia (16%).

Conclusions

Two different clinical patterns among hyperlactatemic septic shock patients may be identified according to hypoperfusion context. Patients with hyperlactatemia plus low ScvO₂, or high P(cv-a)CO₂, or high CRT values exhibited a more severe circulatory dysfunction. This provides a starting point to launch further prospective studies to confirm if this approach can lead to a more selective resuscitation strategy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0253-x) contains supplementary material, which is available to authorized users.

Endpoints in resuscitation

PURPOSE OF REVIEW

Shock occurs because of a failure to deliver adequate oxygen to meet the metabolic demands of the body resulting in metabolic acidosis, inflammation, and coagulopathy. Resuscitation is the process of treating shock in an attempt to restore normal physiology. Various hemodynamic, metabolic, and regional endpoints have been described to evaluate the degree of shock and guide resuscitation efforts. We will briefly describe these endpoints, and propose damage control resuscitation as an additional endpoint.

RECENT FINDINGS

Serum lactate, base deficit, and pH are well established endpoints of resuscitation that provide valuable information when trended over time; however, a single value is inadequate to determine adequacy of resuscitation. Rapid normalization of central venous oxygen concentration has been associated with improved survival, and bedside transthoracic echocardiography can be a reliable assessment of volume status. In hypovolemic/hemorrhagic shock, early hypotensive, or controlled resuscitation strategies have been associated with improved survival, and hemostatic strategies guided by thrombelastography using a balanced transfusion approach result in improved hemostasis.

SUMMARY

Numerous endpoints are available; however, no single endpoint is universally applicable. Damage control resuscitation strategies have demonstrated improved survival, hemostasis, and less early death from exsanguination, suggesting that hemorrhage control should be an additional endpoint in resuscitation.

The value of blood lactate kinetics in critically ill patients: a systematic review

BACKGROUND

The time course of blood lactate levels could be helpful to assess a patient's response to therapy. Although the focus of published studies has been largely on septic patients, many other studies have reported serial blood lactate levels in different groups of acutely ill patients.

METHODS

We performed a systematic search of PubMed, Science Direct, and Embase until the end of February 2016 plus reference lists of relevant publications. We selected all observational and interventional studies that evaluated the capacity of serial blood lactate concentrations to predict outcome. There was no restriction based on language. We excluded studies in pediatric populations, experimental studies, and studies that did not report changes in lactate values or all-cause mortality rates. We separated studies according to the type of patients included. We collected data on the number of patients, timing of lactate measurements, minimum lactate level needed for inclusion if present, and suggested time interval for predictive use.

RESULTS

A total of 96 studies met our criteria: 14 in general ICU populations, five in general surgical ICU populations, five in patients post cardiac surgery, 14 in trauma patients, 39 in patients with sepsis, four in patients with cardiogenic shock, eight in patients after cardiac arrest, three in patients with respiratory failure, and four in other conditions. A decrease in lactate levels over time was consistently associated with lower mortality rates in all subgroups of patients. Most studies reported changes over 6, 12 or 24 hrs, fewer used shorter time intervals. Lactate kinetics did not appear very different in patients with sepsis and other types of patients. A few studies suggested that therapy could be guided by these measurements.

CONCLUSIONS

The observation of a better outcome associated with decreasing blood lactate concentrations was consistent throughout the clinical studies, and was not limited to septic patients. In all groups, the changes are relatively slow, so that lactate measurements every 1-2 hrs are probably sufficient in most acute conditions. The value of lactate kinetics appears to be valid regardless of the initial value.

Effects of dexmedetomidine and esmolol on systemic hemodynamics and exogenous lactate clearance in early experimental septic shock

BACKGROUND

Persistent hyperlactatemia during septic shock is multifactorial. Hypoperfusion-related anaerobic production and adrenergic-driven aerobic generation together with impaired lactate clearance have been implicated. An excessive adrenergic response could contribute to persistent hyperlactatemia and adrenergic modulation might be beneficial. We assessed the effects of dexmedetomidine and esmolol on hemodynamics, lactate generation, and exogenous lactate clearance during endotoxin-induced septic shock.

METHODS

Eighteen anesthetized and mechanically ventilated sheep were subjected to a multimodal hemodynamic/perfusion assessment including hepatic and portal vein catheterizations, total hepatic blood flow, and muscle microdialysis. After monitoring, all received a bolus and continuous infusion of endotoxin. After 1 h they were volume resuscitated, and then randomized to endotoxin-control, endotoxin-dexmedetomidine (sequential doses of 0.5 and 1.0 μg/k/h) or endotoxin-esmolol (titrated to decrease basal heart rate by 20 %) groups. Samples were taken at four time points, and exogenous lactate clearance using an intravenous administration of sodium L-lactate (1 mmol/kg) was performed at the end of the experiments.

RESULTS

Dexmedetomidine and esmolol were hemodynamically well tolerated. The dexmedetomidine group exhibited lower epinephrine levels, but no difference in muscle lactate. Despite progressive hypotension in all groups, both dexmedetomidine and esmolol were associated with lower arterial and portal vein lactate levels. Exogenous lactate clearance was significantly higher in the dexmedetomidine and esmolol groups.

CONCLUSIONS

Dexmedetomidine and esmolol were associated with lower arterial and portal lactate levels, and less impairment of exogenous lactate clearance in a model of septic shock. The use of dexmedetomidine and esmolol appears to be associated with beneficial effects on gut lactate generation and lactate clearance and exhibits no negative impact on systemic hemodynamics.

Changes in peripheral perfusion relate to visceral organ perfusion in early septic shock: A pilot study

PURPOSE

To correlate clinical indicators of peripheral perfusion with visceral organ vascular tone in 30 septic shock patients.

MATERIALS AND METHODS

In a prospective pilot study, capillary refill time, the Mottling score, and peripheral temperature were determined within 24, 48, and 72 hours after intensive care unit admission. Simultaneously, pulsatility indices in the liver, spleen, kidneys, and intestines were measured by Doppler ultrasonography. Correlation analyses were calculated, applying an adjusted significance level (P< .0125) to correct for multiple testing.

RESULTS

Significant relationships were observed between the pulsatility index of selected organs and the capillary refill time (intestines: r= 0.325, P= .007), and the Mottling score (kidneys: r= 0.396, P= .006), but not peripheral temperature (all r< 0.14, P> .05). An association over time was observed for the capillary refill time and pulsatility index of the liver (P= .04) and intestines (P= .03) as well as for the Mottling score and the kidneys' pulsatility index (P= .03), but not for peripheral temperature and any visceral organs' pulsatility index.

CONCLUSIONS

Capillary refill time and skin mottling may be correlated with the pulsatility index, a sonographic surrogate of vascular tone, of visceral organs in early septic shock.

New perspectives of volemic resuscitation in polytrauma patients: a review

Nowadays, fluid resuscitation of multiple trauma patients is still a challenging therapy. Existing therapies for volume replacement in severe haemorrhagic shock can lead to adverse reactions that may be fatal for the patient. Patients presenting with multiple trauma often develop hemorrhagic shock, which triggers a series of metabolic, physiological and cellular dysfunction. These disorders combined, lead to complications that significantly decrease survival rate in this subset of patients. Volume and electrolyte resuscitation is challenging due to many factors that overlap. Poor management can lead to post-resuscitation systemic inflammation causing multiple organ failure and ultimately death. In literature, there is no exact formula for this purpose, and opinions are divided. This paper presents a review of modern techniques and current studies regarding the management of fluid resuscitation in trauma patients with hemorrhagic shock. According to the literature and from clinical experience, all aspects regarding post-resuscitation period need to be considered. Also, for every case in particular, emergency therapy management needs to be rigorously respected considering all physiological, biochemical and biological parameters.

Prognostic utility of plasma lactate measured between 24 and 48 h after initiation of early goal-directed therapy in the management of sepsis, severe sepsis, and septic shock

Background

Based on the proven efficacy of lactate in predicting mortality and morbidity in sepsis when measured early in the resuscitative protocol, our group hypothesized that this utility extends later in the course of care. This study sought to investigate the prognostic potential of plasma lactate clearance measured 24–48 h after the initiation of treatment for nonsurgical patients with sepsis, severe sepsis, and septic shock.

Methods

Plasma lactate values, measured 24–48 h after the initiation of treatment, were collected in nonsurgical septic, severe septic, and septic shock patients. The primary outcome was 30-day mortality, while secondary outcomes included requirements for vasopressors and boluses of intravenous fluids. Analysis of these three outcomes was performed while controlling for clinical severity as measured by Sequential Organ Failure Assessment (SOFA), renal dysfunction, and hepatic dysfunction. Lactate clearance was defined as the percent change in plasma lactate levels measured after 24–48 h of treatment from the plasma lactate level at initial presentation.

Results

Two hundred twenty-nine nonsurgical patients were divided into two groups, clearers (above median lactate clearance [31.6 %]) and nonclearers (below median lactate clearance [31.6 %]). The adjusted odds ratio of mortality in clearers compared to nonclearers was 0.39 (CI 0.20–0.76) (p = 0.006). For vasopressor requirement, the adjusted odds ratio was 0.41 (CI 0.21–0.79) in clearers compared to nonclearers (p = 0.008). For intravenous fluid bolus requirement, the adjusted odds ratio was 0.81 (CI 0.48–1.39) in clearers compared to nonclearers (p = 0.45).

Conclusions

Lower plasma lactate clearance 24–48 h after the initiation of treatment is associated with higher 30-day mortality and requirements for vasopressors in nonsurgical septic patients and may be a useful noninvasive measurement for guiding late-sepsis treatment. Further investigation looking at mechanisms and therapeutic targets to improve lactate clearance in late sepsis may improve patient mortality and outcomes.

Lactate kinetics in sepsis and septic shock: a review of the literature and rationale for further research

Over the last two decades, there have been vast improvements in sepsis-related outcomes, largely resulting from the widespread adoption of aggressive fluid resuscitation and infection control. With increased understanding of the pathophysiology of sepsis, novel diagnostics and resuscitative interventions are being discovered. In recent years, few diagnostic tests like lactate have engendered more attention and research in the sepsis arena. Studies highlighting lactate’s prognostic potential for mortality and other outcomes are ubiquitous and largely focus on the early stage of sepsis management, defined as the initial 6 h and widely referred to as the “golden hours.” Additional investigations, although more representative of surgical and trauma patients, suggest that lactate measurements beyond 24 h from the initiation of resuscitation continue to have predictive and prognostic utility. This review summarizes the current research and evidence regarding lactate’s utility as a prognosticator of clinical outcomes in both early and late sepsis management, defines the mechanism of lactate production and clearance, and identifies areas warranting further research.

Clinical classification of tissue perfusion based on the central venous oxygen saturation and the peripheral perfusion index

Introduction

We investigated whether combining the peripheral perfusion index (PI) and central venous oxygen saturation(ScvO₂) would identify subsets of patients for assessing the tissue perfusion and predicting outcome during the resuscitation in critically ill patients.

Methods

A total of 202 patients with central venous catheters for resuscitation were enrolled in this prospective observational study. The arterial, central venous blood gas and the PI were measured simultaneously at the enrollment (T0) and 8 h (T8) after early resuscitation. Based on the distribution of the PI in healthy population, a cutoff of PI ≥1.4 was defined as a normal PI. Moreover, the critical value of PI was defined as the best cutoff value related to the mortality in the study population. The PI impairment stratification is defined as follows: a normal PI(≥1.4), mild PI impairment (critical value < PI < 1.4) and critical PI impairment (PI ≤ critical value).

Results

The PI at T8 was with the greatest AUC for prediction the 30-day mortality and PI is an independent risk factor for 30-day mortality. Moreover, a cutoff of PI < 0.6 is related to poor outcomes following resuscitation. So, based on cutoffs of ScvO₂ (70 %) and critical PI (0.6) at T8, we assigned the patients to four categories: group 1 (PI ≤ 0.6 on ScvO₂ < 70 %), group 2 (PI ≤ 0.6 on ScvO₂ ≥ 70 %), group 3 (PI > 0.6 on ScvO₂ < 70 %), and group 4 (PI > 0.6 on ScvO₂ ≥ 70 %). The combination of low ScvO₂(<70 %) and PI(≤0.6) was associated with the lowest survival rates at 30 days [log rank (Mantel–Cox) = 87.518, p < 0.0001]. The sub-group patients who had high ScvO₂(>80 %) at T8 were with low mortality and high PI. Moreover, the normal PI (≥1.4) did not show a better outcome than mild impaired PI (0.6-1.4) patients who had a normalized ScvO₂(>70 %) after resuscitation. The PI was correlated with the lactate, P(v-a)CO₂, and ScvO₂ in all the measurements (n = 404). These relationships are strengthened with abnormal PI (PI < 1.4) but not with normal PI (PI ≥ 1.4).

Conclusion

Complementing ScvO₂ assessment with PI can better identify endpoints of resuscitation and adverse outcomes. Pursuing a normalized PI (≥1.4) may not result in better outcomes for a mild impaired PI after ScvO₂ is normalized.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1057-8) contains supplementary material, which is available to authorized users.

Principles of Fluid Management

Fluid therapy is the most common intervention received by acutely ill hospitalized patients; however, important questions on its optimal use remain. Its prescription should be patient and context specific, with clear indications and contradictions, and have the type, dose, and rate specified. Any fluid therapy, if provided inappropriately, can contribute unnecessary harm to patients. The quantitative toxicity of fluid therapy contributes to worse outcomes; this should prompt greater bedside attention to fluid prescription, fluid balance, development of avoidable complications attributable to fluid overload, and for the timely deresuscitation of patients whose clinical status and physiology allow active fluid mobilization.

Impairment of exogenous lactate clearance in experimental hyperdynamic septic shock is not related to total liver hypoperfusion

Introduction

Although the prognostic value of persistent hyperlactatemia in septic shock is unequivocal, its physiological determinants are controversial. Particularly, the role of impaired hepatic clearance has been underestimated and is only considered relevant in patients with liver ischemia or cirrhosis. Our objectives were to establish whether endotoxemia impairs whole body net lactate clearance, and to explore a potential role for total liver hypoperfusion during the early phase of septic shock.

Methods

After anesthesia, 12 sheep were subjected to hemodynamic/perfusion monitoring including hepatic and portal catheterization, and a hepatic ultrasound flow probe. After stabilization (point A), sheep were alternatively assigned to lipopolysaccharide (LPS) (5 mcg/kg bolus followed by 4 mcg/kg/h) or sham for a three-hour study period. After 60 minutes of shock, animals were fluid resuscitated to normalize mean arterial pressure. Repeated series of measurements were performed immediately after fluid resuscitation (point B), and one (point C) and two hours later (point D). Monitoring included systemic and regional hemodynamics, blood gases and lactate measurements, and ex-vivo hepatic mitochondrial respiration at point D. Parallel exogenous lactate and sorbitol clearances were performed at points B and D. Both groups included an intravenous bolus followed by serial blood sampling to draw a curve using the least squares method.

Results

Significant hyperlactatemia was already present in LPS as compared to sham animals at point B (4.7 (3.1 to 6.7) versus 1.8 (1.5 to 3.7) mmol/L), increasing to 10.2 (7.8 to 12.3) mmol/L at point D. A significant increase in portal and hepatic lactate levels in LPS animals was also observed. No within-group difference in hepatic DO₂, VO₂ or O₂ extraction, total hepatic blood flow (point D: 915 (773 to 1,046) versus 655 (593 to 1,175) ml/min), mitochondrial respiration, liver enzymes or sorbitol clearance was found. However, there was a highly significant decrease in lactate clearance in LPS animals (point B: 46 (30 to 180) versus 1,212 (743 to 2,116) ml/min, P <0.01; point D: 113 (65 to 322) versus 944 (363 to 1,235) ml/min, P <0.01).

Conclusions

Endotoxemia induces an early and severe impairment in lactate clearance that is not related to total liver hypoperfusion.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0928-3) contains supplementary material, which is available to authorized users.