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

Peripheral perfusion index of pulse oximetry in adult patients: a narrative review

The peripheral perfusion index (PI) is derived from pulse oximetry and is defined as the ratio of the pulse wave of the pulsatile portion (arteries) to the non-pulsatile portion (venous and other tissues). A growing number of clinical studies have supported the use of PI in various clinical scenarios, such as guiding hemodynamic management and serving as an indicator of outcome and organ function. In this review, we will introduce and discuss this traditional but neglected indicator of the peripheral microcirculatory perfusion. Further clinical trials are required to clarify the normal and critical values of PI for different monitoring devices in various clinical conditions, to establish different standards of PI-guided strategies, and to determine the effect of PI-guided therapy on outcome.

Dilemmas of Adopting Goal-Directed Perfusion in Extracorporeal Circulation: A Narrative Review

OBJECTIVE

Extracorporeal circulation (ECC) is generally based on standards established in the last decade. In recent years, a concept of perfusion management during ECC, goal-directed perfusion (GDP), has emerged to create optimal conditions for oxygen delivery and extraction, initiated by Rannuci et al. The aim of the present work was to determine whether the ECC procedure can truly be optimized with the current state of knowledge and understanding of human physiology.

METHODS

Discussed articles from 2017 to 2022 were selected from the MEDLINE (PubMed) database using the keywords "cardiopulmonary bypass" AND "cardiac surgery" AND "oxygen delivery" with the conditions of "clinical trial" OR "randomized controlled trial."

RESULTS

The concept of GDP is an attempt to reproduce the physiological conditions of tissue respiration during ECC. Published articles, also due to their retrospective nature, are based on standards and recommendations that do not fully fit the field of physiological circulation. There are still insufficient tools to assess the relationship between volemia, perfusion pressure, and pump performance. Limitations include indications for vasoactive drugs. Methodology has rarely taken into account the period of starting and stopping the heart-lung machine, the most pronounced periods of circulatory destabilization with reduced oxygen delivery.

CONCLUSIONS

Problems associated with ECC such as acute kidney injury, liver failure, vasoplegic syndrome, and others must await its resolution. The use of advanced monitoring technology and data engineering may allow the development of baseline hemodynamic models, which may make the ECC procedure more physiologic and thus improve the safety of the procedure.

Blood gas analysis as a surrogate for microhemodynamic monitoring in sepsis

BACKGROUND

Emergency patients with sepsis or septic shock are at high risk of death. Despite increasing attention to microhemodynamics, the clinical use of advanced microcirculatory assessment is limited due to its shortcomings. Since blood gas analysis is a widely used technique reflecting global oxygen supply and consumption, it may serve as a surrogate for microcirculation monitoring in septic treatment.

METHODS

We performed a search using PubMed, Web of Science, and Google scholar. The studies and reviews that were most relevant to septic microcirculatory dysfunctions and blood gas parameters were identified and included.

RESULTS

Based on the pathophysiology of oxygen metabolism, the included articles provided a general overview of employing blood gas analysis and its derived set of indicators for microhemodynamic monitoring in septic care. Notwithstanding flaws, several parameters are linked to changes in the microcirculation. A comprehensive interpretation of blood gas parameters can be used in order to achieve hemodynamic optimization in septic patients.

CONCLUSION

Blood gas analysis in combination with clinical performance is a reliable alternative for microcirculatory assessments. A deep understanding of oxygen metabolism in septic settings may help emergency physicians to better use blood gas analysis in the evaluation and treatment of sepsis and septic shock.

Time of dissociation between microcirculation, macrocirculation, and lactate levels in a rabbit model of early endotoxemic shock

Background

The relationship between macrocirculation and microcirculation remains controversial. The loss of coherence between microcirculation and macrocirculation has already been found in late-stage sepsis shock. The objective of this study was to determine the earliest possible time of detecting the loss of coherence between microcirculation and macrocirculation in early-stage endotoxemic shock.

Methods

We randomized 24 female New Zealand white rabbits into two groups: endotoxemic shock group (n = 14) and control group (n = 10). Rabbits in the endotoxemic shock group were equipped with arterial and venous catheters and received an intravenous infusion of Escherichia coli lipopolysaccharide (LPS, 2 mg/kg over 10 min). Rabbits in the control group received the same dose of saline infusion. Microcirculatory perfusion parameters were assessed in the sublingual mucosa using sidestream dark-field video microscopy. Systemic hemodynamics and blood lactate levels were measured at baseline and over a 120-min period.

Results

Ninety minutes after completing LPS infusion, all animals in the endotoxemic shock group developed a hypodynamic septic condition, characterized by low cardiac output and increased systemic vascular resistance; 120 min after completing LPS infusion, the mean arterial pressure decreased by 25% (P = 0.01), confirming ongoing endotoxemic shock. However, significant decreases in sublingual microcirculatory parameters of small vessels (microvascular flow index, perfused vessel density, and proportion of small perfused vessels) were observed 30 min after completing LPS infusion (P = 0.01, for all), and threshold decreases of 30% were found 60 min after completing LPS infusion (P = 0.001, for all) in the endotoxemic shock group. Lactate levels significantly increased to more than 2 mm/L at 90 min and more than 4 mm/L at 120 min in the endotoxemic shock group (P = 0.02 and P = 0.01, respectively).

Conclusions

Changes in microcirculatory perfusion precede changes in macrocirculation and lactate levels in a rabbit model of endotoxemia shock. Microcirculation, macrocirculation, and oxygen metabolism are distinct in early-stage endotoxic shock.

Effect of norepinephrine challenge on cardiovascular determinants assessed using a mathematical model in septic shock: a physiological study

BACKGROUND

The present study investigated the cardiovascular determinants of cardiac output (CO), mean systemic filling pressure analogue (Pmsa) derived by Geoffrey Parkin, efficiency of heart (Eh) and related parameters to a norepinephrine (NE) challenge [an increase of 10 mmHg mean arterial pressure (MAP) by NE] in septic shock patients using of a mathematical model.

METHODS

Twenty-seven septic shock patients with pulse index continuous cardiac output (PiCCO) monitoring were enrolled. These patients required NE to maintain an individualized MAP for organ perfusion after early fluid resuscitation based on their clinical condition. NE was decreased to obtain a decrease of 10 mmHg from base MAP (MAP-10mmHg), and the NE doses were adjusted to return MAP to baseline (MAPbase) and produce an increase of 10 mmHg from MAPbase (MAP+10mmHg). Two NE challenge episodes were analyzed for each patient: from MAP-10mmHg to MAPbase and from MAPbase to MAP+10mmHg. The Pmsa, pressure gradient for venous return (PGvr), and Eh (PGvr relative to Pmsa) were estimated using a mathematical model for the three MAP levels (MAP-10mmHg, MAPbase and MAP+10mmHg).

RESULTS

A total of 54 episodes of NE challenges were obtained in 27 patients. Significant and consistent increases were observed in the central venous pressure (CVP), Pmsa, and PGvr in response during the NE titration. ΔCO negatively and significantly correlated with ΔCVP (r=-0.722, P<0.0001), ΔPmsa (r=-0.549, P<0.0001), ΔResistance of venous return (Rvr) (r=-0.597, P<0.0001), and ΔResistance of systemic vascular beds (Rsys) (r=-0.597, P<0.0001). Episodes of decreasing CO/Eh were associated with a higher ΔCVP than the CO/Eh-increasing episodes. The area under the curve (AUC) of ΔCVP to predict decreased CO by the incremental NE was 0.86, and the AUC of ΔCVP to predict decreased Eh was 0.94. A cutoff of ΔCVP >1.5 mmHg for detecting decreased CO resulted in a sensitivity of 75% and a specificity of 94.1%. A cutoff of ΔCVP >1.5 mmHg for detecting decreased Eh resulted in a sensitivity of 64.3% and a specificity of 100%.

CONCLUSIONS

There were a highly divergent response in Eh and CO to afterload challenge episodes of an NE-induced 10mmHg increase in MAP. An increase in CVP may be an early alarm to identify the reduction in CO/Eh during an NE-induced increase of MAP.

Clinical features and mortality-related factors of extensive burns among young adults: the Kunshan disaster experience

Background

The aim of the study was to identify the clinical features and the factors associated with burn induced mortality among young adults after exposure to indoor explosion and fire.

Methods

This is an observational study which included burn patients who were admitted to eighteen ICUs after a fire disaster. Epidemiologic and clinical characteristics, as well as therapy were recorded. The primary outcome was 90-day mortality. The mortality-related factors were also analyzed.

Results

There were 167 burn patients enrolled in the study, the median age was 38 years, 62 (37.1%) patients died within 90 days. Seventy-one percent of patients had a burn size ≥90% TBSA, and 73.7% of patients had a full-thickness burn area above 50% TBSA. The survivors had lower Baux scores, and received earlier escharectomy and autologous skin grafts. The 50% mortality rates (LA50s) for burn size and full-thickness burn area were 95.8% and 88.6% TBSA, respectively. The multivariate analysis showed that full-thickness burn area over 50% TBSA and residual burned surface area (RBSA)/TBSA at 28 days were strong predictors of mortality among burn patients (odds ratio 2.55; 95% CI, 1.01 to 6.44, P=0.047; odds ratio 1.07; 95% CI, 1.04 to 1.09, P<0.001). The ROC curve-based cut-off values of RBSA/TBSA at 28 days for predicting 90-day mortality were 62.5%.

Conclusions

Burn size and full-thickness burn area were the main risk factors for poor outcome in patients with extensive burns. Earlier escharectomy and autologous skin grafts may improve outcomes.

Does End-Expiratory Occlusion Test Predict Fluid Responsiveness in Mechanically Ventilated Patients? A Systematic Review and Meta-Analysis

BACKGROUND

We performed a systematic review and meta-analysis of studies investigating the end-expiratory occlusion (EEO) test induced changes in cardiac index (CI) and in arterial pressure as predictors of fluid responsiveness in adults receiving mechanical ventilation.

METHODS

MEDLINE, EMBASE, Cochrane Database, and Chinese database were screened for relevant original and review articles. The meta-analysis determined the pooled sensitivity, specificity, diagnostic odds ratio, area under the receiver operating characteristic curve (AUROC), and threshold for the EEO test assessed with CI and arterial pressure. In addition, heterogeneity and subgroup analyses were performed.

RESULTS

We included 13 studies involving 479 adult patients and 523 volume expansion. Statistically significant heterogeneity was identified, and meta-regression indicated that prone position was the major sources of heterogeneity. After removal of the study performed in prone position, heterogeneity became nonsignificant. EEO-induced changes in CI (or surrogate) are accurate for predicting fluid responsiveness in semirecumbent or supine patients, with excellent pooled sensitivity of 92% (95% CI, 0.88-0.95, I = 0.00%), specificity of 89% (95% CI, 0.83-0.93, I = 34.34%), and a summary AUROC of 0.95 (95% CI, 0.93-0.97). The mean threshold was an EEO-induced increase in CI (or surrogate) of more than 4.9 ± 1.5%. EEO test exhibited better diagnostic performance in semirecumbent or supine patients than prone patients, with higher AUROC (0.95 vs. 0.65; P < 0.001). In addition, EEO test exhibited higher specificity (0.93 vs. 0.83, P < 0.001) in patients ventilated with low tidal volume compared with normal or nearly normal tidal volume. However, EEO test was less accurate when its hemodynamic effects were detected on arterial pressure. EEO-induced changes in arterial pressure exhibited a lower sensitivity (0.88 vs. 0.92; P = 0.402), specificity (0.77 vs. 0.90; P = 0.019), and AUROC (0.87 vs. 0.96; P < 0.001) compared with EEO-induced changes in CI (or surrogate).

CONCLUSIONS

EEO test is accurate to predict fluid responsiveness in semirecumbent or supine patients but not in prone patients. EEO test exhibited higher specificity in patients ventilated with low tidal volume, and its accuracy is better when its hemodynamic effects are assessed by direct measurement of CI than by the arterial pressure.

Critical hemodynamic therapy oriented resuscitation helping reduce lung water production and improve survival

BACKGROUND

Increased extravascular lung water (EVLW) in shock is common in the critically ill patients. This study aimed to explore the effect of cardiac output (CO) on EVLW and its relevant influence on prognosis.

METHODS

The hemodynamic data of 428 patients with pulse-indicated continuous CO catheterization from Department of Critical Care Medicine, Peking Union Medical College Hospital were retrospectively collected and analyzed. The patients were assigned to acute respiratory distress syndrome group, cardiogenic shock group, septic shock group, and combined shock (cardiogenic and septic) group according to their symptoms. Information on 28-day mortality and renal function was also collected.

RESULTS

The CO and EVLW index (EVLWI) in the cardiogenic and combined shock groups were lower than those in the other groups (acute respiratory distress syndrome group vs. cardiogenic shock group vs. septic shock group vs. combined shock group: CO, 5.1 [4.0, 6.2] vs. 4.7 [4.0, 5.7] vs. 5.5 [4.3, 6.7] vs. 4.6 [3.5, 5.7] at 0 to 24 h, P = 0.009; 4.6 [3.8, 5.6] vs. 4.8 [4.1, 5.7] vs. 5.3 [4.4, 6.5] vs. 4.5 [3.8, 5.3] at 24 to 48 h, P = 0.048; 4.5 [4.1, 5.4] vs. 4.8 [3.8, 5.5] vs. 5.3 [4.0, 6.4] vs. 4.0 [3.2, 5.4] at 48 to 72 h, P = 0.006; EVLWI, 11.4 [8.7, 19.1] vs. 7.9 [6.6, 10.0] vs. 8.8 [7.4, 11.0] vs. 8.2 [6.7, 11.3] at 0 to 24 h, P < 0.001; 11.8 [7.7, 17.2] vs. 7.8 [6.3, 10.2] vs. 8.7 [6.6, 12.2] vs. 8.0 [6.6, 11.1] at 24 to 48 h, P < 0.001; and 11.3 [7.7, 18.7] vs. 7.5 [6.3, 10.0] vs. 8.8 [6.3, 12.2] vs. 8.4 [6.4, 11.2] at 48 to 72 h, P < 0.001. The trend of the EVLWI in the septic shock group was higher than that in the cardiogenic shock group (P < 0.05). Moreover, there existed some difference in the pulmonary vascular permeability index among the cardiogenic shock group, the septic shock group, and the combined shock group, without statistical significance (P > 0.05). In addition, there was no significant difference in tissue perfusion or renal function among the four groups during the observation period (P > 0.05). However, the cardiogenic shock group had a higher 28-day survival rate than the other three groups [log rank (Mantel-Cox) = 31.169, P < 0.001].

CONCLUSION

Tissue-aimed lower CO could reduce the EVLWI and achieve a better prognosis.

Assessment of the peripheral microcirculation in patients with and without shock: a pilot study on different methods

Microvascular dysfunction has been associated with adverse outcomes in critically ill patients, and the current concept of hemodynamic incoherence has gained attention. Our objective was to perform a comprehensive analysis of microcirculatory perfusion parameters and to investigate the best variables that could discriminate patients with and without circulatory shock during early intensive care unit (ICU) admission. This prospective observational study comprised a sample of 40 adult patients with and without circulatory shock (n = 20, each) admitted to the ICU within 24 h. Peripheral clinical [capillary refill time (CRT), peripheral perfusion index (PPI), skin-temperature gradient (Tskin-diff)] and laboratory [arterial lactate and base excess (BE)] perfusion parameters, in addition to near-infrared spectroscopy (NIRS)-derived variables were simultaneously assessed. While lactate, BE, CRT, PPI and Tskin-diff did not differ significantly between the groups, shock patients had lower baseline tissue oxygen saturation (StO₂) [81 (76–83) % vs. 86 (76–90) %, p = 0.044], lower StO₂min [50 (47–57) % vs. 55 (53–65)  %, p = 0.038] and lower StO₂max [87 (80–92) % vs. 93 (90–95) %, p = 0.017] than patients without shock. Additionally, dynamic NIRS variables [recovery time (r = 0.56, p = 0.010), descending slope (r = − 0.44, p = 0.05) and ascending slope (r = − 0.54, p = 0.014)] and not static variable [baseline StO₂ (r = − 0.24, p = 0.28)] exhibited a significant correlation with the administered dose of norepinephrine. In our study with critically ill patients assessed within the first twenty-four hours of ICU admission, among the perfusion parameters, only NIRS-derived parameters could discriminate patients with and without shock.

Interpretation of venous-to-arterial carbon dioxide difference in the resuscitation of septic shock patients

The venous-to-arterial carbon dioxide difference [P(v-a)CO₂] was calculated from the difference of venous CO₂ and arterial CO₂, which has been used to reflect the global flow in the circulatory shock. Moreover, recent clinical studies found the P(v-a)CO₂ was related to the sublingual microcirculation perfusion in the sepsis. However, it is still controversial that whether P(v-a)CO₂ could be used to assess the microcirculatory flow in septic patients. Moreover, the related influent factors should be taken into account when interpreting P(v-a)CO₂ in clinical practice. This paper reviews the relevant experimental and clinical scenarios of P(v-a)CO₂ with the aim to help intensivists to use this parameter in the resuscitation of septic shock patients. Furthermore, we propose a conceptual framework to manage a high P(v-a)CO₂ value in the resuscitation of septic shock. The triggers of correcting an elevated P(v-a)CO₂ should take into consideration the other tissue perfusion parameters. Additionally, more evidence is required to validate that a decreasing in P(v-a)CO₂ by increasing cardiac output would result in improvement of microcirculation. Further investigations are necessary to clarify the relationship between P(v-a)CO₂ and microcirculation.

Resuscitation incoherence and dynamic circulation-perfusion coupling in circulatory shock

OBJECTIVE

Poor tissue perfusion/cellular hypoxia may persist despite restoration of the macrocirculation (Macro). This article reviewed the literatures of coherence between hemodynamics and tissue perfusion in circulatory shock.

DATA SOURCES

We retrieved information from the PubMed database up to January 2018 using various search terms or/and their combinations, including resuscitation, circulatory shock, septic shock, tissue perfusion, hemodynamic coherence, and microcirculation (Micro).

STUDY SELECTION

The data from peer-reviewed journals printed in English on the relationships of tissue perfusion, shock, and resuscitation were included.

RESULTS

A binary (coherence/incoherence, coupled/uncoupled, or associated/disassociated) mode is used to describe resuscitation coherence. The phenomenon of resuscitation incoherence (RI) has gained great attention. However, the RI concept requires a more practical, systematic, and comprehensive framework for use in clinical practice. Moreover, we introduce a conceptual framework of RI to evaluate the interrelationship of the Macro, Micro, and cell. The RI is divided into four types (Type 1: Macro-Micro incoherence + impaired cell; Type 2: Macro-Micro incoherence + normal cell; Type 3: Micro-Cell incoherence + normal Micro; and Type 4: both Macro-Micro and Micro-cell incoherence). Furthermore, we propose the concept of dynamic circulation-perfusion coupling to evaluate the relationship of circulation and tissue perfusion during circulatory shock.

CONCLUSIONS

The concept of RI and dynamic circulation-perfusion coupling should be considered in the management of circulatory shock. Moreover, these concepts require further studies in clinical practice.

The Pannexin-1 Channel Inhibitor Probenecid Attenuates Skeletal Muscle Cellular Energy Crisis and Histopathological Injury in a Rabbit Endotoxemia Model

This study aimed to investigate the effect of probenecid (Pro) as an inhibitor of the pannexin-1 (Panx-1) channel-mediated release of intracellular ATP to the extracellular compartment on inflammation, cellular energy crisis, and organ injury in a rabbit sepsis model induced by Escherichia coli lipopolysaccharides (LPS). A total of 24 anesthetized and ventilated rabbits were randomly assigned to receive one of four treatments: infusion of LPS without Pro (LPS group), infusion of LPS with Pro (LPS + Pro group), sham operation without Pro (normal group), and sham operation with Pro (normal + Pro group). The LPS group had significantly higher serum ATP levels, serum inflammatory factor levels (TNF-α, IL-6, and IL-1β), and lower ATP concentrations and ATP/ADP ratios in the skeletal muscle tissue than the normal group. Compared to that at baseline, the expression of Panx-1 in peripheral blood cells increased significantly after the infusion of LPS (fluorescence intensity of Panx-1: T0 (baseline) vs. T1 (post-LPS) = 10 ± 1.2 vs. 84 ± 48, P < 0.0001; paired differences 73 ± 46, P = 0.024). Moreover, the LPS group exhibited higher expression of Panx-1 in the skeletal muscle tissue than the normal group. The serum ATP level was significantly positively correlated with IL-1β (R = 0.602, P = 0.001), IL-6 (R = 0.381, P = 0.033), and TNF-α (R = 0.514, P = 0.005) in 24 paired measurements. Compared to the LPS group, the LPS + Pro group had significantly lower levels of inflammatory factors (TNF-α, IL-6, and IL-1β) and serum ATP. In the skeletal muscle tissue, the LPS + Pro group also had a higher ATP concentration (1.1 ± 0.15 vs. 1.33 ± 0.17, P = 0.041) and ATP/ADP ratio (0.37 ± 0.03 vs. 0.51 ± 0.06, P = 0.002) and a lower histopathological damage score (4.67 ± 0.52 vs. 3 ± 0.63, P = 0.004). An overexpression of Panx-1 channel might be responsible for the strong inflammatory response, high serum ATP level, and skeletal muscle cellular energy crisis and histopathological damages in sepsis. Inhibiting Panx-1 channel-mediated release of intracellular ATP could decrease the above-mentioned injuries, and Panx-1 might be a potential therapeutic target in sepsis.