The prediction of fluid responsiveness

Central venous oxygen saturation changes as a reliable predictor of the change of CI in septic shock: To explore potential influencing factors

PURPOSE

Assessing fluid responsiveness relying on central venous oxygen saturation (ScvO2) yields varied outcomes across several studies. This study aimed to determine the ability of the change in ScvO2 (ΔScvO2) to detect fluid responsiveness in ventilated septic shock patients and potential influencing factors.

METHODS

In this prospective, single-center study, all patients conducted from February 2023 to January 2024 received fluid challenge. Oxygen consumption was measured by indirect calorimetry, and fluid responsiveness was defined as an increase in cardiac index (CI) ≥ 10% measured by transthoracic echocardiography. Multivariate linear regression analysis was conducted to evaluate the impact of oxygen consumption, arterial oxygen saturation, CI, and hemoglobin on ScvO2 and its change before and after fluid challenge. The Shapiro-Wilk test was used for the normality of continuous data. Data comparison between fluid responders and non-responders was conducted using a two-tailed Student t-test, Mann Whitney U test, and Chi-square test. Paired t-tests were used for normally distributed data, while the Wilcoxon signed-rank test was used for skewed data, to compare data before and after fluid challenge.

RESULTS

Among 49 patients (31 men, aged (59 ± 18) years), 27 were responders. The patients had an acute physiology and chronic health evaluation II score of 24 ± 8, a sequential organ failure assessment score of 11 ± 4, and a blood lactate level of (3.2 ± 3.1) mmol/L at enrollment. After the fluid challenge, the ΔScvO2 (mmHg) in the responders was greater than that in the non-responders (4 ± 6 vs. 1 ± 3, p = 0.019). Multivariate linear regression analysis suggested that CI was the only independent influencing factor of ScvO2, with R2 = 0.063, p = 0.008. After the fluid challenge, the change in CI became the only contributing factor to ΔScvO2 (R2 = 0.245, p < 0.001). ΔScvO2 had a good discriminatory ability for the responders and non-responders with a threshold of 4.4% (area under the curve = 0.732, p = 0.006).

CONCLUSION

ΔScvO2 served as a reliable surrogate marker for ΔCI and could be utilized to assess fluid responsiveness, given that the change in CI was the sole contributing factor to the ΔScvO2. In stable hemoglobin conditions, the absolute value of ScvO2 could serve as a monitoring indicator for adequate oxygen delivery independent of oxygen consumption.

Fluid management in the septic peri-operative patient

PURPOSE OF REVIEW

This review provides insight into recent clinical studies involving septic peri-operative patients and highlights gaps in understanding fluid management. The aim is to enhance the understanding of safe fluid resuscitation to optimize peri-operative outcomes and reduce complications.

RECENT FINDINGS

Recent research shows adverse surgical and clinical outcomes with both under- and over-hydration of peri-operative patients. The kinetic of intravenous fluids varies significantly during surgery, general anaesthesia, and sepsis with damage to endothelial glycocalyx (EG), which increases vascular permeability and interstitial oedema. Among clinical anaesthesia, neuraxial anaesthesia and sevoflurane have less effect on EG. Hypervolemia and the speed and volume of fluid infusion are also linked to EG shedding. Despite improvement in the antisepsis strategies, peri-operative sepsis is not uncommon. Fluid resuscitation is the cornerstone of sepsis management. However, overzealous fluid resuscitation is associated with increased mortality in patients with sepsis and septic shock. Personalized fluid resuscitation based on a careful assessment of intravascular volume status, dynamic haemodynamic variables and fluid tolerance appears to be a safe approach. Balanced solutions (BS) are preferred over 0.9% saline in patients with sepsis and septic shock due to a potential reduction in mortality, when exclusive BS are used and/or large volume of fluids are required for fluid resuscitation. Peri-operative goal-directed fluid therapy (GDFT) using dynamic haemodynamic variables remains an area of interest in reducing postoperative complications and can be considered for sepsis management (Supplementary Digital Content).

SUMMARY

Optimization of peri-operative fluid management is crucial for improving surgical outcomes and reducing postoperative complications in patients with sepsis. Individualized and GDFT using BS is the preferred approach for fluid resuscitation in septic peri-operative patients. Future research should evaluate the interaction between clinical anaesthesia and EG, its implications on fluid resuscitation, and the impact of GDFT in septic peri-operative patients.

Evaluation of a Physiologic-Driven Closed-Loop Resuscitation Algorithm in an Animal Model of Hemorrhagic Shock

OBJECTIVES

Appropriate resuscitation from hemorrhagic shock is critical to restore tissue perfusion and to avoid over-resuscitation. The objective of this study was to test the ability of a closed-loop diagnosis and resuscitation algorithm called resuscitation from shock using functional hemodynamic monitoring using invasive monitoring (ReFit1) and minimally invasive monitoring (ReFit2) to identify, treat, and stabilize a porcine model of severe hemorrhagic shock.

DESIGN

We created a ReFit algorithm using dynamic hemodynamic parameters of pulse pressure variation (PPV), stroke volume variation (SVV), dynamic arterial elastance (Ea dyn = PPV/SVV), driven by mean arterial pressure (MAP), mixed venous oxygen saturation, and heart rate targets to define the need for fluids, vasopressors, and inotropes.

SETTING

University-based animal laboratory.

SUBJECTS

Twenty-seven female pigs.

INTERVENTIONS

Anesthetized, intubated, and ventilated (8 mL/kg) pigs were bled at 10 mL/min until a MAP of less than 40 mm Hg, held for 30 minutes, then resuscitated. The ReFit algorithm used the above dynamic parameters to drive computer-controlled infusion pumps to deliver blood, lactated Ringer's solution, norepinephrine, and in ReFit1 dobutamine. In four animals, after initial resuscitation from hemorrhagic shock, the ability of the ReFit1 algorithm to treat acute air embolism-induced pulmonary hypertension and right heart failure was also tested.

MAIN RESULTS

In 10 ReFit1 and 17 ReFit2 animals, the time to stabilization from shock was not dissimilar to open controlled resuscitation performed by an expert physician (52 ± 12, 50 ± 13, and 60 ± 15 min, respectively) with similar amounts of fluids and norepinephrine needed. In four ReFit1 animals after initial stabilization, the algorithm successfully resuscitated the animals after inducing an acute air embolism right heart failure, with all animals recovering stability within 30 minutes.

CONCLUSIONS

Our physiologically based functional hemodynamic monitoring-centered closed-loop resuscitation system can effectively diagnose and treat cardiovascular shock due to hemorrhage and air embolism.

Assessment of the shock index in septic shock: A systematic review

OBJECTIVE

To identify published research on the Shock Index (SI) in patients with septic shock or severe sepsis and to describe its main findings and conclusions.

DESIGN

Systematic review of the literature following the recommendations of the PRISMA protocol (Preferred Reporting Items for Systematic Reviews and Meta-Analyses).

SETTINGS

The following databases were consulted: Pubmed, Embase, Library Cochrane and Lilacs.

PATIENTS

Patients older than 14 years with septic shock. Pregnant women and population with COVID-19 were excluded.

INTERVENTIONS

Studies reporting measurement of the shock index or its modified variants.

MAIN VARIABLES OF INTEREST

Absolute frequencies and relative frequencies were assessed with measures of central tendency and dispersion. Effect estimators (OR, RR and HR) were extracted according to the context of each study.

RESULTS

Seventeen articles were included, of which 11 investigated the SI as a predictor of mortality. Seven of them found significant differences in the SI when comparing survivors to non-survivors and observed a relationship between the SI evolution and clinical outcomes. Additional research evidenced a relation between the Modified Shock Index and myocardial depression, as well as mortality. Furthermore, they identified a relationship between the Diastolic Shock Index, the dose of administered dobutamine, and mortality.

CONCLUSIONS

The results suggest that both the SI and its modified versions, particularly in serial assessments, can be considered for evaluating patient prognosis. The SI can also aid in determining fluid management for patients.

Stroke volume variation induced by lung recruitment maneuver to predict fluid responsiveness in patients receiving mechanical ventilation: A systematic review and meta-analysis

STUDY OBJECTIVE

The aim of this study was to evaluate the accuracy of lung recruitment maneuver induced stroke volume variation (ΔSVLRM) in predicting fluid responsiveness in mechanically ventilated adult patients by systematic review and meta-analysis.

METHODS

A comprehensive electronic search of relevant literature was conducted in PubMed, Web of Science, Cochrane Library, Ovid Medline, Embase and Chinese databases (including China National Knowledge Infrastructure, Wanfang and VIP databases). Review Manager 5.4, Meta-DiSc 1.4 and STATA 16.0 were selected for data analysis, and QUADAS-2 tool was used for quality assessment. Data from selected studies were pooled to obtain sensitivity, specificity, diagnostic likelihood ratio (DLR) of positive and negative, diagnostic odds ratio (DOR), and summary receiver operating characteristic curve.

RESULTS

A total of 6 studies with 256 patients were enrolled through March 2024. The risk of bias and applicability concerns for each included study were low, and there was no significant publication bias. There was moderate to substantial heterogeneity for the non-threshold effect, but not for the threshold effect. The combined sensitivity and specificity were 0.84 (95% CI, 0.77-0.90) and 0.79 (95% CI, 0.70-0.86), respectively. The DOR and the area under the curve (AUC) were 22.15 (95%CI, 7.62-64.34) and 0.90 (95% CI, 0.87-0.92), respectively. The positive and negative predictive values of DLR were 4.53 (95% CI, 2.50-8.18) and 0.19 (95% CI, 0.11-0.35), respectively. Fagan's nomogram showed that with a pre-test probability of 52%, the post-test probability reached 83% and 17% for the positive and negative tests, respectively.

CONCLUSIONS

Based on the currently available evidence, ΔSVLRM has a good diagnostic value for predicting the fluid responsiveness in adult patients undergoing mechanical ventilation. Given the heterogeneity and limitations of the published data, further studies with large sample sizes and different clinical settings are needed to confirm the diagnostic value of ΔSVLRM in predicting fluid responsiveness. PROSPERO registration number: CRD42023490598.

Albumin: a comprehensive review and practical guideline for clinical use

PURPOSE

Nowadays, it is largely accepted that albumin should not be used in hypoalbuminemia or for nutritional purpose. The most discussed indication of albumin at present is the resuscitation in shock states, especially distributive shocks such as septic shock. The main evidence-based indication is also liver disease. In this review, we provided updated evidence-based instruction for definite and potential indications of albumin administration in clinical practice, with appropriate dosing and duration.

METHODS

Data collection was carried out until November 2023 by search of electronic databases including PubMed, Google Scholar, Scopus, and Web of Science. GRADE system has been used to determine the quality of evidence and strength of recommendations for each albumin indication.

RESULTS

A total of 165 relevant studies were included in this review. Fluid replacement in plasmapheresis and liver diseases, including hepatorenal syndrome, spontaneous bacterial peritonitis, and large-volume paracentesis, have a moderate to high quality of evidence and a strong recommendation for administering albumin. Moreover, albumin is used as a second-line and adjunctive to crystalloids for fluid resuscitation in hypovolemic shock, sepsis and septic shock, severe burns, toxic epidermal necrolysis, intradialytic hypotension, ovarian hyperstimulation syndrome, major surgery, non-traumatic brain injury, extracorporeal membrane oxygenation, acute respiratory distress syndrome, and severe and refractory edema with hypoalbuminemia has a low to moderate quality of evidence and weak recommendation to use. Also, in modest volume paracentesis, severe hyponatremia in cirrhosis has a low to moderate quality of evidence and a weak recommendation.

CONCLUSION

Albumin administration is most indicated in management of cirrhosis complications. Fluid resuscitation or treatment of severe and refractory edema, especially in patients with hypoalbuminemia and not responding to other treatments, is another rational use for albumin. Implementation of evidence-based guidelines in hospitals can be an effective measure to reduce inappropriate uses of albumin.

Autonomous precision resuscitation during ground and air transport of an animal hemorrhagic shock model

We tested the ability of a physiologically driven minimally invasive closed-loop algorithm, called Resuscitation based on Functional Hemodynamic Monitoring (ReFit), to stabilize for up to 3 h a porcine model of noncompressible hemorrhage induced by severe liver injury and do so during both ground and air transport. Twelve animals were resuscitated using ReFit to drive fluid and vasopressor infusion to a mean arterial pressure (MAP) > 60 mmHg and heart rate < 110 min-1 30 min after MAP < 40 mmHg following liver injury. ReFit was initially validated in 8 animals in the laboratory, then in 4 animals during air (23nm and 35nm) and ground (9 mi) to air (9.5nm and 83m) transport returning to the laboratory. The ReFit algorithm kept all animals stable for ~ 3 h. Thus, ReFit algorithm can diagnose and treat ongoing hemorrhagic shock independent to the site of care or during transport. These results have implications for treatment of critically ill patients in remote, austere and contested environments and during transport to a higher level of care.

Geo-economic Influence on the Effect of Fluid Volume for Sepsis Resuscitation: A Meta-Analysis

Rationale: Sepsis management relies on fluid resuscitation avoiding fluid overload and its related organ congestion. Objectives: To explore the influence of country income group on risk-benefit balance of fluid management strategies in sepsis. Methods: We searched e-databases for all randomized controlled trials on fluid resuscitation in patients with sepsis or septic shock up to January 2023, excluding studies on hypertonic fluids, colloids, and depletion-based interventions. The effect of fluid strategies (higher versus lower volumes) on mortality was analyzed per income group (i.e., low- and middle-income countries [LMICs] or high-income countries [HICs]). Measurements and Main Results: Twenty-nine studies (11,798 patients) were included in the meta-analysis. There was a numerically higher mortality in studies of LMICs as compared with those of HICs: median, 37% (interquartile range [IQR]: 26-41) versus 29% (IQR: 17-38; P = 0.06). Income group significantly interacted with the effect of fluid volume on mortality: Higher fluid volume was associated with higher mortality in LMICs but not in HICs: odds ratio (OR), 1.47; 95% confidence interval (95% CI): 1.14-1.90 versus 1.00 (95% CI: 0.87-1.16), P = 0.01 for subgroup differences. Higher fluid volume was associated with increased need for mechanical ventilation in LMICs (OR, 1.24 [95% CI: 1.08-1.43]) but not in HICs (OR, 1.02 [95% CI: 0.80-1.29]). Self-reported access to mechanical ventilation also significantly influenced the effect of fluid volume on mortality, which increased with higher volumes only in settings with limited access to mechanical ventilation (OR: 1.45 [95% CI: 1.09-1.93] vs. 1.09 [95% CI: 0.93-1.28], P = 0.02 for subgroup differences). Conclusions: In sepsis trials, the effect of fluid resuscitation approach differed by setting, with higher volume of fluid resuscitation associated with increased mortality in LMICs and in settings with restricted access to mechanical ventilation. The precise reason for these differences is unclear and may be attributable in part to resource constraints, participant variation between trials, or other unmeasured factors.

Coexistence of a fluid responsive state and venous congestion signals in critically ill patients: a multicenter observational proof-of-concept study

BACKGROUND

Current recommendations support guiding fluid resuscitation through the assessment of fluid responsiveness. Recently, the concept of fluid tolerance and the prevention of venous congestion (VC) have emerged as relevant aspects to be considered to avoid potentially deleterious side effects of fluid resuscitation. However, there is paucity of data on the relationship of fluid responsiveness and VC. This study aims to compare the prevalence of venous congestion in fluid responsive and fluid unresponsive critically ill patients after intensive care (ICU) admission.

METHODS

Multicenter, prospective cross-sectional observational study conducted in three medical-surgical ICUs in Chile. Consecutive mechanically ventilated patients that required vasopressors and admitted < 24 h to ICU were included between November 2022 and June 2023. Patients were assessed simultaneously for fluid responsiveness and VC at a single timepoint. Fluid responsiveness status, VC signals such as central venous pressure, estimation of left ventricular filling pressures, lung, and abdominal ultrasound congestion indexes and relevant clinical data were collected.

RESULTS

Ninety patients were included. Median age was 63 [45-71] years old, and median SOFA score was 9 [7-11]. Thirty-eight percent of the patients were fluid responsive (FR+), while 62% were fluid unresponsive (FR-). The most prevalent diagnosis was sepsis (41%) followed by respiratory failure (22%). The prevalence of at least one VC signal was not significantly different between FR+ and FR- groups (53% vs. 57%, p = 0.69), as well as the proportion of patients with 2 or 3 VC signals (15% vs. 21%, p = 0.4). We found no association between fluid balance, CRT status, or diagnostic group and the presence of VC signals.

CONCLUSIONS

Venous congestion signals were prevalent in both fluid responsive and unresponsive critically ill patients. The presence of venous congestion was not associated with fluid balance or diagnostic group. Further studies should assess the clinical relevance of these results and their potential impact on resuscitation and monitoring practices.

Meaning and Management of Perioperative Oliguria

Perioperative oliguria is an alarm signal. The initial assessment includes closer patient monitoring, evaluation of volemic status, risk-benefit of fluid challenge or furosemide stress test, and investigation of possible perioperative complications.

Perioperative Fluid Management in Colorectal Surgery: Institutional Approach to Standardized Practice

The present review discusses restrictive perioperative fluid protocols within enhanced recovery after surgery (ERAS) pathways. Standardized definitions of a restrictive or liberal fluid regimen are lacking since they depend on conflicting evidence, institutional protocols, and personal preferences. Challenges related to restrictive fluid protocols are related to proper patient selection within standardized ERAS protocols. On the other hand, invasive goal-directed fluid therapy (GDFT) is reserved for more challenging disease presentations and polymorbid and frail patients. While the perfusion rate (mL/kg/h) appears less predictive for postoperative outcomes, the authors identified critical thresholds related to total intravenous fluids and weight gain. These thresholds are discussed within the available evidence. The authors aim to introduce their institutional approach to standardized practice.

The effect of passive leg raising test on intracranial pressure and cerebral autoregulation in brain injured patients: a physiological observational study

BACKGROUND

The use of the passive leg raising (PLR) is limited in acute brain injury (ABI) patients with increased intracranial pressure (ICP) since the postural change of the head may impact on ICP and cerebral autoregulation. However, the PLR use may prevent a positive daily fluid balance, which had been recently associated to worse neurological outcomes. We therefore studied early and delayed effects of PLR on the cerebral autoregulation of patients recovering from ABI.

MATERIALS AND METHODS

This is a Prospective, observational, single-center study conducted in critically ill patients admitted with stable ABI and receiving invasive ICP monitoring, multimodal neuromonitoring and continuous hemodynamic monitoring. The fluid challenge consisted of 500 mL of crystalloid over 10 min; fluid responsiveness was defined as cardiac index increase ≥ 10%. Comparisons between different variables at baseline and after PLR were made by paired Wilcoxon signed-rank test. The correlation coefficients between hemodynamic and neuromonitoring variables were assessed using Spearman's rank test.

RESULTS

We studied 23 patients [12 patients (52.2%) were fluid responders]. The PLR significantly increased ICP [from 13.7 (8.3-16.4) to 15.4 (12.0-19.2) mmHg; p < 0.001], cerebral perfusion pressure (CPP) [from 51.1 (47.4-55.6) to 56.4 (49.6-61.5) mmHg; p < 0.001] and the pressure reactivity index (PRx) [from 0.12 (0.01-0.24) to 0.43 (0.34-0.46) mmHg; p < 0.001]. Regarding Near Infrared Spectroscopy (NIRS)-derived parameters, PLR significantly increased the arterial component of regional cerebral oxygen saturation (O2Hbi) [from 1.8 (0.8-3.7) to 4.3 (2.5-5.6) μM cm; p < 0.001], the deoxygenated hemoglobin (HHbi) [from 1.6 (0.2-2.9) to 2.7 (1.4-4.0) μM cm; p = 0.007] and total hemoglobin (cHbi) [from 3.6 (1.9-5.3) to 7.8 (5.2-10.3): p < 0.001]. In all the patients who had altered autoregulation after PLR, these changes persisted ten minutes afterwards. After the PLR, we observed a significant correlation between MAP and CPP and PRx.

CONCLUSIONS

In ABI patient with stable ICP, PLR test increased ICP, but mostly within safety values and thresholds. Despite this, cerebral autoregulation was importantly impaired, and this persisted up to 10 min after the end of the maneuvre. Our results discourage the use of PLR test in ABI even when ICP is stable.

The Ins and Outs of IV Fluids in Hemodynamic Resuscitation

OBJECTIVES

Concise definitive review of the physiology of IV fluid (IVF) use in critically ill patients.

DATA SOURCES

Available literature on PubMed and MEDLINE databases.

STUDY SELECTION

Basic physiology studies, observational studies, clinical trials, and reviews addressing the physiology of IVF and their use in the critically ill were included.

DATA EXTRACTION

None.

DATA SYNTHESIS

We combine clinical and physiologic studies to form a framework for understanding rational and science-based use of fluids and electrolytes.

CONCLUSIONS

IVF administration is among the most common interventions for critically ill patients. IVF can be classified as crystalloids or colloids, and most crystalloids are sodium salts. They are frequently used to improve hemodynamics during shock states. Many recent clinical trials have sought to understand which kind of IVF might lead to better patient outcomes, especially in sepsis. Rational use of IVF rests on understanding the physiology of the shock state and what to expect IVF will act in those settings. Many questions remain unanswered, and future research should include a physiologic understanding of IVF in study design.

Supine transfer test-induced changes in cardiac index predict fluid responsiveness in patients without intra-abdominal hypertension

BACKGROUND

The reversible maneuver that mimics the fluid challenge is a widely used test for evaluating volume responsiveness. However, passive leg raising (PLR) does have certain limitations. The aim of the study is to determine whether the supine transfer test could predict fluid responsiveness in adult patients with acute circulatory failure who do not have intra-abdominal hypertension, by measuring changes in cardiac index (CI).

METHODS

Single-center, prospective clinical study in a 25-bed surgery intensive care unit at the Fudan University Shanghai Cancer Center. Thirty-four patients who presented with acute circulatory failure and were scheduled for fluid therapy. Every patient underwent supine transfer test and fluid challenge with 500 mL saline for 15-30 min. There were four sequential steps in the protocol: (1) baseline-1: a semi-recumbent position with the head of the bed raised to 45°; (2) supine transfer test: patients were transferred from the 45° semi-recumbent position to the strict supine position; (3) baseline-2: return to baseline-1 position; and (4) fluid challenge: administration of 500 mL saline for 15-30 min. Hemodynamic parameters were recorded at each step with arterial pulse contour analysis (ProAQT/Pulsioflex). A fluid responder was defined as an increase in CI ≥ 15% after fluid challenge. The receiver operating characteristic curve and gray zone were defined for CI.

RESULTS

Seventeen patients were fluid challenge. The r value of the linear correlations was 0.73 between the supine transfer test- and fluid challenge-induced relative CI changes. The relative changes in CI induced by supine transfer in predicting fluid responsiveness had an area under the receiver operating characteristic curve of 0.88 (95% confidence interval 0.72-0.97) and predicted a fluid responder with 76.5% (95% confidence interval 50.1-93.2) sensitivity and 88.2% (95% confidence interval 63.6-98.5) specificity, at a best threshold of 5.5%. Nineteen (55%) patients were in the gray zone (CI ranging from -3 and 8 L/min/m2).

CONCLUSION

The supine transfer test can potentially assist in detecting fluid responsiveness in patients with acute circulatory failure without intra-abdominal hypertension. Nevertheless, the small threshold and the 55% gray zone were noteworthy limitation.

TRIAL REGISTRATION

Predicting fluid responsiveness with supine transition test (ChiCTR2200058264). Registered 2022-04-04 and last refreshed on 2023-03-26, https://www.chictr.org.cn/showproj.html?proj=166175 .

Fluid management strategies and their interaction with mechanical ventilation: from experimental studies to clinical practice

Patients on mechanical ventilation may receive intravenous fluids via restrictive or liberal fluid management. A clear and objective differentiation between restrictive and liberal fluid management strategies is lacking in the literature. The liberal approach has been described as involving fluid rates ranging from 1.2 to 12 times higher than the restrictive approach. A restrictive fluid management may lead to hypoperfusion and distal organ damage, and a liberal fluid strategy may result in endothelial shear stress and glycocalyx damage, cardiovascular complications, lung edema, and distal organ dysfunction. The association between fluid and mechanical ventilation strategies and how they interact toward ventilator-induced lung injury (VILI) could potentiate the damage. For instance, the combination of a liberal fluids and pressure-support ventilation, but not pressure control ventilation, may lead to further lung damage in experimental models of acute lung injury. Moreover, under liberal fluid management, the application of high positive end-expiratory pressure (PEEP) or an abrupt decrease in PEEP yielded higher endothelial cell damage in the lungs. Nevertheless, the translational aspects of these findings are scarce. The aim of this narrative review is to provide better understanding of the interaction between different fluid and ventilation strategies and how these interactions may affect lung and distal organs. The weaning phase of mechanical ventilation and the deresuscitation phase are not explored in this review.

Variation in central venous oxygen saturation to evaluate fluid responsiveness: a systematic review and meta-analysis

BACKGROUND

Since oxygen content and oxygen consumption typically remain unchanged within a short period, variation in central venous oxygen saturation (ΔScvO₂) during fluid challenge can theoretically track the changes in cardiac output (CO). We conducted this meta-analysis to systematically assess the diagnostic performance of ΔScvO₂ during a fluid challenge for fluid responsiveness in mechanically ventilated patients receiving volume expansion.

METHODS

Electronic databases were systematically searched to identify relevant studies published before October 24, 2022. As the cutoff value of ΔScvO₂ was expected to vary across the included studies, we estimated the area under the hierarchical summary receiver operating characteristic curve (AUHSROC) as the primary measure of diagnostic accuracy. The optimal threshold of ΔScvO₂ and the corresponding 95% confidential interval (CI) were also estimated.

RESULTS

This meta-analysis included 5 observational studies comprising 240 participants, of whom 133 (55%) were fluid responders. Overall, the ΔScvO₂ during the fluid challenge exhibited excellent performance for defining fluid responsiveness in mechanically ventilated patients receiving volume expansion, with an AUHSROC of 0.86 (95% CI 0.83-0.89), a pooled sensitivity of 0.78 (95% CI 0.69-0.85), a pooled specificity of 0.84 (95% CI 0.72-0.91), and a pooled diagnostic odds ratio of 17.7 (95% CI 5.9-53.2). The distribution of the cutoff values was nearly conically symmetrical and concentered between 3 and 5%; the mean and median cutoff values were 4% (95% CI 3-5%) and 4% (95% CI not estimable), respectively.

CONCLUSIONS

In mechanically ventilated patients receiving volume expansion, the ΔScvO2 during the fluid challenge is a reliable indicator of fluid responsiveness. Clinical trial registration PROSPERO, https://www.crd.york.ac.uk/prospero/ , registry number: CRD42022370192.