Krisztián Tánczos

Central venous oxygen saturation and carbon dioxide gap as resuscitation targets in a hemorrhagic shock

Fluid resuscitation is still a major challenge. We aimed to describe changes in central venous oxygen saturation (ScvO2) and venous‐to‐arterial carbon dioxide gap (dCO2) during an experimental stroke volume (SV) index (SVI)‐guided hemorrhage and fluid resuscitation model in pigs.

The multimodal concept of hemodynamic stabilization

Hemodynamic instability often leads to hypoperfusion, which has a significant impact on outcome in both medical and surgical patients. Measures to detect and treat tissue hypoperfusion early by correcting the imbalance between oxygen delivery and consumption is of particular importance. There are several studies targeting different hemodynamic endpoints in order to investigate the effects of goal-directed therapy on outcome. A so-called multimodal concept putting several variables in context follows simple logic and may provide a broader picture. Furthermore, rather than treating population based “normal” values of certain indices, this concept can be translated into the individualized patient care to reach adequate oxygen supply and tissue oxygenation in order to avoid under, or over resuscitation, which are equally harmful. The purpose of this review is to give an overview of current data providing the basis of this a multimodal, individualized approach of hemodynamic monitoring and treatment.

Early procalcitonin kinetics and appropriateness of empirical antimicrobial therapy in critically ill patients: A prospective observational study.

PURPOSE The purpose was to investigate the value of procalcitonin (PCT) kinetics in predicting the appropriateness of empirical antimicrobial treatment in critically ill patients. MATERIALS AND METHODS This prospective observational study recruited patients in whom empirical antimicrobial therapy was started for suspected infection. Biochemical and physiological parameters were measured before initiating antimicrobials (t0), 8 hourly (t8, t16, t24), and then daily (day2-6). Patients were grouped post hoc into appropriate (A) and inappropriate (IA) groups. RESULTS Of 209 patients, infection was confirmed in 67%. Procalcitonin kinetics were different between the IA (n = 33) and A groups (n = 108). In the IA group, PCT levels (median [interquartile range]) increased: t0= 2.8 (1.2-7.4), t16= 8.6 (4.8-22.1), t24= 14.5 (4.9-36.1), P< .05. In the A group, PCT peaked at t16 and started to decrease by t24: t0= 4.2 (1.9-12.8), t16= 6.99 (3.4-29.1), t24= 5.2 (2.0-16.7), P< .05. Receiver operating characteristic analysis revealed that a PCT elevation greater than or equal to 69% from t0 to t16 had an area under the curve for predicting inappropriate antimicrobial treatment of 0.73 (95% confidence interval, 0.63-0.83), P< .001; from t0 to t24, a greater than or equal to 74% increase had an area under the curve of 0.86 (0.77-0.94), P< .001. Hospital mortality was 37% in the A group and 61% in the IA group (P= .017). CONCLUSIONS Early response of PCT in the first 24 hours of commencing empirical antimicrobials in critically ill patients may help the clinician to evaluate the appropriateness of therapy.

Delta Procalcitonin Is a Better Indicator of Infection Than Absolute Procalcitonin Values in Critically Ill Patients: A Prospective Observational Study

Purpose. To investigate whether absolute value of procalcitonin (PCT) or the change (delta-PCT) is better indicator of infection in intensive care patients. Materials and Methods. Post hoc analysis of a prospective observational study. Patients with suspected new-onset infection were included in whom PCT, C-reactive protein (CRP), temperature, and leukocyte (WBC) values were measured on inclusion (t 0) and data were also available from the previous day (t −1). Based on clinical and microbiological data, patients were grouped post hoc into infection- (I-) and noninfection- (NI-) groups. Results. Of the 114 patients, 85 (75%) had proven infection. PCT levels were similar at t −1: I-group (median [interquartile range]): 1.04 [0.40–3.57] versus NI-group: 0.53 [0.16–1.68], p = 0.444. By t 0 PCT levels were significantly higher in the I-group: 4.62 [1.91–12.62] versus 1.12 [0.30–1.66], p = 0.018. The area under the curve to predict infection for absolute values of PCT was 0.64 [95% CI = 0.52–0.76], p = 0.022; for percentage change: 0.77 [0.66–0.87], p < 0.001; and for delta-PCT: 0.85 [0.78–0.92], p < 0.001. The optimal cut-off value for delta-PCT to indicate infection was 0.76 ng/mL (sensitivity 80 [70–88]%, specificity 86 [68-96]%). Neither absolute values nor changes in CRP, temperature, or WBC could predict infection. Conclusions. Our results suggest that delta-PCT values are superior to absolute values in indicating infection in intensive care patients. This trial is registered with ClinicalTrials.gov identifier: NCT02311816.

The oxygen supply-demand balance: A monitoring challenge

The principal task of acute critical care is to avoid or correct oxygen debt by increasing oxygen delivery (DO2) and/or decreasing oxygen consumption (VO2). The most commonly used methods to assess the relationship of adequate delivery and consumption are mixed venous oxygen saturation and its surrogate, central venous oxygen saturation (ScvO2). The purpose of this article is to review the values and limitations of the two parameters and evaluate the clinical use of ScvO2 in certain clinical scenarios, such as anaemia and transfusion, hypovolaemia, major surgery, septic shock, and in difficult-to-wean patients.

Goal-Directed Resuscitation Aiming Cardiac Index Masks Residual Hypovolemia: An Animal Experiment

The aim of this study was to compare stroke volume (SVI) to cardiac index (CI) guided resuscitation in a bleeding-resuscitation experiment. Twenty six pigs were randomized and bled in both groups till baseline SVI (T bsl) dropped by 50% (T 0), followed by resuscitation with crystalloid solution until initial SVI or CI was reached (T 4). Similar amount of blood was shed but animals received significantly less fluid in the CI-group as in the SVI-group: median = 900 (interquartile range: 850–1780) versus 1965 (1584–2165) mL, p = 0.02, respectively. In the SVI-group all variables returned to their baseline values, but in the CI-group animals remained underresuscitated as indicated by SVI, heart rate (HR) and stroke volume variation (SVV), and central venous oxygen saturation (ScvO2) at T 4 as compared to T bsl: SVI = 23.8 ± 5.9 versus 31.4 ± 4.7 mL, HR: 117 ± 35 versus 89 ± 11/min SVV: 17.4 ± 7.6 versus 11.5 ± 5.3%, and ScvO2: 64.1 ± 11.6 versus 79.2 ± 8.1%, p < 0.05, respectively. Our results indicate that CI-based goal-directed resuscitation may result in residual hypovolaemia, as bleeding caused stress induced tachycardia “normalizes” CI, without restoring adequate SVI. As the SVI-guided approach normalized most hemodynamic variables, we recommend using SVI instead of CI as the primary goal of resuscitation during acute bleeding.

Mean arterial pressure targeted fluid resuscitation may lead to fluid overload: A bleeding-resuscitation animal experiment

Introduction Fluid resuscitation is the cornerstone of treatment in hemorrhagic shock. Despite increasing doubts, several guidelines recommend to maintain mean arterial pressure (MAP) >65 mmHg as the most frequent indication of fluid therapy. Our aim was to investigate the effects of a MAP-guided management in a bleeding-resuscitation animal experiment. Materials and methods After anesthesia and instrumentation (tbsl) animals were bled till the initial stroke volume index dropped by 50% (t0). Fluid replacement was performed in 4 equivalent steps (t1-4) with balanced crystalloid solution to reach the baseline values of MAP. Invasive hemodynamic measurements and blood gas analyses were performed after each step. Results Mean arterial pressure dropped from tbsl to t0 (114±11 vs 76.9±16.9 mmHg, p<0.001) and returned to baseline by t4 (101.4±14.4 mmHg). From tbsl-t0 stroke volume index (SVI), cardiac index (CI) decreased (SVI: 40±8.6 vs 19.3±3.6 ml/m2, p<0.001; CI: 3.4±0.3 vs 1.9±0.3 l/min/m2, p<0.001), pulse pressure variation (PPV) increased (13.2±4.3 vs 22.1±4.3%, p<0.001). There was a decrease in oxygen delivery (464±45 vs 246±26.9 ml/min, p<0.001), central venous oxygen saturation (82.8±5.4 vs 53.6±12.1%, p<0.001) and increase in lactate levels (1.6±0.4 vs 3.5±1.6 mmol/l, p<0.005). SVI, CI and PPV returned to their initial values by t2. To normalize MAP fluid therapy had to be continued till t4, with the total infused volume of 4.5±0.8 l. Conclusion In the current experiment bleeding led to hemorrhagic shock, while MAP remained higher than 65 mmHg. Furthermore, MAP was unable to indicate the normalization of SVI, CI and PPV that resulted in unnecessary fluid administration. Our data give further evidence that MAP may be an inappropriate parameter to follow during fluid resuscitation.

Volume-replacement ratio for crystalloids and colloids during bleeding and resuscitation: an animal experiment

BackgroundFluid resuscitation remains a cornerstone in the management of acute bleeding. According to Starlings “Three-compartment model”, four-times more crystalloids have the same volume effect as colloids. However, this volume-replacement ratio remains a controversial issue as it may be affected by the degradation of the endothelial glycocalyx layer, a situation often found in the critically ill. Our aim was to compare colloid and crystalloid based fluid resuscitation during an experimental stroke volume index (SVI) guided hemorrhage and resuscitation animal model.MethodsAnesthetized and mechanically ventilated pigs were randomized to receive a colloid (Voluven®,HES, n=15) or crystalloid (Ringerfundin®,RF, n=15) infusion. Animals were bled till baseline SVI (Tbsl) dropped by 50% (T0), followed by resuscitation until initial SVI was reached (T4) in four steps. Invasive hemodynamic measurements, blood gas analyses and laboratory tests were performed at each assessment points. Glycocalyx degradation markers (Syndecan-1/hematocrit ratio, Glypican/hematocrit ratio) were determined at Tbsl, T0 and T4.ResultsSimilar amounts of blood were shed in both groups (HES group: 506±159 mls blood, RF group: 470±127 mls blood). Hemodynamic changes followed the same pattern without significant difference between the groups. Animals received significantly less resuscitation fluid in the HES compared to the RF-group: 425 [320-665], vs 1390 [884-1585] mls, p <0.001. The volume replacement ratio was 0.92 [0.79-1.54] for HES; and 3.03 [2.00-4.23] for the RF-group (p <0.001). There was no significant difference between the groups in the glycocalyx degradation markers.ConclusionIn this moderate bleeding-resuscitation animal model the volume-replacement ratio for crystalloids and colloids followed similar patterns as predicted by Starlings principle, and the glycocalyx remained intact. This indicates that in acute bleeding events, such as trauma or during surgery, colloids may be beneficial as hemodynamic stability may be achieved more rapidly than with crystalloids.

ScvO 2 as an Alternative Transfusion Trigger

Blood transfusion is often a life-saving but risky intervention. Restrictive transfusion protocols have recently been developed with a post-transfusion target haemoglobin level of 7–10 g/dL. Whether only haemoglobin level is enough to guide our transfusion practice is questionable; hence, the same level of anaemia may be harmless in sedated, haemodynamically stable patients, while it requires urgent treatment in unstable patients or when oxygen demand is increased. Therefore, it is not the haemoglobin level per se that determines the severity of anaemia but the imbalance between oxygen delivery and consumption. One of the simple surrogates to estimate the balance of the oxygen extraction ratio is central venous oxygen saturation. In this chapter, the role of central venous oxygen saturation as an alternative transfusion trigger in addition to haemoglobin will be discussed.

The Hemodynamic Puzzle: Solving the Impossible?

Development of multiorgan dysfunction is often the result of hypoperfusion, which severely affects outcomes of medical and surgical patients and substantially increases the utilization of resources and costs [1]. Therefore, the use of early and efficient strategies to detect tissue hypoperfusion and to treat the imbalance between oxygen consumption and delivery is of particular importance [2]. Traditional endpoints, such as heart rate, blood pressure, mental status and urine output, can be useful in the initial identification of inadequate perfusion, but are limited in their ability to identify ongoing, compensated shock [3]. Therefore, more detailed assessment of global macrohemodynamic indices, such as cardiac output and derived variables and measures of oxygen delivery and uptake, may be necessary to guide treatment [4–5]. Furthermore, after optimization of these parameters, indicators of tissue perfusion should also be assessed to verify the effectiveness of therapy [6]. This multimodal approach can be translated into the individualized use of target endpoints for hemodynamic stabilization instead of treating ‘normal’ values, and can help to achieve adequate oxygen supply and tissue oxygenation in order to avoid under- or over-resuscitation, which are equally harmful.