Márton Németh

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.

Multimodal individualized concept of hemodynamic monitoring.

Purpose of review To discuss the pathophysiological rationale of advanced hemodynamic monitoring in the critically ill and also to highlight the importance of a multimodal, individualized approach. Recent findings There are several clinical studies and animal experiments evaluating, which hemodynamic endpoint should be the best target during fluid management. Recent systematic reviews and meta-analyses also investigated the effects of advanced hemodynamic endpoints targeted hemodynamic management on outcome mainly in high-risk surgical patients. Although most of these studies report positive results, this knowledge does not seem to affect our everyday practice. According to large international surveys, most physicians still rely on inappropriate indices. One of the reasons could be that target values applied in these studies can be misleading in the individual patient. Therefore, we describe the concept of an individualized approach, in which normalizing the components of oxygen delivery are put in the context of the patients’ individual response by evaluating components of oxygen consumption, and organ perfusion. Summary Advanced hemodynamic monitoring-based management provides a number of benefits, which could be better tailored for the patients’ actual needs by putting this into a multimodal, individualized approach.

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.

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.

Lung Recruitment Can Improve Oxygenation in Patients Ventilated in Continuous Positive Airway Pressure/Pressure Support Mode

Background Recruitment maneuvers are often used in critical care patients with hypoxemic respiratory failure. Although continuous positive airway pressure/pressure support (CPAP/PS) ventilation is a frequently used approach, but whether lung recruitment also improves oxygenation in spontaneously breathing patients has not been investigated yet. The primary objective was to analyze the effect of recruitment maneuver on oxygenation in patients ventilated in CPAP/PS mode. Methods Following baseline measurements PEEP was increased by 5 cmH2O. Recruitment maneuver was applied for 40 s with 40 cmH2O of PS. Measurements of the difference in PaO2/FiO2 and airway parameters measured by the ventilator were recorded immediately after recruitment then 15 and 30 min later. Thirty patients ventilated in CPAP/PS mode with a PEEP ≥5 cmH2O were enrolled in this prospective, observational study if their PaO2/FiO2 ratio was <300 mmHg or required an FiO2 >0.5. Results Following recruitment maneuver patients were considered as non-responders (NR, n = 15) if difference of PaO2/FiO2 <20% and responders (R, n = 15) if difference of PaO2/FiO2 ≥20%. In the NR-group, PaO2/FiO2 decreased non-significantly from baseline: median [interquartile], PaO2/FiO2 = 176 [120–186] vs. after recruitment: 169 [121–182] mmHg, P = 0.307 while in the R-group there was significant improvement: 139 [117–164] vs. 230 [211–323] mmHg, P = 0.01. At the same time points, dead space to tidal volume ratio (Vds/Vte) significantly increased in the NR-group Vds/Vte = 32 [27–37] vs. 36 [25–42]%, P = 0.013 but no significant change was observed in the R-group: 26 [22–34] vs. 27 [24–33]%, P = 0.386. Conclusion Recruitment maneuver improved PaO2/FiO2 ratio by ≥20% in 50% of patients ventilated in CPAP/PS mode.

Monitoring Microcirculatory Blood Flow with a New Sublingual Tonometer in a Porcine Model of Hemorrhagic Shock

Tissue capnometry may be suitable for the indirect evaluation of regional hypoperfusion. We tested the performance of a new sublingual capillary tonometer in experimental hemorrhage. Thirty-six anesthetized, ventilated mini pigs were divided into sham-operated (n = 9) and shock groups (n = 27). Hemorrhagic shock was induced by reducing mean arterial pressure (MAP) to 40 mmHg for 60 min, after which fluid resuscitation started aiming to increase MAP to 75% of the baseline value (60–180 min). Sublingual carbon-dioxide partial pressure was measured by tonometry, using a specially coiled silicone rubber tube. Mucosal red blood cell velocity (RBCV) and capillary perfusion rate (CPR) were assessed by orthogonal polarization spectral (OPS) imaging. In the 60 min shock phase a significant drop in cardiac index was accompanied by reduction in sublingual RBCV and CPR and significant increase in the sublingual mucosal-to-arterial PCO2 gap (PSLCO2 gap), which significantly improved during the 120 min resuscitation phase. There was significant correlation between PSLCO2 gap and sublingual RBCV (r = −0.65, p < 0.0001), CPR (r = −0.64, p < 0.0001), central venous oxygen saturation (r = −0.50, p < 0.0001), and central venous-to-arterial PCO2 difference (r = 0.62, p < 0.0001). This new sublingual tonometer may be an appropriate tool for the indirect evaluation of circulatory changes in shock.

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.

Monitoring of Tissue Oxygenation: an Everyday Clinical Challenge

Purpose of review The aim of this article is to study the overview of pathophysiology and clinical application of central venous oxygen saturation monitoring in critically ill patients and during the perioperative period. Recent findings There are several clinical studies and animal experiments evaluating the effects of goal-directed hemodynamic stabilization on critically ill patients. Recent systematic reviews and meta-analyses found that advanced hemodynamic endpoints-targeted management has a positive effect on outcome in high-risk surgical patients. As all interventions aim to improve tissue oxygenation, it is of utmost importance to monitor the balance between oxygen delivery and consumption. For this purpose, central venous blood gas analysis provides an easily available tool in the everyday clinical practice. The adequate interpretation of central venous oxygen saturation renders the need of careful evaluation of several physiological and pathophysiological circumstances. When appropriately evaluated, central venous oxygen saturation can be a valuable component of a multimodal individualized approach, in which components of oxygen delivery are put in the context of the patients’ individual oxygen consumption. In addition to guide therapy, central venous oxygen saturation may also serve as an early warning sign of inadequate oxygen delivery, which would otherwise remain hidden from the attending physician. Summary With the incorporation of central venous oxygen saturation in the everyday clinical routine, treatment could be better tailored for the patients’ actual needs; hence, it may also improve outcome.