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      Central venous O 2 saturation and venous-to-arterial CO 2 difference as complementary tools for goal-directed therapy during high-risk surgery

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          Abstract

          Introduction

          Central venous oxygen saturation (ScvO 2) is a useful therapeutic target in septic shock and high-risk surgery. We tested the hypothesis that central venous-to-arterial carbon dioxide difference (P(cv-a)CO 2), a global index of tissue perfusion, could be used as a complementary tool to ScvO 2 for goal-directed fluid therapy (GDT) to identify persistent low flow after optimization of preload has been achieved by fluid loading during high-risk surgery.

          Methods

          This is a secondary analysis of results obtained in a study involving 70 adult patients (ASA I to III), undergoing major abdominal surgery, and treated with an individualized goal-directed fluid replacement therapy. All patients were managed to maintain a respiratory variation in peak aortic flow velocity below 13%. Cardiac index (CI), oxygen delivery index (DO 2i), ScvO 2, P(cv-a)CO 2 and postoperative complications were recorded blindly for all patients.

          Results

          A total of 34% of patients developed postoperative complications. At baseline, there was no difference in demographic or haemodynamic variables between patients who developed complications and those who did not. In patients with complications, during surgery, both mean ScvO 2 (78 ± 4 versus 81 ± 4%, P = 0.017) and minimal ScvO 2 (minScvO 2) (67 ± 6 versus 72 ± 6%, P = 0.0017) were lower than in patients without complications, despite perfusion of similar volumes of fluids and comparable CI and DO 2i values. The optimal ScvO 2 cut-off value was 70.6% and minScvO 2 < 70% was independently associated with the development of postoperative complications (OR = 4.2 (95% CI: 1.1 to 14.4), P = 0.025). P(cv-a)CO 2 was larger in patients with complications (7.8 ± 2 versus 5.6 ± 2 mmHg, P < 10 -6). In patients with complications and ScvO 2 ≥71%, P(cv-a)CO 2 was also significantly larger (7.7 ± 2 versus 5.5 ± 2 mmHg, P < 10 -6) than in patients without complications. The area under the receiver operating characteristic (ROC) curve was 0.785 (95% CI: 0.74 to 0.83) for discrimination of patients with ScvO 2 ≥71% who did and did not develop complications, with 5 mmHg as the most predictive threshold value.

          Conclusions

          ScvO 2 reflects important changes in O 2 delivery in relation to O 2 needs during the perioperative period. A P(cv-a)CO 2 < 5 mmHg might serve as a complementary target to ScvO 2 during GDT to identify persistent inadequacy of the circulatory response in face of metabolic requirements when an ScvO 2 ≥71% is achieved.

          Trial registration

          Clinicaltrials.gov Identifier: NCT00852449.

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          Most cited references27

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          Lactate clearance vs central venous oxygen saturation as goals of early sepsis therapy: a randomized clinical trial.

          Goal-directed resuscitation for severe sepsis and septic shock has been reported to reduce mortality when applied in the emergency department. To test the hypothesis of noninferiority between lactate clearance and central venous oxygen saturation (ScvO2) as goals of early sepsis resuscitation. Multicenter randomized, noninferiority trial involving patients with severe sepsis and evidence of hypoperfusion or septic shock who were admitted to the emergency department from January 2007 to January 2009 at 1 of 3 participating US urban hospitals. We randomly assigned patients to 1 of 2 resuscitation protocols. The ScvO2 group was resuscitated to normalize central venous pressure, mean arterial pressure, and ScvO2 of at least 70%; and the lactate clearance group was resuscitated to normalize central venous pressure, mean arterial pressure, and lactate clearance of at least 10%. The study protocol was continued until all goals were achieved or for up to 6 hours. Clinicians who subsequently assumed the care of the patients were blinded to the treatment assignment. The primary outcome was absolute in-hospital mortality rate; the noninferiority threshold was set at Delta equal to -10%. Of the 300 patients enrolled, 150 were assigned to each group and patients were well matched by demographic, comorbidities, and physiological features. There were no differences in treatments administered during the initial 72 hours of hospitalization. Thirty-four patients (23%) in the ScvO2 group died while in the hospital (95% confidence interval [CI], 17%-30%) compared with 25 (17%; 95% CI, 11%-24%) in the lactate clearance group. This observed difference between mortality rates did not reach the predefined -10% threshold (intent-to-treat analysis: 95% CI for the 6% difference, -3% to 15%). There were no differences in treatment-related adverse events between the groups. Among patients with septic shock who were treated to normalize central venous and mean arterial pressure, additional management to normalize lactate clearance compared with management to normalize ScvO2 did not result in significantly different in-hospital mortality. clinicaltrials.gov Identifier: NCT00372502.
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            Goal-directed fluid management based on pulse pressure variation monitoring during high-risk surgery: a pilot randomized controlled trial

            Introduction Several studies have shown that maximizing stroke volume (or increasing it until a plateau is reached) by volume loading during high-risk surgery may improve post-operative outcome. This goal could be achieved simply by minimizing the variation in arterial pulse pressure (ΔPP) induced by mechanical ventilation. We tested this hypothesis in a prospective, randomized, single-centre study. The primary endpoint was the length of postoperative stay in hospital. Methods Thirty-three patients undergoing high-risk surgery were randomized either to a control group (group C, n = 16) or to an intervention group (group I, n = 17). In group I, ΔPP was continuously monitored during surgery by a multiparameter bedside monitor and minimized to 10% or less by volume loading. Results Both groups were comparable in terms of demographic data, American Society of Anesthesiology score, type, and duration of surgery. During surgery, group I received more fluid than group C (4,618 ± 1,557 versus 1,694 ± 705 ml (mean ± SD), P < 0.0001), and ΔPP decreased from 22 ± 75 to 9 ± 1% (P < 0.05) in group I. The median duration of postoperative stay in hospital (7 versus 17 days, P < 0.01) was lower in group I than in group C. The number of postoperative complications per patient (1.4 ± 2.1 versus 3.9 ± 2.8, P < 0.05), as well as the median duration of mechanical ventilation (1 versus 5 days, P < 0.05) and stay in the intensive care unit (3 versus 9 days, P < 0.01) was also lower in group I. Conclusion Monitoring and minimizing ΔPP by volume loading during high-risk surgery improves postoperative outcome and decreases the length of stay in hospital. Trial registration NCT00479011
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              Combination of venoarterial PCO2 difference with arteriovenous O2 content difference to detect anaerobic metabolism in patients.

              Under conditions of tissue hypoxia total CO2 production (VCO2) should be less reduced than O2 consumption (VO2) since an anaerobic CO2 production should occur. Thus the VCO(2)/VO(2) ratio, and hence the venoarterial CO2 tension difference/arteriovenous O2 content difference ratio (DeltaPCO2/C(a-v)O2), should increase. We tested the value of the DeltaPCO2/C(a-v)O2 ratio in detecting the presence of global anaerobic metabolism as defined by an increase in arterial lactate level above 2 mmol/l (Lac+). Retrospective study over a 17-month period in medical intensive care unit of a university hospital. We obtained 148 sets of measurements in 89 critically ill patients monitored by a pulmonary artery catheter. The DeltaPCO2/C(a-v)O2 ratio was higher in those with increased ( n=73) than in the normolactatemic group (2.0+/-0.9 vs. 1.1+/-0.6, p<0.0001). Among all the O2- and CO2-derived parameters the DeltaPCO2/C(a-v)O2 ratio had the highest correlation with the arterial lactate level ( r=0.57). Moreover, for a threshold value of 1.4 the DeltaPCO2/C(a-v)O2 ratio predicted significantly better than the other parameters (receiver operating characteristic curves) the presence of hyperlactatemia (positive and negative predictive values of 86% and 80%, respectively). The overall survival estimate at 1 month was greater when the DeltaPCO2/C(a-v)O2 ratio was less than 1.4 on the first set of measurements (38+/-10% vs. 20+/-8%, p<0.01). The DeltaPCO2/C(a-v)O2 ratio seems a reliable marker of global anaerobic metabolism. Its calculation would be helpful for a better interpretation of pulmonary artery catheter data.
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                Author and article information

                Journal
                Crit Care
                Critical Care
                BioMed Central
                1364-8535
                1466-609X
                2010
                29 October 2010
                : 14
                : 5
                : R193
                Affiliations
                [1 ]Department of Anaesthesiology and Critical Care Medicine, Estaing Hospital, University Hospital of Clermont-Ferrand, 1 Place Lucie Aubrac, Clermont-Ferrand, 63000, France
                [2 ]Federation of Anaesthesiology and Critical Care Medicine, University Hospital of Lille, Univ Nord de France, Rue du Pr. Emile Laine, Lille, 59037, France
                Article
                cc9310
                10.1186/cc9310
                3219300
                21034476
                6d0a8644-1eae-457a-a9c5-730768432c13
                Copyright ©2010 Futier et al; licensee BioMed Central Ltd.

                This is an open access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 15 May 2010
                : 16 July 2010
                : 29 October 2010
                Categories
                Research

                Emergency medicine & Trauma
                Emergency medicine & Trauma

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