Intraoperative Dexamethasone is associated with a lower risk of respiratory failure in Thoracic Surgery: Observational cohort study (SURTHODEX).

BACKGROUND: Postoperative complications, particularly respiratory complications, are of significant clinical concern in patients undergoing elective thoracic surgery. Dexamethasone (DXM), commonly administered to prevent postoperative nausea and vomiting (PONV), has potential anti-inflammatory effects that might be beneficial in reducing these complications. We aimed to investigate whether intraoperative DXM administration could mitigate the occurrence of respiratory complications following elective thoracic surgery. METHODS: We conducted a single-center observational study, including patients who underwent elective thoracic surgery from 2012 to 2020. The primary outcome was the onset of acute respiratory failure within 7 days post-surgery. Secondary outcomes encompassed other postoperative complications, duration of hospital stay, and mortality within 30 days post-surgery. An overlap propensity score analysis was employed to estimate the treatment effect. RESULTS: We included 1,247 adult patients, 897 who received dexamethasone (DXM) and 350 who served as controls. Intraoperative dexamethasone administration was associated with a significant reduction in respiratory complications with an adjusted relative risk (RR) of 0.65 (95% CI: 0.43-0.97). There was also a significant decline in composite infectious criteria with an adjusted RR of 0.76 (95% CI: 0.63-0.93). Cardiac complications were also assessed as a composite criterion, and a significant reduction was observed (adjusted RR, 0.68; 95% CI, 0.51-0.9). However, there were no association with mechanical complications, mortality within 30 days (adjusted RR of 0.43, 95% CI: 0.17-1.09) or in the length of hospital stay (adjusted RR of 0.85, 95% CI: 0.71-1.02). CONCLUSIONS: Dexamethasone administration was associated with a reduction in postoperative respiratory complications. Further prospective studies are needed to confirm these findings.

Evaluation of the early use of norepinephrine in major abdominal surgery on medical and surgical postoperative complications: study protocol for a randomised controlled trial (EPON STUDY).

BACKGROUND: Post-induction anaesthesia often promotes intraoperative hypotension (IOH) that can worsen postoperative outcomes. This study aims to assess the benefit of norepinephrine versus ephedrine at the induction of anaesthesia to prevent postoperative complications following major abdominal surgery by preventing IOH. METHODS AND ANALYSIS: The EPON STUDY is a prospective single-centre randomised controlled trial with the planned inclusion of 500 patients scheduled for major abdominal surgery at the Amiens University Hospital. The inclusion criteria are patients aged over 50 years weighing more than 50 kg with an American Society of Anesthesiologists physical status score of ≥2 undergoing major abdominal surgery under general anaesthesia. Patients are allocated either to the intervention group (n=250) or the standard group (n=250). In the intervention group, the prevention of post-induction IOH is performed with norepinephrine (dilution to 0.016 mg/mL) using an electric syringe pump at a rate of 0.48 mg/h (30 mL/h) from the start of anaesthesia and then titrated to achieve the haemodynamic target. In the control group, the prevention of post-induction IOH is performed with manual titration of ephedrine, with a maximal dose of 30 mg, followed by perfusion with norepinephrine. In both groups, the haemodynamic target to maintain is a mean arterial pressure (MAP) of 65 mm Hg or 70 mm Hg for patients with a medical history of hypertension. An intention-to-treat analysis will be performed. The primary outcome is the Clavien-Dindo score assessed up to 30 days postoperatively. The secondary endpoints are the length of hospital stay and length of stay in an intensive care unit/postoperative care unit; postoperative renal function; postoperative cardiovascular, respiratory, neurological, haematological and infectious complications at 1 month; and volume of intraoperative vascular filling and mortality at 1 month. ETHICS AND DISSEMINATION: Ethical approval was obtained from the committee of protection of the persons of Ile de France in May 2021 (number 21 05 41). The authors will be involved in disseminating the research findings (through attending conferences and co-authoring papers). The results of the study will be disseminated via peer-reviewed publications and presentations at national and international conferences. TRIAL REGISTRATION NUMBER: NCT05276596.

S erratus anterior plane block alone, paravertebral block alone and their combination in video-assisted thoracoscopic surgery: the THORACOSOPIC double-blind, randomized trial.

OBJECTIVES: Serratus anterior plane block (SAPB) and paravertebral block (PVB) are well known to reduce pain levels after video-assisted thoracoscopic surgery (VATS). However, the relative efficacies of each block and a combination of the 2 have not been fully characterized. The objective of the present study was to assess the efficacy of PVB alone, SAPB alone and the combination of PVB and SAPB with regard to the occurrence and intensity of pain after VATS. METHODS: We conducted the THORACOSOPIC single-centre, double-blind, randomized trial in adult patients due to undergo elective VATS lung resection. The participants were randomized to PVB only, SAPB only and PVB + SAPB groups. The primary end-point was pain on coughing on admission to the postanaesthesia care unit. The secondary end-points were postoperative pain at rest and on coughing at other time points and the cumulative opioid consumption. Pain was scored on a visual analogue scale. RESULTS: One-hundred and fifty-six patients (52 in each group) were included. On admission to the postanaesthesia care unit, the 3 groups did not differ significantly with regard to the pain on coughing: the visual analogue scale score was 3 (0-6), 4 (0-8) and 2 (0-6) in the PVB, SAPB and PVB + SAPB groups, respectively (P = 0.204). During postoperative care, the overall pain score was significantly lower in the SABP + PVP group at rest and on cough. CONCLUSIONS: The combination of SABP + PVB could be beneficial for pain management in VATS in comparison to SABP or PVB alone.

Determinants of postoperative complications in high-risk noncardiac surgery patients optimized with hemodynamic treatment strategies: A post-hoc analysis of a randomized multicenter clinical trial.

STUDY OBJECTIVE: This post-hoc analysis of a randomized controlled trial was undertaken to establish the determinants of postoperative complications and acute kidney injury in high-risk noncardiac surgery patients supported with hemodynamic treatment strategies. DESIGN: We conducted a post-hoc analysis of patients enrolled in the OPtimization Hemodynamic Individualized by the respiratory QUotiEnt (OPHIQUE) trial. SETTING: Operating rooms in four university medical centers and one non-university hospital from December 26, 2018, to September 9, 2021. PATIENTS: We enrolled 350 patients with a high risk of postoperative complications undergoing high-risk noncardiac surgery lasting 2 h or longer under general anesthesia. INTERVENTIONS: All patients were treated according to hemodynamic treatment strategies which included cardiac output optimization by titration of fluid challenge and targeted systolic blood pressure to remain within ±10% of the reference value. MEASUREMENTS: We assessed the association between pre-operative and intra-operative exposure of interest with a composite primary outcome of major complications or death within seven days following surgery using a multivariable logistic regression model. We also assessed the association between these exposures of interest and acute kidney injury. MAIN RESULTS: The data of 341 patients were analyzed. In multivariate analysis, the factors independently associated with the primary outcome were age (OR = 1.04 (1.01-1.06), P = 0.002), preoperative hemoglobin concentration (OR = 0.85 (0.75-0.96), P = 0.012), non-vascular surgery (OR = 0.30 (0.17-0.53), P < 0.0001), and intraoperative surgical complications (OR = 2.08 (1.02-4.24), P = 0.046). The factors independently associated with postoperative acute kidney injury were age (OR = 1.04 (1.01-1.08), P = 0.008), preoperative creatinine concentration (OR = 1.01 (1.00-1.01), P = 0.049), non-vascular surgery (OR = 0.36 (0.20-0.66), P = 0.001), and intraoperative surgical complications (OR = 3.36 (1.50-7.55), P = 0.031). CONCLUSIONS: Surgical complications, a lower preoperative hemoglobin concentration, age, and vascular surgery were associated with postoperative complications in a high-risk noncardiac surgery population supported with hemodynamic treatment strategies.

Effect of norepinephrine on the vascular waterfall and tissue perfusion in vasoplegic hypotensive patients: a prospective, observational, applied physiology study in cardiac surgery.

BACKGROUND: Norepinephrine is a commonly used drug for treating vasoplegic acute circulatory failure in ICU. The prediction of norepinephrine macro- and micro-circulatory response is complicated by its uneven receptors' distribution between the arterial and the venous structures, and by the presence of a physiological vascular waterfall (VW) that disconnects the arterial and the venous circulation in two pressure systems. The objectives of this study were to describe the VW in patients with arterial hypotension due to vasodilatory circulatory shock, and its behavior according to its response to norepinephrine infusion. METHODS: A prospective, observational, bi-centric study has included adult patients, for whom the physician decided to initiate norepinephrine during the six first hours following admission to the ICU after cardiac surgery, and unresponsive to a fluid challenge. The mean systemic pressure (MSP) and the critical closing pressure (CCP) were measured at inclusion and after norepinephrine infusion. RESULTS: Thirty patients were included. Norepinephrine increased arterial pressure and total peripheral resistances in all cohort. The cohort was dichotomized as VW responders (patients with a change of VW over the least significant change (≥ 93% increase in VW)), and as VW non-responders. In 19 (63%) of the 30 patients, VW increased from 3.47 [- 14.43;7.71] mmHg to 43.6 [25.8;48.1] mmHg, p < 0.001) with norepinephrine infusion, being classified as VW responders. The VW responders improved cardiac index (from 1.8 (0.6) L min-1 m-2 to 2.2 (0.5) L min-1 m-2, p = 0.002), capillary refill time (from to 4.2 (1.1) s to 3.1 (1) s, p = 0.006), and pCO2 gap (from 9 [7;10] mmHg to 6 [4;8] mmHg, p = 0.04). No baseline parameters were able to predict the VW response to norepinephrine. In comparison, VW non-responders did not significantly change the VW (from 5 [-5;16] mmHg to -2 [-12;15] mmHg, p = 0.17), cardiac index (from 1.6 (0.3) L min-1 m-2 to 1.8 (0.4) L min-1 m-2, p = 0.09) and capillary refill time (from 4.1 (1) s to 3.7 (1.4), p = 0.44). CONCLUSIONS: In post-cardiac surgery patients with vasoplegic arterial hypotension, the vascular waterfall is low. Norepinephrine did not systematically restore the vascular waterfall. Increase of the vascular waterfall was associated with an improvement of laboratory and clinical parameters of tissue perfusion.

Respiratory Exchange Ratio guided management in high-risk noncardiac surgery: The OPHIQUE multicentre randomised controlled trial.

BACKGROUND: There is a need to develop non-invasive markers to identify the occurrence of anaerobic metabolism in high-risk surgery. Our objective was to demonstrate that a goal-directed therapy algorithm incorporating the respiratory exchange ratio (ratio between CO2 production and O2 consumption) can reduce postoperative complications. METHODS: We conducted a randomized, multicenter, controlled clinical trial in four university medical centers and one non-university hospital from December 26, 2018, to September 9, 2021. 350 patients with a high risk of postoperative complications undergoing high-risk noncardiac surgery lasting 2 h or longer under general anesthesia were enrolled. The control group was treated according to current hemodynamic guidelines. The interventional group was treated according to an algorithm based on the measurement of the respiratory exchange ratio. The primary outcome was a composite of major complications or death within seven days of surgery. The secondary outcomes were the length of hospital stay, 30-day mortality, and the total intraoperative volume of fluids administered. RESULTS: The primary outcome occurred for 78 patients (45.6%) in the interventional group and 83 patients (48.8%) in the control group (relative risk: 0.93, 95% confidence interval [CI]: 0.75-1.17; p = 0.55). There were no clinically relevant differences between the two groups for secondary outcomes. CONCLUSIONS: In high-risk surgery, a goal-directed therapy algorithm integrating the measurement of the respiratory-exchange ratio did not reduce a composite outcome of major postoperative complications or death within seven days after surgery compared to routine care. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03852147.

Assessment of fluid unresponsiveness guided by lung ultrasound in abdominal surgery: a prospective cohort study.

A fluid challenge can generate an infraclinical interstitial syndrome that may be detected by the appearance of B-lines by lung ultrasound. Our objective was to evaluate the appearance of B-lines as a diagnostic marker of preload unresponsiveness and postoperative complications in the operating theater. We conducted a prospective, bicentric, observational study. Adult patients undergoing abdominal surgery were included. Stroke volume (SV) was determined before and after a fluid challenge with 250 mL crystalloids (Delta-SV) using esophageal Doppler monitoring. Responders were defined by an increase of Delta-SV > 10% after fluid challenge. B-lines were collected at four bilateral predefined zones (right and left anterior and lateral). Delta-B-line was defined as the number of newly appearing B-lines after a fluid challenge. Postoperative pulmonary complications were prospectively recorded according to European guidelines. In total, 197 patients were analyzed. After a first fluid challenge, 67% of patients were responders and 33% were non-responders. Delta-B-line was significantly higher in non-responders than responders [4 (2-7) vs 1 (0-3), p < 0.0001]. Delta-B-line was able to diagnose fluid non-responders with an area under the curve of 0.74 (95% CI 0.67-0.80, p < 0.0001). The best threshold was two B-lines with a sensitivity of 80% and a specificity of 57%. The final Delta-B-line could predict postoperative pulmonary complications with an area under the curve of 0.74 (95% CI 0.67-0.80, p = 0.0004). Delta-B-line of two or more detected in four lung ultrasound zones can be considered to be a marker of preload unresponsiveness after a fluid challenge in abdominal surgery.The objectives and procedures of the study were registered at Clinicaltrials.gov (NCT03502460; Principal investigator: Stéphane BAR, date of registration: April 18, 2018).

Dynamic Arterial Elastance Is Associated With the Vascular Waterfall in Patients Treated With Norepinephrine: An Observational Study.

Introduction: It has been suggested that dynamic arterial elastance (Eadyn) can predict decreases in arterial pressure in response to changing norepinephrine levels. The objective of this study was to determine whether Eadyn is correlated with determinants of the vascular waterfall [critical closing pressure (CCP) and systemic arterial resistance (SARi)] in patients treated with norepinephrine. Materials and Methods: Patients treated with norepinephrine for vasoplegia following cardiac surgery were studied. Vascular and flow parameters were recorded immediately before the norepinephrine infusion and then again once hemodynamic parameters had been stable for 15 min. The primary outcomes were Eadyn and its associations with CCP and SARi. The secondary outcomes were the associations between Eadyn and vascular/flow parameters. Results: At baseline, all patients were hypotensive with Eadyn of 0.93 [0.47;1.27]. Norepinephrine increased the arterial blood pressure, cardiac index, CCP, total peripheral resistance (TPRi), arterial elastance, and ventricular elastance and decreased Eadyn [0.40 (0.30;0.60)] and SARi. Eadyn was significantly associated with arterial compliance (CA), CCP, and TPRi (p < 0.05). Conclusion: In patients with vasoplegic syndrome, Eadyn was correlated with determinants of the vascular waterfall. Eadyn is an easy-to-read functional index of arterial load that can be used to assess the patient's macro/microcirculatory status. Clinical Trial Registration: ClinicalTrials.gov #NCT03478709.

Changes in Plasma Angiopoietin Levels After Transcatheter Aortic Valve Replacement and Surgical Aortic Valve Replacement: A Prospective Cohort Study.

OBJECTIVE: Angiopoietins (Angs) regulate endothelial permeability. Ang-1 and 2 (Ang-1 and Ang-2) are implied in endothelial stability through an antagonism effect. The objectives of the present study were to describe and compare changes in Ang levels after transcatheter aortic valve replacement (TAVR) and surgical aortic valve replacement (SAVR). DESIGN: A prospective, single-center study. PARTICIPANTS: Adult patients with aortic stenosis scheduled for SAVR or TAVR. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Ang-1 and Ang-2 were measured using an enzyme-linked immunosorbent assay right before surgery (T0), at the end of surgery (T1), and at day one (T2). Sixty consecutive patients (SAVR group [n = 30] and TAVR group [n = 30]) were included between January and June 2017. Ang-1 decreased significantly after both TAVR (T0: 3,663 [2,602-4,262]; T1: 1,611 [981-2,409]; T2: 1,082 [652-1,589] ng/mL; p < 0.0001) and SAVR (T0: 1,603 [975-2,849]; T1: 783 [547-1,024]; T2: 828 [460-1,227] ng/mL; p = 0.0001). Ang-2 increased significantly after SAVR (T0: 2,472 [1,502-3,622]; T1: 2,997 [1,759-3,839]; T2: 5,421 [3,557-7,087] ng/mL; p < 0.0001) but did not change markedly after TAVR (T0: 3,343 [2,661-6,272]; T1: 3,788 [2,574-5,016]; T2: 3,446 [3,029-6,313] ng/mL; p = 0.066). Among patients with paravalvular leakage, the changes in the plasma Ang-2 level and the Ang-2/Ang-1 ratio were greater. CONCLUSION: SAVR induces greater alterations of Ang homeostasis than TAVR, confirming a role for the use of cardiopulmonary bypass. Paravalvular leakage after TAVR is associated with Ang changes similar to those observed with SAVR.

Echocardiographic measure of dynamic arterial elastance predict pressure response during norepinephrine weaning: an observational study.

The purpose of this study was to determine whether dynamic elastance EAdyn derived from echocardiographic measurements of stroke volume variations can predict the success of a one-step decrease of norepinephrine dose. In this prospective single-center study, 39 patients with vasoplegic syndrome treated with norepinephrine and for whom the attending physician had decided to decrease norepinephrine dose and monitored by thermodilution were analyzed. EAdyn is the ratio of pulse pressure variation to stroke volume variation and was calculated from echocardiography stroke volume variations and from transpulmonary thermodilution. Pulse pressure variation was obtained from invasive arterial monitoring. Responders were defined by a decrease in mean arterial pressure (MAP) > 10% following norepinephrine decrease. The median decrease in norepinephrine was of 0.04 [0.03-0.05] µg kg-1 min-1. Twelve patients (31%) were classified as pressure responders with a median decrease in MAP of 13% [12-15%]. EAdyn was lower in pressure responders (0.40 [0.24-0.57] vs 0.95 [0.77-1.09], p < 0.01). EAdyn was able to discriminate between pressure responders and non-responders with an area under the curve of 0.86 (CI95% [0.71 to1.0], p < 0.05). The optimal cut-off was 0.8. EAdyn calculated from the echocardiographic estimation of the stroke volume variation and the invasive arterial pulse pressure variation can be used to discriminate pressure response to norepinephrine weaning. Agreement between EAdyn calculated from echocardiography and thermodilution was poor. Echocardiographic EAdyn might be used at bedside to optimize hemodynamic treatment.

Predictive value of the respiratory exchange ratio for the occurrence of postoperative complications in laparoscopic surgery: a prospective and observational study.

Indirect measurement of the respiratory exchange ratio (RER) has been shown to predict the occurrence of postoperative complications after major open non-cardiac surgery. Our main objective was to demonstrate the ability of the RER, indirectly measured by the anaesthesia respirator, to predict the occurrence of postoperative complications following laparoscopic surgery. We performed an observational, prospective and monocentric study. Haemodynamic and respiratory parameters were collected at several timepoints to calculate the RER by a non-volumetric method: RER = (FetCO2-FiCO2)/(FiO2-FetO2). Fifty patients were prospectively included. Nine patients (18%) had at least one postoperative complication. The mean RER was significantly higher for the subgroup of patients with complications than the subgroup without (1.04 ± 0.27 vs 0.88 ± 0.13, p < 0.05). The RER could predict the occurrence of post-operative complications with an area under the ROC curve of 0.73 (95% CI 0.59-0.85, p = 0.021). The best cut off was 0.98, with a sensitivity of 56% and a specificity of 88%. One hour after insufflation, the FiO2-FetO2 difference was significantly lower and the RER was significantly higher in the complications subgroup than in the subgroup without complications (4.4/- 1.6% vs 5.8/- 1.2%, p = 0.001 and 0.95 [0.85-1.04] vs 0.83 [0.75-0.92], p = 0.04, respectively). The RER measured during laparoscopic surgery can predict the occurrence of postoperative complications.Trial registration The objectives and procedures of the study was registered at Clinicaltrials.gov (NCT03751579); date: November 23, 2018.

Individualized hemodynamic optimization guided by indirect measurement of the respiratory exchange ratio in major surgery: study protocol for a randomized controlled trial (the OPHIQUE study).

BACKGROUND: Observational studies have suggested that a high respiratory exchange ratio (RER) is associated with the occurrence of postoperative complications. The study's primary objective is to demonstrate that the incidence of postoperative complications is lower in an interventional group (patients monitored using a hemodynamic algorithm that incorporates the RER) than in a control group (treated according to standard practice). METHODS: We shall perform a prospective, multicenter, randomized, open-label, superiority trial of consecutive patients undergoing major noncardiac surgery (i.e., abdominal, vascular, and orthopedic surgery). The control group will be treated according to the current guidelines on standard hemodynamic care. The interventional group will be treated according to an algorithm based on the RER. The primary outcome will be the occurrence of at least one complication in the 7 days following surgery. The secondary outcomes will be the length of hospital stay, the total number of complications per patient, the 30-day mortality, the total intraoperative volume of fluids administered, and the Sequential [sepsis-related] Organ Failure Assessment (SOFA) score and laboratory data measured on postoperative days 1, 2, and 7. A total of 350 patients will be included. DISCUSSION: In the operating theater, the RER is potentially a continuously available, easy-to-read, indirect marker of tissue hypoperfusion and postoperative complications. If the RER does predict the occurrence of tissue hypoperfusion, it will help the physician to provide personalized hemodynamic management and limit the side effects associated with excessive hemodynamic optimization (volume overload, vasoconstriction, etc.). TRIAL REGISTRATION: ClinicalTrials.gov NCT03852147 . Registered on February 25, 2019.

Vasoplegia After Cardiac Surgery Is Associated With Endothelial Glycocalyx Alterations.

OBJECTIVE: To assess endothelial glycocalyx (EG) alteration in vasoplegic syndrome after cardiac surgery with cardiopulmonary bypass. DESIGN: Prospective analysis SETTING: Single university hospitals. PARTICIPANTS: Patients undergoing elective cardiac surgery under cardiopulmonary bypass. INTERVENTIONS: Observational study METHODS: Heparan sulfate and syndecan-1 levels were assessed in plasma before surgery, on intensive care unit admission, and on the first postoperative day. The primary outcome was comparisons of heparan sulfate and syndecan-1 levels in patients with and without vasoplegic syndrome. RESULTS: A total of 46 patients were analyzed. Only syndecan-1 was modified by cardiac surgery (p < 0.05). Plasma syndecan-1 levels were lower in patients with vasoplegic syndrome at the 3 time-points and were associated with the cumulative norepinephrine dose. Baseline plasma syndecan-1 predicted the development of vasoplegic syndrome with an area under the curve of 0.7 (confidence interval 95%: 0.51-0.85, p = 0.045). Heparan sulfate levels were not modified by cardiac surgery. CONCLUSION: Patients with vasoplegic syndrome after cardiac surgery present a different pattern of EG components. Lower syndecan-1 levels were associated with vasoplegic syndrome. These preliminary results suggest a specific phenotype that may reflect endothelial activation leading to alteration of the EG.

Predicting postoperative complications with the respiratory exchange ratio after high-risk noncardiac surgery: A prospective cohort study.

BACKGROUND: The respiratory exchange ratio (RER), defined as the ratio of CO2 production (VCO2) to O2 consumption (VO2), is reported to be a noninvasive marker of anaerobic metabolism. The intubated, ventilated patient's inspired and expired fractions of O2 and CO2 (FiO2, FeO2, FiCO2 and FeCO2) are monitored in the operating room and can be used to calculate RER. OBJECTIVE: To investigating the ability of the RER to predict postoperative complications. DESIGN: An observational, prospective study. SETTING: Two French university hospitals between March 2017 and September 2018. PATIENTS: A total of 110 patients undergoing noncardiac high-risk surgery. MAIN OUTCOME MEASURES: The RER was calculated as (FeCO2 - FiCO2)/(FiO2 - FeO2) at five time points during the operation. The primary endpoint was at the end of the surgery. The secondary endpoints were systemic oxygenation indices (pCO2 gap, pCO2 gap/arteriovenous difference in O2 ratio, central venous oxygen saturation) and the arterial lactate level at the end of the surgery. Complications were classified according to the European Peri-operative Clinical Outcome definitions. RESULTS: Postoperative complications occurred in 35 patients (34%). The median [interquartile range] RER at the end of surgery was significantly greater in the subgroup with complications, 1.06 [0.84 to 1.35] than in the subgroup without complications, 0.81 [0.75 to 0.91], and correlated significantly with the arterial lactate (r = 0.31, P < 0.001) and VO2 (r = -0.23, P = 0.001). Analysis of the area under the receiver operating characteristic curve for the predictive value of RER for postoperative complications revealed a value of 0.77 [95% confidence interval (CI) 0.69 to 0.88, P = 0.001]. The best cut-off for the RER was 0.94, with a sensitivity of 71% (95% CI 54 to 85) and a specificity of 79% (95% CI 68 to 88). CONCLUSION: As a putative noninvasive marker of tissue hypoperfusion and anaerobic metabolism, the RER can be used to predict complications following high-risk surgery. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03471962.

Regional capnometry to evaluate the adequacy of tissue perfusion.

Tissue hypoperfusion is a major cause of morbidity and mortality in critically ill patients but cannot always be detected by measuring standard whole-body hemodynamic and oxygen-related parameters (e.g., blood pressure, cardiac output, and central venous oxygen saturation). Preclinical and clinical studies have demonstrated that low-flow states are consistently associated with large increases in venous and tissue PCO2. Monitoring regional PCO2 with gastric tonometry (PgCO2) is known to have independent prognostic value for predicting postoperative complications and mortality. The PgCO2 gap might also be of value as a treatment target (endpoint) in critically ill patients. However, this tool has several limitations and has not yet been developed commercially, thus restricting its use. Regional capnography with sublingual and transcutaneous sensors might be an alternative noninvasive option for evaluating the adequacy of tissue perfusion in critically ill patients. However, further studies are needed to determine whether or not this monitoring technique is of value-particularly as an endpoint for guiding resuscitation. Bladder PCO2, has only been evaluated in animal studies, and so remains to be validated in patients.