Respiratory quotient estimations as additional prognostic tools in early septic shock

Markers of Tissue Perfusion as Predictors of Adverse Outcomes in Patients with Left Ventricular Dysfunction Undergoing Coronary Artery Bypass Surgery

BACKGROUND

Cardiac surgery patients may be exposed to tissue hypoperfusion and anaerobic metabolism.

OBJECTIVE

To verify whether the biomarkers of tissue hypoperfusion have predictive value for prolonged intensive care unit (ICU) stay in patients with left ventricular dysfunction who underwent coronary artery bypass surgery.

METHODS

After approval by the institution's Ethics Committee and the signing of informed consent, 87 patients with left ventricular dysfunction (ejection fraction < 50%) undergoing coronary artery bypass surgery were enrolled. Hemodynamic and metabolic biomarkers were collected at five time points: after anesthesia, at the end of the surgery, at ICU admission, and at six and twelve hours after. An analysis of variance for repeated measures followed by a Bonferroni post hoc test was used for repeated, continuous variables (hemodynamic and metabolic variables) to determine differences between the two groups over the course of the study period. The level of statistical significance adopted was 5%.

RESULTS

Thirty-eight patients (43.7%) who presented adverse outcomes were older, higher Euro score (p<0.001), and elevated ΔpCO2 as analyzed 12 hours after ICU admission (p<0.01), while increased arterial lactate concentration at 6 hours postoperatively was found to be a negative predictive factor (p<0.01).

CONCLUSIONS

Euro SCORE, six-hour postoperative arterial lactate, 12-hour postoperative ΔPCO2, and eRQ are independent predictors of adverse outcomes in patients with left ventricular dysfunction after cardiac surgery.

The Prediction of Surgery Outcomes in Abdominal Tumor Patients with Sepsis by Pcv-aCO2/Ca-cvO2

Background

To determine whether Pcv-aCO2/Ca-cvO2 combined with Pcv-aCO2 could predict the outcomes in patients complicated with abdominal infection and sepsis after abdominal tumor operation.

Methods

Total 92 patients admitted to our hospital from January 2017 to December 2020 who underwent abdominal tumor operation were enrolled. Blood gas analysis of artery and central vein, various laboratory indexes, SOFA score, hemodynamic parameters at different time points and treatment outcome were recorded.

Results

ROC curve analysis showed that hemodynamic parameter alone could not predict ICU treatment outcome and mortality of patients, but 72-hour SOFA score could predict treatment outcome of patients (AUC = 0.930, 95% CI: 0.803–1.000, p = 0.019). The significant hemodynamic parameter for evaluating treatment outcome and prognosis of patients was Pcv-aCO2 + Ratio of T3. Kaplan–Meier univariate survival curve and Log-rank suggested that patients who had higher combined predictive parameter of T3 Ratio + T3 Pcv-aCO2 still had ischemia and hypoxia of tissues and organs after standard fluid resuscitation, and treatment outcome was not good. In subgroup analysis, patients with higher Ratio had higher lactate, higher T72 SOFA score, and poor treatment outcome.

Conclusion

The combination of Ratio and Pcv-aCO2 could evaluate clinical treatment outcome of patients complicated with abdominal infection and sepsis after abdominal tumor operation.

Insulin and cancer: a tangled web

For a century, since the pioneering work of Otto Warburg, the interwoven relationship between metabolism and cancer has been appreciated. More recently, with obesity rates rising in the U.S. and worldwide, epidemiologic evidence has supported a link between obesity and cancer. A substantial body of work seeks to mechanistically unpack the association between obesity, altered metabolism, and cancer. Without question, these relationships are multifactorial and cannot be distilled to a single obesity- and metabolism-altering hormone, substrate, or factor. However, it is important to understand the hormone-specific associations between metabolism and cancer. Here, we review the links between obesity, metabolic dysregulation, insulin, and cancer, with an emphasis on current investigational metabolic adjuncts to standard-of-care cancer treatment.

Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia

The purpose of the study was to evaluate the behavior of the venous-to-arterial CO₂ tension difference (ΔPCO₂) over the arterial-to-venous oxygen content difference (ΔO₂) ratio (ΔPCO₂/ΔO₂) and the difference between venous-to-arterial CO₂ content calculated with the Douglas’ equation (ΔCCO_2D) over ΔO₂ ratio (ΔCCO_2D/ΔO₂) and their abilities to reflect the occurrence of anaerobic metabolism in two experimental models of tissue hypoxia: ischemic hypoxia (IH) and hypoxic hypoxia (HH). We also aimed to assess the influence of metabolic acidosis and Haldane effects on the PCO₂/CO₂ content relationship. In a vascularly isolated, innervated dog hindlimb perfused with a pump-membrane oxygenator system, the oxygen delivery (DO₂) was lowered in a stepwise manner to decrease it beyond critical DO₂ (DO_2crit) by lowering either arterial PO₂ (HH-model) or flow (IH-model). Twelve anesthetized and mechanically ventilated dogs were studied, 6 in each model. Limb DO₂, oxygen consumption (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\dot{\text{V}}\text{O}}_{2}$$\end{document}V˙O2), ΔPCO₂/ΔO₂, and ΔCCO_2D/ΔO₂ were obtained every 15 min. Beyond DO_2crit, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\dot{\text{V}}\text{O}}_{2}$$\end{document}V˙O2 decreased, indicating dysoxia. ΔPCO₂/ΔO₂, and ΔCCO_2D/ΔO₂ increased significantly only after reaching DO_2crit in both models. At DO_2crit, ΔPCO₂/ΔO₂ was significantly higher in the HH-model than in the IH-model (1.82 ± 0.09 vs. 1.39 ± 0.06, p = 0.002). At DO_2crit, ΔCCO_2D/ΔO₂ was not significantly different between the two groups (0.87 ± 0.05 for IH vs. 1.01 ± 0.06 for HH, p = 0.09). Below DO_2crit, we observed a discrepancy between the behavior of the two indices. In both models, ΔPCO₂/ΔO₂ continued to increase significantly (higher in the HH-model), whereas ΔCCO_2D/ΔO₂ tended to decrease to become not significantly different from its baseline in the IH-model. Metabolic acidosis significantly influenced the PCO₂/CO₂ content relationship, but not the Haldane effect. ΔPCO₂/ΔO₂ was able to depict the occurrence of anaerobic metabolism in both tissue hypoxia models. However, at very low DO₂ values, ΔPCO₂/ΔO₂ did not only reflect the ongoing anaerobic metabolism; it was confounded by the effects of metabolic acidosis on the CO₂–hemoglobin dissociation curve, and then it should be interpreted with caution.

Utility of venous-to-arterial carbon dioxide changes to arteriovenous oxygen content ratios in the prognosis of severe sepsis and septic shock: A systematic review and meta-analysis

Background:

Sepsis patients with insufficient tissue perfusion and hypoxia should be identified and resuscitated immediately. Recently, venous-to-arterial carbon dioxide pressure changes and the arteriovenous oxygen content difference ratio (Pcv-aCO2/Ca-vO2) as a predictor of tissue perfusion recovery and poor prognosis.

Objectives:

Pcv-aCO2/Ca-vO2 is a substitute for respiratory entropy, the elevation of which indicates a lack of tissue perfusion. Pcv-aCO2/Ca-vO2 can be used as an indicator to predict the prognosis of patients with sepsis or septic shock, but its prognostic value has not been fully evaluated. Here, we have performed a meta-analysis to assess its predictive value for mortality.

Methods:

Meta-analysis of Observational Studies in Epidemiology group guidelines were followed for this meta-analysis. We searched the comprehensive electronic databases of PubMed, EMBASE, Web of Science, and Cochrane libraries from inception to March 2019, using the terms including “venous-arterial,” “carbon dioxide,” “Shock, Septic,” and related keywords. The Newcastle-Ottawa scale was used for quality evaluation of the literature. A meta-analysis was performed using RevMan 5.3 and Stata 14.0 software to evaluate the effects of Pcv-aCO2/Ca-vO2 on short-term mortality, sequential organ failure assessment, and acute physiology and chronic health evaluation scores in patients with sepsis or septic shock.

Results:

The final analysis included 13 clinical studies involving a total of 940 subjects. The results of the meta-analysis showed that non-surviving patients had higher Pcv-aCO2/Ca-vO2 than survivors after fluid resuscitation (standardized mean difference = 0.68, 95% confidence interval = 0.24–1.12) and blood samples taken 6 h after resuscitation showed a greater risk of mortality (risk ratio = 1.89, 95% confidence interval = 1.48–2.41) and sequential organ failure assessment scores (mean difference = 1.58, 95% confidence interval = 0.88–2.28, P < 0.01) in patients with high Pcv-aCO2/Ca-vO2. These differences were statistically significant.

Conclusion:

This meta-analysis indicates that Pcv-aCO2/Ca-vO2 has predictive value for mortality in patients with sepsis or septic shock. Further studies are now required to determine the optimal threshold for predicting sepsis mortality.

Prospero Registration:

The protocol for this systematic review was registered on PROSPERO (CRD 42019128134).

Veno-arterial CO2 difference and respiratory quotient after cardiac arrest: An observational cohort study

PURPOSE

To characterize venous-arterial CO₂ difference (ΔpCO₂) and the respiratory quotient (RQ) in post cardiac arrest patients and evaluate the association between these parameters and patient outcome.

MATERIALS AND METHODS

Data were obtained retrospectively from post cardiac arrest patients admitted between 2007 and 2016 to a medical intensive care unit. Comatose, adult patients in whom arterial and venous blood gas analyses were concomitantly performed in the first 24 h were included. Patients were grouped according to the time-point of sampling; 0-6, 6-12 and 12-24 h after admission.

RESULTS

308 patients were included; 174 (56%) died before ICU discharge and 212 (69%) had an unfavorable neurologic outcome. RQ was associated with ICU mortality (OR:1.09 (95%CI: 1.04-1.14; p < 0.01)), although not with neurological outcome. ΔpCO₂ was negatively associated with both ICU mortality (OR: 0.92 (95%CI: 0.86-0.99; p = 0.02)) and poor neurologic outcome (adjusted OR: 0.93 (95%CI: 0.87-0.99; p = 0.02)). ΔpCO₂ predicted an elevated RQ; a ΔpCO₂ above 8.5 mmHg identified a high RQ with reasonable sensitivity and specificity.

CONCLUSIONS

RQ was associated with ICU mortality and ΔpCO₂ identified elevated RQ in the early phase after cardiac arrest. However, ΔpCO₂ were negatively associated with both ICU mortality and neurologic outcome.

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.

How can CO2-derived indices guide resuscitation in critically ill patients?

Assessing the adequacy of oxygen delivery with oxygen requirements is one of the key-goal of haemodynamic resuscitation. Clinical examination, lactate and central or mixed venous oxygen saturation (S_vO₂ and S_cvO₂, respectively) all have their limitations. Many of them may be overcome by the use of the carbon dioxide (CO₂)-derived variables. The venoarterial difference in CO₂ tension ("ΔPCO₂" or "PCO₂ gap") is not an indicator of anaerobic metabolism since it is influenced by the oxygen consumption. By contrast, it reliably indicates whether blood flow is sufficient to carry CO₂ from the peripheral tissue to the lungs in view of its clearance: it, thus, reflects the adequacy of cardiac output with the metabolic condition. The ratio of the PCO₂ gap with the arteriovenous difference of oxygen content (PCO₂ gap/C_a-vO₂) might be a marker of anaerobiosis. Conversely to S_vO₂ and S_cvO₂, it remains interpretable if the oxygen extraction is impaired as it is in case of sepsis. Compared to lactate, it has the main advantage to change without delay and to provide a real-time monitoring of tissue hypoxia.

Central venous-to-arterial carbon dioxide difference combined with arterial-to-venous oxygen content difference (PcvaCO2/CavO2) reflects microcirculatory oxygenation alterations in early septic shock

PURPOSE

To explore the relationship between central venous-to-arterial carbon dioxide difference (P_cvaCO₂), P_cvaCO₂/arterial-venous oxygen content difference ratio (P_cvaCO₂/C_avO₂) and the microcirculatory status, evaluated by using near-infrared spectroscopy, in septic shock patients.

METHODS

Observational study in a 30-bed mixed ICU. Fifty septic shock patients within the first 24 h of ICU admission were studied. After restoration of mean arterial pressure, hemodynamic, metabolic and microcirculatory parameters were simultaneously evaluated. Local tissue oxygen saturation (StO₂), and local hemoglobin index (THI) were measured on the thenar eminence by means of near-infrared spectroscopy. A transient vascular occlusion test was performed in order to obtain StO₂ deoxygenation rate (DeO₂), local oxygen consumption (nirVO₂), and reoxgenation rate (ReO₂).

RESULTS

At inclusion, increased P_cvaCO₂ values were associated with lower StO₂ and THI, whereas increased P_cvaCO₂/C_avO₂ values were associated with lower DeO₂, nirVO₂, and ReO₂. Multiple regression models confirmed the association between P_cvaCO₂/C_avO₂ and nirVO₂, while P_cvaCO₂ was only related to CI, and not to microcirculatory parameters.

CONCLUSIONS

In a population of early septic shock patients, increases in P_cvaCO₂ and P_cvaCO₂/C_avO₂ reflected different alterations at the microcirculatory level. While P_cvaCO₂ was related to global flow, the P_cvaCO₂/C_avO₂ ratio was associated to impaired local oxygen utilization and diminished microvascular reactivity.