A call for immediate climate action in anesthesiology: routine use of minimal or metabolic fresh gas flow reduces our ecological footprint.

PURPOSE: Climate change is a global threat, and inhalational anesthetics contribute to global warming by altering the photophysical properties of the atmosphere. On a global perspective, there is a fundamental need to reduce perioperative morbidity and mortality and to provide safe anesthesia. Thus, inhalational anesthetics will remain a significant source of emissions in the foreseeable future. It is, therefore, necessary to develop and implement strategies to minimize the consumption of inhalational anesthetics to reduce the ecological footprint of inhalational anesthesia. SOURCE: We have integrated recent findings concerning climate change, characteristics of established inhalational anesthetics, complex simulative calculations, and clinical expertise to propose a practical and safe strategy to practice ecologically responsible anesthesia using inhalational anesthetics. PRINCIPAL FINDINGS: Comparing the global warming potential of inhalational anesthetics, desflurane is about 20 times more potent than sevoflurane and five times more potent than isoflurane. Balanced anesthesia using low or minimal fresh gas flow (≤ 1 L·min-1) during the wash-in period and metabolic fresh gas flow (0.35 L·min-1) during steady-state maintenance reduces CO2 emissions and costs by approximately 50%. Total intravenous anesthesia and locoregional anesthesia represent further options for lowering greenhouse gas emissions. CONCLUSION: Responsible anesthetic management choices should prioritize patient safety and consider all available options. If inhalational anesthesia is chosen, the use of minimal or metabolic fresh gas flow reduces the consumption of inhalational anesthetics significantly. Nitrous oxide should be avoided entirely as it contributes to depletion of the ozone layer, and desflurane should only be used in justified exceptional cases.

RéSUMé: OBJECTIF: Les changements climatiques constituent une menace mondiale et les anesthésiques volatils contribuent au réchauffement climatique en modifiant les propriétés photophysiques de l'atmosphère. Dans une perspective mondiale, il est fondamentalement nécessaire de réduire la morbidité et la mortalité périopératoires et de procurer une anesthésie sécuritaire. Par conséquent, les agents volatils demeureront une source importante d'émissions dans un avenir proche. Il est donc nécessaire d'élaborer et de mettre en œuvre des stratégies pour minimiser la consommation d'anesthésiques volatils afin de réduire l'empreinte écologique de l'anesthésie par inhalation. SOURCES: Nous avons intégré les découvertes récentes concernant les changements climatiques, les caractéristiques des anesthésiques volatils connus, des calculs de simulation complexes et l'expertise clinique pour proposer une stratégie pratique et sécuritaire pour exercer une anesthésie écologiquement responsable en utilisant des anesthésiques volatils. CONSTATATIONS PRINCIPALES: En comparant le potentiel de réchauffement planétaire des anesthésiques volatils, le desflurane est environ 20 fois plus puissant que le sévoflurane et cinq fois plus puissant que l'isoflurane. Une anesthésie équilibrée avec un débit de gaz frais faible ou minimal (≤ 1 L·min-1) pendant la période de mise en route ('wash-in') et le débit métabolique de gaz frais (0,35 L·min-1) pendant le maintien à l'état d'équilibre réduit le CO2 et les coûts d'environ 50 %. L'anesthésie intraveineuse totale et l'anesthésie locorégionale représentent d'autres options pour réduire les émissions de gaz à effet de serre. CONCLUSION: Les choix responsables en matière de prise en charge anesthésique devraient accorder la priorité à la sécurité des patients et à l'évaluation de toutes les options disponibles. Si l'anesthésie par inhalation est choisie, l'utilisation d'un débit minimal ou métabolique de gaz frais réduit considérablement la consommation d'anesthésiques volatils. Le protoxyde d'azote doit être complètement évité car il contribue à l'appauvrissement de la couche d'ozone, et le desflurane ne doit être utilisé que dans les cas exceptionnels et justifiés.

Improved Diagnosis of Iron Deficiency Anemia in the Critically Ill via Fluorescence Flowcytometric Hemoglobin Biomarkers.

BACKGROUND: Iron deficiency anemia (IDA) is common in critically ill patients treated in the intensive care unit (ICU), and it can lead to severe consequences. Precise and immediate diagnostics are not available, but they are inevitably needed to administer adequate therapy. Serological parameters such as serum ferritin and transferrin saturation (TSAT) are heavily influenced by simultaneous inflammation reactions, resulting in the need for more suitable parameters. Reticulocyte biomarkers such as reticulocyte hemoglobin content (RET-He) and Delta-hemoglobin equivalent (Delta-He) determined by fluorescence flowcytometry are more specific for the diagnosis of IDA-based anemia and should be investigated for this purpose. METHODS: In a prospective cohort single-center study, serum ferritin and transferrin saturation (TSAT) were collected and compared to RET-He and Delta-He by performing a receiver operating curve (ROC) analysis. The sensitivity and specificity of a single variable or the combination of two variables, as well as cutoff values, for the diagnosis of IDA were calculated. A group comparison for IDA patients without IDA was performed for a control group. RESULTS: A total of 314 patients were enrolled from an interdisciplinary ICU. RET-He (area under the curve (AUC) 0.847) and Delta-He (AUC 0.807) did indicate iron-deficient anemia that was more specific and sensitive in comparison to serum ferritin (AUC 0.678) and TSAT (AUC 0.754). The detection of functional iron deficiency (FID) occurred in 28.3% of cases with anemia. CONCLUSIONS: Determination of RET-He and Delta-He allows for the increased precision and sensitivity of iron-deficient anemia in the ICU.

Delta-Hemoglobin Equivalent and Granularity Index as Cell-Derived Biomarkers for the Detection of Bacterial Infections.

BACKGROUND: Prompt and precise detection of an infection in the blood is of great clinical importance in terms of early therapy initiation and the patient's prognosis. Infection-triggered inflammatory cellular and humoral signaling cascades offer great opportunities to redefine standard tests. However, while inexpensive and easy-to-use biomarkers for the detection of infections and the concomitant inflammatory processes exist, they are rarely used in clinical practice. We aimed to investigate the correlation of Granularity Index (GI) and Delta-hemoglobin equivalent (Delta-He) as inexpensive and easy-to-use cell-derived infection markers with established acute-phase parameters in a randomly selected patient. METHODS: We analyzed plasma concentrations of the established C-reactive protein (CRP) and procalcitonin (PCT) and leukocyte and thrombocyte counts in blood samples of 1,787 patients undergoing routine laboratory inflammation diagnostics. We also measured the Granularity Index (GI) and Delta-hemoglobin equivalent (Delta-He) in this cohort between February 2019 and February 2020. RESULTS: Delta-He and GI Index significantly correlated with CRP concentration (AUC 0.72, 95% CI 0.71 - 0.74; p < 0.001 for both analytes) and thrombocyte count (p < 0.001 for both analytes) but not with leukocyte count (AUC 0.54, 95% CI 0.50 - 0.59, p < 0.67). Furthermore, Delta-He significantly correlated with PCT (AUC 0.65, 95% CI 0.63 - 0.68, p < 0.001) while GI Index did not. Additionally, thrombocyte count significantly correlated with CRP (p < 0.001) and with PCT concentrations (p < 0.001). CONCLUSIONS: Delta-He and GI are two novel, inexpensive and easy-to-use cell-derived hematological biomarkers with the potential to be used as fully automated and highly standardized parameters. These biomarkers would be available on a 24 hours basis in the routine laboratory for the detection of bacterial infections by measuring a complete blood count (CBC) with differential and reticulocyte counts.

Quantitative Sensory Testing to Predict Postoperative Pain.

PURPOSE OF REVIEW: We review the relevance of quantitative sensory testing (QST) in light of acute and chronic postoperative pain and associated challenges. RECENT FINDINGS: Predicting the occurrence of acute and chronic postoperative pain with QST can help identify patients at risk and allows proactive preventive management. Generally, central QST testing, such as temporal summation of pain (TSP) and conditioned pain modulation (CPM), appear to be the most promising modalities for reliable prediction of postoperative pain by QST. Overall, QST testing has the best predictive value in patients undergoing orthopedic procedures. Current evidence underlines the potential of preoperative QST to predict postoperative pain in patients undergoing elective surgery. Implementing QST in routine preoperative screening can help advancing traditional pain therapy toward personalized perioperative pain medicine.

Valsalva Retinopathy: A Rare Complication After General Anesthesia.

Sudden visual loss after general anesthesia is a rare and serious complication. Unilateral visual loss can be caused by an increase in pressure in the preretinal veins with subsequent rupture and hematoma formation. Our patient most likely experienced an increase in venous pressure as a consequence of temporarily increased intrapulmonary pressures during a sustained Valsalva maneuver shortly after tracheal intubation. Although surgical correction is available, in almost all cases, no specific therapy is required because the problem completely regresses spontaneously.

Inhalational anaesthesia with low fresh gas flow.

During the inhalation of anaesthesia use of low fresh gas flow (0.35-1 L/min) has some important advantages. There are three areas of benefit: pulmonary - anaesthesia with low fresh gas flow improves the dynamics of inhaled anaesthesia gas, increases mucociliary clearance, maintains body temperature and reduces water loss. Economic - reduction of anaesthesia gas consumption resulting in significant savings of > 75% and Ecological - reduction in nitrous oxide consumption, which is an important ozone-depleting and heat-trapping greenhouse gas that is emitted. Nevertheless, anaesthesia with high fresh gas flows of 2-6 L/min is still performed, a technique in which rebreathing is practically negligible. This special article describes the clinical use of conventional plenum vaporizers, connected to the fresh gas supply to easily perform low (1 L/min), minimal (0.5 L/min) or metabolic flow anaesthesia (0.35 L/min) with conventional Primus Draeger(®) anaesthesia machines in routine clinical practice.

Local anesthetics inhibit thromboxane A2 signaling in Xenopus oocytes and human k562 cells.

Thromboxane A(2) (TXA(2)) has been proposed as a mediator of perioperative myocardial ischemia, vasoconstriction, and thrombosis. As these adverse events are minimized with epidural anesthesia, rather than general anesthesia, we hypothesized that local anesthetics would inhibit TXA(2)-receptor signaling. We used fluorometric determination of intracellular [Ca(2+)] in human K562 cells and 2-electrode voltage clamp measurements in Xenopus laevis oocytes expressing TXA(2) receptors. After 10-min incubation, lidocaine (IC(50): 1.02 +/- 0.2 x 10(-3) M), ropivacaine (IC(50): ropivacaine 6.3 +/- 0.9 x 10(-5) M), or bupivacaine (IC(50): 1.42 +/- 0.08 x 10(-7) M) inhibited TXA(2)-induced [Ca(2+)](i) in K562 cells. These data were confirmed in Xenopus oocytes recombinantly expressing TXA(2) receptors, with IC(50)s of bupivacaine 1.2 +/- 0.2 x 10(-5) M, R(+) ropivacaine 4.9 +/- 1.7 x 10(-4) M, S(-) ropivacaine 5.3 +/- 0.9 x 10(-5) M, and lidocaine 6.4 +/- 2.8 x 10(-4) M. Intracellular pathways activated by IP(3) and GTPgammaS were not significantly affected by the local anesthetics tested. QX314, a positively charged lidocaine analog, inhibited only if injected intracellularly (IC(50): 5.3 +/- 1.7 x 10(-4) M), indicating one local anesthetic target is most likely inside the cell. Benzocaine (largely uncharged) inhibited with an IC(50) of 8.7 +/- 1.8 x 10(-4) M. This suggests that some of the beneficial effects of regional anesthesia techniques might be due to direct interaction of local anesthetics with the functioning of membrane proteins.

Modulation of Xenopus laevis Ca-activated Cl currents by protein kinase C and protein phosphatases: implications for studies of anesthetic mechanisms.

Ca-activated Cl currents (I(Cl(Ca))) are used frequently as reporters in functional studies of anesthetic effects on G protein-coupled receptors using Xenopus laevis oocytes. However, because anesthetics affect protein kinase C (PKC), they could indirectly affect I(Cl(Ca)) if this current is regulated by phosphorylation. We therefore studied the effect of modulation of either PKC or protein phosphatases PP1alpha and PP2A on I(Cl(Ca)) stimulated either by lysophosphatidate (LPA) signaling or by microinjection of Ca. X. laevis oocytes were studied under voltage clamp. Rat PP1alpha and PP2A were overexpressed in oocytes. PP, inositoltrisphosphate (IP(3)), the PP inhibitor okadaic acid (OA), the PKC inhibitor chelerythrine, or CaCl(2) were directly injected into the oocyte. Responses to agonists (LPA 10(-6) M, IP(3) 10(-4) M, CaCl(2) 0.5 M) were measured at a holding potential of -70 mV in the presence or absence of the PP inhibitors cantharidin or OA. PP1 alpha and PP2A inhibited I(Cl(Ca)) from 7.6 +/- 0.9 microC to 2.5 +/- 0.9 microC and 3.2 +/- 1.4 microC, respectively. PP inhibition enhanced I(Cl(Ca)) in control oocytes and reversed the inhibitory effect in oocytes expressing PP1 alpha or PP2A. PKC inhibition by chelerythrine enhanced both LPA- and CaCl(2)-induced I(Cl(Ca)). Our data indicate that the Xenopus I(Cl(Ca)) is modulated by phosphorylation. This may complicate design and interpretation of studies of G protein-coupled receptors using this model.