Risk factors associated with intraoperative shivering during caesarean section: a prospective nested case-control study.

BACKGROUND: To study the incidence and risk factors of shivering in pregnant women during cesarean section. METHODS: We performed a prospective nested case-control study involving parturients scheduled for cesarean sections between July 2018 and May 2021. The overall incidence of intraoperative shivering and its potential risk factors were investigated. The potential risk factors evaluated were pain, anxiety, emergency surgery, transfer from the delivery room, epidural labor analgesia, membrane rupture, labor, and the timing of the surgery. Shivering and body temperature at different time points during the cesarean section were also recorded. The selected seven time points were: entering the operating room, post-anesthesia, post-disinfection, post-delivery, post-oxytocin, post additional hysterotonics, and before leaving the operating room. RESULTS: We analyzed 212 cesarean section parturients. The overall incidence of shivering was 89 (42.0%). Multivariate logistic regression showed that anxiety, emergency delivery, and transfer from the delivery room to the operating room increased the overall shivering incidence (odds ratio = 1.77, 2.90, and 3.83, respectively). The peak shivering incidence occurred after skin disinfection (63, 29.7%), and the lowest body temperature occurred after oxytocin treatment (36.24 ± 0.30 °C). Stratified analysis of surgery origin showed that emergency delivery was a risk factor for shivering (odds ratio = 2.99) in women transferred from the obstetric ward to the operating room. CONCLUSION: Shivering occurred frequently during cesarean sections, with the peak incidence occurring after skin disinfection. Anxiety, emergency delivery, and transfer from the delivery room to the operating room increased the risk of shivering development during cesarean sections. TRIAL REGISTRATION: The study protocol was registered online at China Clinical Registration Center (registration number: ChiCTR-ROC-17010532, Registered on 29 January 2017).

High concentration in situ polymer gel electrolyte for high performance lithium metal batteries.

A high concentration gel polymer electrolyte (GPE) was prepared by simply using LiFSI-LiNO3 dissolved in 1,3-dioxolane. The Li‖Li cell achieves stable battery cycling for over 3200 h. Furthermore, the Li‖Cu cell demonstrates a high CE of 99.2%. Even at a high current density of 8 mA cm-2, a high CE of 98.5% was still achieved. Notably, in a Li‖LiFePO4 cell, this electrolyte enables high capacity retention of 94.5% and an average CE of 99.8% over 500 cycles, showing promising prospects for high-performance lithium metal batteries.

Rational construction of graphitic carbon nitride composited Li-rich Mn-based oxide cathode materials toward high-performance Li-ion battery.

Li-rich Mn-based oxides (LRMOs) are considered as one of the most-promising cathode materials for next generation Li-ion batteries (LIBs) because of their high energy density. Nevertheless, the intrinsic shortcomings, such as the low first coulomb efficiency, severe capacity/voltage fade, and poor rate performance seriously limit its commercial application in the future. In this work, we construct successfully g-C3N4 coating layer to modify Li1.2Mn0.54Ni0.13Co0.13O2 (LMNC) via a facile solution. The g-C3N4 layer can alleviate the side-reaction between electrolyte and LMNC materials, and improve electronic conduction of LMNC. In addition, the g-C3N4 layer can suppress the collapse of structure and improve cyclic stability of LMNC materials. Consequently, g-C3N4 (4 wt%)-coated LMNC sample shows the highest initial coulomb efficiency (78.5%), the highest capacity retention ratio (78.8%) and the slightest voltage decay (0.48 V) after 300 loops. Besides, it also can provide high reversible capacity of about 300 and 93 mAh g-1 at 0.1 and 10C, respectively. This work proposes a novel approach to achieve next-generation high-energy density cathode materials, and g-C3N4 (4 wt%)-coated LMNC shows an enormous potential as the cathode materials for next generation LIBs with excellent performance.

A long-life lithium-oxygen battery via a molecular quenching/mediating mechanism.

The advancement of lithium-oxygen (Li-O2) batteries has been hindered by challenges including low discharge capacity, poor energy efficiency, severe parasitic reactions, etc. We report an Li-O2 battery operated via a new quenching/mediating mechanism that relies on the direct chemical reactions between a versatile molecule and superoxide radical/Li2O2. The battery exhibits a 46-fold increase in discharge capacity, a low charge overpotential of 0.7 V, and an ultralong cycle life >1400 cycles. Featuring redox-active 2,2,6,6-tetramethyl-1-piperidinyloxy moieties bridged by a quenching-active perylene diimide backbone, the tailor-designed molecule acts as a redox mediator to catalyze discharge/charge reactions and serves as a reusable superoxide quencher to chemically react with superoxide species generated during battery operation. The all-in-one molecule can simultaneously tackle issues of parasitic reactions associated with superoxide radicals, singlet oxygen, high overpotentials, and lithium corrosion. The molecular design of multifunctional additives combining various capabilities opens a new avenue for developing high-performance Li-O2 batteries.

A high efficiency electrolyte enables robust inorganic-organic solid electrolyte interfaces for fast Li metal anode.

Developing a high-rate Li metal anode with superior reversibility is a prerequisite for fast-charging Li metal batteries. However, the build-up of large concentration gradients under high current density leads to inhomogeneous Li deposition and unstable passivation layers of Li metal, resulting in lower Coulombic efficiency. Here we report a concentrated dual-salts LiFSI-LiNO3/DOL electrolyte to improve the high-rate performance of Li metal anode. Sufficient Li salts help passivate the fresh Li deposition quickly. Further, DOL contributes to the formation of flexible organic layers that can accommodate the rapid volume change of Li metal upon cycling. Li metal in the electrolyte remains stable over 240 cycles with the average Coulombic efficiency of 99.14% under a high current density of 8.0 mA cm-2.

Identifying Anionic Redox Activity within the Related O3- and P2-Type Cathodes for Sodium-Ion Battery.

As promising cathodes for Na-ion batteries (NIBs), layered transition-metal (TM) oxides have attracted intense research activities because of high specific capacities, especially benefiting from the boosted capacity triggered by oxygen-related anionic redox reactions (ARRs). However, regarding ARRs activity, the difference between typical O3- and P2-type structures has not been clarified with in-depth exploration. Herein, composed with similar composition, ARRs-induced oxygen behaviors within O3-Na0.6Li0.2Fe0.4Ru0.4O2 and P2-Na0.6Li0.35Fe0.1Ru0.55O2 are systematically investigated by varying ex/in situ spectroscopic characterizations. Conducted with a lower charging cutoff voltage (4.0 V), P2-type cathode will more easily trigger the reversible oxygen behaviors and deliver a larger capacity, better rate performance, and stable cyclability, in contrast to the O3-type cathode. Moreover, within O3-type structure, increasing charging potential (beyond 4.3 V) would induce additional anionic oxidation capacity, but inevitably lead to the irreversible evolution of gaseous O2 and superoxo. With the unique feature, this work provides a promising strategy design for fabricating cathodes with optimal microstructural arrangement, which could further push forward the changes in macro-/nanostructures and even ideal performance.

Improving the structural and cyclic stabilities of P2-type Na0.67MnO2 cathode material via Cu and Ti co-substitution for sodium ion batteries.

An air-stable Na0.67Mn0.7Cu0.15Ti0.15O2 (NMCT) has been synthesized using a solid-state method. It displays a reversible capacity of 170 mA h g-1 and a capacity retention of 82.5% after 300 cycles. NMCT also exhibits good structural stability upon electrochemical de/intercalation processes as observed by operando XRD. And the result shows that the unit-cell volume change of NMCT during the whole process of Na+ de/intercalation is only 3.2%. These data indicate that NMCT is a promising cathode material for sodium ion batteries (SIBs).

NonAqueous, Metal-Free, and Hybrid Electrolyte Li-Ion O2 Battery with a Single-Ion-Conducting Separator.

The rechargeable lithium-oxygen (Li-O2) batteries suffer from not only the low practical capacity and high overpotential at the oxygen cathode but also the low lithium utilization and dendrite growth of the Li metal. In this work, by coupling the dual mediator catholyte and the carbonate-based anolyte for the high specific capacity Si anode, we propose a hybrid electrolyte design for the fabrication of Li-ion O2 batteries. A single-ion-conducting lithiated Nafion membrane is introduced to bridge the two electrolyte systems. Benefiting from the restraint of mediator shuttling and the uniform solid electrolyte interface film of silicon anode, the hybrid electrolyte Li-ion O2 battery exhibits high reversible capacity, low overpotential, and improved cycling stability. Beyond the Li-ion O2 battery, the hybrid electrolyte design shows great potential for the development of stable battery systems with high energy efficiency.

Efficacy and Safety of Different Norepinephrine Regimens for Prevention of Spinal Hypotension in Cesarean Section: A Randomized Trial.

The aim of this paper is to evaluate the efficacy and safety of three different norepinephrine dosing regimens for preventing spinal hypotension in cesarean section. In this randomized double-blinded controlled study, 120 parturients scheduled for elective section delivery under spinal anesthesia were assigned to 1 of 4 groups. In the control group, patients received saline infusion. In three norepinephrine groups, the infusion dosage regimens were 5, 10, and 15 µg/kg/h, respectively. Hypotension was treated with a rescue bolus of 10 µg norepinephrine. The study protocol was continued until the end of surgery. The primary outcome was the proportion of participants that underwent hypotension. The proportion of hypotension participants was significantly reduced in the norepinephrine groups (37.9%, 20%, and 25%, respectively) compared to that in the control group (86.7%). However, the highest dose of norepinephrine (15 µg/kg/h) resulted in more hypertension episodes. In addition, blood pressure was better maintained in the norepinephrine 5 µg/kg/h and 10 µg/kg/h groups than in the control group and 15 µg/kg/h group. No significant differences in other hemodynamic variables, adverse effects, maternal and neonatal blood gases, or Apgar scores were observed among the groups. In summary, for patients who undergo cesarean delivery under spinal anesthesia, infusion of 5-10 µg/kg/h norepinephrine was effective to reduce hypotension incidence without significant adverse effects on maternal and neonatal outcomes. Clinical Trial Registration Number is ChiCTR-INR-16009452.

A lithium-ion oxygen battery with a Si anode lithiated in situ by a Li3N-containing cathode.

A practicable strategy has been developed to build a LixSi-O2 battery using an in situ formed Li-Si alloy anode based on the decomposition of Li3N pre-loaded in the cathode. The LixSi-O2 battery has achieved more than 100 stable charge-discharge cycles with lower polarization than that using a lithium metal anode.

Ordered mesoporous TiC-C composites as cathode materials for Li-O2 batteries.

Ordered mesoporous TiC-C (OMTC) composites were prepared and served as catalysts for nonaqueous Li-O2 batteries. The OMTC cathodes showed high specific capacity, low overpotential and good cyclability. Furthermore, the reaction mechanism of Li-O2 batteries during charge and discharge processes was investigated extensively by XRD, XPS and in situ GC-MS methods.