Background: Cerebral circulation is profoundly affected by changes in PaCO2. CO2 manipulation plays a basic role in the management of intracranial hypertension; CO2 reactivity (CO2R) defines the changes in CBF in response to changes in PaCO2. Transcranial Doppler has allowed exploring its effects "on line".
Materials And Methods: We conducted a prospective clinical trial, with the objective of studying CO2R in severe head injury patients. Sixteen severe traumatic brain injury patients, mechanically ventilated, were included. Monitoring of MAP, ICP, CPP, SjO2, ETCO2, and cerebral blood flow velocity (CBFV) was performed. Taking into account basal cerebral hemodynamic pattern, minute ventilation was modified to attain a negative ("A") or positive ("B") deltaPCO2. CO2R was calculated as: CO2R = % deltaCBFV/deltaETCO2 in mmHg (normal value 3.7 +/- 1%/mmHg). CO2R was compared with deltaICP/ deltaPCO2 in each patient.
Findings: Three patients were excluded because the change in ETCO2 was too low (deltaETCO2 < 3 mmHg). The median value of CO2R in the total group of 13 patients was 3.38. In "A" the values tended to be lower than in "B". There were four low CO2R values in "A" and none in "B". There was no significant correlation between CO2R and deltaICP/deltaPCO2.
Conclusions: The different "A" and "B" behavior might be due to dissimilar mechanisms involved in the basis of vasodilatation and vasoconstriction. Changes in ventilation must be performed with caution, avoiding sudden increases in CO2 that may increase ICP. The absence of correlation between CO2R and deltaICP/deltaPCO2 is explained, at least partially, by different cranio-cerebral compliance in each patient. Therefore, induced blood volume changes are not directly transmitted to ICP, but their effects depend on the shape of the pressure-volume curve and the position on the curve in which each situation is working.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1007/978-3-211-85578-2_34 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Integrated system for electrolyte recovery, product separation, and CO capture in CO reduction.
Nat Commun
January 2025
School of Environment and Energy, State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, National Engineering Laboratory for VOCs Pollution Control Technology and Equipment, South China University of Technology, Guangzhou, 510006, China.
Challenges in CO capture, CO crossover, product separation, and electrolyte recovery hinder electrocatalytic CO reduction (COR). Here, we present an integrated electrochemical recovery and separation system (ERSS) with an ion separation module (ISM) between the anode and cathode of a water electrolysis system. During ERSS operation, protons from the anolyte flow through the anodic cation exchange membrane (CEM) into the ISM, acidifying the COR effluent electrolyte.
View Article and Find Full Text PDFGraphene-based single-atom catalysts for electrochemical CO reduction: unraveling the roles of metals and dopants in tuning activity.
Phys Chem Chem Phys
January 2025
Department of Chemical Engineering, Northeastern University, Boston, Massachusetts, 02115, USA.
Discovering electrocatalysts that can efficiently convert carbon dioxide (CO) to valuable fuels and feedstocks using excess renewable electricity is an emergent carbon-neutral technology. A single metal atom embedded in doped graphene, , single-atom catalyst (SAC), possesses high activity and selectivity for electrochemical CO reduction (COR) to CO, yet further reduction to hydrocarbons is challenging. Here, using density functional theory calculations, we investigate stability and reactivity of a broad SAC chemical space with various metal centers (3d transition metals) and dopants (2p dopants of B, N, O; 3p dopants of P, S) as electrocatalysts for COR to methane and methanol.
View Article and Find Full Text PDFConstraining CO Coverage on Copper Promotes CO Electroreduction to Multi-carbon Products in Strong Acid.
Angew Chem Int Ed Engl
December 2024
Department of Chemistry, City University of Hong Kong, Hong Kong SAR, 999077, PR China.
Electrocatalytic CO reduction (COR) to multi-carbon (C) products in strong acid presents a promising approach to mitigate the CO loss commonly encountered in alkaline and neutral systems. However, this process often suffers from low selectivity for C products due to the competing C (e.g.
View Article and Find Full Text PDFSolar-Driven Sulfide Oxidation Paired With CO Reduction Based on Vacancies Engineering of Copper Selenide.
Small
December 2024
Institute of Photoelectronic Thin Film Devices and Technology, Renewable Energy Conversion and Storage Center, State Key Laboratory of Photovoltaic Materials and Cells, Nankai University, Tianjin, 300350, P. R. China.
Photovoltaic-driven electrochemical (PV-EC) carbon dioxide reduction (COR) coupled with sulfide oxidation (SOR) can efficiently convert the solar energy into chemical energy, expanding its applications. However, developing low-cost electrocatalysts that exhibit high selectivity and efficiency for both COR and SOR remains a challenge. Herein, a bifunctional copper selenide catalyst is developed with copper vacancies (v-CuSe) for the COR-SOR.
View Article and Find Full Text PDFIn Situ Transmission Electron Microscopy of Electrocatalyst Materials: Proposed Workflows, Technical Advances, Challenges, and Lessons Learned.
Small Methods
January 2025
Department of Chemical Engineering, McMaster University, Hamilton, ON, L8S 4L7, Canada.
In situ electrochemical liquid phase transmission electron microscopy (LP-TEM) measurements utilize micro-chip three-electrode cells with electron transparent silicon nitride windows that confine the liquid electrolyte. By imaging electrocatalysts deposited on micro-patterned electrodes, LP-TEM provides insight into morphological, phase structure, and compositional changes within electrocatalyst materials under electrochemical reaction conditions, which have practical implications on activity, selectivity, and durability. Despite LP-TEM capabilities becoming more accessible, in situ measurements under electrochemical reaction conditions remain non-trivial, with challenges including electron beam interactions with the electrolyte and electrode, the lack of well-defined experimental workflows, and difficulty interpreting particle behavior within a liquid.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!