Continuous non-invasive vs. invasive arterial blood pressure monitoring during neuroradiological procedure: a comparative, prospective, monocentric, observational study.

BACKGROUND: In the perioperative setting, the most accurate way to continuously measure arterial blood pressure (ABP) is using an arterial catheter. Surrogate methods such as finger cuff have been developed to allow non-invasive measurements and are increasingly used, but need further evaluation. The aim of this study is to evaluate the accuracy and clinical concordance between two devices for the measurement of ABP during neuroradiological procedure. METHODS: This is a prospective, monocentric, observational study. All consecutive patients undergoing a neuroradiological procedure were eligible. Patients who needed arterial catheter for blood pressure measurement were included. During neuroradiological procedure, ABP (systolic, mean and diatolic blood pressure) was measured with two different technologies: radial artery catheter and Nexfin. Bland-Altman and error grid analyses were performed to evaluate the accuracy and clinical concordance between devices. RESULTS: From March 2022 to November 2022, we included 50 patients, mostly ASA 3 (60%) and required a cerebral embolization (94%) under general anaesthesia (96%). Error grid analysis showed that 99% of non-invasive ABP measures obtained with the Nexfin were located in the risk zone A or B. However, 65.7% of hypertension events and 41% of hypotensive events were respectively not detected by Nexfin. Compared to the artery catheter, a significant relationship was found for SAP (r2 = 0.78) and MAP (r2 = 0.80) with the Nexfin (p < 0.001). Bias and limits of agreement (LOA) were respectively 9.6 mmHg (- 15.6 to 34.8 mmHg) and - 0.8 mmHg (- 17.2 to 15.6 mmHg), for SAP and MAP. CONCLUSIONS: Nexfin is not strictly interchangeable with artery catheter for ABP measuring. Further studies are needed to define its clinical use during neuroradiological procedure. TRIAL REGISTRATION: Clinicaltrials.gov, registration number: NCT05283824.

Inhibition of the ventral midline thalamus does not alter encoding, short-term holding or retrieval of spatial information in rats performing a water-escape working memory task.

Working memory (WM) is a function operating in three successive phases: encoding (sample trial), holding (delay), and retrieval (test trial) of information. Studies point to a possible implication of the thalamic reuniens nucleus (Re) in spatial WM (SWM). In which of the aforementioned 3 phases the Re has a function is largely unknown. Recently, in a delayed SWM water-escape task, we found that performance during the retrieval trial correlated positively with c-Fos expression in the Re nucleus, suggesting participation in retrieval. Here, we used the same task and muscimol (MUSC) inhibition or DREADD(hM4Di)-mediated inhibition of the Re during information encoding, right thereafter (thereby affecting the holding phase), or during the retrieval trial. A 6-hour delay separated encoding from retrieval. Concerning SWM, MUSC in the Re nucleus did not alter performance, be it during or after encoding, or during evaluation. CNO administered before encoding in DREADD-expressing rats was also ineffective, although CNO-induced inhibition disrupted set shifting performance, as found previously (Quet et al., Brain Struct Function 225, 2020), thereby validating DREADD efficiency. These findings are the first that do not support an implication of the Re nucleus in SWM. As most previous studies used T-maze alternation tasks, which carry high proactive interference risks, an important question to resolve now is whether the Re nucleus is required in (T-maze alternation) tasks using very short information-holding delays (seconds to minutes), and less so in other short-term spatial memory tasks with longer information holding intervals (hours) and therefore reduced interference risks.

Ventral midline thalamus activation is correlated with memory performance in a delayed spatial matching-to-sample task: A c-Fos imaging approach in the rat.

The reuniens (Re) and rhomboid (Rh) nuclei of the ventral midline thalamus are bi-directionally connected with the hippocampus and the medial prefrontal cortex. They participate in a variety of cognitive functions, including information holding for seconds to minutes in working memory tasks. What about longer delays? To address this question, we used a spatial working memory task in which rats had to reach a platform submerged in water. The platform location was changed every 2-trial session and rats had to use allothetic cues to find it. Control rats received training in a typical response-memory task. We interposed a 6 h interval between instruction (locate platform) and evaluation (return to platform) trials in both tasks. After the last session, rats were killed for c-Fos imaging. A home-cage group was used as additional control of baseline levels of c-Fos expression. C-Fos expression was increased to comparable levels in the Re (not Rh) of both spatial memory and response-memory rats as compared to their home cage counterparts. However, in spatial memory rats, not in their response-memory controls, task performance was correlated with c-Fos expression in the Re: the higher this expression, the better the performance. Furthermore, we noticed an activation of hippocampal region CA1 and of the anteroventral nucleus of the rostral thalamus. This activation was specific to spatial memory. The data point to a possible performance-determinant participation of the Re nucleus in the delayed engagement of spatial information encoded in a temporary memory.

The reuniens and rhomboid nuclei are necessary for contextual fear memory persistence in rats.

Memory persistence refers to the process by which a temporary, labile memory is transformed into a stable and long-lasting state. This process involves a reorganization of brain networks at systems level, which requires functional interactions between the hippocampus (HP) and medial prefrontal cortex (mPFC). The reuniens (Re) and rhomboid (Rh) nuclei of the ventral midline thalamus are bidirectionally connected with both regions, and we previously demonstrated their crucial role in spatial memory persistence. We now investigated, in male rats, whether specific manipulations of ReRh activity also affected contextual and cued fear memory persistence. We showed that the permanent ReRh lesion impaired remote, but not recent contextual fear memory. Tone-cued recent and remote fear memory were spared by the lesion. In intact rats, acute chemogenetic ReRh inhibition conducted before recall of either recent or remote contextual fear memories produced no effect, indicating that the ReRh nuclei are not required for retrieval of such memories. This was also suggested by a functional cellular imaging approach, as retrieval did not alter c-fos expression in the ReRh. Collectively, these data are compatible with a role for the ReRh in 'off-line' consolidation of a contextual fear memory and support the crucial importance of ventral midline thalamic nuclei in systems consolidation of memories.