Hyperosmolarity in children with hyperammonemia: a risk of brain herniation at the start of renal replacement therapy.

Purpose: Renal replacement therapy (RRT) is used in hyperammonemia to reduce the concentration of ammonia in the blood. In the case of plasma hyperosmolarity, RRT can also rapidly decrease plasma osmolarity, which may increase cerebral edema in these patients and favor the occurrence of brain herniation. Methods: We conducted a retrospective clinical study in a tertiary care university-affiliated hospital. All patients admitted in a Pediatric Intensive Care Unit (PICU), less than 18 years old with ammonemia >150 µmol/L and who underwent RRT between January 2015 and June 2023 were included. We collected data on plasma osmolarity levels, osmolar gap and blood ammonia levels before and during RRT. Results: Eleven patients were included (10 with acute liver failure and 1 with a urea cycle disorders). Their mean age was 36.2 months. Before RRT, the median highest measured osmolarity was 320 (305-324) mOsm/L, whereas the median calculated osmolarity was 303 (293-314) mOsm/L, corresponding to an osmolar gap of 14 mOsm/L. Ammonia blood level over 400 µmol/L are significantly associated with higher plasma osmolarity (P-Value <0.001). In one case, a patient had a brain herniation episode after a quick osmolar drop. This episode was reversed by the administration of hyperosmolar agents and the temporary suspension of RRT. Conclusion: This study highlights the hyperosmolarity and high osmolar gap that occur in children with hyperammonemia. A careful monitoring and control of plasma osmolarity evolution may alert clinician on the risk of occurrence of neurological complication such as brain herniation.

Probing pathways by which rhynchophylline modifies sleep using spatial transcriptomics.

BACKGROUND: Rhynchophylline (RHY) is an alkaloid component of Uncaria, which are plants extensively used in traditional Asian medicines. Uncaria treatments increase sleep time and quality in humans, and RHY induces sleep in rats. However, like many traditional natural treatments, the mechanisms of action of RHY and Uncaria remain evasive. Moreover, it is unknown whether RHY modifies key brain oscillations during sleep. We thus aimed at defining the effects of RHY on sleep architecture and oscillations throughout a 24-h cycle, as well as identifying the underlying molecular mechanisms. Mice received systemic RHY injections at two times of the day (beginning and end of the light period), and vigilance states were studied by electrocorticographic recordings. RESULTS: RHY enhanced slow wave sleep (SWS) after both injections, suppressed paradoxical sleep (PS) in the light but enhanced PS in the dark period. Furthermore, RHY modified brain oscillations during both wakefulness and SWS (including delta activity dynamics) in a time-dependent manner. Interestingly, most effects were larger in females. A brain spatial transcriptomic analysis showed that RHY modifies the expression of genes linked to cell movement, apoptosis/necrosis, and transcription/translation in a brain region-independent manner, and changes those linked to sleep regulation (e.g., Hcrt, Pmch) in a brain region-specific manner (e.g., in the hypothalamus). CONCLUSIONS: The findings provide support to the sleep-inducing effect of RHY, expose the relevance to shape wake/sleep oscillations, and highlight its effects on the transcriptome with a high spatial resolution. The exposed molecular mechanisms underlying the effect of a natural compound should benefit sleep- and brain-related medicine.