Neuraxial Anesthesia and CSF Dynamics

Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds the brain and spinal cord, providing nutrient delivery, structural support, and metabolic assistance. In addition to serving as a medium for nutrient and waste exchange, CSF is important for the proper functioning of neural tissues, as it helps maintain homeostasis in the central nervous system.¹ CSF plays a critical role in neuraxial anesthesia (which includes spinal anesthesia, epidural techniques, and combined spinal-epidural methods), since local anesthetics must travel and disperse within the CSF after injection. The volume and movement of CSF can significantly influence the spread and effectiveness of neuraxial anesthesia; for example, variations in CSF volume or velocity, and even patient positioning, can affect the strength or duration of the anesthetic block. Conversely, neuraxial techniques may cause changes to CSF parameters such as pressure or flow. As such, the study of CSF dynamics and neuraxial anesthesia is crucial for enhancing patient outcomes, particularly in high-risk populations.  

One such high-risk group is pregnant women, who face many anatomical and physiological changes. During pregnancy, CSF volume decreases and progesterone increases, influencing membrane excitability, neurotransmission, and neuronal sheath permeability.² A 2023 prospective, observational, single-center study included 26 women undergoing spinal anesthesia for cesarean section. CSF samples were collected prior to intrathecal administration of the anesthetic mixture: a combination of levobupivacaine, sufentanil, and morphine. The procedure was well tolerated by all patients, with few observed neurological complications or anesthesia-related adverse events. CSF analysis revealed normal physiological and chemical parameters, including median concentration of CSF/plasma glucose ratios, CSF lactate levels, and average CSF protein concentrations. No viral RNA was detected in CSF samples, and there were no signs of central nervous system dysfunction. These findings suggest spinal anesthesia is a safe and effective technique for cesarean delivery in pregnant women, with no significant effects on CSF dynamics.²

Tissue injury after major surgery provokes an inflammatory immune response pain and can lead to functional changes in the spinal cord.³ A prospective observational study measured pro-inflammatory and anti-inflammatory cytokine levels in CSF samples collected from orthopedic patients before and after anesthesia. IL-6 (a pro-inflammatory cytokine) and IL-10 (an anti-inflammatory cytokine) levels were measured with ELISA assays. Immediately after surgery, IL-6 levels increased significantly in patients receiving both general and spinal anesthesia; however, there was a notably smaller increase in IL-6 for patients who underwent spinal anesthesia.⁴ Minimal changes were reported for IL-10 levels across all study groups. In this study design, some patients received spinal anesthesia through a polyamide catheter, while others received spinal anesthesia through a single-injection puncture. Interestingly, although both groups received the same anesthetic and dosage, the increases in CSF IL-6 between the two groups were variable, with some patients exhibiting IL-6 levels an order of magnitude larger than others. This finding suggests that CSF dynamics in response to the mechanical effects of spinal anesthesia may vary across patients.⁴

CSF plays a central role in the effectiveness and safety of anesthesia, particularly spinal anesthesia, by influencing the distribution and duration of anesthetic agents. Variations in CSF volume, flow dynamics, and patient-specific physiological conditions can significantly impact the outcomes of neuraxial anesthesia, highlighting the importance of personalized approaches in clinical practice. Studies involving pregnant women have demonstrated that spinal anesthesia is safe even for this high-risk population, with no significant disruption to CSF composition or function. Research on inflammatory responses following surgery shows that spinal anesthesia may moderate the postoperative rise in pro-inflammatory cytokines like IL-6, suggesting a potential neuroprotective effect. These findings underscore the importance of continued investigation into CSF physiology and its interactions with anesthetic techniques to optimize care across diverse patient populations and surgical contexts.

References

1. Telano, Lauren N., and Stephen Baker. “Physiology, Cerebral Spinal Fluid.” StatPearls, StatPearls Publishing, 2025. http://www.ncbi.nlm.nih.gov/books/NBK519007/
2. Fierro, Giulia, et al. “Safety of Spinal Anesthesia and Analysis of Cerebrospinal Fluid in SARS-CoV-2 Pregnant Women Undergoing Cesarean Section: An Observational Prospective Study.” Journal of Anesthesia, Analgesia and Critical Care, 3(1), 2023, 49. https://doi.org/10.1186/s44158-023-00135-1
3. Rang, H.E., Urban, L. “New Molecules in Analgesia.” British Journal of Anaesthesiology, 75, 1995, 145-156.
4. Yeager, Mark P., et al. “Cerebrospinal Fluid Cytokine Levels after Surgery with Spinal or General Anesthesia.” Regional Anesthesia and Pain Medicine, 24(6), 1999, 557–562. ScienceDirect, https://doi.org/10.1016/S1098-7339(99)90049-4