Milton Dante Galicia Esparza

Hypoxia is a complex multisystemic condition characterized by insufficient oxygen availability at the tissue level, producing progressive dysfunction involving the pulmonary, cardiovascular, and neurological systems. Although traditionally associated with respiratory failure, contemporary evidence demonstrates that hypoxia activates interconnected physiological, inflammatory, vascular, metabolic, and neurological pathways capable of generating widespread systemic injury. The objective of this review was to analyze the principal mechanisms through which hypoxia contributes to pulmonary, cardiovascular, and neurological dysfunction, emphasizing the integrated interactions between these systems and their clinical implications in modern medicine. This review was developed using a structured narrative methodology based on scientific literature indexed in international databases including PubMed, Scopus, Google Scholar, Europe PMC, Elsevier, and SpringerLink. The investigation integrated evidence from pulmonology, cardiology, neurology, critical care medicine, and vascular physiology in order to evaluate the systemic consequences of acute, chronic, and intermittent hypoxia. Special attention was given to molecular mechanisms such as hypoxia-inducible factor activation, oxidative stress, endothelial dysfunction, autonomic imbalance, mitochondrial injury, inflammatory cytokine release, and vascular remodeling. The findings demonstrate that pulmonary dysfunction initiates hypoxemia through mechanisms including ventilation-perfusion mismatch, diffusion impairment, hypoventilation, and shunt physiology. Cardiovascular adaptation initially attempts to preserve oxygen delivery through sympathetic activation and pulmonary vasoconstriction; however, prolonged hypoxic exposure contributes to pulmonary hypertension, right ventricular overload, endothelial dysfunction, arrhythmogenic instability, and impaired systemic perfusion. Neurological consequences include neuroinflammation, excitotoxicity, cognitive impairment, cerebral autoregulatory dysfunction, and hypoxic-ischemic injury due to the high metabolic vulnerability of neuronal tissue. Intermittent hypoxia, particularly in obstructive sleep apnea, was associated with substantial cardiovascular and neurocognitive consequences related to oxidative stress and autonomic dysregulation.

Neuroinflammation has emerged as a fundamental pathophysiological mechanism linking neurological disorders with systemic inflammatory diseases. Increasing evidence demonstrates that chronic immune activation contributes significantly to neuronal dysfunction, cognitive impairment, neurodegeneration, and multisystem clinical manifestations through complex interactions involving microglial activation, cytokine signaling, oxidative stress, endothelial dysfunction, mitochondrial injury, and blood–brain barrier disruption. The objective of this review was to analyze the role of neuroinflammation as an interdisciplinary bridge between neurology, immunology, and internal medicine while evaluating its clinical, molecular, and translational implications. A narrative review methodology based on the Scientific Method and Process-Based Methodology was employed. Scientific literature indexed in international databases including PubMed, Scopus, ScienceDirect, SpringerLink, and Frontiers was analyzed. The review prioritized peer-reviewed studies published primarily between 2020 and 2025 addressing neuroimmune communication, neurodegeneration, metabolic disorders, autoimmune diseases, infectious syndromes, and gut–brain axis interactions. The analyzed evidence demonstrated that neuroinflammatory mechanisms are strongly associated with metabolic diseases such as obesity and type 2 diabetes mellitus, autoimmune disorders including systemic lupus erythematosus, infectious conditions such as sepsis and long COVID syndrome, and neurodegenerative diseases. Persistent inflammatory activation was consistently related to cognitive impairment, chronic fatigue, depression, autonomic dysfunction, chronic pain, and progressive neuronal injury. Furthermore, the gut–brain axis emerged as a major regulator of neuroimmune communication, reinforcing the systemic nature of neuroinflammation.

The kidney has traditionally been recognized as an organ responsible for filtration and homeostasis; however, recent evidence highlights its role as a sensitive sensor capable of detecting early systemic alterations. This review analyzes the function of the kidney as a sensor organ through the evaluation of renal biomarkers, with a particular focus on pediatric populations and their interaction with gastrointestinal diseases. A structured narrative review methodology was applied, integrating evidence from nephrology, internal medicine, pediatrics, and gastroenterology. Emerging biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), interleukin-18 (IL-18), and cystatin C demonstrate greater sensitivity for early detection of renal and systemic alterations compared to traditional markers such as serum creatinine. These biomarkers reflect different pathophysiological mechanisms, including tubular injury, inflammation, and glomerular dysfunction, allowing for a multidimensional assessment of disease processes. The findings also emphasize the relevance of the gut–kidney axis, where gastrointestinal conditions such as dehydration, inflammatory bowel disease, liver dysfunction, and dysbiosis can induce early renal responses. This relationship is particularly significant in pediatric patients, where systemic disturbances may progress rapidly and remain clinically silent in early stages.