Hyperventilation Syndrome in a Child: Electrolyte Disturbances and Cardiac Involvement in Anxiety-Related Presentations

<b>Background:</b> Hyperventilation Syndrome (HVS) is a well-recognized physiological consequence of acute anxiety, often resulting in respiratory alkalosis and subsequent electrolyte imbalances. Among these, a reduction in ionized calcium levels can lead to neuromuscular irritability and electrocardiographic abnormalities such as QTc prolongation. Although well-documented in specific settings, including autism spectrum disorders and drug-induced crises, such complications are rarely described in otherwise healthy pediatric patients presenting with isolated anxiety episodes. This report aims to raise awareness of anxiety-driven somatic manifestations, particularly in the context of the rising prevalence of mental health disorders among children and adolescents. <b>Methods:</b> We report the case of a previously healthy 10-year-old girl presenting to the emergency department with acute agitation and hyperventilation. Clinical examination revealed neuromuscular symptoms, including Trousseau's sign and flexion posture. Initial laboratory testing and arterial blood gas analysis indicated respiratory alkalosis with decreased ionized calcium levels, and a resting ECG showed QTc prolongation (510 ms). Treatment included intravenous midazolam, a balanced electrolyte solution, and oral bromazepam during intensive observation with cardiac monitoring. <b>Results:</b> The patient's symptoms progressively improved following anxiolytic and supportive therapy. Electrolyte abnormalities normalized within 48 h, with complete resolution of the prolonged QTc (430 ms). No arrhythmias or other complications occurred. Outpatient psychological follow-up was arranged upon discharge. <b>Conclusions:</b> This case underscores the importance of considering anxiety as a primary etiology in pediatric patients with apparent metabolic or cardiac abnormalities. Early psychiatric recognition and targeted supportive care can prevent overtreatment and reduce the burden on emergency and cardiologic resources.