Safety of low dose local anesthetics for Paroxysmal Sympathetic Dysfunction

Hypoxic–ischemic encephalopathy (HIE) occurs after global cerebral ischemia and can lead to outcomes ranging from persistent vegetative state to complete recovery. The management of HIE is multidisciplinary and offered to medically stable individuals. Paroxysmal Sympathetic Hyperactivity (PSH), also called Paroxysmal Autonomic Instability with Dystonia (PAID), occurs in 7–33% of HIE cases within the first three months. PSH presents with agitation, sweating, fever, high blood pressure, fast heart rate, rapid breathing, and extensor posturing. Standard drugs used include morphine, bromocriptine, propranolol, clonidine, lorazepam, and dantrolene, yet outcomes often remain poor with prolonged care and minimal functional gains. Neural therapy, which uses low-dose short-acting local anesthetics at autonomic structures, has shown promise in reducing autonomic dysfunction through blocks of the stellate ganglion or vagus nerve. The primary aim of this pilot study was to test the feasibility of such low-dose blocks in PSH, with secondary aims of assessing PSH score changes, DLT score, and treatment-related adverse events. The study was conducted in a tertiary rehabilitation center with ethics approval (ECASM-AIMS-2025-165, CTRI registered), and informed consent was obtained from families. Eligible patients had HIE within three months, were off ventilator and inotropes, had CRS-R scores between 3 and 8, radiological stage 3 injury, unresolved PSH for one week post-ICU, a DLT score of 5+, were on maximum tolerated propranolol, and had no active infection or comorbidities. Patients received six injections weekly for four weeks, with anesthetic blocks of the stellate and vagus nerves under ultrasound guidance, and outcomes were tracked using validated PSH and DLT scoring systems.