Noninvasive CA Monitoring Validation and Autonomic Modulation in Aneurysmal Subarachnoid Hemorrhage

This is a two-component prospective study of adult aneurysmal subarachnoid hemorrhage (aSAH) patients admitted to the Neurosciences Intensive Care Unit (NSICU) at UT Southwestern Medical Center. Component 1 (active upon IRB approval) validates Brain4Care (B4C) extensometry-derived noninvasive cerebral autoregulation (CA) indices against invasive ICP-derived equivalents in aSAH patients with open external ventricular drains (EVDs), and characterizes the prospective natural history of multi-modal CA parameter evolution through the delayed cerebral ischemia (DCI) window (admission through Day 14). Component 2 (activated upon PI readiness declaration) assesses the within-subject effect of cervical sympathetic block (CSB) and transcutaneous auricular vagal nerve stimulation (taVNS) on CA parameters in enrolled aSAH patients.

Inclusion Criteria (Component 1 - All Enrolled Participants): * Age 18 years or older * Primary diagnosis of aneurysmal subarachnoid hemorrhage (aSAH), confirmed by imaging * Admitted to the NSICU at Clements University Hospital, UT Southwestern Medical Center * Informed consent obtained from subject or legally authorized representative (as defined under Texas Health and Safety Code Section 166.039) * Brain4Care extensometry sensor placeable at an appropriate cranial site not occluded by surgical dressings or EVD hardware * Open EVD with active continuous ICP monitoring (required for EVD clamping sub-protocol only; not required for Aims 2 or 3) Exclusion Criteria (Component 1): * Age younger than 18 years * Prisoner status * Primary NSICU admission diagnosis other than aSAH * Active declination by subject or legally authorized representative * Brain4Care sensor not placeable at any accessible cranial site * Active clinical deterioration making research monitoring impractical at time of approach * Physician-of-record declining research enrollment for clinical reasons * Inability to provide informed consent in English * Known pregnancy at time of enrollment Additional Inclusion Criteria for Component 2 (Aim 3 - CSB and taVNS): * At least one successful EVD clamping session completed * PI documentation of Component 2 operational readiness, co-signed by qualified co-investigator or Department Director * INR 1.5 or less and platelet count 50,000/uL or greater within 24 hours prior to each CSB procedure * No active infection or cellulitis at right anterolateral neck * No known allergy to ropivacaine or amide local anesthetics * No contralateral phrenic nerve palsy or severe pre-existing respiratory compromise * No cardiac pacemaker or implanted cardiac device contraindicating taVNS * No allergy to electrode adhesive materials * Continuous cardiac telemetry active and interpretable * Resting HR 60 bpm or greater on two readings within 24 hours prior to session * No current use of Class I or III antiarrhythmic medications * No clinically significant AV conduction abnormality Additional Exclusion Criteria for Component 2: * Prior ipsilateral right-sided cervical surgery, radiation, or known anatomical distortion precluding safe C6 approach * Hemodynamic instability with active vasopressor escalation at time of planned CSB * Active uncontrolled tachyarrhythmia or bradyarrhythmia at time of taVNS session * Physician-of-record declining autonomic modulation procedures for any clinical reason * Known or suspected pregnancy