Patients will receive a subcutaneous sham injection of saline

The SGB group will receive ropivacaine 0.5% 10ml

The control group will receive normal saline in the sham injection.

Change in heart rate variability (HRV) metrics (time and frequency domains) from baseline to first and second follow up visit

Measure the change in plasma catecholamine levels from baseline to first and second follow up visits

SPOTS evaluates the frequency and severity of common POTS symptoms, The higher the score, the greater the symptom burden. A reduction in SPOTS score suggests clinical improvement. SPOTS scores at 1st and 2nd FU are compared to baseline SPOTS scores.

Change in VOSS score at 1st and 2nd FU compared to baseline. The Vanderbilt Orthostatic Symptom Score (VOSS) is a tool used to assess and track the severity of symptoms associated with postural orthostatic tachycardia syndrome (POTS). It helps quantify a patient's symptom burden by having them rate the severity of 9 symptoms (mental clouding, blurred vision, shortness of breath, rapid heartbeat, tremulousness, chest discomfort, headache, lightheadedness, and nausea) on a scale of 0 to 10, where 0 indicates no symptoms.

Change in FSS score at 1st and 2nd FU compared to baseline. The Fatigue Severity Scale (FSS) is a questionnaire used to measure the severity of fatigue and its impact on daily activities. It's a 9-item scale where respondents rate their agreement with statements about fatigue using a 7-point scale, with 1 being "strongly disagree" and 7 being "strongly agree". The total FSS score is calculated by summing the responses, with a higher score indicating greater fatigue severity.

Change in the PROMIS Cognitive Function Short Form 6a score at 1st and 2nd FU compared to baseline. Short Form 6a is a six-item sub-set scale of the PROMIS (Patient Reported Outcomes Measurement Information System) Cognitive Function item bank that assesses patient-perceived cognitive deficits. The questions use a 5-point response scale, ranging from "Not at all" to "Very much". A higher score generally indicates better perceived cognitive ability.

Change in EQ-5D score at 1st and 2nd FU compared to baseline. The EQ-5D is a questionnaire for measuring patient-reported outcomes which assesses health-related quality of life across five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. The EQ-5D index score ranges from 0 to 1, where 1 represents perfect health, 0 represents a state as bad as death, and values between 0 and 1 represent different levels of health, with higher values indicating better health.

The PGI-S (Patient Global Impression of Severity) is a single-item, 7-point scale used to assess a patient's perception of the current severity of their condition. A rating of 1 indicates "normal, not at all ill," while a rating of 7 indicates "among the most extremely ill patients." This self-reported measure provides a global assessment of illness severity from the patient's perspective and is commonly used in clinical trials to gauge baseline condition or monitor progression over time.

The PGI-C (Patient Global Impression of Change) is a 7-point scale used to assess a patient's perceived change in their health or condition after an intervention. A rating of 1 indicates "very much improved," while a rating of 7 indicates "very much worse". It's a self-reported measure that reflects a patient's belief about the efficacy of treatment.

The CGI-S (Clinical Global Impression of Severity) is a 7-point scale used by clinicians to assess the severity of a patient's illness at a given point in time. A rating of 1 indicates "normal, not at all ill," while a rating of 7 indicates "among the most extremely ill patients." This clinician-rated measure provides an overall impression of the patient's current condition, based on clinical judgment and all available information, including patient history, symptoms, and behavior.

The Clinical Global Impression of Change (CGI-C) is a scale used to assess the clinical change or improvement in a patient's condition over time. CGI-C scores range from 1 (very much improved) through to 7 (very much worse).

Reduction in anxiety and depression symptoms as measured by the BAI score. Beck Anxiety Inventory (BAI) is a 21-item self-report questionnaire designed to assess the severity of anxiety symptoms. Each item is rated on a 4-point scale (0 = not at all to 3 = severely). The total score ranges from 0 to 63. Higher scores indicate greater severity of anxiety symptoms.

Reduction in anxiety and depression symptoms as measured by the BDI score. Beck Depression Inventory (BDI) is a 21-question multiple-choice self-report inventory for measuring the severity of depression. The total score ranges from 0 to 63. Higher total scores indicate more severe depressive symptoms.

Measure the change in adrenergic G-protein-coupled receptor autoantibody concentrations from baseline to first and second follow up visits from stored serum samples.

Measure the change in inflammatory markers concentrations (including but not limited to IL1, IL6, IL8, TNF) from baseline to first and second follow up visits from stored serum samples

Proportion of patients achieving Horner's syndrome post-SGB as a measure of block success

Measure the change in facial skin temperature (C°) post-procedure

Sweat testing will be performed following the procedure. The patient is coated with a moisture-sensitive powder that changes color following the increase in facial blood flow following the intervention.