The goal of this observational study is to evaluate intravenous lidocaine efficacy and safety in treating headache following non-traumatic subarachnoid hemorrhage. Through this prospective analysis, the investigators hope to:

1. show that intravenous lidocaine infusion causes a clinically significant reduction in pain scores in patients with moderate/severe headache pain following non-traumatic subarachnoid hemorrhage;
2. show that intravenous lidocaine infusion is safe in treating headache following non-traumatic subarachnoid hemorrhage;
3. and report vasospasm prevalence in the cohort.

Participants will receive lidocaine infusion as treatment for non-traumatic subarachnoid hemorrhage headache and provide pain scores (on a numeric pain scale) every two hours the patients are awake for a maximum of seven days. Monitoring for vasospasm will occur as part of the patients regular medical care.

Inclusion Criteria:

• Patients > 18 years;
• Have a favorable neurological status defined as Hunt and Hess score ≤ 3 (as it accounts for patient awareness);
• Can communicate numeric pain scores;
• Are diagnosed with non-traumatic subarachnoid hemorrhage

Exclusion Criteria:

• The patient is diagnosed with traumatic subarachnoid hemorrhage;
• If the patient is < 18 years of age;
• If numeric pain scores could not be captured for > 3 days of hospitalization;
• If the patient had a prior aneurysm;
• Chronic pain not associated with non-traumatic subarachnoid hemorrhage diagnosis;
• A disability before the stroke (> 2 on modified Rankin Scale score);
• A Hunt and Hess score > 3;
• Contraindications to lidocaine (significant cardiac disease, arrhythmia, seizures, previous allergic reaction to lidocaine

Patients will be recruited once a diagnosis of non-traumatic subarachnoid hemorrhage has been confirmed and the patients meet the inclusion criteria for the study. The investigators will exclude incarcerated patients and pregnant women from the study, but the investigators will include patients that cannot consent themselves, as long as the patient meets the inclusion criteria, the investigators can gain consent from the patient's legal guardian/representative, and the patient can report a numeric pain score for the full length of the study (every 2 h the patient is awake for up to 7 days).