Non-invasive Measurement of Cerebrovascular Reactivity After Traumatic Brain Injury

Inclusion Criteria:

1. Men and women, aged ≥18

2. CT evidence of TBI-linked abnormality

- Traumatic subarachnoid hemorrhage

- Intracerebral hemorrhage/contusion

- Subdural/epidural hematoma

3. Ability to undergo fNIRS testing with hypercapnia challenge

4. Subject able to provide informed consent

5. Attending of record agrees to include subject in study

Exclusion Criteria:

1. Unstable respiratory or hemodynamic status

2. Evidence of penetrating brain injury

3. TBI requiring craniotomy or craniectomy

4. Evidence or risk of ICP crisis

5. History of disabling pre-existing neurologic disorder (e.g. dementia, uncontrolled
epilepsy, multiple sclerosis, strokes, brain tumors, prior severe TBI, or other
disorder that confounds interpretation of NIRS testing or neuropsychological results)

6. History of pre-existing disabling mental illness (e.g. major depression or
schizophrenia)

7. Exclusion criteria for sildenafil administration:

- History of melanoma

- current use of organic nitrate vasodilators

- current use of ritonavir (HIV-protease inhibitor)

- current use of erythromycin, ketoconazole, or itraconazole; current use of
cimetidine

- current use of alpha-blockers such as doxazosin (Cardura), tamsulosin (Flomax),
and terazosin (Hytrin) prazosin (Minipres)

- resting hypotension (systolic BP <90)

- severe renal insufficiency

- hepatic cirrhosis

- acute ischemic stroke within past 2 months

- acute myocardial infarction within past 2 months

- unstable angina pectoris

- acute or chronic heart failure

- retinitis pigmentosa

- pregnant or breastfeeding female

- known hypersensitivity or allergy to sildenafil

8. Unstable cardiac status that constitutes a contraindication to sexual activity

9. Inability to read and communicate in English (necessary to obtain reliable
neuropsychometric data)

10. Nursing mothers