Resuscitative Endocrinology:Single-dose Clinical Uses for Estrogen-Traumatic Brain Injury

Early estrogen treatment has been tested in a myriad of animal models of resuscitation ranging from TBI and stroke to spinal cord injury, trauma-related hemorrhage, and sepsis. In these scenarios, studies using old and young, male and female animals found estrogen to be a strikingly effective therapy. Importantly, various animal studies examining brain injury sizes via radiological imaging and sophisticated immunofluorescent techniques have revealed significant protective effects of IV estrogen given post-injury, noting decreases in injury size of up to 65% in those receiving estrogen compared with those not receiving it. Furthermore, this beneficial effect is seen in all body tissues in both males and females. Only one identified TBI study to date did not show similar efficacy. A rodent model of TBI found that all females, in all three groups (those receiving no treatment, placebo, and estrogen) inexplicably died.

Mechanisms of Estrogen's Neuroprotection The use of estrogen as an acute resuscitation drug for severe brain injury has been extensively investigated in animal models. The mechanisms of estrogen's protective effects are numerous, including prevention of propogation of oxidant injury, anti-inflammatory properties in all major organs in the body, and mitochondria stabilization.

Importantly, the following studies find that estrogen exerts significant neuroprotective effects aimed at many of the mechanisms implicated in devastating secondary brain injury in TBI, including:

Brain Ischemia and Reperfusion Intracerebral Hemorrhage (a frequent component of traumatic brain injury) Impaired Cerebral Blood Flow Cerebral Vasospasm Cerebral Metabolic Dysfunction, including mitochondrial dysfunction with reduction of ATP production Cerebral Excitotoxicity and Blood Brain Barrier Preservation Cerebral Oxidant Injury Cerebral Edema Cerebral Inflammation Apoptosis

The protective effects of estrogen may initially appear counterintuitive in light of the recent WHI and HERS trials which studied long-term, oral, low-dose administration of estrogen in older, significantly-post menopausal women. In contrast, the proposed study utilizes a one-time resuscitative dose of IV estrogen administered rapidly following the injury. From a safety standpoint, there are a hundred-million women years of safety data for estrogen's clinical use, and safe use has been documented in men with prostate cancer, uremic bleeding, liver transplantation, and spine surgery. Any safety concerns, such as clotting effects found with long-tem, orally administered estrogen would not be expected when administered one time through an IV dose. Estrogen, when administered IV, avoids the first pass effect in the liver, and does not trigger the ER-α mediated pro-thrombotic effects seen with oral administration. Therefore, it is felt that this acute, IV single-dose administration of estrogen will convey the protective benefits seen in animal studies without side effects implicated with long-term oral use in humans.

Finally, estrogen is not the only sex steroid implicated in resuscitation. While estrogen has been the most frequently studied sex steroid in animal resuscitation models, progesterone too is thought to have potential neuroprotective effects. There is a recently published clinical pilot trial of IV progesterone as an acute resuscitative therapy for TBI patients, which indicates potentially promising clinical results without negative safety findings, thereby also poising this sex steroid for future multi-center trials.

In summary, we believe that there are compelling reasons to evaluate estrogen as an acute intervention in patients with traumatic brain injury given the benefit demonstrated in animal studies of brain injury, and safety data in humans prescribed estrogen for other indications. But we are aware that there are no published data related to use of a single dose of IV estrogen in injured patients in the acute setting. Therefore we have conceptualized our trial with frequent evaluation of patient safety through an organized Data Safety Monitoring Committee.

Potential participants include patients between the ages of 18 and 55 years who are admitted to Parkland Memorial Hospital or Baylor University Medical Center with a presumed diagnosis of severe traumatic brain injury. This young population was chosen for several reasons:

1. This population represents the most frequent patient with TBI (young).
2. This population filters out confounders such as chronic, age-related illnesses. Upon admission to the Emergency Department and evaluation of the patient in light of study criteria, qualified participants will be randomized to receive a single dose of 0.5 mg/kg Premarin® IV or placebo. One 7cc tube of blood and available urine will be drawn for baseline values prior to study drug administration. Those patients who require the placement of a ventriculostomy by a neurosurgeon for therapeutic treatment will also have one 7cc test tube of blood and available urine from the foley catheter drawn at the time the ventriculostomy is placed. Upon placement of the ventriculostomy, cerebral spinal fluid that would otherwise be discarded will be collected. These fluids will be centrifuged and frozen within one hour of collection, and the blood, CSF and urine analyzed in batches for markers of injury and repair. These samples will then be serially collected on an every four hour schedule over the first 24 hours, then every 8 hours for the following 4 days. CSF collection will end early if the ventriculostomy is removed for clinical reasons. Clinically-relevant patient progress (such as vital signs, Glasgow Coma Scale (GCS), partial pressure of carbon dioxide in the arterial blood (PaCO2), intracranial pressure (ICP), and temperature), clinically required interventions, neuro-imaging results, and demographics will be monitored and tracked.

For assessing length of time in coma and orientation, we will administer the Galveston Orientation and Amnesia Test (GOAT) daily until the patient successfully completes the test, for up to 2 months.

Longer-term neurological outcomes will be measured at discharge, 28 days, 3 and 6 months post-injury utilizing the Disability Rating Scale, Glasgow Outcome Score-Extended (GOSE), and Functional Status Examination. These outcomes measures will be collected by the research staff via telephone interviews if the patient has been discharged. The Disability Rating Scale (DRS), Glasgow Outcome Scale-Extended GOSE, and Functional Status Examination are well validated in the literature for follow-up in patients with TBI. These tests can be easily administered over the phone to either the patient or the caregiver.