Rapid Detection and Initial Treatment of Life-Threatening Subdural Hematoma in a Sheep Model

Technical Summary: Rapid Detection and Initial Treatment of Life-Threatening Subdural Hematoma in a Sheep Model

Problem Statement
Traumatic brain injury (TBI) is the leading cause of death and disability in individuals under 40 globally. While the standard of care for severe TBI involving subdural or epidural hematomas involves rapid CT scanning and neurosurgical intervention, these resources are frequently unavailable in austere environments such as large-scale combat operations, mass casualty events, wilderness settings, and developing nations. Existing handheld infrared hemorrhage detection devices (e.g., Infrascanner 2000) suffer from critical limitations: they cannot independently assess brain regions (making them insensitive to bilateral hemorrhages), cannot distinguish between life-threatening intracranial bleeding and non-life-threatening scalp hemorrhages, and lack the spatial resolution to guide treatment. Furthermore, non-neurosurgeons generally lack the capability to safely perform emergency burr holes to relieve intracranial pressure (ICP) due to risks of brain injury, infection, and the difficulty of removing clotted blood through small openings.

Methodology
The authors developed and tested two prototype handheld devices in a novel sheep model of life-threatening subdural hematoma.

1. Detection Device: A frequency-domain, multi-detector infrared hemorrhage detection device was engineered with three specific advancements over existing technology:

   • Multi-detector geometry: Three detectors spaced at varying distances (1, 2, and 3 cm) from the source allow for differential sensitivity to superficial (scalp) versus deep (intracranial) tissues.
   • Frequency-domain modulation: An infrared laser with modulated intensity (200 MHz) enables the measurement of both amplitude attenuation and phase shift, providing deeper tissue characterization.
   • Dynamic scanning: The device is designed to be pressed against the head and moved continuously, with spatial tracking to ensure coverage and signal quality monitoring.
   • Testing: The device was calibrated using optical phantoms and tested on 23 sheep. Medical providers (medics, corpsmen, physicians) with minimal training (30 minutes) performed blinded scans. The study compared the new device against the Infrascanner 2000 in scenarios involving unilateral subdural hematoma, bilateral subdural hematoma, and the presence of confounding subgaleal (scalp) blood.

2. Treatment Device: A second handheld device was designed to allow non-neurosurgeons to safely create a burr hole and remove clotted blood. Key features include:

   • Secure anchoring via three bone screws with a foam gasket to act as an infection barrier.
   • A battery-powered cautery ring to seal the scalp.
   • A hand-crank drill with a pressure-sensitive clutch and hard stop to prevent penetration of the inner skull table.
   • A deployable blade to cut the dura.
   • A transparent access port compatible with a portable morcellator (NICO Myriad) to suction and cut clotted blood.
   • Testing: A preregistered, randomized, sham-controlled trial was conducted on 12 qualifying sheep (out of an initial 18). Non-neurosurgeons performed the procedure. The primary outcome was the reduction in ICP; secondary outcomes included blinded neurological assessments by veterinarians.

Key Results

• Sheep Model Validation: A 15-mL infusion of autologous venous blood into the subdural space successfully replicated life-threatening subdural hematoma, resulting in 50% mortality and significant ICP spikes (mean peak 114 mm Hg), mimicking human pathophysiology.
• Detection Accuracy:
  • In a simple unilateral vs. sham scenario, the new device achieved 0.58 sensitivity and 0.73 specificity, comparable to the Infrascanner 2000 (0.45 sensitivity, 0.84 specificity).
  • In complex scenarios involving bilateral subdural hematomas, the new device achieved 0.87 overall accuracy, significantly outperforming the Infrascanner 2000 (0.38 accuracy).
  • In scenarios with superficial subgaleal blood (simulating scalp trauma), the new device maintained 0.84 sensitivity for detecting the underlying subdural hematoma, whereas the Infrascanner 2000 dropped to 0.38 sensitivity. The new device successfully differentiated deep intracranial blood from superficial blood using its multi-detector array.
• Treatment Efficacy:
  • Non-neurosurgeons completed the entire treatment procedure (shaving, cauterizing, drilling, dural cutting, and morcellation) in under 20 minutes.
  • The treatment group showed a mean ICP reduction of 16.5 mm Hg compared to a 5 mm Hg reduction in the sham group (p=0.013).
  • Blinded neurological assessments revealed improved post-anesthesia outcomes in the treatment group compared to the sham group (p=0.05).
  • No device-related adverse events occurred, though two dural cutting blade failures were corrected on-site.

Significance and Claims
The paper claims that these two prototype devices address a critical unmet need for the rapid detection and initial treatment of life-threatening subdural hematomas when CT scanners and neurosurgeons are unavailable. The authors emphasize that these devices are not intended to replace definitive neurosurgical care but to serve as a bridge in challenging situations (e.g., military operations, rural trauma centers, developing world).

The study demonstrates that:

1. Advanced frequency-domain infrared technology can overcome the limitations of current handheld detectors, specifically regarding bilateral detection and differentiation from scalp hemorrhages.
2. A specialized, safety-featured handheld device can enable non-neurosurgeons to safely perform emergency burr holes and remove clotted blood, resulting in measurable ICP reduction and improved neurological outcomes in an animal model.

The authors conclude with modest optimism, noting that significant work remains—including replication, infection risk assessment, regulatory clearance, and human clinical trials—before these technologies can be translated to clinical practice.