The Use of Near Infrared Spectroscopy in the Diagnosis of Acute Compartment Syndrome

• Incidence of acute compartment syndrome (ACS) [ Time Frame: 24-48 hours at study site ] [ Designated as safety issue: No ]
  The "gold standard" criterion for ACS will be "clinical diagnosis". That is, all subjects undergoing fasciotomy for clinically diagnosed ACS (NOT PROPHYLACTIC fasciotomies) will be considered to have ACS. NIRS values will be compared to clinical diagnosis to determine accuracy and threshold values.
  
  

• Intracompartmental pressure (ICP) [ Time Frame: 24-48 hours at study site ] [ Designated as safety issue: No ]
  ICP measurements will be taken at the doctor's discretion, as this is the only existing objective diagnostic tool for ACS. When available, ICP will be compared to NIRS values to assess the magnitude of agreement between the 2 tools.
  
  

The purpose of this prospective observational cohort study is to define the reliability and accuracy of Near Infrared Spectroscopy (NIRS) in the detection of intra-compartmental tissue perfusion in injured and noninjured extremities over time. Additionally, it will establish diagnostic perfusion value thresholds to be used in a subsequent interventional study confirming the efficacy of NIRS-based ACS monitoring. Through prospective measurements of NIRS values, vital signs, intracompartmental pressures and clinical examinations, guidelines and parameters will be established for the use of NIRS in diagnosing acute compartment syndrome (ACS), monitoring patients at risk for ACS and evaluating the adequacy of fasciotomy in patients treated for ACS.

Null hypotheses:

• NIRS values do not correlate with intracompartmental pressures, when they are obtained in the course of routine care of patients in the combat theater.
• There is no difference in the NIRS values between non-injured, injured extremities and injured extremities treated with fasciotomy for ACS
• NIRS values from the upper extremity and feet do not correlate to NIRS values from the normal legs in critical control patients and patients with unilateral severe lower extremity injury.

Specific Aims:

1. Conduct observational, human-use, study to compile a normative reference database for NIRS-measured tissue perfusion in the uninjured upper extremity and the injured and non-injured legs of up to 120 injured subjects, from varying ethnicities (skin pigmentations) in varying degrees of hemodynamic status (stable, critically injured) to test the 3 hypotheses listed above. The study groups consist of one control group (critically ill without leg injuries) and one investigational group (critically injured with leg injuries):

   • COHORT 1: 25 critically injured patients with NO severe traumatic lower extremity traumatic injuries to provide normative data for the "critically injured" physiological status ("Critical" CONTROLS)
   • COHORT 2: 95 total (35 Cohort 2A; 35 Cohort 2B; 25 Cohort 2C) patients with "severe" traumatic lower extremity injuries presenting to a "participating" level 1 trauma center within 12 hours of their injury, to provide data on the acute post-injury phase. (INVESTIGATIONAL COHORT)
   • COHORT 2A: Patients meeting COHORT 2 inclusion criteria, who have UNILATERAL "severe lower extremity injuries".
   • COHORT 2B: Patients meeting COHORT 2 inclusion criteria, who have BILATERAL "severe lower extremity injuries".
   • COHORT 2C (ACS GROUP): Patients meeting COHORT 2 inclusion criteria, who have been clinically diagnosed by the treating provider using that treating provider's standards of diagnosing ACS and the patient, in addition to being diagnosed with ACS, undergoes four-compartment leg fasciotomy. Patients in this cohort need data collection to start BEFORE fasciotomy and continue AFTER fasciotomy.
2. Record provider comments regarding usability of the technology in its new embodiment and areas of needed design improvement. Apply this knowledge to perfect the industrial design and functionality of the final device.
3. Establish evidenced-based clinical guidelines for the diagnosis and management of ACS in traumatically injured soldiers to be tested in a subsequent interventional clinical (IDE) study.