Near Infra-red Spectroscopy in the Diagnosis of Acute Compartment Syndrome

Description: OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #8, 9:12 AM *Near Infra-red Spectroscopy in the Diagnosis of Acute Compartment Syndrome Matthew J. Hope, MRCSE ; Carol Hajducka, RN; Hamish Simpson, MD; Margaret M. McQueen, MD, FRCS; Royal Infirmary of Edinburgh, Edinburgh, United Kingdom (a-Hutchinson Technology) Purpose: Near-infrared spectroscopy (NIRS), which measures soft tissue oxygenation (StO 2 ) noninvasively, is potentially a new noninvasive technique for the early detection of acute compartment syndrome (ACS). Animal models of ACS have shown that StO 2 correlates with perfusion pressure in the compartment. The first part of this study examined intracompartmental pressure and StO 2 among patients at risk of ACS. The second part investigated the influence of subcutaneous and intramuscular hematoma on NIRS in an ACS animal model. Methods: 1) Adult patients with tibial or radial diaphyseal fracture or gross soft tissue swelling were recruited on admission to the orthopaedic trauma unit. Noninvasive and invasive monitoring were carried out from admission until a minimum of 24 hours postoperatively. The differential pressure (DDP) was calculated as the compartment pressure subtracted from the diastolic blood pressure. The threshold for fasciotomy was a 'DDP' <30mmHg. StO 2 values were simultaneously recorded from the contralateral (uninjured) limb at the same site. The difference between the StO 2 value on the injured and uninjured sides was calculated (StO 2 difference). 2) Fifteen adult pigs were divided into three equal groups: plasma infusion alone, plasma infusion with SC hematoma (15 ml of blood) and whole blood infusion (intramuscular hematoma). An ACS was induced under general anesthesia by the above infusion into the anterior compartment of one rear leg of each animal. On both legs noninvasive StO 2 and compartment pressure monitoring were carried out. The development of an ACS was confirmed by absence of muscle twitch on electrical stimulation. Fasciotomy was performed 30 minutes later. DDP and 'StO 2 difference' (calculated as above) were compared. Results: 1) Three patients with thigh swelling, 73 with tibial fracture, and 2 with forearm fracture were recruited.   Mean 'StO 2 difference'    (%)  Mean 'DDP'  (mmHg)  no fasciotomy ( N = 59)  10.0   P = 0.003  52.6   P < 0.001  fasciotomy ( N = 18, all leg)  -2.7    24.5   2) An acute compartment syndrome was confirmed in all animals. Correlation between DDP (mmHg) and 'StO 2 difference' (%)  Plasma infusion ( N = 5)   r = 0.754   P = 0.01  Plasma infusion + SC hematoma ( N = 5)   r = 0.004   P = 0.95  Intramuscular hematoma ( N = 4)   r = 0.516   P = 0.01 Discussion/Conclusion: The StO 2 difference (measured noninvasively) was significantly lower among patients with an ACS, suggesting that NIRS can detect decreasing tissue oxygenation in trauma patients who are developing an ACS. The animal study confirms a strong correlation between DDP (mmHg) and StO 2 difference (%) in a plasma infusion and an intramuscular hematoma model. This correlation was lost in the presence of a SC hematoma. We are optimistic that NIRS will prove to be a reliable new noninvasive technique for the early detection of an acute compartment syndrome. The localization and avoidance of areas of SC hematoma will improve the diagnostic accuracy of NIRS in acute compartment syndrome.