SP27. Microdialysis Detects Subcutaneous and Intramuscular Biomarker Measurement Associated With Acute Peripheral Compartment Syndrome in a Porcine Model

PURPOSE: Peripheral compartment syndrome (PCS) occurs in approximately 8 out of every 100,000 people each year, with mortality rates of 15-20% following emergency fasciotomy. Currently, the diagnosis of PCS relies on clinical evaluation and intra-compartmental pressure (ICP) measurements, which identify PCS in only about 69% of cases. In microsurgery, microdialysis of tissue biomarkers, such as pH, has demonstrated the ability to detect flap vascular compromise 1-2 hours before it becomes clinically evident. We hypothesized that measuring pH from the interstitial fluid (ISF) using microdialysis allows accurate monitoring of metabolic changes associated with PCS. Additionally, we hypothesized that changes in pH sampled subcutaneously (SC) exhibit similar trends to those sampled in the intramuscular (IM) compartment. METHODS: Four male Yorkshire swine were used in a PCS model with bilateral hind limb tourniquets (eight hindlimbs). For six hours, we monitored changes in tissue metabolism of the Peroneus Tertius muscles by measuring intra-compartmental pressure (ICP), tissue oxygenation (SrO2) using near-infrared spectroscopy (NIRS), hindlimb temperature with a forward looking infrared (FLIR) thermal camera, and interstitial fluid pH in both intramuscular and subcutaneous tissues through microdialysis. RESULTS: ICP significantly increased immediately after tourniquet inflation and stayed elevated at all time points (pre-inflation: 12.5 ± 5.6 mmHg vs. post-inflation: 46.3 ± 30 mmHg, p = 0.05). Both SrO2 and hindlimb temperature significantly decreased within 0.5 hours post-inflation and remained low thereafter (SrO2: pre-inflation 69.4 ± 7% vs. 0.5 hours 25.6 ± 28%, p = 0.00005; temperature: pre-inflation 30.6 ± 2.6 °C vs. 0.5 hours 26.4 ± 2.9 °C, p = 0.0002). At hour 4, IM pH levels decreased significantly compared to baseline (pre-inflation: 7.5 ± 0.3 vs. 4 hours: 6.7 ± 0.4, p < 0.0019) and remained low until hour 6. SC pH levels decreased significantly by hour 3 and remained low at hour 6 (pre-inflation: 7.6 ± 0.6 vs. 3 hours: 7.1 ± 0.6, p = 0.005). No significant differences were found between IM and SC pH levels at all time points, except at hour 4 (IM: 6.7 ± 0.8 vs. SC: 7.1 ± 0.6, p = 0.05). CONCLUSION: Continuous monitoring of tissue pH through microdialysis can support the diagnosis of PCS. SC pH exhibit changes similar to those observed with more invasive IM sampling. Initial data should be validated in a larger cohort of animals to strengthen these findings.