Session II - Tibia
Fri., 10/8/04 Tibia, Paper #8, 10:42 am
·Compartment Syndrome Ultrafiltration Catheters: Report of a Clinical Pilot Study of a Novel Method for Management of Patients at Risk of Compartment Syndrome
Purpose: In this pilot study, we evaluated use of the Intramuscular Pressure and Fluid (IMPF) monitoring system in patients with tibia fractures. The IMPF catheter measures intramuscular pressure (IMP) and removes tissue fluid via tissue ultrafiltration. The hypothesis is that removal of interstitial fluid will reduce intramuscular pressure and allow for analysis of the fluid for improved diagnosis.
Methods: The protocol was approved by the Human Subjects Research Committee. Subjects were treated with the IMPF catheter and a standard Stryker pressure-monitoring catheter. One of each catheter was placed in both the anterior and in the deep posterior compartment of the leg after surgery and used for 24 hours. Outcomes included the pressures measured by each catheter and changes in the perfusion pressure of the limb. Ultrafiltrate fluid was removed in 8-hour aliquots and analyzed for lactate dehydrogenase (LDH) and creatine phosphokinase (CPK).
Results: Ten patients were included in the study. No serious device-related complications occurred. There was a reasonable correlation between the pressures measured by the IMPF and by the Stryker catheter. Pooled mean postoperative IMP was 38.1 ± 21.1 mm Hg SD, and this was used as a pre-treatment baseline (hour 0 to hour 1). Mean pressure during the treatment period (hour 2 to hour 24) was 26.7 ± 15.2 mm Hg SD for all patients. The average decrease in IMP was 11.4 ± 8.8 mm Hg SD for both catheters in the anterior compartment (P = 0.003 by two-tailed paired t- test). Perfusion pressure increased by 14.9 ± 11.7 mm Hg from baseline to the mean of the treatment period.
Mean ultrafiltrate levels of LDH were 38,502 ±20,723 IU/l (SD) and mean CPK was 20,159 ± 14,252 IU/l in all 10 patients. Serum levels were drawn pre- and post-observation. In general, analyte levels decreased over time and serum levels increased over time. Mean ultrafiltrate:serum concentration ratios were 183 and 87 for CPK and LDH at the beginning of the study and 34 and 57, respectively, at the end of the study. There was wide variability in concentrations in the ultrafiltrate, but a modest correlation (R2 = 0.54) was shown between high IMP and high ultrafiltrate concentrations of LDH and CPK.
No patient needed a fasciotomy or developed compartment syndrome during the study. One patient developed clinical signs of compartment syndrome 22 hours after catheter removal and underwent fasciotomy. At the time of fasciotomy, myonecrosis was seen only in the untreated lateral compartment.
Conclusion: This pilot study of IMPF catheters demonstrates a reduction in IMP with treatment. Measurement of enzymes in tissue fluid may make it easier to detect the presence of compartment syndrome. Ultrafiltrate levels were almost two orders of magnitude greater than serum concentrations because ultrafiltrate is pure undiluted interstitial fluid. Low serum levels may mean either no injury or poor perfusion to the area, so assay of the ultrafiltrate may provide greater sensitivity to muscle injury. A randomized controlled study is necessary to prove the efficacy of IMPF catheters.
Significance: IMPF catheters may provide an improved method of diagnosis and potentially reduce the incidence of compartment syndrome in those patients at risk.