Paramedian access to the epidural space: The optimum window for ultrasoundimaging

Study Objective: To establish a useful ultrasonic approach to the epidural space so as to optimize pre-puncture diagnostics. Design: Prospective study. Setting: University clinic. Patients: 60 participants (19 to 34 years of age), 40 healthy volunteers (2 0 male, 20 female) and 20 parturients. Interventions: Ultrasound scanning of the lumbar spine was performed at the L-3-L-4 vertebral interspace. Three ultrasound planes were employed: the t ransverse, median, and paramedian longitudinal approaches. Measurements: We compared the width of the ultrasound-permeable area in the median and paramedian planes and assessed the visibility of the epidural s pace and its surrounding structures. Main Results: In the paramedian plane, the permeable window was larger (p < 0.001) than in the median approach. The visibility of the ligamentum flavu m (p < 0.0001), dura mater (p < 0.0001), and cauda equina (p < 0.0001) was significantly higher Pulsation of epidural vessels could be observed more f requently (p < 0.0001) in the paramedian plane. Conclusions: The longitudinal paramedian plane provided information about t he epidural space depth in excellent imaging quality. The additional inform ation might be beneficial in epidural anesthesia and in other clinical spec ialties (e.g, neurosurgery, trauma care). (C) 2001 by Elsevier Science Inc.