Paramedian access to the epidural space: The optimum window for ultrasound imaging

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 (20 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 transverse, 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 space 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 flavum (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 frequently (p < 0.0001) in the paramedian plane. Conclusions: The longitudinal paramedian plane provided information about the epidural space depth in excellent imaging quality. The additional information might be beneficial in epidural anesthesia and in other clinical specialties (e.g, neurosurgery, trauma care). (C) 2001 by Elsevier Science Inc.