Excessive subgaleal suction from a variable vacuum drainage system used for managing chronic subdural hematomas: a cautionary note. Illustrative case

BACKGROUND: Negative-pressure drainage is commonly used to manage chronic subdural hematomas. A patient underwent burr hole drainage of a chronic subdural hematoma with subgaleal drainage set at the medium-pressure setting using a variable drainage system. Postoperative CT imaging documented extensive subarachnoid and parenchymal hemorrhage. Independent testing of the VariVac drainage system was performed using a Rigel VenTest 810 calibrated gas flow analyzer. OBSERVATIONS: Testing revealed that suction pressures had exceeded the threshold in two of three canisters with the valve mechanism set on medium. Negative pressures of up to 25 kPa (187.5 mm Hg) were attained on high when the maximum setting was intended to be 15 kPa (112.5 mm Hg) only. There was also variability between the three tested canisters, suggesting a lack of consistency. In general, higher suction pressures than the manufacturer-stated values were observed. LESSONS: There is significant discrepancy between the quoted manufacturer and actual suction pressures applied by variable suction drains. This may result in a mismatch with surgeon expectations of specific drain pressure settings, occasionally leading to potentially catastrophic consequences. It is imperative that caution be exercised when utilizing VariVac drains given that an excessive force on the brain may be inadvertently applied, leading to multifocal and multicompartmental catastrophic hemorrhage. https://thejns.org/doi/10.3171/CASE26108.