Neurosurgery 99:537–544, 2026
Postoperative drainage is an important component of chronic subdural hematoma surgery, yet the interpretation of drainage volume and duration remains clinically relevant to the prevention of recurrence. This analysis of the FINISH trial examines their association with reoperation, alongside the volume of intraoperative irrigation. Its findings invite a critical appraisal of the assumption that greater drainage necessarily reflects more effective evacuation, while emphasizing the distinction between observational associations and evidence sufficient to establish a standardized drainage protocol.
Objective
To examine whether drainage and irrigation measurements relate to recurrence requiring reoperation.
Methods
This post hoc analysis used 546 patients from the multicenter FINISH irrigation trial. Logistic regression assessed drainage volume, duration and irrigation volume against outcomes.
Main results
Reoperation occurred in 84 patients (15.4%). Median drainage was 70 mL over 48 hours. Each additional 100 mL was associated with higher reoperation odds (OR 1.15, 95% CI 1.02–1.31). Reoperation rates were 18.2% with drainage under 48 hours and 12.1% at 48 hours or longer. Irrigation volume was not associated with reoperation.
Interpretation — operative relevance
The practical decision is how to interpret the postoperative drain within the evacuation strategy. The study does not justify deliberately increasing or restricting output. A high output may identify a different clinical situation rather than cause recurrence.
Similarly, these comparisons do not establish that extending every drain beyond 48 hours improves outcome. The duration comparison was not randomized, even though the parent trial was. More irrigation should not be equated automatically with a better operation.
Limitations
Drainage exposures were observational. Clinical decisions and unmeasured factors may explain part of the associations. The abstract does not provide a validated output-based removal algorithm or enough procedural detail to compare drain position, suction or irrigation technique.
Clinical takeaway
Document output and elapsed drainage time together, and interpret them alongside clinical recovery. This paper is useful for reviewing a unit’s drain protocol; it does not supply a new mandatory removal threshold or irrigation dose.