Burr-hole drainage with or without irrigation for chronic subdural haematoma (FINISH): a Finnish, nationwide, parallel-group, multicentre, randomised, controlled, non-inferiority trial

Background Chronic subdural haematoma is a common surgically treated intracranial emergency. Burr-hole drainage surgery, to evacuate chronic subdural haematoma, involves three elements: creation of a burr hole for access, irrigation of the subdural space, and insertion of a subdural drain. Although the subdural drain has been established as beneficial, the therapeutic effect of subdural irrigation has not been addressed. Methods The FINISH trial was an investigator-initiated, pragmatic, multicentre, nationwide, randomised, controlled, parallel-group, non-inferiority trial in five neurosurgical units in Finland that enrolled adults aged 18 years or older with a chronic subdural haematoma requiring burr-hole drainage. Patients were randomly assigned (1:1) by computergenerated block randomisation with block sizes of four, six, or eight, stratified by site, to burr-hole drainage either with or without subdural irrigation. All patients and staff were masked to treatment assignment apart from the neurosurgeon and operating room staff. A burr hole was drilled at the site of maximum haematoma thickness in both groups, and the subdural space was either irrigated or not irrigated before inserting a subdural drain, which remained in place for 48 h. Reoperations, functional outcome, mortality, and adverse events were recorded for 6 months after surgery. The primary outcome was the reoperation rate within 6 months. The non-inferiority margin was set at 7<middle dot>5%. Key secondary outcomes that were also required to conclude non-inferiority were the proportion of participants with unfavourable functional outcomes (ie, modified Rankin Scale score of 4-6, where 0 indicates no symptoms and 6 indicates death) and mortality rate at 6 months. The primary and key secondary analyses were done in both the intention-to-treat and per-protocol populations. The trial was registered with ClinicalTrials.gov (NCT04203550) and is completed. Findings From Jan 1, 2020, to Aug 17, 2022, we assessed 1644 patients for eligibility and 589 (36%) patients were randomly assigned to a treatment group and treated (294 assigned to drainage with irrigation and 295 assigned to drainage without irrigation; 165 [28%] women and 424 [72%] men). The 6-month follow-up period extended until Feb 14, 2023. In the intention-to-treat analysis, 54 (18<middle dot>3%) of 295 participants required reoperation in the group assigned to receive no irrigation versus 37 (12<middle dot>6%) of 294 in the group assigned to receive irrigation (difference of 6<middle dot>0 percentage points, 95% CI 0<middle dot>2-11<middle dot>7; p=0<middle dot>30; adjusted for study site). There were no significant between-group differences in the proportion of people with modified Rankin Scale score of 4-6 (37 [13<middle dot>1%] of 283 in the no-irrigation group vs 36 [12<middle dot>6%] of 285 in the irrigation group; p=0<middle dot>89) or mortality rate (18 [6<middle dot>1%] of 295 in the no-irrigation group vs 21 [7<middle dot>1%] of 294 in the irrigation group; p=0<middle dot>58). The findings of the primary intention-to-treat analysis were not materially altered in the per-protocol analysis.There were no significant between-group differences in the number of adverse events, and the most frequent severe adverse events were systemic infections (26 [8<middle dot>8%] of 295 participants who did not receive irrigation vs 22 [7<middle dot>5%] of 294 participants who received irrigation), intracranial haemorrhage (13 [4<middle dot>4%] vs seven [2<middle dot>4%]), and epileptic seizures (five [1<middle dot>7%] vs nine [3<middle dot>1%]). Interpretation We could not conclude non-inferiority of burr-hole drainage without irrigation. The reoperation rate was 6<middle dot>0 percentage points higher after burr-hole drainage without subdural irrigation than with subdural irrigation. Considering that there were no differences in functional outcome or mortality between the groups, the trial favours the use of subdural irrigation.