Assessment of drainage techniques for evacuation of chronic subdural hematoma: a consecutive population-based comparative cohort study

Abstract

OBJECTIVE Surgery for chronic subdural hematoma (CSDH) is one of the most common neurosurgical procedures. The benefit of postoperative passive subdural drainage compared with no drains has been established, but other drainage techniques are common, and their effectiveness compared with passive subdural drains remains unknown. METHODS In Scandinavian population-based cohorts the authors conducted a consecutive, parallel cohort study to compare different drainage techniques. The techniques used were continuous irrigation and drainage (CID cohort, n = 166), passive subdural drainage (PD cohort, n = 330), and active subgaleal drainage (AD cohort, n = 764). The primary end point was recurrence in need of reoperation within 6 months of index surgery. Secondary end points were complications, perioperative mortality, and overall survival. The analyses were based on direct regional comparison (i.e., surgical strategy). RESULTS Recurrence in need of surgery was observed in 18 patients (10.8%) in the CID cohort, in 66 patients (20.0%) in the PD cohort, and in 85 patients (11.1%) in the AD cohort (p < 0.001). Complications were more common in the CID cohort (14.5%) compared with the PD (7.3%) and AD (8.1%) cohorts (p = 0.019). Perioperative mortality rates were similar between cohorts (p = 0.621). There were some differences in baseline and treatment characteristics possibly interfering with the above-mentioned results. However, after adjusting for differences in baseline and treatment characteristics in a regression model, the drainage techniques were still significantly associated with clinical outcome (p < 0.001 for recurrence, p = 0.017 for complications). CONCLUSIONS Compared with the AD cohort, more recurrences were observed in the PD cohort and more complications in the CID cohort, also after adjustment for differences at baseline. Although the authors cannot exclude unmeasured confounding factors when comparing centers, AD appears superior to the more common PD. Clinical trial registration no.: NCT01930617 (clinicaltrials.gov).

Hawthorne effect on surgical studies

“…The observational studies that mentioned the Hawthorne effect as an explanation for some of their outcomes were all good quality studies (Table ). Five RCTs were of poor quality, mainly due to personnel not being blinded to the intervention and one was of fair quality as shown in Table .…”

“…Four trials were based on orthopaedics (three observational studies; one RCT), three on obstetrics (two observational studies; one RCT), three on neurosurgery (two observational studies; one RCT), three on general surgery (one observational study; two RCTs) and one each on cardiothoracic (observational), ear nose and throat (observational) and maxillofacial surgery (RCT). Thirteen studies reported participant gender, being 3178 females (69%) and 1409 males (31%) . The mean age of participants was 61.1 years (Table ) .…”

“…14 Three studies had shorter follow-up periods post-intervention, thus making it possible that the improved outcomes were due to inadequate length of follow-up. [14][15][16] The observational studies that mentioned the Hawthorne effect as an explanation for some of their outcomes were all good quality studies 19,22,26,27 (Table 7). Five RCTs were of poor quality, mainly due to personnel not being blinded to the intervention 18,20,21,23,24 and one was of fair quality 25 as shown in Table 8.…”

“…The results from this systematic review suggest that there are three general trends for the acknowledgement of the Hawthorne effect in surgical studies: (i) studies that acknowledged the possible bias of the Hawthorne effect on their finding and thus tried to quantify it, (ii) studies that mentioned the Hawthorne effect as a way to justify unexpected results in their studies and (iii) studies that used the Hawthorne effect to explain differences seen between their results and the results of similar studies …”

“…Thirteen studies reported participant gender, being 3178 females (69%) and 1409 males (31%). 12,[15][16][17][18][19][20][22][23][24][25][26][27] The mean age of participants was 61.1 years ( Table 2).…”