Use of Novel Automated Active Irrigation With Drainage Versus Passive Drainage Alone for Chronic Subdural Hematoma—A Propensity Score-Matched Comparative Study With Volumetric Analysis : Operative Neurosurgery

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Use of Novel Automated Active Irrigation With Drainage Versus Passive Drainage Alone for Chronic Subdural Hematoma—A Propensity Score-Matched Comparative Study With Volumetric Analysis

Baig, Ammad A. MD*,‡; Hess, Ryan M. MD*,‡; Khan, Asham MD*,‡; Cappuzzo, Justin M. MD*,‡; Turner, Ryan C. MD, PhD*,‡; Hashmi, Eisa BS‡,§; Bregy, Amade MD, PhD*,‡; Kuo, Cathleen C. BS‡,§; Nyabuto, Elizabeth MD*,‡; Goyal, Aditya D. High School Diploma; Davies, Jason M. MD, PhD*,‡,‖,¶,#; Levy, Elad I. MD, MBA*,‡,¶,#,**; Siddiqui, Adnan H. MD, PhD*,‡,¶,#,**

Author Information
Operative Neurosurgery 24(6):p 630-640, June 2023. | DOI: 10.1227/ons.0000000000000630
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  • SDC



chronic subdural hematoma
length of stay
noncontrast computed tomography
propensity score matching
subdural hematoma.

Treatment of chronic subdural hematoma (cSDH)—a common condition faced by neurosurgeons ranging in incidence from 1.7/100 000 to 14/100 000 persons—is varied, although craniotomy has remained the most common surgical treatment with drainage through a standard passive drain considered the treatment “gold standard.”1-8 Typically, the drain is left behind to aid in clearing the residual hematoma, with or without irrigation. The high rates of catheter occlusion, repeat placements, and subsequent infections associated with passive drainage warrant development and implementation of new technologies that can better aid in the clearance of residual hematoma after surgical evacuation.

One such new technology, the IRRAflow system (IRRAS), uses automated continuous and active irrigation with drainage and may be used as an alternative to passive drainage alone after surgical evacuation.9 The system's dual-lumen catheter actively and continuously irrigates fluid (such as sterile saline solution) in the subdural space, along with passive drainage. In addition, the system's continuous intracranial pressure (ICP) monitoring and programmable flush irrigation system allow for more patient-tailored management.

The goal of this study was to compare the novel IRRAflow active and automated continuous irrigation with drainage system with standard passive drains for rates of cSDH clearance, catheter-related occlusions, infections, hospital length of stay (LOS), morbidity, and mortality.


Informed consent for procedures and publication of patient data was provided by each patient or legally authorized representative. Our local institutional review board approved this study. Data supporting the findings are available from the corresponding author on reasonable request.

Patient Population

Our prospectively maintained database was retrospectively searched for consecutive patients who presented with signs and symptoms of cSDH between September 2020 and April 2022. After radiographic confirmation using noncontrast computed tomography (NCCT), these patients underwent cSDH evacuation followed by IRRAflow catheter or passive drain placement. The choice of type of drain placement was at the operating surgeon's discretion. Patients were dichotomized into groups treated with active irrigation and drainage using IRRAflow and those treated with standard-of-care passive drains (TLS® Surgical Drainage System catheter [Stryker] or Jackson-Pratt® surgical drain [Cardinal Health) in the subdural space. Patient data collected included demographics, comorbidities, and smoking status. In addition, current anticoagulant and antiplatelet use was noted. Baseline neurological status was recorded using prehospital modified Rankin Scale (mRS) and admission Glasgow Coma Scale (GCS) scores. Presenting symptoms and intracranial hemorrhage (ICH) history were also recorded.

Procedural Details and Outcome Metrics

Procedural characteristics recorded were modality of treatment (craniotomy or burr-hole surgical evacuation), catheter placement details, irrigation fluid used, initial drainage height of the catheter, total drainage volume, and initial active irrigation rate (for the IRRAflow catheter). For outcome assessment, catheter occlusions or related infections requiring replacement and any subsequent revision were recorded.

Procedural outcomes recorded were seizure activity, hemorrhage during catheter placement, repeat subdural evacuation requiring intervention, and rate of conversion of the IRRAflow catheter to a standard drain. Other outcome metrics assessed were length of intensive care unit (ICU) stay and total hospital LOS. For patients readmitted for recurrent hematoma, LOS was calculated to reflect the sum of the length (days) of all admissions. Immediate follow-up data included discharge mRS and GCS scores and all-cause in-hospital mortality.

We typically use passive drains to promote continuous egress of subdural blood after surgical evacuation. The drains fall into two categories: gravity-driven and suction-driven. The gravity-driven drains are either TLS drains connected to drainage bags dropped below the patient's head or to a ventriculostomy catheter inserted into the subdural space and attached to a buretrol that is leveled to promote drainage. The suction drains are standard Jackson-Pratt drains that are placed on gentle bulb suction. We use the term “passive” to describe these methods because the drainage process does not require additional intervention. By contrast, “active” drainage involves the use of irrigation to promote egress of subdural blood postoperatively.

IRRAflow Catheter Placement and Management

Patients presenting with cSDH deemed good surgical candidates were transported to the operating room where surgical evacuation with craniotomy or burr-hole surgery was performed in standard fashion (Figure 1). After hematoma evacuation, the IRRAflow system was primed and its drainage catheter placed in the subdural space, after which the dura was reflected and the craniotomy or burr-hole site was closed (Figure 1). The drain was secured with 3-0 nylon sutures. Standard passive drains were placed in similar fashion. Drains were placed anterior to posterior in both groups. The patient was then transferred to the neurosurgical ICU. The IRRAflow control unit system was connected with the drainage catheter, and the system was calibrated to the desired drainage height and irrigation flow rate (Figure 2A-2C).

Intraoperative photographs. A, Right-sided chronic subdural hematoma collection demonstrated on opening the dura after subtotal craniotomy. B, Complete hematoma evacuation. C, A plastic passer is tunneled anterior to posterior using forceps followed by D, placement of the IRRAflow catheter (IRRAS) through the passer. E, The IRRAflow catheter is pulled through, with the plastic passer removed afterward (performed to maintain sterility and to avoid issues with multiple stopcocks being used for irrigation). F, Anterior-posterior placement before bone placement.
Postoperative setup. A, Fluid exchange system shown with an irrigating pump and drainage mechanism that interact with the dual-lumen catheter B, to irrigate the surgical site with sterile saline solution (black arrowhead) and drain (white arrowhead) residual blood from the subdural space. C, The digital pump used by the IRRAflow system to actively exchange fluid automatically sends a bolus of fluid into the irrigation channel of the catheter. This irrigation bolus serves to dilute further any solid particles that may have built up in the ventricles and keeps the catheter tip clear of solid debris, which can frequently obstruct drainage with an external ventricular drain. The second lumen of the catheter is then used to drain this diluted material while also checking the patient's intracranial pressure. This illustration was reproduced with permission from IRRAS, all rights reserved.

An initial flow rate of 20 mL/hour that was gradually titrated to a maximum rate of 120mL/hour for active irrigation and drainage was established for all patients. The drainage bag resembles the drainage receptacle of a Foley catheter and can be leveled like a standard ventricular drain. The bag height is generally set to −15 or −20 cm at the level of the tragus. Gravity acts as the driving force to promote fluid egress from the subdural space. Serial NCCT images were obtained throughout the hospital stay until discharge. Further details about the irrigation and drainage settings and associated safety mechanisms are presented in Supplemental Digital Content 1, Supplemental Methods,

Statistical and Volumetric Analysis

Means or medians were reported for continuous variables with respective SDs and IQR according to data normality. Categorical variables were reported as frequencies. One-to-one propensity score matching (PSM) was conducted to control for treatment selection bias (IRRAflow vs standard passive drain) using nearest-neighbor technique without replacement for comorbidities and presentation severity. Covariates included in the PSM model included age, sex, race, comorbidities, smoking status, prehospital mRS and admission GCS scores, and hematoma volume at presentation. Balance in these baseline variables was estimated using standardized mean differences, with a 10% difference regarded as imbalanced.

For volumetric analysis, NCCT images for each patient obtained preoperatively, postoperatively, and at discharge were retrieved from our database. To determine the hematoma volume from each scan, a digital imaging and communications in medicine file was loaded into ImageJ processing software (, where the color and contrast of each imaging series were adjusted to easily differentiate the hematoma from brain matter. The ImageJ segmentation plugin was then used along with a region-of-interest selection tool to outline the hematoma mass at each frame of the NCCT image. Beginning with the first frame in which the presence of a hematoma was visible (starting at the skull base, moving upward as the frames progressed), the hematoma was highlighted manually by 2 authors blinded to the type of drainage using the selection tool to precisely outline the hematoma area present in each layer of the brain (Figure 3). The hematoma selection was then converted to an area measurement. After delineating the hematoma at each layer, the area measurements were summed together and multiplied by layer height and pixel spacing in x and y directions to derive a total volume measurement for the hematoma. This process was repeated to determine the hematoma volume for each patient at each of the 3 time points studied. All postoperative imaging was obtained 1 hour after hematoma evacuation and drain placement. Residual hematoma was delineated as described above, with the exclusion of intraoperative irrigation fluid and pneumocephalus artifact. To calculate the actual hematoma clearance rate, the hematoma volume (mL) measured at the time of catheter/drain removal was subtracted from the volume measured at the time of catheter/drain placement and divided by the total number of days the catheter/drain was placed (rate = mL/day cleared).

Noncontrast computed tomography axial images showing chronic subdural hematoma segmentation at 3 different levels using ImageJ software ( The area of the hematoma is precisely outlined using the software selection tool and later calculated as volumes.

To determine the total brain volume at each instance of hematoma volume, Vitrea Advanced Visualization software (Canon Medical Informatics) was used to create a three-dimensional model of the brain based on an axial view NCCT digital imaging and communications in medicine file selected and calculated the total brain volume for each data point. Thus, each hematoma volume measurement could be better interpreted in the context of the paired total brain volume measurement.

For comparison between matched groups, data normality was checked and continuous variables were analyzed by two-sample Mann-Whitney t test. Categorical variables were analyzed using the χ2 test or Fisher test. All statistical tests were 2-tailed, and a P value of <.05 was considered statistically significant. To identify predictors or explanatory variables, multivariate logistic regression analysis was performed for all clinically relevant variables identified on bivariate analysis. All statistical analyses were performed with R Statistical and Computing software (version 4.1.3, released 2020; R Studio).


Patient Characteristics and Presentation

Overall, 55 patients were included in our cohort before PSM (standard passive drain group-34; active irrigation with IRRAflow group-21) (Figure 4A and 4B). All 55 patients were included in the PSM analysis. After one-to-one PSM, 21 patients were included in each group. No significant differences were found between matched groups for baseline demographics and presenting hematoma volume before or after PSM analysis (Table 1). The median admission GCS score was 14 (IQR 14-15) for both groups. Hematoma volume at presentation was slightly higher in the IRRAflow group, although the difference was nonsignificant (9.8 ± 5.8 vs 8.6 ± 5.2; P = .801).

Histogram for propensity score distribution A, before and B, after matching for age, sex, race-ethnicity, comorbidities (diabetes mellitus, hyperlipidemia, hypertension, and atrial fibrillation), smoking status, prehospital modified Rankin Scale score, admission Glasgow Coma Scale score, and hematoma volume at presentation. X-axis demonstrates frequency or the number of patients with an individual propensity score (Y-axis).
TABLE 1. - Patient Characteristics and Basic Demographics
Variable Before propensity score matching After propensity score matching
Passive drainage alone (n = 34) Active and continuous irrigation with drainage (n = 21) P-value Passive drainage alone (n = 21) Active and continuous irrigation with drainage (n = 21) P-value
Age, y (mean ± SD) 71.9 ± 10.0 73.7 ± 13.0 .538 72.0 ± 9.8 73.7 ± 13.0 .562
Sex (n [% of all cases])
 Women 11 (32.4) 4 (19) .444 6 (28.6) 4 (19) .717
 Men 23 (67.6) 17 (81) .444 15 (71.4) 17 (81) .717
Race–ethnicity (n [%])
 White 26 (76.5) 18 (85.7) .369 16 (76.2) 18 (85.7) .190
 African American 5 (14.7) 3 (14.3) .369 2 (9.5) 3 (14.3) .190
Comorbidities (n [%])
 Diabetes mellitus 9 (26.5) 3 (14.3) .467 4 (19) 3 (14.3) 1.000
 Hypertension 25 (73.5) 20 (95.2) .095 19 (90.5) 20 (95.2) 1.000
 Hyperlipidemia 11 (32.4) 13 (61.9) .062 10 (47.6) 13 (61.9) .535
 Atrial fibrillation 8 (23.5) 6 (28.6) .922 5 (23.8) 6 (28.6) 1.000
Smoking status (n [%])
 Active smoker 12 (35.3) 10 (47.6) .533 9 (42.9) 10 (47.6) 1.000
 Nonsmoker 22 (64.7) 11 (52.4) .533 12 (57.1) 11 (52.4) 1.000
 Previous smoker 0 (0) 0 (0) .533 0 (0) 0 (0) 1.000
Prehospital mRS (mean ± SD) 1.4 ± 1.4 1.4 ± 0.9 .473 1.4 ± 1.4 1.4 ± 0.9 .521
Admission GCS (median [IQR]) 14 (14-15) 14 (14-15) .704 14 (14-15) 14 (14-15) .798
Anticoagulation (n [%]) 2 (5.9) 3 (14.3) .568 2 (9.5) 3 (14.3) 1.000
Antiplatelet therapy (n [%])
 Aspirin 0 (0) 8 (38.1) <.001 0 (0) 8 (38.1) .469
 Clopidogrel 1 (2.9) 2 (9.5) .665 1 (4.8) 2 (9.5) 1.000
Presenting symptoms (n [%])
 Hemiparesis 13 (38.2) 9 (42.9) .335 9 (42.9) 9 (42.9) .688
 Altered mental status 9 (26.5) 2 (9.5) .335 3 (14.3) 2 (9.5) .688
 Headache 11 (32.4) 9 (42.9) .335 8 (38.1) 9 (42.9) .688
 Dysarthria 0 (0) 0 (0) .335 0 (0) 0 (0) .688
Hematoma volume at presentation, mL (mean ± SD) 9.9 ± 5.0 9.8 ± 5.8 .634 8.6 ± 5.2 9.8 ± 5.8 .801
Brain volume at presentation, mL (mean ± SD) 1357.5 ± 141.3 1354.9 ± 170.0 .869 1345.3 ± 131.6 1354.9 ± 170.0 .651
GCS, Glasgow Coma Scale (score); mRS, modified Rankin Scale (score).
Statistical significance is indicated with bold italics.

Procedural Outcomes

A significantly higher rate of hematoma clearance was found in the active irrigation and drainage group (IRRAflow group) than in the passive irrigation group (0.5 ± 0.4 vs 0.4 ± 0.5 mL/day; odds ratio [OR] = 1.291; CI: 1.062-1.570, P = .002) despite similar mean total duration of catheter placement (IRRAflow, 3.7 ± 2.2 days; passive irrigation, 4.4 ± 4.1 days; OR = 0.982; CI: 0.936-1.030; P = .737) (Table 2). On multivariate logistic regression analysis, significantly higher odds of a faster rate of hematoma clearance were demonstrated in the IRRAflow group than the passive irrigation group (OR = 1.830 (CI: 1.143-2.932), P = .022) (Table 3). Although catheter-related infections were nonsignificantly lower in the IRRAflow group than the passive irrigation group (0 vs 2 [9.5%]; OR = 0.243; CI: 0.008-4.016; P = .488) on bivariate analysis, this difference was statistically significant in the regression model, highlighting a lower likelihood of infection in the IRRAflow group (OR = 0.051, CI: 0.004-0.697; P = .039). Both groups had similar rates for catheter revision, shunt placement, and hematoma volume at discharge (Tables 2 and 3). No case required conversion of the IRRAflow catheter to a passive drain. A nonsignificantly higher rate of seizure activity was seen in the passive drainage group (3 [14.3%] vs 0; OR = 0; CI: 0.006-2.538; P = .231). Patients with IRRAflow placement had a nonsignificantly shorter length of hospital stay (6.8 ± 3.0 vs 10.6 ± 16.2 days; OR = 0.993; CI: 0.980-1.006; P = .829). One in-hospital death was recorded in each group (4.8%). The two operators performed a similar number of drain placement procedures after cSDH evacuation (operator 1: IRRAflow = 10, passive drain = 9; operator 2: IRRAflow = 11, passive drain = 12).

TABLE 2. - Procedural Details and Outcomes After Propensity Score Matching
Variable Passive drainage alone (n = 21) Active and continuous irrigation with drainage (n = 21) Passive drainage vs active and continuous irrigation with drainage
OR (95% CI) P-value
Surgical evacuation technique (n, %)
 Craniotomy 14 (66.7) 12 (57.1) 0.560 (0.201-2.306) .546
 Burr hole(s) 7 (33.3) 9 (42.9) Reference .546
Laterality of hematoma and surgical site (n, %)
 Bilateral 4 (19.0) 1 (4.8) Reference .340
 Left-sided 11 (52.4) 14 (66.7) 2.333 (0.510-28.045) .340
 Right-sided 6 (28.6) 6 (28.6) 1.714 (0.352-25.599) .340
Duration of catheter placement, d (mean ± SD) 4.4 ± 4.1 3.7 ± 2.2 0.982 (0.936-1.030) .737
Catheter revisions (n, %) 1 (4.8) 1 (4.8) 1.000 (0.483-2.070) 1.000
Catheter-related infections (n, %) 2 (9.5) 0 (0) 0.243 (0.008-4.016) .488
Shunt placement (n, %) 0 (0) 1 (4.8) 1.000 (0.121-81.739) 1.000
Repeat hematoma evacuation during hospital course (n, %) 1 (4.8) 3 (14.3) 1.579 (0.345-19.362) .599
Hematoma volume postevacuation, mL (mean ± SD) 2.4 ± 1.7 3.4 ± 3.0 1.052 (0.990-1.118) .279
Brain volume postevacuation, mL (mean ± SD) 1326.6 ± 136.1 1336.6 ± 175.0 1.000 (0.999-1.001) .860
Hematoma volume at discharge, mL (mean ± SD) 2.0 ± 1.7 2.1 ± 2.5 1.024 (0.979-1.071) .315
Brain volume at discharge, mL (mean ± SD) 1350.7 ± 146.3 1360.3 ± 174.3 1.000 (0.999-1.001) .847
Hematoma expansion at discharge (n, %) 5 (23.8) 1 (4.8) 0.127 (0.032-1.494) .186
Hematoma clearance rate, mL/d (mean ± SD) 0.4 ± 0.5 0.5 ± 0.4 1.291 (1.062-1.570) .002
Length of hospital stay, d (mean ± SD) 10.6 ± 16.2 6.8 ± 3.0 0.993 (0.980-1.006) .829
Length of ICU stay, d (mean ± SD) 4.5 ± 4.6 4.0 ± 2.1 0.991 (0.948-1.036) .566
Seizure activity 3 (14.3) 0 (0) 0 (0.006-2.538) .231
Other adverse events 4 (19.0) 1 (4.8) 0.162 (0.040-2.010) .341
Discharge mRS (median [IQR]) 1 (1-3) 1 (1-3) 0.984 (0.886-1.092) 1.000
 Good outcome (mRS 0-2) (n, %) 14 (66.7) 15 (71.4) 1.001 (0.346-4.397) .753
Discharge GCS (median [IQR]) 15 (14-15) 15.5 (15-16) 0.974 (0.887-1.070) .585
All cause in-hospital mortality, (n, %) 1 (4.8) 1 (4.8) 1.000 (0.483-2.070) 1.000
Mean follow-up (mo) 16.9 ± 18.5 9.8 ± 7.2 Overall: 13.3 ± 14.3
Hematoma recurrence on follow-up 2 (9.5) 2 (9.5) 1.000 (0.590-1.695) 1.000
GCS, Glasgow Coma Scale (score); ICU, intensive care unit; mRS, modified Rankin Scale (score).
Statistical significance is indicated with bold italics.

TABLE 3. - Multivariate Logistic Regression Analysis After Propensity Score Matching
Radiographic and clinical outcomes Passive drainage vs active and continuous irrigation with drainage
OR (95% CI) P-value
Treatment group (craniotomy) 0.755 (0.534-1.068) .130
Duration of catheter placement 1.005 (0.949-1.063) .877
Number of catheter revisions 0.403 (0.091-1.790) .249
Catheter-related infections 0.051 (0.004-0.697) .039
Shunt placement 5.479 (0.518-36.921) .104
Hematoma expansion at discharge 0.551 (0.272-1.114) .110
Repeat subdural evacuation 0.685 (0.367-1.280) .252
Hematoma volume postevacuation 0.878 (0.788-0.979) .131
Brain volume postevacuation 1.000 (0.997-1.003) .086
Hematoma volume at discharge 1.192 (0.982-2.867) .139
Brain volume at discharge 0.997 (0.994-1.000) .109
Hematoma clearance rate 1.830 (1.143-2.932) .022
Length of hospital stay 0.999 (0.977-1.022) .919
Length of ICU stay 1.086 (0.978-1.206) .141
Seizure activity 0.597 (0.351-1.018) .075
Other adverse events 0.822 (0.307-2.200) .702
Good outcome (discharge mRS of 0-2) 1.201 (0.970-1.486) .112
Discharge GCS 0.997 (0.994-1.000) .109
GCS, Glasgow Coma Scale (score); ICU, intensive care unit; mRS, modified Rankin Scale (score); OR, odds ratio.
Statistical significance is indicated with bold italics.

The hematoma recurrence rate during longer-term follow-up was also recorded. Overall, the mean follow-up duration was 13.3 ± 14.3 months (range: 2.3-34.3 months). It was 9.8 ± 7.2 months in the active irrigation and drainage group and 16.9 ± 18.5 months in the passive drainage group. The recurrence rate was 9.5% in each cohort (2 of 21 in each; OR = 1.000 [0.590-1.695]; P = 1.000). One patient in each arm (4.8%) underwent middle meningeal artery embolization, and 1 in each underwent repeat surgical evacuation.

Craniotomy and Burr-Hole Subgroup Outcomes

Further subgroup analysis comparing outcomes for craniotomy and burr-hole cases for the 2 different drainage techniques showed similar results. Interestingly, in the burr-hole subgroup, significantly lower hematoma expansion was seen in the active and continuous irrigation and drainage group compared with passive drainage alone (−3.9 ± 6.3 vs -0.1 ± 1.0; P = .029). Further details are presented in Supplemental Digital Content 2, Supplement Results,


In this PSM comparative study, we report our experience using continuous and automated, active irrigation with drainage for cSDH clearance postsurgical evacuation and compared that with passive drainage alone. Most significantly, we obtained a higher rate of hematoma clearance in the active irrigation and drainage IRRAflow group and a significantly lower rate of catheter-related infections. To the best of our knowledge, this is the first comparative study detailing the use of the novel IRRAflow system for patients with cSDH.

Adjunct continuous irrigation with drainage, although not a new concept, has shown promising results in some studies, which serve as good rationale for its use after surgical evacuation.10-14 Hennig and Kloster14 were one of the earliest groups who compared hematoma recurrence rates for patients treated with and without continuous irrigation. Hematoma recurrence was reported in 2 of 77 (2.6%) cases treated with continuous irrigation; an incidence rate 9 times lower than that for passive drainage alone (5 of 21 cases, 23.8%).14 More recently, Sjåvik et al13 conducted a consecutive population-based comparative cohort study assessing various drainage techniques for cSDH evacuation and compared continuous irrigation and drainage with passive subdural drainage and active subgaleal drainage. Significantly lower rates of recurrent hematoma requiring surgical evacuation were seen in the continuous irrigation and drainage group (10.8%) than the passive subdural drainage and active subgaleal drainage group (20% vs 11.1%; P <.001). These differences in clinical outcomes and recurrence rates provide evidence of benefit of postsurgical drainage complemented with irrigation. Possible mechanisms behind better hematoma clearance with irrigation are hypothesized, but long-lasting continuous irrigation seems to allow re-expansion of the brain within normal pressure limits, avoiding both passive and suction drainage. Moreover, an efficient washout of blood degradation products from the subdural space seems to be beneficial, even with recurrent bleeds. However, all previously mentioned studies relied on manual irrigation that was gravity-dependent or operator-dependent with variable irrigation rates and sporadic injections at varying time points.13,14 In addition, the strict immobilization required with gravity-dependent irrigation systems could hamper patient recovery and mobilization postprocedure. Our experience of a significantly better hematoma clearance rate for patients undergoing active irrigation helps corroborate findings from these studies, with the added advantage of continuous automation of the irrigation process. The double-lumen system incorporates an irrigation port connected to a continuous pump, obviating the need for routine flushing.

A recent large multicenter randomized controlled trial investigated the efficacy of extracranial subperiosteal drain placements compared with that of subdural drain placement, demonstrating nonsignificantly lower hematoma recurrence rates, lower drain misplacement rates, and fewer surgical site infections.15 In our cohort, all patients had subdural drain placement, but given the suggested benefit of extracranial drains, active irrigation with drainage could potentially lead to even better outcomes. Although currently the IRRAflow system is modeled for intracranial spaces only (subdural and intraventricular), it would be interesting to explore outcomes between active irrigation and drainage vs passive drainage in the subperiosteal space. Another new therapy for the management of recurrent cSDH is middle meningeal artery embolization.16 Preliminary studies and early data suggest modest recurrence rates.16 However, much of those data are restricted to patients who had recurrence but were asymptomatic or mildly symptomatic at presentation. For patients presenting with mass effect or severe symptoms, craniotomy or burr-hole evacuation remains the standard of care and was practiced at our institution.

One complication commonly encountered with a passive drainage system is suboptimal drainage flow because of catheter occlusion, leading to repeat irrigation attempts and catheter-related infections.17-19 Interestingly, in the aforementioned study by Sjåvik et al,13 a higher overall complication rate was reported with active irrigation and drainage than passive drainage (14.5% vs 7.2%; P = .019). This is in contrast to our finding of a significantly lower odds of catheter-related infections with active irrigation (OR = 0.051, 95% CI: 0.004 0.697; P = .039). Constant irrigation and flow with automated checks for catheter occlusion could explain this difference.

Catheter-related infections, repeat irrigations, and catheter revisions and replacements are not without expense and need further investigation. In a study by Fargen et al,17 a high per-patient cost was calculated for catheter occlusion. These findings, although pertinent to external ventricular drain use, provide valuable data regarding catheter revisions and occlusions. Using a self-irrigating catheter system attempts to minimize these complications with constant irrigation and drainage at flow rates tailored to individual patients and hematoma status. Active irrigation eliminates blood stagnation and clotting that occur because of slow drainage in a traditional passive drainage setup. By aiding the drainage with active irrigation and eliminating the need for repeat replacements, self-irrigating catheters can potentially help to reduce the occurrence of hemorrhage and infection resulting from catheter revisions and replacements. In addition, to establish safety of this new device, seizure activity was closely monitored in all patients. This is particularly important because patients with cSDH are at high risk for seizures, especially during the postsurgical period when seizure activity is associated with hematoma recurrence and repeat surgical evacuation.20-23 A nonsignificantly higher rate of seizure activity was seen with passive drainage (3 patients [14.3%] vs 0; OR = 0; 95% CI 0.006-2.538, P = .231), suggesting a trend that may show significance with a larger sample size.

Another aspect of our study was investigating the length of the hospital and ICU stays that have been shown to significantly affect mortality and morbidity after surgical cSDH evacuation.18,19 The duration of catheter placement was 4.4 ± 4.1 days in the passive drainage group and 3.7 ± 2.2 days in the active continuous irrigation and drainage (IRRAflow) group. No statistically significant difference was seen for the duration of catheter placement (OR = 0.982; 95% CI [0.936-1.030]; P = .737). Historical data suggest an LOS of 15 to 20 days for patients undergoing surgical evacuation.18,19 Ball et al19 evaluated data for 2010 patients who underwent surgical SDH evacuation and reported a mean total LOS of 10.4 ± 13.1 days. Similarly, Balser et al24 reported a mean total LOS of 13.4 ± 10.2 days. Our result for mean total hospital LOS was nonsignificantly shorter in the active irrigation with drainage group (6.8 ± 3.0 vs 10.6 ± 16.2; OR = 0.993; CI: 0.980-1.006; P = .829). By reducing the catheter-related infection rate for similar lengths of hospital and ICU stays, active irrigation seems promising in aiding short-term management of these chronically ill patients. This is especially important because most of these patients are older and have prolonged hospital stays because of catheter-related infections requiring extended courses of antibiotic therapy. Active irrigation with drainage seems to be beneficial as an adjunct tool that simplifies patient care and improves short-term outcomes.


Our study has limitations, foremost of which is the retrospective and observational nature of patient data. We performed PSM to address this shortcoming. Currently, the IRRAflow system costs approximately $4000, which could be a significant limitation for resource-limited centers. This cost could be potentially offset with lower rates of catheter occlusions requiring less frequent revisions and shorter LOS. Although the chronicity of all subdural hematomas was confirmed on head NCCT, hematoma density was not included as one of the PSM variables. Another limitation is the small sample size post-PSM, which introduces variability in procedural outcomes. Larger, multicenter, prospective trials are currently being planned to address these limitations. Nevertheless, we present key proof-of-concept findings that reflect better hematoma clearance rates with active irrigation and drainage.


Active continuous irrigation with drainage after surgical evacuation for cSDH results in superior hematoma clearance rates and less catheter-related infections than passive drainage alone. In our series, it led to acceptable lengths of hospital stay with fewer catheter-related complications than passive drainage alone.


This study did not receive any funding or financial support.


A. Khan—Research grants: Scoliosis Research Society to study scoliosis in Chiari patients and Neurosurgical Research & Education Foundation (NREF) to study bupivacaine pain pumps in patients undergoing spinal deformity correction. J. M. Cappuzzo—Consulting Fees: Cerenovus, J&J Medical Device Companies; Integra Lifesciences, Corp.; MIVI Neuroscience; Penumbra; Stryker, Corp. Support for attending meetings and/or travel: Stryker, Corp.; Penumbra J. M. Davies–Consulting fees; payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing, or educational events; support for attending meetings and/or travel: Medtronic. Patents planned, issued, or pending: Participation on a Data Safety Monitoring Board or Advisory Board: NIH NIHDS Strokenet. Stock or stock options: Synchron, Cerebrotech, Further relationships disclosed with Rist and Hyperion. E. I. Levy—Shareholder/Ownership Interest: NeXtGen Biologics, RAPID Medical, Claret Medical, Cognition Medical, Imperative Care, Rebound Therapeutics, StimMed, Three Rivers Medical; Patent: Bone Scalpel; Honorarium for Training & Lectures: Medtronic, Penumbra, MicroVention, Integra, Consultant: Clarion, GLG Consulting, Guidepoint Global, Imperative Care, Medtronic, StimMed, Misionix, Mosiac; Chief Medical Officer: Haniva Technology; National PI: Medtronic Steering Committees for SWIFT Prime and SWIFT Direct Trials; Site PI Study: MicroVention (CONFIDENCE Study) Medtronic (STRATIS Study-Sub 1); Advisory Board: Stryker (AIS Clinical Advisory Board), NeXtGen Biologics, MEDX, Cognition Medical; Endostream Medical, IRRAS AB (Consultant/Advisory Board), Medical Legal Review: render medical/legal opinions as an expert witness; leadership or fiduciary roles in other board society, committee or advocacy group, paid and unpaid: CNS, ABNS, UBNS. A. H. Siddiqui—Consulting fees: Amnis Therapeutics, Apellis Pharmaceuticals, Boston Scientific, Canon Medical Systems USA, Cardinal Health 200, LLC, Cerebrotech Medical Systems, Cerenovus, Cerevatech Medical, Cordis, Corindus, Endostream Medical, Ltd, Imperative Care, InspireMD, Ltd., Integra, IRRAS AB, Medtronic, MicroVention, Minnetronix Neuro, Peijia Medical, Penumbra, Q'Apel Medical, Rapid Medical, Serenity Medical, Silk Road Medical, StimMed, LLC, Stryker Neurovascular, Three Rivers Medical, VasSol, Leadership or fiduciary role in other board, society, committee or advocacy group: Secretary—Board of the Society of NeuroInterventional Surgery 2020-2021, Chair—Cerebrovascular Section of the AANS/CNS 2020-2021. Stock or stock options: Adona Medical, Amnis Therapeutics, Bend, IT Technologies, Ltd., BlinkTBI, Inc, Cerebrotech Medical Systems, Cerevatech Medical, Cognition Medical, CVAID Ltd., E8, Endostream Medical, Ltd, Galaxy Therapeutics, Imperative; Care, InspireMD, Ltd., Instylla, International Medical Distribution Partners, Launch NY; Neurolutions, NeuroRadial Technologies, NeuroTechnology Investors, Neurovascular Diagnostics, Peijia; Medical, PerFlow Medical, Ltd., Q'Apel Medical,, Radical Catheter Technologies, Rebound Therapeutics Corp. (Purchased 2019 by Integra Lifesciences, Corp), Rist Neurovascular (Purchased 2020 by Medtronic), Sense Diagnostics, Serenity Medical, Silk Road Medical, Sim & Cure, SongBird Therapy, Spinnaker Medical, StimMed, LLC, Synchron, Three Rivers Medical, Truvic Medical, Tulavi Therapeutics, Vastrax, LLC, VICIS, Viseon Other financial or nonfinancial interests: National PI/Steering Committees: Cerenovus EXCELLENT and ARISE II Trial; Medtronic SWIFT PRIME, VANTAGE, EMBOLISE and SWIFT DIRECT Trials; MicroVention FRED Trial & CONFIDENCE Study; MUSC POSITIVE Trial; Penumbra 3D Separator Trial, COMPASS Trial, INVEST Trial, MIVI neuroscience EVAQ Trial; Rapid Medical SUCCESS Trial; InspireMD C-GUARDIANS IDE Pivotal Trial. R. M. Hess has support from IRRAS. The other authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.


The authors thank Paul H. Dressel BFA for formatting the images and Debra J. Zimmer for editorial assistance.


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Supplemental Digital Content

Supplemental Digital Content 1. Supplemental Methods. Further details about the irrigation and drainage settings and associated safety mechanisms.

Supplemental Digital Content 2. Supplement Results. Subgroup analysis and outcomes for craniotomy and burr-hole cases.


In the present study, the authors investigated the novel utilization of an active drainage system to enhance fluid clearance following operative evacuation of chronic subdural hematoma (cSDH). In an aging population, this is one of the most common pathologies that neurosurgeons encounter and attempt to treat to cure.1a The management guidelines, along with the technology currently employed in the neurosurgical armamentarium, are in flux, particularly with the usage of middle meningeal artery embolization in recent years.2a,3a It is known that the rate of recurrence reported in the literature is between 5% and 33% at long-term follow-up.4a,5a Histological evidence suggests of sustained inflammatory response, formation of neo-membranes, and further propagation of subdural blood and fluid collection as key aspects of the natural history of cSDH.6a

There is level I evidence to support drain insertion as part of standard neurosurgical practice to reduce the risk of re-accumulation.7a Here, the authors use a novel double-lumen automated irrigation system, the IRRAflow, for the drain insertion in 21 patients compared to 34 patients with standard drains. The authors find that this technology improved residual clearance and that it was safely applied with no increased risks to the patients during their hospitalization. Along with faster clearance, there is the potential for shorter inpatient stay along with lower risks of inpatient complications, which we unfortunately observe far too many times in the elderly, comorbid population. This study is a pilot design with a small cohort of patients, but the results overall are positive. Additional data on long-term follow-up are needed for future investigation and validation of the technological benefits. The management of cSDH remains a challenge to the clinician, and as the authors have illustrated, it is an active field of research in a high-risk patient population.

Hansen Deng

Pascal O. Zinn

David O. Okonkwo

Pittsburgh, Pennsylvania, USA


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2a. Haldrup M, Ketharanathan B, Debrabant B, et al. Embolization of the middle meningeal artery in patients with chronic subdural hematoma-a systematic review and meta-analysis. Acta Neurochir. 2020;162(4):777-784.
3a. Ducruet AF, Grobelny BT, Zacharia BE, et al. The surgical management of chronic subdural hematoma. Neurosurg Rev. 2012;35(2):155-169; discussion 169.
4a. Weigel R, Schmiedek P, Krauss JK. Outcome of contemporary surgery for chronic subdural haematoma: evidence based review. J Neurol Neurosurg Psychiatry. 2003;74(7):937-943.
5a. Ramachandran R, Hegde T. Chronic subdural hematomas—causes of morbidity and mortality. Surg Neurol. 2007;67(4):367-372; discussion 372-373.
6a. Edlmann E, Giorgi-Coll S, Whitfield PC, Carpenter KLH, Hutchinson PJ. Pathophysiology of chronic subdural haematoma: inflammation, angiogenesis and implications for pharmacotherapy. J Neuroinflammation. 2017;14(1):108.
7a. Santarius T, Kirkpatrick PJ, Ganesan D, et al. Use of drains versus no drains after burr-hole evacuation of chronic subdural haematoma: a randomised controlled trial. Lancet. 2009;374(9695):1067-1073.

Active irrigation; Chronic subdural hematoma; Drainage; Irrigation and drainage: passive irrigation

Supplemental Digital Content

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