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Original research
Timing of complications during and after elective endovascular intracranial aneurysm coiling
  1. Michelle Masayo Kameda-Smith1,
  2. Paula Klurfan1,2,
  3. Brian Anthony van Adel1,2,3,
  4. Ramiro Larrazabal2,
  5. Forough Farrokhyar1,4,
  6. Michael Bennardo1,
  7. Thorsteinn Gunnarsson1,2
  1. 1 Division of Neurosurgery, Department of Surgery, McMaster University, Hamilton, Ontario, Canada
  2. 2 Department of Radiology, McMaster University, Hamilton, Ontario, Canada
  3. 3 Division of Neurology, Department of Internal Medicine, McMaster University, Hamilton, Ontario, Canada
  4. 4 Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada
  1. Correspondence to Dr Thorsteinn Gunnarsson, Division of Neurosurgery, Hamilton General Hospital 237 Barton, St. E Hamilton, Ontario, L8L 2X2, Canada; thorsteinn.gunnarsson{at}


Objective To determine the time to complications during and after elective endovascular intracranial aneurysm coiling.

Methods A retrospective chart review of patients undergoing elective endovascular aneurysm coiling between March 2006 and October 2013 in one large Eastern Canadian Neurointerventional Service was performed. Data regarding the incidence, time and type of complication related to the endovascular coiling procedure and clinical outcome at last follow-up were collected. Patient, aneurysm and operation factors were analyzed to determine any factors associated with complication occurrence.

Results Of the 150 patient procedures analyzed, 16% experienced a coiling-related complication, although none resulted in death. 6.7% of patients experienced an intraoperative complication, of which thromboembolism was the most common type. The majority of the complications were detected in the first 6 hours after reversal of anesthesia, and a small proportion the next morning prior to discharge. Only 3.3% of patients had persistent neurological deficit after the procedure on last follow-up. Duration of the operation demonstrated a strong association with the occurrence of procedure-related complications.

Conclusion This study demonstrates that coiling-related complications of elective endovascular coiling tend to occur either intraoperatively or are detected shortly after reversal of anesthesia. Further investigation with a larger cohort may help to guide important preoperative communication with patients and identify a select group of patients who may not necessarily require prolonged admission to hospital for observation.

  • time to complication
  • unruptured intracranial aneurysm
  • coiling
  • day surgery
  • endovascular

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Endovascular coil embolization of unruptured intracranial aneurysms (UIA) has become a well-established treatment modality.1 2 Recent advances in the technology of endovascular neurosurgery and neuroimaging have resulted in a large increase (ie, doubling) in the number of elective endovascular procedures for UIA.3 4 Paralleling the increase in incidental aneurysms detected is the increased demand on the healthcare system to treat aneurysms with a risk of rupture greater than the risks associated with surgery.

Unfortunately healthcare budgets are not without limits. Recently, the Canadian Ministry of Health has observed healthcare costs increasing at a much faster rate than any government in Canada can fund.5 These financial limitations challenge many ethical principles of beneficence and distributive justice. As a result, some surgical subspecialties have welcomed the ever-evolving concept of day case surgery. Numerous benefits have been associated with day case surgery including (1) reducing patient exposure to nosocomial infections, risk of thromboembolism and exposure to medical error; (2) cost efficiency (ie, eliminating the risk of cancellation of elective procedures secondary to bed shortages and perhaps affecting the length of waiting times); and (3) cost effectiveness (ie, one night in a hospital surgical ward bed estimated at approximately $1200 CDN).6 7

Despite numerous studies suggesting the safety of day case surgery, neurosurgery has been slow to adopt this paradigm. Barriers in developing widespread use of neurosurgical day case procedures include substantial concern regarding medicolegal risks associated with patients in whom late complications develop while at home, resulting in delayed treatment and a worse outcome.7 Many studies, however, have demonstrated that, in the right patient, undergoing selected neurosurgical procedures (eg, awake mini-craniotomy for brain tumor resection/biopsy, spinal decompression, mini-craniotomy and clipping of an anterior circulation aneurysm), late complications are rare.7 Also, after endovascular treatment of a UIA, patients have been found not to require routine ICU monitoring post-procedure.7–10 In terms of timing to complication, Burrows and colleagues were the first to make the observation that most of the complications associated with the coiling procedure were evident either during the procedure or on awakening from anesthesia.9 Zakhari et al have also recently demonstrated that patient discharge the day after elective aneurysm treatment was not associated with an increase in post-discharge adverse events.11 Anecdotally, this has also been the experience at our center, so we set out to determine the incidence and timing of complications during and after elective endovascular intracranial aneurysm coiling.


A retrospective chart review of the elective aneurysm coiling procedures between March 2006 and October 2013 was conducted after ethics approval was granted by the Hamilton Integrated Research Ethics Board. To maximize the sample size, all consecutive patients undergoing simple straightforward elective coiling procedures by the senior authors at one Eastern Canadian Neurosurgical Institution were included. All cases were completed by experienced staff neurointerventionalists. Cases excluded from the analysis were procedures where flow diverting stents or stent-assisted coiling procedures were used, parent vessels were sacrificed as part of the treatment for the aneurysm, unsuccessful coiling attempts and aneurysm associated with arteriovenous malformations or dural arteriovenous fistulas. Data were collected using the notes from the electronic health records at our institution, which also include copies of all paper charts.

Statistical analysis

Categorical variables were reported as counts and proportions and compared using the Χ2 or Fisher test. Continuous variables were reported as mean (SD) or median (minimum, maximum) if not normally distributed and compared using the independent samples t-test or Mann–Whitney U test as appropriate. To compare the means of multiple groups, ANOVA or the Kruskal–Wallis test was employed. The complication rate with corresponding 95% CIs using the Wilson method were calculated and reported. Kaplan–Meier analysis was then used to generate the cumulative complication-free rate with 95% CIs. Log-rank test was used to compare the between-group complication-free rates. Cox proportional hazard regression analysis was conducted to explore the potential predictors of the complication. Hazard ratios (HR) with 95% CIs and p values were reported. The level of significance was set at 0.05. SPSS software ( was used for analysis.


Patient demographics

There were 150 patient procedures included in the analysis. The mean (SD) age at the time of operation was 56.5 (11.5) years (range 12–82 years). Of 150 patient procedures, 74% of patients were women and 26.7% had undergone a previous endovascular procedure with one patient undergoing five procedures over the 7.5 years of data acquisition (table 1). Overall, 67.3% of the procedures were for aneurysms in the anterior circulation. The mean (SD) size of the aneurysm was 9.7 (4.8) mm (range 2.8–31 mm). Six patients were lost to follow-up at the time of data analysis.

Table 1

Patient demographics and baseline characteristics (n=150)

Operation and admission details

The most common elective aneurysm to be coiled were aneurysms of the anterior communicating artery (22.7%). The mean (SD) operative time (ie, time from arriving at the angiographic suite to departing) was 3.15 (0.9) hours (range 1–6 hours). As most were admitted on the day of coiling, the mean (SD) number of days in hospital and days in hospital postoperatively were similar at 2.95 (15.4) and 2.69 (15.5) days, respectively. Both values were skewed by one patient who was admitted for 190 days following a postoperative thalamic infarct. Removing this outlier, the mean number of days in hospital and in hospital postoperatively were 1.65 (1.8) and 1.43 (1.2), respectively. The median number of days in hospital was 1 day, with 118 of 150 patient procedures (78.7%) being discharged home the following day, including nearly half of the 16% of patients who experienced a coiling-related complication (table 2).

Table 2

Operation and admission details (n=150)

Coiling-related complications

Of 150 procedures, 24 patients (16%, 95% CI 11.0% to 22.7%) experienced coiling-related complications (table 3). The time to first complication was divided into three time intervals. Of 24 coiling-related complications, 6.7% of patients experienced an intraoperative complication, 5.3% experienced a complication after the operation during inpatient stay and 4.0% experienced a complication after discharge. The most common complications were new neurological symptoms (n=6), thromboembolism (n=6) and medical complications (n=6). Of the 24 patient procedures experiencing any procedure-related complications, only 20.8% had persistent deficits at last follow-up. Overall (ie, of the 150 patients in this cohort), only 3.3% of patients demonstrated persistent deficits (table 4, figure 1). The duration of the procedure demonstrated a tendency towards complication occurrence (table 5).

Table 3

Coiling-related complications 

Figure 1

Pesistent, transient and no postoperative deficits in patients undergoing endovascular coiling.

Table 4

Patients with persistent neurological deficit. Size of aneurysm refers to the filling portion

The Kaplan–Meier curve in figure 2 demonstrates the cumulative complication-free rate for all patients in the analysis. Of 150 patients, 88% (95% CI 82% to 93%) of the patients were complication-free at 24 hours post-surgery and at 192 days follow-up period. The curve at time 0 starts at 93.3%, accounting for the 6.7% of intraoperative complications. Then, from the time after anesthesia reversal and extubation, the majority of complications occur prior to 6 hours with another group alerting nursing or medical staff the next day. The curve plateaus after 24 hours post-surgery at 88% complication-free rate.

Figure 2

Kaplan–Meier curve of cumulative complication-free rate for all patients in the analysis.

Predictors of coiling-related complications

The only potential predictor of coiling-related complications was longer operation time (HR 1.8; 95% CI 1.2 to 2.6, p=0.002), which translates into an approximately twice higher risk of complications for each hour increase in time in the operating room (table 5) . Gender, age, previous coiling, number of previous coiling procedures, location of aneurysm and largest aneurysm dimension were not significant. Figure 3 demostrates the lenght of stay in hospital between patients who experienced complications vs. those who did not.

Table 5

Univariate analysis of patient characteristics and occurrence of complications

Figure 3

Length of stay in hospital.


This study has confirmed our anecdotal experience and Burrow’s assertion that, in the infrequent instance that a coiling-related complication associated with an elective aneurysm coiling occurs, it is during the procedure itself or shortly thereafter.9 The coiling-related complication rate was 16%, although most were minor with no long-term morbidity and no deaths.


Complications associated with coiling were subcategorized according to their type (ie, neurological symptom of unknown etiology, thromboembolic, medical, groin hematoma, vasospasm, iatrogenic cervical artery dissection, psychiatric, intraoperative rupture and mass effect) and timing (ie, intraoperative, postoperative/pre-discharge and post-discharge). The types of complications encountered in this study have been well documented after endovascular treatment of aneurysms.12–14 The systematic review and meta-analysis by Naggara et al found the overall risk of an adverse outcome after endovascular treatment of UIA was 4–5%.13 In their study, unfavorable outcome was defined as disability at 1 month by the modified Rankin scale (mRS) >2, Glasgow Outcome Scale (GOS) >2 or World Federation of Neurosurgeons (WFNS) scale >2, or a loss of 1 point in patients with prior deficits of either mRS, GOS or WFNS. Comparatively, our patient population experienced a significantly lower rate of permanent deficit at first follow-up of 3.3%. Of note, in the review by Naggara et al they found that patients with unfavorable outcomes were significantly older.13 Since their review, Zakhari and colleagues have published their single-center experience of complications of elective UIA coiling. In their group of 97 patients the length of stay was 2.52 days with no significant difference in post-discharge adverse outcome rates between early (<2 days) and standard (>2 days) discharge groups.11

In terms of adverse outcomes, overall hospital mortality has been documented to range between 0.57% and 1.7%.12–14 No deaths occurred in our patient cohort as a result of their elective endovascular aneurysm coiling procedure. Alshekhlee and colleagues detailed the types of complications encountered during and after endovascular coiling of UIA. They found that the rates of complications following elective UIA coiling were associated with intracerebral hemorrhage (1.37%), postoperative stroke (2.92%), hydrocephalus (1.26%), pulmonary complications (0.83%), cardiac complications (2.12%), systemic infection (0.09%) and acute renal failure (0.91%).12 In contrast to these types, we found our patients experienced a new neurological symptom of unknown etiology (4%), thromboembolic events (4%), medical complications (4%), groin hematoma (2%), vasospasm (1.3%), iatrogenic vertebral artery dissection (1.3%), psychiatric complications (1.3%), intraoperative rupture (0.7%) and mass effect (0.7%). It is difficult to compare the rates of the types of complications with our group of patients as a thromboembolic event visualized during the procedure did not in most cases cause a new associated neurological deficit but was included as an event in our study. As a result, our figures may be inflated, capturing all the events regardless of clinical sequelae.

Time to complications

Thromboembolic and hemorrhagic complications are not infrequent during endovascular procedures for intracerebral aneurysms but can be promptly recognized and treated in the angiographic suite, thus resulting in a low rate of permanent comorbidity and mortality. Burrows et al found that most complications associated with elective endovascular coiling were evident during the procedure or on awakening from anesthesia.9 In order to better delineate the timing of coiling-related complications in our group, we analyzed those that occurred intraoperatively, postoperatively prior to discharge (ie, during their hospital stay after anesthesia reversal) and post-discharge.

Naggara and colleagues found that peri-procedural complications associated with endovascular coiling of UIA occurred at a rate of 7.6% for thromboembolic events, 2.6% for perforation or rupture and 3.0% for device-related problems.13 In comparison, only one patient in our group experienced an intraoperative perforation (0.7%) and thromboembolic events were noted in 2.4% of the patients intraoperatively.14 In terms of timing, the Kaplan–Meier curve in figure 2 shows that 6.7% of complications occurred intraoperatively. Thereafter, from the time after anesthesia reversal and extubation, the majority of complications occur prior to 6 hours with another group alerting nursing or medical staff the next day.

Feasibility of day case endovascular coiling for UIA

Day case surgery is a continually evolving specialty in line with the changing demands of the modern health service. In the context of limited healthcare resources, it is of paramount importance to determine the most efficient and cost-effective ways in which to deliver elective surgical care. It is equally important to ensure that such cost-effectiveness solutions are well tolerated by patients.10

One reason for the reluctance of many neurosurgeons to consider day case surgery appears to be the perception that patients would be placed at risk by early discharge. This primarily relates to the potential for development of postoperative complications that may cause rapid deterioration in the patient’s condition, necessitating prompt diagnosis and treatment if death and long-term sequelae are to be avoided.10 On the other hand, however, hospital admission is not a decision to be taken lightly.

In carefully selected patients there has been no reported case of a patient having a negative outcome as a result of early discharge in the field of neurosurgery, including post-craniotomy and clipping of UIA.7 8 10 15 16 In the study by Goettel et al on patients undergoing craniotomy and clipping of UIA, 67% were successfully discharged home on the day of surgery.8 In support of recent trends towards day case surgery, qualitative studies on neurosurgical patients’ perception of outpatient craniotomy have shown high patient satisfaction with approximately half of these patients believing they would recover more quickly and more comfortably at home.16

The real potential advantages of performing such surgical procedures on a day case basis include: more efficient and cost-effective, elimination of the risk of postponement of surgery due to lack of bed availability, reduction of case cancellation, reduced waiting times for surgery, reduced risk of nosocomial infections, thromboembolic complications and medical error.7 This benefits the patient, surgeon and flow of the healthcare system as a whole.7

To our knowledge, this is the first study to delineate the timing of complications associated with elective endovascular treatment of an intracranial aneurysm. We hope to follow on with a prospective registry of patients deemed suitable for day case surgery and evaluation of which patient subgroups undergoing elective endovascular treatment of an intracranial aneurysm can successfully and safely be discharged home on the same day as their surgery.

Study limitations

As a feasibility study, the lack of sample size calculation limits the conclusions that can be made with regard to associated risk factors for elective coiling-related complications as this was a secondary objective of the study. Accordingly, this study is underpowered to draw any definite conclusion from the findings. This will be observed more formally in the prospective registry. Also, as a retrospective chart review, the data, though complete, are prone to all the biases associated with the nature of the study. Despite these limitations, we explored a novel question, being the first to address the feasibility of a day surgery service for elective intracranial aneurysm coiling.


In our patient cohort, coiling-related complications after elective endovascular intracranial aneurysm coiling occurred either intraoperatively or were detected shortly after reversal of anesthesia. These findings warrant further investigation with a larger cohort to guide preoperative communication with patients and to identify a select group of patients who may not necessarily require a prolonged hospital admission for observation.


The authors thank all the individuals who contributed to the study or manuscript preparation but did not fulfil all the criteria for authorship.



  • Contributors MMK-S, TG, PK, BAvA, RL and FF conceived and designed the study. MMK-S and MB were involved in the data acquisition. FF performed the data analysis and interpretation of data was performed by MMK-S, FF, TG, PK, BAvA, RL. The final draft was written by MMK-S. Draft revisions, approval and agreement to be accountable for all aspects of the work were reached by all the named authors.

  • Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Ethics approval Hamilton Integrated Research Ethics Board (HiREB).

  • Provenance and peer review Not commissioned; externally peer reviewed.