Unique Neurosurgical Morbidity and Mortality Conference Characteristics: A Comprehensive Literature Review of Neurosurgical Morbidity and Mortality Conference Practices with Proposed Recommendations

Journal Pre-proof Unique Neurosurgical Morbidity and Mortality Conference Characteristics: A Comprehensive Literature Review of Neurosurgical Morbidity & Mortality Conference Practices with Proposed Recommendations Ilya Rybkin, Ida Azizkhanian, James Gary, Chad Cole, Meic Schmidt, Chirag Gandhi, Fawaz Al-Mulfti, Patrice Anderson, Justin Santarelli, Christian Bowers PII:

S1878-8750(19)32864-5

DOI:

https://doi.org/10.1016/j.wneu.2019.11.028

Reference:

WNEU 13697

To appear in:

World Neurosurgery

Received Date: 29 July 2019 Revised Date:

4 November 2019

Accepted Date: 5 November 2019

Please cite this article as: Rybkin I, Azizkhanian I, Gary J, Cole C, Schmidt M, Gandhi C, Al-Mulfti F, Anderson P, Santarelli J, Bowers C, Unique Neurosurgical Morbidity and Mortality Conference Characteristics: A Comprehensive Literature Review of Neurosurgical Morbidity & Mortality Conference Practices with Proposed Recommendations, World Neurosurgery (2019), doi: https://doi.org/10.1016/ j.wneu.2019.11.028. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Elsevier Inc. All rights reserved.

Title Unique Neurosurgical Morbidity and Mortality Conference Characteristics: A Comprehensive Literature Review of Neurosurgical Morbidity & Mortality Conference Practices with Proposed Recommendations Ilya Rybkin1 (corresponding author, [email protected]) Ida Azizkhanian1 James Gary2 Chad Cole3 Meic Schmidt3 Chirag Gandhi3 Fawaz Al-Mulfti3 Patrice Anderson4 Justin Santarelli3 Christian Bowers3 1

New York Medical College, Valhalla, NY 10595 Albert Einstein College of Medicine, Bronx, NY 10461 3 Department of Neurosurgery, Westchester Medical Center, New York Medical College, Valhalla, NY 10595 4 Department of Surgery, Westchester Medical Center, New York Medical College, Valhalla, NY 10595 2

Academic Degrees Ilya Rybkin, MS Ida Azizkhanian, MS James Gary, BS Chad Cole, MD, MSc Meic Schmidt, MD, MBA Chirag Gandhi, MD Fawaz Al-Mulfti, MD Patrice Anderson, MD Justin Santarelli, MD Christian Bowers, MD

Rybkin 1 Title Unique Neurosurgical Morbidity and Mortality Conference Characteristics: A Comprehensive Literature Review of Neurosurgical Morbidity & Mortality Conference Practices with Proposed Recommendations Ilya Rybkin1 (corresponding author, [email protected]) Ida Azizkhanian1 James Gary2 Chad Cole3 Meic Schmidt3 Chirag Gandhi3 Fawaz Al-Mulfti3 Patrice Anderson4 Justin Santarelli3 Christian Bowers3 1

New York Medical College, Valhalla, NY 10595

2

Albert Einstein College of Medicine, Bronx, NY 10461

3

Department of Neurosurgery, Westchester Medical Center, New York Medical College, Valhalla, NY

10595 4

Department of Surgery, Westchester Medical Center, New York Medical College, Valhalla, NY 10595

Academic Degrees Ilya Rybkin, MS

Rybkin 2 Ida Azizkhanian, MS James Gary, BS Chad Cole, MD, MSc Meic Schmidt, MD, MBA Chirag Gandhi, MD Fawaz Al-Mulfti, MD Patrice Anderson, MD Justin Santarelli, MD Christian Bowers, MD

Keywords Morbidity and Mortality; Complication Grading; Complication Scale; Adverse event; Complication; Surgical Complexity; Frailty

Abbreviations AE: Adverse event ASA: American Society of Anesthesiologists CCI: Charlson Comorbidity Index CSF: Cerebrospinal fluid DVT: Deep vein thrombosis EBL: Estimated blood loss HRQL: Health related quality of life IC: Intensive care ICU: Intensive care unit

Rybkin 3 KPS: Karnofsky Performance Status LOS: Length of stay M&M: Morbidity and mortality MCS: Milan complexity scale mFI: Modified frailty index mRS: modified Rankin Scale NIHSS: National Institutes of Health Stroke Scale PE: Pulmonary embolism PTD: Pathology treatment difficulty QOD: Quality Outcomes Database STS: Society of Thoracic Surgeons Disclosures: Conflict of interests: none This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Abstract

Objective: The aim of this study was to review the literature for neurosurgical complication definitions and to report the current scales used for classifying these complications, as well as to discuss their limitations. Methods: A systematic review was performed through a PubMed search using predetermined Mesh Terms and inclusion criteria. Papers meeting inclusion criteria were specific to the field of neurosurgery and presented a unique complication grading scale. Results: There are 2,156 PubMed results that match our pre-determined Mesh Terms. Of those, 7 met our inclusion criteria and were published from 2001 to 2019. Four studies are applicable to

Rybkin 4

general neurosurgery, two for spine surgery, and one for neuroendovascular surgery. Scales are based on therapy needed to treat, predictability and avoidability, survey/consensus of expert judgement, and the underlying cause of an adverse event. None of these studies takes into account the complexity of the surgery or the frailty of the patient in the final grading score.

Conclusions: There is no current standardized neurosurgical complication grade used throughout morbidity and mortality conferences. Although there are proposed scales in the literature, each with their strengths and limitations, none of these take into account surgery complexity or patient frailty and comorbidity. We advocate for a comprehensive scale that includes a pre-operative grading system factoring baseline surgical complexity as well as patient frailty.

Introduction Morbidity and Mortality (M&M) conferences are peer-reviewed and medicolegally protected forums for presenting and discussing complications, elucidating potential sources of error, assigning and classifying blame, and educating faculty, residents, and other ancillary staff with the objective of reducing or eliminating the repetition of similar preventable negative outcomes. Although individual hospitals, and the Accreditation Counseling for Graduate Medical Education all require these regularly scheduled formal peer-reviewed M&M conferences, a great deal of heterogeneity exists in how M&Ms are conducted across the healthcare system.1,2 The literature is rife with the terms ‘adverse event’ and ‘complication’, yet no standardized definitions exist for these labels, and there is no consensus as to a grading system or classification schema. Although data from M&M conferences can yield valuable information regarding trends in morbidity, and can potentially uncover areas in need of improvement, this

Rybkin 5 data is typically not systematically collected or stored,3 probably in large part due to concerns about medicolegal ramifications if ever published or analyzed outside of the M&M setting. Subsequently, comparison of complication rates between different hospitals, or even between different time periods within the same institution, is usually not possible .4–6 There are four different archetypes of patient outcomes that have been described: expected successes, unexpected failures, unexpected successes, and expected failures.7 Typically, unexpected failures are of the greatest interest with regards to M&M analysis and discussion, as these outcomes may be the most amenable to prevention with appropriate modifications in clinical practice. Unfortunately, due to the lack of any standardization or consensus of the definition of what constitutes a neurosurgical complication, identifying an unexpected failure is frequently variable depending on who is making the classification determination and ultimately unclear and inconsistent with little interobserver reliability. The aims of this paper fall under two scopes: we first report the various definitions of ‘complications’ within the literature, followed by a review of published neurosurgical M&M classifications. The strengths and limitations of these scales are discussed before we introduce our proposed modifications.

Methods This systematic review was conducted with the Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines. We performed a PubMed search to identify studies that met our predetermined inclusion criteria for studies: must be specific to the field of neurosurgery and must propose a unique complication grading scale. The Mesh Terms “neurosurgical procedures/ adverse effects” and “postoperative complications” were used in the initial query in combination

Rybkin 6 with boolean operator AND. For completeness of search, the Mesh Terms “orthopedic procedures/ adverse effects” and “spine/surgery” were searched in combination with boolean operator AND to ensure inclusion of studies written by orthopedic specialists with whom neurosurgeons share expertise on spinal procedures. Papers listed from those searches were screened by title to exclude studies not presenting unique classification systems for complications of neurosurgical procedures. The remaining articles were included in the review. Two independent reviewers (IA and IR) performed these steps and obtained the same list of final articles. The results of this search yielded articles that are presented in a narrative summary.

Results The Mesh Terms “neurosurgical procedures/ adverse effects” and “postoperative complication” in Pubmed yielded 1,672 results, 6 of which were on a systematic complications scale for neurosurgical procedures and therefore included in this paper. The Mesh Terms “orthopedic procedures/ adverse effects” and “spine/surgery” yielded 484 results, 1 of which was a paper on a complications grading system for spine surgery. 2149 articles were excluded since they did not propose a unique complication grading scale, they were not relevant to neurosurgical (cranial/spinal/endovascular) procedures, or they were not in English. In total, 7 publications were included for proposing a unique complications grading scale of neurosurgical procedures (see table 1). Two studies are unique to spinal procedures and include input from orthopedic as well as neurosurgical specialists while the other five papers are written solely by neurosurgeons.

Defining complications The first step in any M&M proceeding is to identify the criteria for defining a

Rybkin 7 complication. Complication rates will vary tremendously based on the definition. An overly broad definition encompassing any possible deviation from an absolute perfect and idealized hospital course results in an overinflated complication rate. This is unnecessarily cumbersome, particularly when there are no significant clinical differences accompanying such deviations (e.g. a patient needed to have an increase in oral as needed pain medication due to post-operative pain). Likewise, if excessively narrow parameters for defining a neurosurgery complication exist, such as only unexpected mortality, then this threshold would exclude multiple severe negative outcomes that are clearly M&Ms. To highlight the different definition parameters of neurosurgical complications, Hamilton’s definition is “any untoward event occurring to a patient while on the neurosurgical service”. These M&M classifications that are so broadly inclusive result in higher complication rates than the narrower M&M criteria for defining complications.8 Sokol and Wilson define a complication as “any undesirable, unintended, and direct result of an operation affecting the patient, which would not have occurred had the operation gone as well as could reasonably be hoped”.9 However, any expected untoward events are excluded from their definition. Similarly, Faciszewski only record some complications that persist for more than 6 months since in some instances to achieve the best surgical goal, a surgical approach may be used where transient (<6 months), but not permanent neurological deficits are expected.10 For example, post thoracotomy pain syndrome after a routine thoracotomy would not be categorized as a complication if the pain lasted for less than 6 months because that is a frequent, normal, and expected result of that specific surgery, regardless of how undesirable or painful it is for patients. The authors state that expected post-procedural events that should not be classified as complications unless the threshold of a non-routine intervention was necessary to mitigate the event.10 Pleural effusions

Rybkin 8 following chest tube removal after a thoracolumbotomy were not considered complications unless the effusion required a thoracocentesis or placement of another chest tube because a threshold of another procedural intervention was met. This method relies on expected outcomes, which is a reasonable way of defining when a neurosurgical complication has occurred. A differing complication classification system by Landriel Ibañez et al. includes expected adverse outcomes, even when they are assumed to be unavoidable results of a particular procedure (e.g. such as very mild transient facial paralysis (House-Brackmann II/VI) following resection of a giant 5 cm acoustic neuroma.)4 One fundamental problem in the neurosurgical M&M literature is that the terms ‘adverse event’ and ‘complication’ are used interchangeably despite having different meanings.11 Rampersaud et al. defines an adverse event (AE) as an unexpected or undesirable event occurring as a result of surgery.11 By contrast, a surgical complication is defined as a disease or disorder that is a surgical consequence that negatively affects a patient’s outcome.11 They add that not every adverse event will result in a complication, and reported that a 14% AE rate resulted in a 3.2% complication rate (a sterile field contamination will not necessarily result in a postoperative infection). The general assumption is that most minor adverse events do not result in complications, and they report that 77% of adverse events were complication free.11 Despite this, they state that is important to document every adverse event as it occurs in order to prevent potentially poor outcomes. Overlooking and not documenting what may otherwise be thought of as inconsequential adverse events could result in complacency and a false sense of security. This is especially true in the field of neurosurgery, wherein relatively small deviations in the intraoperative or postoperative course can result in catastrophic outcomes. Prospectively defining adverse events pre-operatively and then subsequently

Rybkin 9 documenting them postoperatively, developing protocols to reduce the incidence of such adverse events, and then tracking and analyzing complication rates can result in improved patient safety. However, identifying adverse events does not necessarily mean there are solutions for eliminating their occurrence. It is well established in the literature that complex cranial skull base or corrective spinal deformity procedures in neurosurgery have considerably higher risks than routine procedures in other surgical specialties and some adverse events may be unavoidable and may have to be considered as part of a surgical procedure.4,12 Clavien et al. define complications as any deviation from the normal postoperative course, including asymptomatic deviations such as arrhythmia and atelectasis.13 The authors define a sequela as any effect of a surgery which is inherent to the nature of the surgery, such as an inability to walk following a leg amputation.13 A failure to cure occurs if the original goal of the surgery is not achieved, such as the persistence of residual tumor following a surgery that was attempting a gross total resection.13 According to the authors, sequela and failure to cure should not be included in a classification system of complications, as they are not complications. Similarly, Ferroli et al. propose that undesired outcomes should be classified under three categories: complications, sequelae, and incomplete cures.14 As they state, one center’s complication rate varies dramatically from 10% if including sequelae (transient neurological deficits which resolve by the time the patients are discharged), to 2% if these cases are excluded. The definition of transient versus permanent neurological deficits merits its own review paper, but is briefly addressed in this paper also. A clear demarcation between sequelae and complication is vital when trying to eliminate the confusion in the literature regarding neurosurgical complications. Baron et al. subclassified complications as medical or surgical based on whether they

Rybkin 10 result directly from the technical aspects of a surgical procedure (e.g. errant pedicle screw in spine surgery hits a nerve root causing new unexpected post-operative weakness) or as a result of a medical complication during the recovery (e.g. post-operative pneumonia in a spine surgery patient who had a prolonged postoperative period on a ventilator due to a long deformity correction surgery) in their adult spinal deformity surgery paper.15 Medical complications were defined as “pathologic processes that affect the patient that occur during or around surgery for spinal deformity that are not directly related to surgical technique”.15 Brock et al. state that it is necessary to report whether a patient’s post-operative health decline is from a medical complication, as these should be excluded from statistical analysis of postoperative complications.16 They state that a pulmonary embolism (PE) may occur postoperatively as patients may be bedridden but not every non-ambulatory patient will develop a PE. Since such events are a result of numerous variables and contributory causes, and indirectly related to surgery, excluding such cases would provide a more accurate reflection of the technical neurosurgical culpability of a specific surgeon. Broggi et al. scrutinized excluding such cases however, stating that although a PE is not directly related to surgery, it should be counted as a surgical complication since they would not have developed the PE in the first place if they never underwent the surgical procedure.17 A similar argument is made regarding infection; Brock et al. would consider a post operative infection as a medical complication which would be excluded from statistical analysis, whereas Broggi et al. considers such an exclusion as incorrect. It is important to consider that some complications, for example deep vein thromboses (DVT)/PE may be directly dependent on a lack of postoperative resources (such as no physical therapists to ambulate patients) rather than surgical skill.

Rybkin 11 Timeframe of complication recording Another critical metric that has significance variance in the neurosurgical M&M literature is the length of the post-operative time period where a negative outcome gets classified as a complication. The literature contains a variety of differing proposals, with 30 days, 6 months, and 1-year as the most-commonly reported intervals.4,11–13,18,19 A shorter timeframe such as 30 days is pragmatic because the important details and nuances regarding a patient’s case may become forgotten over time while the most details will be recalled when the case is recent. Increasing the length of time for capturing complications will increase complication detection at the expense of forgetting proximate clinical nuances details. Furthermore, imperfect medical records found in a retrospective chart review are relied on to a greater degree as time lapses. The reason for considering a longer period for defining complications is illustrated by one paper that noted that 13.7% of their patients had complications more than 90 days postoperatively.6 Therefore, a 30 day surveillance period could inherently miss serious complications.

Grading complications One of the biggest problems with the current lack of standardization in neurosurgical complication classification is the absolute inability to compare outcomes among different institutions.4 This is further compounded by the absence of any preoperative expected complication risk stratification that is based on case complexity or difficulty. Outcome reporting based on subjective criteria and ambiguous classifications such as “minor” or “major” complications can be vague and can group complications together that consist of widely varying severities. Additionally, varying degrees of surgical culpability and complications can be grouped together without factoring in the variable pre-operative anticipated complication rate

Rybkin 12 (e.g.- burr hole evacuation of a chronic subdural hematoma would be expected to have a much lower complication rate than a brain-stem cavernous malformation resection). However, the need for complication grading has at least been recognized as a number of varying grading systems have been proposed.4,11,12,18,20–22 These proposed classification systems are based on the severity of treatment rendered for a given complication, the extent of days added for the overall hospital length of stay, the transient or permanent nature of a deficit or detrimental effect, the need for further reoperation, the predictability and avoidability of the complication, or some combination of these factors. More recently, a novel system based on type of error transpiring rather than the presence or severity of a negative outcome has also emerged.20,21 The type of error which transpired can be important to note and record since sometimes an M&M may not have occurred at all, but an M&M event should be noted because erroneous clinical decision making could have led to a major complication and sheer luck prevented that from occurring. One example is no cerebrospinal fluid (CSF) leak occurring after a delayed opening of a lumbar drain to reduce CSF volume/pressure following a tegmen dehiscence/CSF otorrhea case. Although there was no leak, the type of error that occurred was egregious; not ensuring CSF drainage actually occurred, and an important learning opportunity would be lost if this scenario was not considered an M&M. First neurosurgical classification system In 2001, Bonsanto et al. categorized adverse events as either a neurosurgical complication, neurosurgically complicated course, or a medical nonsurgical complication.22 A neurosurgical complication was one defined as unexpected with regards to the natural course of a disease, but known within the literature to occur. A neurosurgically complicated course is one

Rybkin 13 which is expected due to the pathology and location of a lesion. A medical non surgical complication is a medical complication, necessitating additional treatment during the hospital course.4,22Although this system was proposed specifically to address the need of a classification for neurosurgical complications, the framework is lacking in not accounting for complication severity.21 Therapy required to treat Clavien et al. proposed a 4-scale system in 1992, and an amended, standardized 5-scale classification system in 2004 (Clavien-Dindo Classification) in an attempt to establish an objective complication reporting system that eliminated subjectivity and imprecision.13,19 Their scale is graded logically by classifying complications based on the increasing intensity and seriousness of the treatments required to address them following a deviation in a normal expected post-operative course. Although the scale was proposed for general surgery complications, it has been adopted and modified for classifying neurosurgical complications as well, with Landriel Ibañez et al. basing their 4-scale grading system on this ‘therapy required to treat’ model. Another spine-surgery classification system by Rampersaud et al. uses the severity of treatment necessary, with the addition of the effect on hospital length of stay, and the presence of long term sequelae, defined as a deficit existing for longer than 6 months following surgery, to classify complications.11 Although this model includes treatment severity as a criteria for complication grading, the criteria itself are subjective (what constitutes minimal treatment vs.

Rybkin 14 significant treatment is not defined and is ambiguous). One major advantage of scales based on therapeutic interventions is that treatments received are typically well-documented and are evident on chart review while certain adverse events may be overlooked, especially when considered minor in nature. By using therapeutic interventions to classify adverse events, more of the significant complications will be documented. This treatment-based stratification additionally helps to differentiate complications that have the same label (e.g.post-craniotomy hematoma) but very different results and subsequent hospital courses (e.g. one hematoma evacuated surgically with return to OR while the other is managed with observation). Despite the popularity of Clavien-Dindo grading scale among surgical centers, the system is not applicable to all patient populations. For example, increasing complication severity based on the grading system was not associated with inferior postoperative health related quality of life (HRQL) scores or increased estimated blood loss (EBL) in a cervical deformity series nor was there an association with increased length of stay (LOS).6 This is thought to be because the scale lacks validity for intraoperative complications and complications occurring beyond the 30 day post-operative period.6 It must be noted however, that LOS was eliminated from the classification schema of the 2004 Clavien scale as well as the Landriel Ibañez scale, as LOS varies greatly among different hospitals for a variety of non-complication based factors, including insurance status, and is frequently not a good indicator of neurosurgical M&M. Another key limitation of these grading systems is that they do not permit more than one complication to be assessed, as only the major complication is considered, even when multiple complications are present. For example, a patient with a single grade III complication is considered to have sustained greater morbidity than a patient with several grade II

Rybkin 15 complications.6 Furthermore, a lack of treatment is not necessarily synonymous with an absence of morbidity. These systems would classify serious neurosurgical complications, such as hemiplegia following craniotomy for a tumor resection as low-grade only because there is no surgical treatment required to fix it.23 This limitation has been shown by a report’s observation that individuals with a Landriel Ibañez score of 1 had worse discharge health as compared to grade 2 complication patients.24 The grading system’s inability to always correlate with the complication severity is highlighted with an example of a grade 1 complication such as an ischemic lesion caused by poor technical surgical execution that does not require intervention because there is no treatment or way to correct it, but the result could be profound, severe, and permanent neurological impairment that would not be reasonably expected to occur, while a grade 2 complication could require an intervention but still have an excellent prognosis, such as when a spinal hematoma needed to be drained after spine surgery.

Complication Permanence In the Clavien-Dindo scale, a complication grade can be modified with a suffix “d”, indicating presumed long-lasting disability, defined if a patient suffers from a complication at the time of discharge. The Landriel Ibañez scale includes the modifiers suffix “t” for transient, and “p” for persistent. A transient complication is a new neurological deficit which improves within 30 days of a surgical procedure, contrasted from a persistent complication which extends past this time frame. Rampersaud’s scale defines long-term sequelae as lasting greater than 6 months, one of the criteria if met, is sufficient to classify a complication as “major” according to their system. One of the inherent limitations of treatment based complication classification systems is that

Rybkin 16 they don’t distinguish between complications which are defined as permanent/persistent and temporary/transient complications. For example, two patients with the same deficit may have Grade III scores based on the interventions rendered. However, one patient’s deficits may resolve entirely within a span of months, while the other’s deficits may persist permanently and surprisingly their complication grades would be and remain identical. In such cases, all complications persisting past the time frame for transiency would be subsequently labeled as permanent, even if the deficits eventually subside somewhat after a year.4 Houkin et al. define morbidity as transient if the symptoms resulting from a complication resolve within 1 year of the surgical procedure. Other authors have assigned a range of severity to complications based on time to recovery from deficits. Steiger described a complication as moderate if the sequelae resolved within 3 months of surgery. Severe complications were any events which resulted in deficits lasting greater than 3 months or those complications that were life threatening.25 Once again, no consensus exists for determining when a deficit should be considered permanent versus transient or when severe or moderate. A small recovery window, observed currently with the ubiquitous 1-month post-op system to establish a neurosurgical M&M overestimates the complications because people have not had sufficient time to recover from their deficits which can frequently be transient in neurosurgery. However, if the recovery window for complication classification is excessively long, the system minimizes that period of time spent with a significant deficit that required longer follow-up than normal. Succinctly capturing the importance of considering the permanency of a deficit, one important point regarding surgical technique and complication was noted that, “transient neurological deficits related to the manipulation of eloquent nervous tissue is unavoidable in certain procedures, and

Rybkin 17 the rate between transient and permanent deficits subsequently defines the excellence of surgery within such a context.” 26 In the case of certain procedures with prolonged expected but nonpermanent deficits, it would not be possible to elucidate what is truly a transient or permanent deficit, and thus accurately classify the complication, based on current neurosurgical M&M classification models. Predictability and Avoidability Houkin et al. classified neurosurgery specific adverse events into 5 types, basing them on relation to the procedure, predictability of the event, and possibility of avoidance.12 In this schema, type I events are unrelated to the index procedure, i.e., it is a completely incidental event that occurs during the perioperative period. A type II event is related to a procedure but unpredictable, even upon deliberate focus retrospective review. Events that are classified as types III to V are predictable procedural-related events. A type III event is predictable yet unavoidable. A type IV event is avoidable, but not due to carelessness. A type V event is due to obvious human error or carelessness. These events were further classified into one of three categories: neurological events (neurological deficits), local events without neurological deficit (ex: wound infection, leakage of CSF), and systemic events (systemic infection and adverse effects of surgery related drugs). Type III events occurred with the greatest frequency in this report (65.4%), suggesting that most adverse events within neurosurgery are predictable yet unavoidable, although often minor and transient. As mentioned earlier, there is no consensus in the literature whether an unavoidable event should be considered a complication. Identifying such events, which would be considered “expected failures” by Bohnen can however differentiate them from “unexpected failures”, which would be more relevant for discussion in neurosurgical M&Ms.

Rybkin 18

Survey/Consensus of Expert Judgement In contrast to arbitrary single-practitioner or single-institutional classification systems, survey responses from large groups of subspecialists have been used to form classification systems. Lebude et al. developed a binary classification system for spine-surgery complications, based on >200 spine surgeons responses to various complication scenarios presented in clinical vignettes.18 The surgeons identified complication incidence and severity based on provided examples illustrating common clinical scenarios. Their responses produced the following complication schema: Major complication: An adverse perioperative event, from surgery to 30 days after surgery, that produces permanent detrimental effect, or necessitates reoperation, even if occurring secondary to medical adverse events not directly related to the procedure. Minor complication: An adverse perioperative event including medical adverse events that produces only transient detrimental effects. It is important to note that there was an overrepresentation of orthopedic surgeons in the respondents (73%). Additionally, the authors found that neurosurgeons were less likely to assign a complication to a clinical scenarios & were more likely to grade them as minor when compared to the orthopedic surgeons. This disparity may be attributable to the more acute life-threatening conditions that neurosurgeons encounter on a daily basis. The unavoidability of negative outcomes commonly seen in a neurosurgical may raise the threshold for what qualifies as a complication. Nevertheless, polling from a survey may determine an opinion consensus, but may not necessarily establish the best method for determining a comprehensive grading system. The differences in opinion regarding complication classification demonstrates the need for standardizing outcome assessment based on individual case factors that have significant

Rybkin 19 influence on patient outcomes, such as patient frailty/baseline characteristics and surgical technical complexity required by a given pathology.

Underlying cause of the adverse event Houkin et al. classifies the causes of adverse events, proposing six classes responsible for a given morbidity: patient disease, technical cause, medical cause concerned with treatment (adverse events of a drug as an example), equipment cause, diagnosis and strategy cause, and unidentified cause. Shortly afterwards another paper attempted to organize complications according to the type of error made, but acknowledged that this did not work in a retrospective fashion because it is too arbitrary.25 In 2016, Ravindra et al. proposed an endovascular neurosurgery-specific complication system based on the underlying cause of complication.20 The subcategories included mechanical complications, technical complications, judgment errors, and critical events. Mechanical complications are related endovascular equipment failure, technical complications result from manual errors, & judgment errors arise from faulty surgical decision making. Errors in judgment can include improper patient selection, inaccurately assessing the risk-benefit ratio of a disease and/or a procedure, poor treatment decisions, or equipment selection. Critical events cause negative outcomes, but do not affect the procedure’s ultimate goal. Reactions to contrast and radiation effects are examples of these events. Most recently, Gozal et al. expanded Ravindra et al.’s initial system, extending its use for all neurosurgical subspecialties.21 Technical errors, judgment errors, and critical events remained in the classification, and in in lieu of the mechanical complications category, the authors added ‘indication errors’, and 'procedural errors’. Indication errors are defined as adverse

Rybkin 20 events resulting from poor preoperative decision making and procedural errors are defined as resulting from failures of perioperative safety protocols or procedures. One important distinction between the two systems is that in the earlier paper improper patient selection and miscalculation of the surgical risk-benefit ratio is categorized in the ‘judgement error’ class, whereas in the second paper it would be classified under ‘indications error’. In contrast to other classification systems, which focus on negative postoperative outcomes, these systems can classify events into complication categories even when patients do not suffer a negative outcome. The authors provide an example – in two of their cases, aneurysm perforation resulted in hemorrhage, however since an external ventricular drain was in place, and a balloon was available, there was no adverse clinical effect to the patient, despite a technical, mechanical, or judgement error having occurred. Additionally, these systems can elucidate multiple causative errors resulting in the same end-complication, and subsequently provides for an opportunity to establish interventions and protocols to reduce such events that result from multifactorial etiologies.

Patient Baseline Comorbidity Characteristics and Pathology Treatment Difficulty Standardizing complication classification cannot occur without taking into account patients’ baseline characteristics (comorbidities) and the surgical risk necessitated by each pathology’s characteristics, or the Pathology Treatment Difficulty (PTD).27 Two individuals undergoing the same procedure for the same pathology but on opposite ends of the comorbidity spectrum, will tend to have significantly different risk profiles. One reported clinical example demonstrated that the risk profile for routine spinal fusion in two patients could vary from 45%

Rybkin 21 to 2%, just based on the former patient having the two comorbidities of diabetes and moderate obesity and the latter patient not having either comorbidity.27 This vast difference in expected outcomes, based on preoperative patient characteristics, must be factored into a neurosurgical M&M classification schema.

Comorbidity Indices Although traditional comorbidity indices have been adopted and used commonly such as the American Society of Anesthesiologists score (ASA) score and the Charlson Comorbidity Index (CCI), the modified frailty index (mFI) has been shown recently to outperform most other indices for predicting outcomes across the spectrum of surgical specialties.28–31 Frailty has been shown to best predict complications in a number of studies, and with the exception of ASA, has predicted adverse outcomes better in posterior lumbar fusion, while CCI was found to be a better predictor of adverse outcomes in spinal tumor resections.32,33 Although mFI has been an excellent outcome predictor, there is widespread variation and heterogeneity regarding how the mFI scores are grouped and classified.34–36 Therefore, there needs to be standardization of frailty scales with mFI classification in order to assure that there is a common language and schema for comparing the baseline patient health characteristics, so that outcomes can be compared fairly. Alternatively, a neurosurgery-specific new frailty index can also be devised for optimal predictive value for each specific pathology type, such as the mFI specific to metastatic spine tumors and similar to what was done previously for risk stratification in patients with unruptured cerebral aneurysms.37 Finally, the Pathology Treatment Difficulty must be systematically and quantitatively accounted for. For example, the 3% mortality rate for skull base meningioma surgery is

Rybkin 22 accepted, but would be unacceptably high for small convexity meningioma surgical resections.16 An example from spine surgery is that the mortality rates for a multitude of cervical or lumbar surgeries is <1%, but is much higher in those undergoing thoracic spine surgery, which can be as high as 6.4% and 7.4% for vertebroplasty and kyphoplasty respectively.27 The PTD is extremely high in some neurosurgery cases, with morbidity and mortality rates at levels that would never be acceptable for routine non-life or neurological function-preserving surgery such as a small abdominal inguinal hernia repair in a healthy patient. Therefore, proper neurosurgical complication classification schemas have to be able to differentiate between an unexpected complication and an adverse outcome that is frequent and expected due to a high PTD, even if the outcome not what most would consider as favorable (e.g. a deep symptomatic brainstem cavernous malformation would carry an extremely high rate of adverse outcomes, even if no technical surgical error so the permitted range of outcomes before blaming on technical error must be much higher than with a small convexity meningioma).38 Ferroli et al. state that major brain vessel manipulation, surgery in an eloquent area, posterior fossa, brainstem-deep location, and cranial nerve manipulation were all statistically significant predictors of complications including new neurological deficits for a series of patients undergoing cranial surgery.39 These are the types of characteristics that would increase the PTD of a particular pathology and some standardized PTD-type of assessment must be taken into account in order to ensure successful prospective comprehensive classification schemas. A standardized classification system that successfully accounts for PTD and surgical complexity could enable individual and institutional outcome comparisons on a larger level. Brock et al. state that ‘with no assessment of surgery complexity, a hospital where only simple surgical procedures are performed will appear much more reliable as opposed to a center of

Rybkin 23 excellence where many complex surgical procedures such as skull base procedures are conducted, for which an incidence of morbidity and a not negligible mortality is even expected’.16 Broggi et al. proposed an algorithm which involves classifying complications either based on Clavien Dindo’s or Landriel Ibañez’s scale, while integrating the Milan Complexity Scale (MCS), to grade overall surgical complexity.17 Surgical outcomes can also be measured by multiple objective scales, such as the Karnofsky Performance Status (KPS), National Institutes of Health Stroke Scale (NIHSS), the modified Rankin Scale (mRS), and other disease-specific patient reported outcome measurements.40–42 While it is unlikely that one classification system will ever adequately reflect all aspects of the post-surgical complications of neurosurgical procedures, there are feasible projects that can bring standardization to the evaluation of neurosurgical outcomes. An example of one such project is the Society of Thoracic Surgeon’s (STS) Public Reporting Online initiative.43 STS makes data available to the public on outcomes of adult cardiac, congenital heart, and general thoracic procedures at individual hospitals enrolled in the STS database. Expected outcomes for each hospital are calculated based on the average outcomes per procedure, adjusted for the risk associated with that hospital’s specific patient population using the STS mortality risk model. The risk adjustment model therefore takes into account the fact the hospitals that treat more complicated patients will have higher mortality rates. The STS outcomes reporting initiative relies on participation of a large number of medical centers for acquisition of accurate data. While thoracic surgeons have collaborated to make this initiative a reality, no such cohesive effort has been put in place in the field of neurosurgery. Recently, a first attempt at making a national outcomes reporting initiative for

Rybkin 24 neurosurgery was started by NeuroPoint through the Quality Outcomes Database (QOD) project.44 QOD aims to create patient registries to collect prospective data on outcomes in spinal surgery, stereotactic radiosurgery, and cerebrovascular procedures and provide risk adjusted benchmarks for these procedures.45 Physician driven quality improvement measures organized through nation-wide patient registries have been successful for STS and can therefore be replicated in neurosurgical practice. As such, more awareness and participation in such initiatives is imperative for the development of systematic and objective outcomes reporting, improving patient safety, and promoting healthcare efficiency.46 We advocate for a system which defines complications based on Landriel Ibañez et al.’s definition: any deviation from the normal postoperative course, graded based on therapy needed to treat, taking into consideration PTD and patient frailty. While such a prospective scale would be more comprehensive than the current scales in the literature, it would require substantial effort in order to apply to the vast breadth of neurosurgical subspecialities. We hold the sentiments of Clark and Spetzler, who state that an objective system could potentially improve the outcomes of neurosurgical groups with lower performances.38 We do however acknowledge potential problems that these authors mention could arise, including surgeon avoidance of difficult cases.

Conclusion The term “complication” has many interpretations throughout the literature with no unified definition accepted among neurosurgical institutions. A standard definition of what constitutes a complication along with a classification system must be established in order to objectively appraise neurosurgical outcomes and is a requirement of standardizing neurosurgical

Rybkin 25 M&Ms. We advocate for a comprehensive scale that includes a pre-operative grading system based on the PTD to factor baseline surgical complexity as well as a baseline mFI to assess for baseline patient comorbidities. This scale also must differentiate between transient and permanent deficits at the 6-month, and 12-month time points if there is still a deficit whose permanency is in question. Ultimately, complex pathologies with high complication rates should have their own M&M classification system determined by consensus from the experts of that specific pathology unless the system by Broggi et al. can be validated or shown to perform well across pathology types.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for- profit sectors.

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Authors

Type of Procedure Graded

Basis of Scale

Cranial and Spinal

Expectedness

Rampersaud (2006)

Spinal

Therapy Required to Treat

Houkin (2009)

Cranial and Spinal

Predictability and Avoidability

Lebude (2010)

Spinal

Survey/Consensus of Expert Judgement

Landriel Ibañez (2011)

Cranial and Spinal

Therapy Required to Treat

Ravindra (2016)

Endovascular

Underlying Cause of the Adverse Event

Gozal (2019)

Cranial, Spinal, Endovascular

Underlying Cause of the Adverse Event

Bonsanto (2001)

Table 1: Unique neurosurgical complication grading systems in the literature

Grade

Clavien Dindo et al.13,19

Landriel Ibañez et al.4

No postoperative events (ie. no complications)

0 I

Any deviation from the normal postoperative course without the need for pharmaceutical treatment or surgical, endoscopic, and radiological interventions*

Requiring pharmacological treatment with drugs other than such allowed for grade I complications†

Requiring surgical, endoscopic or radiological intervention

Complication requiring invasive treatment such as surgical, endoscopic, or endovascular interventions Complication requiring intervention without general anesthesia Complication requiring intervention with general anesthesia Life-threatening complications requiring management in ICU

Intervention not under general anesthesia

Complication involving single organ failure

Intervention under general anesthesia

Complication involving multiple organ failure

IIa IIb

IIIa IIIb

IV IVa

Life-threatening complication (including CNS complications)‡ requiring IC/ICU management Single organ dysfunction (including dialysis Multiorgan dysfunction

IVb V

Minor: requiring none or minimal treatment, with no or minimal effect (1day) on LOS

Complication requiring drug treatment

Ib

III

Any non-life-threatening deviation from normal postoperative course, not requiring invasive treatment Complication requiring no drug treatment

Ia

II

Rampersaud et al.11

Complication resulting in death

Moderate: requiring treatment, increases LOS by 2-7 days and/or has no long term (≤ 6 months) sequelae

Major: requiring significant treatment, increasing LOS by > 7 days and has long term (> 6 months) sequelae

Death

Adverse events that are directly related to surgery or surgical technique Adverse events that are not directly related to surgery or surgical technique

Death

Death

*Allowed therapeutic regimens are: drugs as antimetics, antipyretics, analgetics, diuretics, electrolytes, and physiotherapy. This grade also includes wound infections opened at the bedside. †Blood transfusions and total parenteral nutrition are also included ‡Brain hemorrhage, ischemic stroke, subarrachnoidal bleeding, but excluding transient ischemic attacks LOS = length of stay, ICU = intensive care unit, IC = intensive care

Table 2: Treatment based grading systems

Houkin Grade12

Related to Procedure

Predictable

Avoidable

X

X

X

X

✓

X

X

X

III

✓

✓

X

X

IV

✓

✓

✓

X

V

✓

✓

✓

✓

I

II

Table 3: Houkin et al. Grading Criteria

Error

Cause

Patient Disease

Houkin et al.12 (General Neurosurgery)

Ravindra et al.20 (Endovascular)

Gozal et al.21 (General Neurosurgery)

Inevitable because of the nature and severity of the disease Procedural missteps with regards to technical aspects of surgery/poor technique

Technical cause/error Medical cause concerned with treatment

Adverse effects of drug

Improper use of equipment Equipment cause

Diagnosis and strategy cause Unidentified cause Mechanical error

Judgement error

Cases with incorrect diagnosis Unidentified causes of adverse events Failure of equipment and devices, regardless if an adverse event occurs Direct result of surgical decision making. Includes patient selection, inaccurately assessing the riskbenefit ratio of a disease and a procedure, poor treatment decisions, or equipment selection*

Indications error

Procedural error

Critical events

Adverse events that occur as a direct result of deliberate surgical decisions made intraoperatively Ex: overaggressive tumor resection or incomplete tumor resection requiring reoperation Poor surgical decision-making in the preoperative period. Includes poor patient selection, unclear indications for surgery, or miscalculation of the surgical riskbenefit ratio* Failure of established perioperative safety procedures and protocols Ex: wrong-site surgery, retained foreign bodies, or poor sterilization of instrument

May not directly affect the goals of the procedure but still involve negative outcomes associated with the intervention Ex: Reaction to contrast

* Improper patient selection and miscalculation of the surgical risk-benefit ratio is classified as Judgment Error in Ravindra et al.’s system, but is classified under Indications Errors in Gozal et al.’s system.

Table 4: Cause-based neurosurgical complication classification systems

Abbreviations AE: Adverse event ASA: American Society of Anesthesiologists CCI: Charlson Comorbidity Index CSF: Cerebrospinal fluid DVT: Deep vein thrombosis EBL: Estimated blood loss HRQL: Health related quality of life IC: Intensive care ICU: Intensive care unit KPS: Karnofsky Performance Status LOS: Length of stay M&M: Morbidity and mortality MCS: Milan complexity scale mFI: Modified frailty index mRS: modified Rankin Scale NIHSS: National Institutes of Health Stroke Scale PE: Pulmonary embolism PTD: Pathology treatment difficulty

Conflict of interests: none This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.