Validity of E-PASS Score for Evaluating Perioperative Minor Complications Associated with Carotid Endarterectomy

Abstract

Carotid endarterectomy (CEA) is conducted to reduce the risk of cerebral infarction; therefore, a low complication rate is highly required. To predict long-term morbidity and mortality, various scoring systems have been considered; nonetheless, a model that can be utilized to estimate nonmajor temporary complications and minor complications is currently lacking. To evaluate the occurrence rate of perioperative complications in various surgical domains, the E-PASS (Estimation of Physiological Ability and Surgical Stress) score is employed. This study was carried out to investigate the utility of the E-PASS score as a predictive factor for the risk of minor complications in patients undergoing CEA. The retrospective analysis was performed for 104 consecutive series of CEA procedures carried out at Otaru Municipal Hospital. The correlation between E-PASS and the rate of minor complications was examined. Sensitivity and specificity were used to construct a receiver operating characteristic curve, and the area under the curve (AUC) was calculated for accuracy. Postoperative minor complications occurred in eight cases (7.7%), including six vagal nerve injuries and two pneumonia cases. Three categorical data-preoperative risk score, surgical stress scores, and comprehensive risk score (CRS)-showed a good relationship with the postoperative minor complication. Among them, CRS presented the highest sensitivity and specificity, as indicated by an AUC of 0.68. The CRS cutoff value was calculated as −0.068, with a 1.7% postoperative minor complication rate for those lower than −0.068 and 14.0% for those higher than −0.068. The E-PASS score was effective for evaluating and predicting postoperative minor complications in patients with CEA procedures.

Introduction

Reportedly, severe carotid artery stenosis is associated with a high risk of major stroke, with an annual occurrence rate of 2-6%,^1,2) and revascularization with carotid endarterectomy (CEA) is highly recommended for its prevention.^3,4) Nonetheless, owing to its high-risk nature, perioperative complication cannot be fully avoided, with incidence rates within the initial 30 days post-surgery reported as follows: 0.9% for death, 1.8% for disabling stroke, 3.7% for non-disabling stroke, 9.3% for wound complications, and 8.6% for cranial nerve injuries.⁵⁾ Thus, the occurrence of these complications must be minimized. Although considerable research has been carried out on evaluating the risk factors, particularly focusing on perioperative and long-term mortality and morbidity including major stroke,^6-12) scant attention has been given to the examination of nonmajor, temporary surgical complications such as wound-related issues, cranial nerve injuries, and internal medical complications such as pneumonia. Because minor complications can also influence impairment in daily life, which results in decreased patient satisfaction,¹³⁾ accurate prediction of these minor complications is also crucial for providing better treatment for CEA. E-PASS (Estimation of Physiological Ability and Surgical Stress) is a surgical risk scoring system that can be calculated using the data from both the preoperative condition and intraoperative variables for patients.¹⁴⁾ It has proven effective in predicting postoperative complications in various fields, which include gastrointestinal surgery,¹⁵⁾ abdominal vascular surgery,¹⁶⁾ and spinal surgery.¹⁷⁾ Nevertheless, its utility in evaluating minor complications in CEA remains unreported. Our report aims to evaluate and examine the effectiveness of the E-PASS score in predicting perioperative minor complications in CEA.

Material and Methods

Patients and treatment

The study protocols were approved by the Institutional Review Board of Otaru General Hospital. The study was conducted based on the principles outlined in the Declaration of Helsinki. Informed consent for this study was waived because anonymous clinical data were utilized in the analysis. All of the patients provided written consent for treatment. A retrospective analysis was conducted on 104 consecutive cases of CEA carried out at Otaru City Hospital between January 2017 and November 2021. The extent of stenosis was calculated using computed tomography angiography or carotid ultrasound as previously described,^18,19) and surgical indications were considered when the degree of stenosis was more than 70% for asymptomatic cases, and more than 50% for symptomatic cases, based on the North American Symptomatic Carotid Endarterectomy Trial and Japanese guideline for stroke treatment.²⁰⁾

Surgical techniques

The procedures were consistently carried out by the same four surgeons, employing standardized surgical techniques as previously reported.^21-23) Briefly, the common carotid artery and the bifurcation of internal and external arteries were exposed. Heparin (2000-3000 U) was administered before arterial clamping to achieve an activated coagulation time longer than 200 s. Arteriotomy was subsequently conducted, followed by an insertion of an internal shunt tube. Under an operative microscope, the atherosclerotic plaque was carefully removed. After confirming the total removal of the plaque, stay sutures were placed at the distal end of the intima to avoid the flipping of the intimal layer. The arteriotomy was sutured primarily with a 6-0 nylon. Intravenous indocyanine green fluorescence imaging was then carried out to detect bloodstream and vessel patency.

Assessment of perioperative minor complications

Perioperative minor complications were defined as any neurological or physiological event considered to be moderate for Common Terminology Criteria for Adverse Events (CTCAE version 5.0-JCOG), not present prior to the initiation of surgical procedure, but subsequently recovered during the follow-up period. Thus, the complications comprised wound-related issues, cranial nerve injuries, and postoperative pneumonia. The E-PASS system comprises a comprehensive risk score (CRS) determined using two distinct parameters, preoperative risk score (PRS) and surgical stress score (SSS). The formula of the calculation is listed in Table 1.¹⁴⁾ Physiological and surgical parameters were obtained based on information contained in medical records, anesthesia records, and perioperative nursing check notes. Patients with severe heart or respiratory diseases, generally considered a high-risk group for CEA, were carefully evaluated for both CEA and carotid artery stenting (CAS). Subsequently, those also deemed at higher risk for CAS due to difficulties with catheter guidance or allergies to contrast agents were selected for CEA.

Table 1.

Equations for E-PASS scores: Preoperative risk score (PRS), surgical stress score (SSS), and comprehensive risk score (CRS)

1. PRS = −0.0686 + 0.00345X1 + 0.323X2 + 0.205X3 + 0.153X4 + 0.148X5 + 0.0666X6

X1: Age; X2: Presence (1) or absence (0) of severe heart disease; X3: Presence (1) or absence (0) of severe pulmonary disease; X4: Presence (1) or absence (0) of diabetes mellitus; X5: Performance status index (0-4); X6: American Society of Anesthesiologists Physiological Status Classification (1-5)

Severe heart disease is defined as heart failure of New York Heart Association Class III or IV or severe arrhythmia requiring mechanical support. Severe pulmonary disease is defined as any condition with a % VC less than 60% and/or a FEV1.0% less than 50%. Diabetes mellitus is defined based on the WHO criteria. Performance status index is defined by the Japanese Society for Cancer Therapy.

2. SSS = −0.342 + 0.0139X1 + 0.0392X2 + 0.352X3

X1: blood loss/body weight (g/kg); X2: operation time (h); X3: extent of skin incision (0, minor incision for laparoscopic or thoracoscopic surgery including scope-assisted surgery; 1, laparotomy or thoracotomy alone; 2, both laparotomy and thoracotomy)

3. CRS = −0.328 + 0.936 (PRS) + 0.976 (SSS)

Statistical analysis

All values were expressed as mean ± standard deviation. PRS was further categorized as <0.3, 0.3 to <0.5, 0.5 to <0.7, and 0.7≤; SSS was categorized as <−0.27, −0.27 to <−0.25, −0.25 to <−0.2, and −0.2≤; and CRS was categorized as <−0.25, −0.25 to <−0.1, −0.1 to <0, and 0≤ to evaluate the relationship between the score and the incidence of minor complications as previously reported.¹⁴⁾ Subsequently, the incidence rates of complications were calculated for each category. The optimum cutoff value, delineated by the receiver operating characteristic (ROC) curve, was determined by the maximized sum of sensitivity and specificity. The area under the curve (AUC) was calculated, and the Youden Index was used to calculate the cutoff value. Statistical examinations were conducted by JMP Pro 16 (SAS Institute Inc., NC, USA).

Results

All physiological and surgical parameters were successfully obtained from the patients. Background data and surgical parameters of 104 patients are listed in Table 2. There were 88 were male, and 16 were female, with a mean age of 74 years.

Table 2.

Patient characteristics

Variables	Total	Symptomatic	Asymptomatic
No. of patients	104	41	63
morbidity	9	4	5
M/F ratio	88:16	35:6	53:10
Age in years (±SD)	74.7 ± 7.7	75.7 ± 8.9	63.8 ± 4.2
Smoke (%)	63.5%	73.1%	57.1%
Hypertension (%)	64.4%	56.1%	69.8%
Diabetes mellitus (%)	33.7%	26.8%	38.1%
Severe heart disease (%)	7.7%	12.2%	4.8%
Severe pulmonary disease (%)	3.8%	2.4%	4.8%
Blood loss per body (g/kg)	0.04	0.038	0.041
Performance status	0.76	1.4	0.32
Surgical time (h)	2.5	2.6	2.4
Body mass index	20.8	20.9	20.7

CRS perioperative minor complications occurred in eight cases (7.7%), which were vagal nerve injury (six cases) and pneumonia (two cases) (Table 3). All symptoms of vagus nerve injury were due to swallowing difficulties, which were suspected to be caused by damage to the internal branch of the laryngeal nerve. The relationship between postoperative minor complications and the E-PASS score shows that although there was a single case that showed postoperative complication, the other seven cases presented a linear correlation of PRS and SSS for the incident of postoperative minor complications (Fig. 1A, B). CRS calculated from PRS and SSS also correlated highly with postoperative minor complication (Fig. 1C), which CRS more than −0.1 is at a high risk of postoperative minor complication. We further evaluated the accuracy of each score by examining ROC curves for PRS, SSS, and CRS, in which the AUC were 0.663, 0.623, and 0.684, respectively. These data demonstrate that CRS showed the highest sensitivity for evaluating postoperative complications, and the most appropriate cutoff point calculated by Youden Index was −0.068 for CRS. The patients with a CRS score of less than −0.068 showed that the rate of minor complication was 1.9% (one out of 54 patients), whereas the patients with a CRS score of more than −0.069 exhibited a higher complication rate of 14% (seven out of 50 patients). The factors associated with the occurrence of complications were further evaluated, and performance index (p = 0.035), and blood loss/body weight (p < 0.0001) were strongly correlated with the result, and operation time also showed a trend in the occurrence of the complication (p = 0.083) (Table 4).

Table 3.

Perioperative minor complications

Complications	Total	Symptomatic stenosis	Asymptomatic stenosis
Vagal nerve injury	6	2	4
Pneumonia	2	1	1
Total	8	3	5

Fig. 1.

Relationship between postoperative minor complication and E-PASS scores. A: Preoperative risk score (PRS). B: Surgical stress score (SSS). C: Comprehensive risk score (CRS).

Table 4.

Factors associated with occurrence of complication

	Complication (+)	Complication (−)	p value
PRS	0.77 ± 0.09	0.57 ± 0.03	0.044*
X1: Age	77 ± 2.7	74.5 ± 0.8	0.33
X2: Presence (1) or absence (0) of severe heart disease	0.13 ± 0.1	0.07 ± 0.03	0.6
X3: Presence (1) or absence (0) of severe pulmonary disease	0.13 ± 0.07	0.03 ± 0.02	0.189
X4: Presence (1) or absence (0) of diabetes mellitus	0.38 ± 0.17	0.33 ± 0.05	0.813
X5: Performance status index (0-4)	1.63 ± 0.42	0.688 ± 0.12	0.035*
X6: American Society of Anesthesiologists Physiological Status	3.13 ± 0.37	2.97 ± 0.11	0.686
SSS	−0.22 ± 0.01	−0.24 ± 0	0.0668
X1: Blood loss/body weight (g/kg)	0.13 ± 0.02	0.03 ± 0.01	<0.0001**
X2: Operation time (h)	3.01 ± 0.29	2.48 ± 0.08	0.083
CRS	0.18±0.09	−0.03 ± 0.03	0.027*

Discussion

In our current investigation, we found that a high E-PASS score was correlated with postoperative minor complications. This highlights the validity of the method to predict postoperative minor complications, as well as to guide surgeons in correcting surgical procedures to lower their occurrence.

In this study, we determined that the AUC for CRS was 0.684, considered fairly high for its accuracy. This result aligns with previously reported findings, in which Hirose et al. examined the efficacy of the E-PASS score in spinal cord surgery, which AUC for detecting postoperative complications was 0.668.¹⁷⁾ They reported that complications occurred in 10.6%, predominantly characterized by neurological disorders (20%), indicating the effectiveness of the E-PASS score in predicting postoperative neurological complications, similar to the findings of this investigation. In contrast, the ROC curve for complication detection in elective infra-renal abdominal aortic aneurysm (AAA) repair surgery exhibited a remarkably high value of 0.905.¹⁶⁾ The nature of complications encompassed infections, hemorrhage, intestinal occlusion, perforation, and renal dysfunction. The E-PASS score incorporated parameters including diabetes and severe cardiac conditions, which suggests its potential for a more direct prediction of complications in AAA surgery. The comparably high incidence of complications (59%) may also be considered a contributing factor in AAA surgery. Compared with the high value of the E-PASS score in AAA surgery, there may be room to consider a score more specifically tailored to CEA. Moreover, we found that the group with the lowest values of PRS, SSS, and CRS showed a fairly high complication rate. Although there was one case of complication in this group; however, a small sample size attributed to this phenomenon can be considered a limitation of this method.

In this study, laryngeal nerve paralysis, which is specific to anterior neck surgery, appears to be the most common complication. Tobacco smoke is known to inhibit the swallowing reflex, and some reports are associated with diabetes with oropharyngeal dysphagia.²⁴⁾ These factors potentially contribute to a decrease in physiological function scores, which enables the prediction of complications' prognosis.²⁵⁾ Moreover, the occurrence of laryngeal nerve paralysis is known to be due to surgical procedures. Both blood loss and operation time, which are included in the SSS, are factors that are related to the difficulty of the case and the surgical technique itself and may have influenced postoperative complications. In all cases, the extent of skin incision was comparable, which indicates a correlation between surgical duration, blood loss, and incidence of complications. Longer surgical exposure under the microscope can directly damage the surrounding tissues and subsequently affect laryngeal nerve damage. Blood loss can be interpreted as blood in the surgical field that can cause low visibility of tissues. This can also lead to unawareness of nerve damage. Moreover, mechanical manipulation during surgery may be a potential factor that leads to recurrent laryngeal nerve paralysis, emphasizing the importance of optimizing surgical techniques and maintaining effective bleeding control to achieve favorable postoperative outcomes. Two cases of pneumonia were also seen in our cohort. Although no statistical difference was found between the patient with complication and noncomplication (p = 0.189), in terms of the presence of preoperative severe pulmonary diseases, one of the patients showed that postoperative pneumonia had preoperative severe pulmonary diseases, which may contribute to the occurrence of the disease.

Nonetheless, limitations should be acknowledged. This study was conducted retrospectively in a single institute. To fully prove the validity, a prospective view to validate the method is also required. Although surgical techniques remained largely consistent among surgeons, the effectiveness of the E-PASS score in predicting complication outcomes between the different surgeons must be evaluated.

The E-PASS score proved efficacious in predicting post-CEA minor complications, and acknowledging these parameters can guide surgeons to correct surgical procedures, which can lead to better surgical outcomes. In these factors, to lower the complication, operation time is one of the factors that should be given more attention. To provide a more accurate evaluation scoring system to lower the incidence of minor complication of CEA, further evaluation is necessary.

Conflicts of Interest Disclosure

The authors have no conflicts of interest to disclose.