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Adult Circulatory Support

Examining Noncardiac Surgical Procedures in Patients on Extracorporeal Membrane Oxygenation

Taghavi, Sharven*; Jayarajan, Senthil N.*; Mangi, Abeel A.; Hollenbach, Kathryn; Dauer, Elizabeth*; Sjoholm, Lars O.*; Pathak, Abhijit*; Santora, Thomas A.*; Goldberg, Amy J.*; Rappold, Joseph F.*

Author Information
doi: 10.1097/MAT.0000000000000258
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Abstract

Extracorporeal membrane oxygenation (ECMO) is an established but resource intensive intervention for patients with fulminant cardiac and/or pulmonary failure.1–4 It can be used for temporary support of critically ill patients.2,5–7 Although outcomes in patients supported by ECMO are poor,8–10 they have improved in recent years.11,12 As more and more patients are supported with these temporary devices,13 many will go on to develop noncardiac surgical problems. Few studies to date have examined noncardiac surgical procedures (NCSPs) in patients supported with temporary ECMO, and little data are available to guide perioperative management of these patients. The goal of this study was to determine which types of NCSPs are required in patients supported with ECMO and to identify variables that influence outcomes in this group of patients.

Methods

Data Source and Study Population

The National Inpatient Sample (NIS) database was queried from 2007 to 2010. The NIS database consists of data from approximately 8 million hospital stays each year and represents a stratified sample of 20% of nonfederal US hospitals. The NIS database is the largest all-payer inpatient health care database in the United States.14 International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) procedure codes for ECMO (39.65, 39.66) were used to identify all adult patients requiring ECMO support. Patients undergoing noncardiac surgical procedures after the initiation of ECMO were compared with other patients supported with ECMO not requiring any surgical procedures. Types of procedures and diagnostic and comorbidity data were obtained by ICD-9 diagnosis codes as established in the previous studies.15,16

Outcomes Measured

The primary outcome measured was inpatient mortality after NCSP. Secondary outcomes included perioperative complications using ICD-9 codes as established in the previous studies.15,16 Length of stay and total hospital cost were also examined.

Statistical Analysis

Student’s t-test and χ2 test were used to examine continuous and categorical variables where appropriate. Continuous variables are presented as mean ± SD, and categorical variables are reported as percentages of the total number of data points available for that field. Multiple variable logistic regression analysis using clinically relevant variables was carried out to examine the variables associated with mortality. A p value less than 0.05 was considered statistically significant. Data were analyzed using SAS statistical software version 9.2 (SAS Institute, Cary, NC).

Results

Types of Noncardiac Surgical Procedures

A total of 563 patients required ECMO during the study period. Of these, 269 (47.8%) patients required NCSPs after the initiation of ECMO. There were a total of 380 NCSPs performed, with an average of 1.41 procedures per patient. Mean number of days on ECMO support before having a NCSP was 2.71 days.

The types of procedures required are shown in Table 1. The most common type of procedure performed were general surgery procedures (n = 149, 39.2%). As seen in Figure 1A, the most common type of general surgery procedure consisted of abdominal exploration and/or bowel resection (46.3%). Other types of general surgical procedures required included biopsy/excision of lymph nodes (14.1%), tracheostomy (12.8%), wound debridement (11.4%), wound coverage (8.7%), percutaneous endoscopic gastrostomy tube (3.4%), and some other procedures (3.4%).

Table 1
Table 1:
Type of Noncardiac Surgical Procedure
Figure 1
Figure 1:
The types of (A) general surgery, (B) extremity/vascular surgery, and (C) thoracic surgery procedures required in patients supported with extracorporeal membrane oxygenation are shown.

The second most common classification of procedure was extremity or vascular procedures (n = 112, 29.5%) as seen in Table 1. As seen in Figure 1B, among vascular/extremity operations, the most common was control of major vascular hemorrhage. Other types of extremity/vascular procedures performed included major vascular bypass, endovascular intervention, aortic repair, embolectomy, and fasciotomy.

The next most common procedure classification was noncardiac thoracic procedures (n = 89, 23.4%). As seen in Figure 1C, the most common thoracic procedure was exploratory thoracotomy and thoracoscopy. Other noncardiac thoracic procedures included lung/pleural biopsy, lobectomy or excision of lesion, pneumonectomy, chest wall procedures, and thymectomy. As shown in Table 1, other less common types of NCSPs included neurosurgical procedures (n = 11, 2.9%), gynecologic procedures (n = 7, 1.8%), urological procedures (n = 5, 1.3%), orthopedic (n = 4, 1.1%), and oral/maxillofacial surgeries (n = 3, 0.1%).

Several covariates were examined to determine which variables were associated with the need for NCSPs. The only variables found to be associated with the need for NCSPs included respiratory failure as a cause of needing ECMO (hazard ratio: 1.48, 95% confidence interval [CI]: 1.03–2.13, p = 0.03) and Hispanic ethnicity (odds ratio [OR]: 4.39, 95% CI: 2.08–9.25, p = 0.001).

Baseline Patient Characteristics

A comparison of baseline patient characteristics in the NCSP cohort and no procedure cohort are shown in Table 2. There was no significant difference between the two groups with respect to age, gender, or comorbidities. Charlson comorbidity index was not significantly different when comparing the two groups. The nonprocedure cohort was more likely to require ECMO for cardiogenic failure (53.9% vs. 63.9%, p = 0.01), whereas the NCSP group was more likely to require ECMO because of pulmonary failure (39.4% vs. 33.7%, p = 0.01). The nonprocedure group was more likely to have a median income less than the 25th percentile (20.5% vs. 29.7%, p = 0.04) and less likely to have a median income greater than the 76th percentile (27.9% vs. 23.8%, p = 0.04). The NCSP group was less likely to be white (66.2% vs. 72.2%, p = 0.04), less likely to be black (14.3% vs. 15.3%, p = 0.04), and more likely to be Hispanic (12.2% vs. 4.7%, p = 0.04).

Table 2
Table 2:
Baseline Patient Characteristics

Postoperative Complications and Cost

Postoperative complications and length of stay are summarized in Table 3. The NCSP cohort had significantly longer length of stay (23.5 vs. 16.6 days, p = 0.001). The NCSP cohort had greater incidence of wound infections (7.4% vs. 3.7%, p = 0.02) and bleeding complications (27.9% vs. 17.3%, p = 0.01). Incidences of postoperative pneumonia, urinary tract infection, acute renal failure, pulmonary embolus/deep vein thrombosis, or sepsis were not significantly different. Total hospital charges were higher in the NCSP group ($487,975.00 vs. $371,245.00, p = 0.002).

Table 3
Table 3:
Postoperative Outcomes

Mortality

In-hospital mortality was not significantly different in the two groups (54.3% vs. 58.2%, p = 0.54). A summary of the multivariate analysis is shown in Figure 2. Requirement of NCSPs was not associated with mortality (OR: 0.91, 95% CI: 0.68–1.23, p = 0.17). The only variable found to be independently associated with mortality was requirement of blood transfusion (OR: 1.70, 95% CI: 1.06–2.74, p = 0.03). As shown in Figure 2, reason for ECMO, age, gender, elective admission, type of insurance, ethnicity, admission year, Charlson comorbidity index, and patient income were not associated with mortality.

Figure 2
Figure 2:
A summary of the multivariate analysis is shown. ECMO, extracorporeal membrane oxygenation.

Subset analysis was carried out to examine mortality in the various categories of NCSPs. Inpatient mortality was not significantly different when comparing general surgery procedures (57.8%), noncardiac thoracic procedures (51.1%), and vascular procedures (54.2%); p = 0.32. In addition, subset analysis was carried out in the same multivariate analysis shown in Figure 2 examining the types of procedures and their association with mortality. General surgery procedures (OR: 1.35, 95% CI: 0.81–2.23, p = 0.25), vascular surgery procedures (OR: 0.90, 95% CI: 0.56–1.46, p = 0.68), and noncardiac thoracic surgery procedures (OR: 0.61, 95% CI: 0.36–1.04, p = 0.07) were not associated with mortality.

Comment

Because ECMO continues to be used to support critically ill patients with fulminant respiratory and/or cardiac failure, surgeons will be called on to evaluate these patients for NCSP. Currently, there is a paucity of data to help guide treatment in these patients, and previous research has been limited to small, single-institutional series.1,2,4,17 The goal of this study was to use a large, national database to determine which types of NCSPs are required in patients supported with ECMO and to identify variables that influence outcomes in this group of patients.

This study demonstrates that general surgery problems are common among patients on ECMO. The most common procedure required in this study was abdominal explorations and/or bowel resections. These findings demonstrate that general surgeons must have a high index of suspicion for abdominal pathology when evaluating these patients in consultation. Abdominal compartment syndrome in the patient supported with ECMO has been described in both the pediatric and the adult population18,19 and should be monitored in these patients. However, this study is the first to suggest that bowel ischemia can also be a problem as several patients required bowel resection. Computerized tomography (CT) scan can be helpful in diagnosing surgical problems in patients supported with ECMO, and patients with suggestion of abdominal pathology should receive CT scan to help guide treatment.20,21

Vascular procedures are also common in the ECMO population. The requirement of arterial cannulation in venoarterial ECMO is known to cause complications that require surgical intervention.22,23 In the current study, we found that the most common types of vascular procedures required were controlling of major vascular hemorrhage, major vascular bypass, endovascular procedures, and aortic repair. Patients on ECMO, especially those on venoarterial cannulation, should be monitored for signs and symptoms of limp ischemia and hemorrhage at cannulation sites.

Noncardiac thoracic procedures were found to be another common category of procedures required in the ECMO population. The most common thoracic procedures were exploratory thoracotomy or thoracoscopy and pleural/lung biopsy. In the pediatric population, thoracotomy or thoracoscopy with lung biopsy is a common procedure done for diagnostic purposes in patients with respiratory failure requiring ECMO.24–26 Although the specific reason for surgery could not be obtained from the NIS database, it is likely that the majority of noncardiac thoracic procedures in this study are being carried out to obtain a tissue diagnosis. Interestingly, respiratory failure as the cause for requiring ECMO was associated with the need for NCSP. This suggests that patients requiring venous-venous ECMO are more likely to require NCSP than those requiring venous-arterial ECMO. Further studies are needed to examine this finding. The only other variable found to be associated with the need for NCSP was Hispanic ethnicity. Although previous studies have not documented this finding in patients supported with ECMO, previous research has shown that there can be substantial variation in surgical treatment across various ethnic groups.27

Although mortality was high for patients supported with ECMO requiring NCSP, it was not significantly different compared with patients supported with ECMO not requiring surgical procedures. In addition, on multivariate analysis, we found that requirement of NCSP was not independently associated with mortality. This held true in our subset analysis when looking at the mortality in the three most common categories of NCS. These findings show that requirement for NCSP in patients supported with ECMO does not necessarily add prohibitive risk and that aggressive surgical intervention should be considered in patients who demonstrate an indication for operation.

Few guidelines exist regarding the perioperative management of adult patients on ECMO undergoing NCSPs. Previous studies have shown the importance of maintaining euvolemia, good tissue oxygenation, and normothermia perioperatively.28 In the current study, the requirement of blood transfusion was independently associated with mortality. This is consistent with our previous study, which demonstrated the importance of careful surgical hemostasis and limiting blood products in patients supported with ECMO undergoing NCSPs.29 The 2011 Society of Thoracic Surgeons and Society of Cardiovascular Anesthesiologist Blood Conservation Clinical Practice Guidelines also recommend conservation of blood for patients on ECMO because of the negative effects of blood transfusion in these patients.30

In this study, we found that patients supported with ECMO requiring NCSPs were more likely to have bleeding complications than those not requiring procedures. This is not surprising because bleeding complications are a known consequence of ECMO as a high degree of anticoagulation is required to prevent ECMO circuit thrombosis.11,31,32 Unfortunately, no clear guidelines exist for the perioperative management of anticoagulation in patients supported with ECMO undergoing NCSPs. Management of anticoagulation in patients supported with ECMO should be individualized with a goal of minimizing thrombotic complications without clinically significant bleeding.30

Although requirement of NCSPs did not result in increased mortality for patients on ECMO, it did result in increased bleeding complications, wound infections, length of stay, and total hospital cost. This study is the first to demonstrate these findings. Detailed information on the development of wound infections was not available so we could not determine whether these wound infections where surgical site infections from the NCSP. Further studies are needed to examine these findings in greater detail.

This study was not without limitations. The NIS database is an administrative database; therefore, there are several variables that could impact outcomes but were not available for analysis. This includes pre-existing surgical conditions, type of cannulation used, and total days of ECMO support. In addition, we could not obtain detailed information on complexity of surgical procedures that each patient required or the complications that occurred during their hospital stay as these are obtained by ICD-9 and procedure codes. Finally, the database is limited to inpatient outcomes, so we could not examine long-term morbidity and mortality.

In conclusion, NCSPs in patients supported with ECMO is feasible and does not result in increased mortality. However, it does result in increased morbidity, longer hospital stay, and increased cost. In addition, our findings demonstrate the importance of maintaining careful surgical hemostasis and minimizing perioperative blood products in patients supported with ECMO undergoing NCSPs.

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Keywords:

extracorporeal membrane oxygenation; ECMO; surgery; complications

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