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Postoperative Risk of Hepatic Decompensation after Orthopedic Surgery in Patients with Cirrhosis

  • Eric M. Nyberg1,
  • Michael Batech2,
  • T. Craig Cheetham2,
  • Jose R. Pio2,
  • Susan L. Caparosa2,
  • Mary Alice Chocas1 and
  • Anshuman Singh*,1,3
Journal of Clinical and Translational Hepatology   2016;4(2):83-89

doi: 10.14218/JCTH.2015.00049

Received:

Revised:

Accepted:

Published online:

 Author information

Citation: Nyberg EM, Batech M, Cheetham TC, Pio JR, Caparosa SL, Chocas MA, et al. Postoperative Risk of Hepatic Decompensation after Orthopedic Surgery in Patients with Cirrhosis. J Clin Transl Hepatol. 2016;4(2):83-89. doi: 10.14218/JCTH.2015.00049.

Abstract

Background and Aims: Previous studies have shown increased hepatic decompensation in patients with cirrhosis undergoing surgery. However, there are little data available in cirrhotics undergoing orthopedic surgery compared to cirrhotics who did not undergo surgery. The aim of this study was to examine the demographics, comorbid conditions, and clinical factors associated with hepatic decompensation within 90 days in cirrhotics who underwent orthopedic surgery. Methods: This is a retrospective matched cohort study. Inclusion criteria were cirrhosis diagnosis, age > 18 years, ≥ 6 months continuous health plan membership, and a procedure code for orthopedic surgery. Up to five cirrhotic controls without orthopedic surgery were matched on age, gender, and cirrhosis diagnosis date. Data abstraction was performed for demographics, socioeconomics, clinical, and decompensation data. Chart review was performed for validation. Multivariable analysis estimated relative risk of decompensation. Results: Eight hundred fifty-three orthopedic surgery cases in cirrhotics were matched with 4,263 cirrhotic controls. Among the cases and matched controls, the mean age was 60.5 years, and 52.2% were female. Within 90 days after surgery, cases had more decompensation compared to matched controls (12.8% vs 4.9%). Using multivariable analysis, orthopedic surgery, a 0.5 g/dL decrease in serum albumin, and a 1-unit increase in Charlson Comorbidity Index were associated with a significant increase in decompensation within 90 days of surgery. Diabetes, chronic obstructive pulmonary disease, and chronic kidney disease were seen with increased frequency in cases vs. matched controls. Conclusions: Cirrhotics who underwent orthopedic surgery had a significant increase in hepatic decompensation within 90 days of surgery compared to matched controls. An incremental decrease in serum albumin and an incremental increase in the Charlson Comorbidity Index were significantly associated with hepatic decompensation after surgery.

Keywords

Cirrhosis, Orthopedic surgery

Introduction

Chronic liver disease is a leading cause of morbidity and mortality worldwide, and in 2011, cirrhosis was the 11th most common cause of death in the United States.1 As the incidence of chronic liver disease and cirrhosis increases, more patients with cirrhosis are undergoing surgery of all types. Previous studies have demonstrated an elevated risk of perioperative morbidity and mortality in patients with cirrhosis who undergo nonhepatic surgery.2–6 Additional studies have evaluated perioperative risks and complictions in cirrhotics undergoing orthopedic surgery and compared them to noncirrhotic controls.7–14 A recent study by Kim et al. evaluated 609 patients with chronic liver disease who underwent surgery, including 246 patients who had cirrhosis and 363 patients without cirrhosis.15 The cirrhotic group had markedly higher postoperative morbidity and mortality than those without cirrhosis.

Between 1995 and 2011, Deleuron et al. compared 363 cirrhosis patients with 109,159 noncirrhosis patients who had undergone total hip arthroplasty (THA) or total knee arthroplasty (TKA).15 This Danish registry-based historical cohort study showed that cirrhosis patients who underwent THA or TKA for primary osteoarthritis had worse outcomes than reference patients undergoing the same procedures. Notably, cirrhotic patients had a high risk of readmission for infection, renal failure, and liver disease. These results indicated that the increased risk applied to all cirrhosis patients and was not restricted to severe cases. Orozco et al. compared hepatitis C and a nonhepatitis C groups who underwent orthopedic surgery and found that hepatitis C patients without significant fibrosis did not have an increased risk of complications. However, for TKA there was a correlation between greater fibrosis and higher infection rates. Liao et al. evaluated the complication rate after instrumental lumbar surgery between noncirrhotic patients and cirrhotic patients.14 The rate of complications after instrumented lumbar surgery was significantly higher in patients with cirrhosis than in control patients, especially with subjects who had a Child-Turcotte-Pugh (CPT) score of 6 or more. The dominant postoperative complication in this study was deteriorated hepatic encephalopathy, which occurred even in patients with stable liver disease.

The risk of complications in cirrhotic patients after orthopedic surgery requires further evaluation. To date, the focus of research has been to compare individuals with cirrhosis to those without cirrhosis. The authors are not aware of any studies that have specifically evaluated the effect of orthopedic surgery on hepatic decompensation in cirrhotic patients compared to cirrhotic controls not undergoing orthopedic surgery. We feel that a cirrhotic control group is important since cirrhosis in itself is associated with a certain risk of decompensation due to the natural history of the disease. The aim of the present study was, therefore, to evaluate the risk of postoperative hepatic decompensation in patients with cirrhosis after undergoing orthopedic surgery compared to cirrhotic controls who did not undergo orthopedic surgery.

Methods

Study Population

This retrospective matched cohort study was conducted with Kaiser Permanente Southern California (KPSC). KPSC is an integrated health care delivery system comprising 14 hospitals, 214 outpatient clinics, and serving approximately 4 million members. All healthcare encounters were captured by a comprehensive electronic medical record (EMR) and by a thorough claims system. These data include information on patient demographics, socioeconomic status, coded diagnoses and procedures, laboratory test results, and other relevant information. The study was approved by the KPSC Institutional Review Board (IRB), and the IRB waived the requirement for patient informed consent as this was a database study without direct patient contact. The KPSC member population is varied and reflects that of the overall Southern California population.16

Inclusion criteria

Participants were included if they received a diagnosis of cirrhosis by International Statistical Classification of Diseases and Related Health Problems-9 (ICD-9) from 01 January 2003 to 31 December 2013, were ≥ 18 years old, and had ≥ 6 months continuous health plan membership (Fig. 1).

Selection criteria for cases and controls.
Fig. 1.  Selection criteria for cases and controls.

Cases and Controls

Cirrhotic cases and controls had the same inclusion criteria with the exception of cirrhotic cases having undergone orthopedic surgery based on Current Procedural Terminology procedure codes. Up to five cirrhotic controls not undergoing orthopedic surgery were matched to each case based on age, gender, cirrhosis diagnosis date, and surgery date. See Figure 1 for patient disposition.

Data collection

Data on baseline demographics, socioeconomics, comorbid conditions, lab values, Charlson Comorbidity Index (CCI), and Model for End-Stage Liver Disease (MELD) score were collected during the pre-index period, which was defined as 6 months prior to the index surgery date (primary index date). Baseline demographics included age, gender, race/ethnicity, and neighborhood household income. Household income was estimated on the basis of address using neighborhood income from the US Census. The Quan adaption of the CCI was calculated as an estimate of health status.17,18 The cases undergoing surgery were matched with cirrhotic controls who did not undergo surgery using a second index date defined as the date of surgery for the case.

Hepatic decompensation events that occurred 90 days after the surgery index date were accessed. Hepatic decompensation was defined as new onset or worsening of 1) ascites, 2) spontaneous bacterial peritonitis, 3) variceal bleeding, and/or 4) hepatic encephalopathy. Decompensation events were identified electronically using ICD-9 codes.

Validation of data

To validate the electronic algorithm and to verify decompensation events, chart review was performed on a 10% random sample of control subjects and with all surgery subjects included in the analysis. To increase algorithm accuracy for hepatic encephalopathy, codes for common medications used to treat this complication, including rifaximin and lactulose, were included in the electronic algorithm. Additionally, targeted chart review was performed to verify that lactulose and rifaximin were given for hepatic encephalopathy and not another medical reason. Further, in all cases with abdominal imaging, paracentesis, and/or upper endoscopy within 90 days after surgery, targeted chart review was performed to double-check specifically for ascites, spontaneous bacterial peritonitis, or variceal bleeding.

Statistical analyses

Descriptive statistics were presented as means and range for continuous variables and frequency (percentages) for categorical variables. Multivariable conditional robust Poisson regression was used to estimate relative risk of decompensation. SAS Enterprise Guide 4.3 (SAS Institute Inc., Cary, NC, USA) was used for all data analyses.

Results

Patient Characteristics

A total of 853 patients with cirrhosis who underwent orthopedic surgery (cases) were matched with 4,263 cirrhotic controls. Among the cases and matched controls, the mean age was 60 years, and 52% were female (Table 1). The distribution among ethnicities and neighborhood household income is shown in Table 1. The baseline CCI was similar overall between cases and controls, as shown in Table 1. Additionally, baseline comorbid conditions and selected laboratory parameters are shown in Table 2. The cases had less advanced liver disease by the selected laboratory parameters and had higher percentages of the selected comorbid conditions.

Table 1.

Demographic characteristics of patients with cirrhosis who had orthopedic surgery matched with patients with cirrhosis who did not have orthopedic surgery, by age, gender, and date of cirrhosis diagnosis, 2003–2013, n = 5116

Orthopedic Surgery (Cases) n = 853 (16.7%)No Orthopedic Surgery (Controls) n = 4,263 (83.3%)p-value
Age (years, continuous)0.8527
 Mean (Range)60.5 (18.0–91.0)60.4 (18.0–93.0)
Gender0.9896
 Female445 (52.2%)2225 (52.2%)
 Male408 (47.8%)2038 (47.8%)
Race/Ethnicity
 White485 (56.9%)1888 (44.3%)
 Black68 (8.0%)421 (9.9%)
 Hispanic236 (27.7%)1444 (33.9%)
 Asian/Pacific Islander53 (6.2%)296 (6.9%)
 Other11 (1.3%)214 (5.0%)
Neighborhood Household Income (Category)1
 < 45,000 USD199 (23.6%)1185 (28.3%)
 45,000 – 80,000 USD429 (50.9%)2017 (48.1%)
 > 80,000 USD215 (25.5%)990 (23.6%)
Table 2.

Comorbid conditions and laboratory parameters1 of patients with cirrhosis who had orthopedic surgery matched with patients with cirrhosis who did not have orthopedic surgery, by age, gender, and date of cirrhosis diagnosis, 2003–2013, n = 5116

Orthopedic Surgery (Cases)No Orthopedic Surgery (Controls)p-value
Charlson Comorbidity Index (categorical)0.0966
 ≤ 192 (10.8%)540 (12.8%)
 > 1761 (89.2%)3669 (87.2%)
Chronic Heart Failure0.2222
 No666 (78.1%)3364 (79.9%)
 Yes187 (21.9%)845 (20.1%)
Diabetes Mellitus0.0083
 No483 (56.6%)2587 (61.5%)
 Yes370 (43.4%)1622 (38.5%)
COPD0.0013
 No723 (84.8%)3733 (88.7%)
 Yes130 (15.2%)476 (11.3%)
Chronic Kidney Disease0.0082
 No657 (77%)3408 (81%)
 Yes196 (23%)801 (19%)
MELD Score0.0002
 N4811427
 Mean (Range)8.5 (6–31)9.8 (6–44)
INR<0.0001
 N6521666
 Mean (Range)1.2 (0.9–3.2)1.3 (0.9–5.2)
Serum Creatinine (mg/dL) (categorical)0.7464
 ≤ 1.5 mg/dL675 (87.3%)2037 (87.8%)
 > 1.5 mg/dL98 (12.7%)284 (12.2%)
Total Bilirubin (mg/dL) (categorical)0.0249
 ≤ 2.0 mg/dL503 (87.5%)1603 (83.6%)
 > 2.0 mg/dL72 (12.5%)314 (16.4%)
Serum Albumin (g/dL) (categorical)0.0001
 > 3.5 g/dL266 (56.2%)683 (46.0%)
 < 3.5 g/dL207 (43.8%)802 (54.0%)
Platelet Count (1000/µL) (categorical)0.0005
 ≥ 75 × 1000/µL727 (89.2%)1901 (84.2%)
 < 75 × 1000/µL88 (10.8%)357 (15.8%)

Rate of Complications

Within 90 days after surgery, patients with cirrhosis who underwent orthopedic surgery had more decompensation events compared to matched controls (12.8% vs 4.9%) (Fig. 2). Among the cases that had a decompensation event, 55% (60/109) underwent nonelective surgery and 78% (85/109) underwent a procedure associated with a higher volume of blood loss (78% moderate blood loss vs 22% low blood loss) (Table 3).

Decompensation within 90 days after surgery among patients with cirrhosis who had orthopedic surgery matched with patients with cirrhosis who did not have orthopedic surgery, by age, gender, and date of cirrhosis diagnosis, 2003–2013.
Fig. 2.  Decompensation within 90 days after surgery among patients with cirrhosis who had orthopedic surgery matched with patients with cirrhosis who did not have orthopedic surgery, by age, gender, and date of cirrhosis diagnosis, 2003–2013.
Table 3.

Association of surgical urgency and procedural blood loss with decompensation in 90 days (n = 863)

No decompensation in 90 days, n = 744 (87.2%)Decompensation in 90 days, n = 109 (12.8%)
Elective procedure status
 Non-elective230 (30.9%)60 (55.0%)
 Elective514 (69.1%)49 (45.0%)
Procedure blood loss
 Low loss349 (46.9%)24 (22.0%)
 Moderate loss395 (53.1%)85 (78.0%)

Using robust Poisson regression with a decompensation event as a binary outcome, the crude and multivariable adjusted relative risk estimates for decompensation events within 90 days after surgery were compared to that in a matched cohort (Table 4). Multivariable analysis showed a significant (2-fold) increase in the relative risk of developing a decompensation event within 90 days after surgery compared to matched cirrhotic controls. Multivariable analysis showed that the relative risk of decompensation was significantly increased for each 0.5 g/dL decrease in serum albumin (from 4.0 g/dL) and for each one point increase in the CCI.

Table 4.

Crude and multivariable adjusted relative risk estimates for decompensation within 90 days of surgery (using robust Poisson regression with decompensation event as a binary outcome)

CrudeMultivariable adjusted
Orthopedic surgery
 No surgeryReferenceReference
 Had a surgery2.57 (2.05, 3.21)2.05 (1.60, 2.62)
Age (5-year increase)
1.08 (1.03, 1.13)0.98 (0.93, 1.04)
Gender
 FemaleReferenceReference
 Male1.30 (1.02, 1.65)1.02 (0.78, 1.32)
Race/Ethnicity
 WhiteReferenceReference
 Black0.98 (0.67, 1.44)0.76 (0.46, 1.24)
 Hispanic0.96 (0.75, 1.23)1.01 (0.76, 1.34)
 Asian/Pacific Islander1.07 (0.72, 1.61)1.23 (0.82, 1.85)
Neighborhood household income
 < 45,000 USD1.07 (0.82, 1.38)0.92 (0.68, 1.25)
 45,000 – 80,000 USDReferenceReference
 ≥ 80,000 USD1.03 (0.78, 1.36)1.08 (0.80, 1.47)
MELD score (5-unit increase)
1.28 (1.21, 1.35)1.06 (0.99, 1.14)
Serum albumin albumin (0.5-g/dL decrease)
1.59 (1.49, 1.70)1.49 (1.37, 1.62)
Platelet count (25-unit decrease)
1.14 (1.09, 1.19)1.03 (0.99, 1.07)
Charlson Comorbidity Index (1-unit increase)
1.22 (1.17, 1.27)1.11 (1.06, 1.17)

Discussion

In this study of 853 patients with cirrhosis who underwent orthopedic surgery, the adjusted relative risk of decompensation within 90 days after surgery was 2-fold higher than that of 4,263 patients with cirrhosis (controls) matched by age, gender, and date of cirrhosis diagnosis. The rate of decompensation within 90 days after surgery in cases was 12.8% versus 4.9% in controls (Fig. 2). The baseline CCI was similar among cases vs. controls, however, individual laboratory parameters at baseline suggest that the cases were selected for as having a lower severity of liver disease compared to controls. This is implied by a baseline lower platelet count in cirrhotic controls than in cases. Lower platelet count is a commonly used surrogate marker for degree of portal hypertension in cirrhotics. Additionally, controls had lower baseline albumin compared to cases, while bilirubin was slightly higher among cases compared to controls. Despite this apparent selection for healthier patients, cases had a 2-fold increased rate of decompensation within 90 days after surgery. These findings support the suggestion of Rai et al. that the risk versus benefit of the procedure should be carefully assessed and discussed in patients with concurrent liver disease who are undergoing a surgical procedure.19

Determining surgical risk in cirrhotic patients is difficult, and multiple scoring systems have sought to quantify this risk. Kim et al. showed that the type of surgery, CPT score, and MELD score were independently associated with postoperative morbidity and mortality in patients with cirrhosis.20 The present study shows that the MELD score and platelet count trend toward statistical significance as a predictor of the risk of decompensation within 90 days of orthopedic surgery. Due to the retrospective design of the present study, one or more parameters included in the MELD score were frequently missing, therefore, a trend toward significance is notable. Further, multivariable analysis showed that the relative risk of decompensation increased significantly with a corresponding incremental change in serum albumin and CCI (Table 4).

Causey et al. performed a single-center retrospective review of 64 cirrhotic patients who underwent nontransplant surgery under general anesthesia over a 6-year period of time to analyze outcomes on postoperative morbidity and mortality using CTP, MELD, and MELD-sodium (MELD-Na) scores.21 Kim et al. utilized CTP and MELD-based indices to compare the abilities of liver indices to predict mortality for patients with liver cirrhosis who underwent elective surgery.20 The authors concluded that a large-scale study is needed to validate how well liver indices that assess the severity of hepatic decompensation predict perioperative adverse events.20 The present study strengthens the indication that these scoring systems are good predictors of perioperative risk. Further, this applies in cirrhotics undergoing orthopedic surgery compared to cirrhotics not undergoing orthopedic surgery, suggesting that events in the perioperative period precipitate hepatic decompensation at a significantly higher rate than that occurring due to the natural history of cirrhosis alone.

As the population in general is becoming more obese, it is expected that an increasing number of patients with obesity-related cirrhosis will undergo elective surgery. A study by Tiberi et al. compared 115 patients with cirrhosis and matched controls without cirrhosis who underwent THA or TKA from 2000 to 2012.11 The authors concluded that patients with cirrhosis undergoing THA or TKA are at increased risk for medical and surgical complications. Patients with cirrhosis had longer hospital stays, more early post-operative hospital readmissions, and more frequent discharges to a skilled nursing or short-term rehabilitation facility compared with controls. Within 90 days of the procedure, the cirrhotic group had more hip dislocations, infections, and revision surgeries. In addition, the study found a correlation between increasing MELD scores and increased rates of complications; a MELD score of 10 or greater had the highest risk of complications. Using cirrhotics instead of healthy controls, our study demonstrates that exposure to orthopedic surgery is an independent risk factor for decompensation in this population.

Hsieh et al. have demonstrated an association between volume of blood loss and urgency of surgery and postoperative morbidity and mortality.7 Similarly, we showed that a higher percentage of cases with a decompensation event had urgent surgery and underwent a procedure associated with higher blood loss (Table 3).

To our knowledge, this is the first matched cohort study to evaluate the rate of hepatic decompensation in cirrhotic patients undergoing orthopedic surgery compared to cirrhotic patients not undergoing surgery. A strength of this study is that it reflects a “real world” population including a large number of patients matched with up to five controls. The ethnic and socioeconomic distribution of the study population is consistent with that of the general population of Southern California.16 Further, the study was conducted within a large healthcare delivery system with an EMR allowing comprehensive evaluation of the medical care provided to patients, minimal ingress and egress, and thorough manual chart review was performed to validate the electronic algorithm and to confirm decompensation.

We matched cases with controls by age, gender, and cirrhosis diagnosis date; however, a limitation of the study is that we were not able to match cases and controls by markers of severity of liver disease. This was not possible due to incomplete clinical data for matching all criteria within an appropriate time period defined as 180 days. Additionally, we were unable to determine baseline CPT score and ASA score due to the nature of the study. Further limitations include drawbacks that are characteristic of retrospective studies, and those limitations inherent in using an electronic algorithm for data abstraction. These limitations include a risk of not identifying certain factors due to deficiencies in coding although an extensive chart review was performed, as noted above.

Conclusions

In summary, this study demonstrates a significant (2-fold) increase in the risk of hepatic decompensation in patients with cirrhosis within 90 days of undergoing orthopedic surgery compared to cirrhotics not undergoing orthopedic surgery. This finding reinforces the need for perioperative optimization of patients with cirrhosis and supports close monitoring of cirrhotic patients in the months following orthopedic surgery.

Abbreviations

CCI: 

Charlson Comorbidity Index

CPT: 

Childs-Pugh-Turcotte

EMR: 

electronic medical record

ICD-9: 

International Statistical Classification of Diseases and Related Health Problems-9

IRB: 

Institutional Review Board

KPSC: 

Kaiser Permanente Southern California

MELD: 

Model for End-Stage Liver Disease

THA: 

total hit arthroplasty

TKA: 

total knee arthroplasty

Declarations

Acknowledgement

This publication was made possible by a Kaiser Permanente Southern California Regional Research Committee grant, which is partially supported by the Southern California Permanente Medical Group Research and Evaluation Department and Direct Community Benefit Investment funds.

Conflict of interest

None

Authors’ contributions

Conception and design, interpretation of data, write-up, and preparation of manuscript (EMN), study design, analysis and interpretation of data, write-up, and critical review of manuscript (MB), conception and design, interpretation of data, write-up, and critical review of manuscript (TCC), data collection, write-up, and critical review of manuscript (JRP), data collection, write-up, and critical review of manuscript (MAC), data collection, write-up, and critical review of manuscript (SLC), conception and design, interpretation of data, write-up, and critical review of manuscript (AS).

References

  1. Heron M. Deaths: leading causes for 2011. Natl Vital Stat Rep 2015;64:1-96 View Article PubMed/NCBI
  2. Pandey CK, Karna ST, Pandey VK, Tandon M, Singhal A, Mangla V. Perioperative risk factors in patients with liver disease undergoing non-hepatic surgery. World J Gastrointest Surg 2012;4:267-274 View Article PubMed/NCBI
  3. Muir AJ. Surgical clearance for the patient with chronic liver disease. Clin Liver Dis 2012;16:421-433 View Article PubMed/NCBI
  4. Nicoll A. Surgical risk in patients with cirrhosis. J Gastroenterol Hepatol 2012;27:1569-1575 View Article PubMed/NCBI
  5. Friedman LS. Surgery in the patient with liver disease. Trans Am Clin Climatol Assoc 2010;121:192-204 View Article PubMed/NCBI
  6. Csikesz NG, Nguyen LN, Tseng JF, Shah SA. Nationwide volume and mortality after elective surgery in cirrhotic patients. J Am Coll Surg 2009;208:96-103 View Article PubMed/NCBI
  7. Hsieh PH, Chen LH, Lee MS, Chen CH, Yang WE, Shih CH. Hip arthroplasty in patients with cirrhosis of the liver. J Bone Joint Surg Br 2003;85:818-821 View Article PubMed/NCBI
  8. Shih LY, Cheng CY, Chang CH, Hsu KY, Hsu RW, Shih HN. Total knee arthroplasty in patients with liver cirrhosis. J Bone Joint Surg Am 2004;86-A:335-341 View Article PubMed/NCBI
  9. Cohen SM, Te HS, Levitsky J. Operative risk of total hip and knee arthroplasty in cirrhotic patients. J Arthroplasty 2005;20:460-466 View Article PubMed/NCBI
  10. Moon YW, Kim YS, Kwon SY, Kim SY, Lim SJ, Park YS. Perioperative risk of hip arthroplasty in patients with cirrhotic liver disease. J Korean Med Sci 2007;22:223-226 View Article PubMed/NCBI
  11. Tiberi JV, Hansen V, El-Abbadi N, Bedair H. Increased complication rates after hip and knee arthroplasty in patients with cirrhosis of the liver. Clin Orthop Relat Res 2014;472:2774-2778 View Article PubMed/NCBI
  12. Deleuran T, Vilstrup H, Overgaard S, Jepsen P. Cirrhosis patients have increased risk of complications after hip or knee arthroplasty. Acta Orthop 2015;86:108-113 View Article PubMed/NCBI
  13. Orozco F, Post ZD, Baxi O, Miller A, Ong A. Fibrosis in hepatitis C patients predicts complications after elective total joint arthroplasty. J Arthroplasty 2014;29:7-10 View Article PubMed/NCBI
  14. Liao JC, Chen WJ, Chen LH, Niu CC, Fu TS, Lai PL. Complications associated with instrumented lumbar surgery in patients with liver cirrhosis: a matched cohort analysis. Spine J 2013;13:908-913 View Article PubMed/NCBI
  15. Kim TH, Um SH, Yim SY, Seo YS, Yim HJ, Jeen YT. The risk of perioperative adverse events in patients with chronic liver disease. Liver Int 2015;35:713-723 View Article PubMed/NCBI
  16. Koebnick C, Langer-Gould AM, Gould MK, Chao CR, Iyer RL, Smith N. Sociodemographic characteristics of members of a large, integrated health care system: comparison with US Census Bureau data. Perm J 2012;16:37-41 View Article PubMed/NCBI
  17. Romano PS, Roos LL, Jollis JG. Adapting a clinical comorbidity index for use with ICD-9-CM administrative data: differing perspectives. J Clin Epidemiol 1993;46:1075-1079 View Article PubMed/NCBI
  18. Quan H, Sundararajan V, Halfon P, Fong A, Burnand B, Luthi JC. Coding algorithms for defining comorbidities in ICD-9-CM and ICD-10 administrative data. Med Care 2005;43:1130-1139 View Article PubMed/NCBI
  19. Rai R, Nagral S, Nagral A. Surgery in a patient with liver disease. J Clin Exp Hepatol 2012;2:238-246 View Article PubMed/NCBI
  20. Kim DH, Kim SH, Kim KS, Lee WJ, Kim NK, Noh SH. Predictors of mortality in cirrhotic patients undergoing extrahepatic surgery: comparison of Child-Turcotte-Pugh and model for end-stage liver disease-based indices. ANZ J Surg 2014;84:832-836 View Article PubMed/NCBI
  21. Causey MW, Steele SR, Farris Z, Lyle DS, Beitler AL. An assessment of different scoring systems in cirrhotic patients undergoing nontransplant surgery. Am J Surg 2012;203:589-593 View Article PubMed/NCBI