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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 4  |  Issue : 4  |  Page : 213-225

Risk factors in adult patients with chronic hepatitis C virus undergoing cardiac surgery with cardiopulmonary bypass: a prospective study


Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, University of Alexandria, Alexandria, Egypt

Date of Submission26-Jul-2016
Date of Acceptance26-Feb-2017
Date of Web Publication11-Oct-2017

Correspondence Address:
Ayman F Khalifa
Department of Anaesthesia and Surgical Intensive Care, Faculty of Medicine, Alexandria University, Alexandria
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/roaic.roaic_61_16

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  Abstract 

Background
Variable outcomes of cardiac operations have been reported in patients with liver disease, but no definitive predictive prognostic factors have been established. This prospective study assessed operative results to identify risk factors associated with morbidity after cardiovascular operations in patients with chronic viral hepatitis.
Patients and methods
The study group consisted of 90 patients with documented chronic viral hepatitis who were subject to elective cardiac surgery with cardiopulmonary bypass (CPB). Potential preoperative predictors of outcome, as well as preoperative model for end-stage liver disease (MELD) score and European system for cardiac operative risk evaluation (EuroSCORE), were calculated. The primary study end points were hospital morbidity (according to sequential organ failure assessment score and other additional morbidities not captured by sequential organ failure assessment score) or mortality (as defined by EuroSCORE II).
Results
The average EuroSCORE II was 1.12±0.56. The average MELD score was 10.12±2.7, which corresponds to a mild to moderate liver dysfunction. Despite the low EuroSCORE II values, 39 patients developed postoperative significant morbidity including seven patients who died in hospital. There were four patients with gastrointestinal complications (two cases with prolonged ileus and two cases with gastrointestinal bleeding bleeding); eight cases with occurrence of infection (six cases with sternal wound infection and two cases with sepsis); five reopen cases; and five cases that needed intra-aortic balloon pump. Analysis showed significant differences in age, MELD score, preoperative platelet count, preoperative creatinine, and preoperative total bilirubin when patients with postoperative morbidity and mortality (group M) were compared with patients without significant morbidity (group N). CPB time, cross-clamp time, postoperative mechanical ventilation, and duration of ICU stay were significantly higher in the group M. In addition, blood products transfused and total chest tubes drainage were significantly higher in the group M. Central venous pressure was significantly higher in the group M after weaning of CPB and thereafter. Arrhythmias were seen postoperatively in 16.6% of cases, the most common being atrial fibrillation, and was significantly higher in the group M. Receiver operating characteristic curve analysis showed that age of 58 years and MELD score of 12 were cutoff values for hospital morbidity, whereas the optimal cutoff values for preoperative platelet count, creatinine, and total bilirubin were 146×103/μl, 1.27 mg/dl, and 1.21 mg/dl, respectively.
Conclusion
Careful consideration of operative indications and methods are necessary in chronic viral hepatitis patients with old age, high MELD scores, low platelet counts, and high serum creatinine and bilirubin. It is vital that liver dysfunction is added to the risk models, which are currently used to predict the postoperative morbidity of cardiac surgery patients.

Keywords: cardiac surgery, cardiopulmonary bypass, chronic hepatitis c virus, risk factors


How to cite this article:
Sabry AM, Fouad HA, Hashem A, Khalifa AF. Risk factors in adult patients with chronic hepatitis C virus undergoing cardiac surgery with cardiopulmonary bypass: a prospective study. Res Opin Anesth Intensive Care 2017;4:213-25

How to cite this URL:
Sabry AM, Fouad HA, Hashem A, Khalifa AF. Risk factors in adult patients with chronic hepatitis C virus undergoing cardiac surgery with cardiopulmonary bypass: a prospective study. Res Opin Anesth Intensive Care [serial online] 2017 [cited 2020 Jun 4];4:213-25. Available from: http://www.roaic.eg.net/text.asp?2017/4/4/213/216452


  Introduction Top


Nearly 3% of the world’s population, some 180 million people, is estimated to be infected with the hepatitis C virus (HCV). Chronic HCV infection has almost doubled in the past decade [1]. With the increasing prevalence of liver disease and improved survival due to newer medications and treatments, a growing number of patients with liver disease require preoperative assessment. These patients are at an increased risk of perioperative mortality because of the effects of surgery and anesthesia on the liver and alternations in the unique metabolic and synthetic functions of the liver [2].

In patients undergoing cardiovascular operations, advanced liver dysfunction increases the risk of complications, including infections and impairment of various organs such as the heart, kidney, and lungs, thereby increasing the burden of postoperative management [3].

Reduction in the total hepatic blood flow during surgery does not necessarily result in hepatic ischemia. In fact, compensatory mechanisms, such as simultaneous reduction in oxygen demand and/or relative increase in oxygen extraction by the liver, usually prevent hepatocellular necrosis in the vast majority of patients undergoing anesthesia and surgery [4],[5],[6].

Cardiopulmonary bypass (CPB), with the associated imbalance between oxygen demand and oxygen supply in the hepatosplanchnic region and the resultant intestinal mucosal injury, leads to a state of endotoxemia due to the release of proinflammatory cytokines [6],[7]. Low hepatic venous oxygen saturation (ShvO2), or increased hepatosplanchnic oxygen extraction, has been reported during and after CPB [8],[9].

However, hepatic dysfunction, manifested by an increase in serum transaminases and bilirubin, does not often occur following bypass, as the hepatocytes are usually protected against a short period of hypoxia [10]. Nevertheless, patients with pre-existing liver disease undergoing CPB are at risk of postoperative liver dysfunction with frequent mortality [11].

It is difficult to completely evaluate hepatic function with a single test because the liver has many functions. Accordingly, to estimate hepatic functional reserve, it is necessary to evaluate the overall results of various liver function tests. The results of these different tests do not all indicate the same degree of dysfunction among all patients. Of these tests, the levels of serum cholinesterase (ChE), which is a hepatocyte secretion enzyme, might indicate hepatic functional reserve [11],[12].

Current cardiac risk scores such as European system for cardiac operative risk evaluation (EuroSCORE II) and the Society of Thoracic Surgeons score do not take liver dysfunction into account despite the importance of liver function with respect to postoperative complications [13].

Although the model for end-stage liver disease (MELD) was initially derived in a small number of patients undergoing transjugular intrahepatic portosystemic shunt procedures to predict survival [14], to date MELD score has become a standard tool for allocation of organs for liver transplantation [15], as well as for risk prediction in several cohorts of patients with varying severity of liver disease [16],[17]. Whether the MELD score, the Child–Turcotte–Pugh (CTP) classification, or possibly the EuroSCORE are helpful tools to predict the risk of morbidity and mortality after cardiac surgery in these cirrhotic patients has not yet been evaluated in a larger cohort [18].

The majority of studies examining the risk of surgery in patients with liver disease have focused on patients with cirrhosis from which a number of risk factors have been identified. Much less information has been published on the risk of surgery in patients with milder forms of liver disease [19],[20],[21].


  Objective Top


The objective of this study was to prospectively evaluate the effect of some perioperative variables on postoperative morbidity and mortality in chronic HCV patients undergoing cardiac surgery with CPB, identify risk factors, and assess their predictive values.


  Patients and methods Top


This study was carried out on 90 adult patients of both sexes with documented chronic HCV infection admitted to the Cardiothoracic Department of the Alexandria Main University Hospital, scheduled for elective cardiac surgery with CPB.

Patients with liver diseases other than viral hepatitis C, hepatocellular carcinoma, acute fulminant hepatitis, MELD score greater than 20, surgery on thoracic aorta, combined procedures, reoperations, bleeding diathesis, and extremes of age (<18 or >75 years) were excluded from the study. After approval of the local Medical Ethics Committee of the Faculty of Medicine (Number 020655 held on 2 August 2014) and taking a written informed consent, formal preanesthetic assessment of every patient as regards demographic data (age, sex, and weight), detailed medical history, complete physical examination, laboratory investigations [including fasting blood sugar, complete blood count, renal functions, liver enzymes, alkaline phosphatase (AP), serum lactate dehydrogenase (LDH), coagulation profile, lipid profile, total serum bilirubin, serum albumin, and serum ChE], and cardiovascular, chest, and liver assessment (ECG, echocardiographic imaging of the heart and carotids Doppler and cardiac catheterization when needed, plain chest radiography, and abdominal ultrasound imaging). Risk assessment was done by calculation of EuroSCORE II and MELD score. All preoperative medications were continued until the morning of surgery.

On arrival to the operating room, peripheral and central venous cannulation and radial artery cannulation were done under local anesthesia and intravenous (IV) sedation in the form of 2 mg of midazolam and 4 mg of morphine sulfate after applying standard monitoring to the patient.

Induction and maintenance of anesthesia was standardized in all patients in the form of midazolam (0.05 mg/kg IV), fentanyl (5 μg/kg IV), propofol (sleeping dose) titrated to maintain hemodynamic stability, and cisatracurium (0.2 mg/kg IV) to facilitate endotracheal intubation. The lungs were ventilated at normocapnia (monitored by end tidal CO2 at 35 mmHg) with isoflurane (1.5%) in an air–oxygen mixture. Additional bolus doses of fentanyl and cisatracurium were injected if necessary. CPB was managed with isovolemic hemodilution, moderate hypothermia (28−30°C) by the heat exchanger to keep the desired temperature, roller pump, and membrane oxygenator. The perfusion flow was kept between 2.4 and 2.6 l/min/m2 during normothermia and between 2 and 2.4 l/min/m2 during hypothermia in every patient. The mean arterial pressure was kept between 50 and 80 mmHg.

Packed red blood cells were transfused according to the Society of Thoracic Surgeons score guidelines [22], and fresh frozen plasma and platelets were infused when necessary (criteria for platelet transfusion was a platelet count of less than 7.0×104/μl or a bleeding tendency after weaning from CPB) [3]. Weaning from CPB and reperfusion of the heart was performed according to the patient’s general condition and cross-clamp time. There was no fixed postoperative treatment regimen for either pharmaceutical or mechanical support. Weaning and extubation from the ventilator was done after hemodynamic [defined as a mean arterial pressure of 60–90 mmHg, heart rate between 60 and 90 bpm, a central venous pressure (CVP) between 10 and 15 mmHg] and ventilatory stability. Analgesia was given in the form of morphine sulfate infusion (2–3 mg/h) in the first 48 h and paracetamol 1 g/6 h.

Measurements included demographic data (age and sex), baseline data (diabetes mellitus, hypertension, hypercholesterolemia, aspartate aminotransferase/alanine aminotransferase ratio, BMI, smoking, and stroke history), and calculation of EuroSCORE II and MELD score; all measurements were recorded preoperatively [16]:



Laboratory investigations [including platelet count, hematocrit (%), blood urea, serum creatinine, aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase, AP, serum LDH, prothrombin activity, international normalized ratio, partial thromboplastin time, total serum bilirubin, serum albumin, and serum ChE] were measured preoperatively, intraoperatively after the termination of CPB, and daily for the first 3 days postoperatively except for serum ChE, which was measured only preoperatively. Insulin resistance was measured according to homeostasis model assessment of insulin resistance HOMA-IR formula preoperatively and after 12 h of the termination of CPB [23]:



Intraoperative mean invasive arterial blood pressure (mmHg), arterial oxygen tension (PaO2), core temperature (°C), and CVP (cmH2O) were recorded after induction of anesthesia, just before CPB, after weaning from CPB, at end of surgery, and postoperatively every 6 h until 24 h.

Clinical measurements including anesthesia time (hours), cross-clamp time (minutes), CPB time (minutes), operative time (hours), type of surgery performed, postoperative mechanical ventilation time (hours), length of ICU stay from operation (days), amount of blood products transfused, chest tubes drainage (ml), and postoperative arrhythmias (and its type) were recorded as well and compared between the two groups.

Statistical analysis [24]

Data were fed to the computer and analyzed using IBM statistical package for the social sciences software package version 20.0 (SPSS; SPSS Inc., Chicago, Illinois, USA). Qualitative data were described using number and percent. Quantitative data were described using range (minimum and maximum), mean, SD, and median. Significance of the obtained results was judged at the 5% level.

The following statistical tests were used:
  1. χ2-Test: it was used for categorical variables, to compare between different groups.
  2. Fisher’s exact or Monte-Carlo correction: it was used to correct for χ2 when more than 20% of the cells have expected count less than 5.
  3. Student’s t-test: it was used for normally quantitative variables, to compare between two studied groups.
  4. Mann–Whitney test: it was used for abnormally quantitative variables, to compare between two studied groups.
  5. Receiver operating characteristic (ROC) curve: it is generated by plotting sensitivity (TP) on y-axis versus 1-specificity (FP) on x-axis at different cutoff values. The area under (AUC) the ROC curve denotes the diagnostic performance of the test. Area more than 50% gives acceptable performance and area about 100% is the best performance for the test. The ROC curve allows also a comparison of performance between two tests.
  6. Multivariate liner regression was assessed.



  Results Top


Postoperatively, patients were categorized into two groups:
  1. Group N included 51 patients, defined as patients without hospital morbidity or mortality − i.e. without significant complications.
  2. Group M included 39 patients, defined as patients with hospital morbidity [according to sequential organ failure assessment (SOFA) score; morbidity is considered if SOFA score is ≥3 points (presence of organ failure) during the ICU stay or the presence of any of the additional morbidities] or mortality (defined by EuroSCORE II; mortality within 30 days from operation or later if the patient is still hospitalized).
  3. Distribution of morbidities in the group M (n=39) is shown in [Table 1]. There were seven deaths in the group M in accordance with EuroSCORE II definition.
    Table 1 Distribution of morbidities in group M (n=39)

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Demographics and baseline data

Preoperative demographic and baseline characteristics of the patients are shown in [Table 2]. Univariate analysis identified significant differences between the groups M and N for age, MELD score, preoperative platelet count, preoperative serum creatinine, and preoperative total serum bilirubin. There were no significant differences between both groups regarding EuroSCORE II, preoperative serum ChE, and preoperative insulin resistance.
Table 2 Preoperative data

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Intraoperative data

There were no significant differences between the groups M and N as regards mean invasive arterial blood pressure, arterial oxygen tension, core temperature, and CVP in all intraoperative intervals, except for CVP that showed significant differences after weaning of CPB and at the end of surgery ([Table 3]).
Table 3 Intraoperative parameters at different intervals

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Intraoperative laboratory data after weaning of CPB are shown in [Table 4]. There were significant differences between both groups regarding platelet count, hematocrit, serum creatinine, γ-glutamyl transferase, AP, and total serum bilirubin.
Table 4 Intraoperative laboratory data after cardiopulmonary bypass

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Postoperative and clinical data

Laboratory data were significantly lower in the group M than in the group N at the first, second, and third days postoperatively ([Table 5]), except for blood urea, serum LDH, partial thromboplastin time, and serum albumin. As regards insulin resistance 12 h after CPB, with a mean value of 2.04±0.83 in the group N and a mean value of 2.56±0.83 in the group M, there was a statistically significant difference between both groups (P=0.004).
Table 5 Postoperative laboratory data

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Postoperative mean invasive arterial blood pressure, arterial oxygen tension, and core temperature showed no significant differences between the groups M and N at all postoperative intervals, whereas CVP was significantly higher in the group M at all postoperative intervals ([Table 6]).
Table 6 Comparison between both groups regarding postoperative parameters

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There were no significant differences in the surgical interventions between the groups M and N, as shown in [Table 7]. There was no significant difference in the mean duration of anesthesia and surgery between groups N and M. However, for CPB time (mean value of 85.76±17.3 min in group N, and 97.87±14.58 min in group M) and aortic cross-clamp time (mean value of 66.12±14.68 min in group N, and 72.03±11.90 min in group M), there was a significant difference between both groups, which was higher in the group M (P=0.001 and 0.043, respectively) ([Table 8]).
Table 7 Comparison between the two groups regarding type of surgery performed

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Table 8 Operative and postoperative clinical data

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The mean duration of mechanical ventilation was 6.08±1.50 h in the group N and 41.76±86.66 h in the group M, and mean ICU stay time was 5.75±1.35 days in the group N and 10.23±3.45 days in the group M. The mean total chest tube output was 801.47±232.67 and 1119.23± 400.88 ml in groups N and M, respectively ([Table 8]). Postoperative arrhythmia occurred in four patients in the group N and 11 patients in the group M; there were significant differences in the mean duration of mechanical ventilation, length of ICU stay, total chest tube drainage, and occurrence of arrhythmia postoperatively between the two groups. Mean transfusion requirements were also significantly higher in group M in comparison with group N, as shown in [Table 9].
Table 9 Comparison between the two groups regarding blood products transfused

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Multivariate analysis of factors related to morbidity after cardiac surgery

Multivariate logistic regression analysis was performed to identify the risk factors for in-hospital morbidity. The variables listed in [Table 10] were included in the analysis. Multivariate analysis identified MELD score [odds ratio (OR): 3.264, 95% confidence interval (CI): 1.233–8.640, P<0.001], cross-clamp time (OR: 0.689, 95% CI: 0.495–0.959, P=0.043), and CPB time (OR: 3.48, 95% CI: 1.051–1.784, P=0.001) as the independent predictors for morbidity.
Table 10 Multivariate logistic regression analysis for some risk factors for morbidity

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Cutoff values

ROC curves were used to evaluate the cutoff values for age, MELD score, platelet count, serum creatinine, and total serum bilirubin as preoperative predictive factors influencing hospital morbidity in patients with chronic viral hepatitis undergoing CPB ([Table 11]).
Table 11 Cutoff values, area under the curve, sensitivity, specificity, and preoperative risk factors

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Analysis yielded cutoff value for age set at 58 years with an AUC of 0.752, a sensitivity of 76.92%, and a specificity of 68.63%. The optimal cutoff value for the MELD score was set at 12 with an AUC of 0.965, a sensitivity of 69.23%, and specificity of 96.08%. For preoperative platelet count the optimal cutoff value was set at 146×103/μl with a sensitivity of 64.1% and specificity of 98.04%. Preoperative creatinine showed cutoff value set at 1.27 mg/dl with a sensitivity of 76.92% and specificity of 82.35%, and for preoperative total bilirubin the cutoff value was set at 1.21 mg/dl with a sensitivity of 48.72% and specificity of 90.2% ([Figure 1],[Figure 2],[Figure 3],[Figure 4],[Figure 5]).
Figure 1 Receiver operating characteristic curve for age.

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Figure 2 Receiver operating characteristic curve for model for end-stage liver disease score.

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Figure 3 Receiver operating characteristic curve for platelet count.

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Figure 4 Receiver operating characteristic curve for creatinine.

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Figure 5 Receiver operating characteristic curve for total bilirubin.

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  Discussion Top


This study was characterized by being prospective and carried out on a relatively large number of patients (90 adult known chronic HCV patients of both sexes) scheduled for elective cardiac surgery with the use of CPB machine.

Postoperatively, patients were categorized into two groups:
  1. Group N: it included 51 patients with no hospital morbidity or mortality.
  2. Group M: it included 39 patients with hospital morbidity (according to SOFA score or any of the additional morbidities not captured by SOFA score) or mortality (defined by EuroSCORE II).


In the present study, it was found that the main postoperative complications for patients with chronic viral hepatitis after cardiac surgery were cardiac complications (28.2%), which is consistent with Hsieh et al. [13] who showed that cardiac complications were the main postoperative complications for patients with liver disease; in addition, the same result was obtained by Lopez-Delgado et al. [25] who studied predictive risk factors but in cirrhotic patients undergoing heart surgery. However, Arif et al. [26] and Thielmann et al. [18] in two separate studies showed that renal complications were the postoperative complications found in patients with liver disease. Another report by Sugimura et al. [27] showed that hepatic complications were the main postoperative complications for patients with liver disease.

However, regardless of the main complication for patients with liver disease who have undergone cardiac surgery, the postoperative complication rate was very high in all these studies. Moreover, even when there is a minimal degree of impaired liver function in combination with elective surgery, the incidence of complications significantly increases, as demonstrated by the present study and previous reports by Hsieh et al. [13] and Bizouarn et al. [28].

The results of the present study demonstrated that preoperative factors associated with hospital morbidity or mortality include age, MELD score, platelet count, serum creatinine, and total serum bilirubin. These findings indicate that these factors may affect the postoperative complications for patients with hepatitis virus infection who have undergone the cardiac surgery. In addition, this study demonstrated that prolongation of the aortic cross-clamping and CPB times were strongly associated with hospital morbidity and death, which was confirmed by other researchers, showing that decisions about the surgical indications and operative method are important in liver dysfunction patients with low platelet counts or high MELD scores. However, these factors may be influenced by other variables.

Consequently, a multivariate logistic regression analysis was used to find independent risk factors for morbidity. Statistical analysis showed that only MELD score, cross-clamp time, and CPB time were independent risk factors for morbidity, which implied that the MELD score, cross-clamp time, and CPB time could affect the postoperative morbidity in patients with hepatitis virus infection.

Regarding age, in agreement with the results of the present study, Morisaki et al. [3] studied 42 cirrhotic patients who underwent cardiovascular operations and found that age was significantly associated with hospital morbidity in multivariate analysis; also, Teh et al. [17] evaluated 772 patients with cirrhosis who underwent abdominal, orthopedic, and cardiovascular surgery, and their results showed that age contributes to postoperative mortality risk and an age greater than 70 years added the equivalent of 3 MELD points to the mortality rate. In contrast, many studies [28],[29],[30] did not find any correlation between age and operative morbidity or mortality. Our result may be explained with increasing cardiopulmonary comorbidity associated with increasing age. In general, because only extremes of age (<18 years or >75 years) significantly affected mortality, age alone cannot be used as a predictor of mortality in most patients. Age with other variables may be used to counsel patients and their families before surgery is performed.

The EuroSCORE is the best quantitative system to assess the surgical risk factors and provide sound predictions of outcomes in cardiac surgery [31],[32]. However, the presence and/or severity of liver disease has not been included in established models of predicting cardiac surgical risk, despite the well-established impact of hepatic dysfunction on cardiac performance based on available studies about advanced liver dysfunction [18],[21].

Although the results of the present study showed a low mean EuroSCORE II value (1.12±0.56), 43% of patients experienced a significant morbidity or mortality postoperatively denoting that EuroSCORE II is not a sensitive tool for risk assessment in hepatic patients undergoing cardiac surgery with the use of CPB. The mean MELD score was 10.12±2.7; despite that there was a significant difference between the two groups according to the morbidity status. Results implied that MELD scores may affect hospital morbidity based on univariate analysis. Moreover, it was found that MELD score is an independent risk factor for morbidity based on multivariate analysis.

Similar to the CTP score, the MELD system has been validated extensively in many different patient groups with varying severity of liver disease [16],[32]. Whereas the CTP score has a range only between 5 and 15 and only three classes (classes A, B, and C), the MELD system has a much wider range of scores, usually between 6 and 40. Therefore, a finer calibration of morbidity risk is possible with MELD. The CTP score can only help predict whether the patient is in a low-risk, intermediate-risk, or high-risk group, but it cannot determine the specific risk for mortality at defined time points.

Many medical tools are used beyond their original intended scope, and often become the standard of care in their new application. The MELD score comprises three objective and commonly available laboratory values: international normalized ratio, total bilirubin, and creatinine. Meanwhile, the CTP classification uses subjective indicators, such as ascites and encephalopathy. The MELD score therefore has the advantages of simplicity and objectivity. In addition, an evaluation of renal function (serum creatinine level) is included in the MELD score but not in the CTP classification. Therefore, it is believed that the MELD score is a useful scoring system in hepatic patients undergoing cardiovascular operations. The present study also showed that preoperative serum creatinine and total serum bilirubin, which represent two individual components of the MELD score, were identified as the predictors to differentiate between groups N and M.

The present results indicated that the best cutoff value for MELD score was found to be 12, with an optimal sensitivity of 69% and a specificity of 96%. A MELD score exceeding 12 may therefore be a reliable predictive value for morbidity in patients with liver dysfunction undergoing cardiovascular operations. Hsieh et al. [13] studied 105 patients with documented chronic viral hepatitis who were subject to elective cardiac surgery; their analysis showed significant differences in MELD score, bilirubin, and smoking. Filsoufi et al. [30], on the other hand, studied 27 patients with cirrhosis who underwent cardiac surgery and reported that the CTP classification was a better predictor of hospital death than the MELD score. However, the reason of this conflicting result may be attributed to the relatively small sample size taken by Filsoufi et al., which makes the validation of MELD score as a predictor of outcome following cardiac surgery difficult.

Several studies showed that low platelet count was associated with a degree of fibrosis in chronic viral hepatitis patients [33],[34]. Filsoufi et al. [30] initially showed an association between preoperative platelet count and operative death in cirrhotic patients undergoing cardiac operations. In addition, preoperative platelet count was inversely related with the severity of cirrhosis as determined by the CTP class. Morisaki et al. [3] in their study showed that a platelet count of less than 9.6×104/μl was a good cutoff value for predicting postoperative morbidity, and indicates the presence of advanced liver fibrosis or cirrhosis. However, other studies did not define a clear cutoff value that was correlated with postoperative morbidity in cirrhotic patients undergoing cardiovascular operations.

The present study demonstrated that a preoperative platelet count of less than 15.0×104/μl was a significant risk factor predicting postoperative morbidity. This cutoff value therefore did not indicate advanced liver fibrosis or cirrhosis. However, other studies reported no difference in platelet count between the groups [27]. The reason for this conflicting result is that most of these studies contained in their groups patients with documented liver cirrhosis, and thus there were no statistical differences between groups; an example is demonstrated in the study by Lin et al [20], who investigated 55 patients with liver cirrhosis and compared between patients with mild cirrhosis (child A) and advanced cirrhosis (child B and child C), and in both groups platelet count was found to be low and ranged from 9.4 to 19.9×104/μl and 8.2 to 14.7×104/μl, respectively, which makes it difficult to find a significant difference between groups.

In the present study, intraoperative factors associated with hospital morbidity include CVP post-CPB, insulin resistance post-CPB, aortic cross-clamp, and CPB times.

CVP remains a useful tool for evaluating hemodynamic status if it is performed under controlled conditions. CVP has the great advantage of being able to be measured at the patient’s bedside without the need of invasive methods. Dynamic evaluation of CVP could be a reliable predictor of fluid responsiveness in patients under mechanical ventilation.

Limitations of CVP as a surrogate variable of preload are caused by the influence of intrathoracic and intra-abdominal pressures. However, these limitations do not impair the importance of CVP as the downstream pressure of the systemic venous system. Results found CVP post-CPB to be significantly correlated with short-term outcome. This hypothesizes that CVP could be a surrogate marker of underscored right ventricular failure, which can ultimately explain the higher morbidity, but this cannot confirm these suspicions.As regards insulin resistance, it is thought that inflammation induced by CPB may play a causative role in insulin resistance in the post-CPB period. It is well known that CPB exacerbates the catabolism and disturbed glucose homeostasis. In agreement with this Kuntschen et al. [35], in their study, found that insulin resistance was initiated by anesthesia and surgical trauma, and further accentuated by CPB, in association with elevated levels of hormones indicative of surgical stress.

Patients with liver disease often suffer from significant perioperative bleeding because of preoperative thrombocytopenia, platelet dysfunction, and low levels of coagulation factors. In the present study, morbidity group showed significant bleeding from chest tubes (mean: 1119.23±400.88 ml), with six patients needing re-exploration (6.6%), and blood products requirements were higher in the same group. An et al. [21] reported that 25% of patients required re-exploration for mediastinal bleeding. Murashita et al. [36] in their study, found that 33% of patients needed re-exploration for bleeding. The rate was much higher than in noncirrhosis patients and much more packed red blood cells, fresh frozen plasma, and platelets were needed. These results confirmed the bleeding tendency in liver disease patients after open heart surgery, which was almost demonstrated by several studies [13],[17],[18],[19],[20],[21].

In the present study, serum ChE, which is considered to be an index of hepatic functional reserve, failed to demonstrate any correlation with morbidity. In contrast, Hirata et al. [12] and Murashita et al. [36] in two different studies found that preoperative levels of serum ChE has been found to be an independent predictor of mortality in patients with liver cirrhosis undergoing open heart surgery. A reason for these conflicting results is that patients in the present study have a more milder form of liver dysfunction while both Hirata and Murashita studied patients with advanced liver cirrhosis.

The lower hematocrit percentage, higher renal functions, liver enzymes, and coagulation profile in the postoperative period might be a consequence of several other complications such as reduced liver function, significantly higher massive postoperative transfusion, and significantly higher rates of septicemia and other infections.

This study had some limitations. The most important limitation is that it was a single-center observational study. In addition, the types of operations were very mixed, ranging from low surgical interventions such as closure of an atrial septal defect and subaortic membrane to operations for valvular diseases and CPB. It is therefore difficult to evaluate the values for stratified surgical procedures because of the very small number for each surgical procedure.


  Conclusion Top


Careful consideration of operative indications and methods are necessary in chronic viral hepatitis patients with old age, high MELD scores, low platelet counts, and high serum creatinine and bilirubin. It is vital that liver dysfunction is added to the risk models, which are currently used to predict the postoperative morbidity of cardiac surgery patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11]



 

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