Asian Cardiovasc Thorac Ann 2005;13:316-320
© 2005 Asia Publishing EXchange Ltd
Nosocomial Infections and Balloon Counterpulsation: Risk Factors and Outcome
Mandakini Pawar, BSc,
Yatin Mehta, FRCA,
Abdul Ansari, MD,
Rajeev Nair, MD,
Naresh Trehan, MD
Department of Anaesthesiology and Critical Care, Escorts Heart Institute and Research Center, New Delhi, India
For reprint information contact: Yatin Mehta, FRCA Tel: 91 11 2682 5000 Fax: 91 11 5162 8442 Email: yatinmehta{at}hotmail.com, Department of Anaesthesiology and Critical Care, Escorts Heart Institute and Research Centre, New Delhi 110 025, India.
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ABSTRACT
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Between February and September 2003, 136 (5.3%) of 2,558 patients undergoing cardiac surgery were supported with intra-aortic balloon counterpulsation. There were 71 infected (group 1) and 65 noninfected (group 2) patients. Risk factors for nosocomial infections were identified by univariate and multivariate analysis. On univariate analysis, significant risk factors were operation time, balloon pump duration, ventilation hours, duration of central venous catheter placement, amount of blood transfused, left ventricular ejection fraction < 30%, intra- and/or postoperative intra-aortic balloon counterpulsation, surgery under cardiopulmonary bypass, combined procedures, re-exploration, and Acute Physiology And Chronic Health Evaluation (APACHE) II score. On multivariate analysis, ventilation hours and amount of blood transfused were independently associated with group 1. Respiratory tract infections were common in the balloon counterpulsation population (41.1%). Mortality was significantly higher in patients needing balloon pump support (19.9%) compared to controls (1.1%), but it was similar in groups 1 and 2. Recognition of risk factors for postoperative infection in patients undergoing cardiovascular surgical procedures with intra-aortic balloon counterpulsation may help to improve their prognosis and allow more organized surveillance.
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INTRODUCTION
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Nosocomial infection after cardiovascular operations represent serious complications associated with substantial morbidity, mortality, and economic burden.1–2 Since its first use by Kantrowitz and colleagues3 in 1968, use of intra-aortic balloon counterpulsation (IABC) has increased, particularly over the past decade with the expansion of interventional cardiology and the increasing age of cardiac surgical patients.4 Institution of IABC was found to be a risk factor for nosocomial infections.5 The mortality rate ranges from 41.2% in the early years of instigation of IABC to 20% by 1995.4 The aim of this study was to determine the risk factors for, and outcome of, nosocomial infections in patients undergoing cardiovascular operations who underwent IABC. Identification of predictors of nosocomial infection in the IABC population could help to reduce the impact of these infections on critically ill patients.
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PATIENTS AND METHODS
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Approval of the institutional review board and informed consent of the patients were obtained for this prospective study. It was conducted at Escorts Heart Institute and Research Center between February and September 2003. During this period, 136 (5.3%) of 2,558 patients undergoing cardiac surgery were supported with IABC. The patients were divided into two groups: group 1 comprised 71 patients who developed a nosocomial infection, and group 2 included the 65 who did not become infected. The definition of nosocomial infection (urinary tract, blood stream, or wound infection) was based on the criteria of the Center for Disease Control6. Pulmonary infection was defined as ventilator-associated pneumonia if the onset was recorded after at least 48 hours of intermittent positive-pressure ventilation and if the following criteria were present: chest radiography showing a new and persistent infiltrate consistent with pneumonia; purulent sputum; elevated temperature > 38°C or leukocyte count 
10,000·mL–1 or 
1,000·mL–1 ; microorganisms isolated from either bronchoalveolar lavage, endotracheal aspirate, or sputum.7 Infected patients were defined as those in whom at least one episode of nosocomial infection developed in the postoperative period. Nosocomial infection in patients already discharged from the hospital was included only in the case of readmission. Of the 136 patients, 9 (6.6%) were readmitted.
The patients were routinely administered stress ulcer prophylaxis (ranitidine 50 mg intravenously 3 times daily). All patients received intravenous antibiotic prophylaxis with cefazolin 1 g thrice daily before the insertion of IABC or before surgery. Diabetic patients received additional gentamicin 1 mg·kg–1 3-times daily for 36 hours. Patients were extubated when they had satisfactory arterial blood gases on a fraction of inspired oxygen of 0.4–0.5, with 4–5 cm positive end-expiratory pressure, spontaneous ventilation, and normothermia, and when they were neurologically normal and hemodynamically stable. Blood transfusion was given if the hemoglobin level was < 9 g·dL–1. Intraoperatively, all patients received autotransfusion.
During the study, the following risk factors were recorded: age, gender, type of surgery, underlying illness, operative procedure, previous cardiac operation, re-exploration, New York Heart Association functional class, time of insertion and duration of IABC, left ventricular ejection fraction (LVEF), duration of operation, total duration of ventilation, duration of central venous catheter (CVC) insertion, intensive care unit (ICU) stay, postoperative hospital stay, units of blood and blood products transfused, and Acute Physiology And Chronic Health Evaluation (APACHE) II score. The timing of IABC was classified as preoperative, intraoperative, or postoperative. The LVEF values were grouped into three categories: 40%, 30–39%, and < 30%.
Univariate analysis was used to identify factors with significant unadjusted effects on nosocomial infections. Multiple logistic regression was applied to determine the significance or independent effects of such variables on nosocomial infections. All statistical tests were 2-tailed and the level of significance was set at 0.05. Results are expressed as mean ± standard deviation.
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RESULTS
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There were 117 males and 19 females, with a mean age of 60.0 ± 9.4 years. Combined operations for coronary artery disease and valvular heart disease were performed in 26 (19%) patients (Table 1
). In univariate analysis, combined operations were significantly higher in group 1 than group 2 (30% vs. 8%, p = 0.001). Preoperative IABC was used in a significantly higher number of group 2 patients (51% vs. 32%, p = 0.030). Patients with LVEF < 30% were significantly associated with group 1 (51% vs. 31%, p = 0.034).
Table 2 shows the results of univariate analysis of variables that were not significantly associated with nosocomial infections. Age, gender, diabetes, hypertension, chronic obstructive pulmonary disease, asthma, obesity, emergency surgery, previous cardiac operation, and functional class were not significantly different between the two groups. However, univariate analysis (Table 3) showed operation time, IABC duration, total ventilation hours, duration of CVC, total transfusion of blood and blood products, APACHE II score, LVEF < 30%, intra- and/or postoperative IABC, surgery with cardiopulmonary bypass, combined procedures, re-exploration, total ICU stay, and postoperative hospital stay were significantly associated with group 1.
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Table 2. Univariate Analysis of Preoperative Variables in 71 Infected (Group 1) and 65 Noninfected (Group 2) Patients
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Multiple stepwise logistic regression showed that ventilation hours and transfusion of blood and blood products were independently associated with group 1 (Table 4). Nosocomial infections occurred in 71 (52%) patients. Respiratory tract infection was the most common (56 patients, 41%) followed by bacteremia (14 patients, 10%), urinary tract infection (13 patients, 10%), and surgical site infection (7 patients, 5%). Pseudomonas aeruginosa was the most frequent bacterial species isolated in patients with respiratory tract infection (39%) and bacteremia (43%), whereas Staphylococcus species were the most common in surgical site infection (10%) and Candida in urinary tract infection (54%).
Mean ICU stay and postoperative hospital stay were significantly higher in group 1 (Table 5). Mortality was higher in group 1, but this was not statistically significant. The overall mortality rate was significantly higher ( p < 0.001) in IABC patients (19.9%) compared to the control group (1.1%) of 2,422 patients who did not require IABC. Multi-organ dysfunction syndrome (MODS) was significantly associated with non-survivors in the infected IABC population (39% vs. 0%, p = 0.024).
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DISCUSSION
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Duration of mechanical ventilation, duration of IABC, and duration of CVC are well-established risk factors for nosocomial infections.8–9 All three factors were significantly associated with group 1. Decreasing the time a patient is placed on these medical devices should help to reduce the overall incidence of hospital-acquired infections. Several studies have shown that early extubation and removal of invasive lines, catheters, and chest tubes can be carried out safely among selected patients undergoing cardiac surgery.10 The results of multivariate analysis showed that total ventilation hours was an independent predictor of nosocomial infection in the IABC population.
Despotis and colleagues11 determined a number of factors associated with post-CPB transfusion of blood products, including prolonged CPB, combined procedures, and repeat procedures. Hardy and colleagues12 noted that combined procedures and re-operations were associated with increased administration of blood products. Blood transfusions appear to increase the susceptibility to infection in surgical patients. Few studies have been designed to assess the influence of blood transfusion on the development of postoperative infection in patients undergoing cardiac surgery.13 Recent data suggest that these patients are transfused excessively; therefore, a decreased number of transfusions could contribute to a reduction in morbidity and mortality.14 We found that combined procedures and re-exploration were significantly higher in group 1. We also noted an independent association of blood transfusion with group 1.
The length of the operation also has a significant effect on the occurrence of postoperative infection.15 In our study, operative time was significantly longer in group 1. As in other reports, we found that patients undergoing combined CABG and valve operations had a significant association with nosocomial infections.9,15 The likely explanation for this is longer mechanical ventilation, greater hemodynamic instability with longer duration of CVC, more blood transfusions, and longer operation time in these procedures. Patients with low LVEF benefit from close surveillance, cardiovascular monitoring, and invasive devices; however, such devices are also associated with increased risk of complications including infection.16 The exact role that infection plays in worsening the prognosis in these patients is difficult to assess as they are critically ill and their clinical status is severe enough to cause infection. We found that patients with LVEF of < 30% were significantly associated with group 1.
A number of studies have found that preoperative IABC was associated with better outcomes than intra- or postoperative insertion.4 We found that preoperative insertion of a balloon pump was significantly higher in group 2 compared to group 1. Preoperative IABC is probably used more electively and hence better sterility is maintained. Also, preoperative IABC may make the patient more hemodynamically stable with a shorter ventilation time postoperatively. Off-pump coronary artery bypass (OPCAB) is increasingly being carried out all over the world as a safe alternative to conventional CABG. Reduced inflammatory response, less bleeding, reduced transfusion requirement, a lower incidence of renal dysfunction, early extubation, and shorter ICU and hospital stay with reduced cost have been shown.17 This explains why there were more OPCAB patients in group 2. Early mobilization and physiotherapy to prevent atelectasis and superinfection are difficult in ventilated patients with IABC. Kollef and colleagues18 associated the supine position of mechanically ventilated patients with an approximately three-fold increased risk of ventilator-associated pneumonia compared with patients in a semi-recumbent position. We found that respiratory tract infection was the most common complication in group 1.
Patients acquiring nosocomial infections have significantly greater APACHE II scores and are more likely to develop MODS compared to noninfected patients.19 The development of MODS, aortic crossclamp time, and severity of illness have been found to be independent risk factors for hospital mortality.19 In this study, APACHE II score and incidence of MODS were significantly higher in group 1. We also found that the development of a nosocomial infection increased the length of stay for patients surviving their hospitalization. Therefore, even if reductions in mortality may not be obvious, shorter hospital stay and decreased medical care costs could be achieved by reducing these infection rates. Our study suggests that minimally invasive cardiac surgery, appropriate and optimal use of IABC, decreasing patient exposure to invasive devices including mechanical ventilation, and minimal use of blood and blood products along with infection-control measures should have the greatest overall impact on hospital-acquired infections.
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REFERENCES
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- Li LY, Wang SQ. A prospective study of nosocomial infections in cardiac surgery patients in China. Am J Infect Control 1990;18:365–70.[Medline]
- Li LY, Wang SQ. Economic effects of nosocomial infections in cardiac surgery. J Hosp Infect 1990;16:339–41.[Medline]
- Kantrowitz A, Tjonneland S, Freed PS, Phillips SJ, Butner AN, Sherman JL Jr. Initial clinical experience with intraaortic balloon pumping in cardiogenic shock. JAMA 1968;203:113–8.[Abstract/Free Full Text]
- Torchiana DF, Hirsch G, Buckley MJ, Hahn C, Allyn JW, Akins CW, et al. Intraaortic balloon pumping for cardiac support: trends in practice and outcome, 1968 to 1995. J Thorac Cardiovasc Surg 1997;113:758–69.[Abstract/Free Full Text]
- Olsen MA, Lock-Buckley P, Hopkins D, Polish LB, Sundt TM, Fraser VJ. The risk factors for deep and superficial chest surgical-site infections after coronary artery bypass graft surgery are different. J Thorac Cardiovasc Surg 2002;124:136–45.[Abstract/Free Full Text]
- Garner JS, Jarvis WR, Emori TG, Horan TC, Hughes JM. CDC definitions for nosocomial infections, 1988. Am J Infect Control 1988;16:128–40.[Medline]
- Pawar M, Mehta Y, Khurana P, Chaudhary A, Kulkarni V, Trehan N. Ventilator-associated pneumonia: Incidence, risk factors, outcome, and microbiology. J Cardiothorac Vasc Anesth 2003;17:22–8.[Medline]
- Vincent JL, Bihari DJ, Suter PM, Bruining HA, White J, Nicolas-Chanoin MH, et al. The prevalence of nosocomial infection in intensive care units in Europe. Results of the European Prevalence of Infection in Intensive Care (EPIC) Study. EPIC International Advisory Committee. JAMA 1995; 274:639–44.[Abstract/Free Full Text]
- Aksnes J, Abdelnoor M, Berge V, Fjeld NB. Risk factors of septicemia and perioperative myocardial infarction in a cohort of patients supported with intra-aortic balloon pump (IABP) in the course of open heart surgery. Eur J Cardiothorac Surg 1993;7:153–7.[Abstract]
- Hickey RF, Cason BA. Timing of tracheal extubation in adult cardiac surgery patients. J Card Surg 1995;10(4 Pt 1):340–8.[Medline]
- Despotis GJ, Filos KS, Zoys TN, Hogue CW Jr, Spitznagel E, Lappas DG. Factors associated with excessive postoperative blood loss and hemostatic transfusion requirements: a multivariate analysis in cardiac surgical patients. Anesth Analg 1996;82:13–21.[Abstract]
- Hardy JF, Perrault J, Tremblay N, Robitaille D, Blain R, Carrier M. The stratification of cardiac surgical procedures according to use of blood products: a retrospective analysis of 1480 cases. Can J Anaesth 1991;38(4 Pt 1):511–7.
- Blumberg N, Heal JM. Transfusion and recipient immune function. Arch Pathol Lab Med 1989;113:246–53.[Medline]
- Goodnough LT, Johnston MF, Toy PT. The variability of transfusion practice in coronary artery bypass surgery. Transfusion Medicine Academic Award Group. JAMA 1991;265:86–90.[Abstract/Free Full Text]
- Rebollo MH, Bernal JM, Llorca J, Rabasa JM, Revuelta JM. Nosocomial infections in patients having cardiovascular operations: a multivariate analysis of risk factors. J Thorac Cardiovasc Surg 1996;112:908–13.[Abstract/Free Full Text]
- Castelli P, Condemi A, Munari M, Savi C, Carro C, Vanelli P. Intra-aortic balloon counterpulsation: outcome in cardiac surgical patients. J Cardiothorac Vasc Anesth 2001;15:700–3.[Medline]
- Mehta Y, Juneja R. Off-pump coronary artery bypass grafting: new developments but a better outcome? Curr Opin Anaesthesiol 2002;15:9–18.[Medline]
- Kollef MH. Ventilator-associated pneumonia. A multivariate analysis. JAMA 1993;270:1965–70.[Abstract/Free Full Text]
- Kollef MH, Sharpless L, Vlasnik J, Pasque C, Murphy D, Fraser VJ. The impact of nosocomial infections on patient outcomes following cardiac surgery. Chest 1997;112:666–75.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
