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Interact CardioVasc Thorac Surg 2006;5:239-242. doi:10.1510/icvts.2005.117382 © 2006 European Association of Cardio-Thoracic Surgery
Incidence and outcome of gastrointestinal complications after cardiopulmonary bypass
a Department of Cardiothoracic Surgery, University of Cologne, Germany Received 27 July 2005; received in revised form 17 January 2006; accepted 18 January 2006
*Corresponding author: Klinik für Herz- und Thoraxchirurgie, im Klinikum der Universität zu Köln, Joseph-Stelzmann-Str. 9, 50924 Köln, Germany. Tel.: +49 221 478 4128; fax: +49 221 478 4186.
Gastrointestinal complications (GI-complications) after CPB are rare, but are associated with high mortality and hospital cost. This retrospective analysis investigates the incidence, patient profile and post-operative course of GI-complications after CPB. The charts of 8869 adult patients, operated on CPB between 1995 and 2002, were reviewed. Patients with post-OP GI-complications were compared to a control group of 1057 consecutive patients operated on CPB between 05/2000 and 04/2001. The incidence of GI-complications was 0.79% with an overall mortality of 21.5% (vs. 3% in controls, P<0.05). Most frequent were upper GI-tract-bleeding (58%), followed by pancreatitis (11%) and cholecystitis (10%). GI-complications were diagnosed 9.2±5.9 days after surgery, with 58.5% after a primarily uneventful post-op course. Compared to control, patients with GI-complications showed no difference in pre-operative comorbidity and EuroSCORE. However, surgery of the thoracic aorta, prolonged CPB time, and necessity for re-thoracotomy was significantly more frequent in patients with GI-complications (P<0.05). GI-complications after CPB remain a rare, but dreaded complication associated with high mortality. Early diagnosis may require a high degree of clinical vigilance as the majority of GI-complications occurred after a primarily uneventful post-op course. Age, co-morbidity, and EuroSCORE were not different between patients with GI-complications and control.
Key Words: Peri-operative complications; Gastrointestinal tract; Gastrointestinal hemorrhage; Risk factors
Constant advancements in operative technique and post-operative management have effected a continuous extension of patient selection criteria in cardiac surgery. The result of this ongoing process is a significant increase in age, severity of cardiac disease and overall morbidity of cardiac surgery patients. One important consequence of this development is the increased post-operative incidence of extra-cardiac organ complications, such as renal, pulmonary, and cerebrovascular dysfunction. The prophylaxis, early diagnosis, and treatment of these extra-cardiac organ complications has gained decisive clinical significance for the management and outcome of cardiac surgery patients. Among extra-cardiac organ complications, the post-operative occurrence of gastrointestinal complications (GI-complications) remains one of the most dreaded, due to its high mortality and extensive consumption of hospital resources [1]. Protocols and procedures of intra- and post-operative care have been adjusted in recent years to fit a considerably sicker patient popuation and to account for the increased risk profile of current cardiac surgery patients. Therefore, it was the purpose of this study to investigate the incidence, pattern, and outcome of gastrointestinal complications in the current cardiac surgery patient population of our institution and to compare these results to the findings of prior investigations.
2.1. Patients with GI-complications (GI-comp) The charts of all patients, operated on CPB between 01.01.1995 and 31.12.2002 in our institution, who were at least 14-years-old at the time of surgery, were retrospectively reviewed for the occurrence of GI-complications. In addition, all autopsy reports of patients operated on CPB between 1995 and 2002 were reviewed. We defined as GI-complication any post-operative event associated with the gastrointestinal tract, which required an invasive diagnostic or therapeutic intervention, such as gastroscopy, colonoscopy, laparotomy or laparoscopy. To qualify as a GI-complication, a gastrointestinal pathology (such as an intestinal bleeding source) had to be confirmed during the invasive procedure. Between 01.05.2000 and 30.04.2001, 1057 consecutive adult patients operated on CPB in our institution were prospectively analyzed for pre-operative morbidity, operative procedure, and post-operative outcome. Data from this group served as control for patients with GI-complications. The following parameters were documented in the GI-comp and Control group:
2.4. Statistical analysis Data are expressed as mean±standard deviation. For comparisons between groups a Student t-test or  2-test was used, as appropriate. Odds-ratios and confidence intervals were calculated using the SPSS software package for Windows, release 10.0.7 (SPSS Inc, Chicago, IL, USA). A P-value <0.05 was considered significant.
The charts of 8986 adult patients, operated in our institution on CPB between 1995 and 2002 were reviewed for GI-complications. In these patients we found 71 GI-complications in 65 patients (group GI-comp). The most frequently noted complication was upper GI-bleeding (41 complications), followed by pancreatitis (8), cholecystitis (7), bowel ischemia (6), ileus (5), and colon perforation (4). Overall incidence of GI-complications was 7.9 per 1000 CBP-patients or 0.79% (Fig. 1).
Patient profile, pre-operative morbidity, and EuroSCORE showed no significant difference between patients with GI-complications (GI-comp) and Control (Table 1). Combined surgery, prior cardiac surgery, emergent surgery, and surgery of the thoracic aorta were more frequent in the GI-comp group, however, statistically significant was only the difference for surgery of the thoracic aorta (P<0.001). Likewise, necessity for re-thoracotomy or circulatory support were more frequent in the GI-comp group than in controls, but significant was only the difference for re-thoracotomy (P<0.001, Table 2). There was no difference for aortic crossclamp time between groups, but total CPB time and reperfusion time were significantly longer in the GI-comp group (P<0.005 and 0.013, respectively; Table 3). The odds-ratio for GI-complications increased with the length of the CPB time (Table 4).
Mortality was significantly higher in the GI-comp group in comparison to control and showed substantial differences between the different forms of GI-complications (Fig. 2). Likewise, the length of ICU stay was significantly longer in the GI-comp group (Fig. 3).
The mean time point of onset for GI-complications was 9.3±5.9 days after surgery. In 58.5% of patients, GI-complications occurred after transfer from the ICU to the regular ward after a primarily uneventful postoperative course (Fig. 4).
In this retrospective analysis, GI-complications after cardiopulmonary bypass showed an overall incidence of 0.79% and were associated with a mortality of 21.5%. In comparison with a control group of 1057 consecutive CPB patients, who were operated in our institution within the time span of the retrospective analysis, there was no significant difference in pre-operative patient profile and EuroSCORE value, however, thoracic aortic surgery, return to surgery, and prolonged CPB time were significantly more frequent in patients with GI-complications. The occurrence of life-threatening GI-complications after CPB was reported for the first time by Berkowitz in 1963, a few years after the clinical introduction of the heart-lung-machine [2]. In this report, four out of seven patients, who developed acute upper gastrointestinal bleeding after CPB, died. Thereafter, the incidence, pattern and outcome of GI-complications after CPB have been investigated in numerous studies [1–6]. The reported incidence of GI-complications varies between 0.12 to 3.0% with an associated mortality of 11 to 63% [1–6]. Several reports agree, that the poor outcome of GI-complications after CPB is at least in part due to the frequently delayed diagnosis of this complication [3]. Typical symptoms of GI-tract disease may be masked by routine analgesic treatment in the conscious patient, or GI-symptoms may be practically absent in the sedated and ventilated ICU patient. Furthermore, brief episodes of unspecific gastrointestinal complaints such as poor appetite, lack of taste, or nausea, occur in about 20–40% of patients after cardiac surgery [7]. It is important to note that the clinical onset of GI-complications is not necessarily immediately after surgery, but may develop after a delay of several days [8]. In the current study, GI-complications occurred at a mean of 9.3±5.9 days after surgery and in nearly 60% of patients after a primarily uneventful post-operative course. As delayed diagnosis of GI-complications is often associated with unfavourable outcome, identification of patients at risk seems desirable. In the absence of a reliable biochemical marker, conventional statistics have been used to define patients at risk for GI-complications. By these means, a number of risk factors have been identified, such as age, redo surgery, combined surgery, need for mechanical circulatory support, prolonged CPB time and others [1,4,5,9]. However, the overall incidence of GI-complications is too low to give any of these identified risk factors a statistical relevance that would justify a change in post-operative care other than increased clinical vigilance for GI-symptoms. Interestingly, there is no significant evidence that a patient history of GI-disease prior to surgery would be associated with an increased risk for GI-complications [3]. In the current study, the most frequently noted complication was upper GI-bleeding, which is in accordance with the results of others [1,3,9]. Only two out the 41 patients with upper GI-bleeding in this study, had a history of gastritis or peptic ulcers. All patients in the current study had received ranitidine or equivalent medication postoperatively for at least two days as part of the standard post-operative treatment protocol. However, the benefit of routine histamine2-receptor antagonist administration for stress ulcer prophylaxis in cardiac surgery patients has not been validated in randomized trials [10]. With regard to possible risk factors for GI-complications, our data showed no difference in patient profile and EuroSCORE value, but indicated that intra-operative factors, such as CPB time and certain post-operative events, such as necessity for return to surgery, are of greater significance for the development of GI-complications.
It has been shown that mesenteric ischemia and acidosis leading to intestinal ischemia can occur during CPB despite unchanged blood flow in the mesenteric vessels [11]. In fact, most of the inflammatory mediators which are released during CPB have the ability to affect vasomotor tone [12]. In the mesenteric of the rat, CPB induces endothelial dysfunction and an increase in the contractile response to In summary, the results of this study are in gross accordance with the findings of prior investigations. GI-complications after CPB have a very low incidence, but were associated with a high mortality. Remarkable in this study was that almost 60% of GI-complications occurred after a primarily uneventful post-operative course with the patient already transferred from intensive or intermediate care to the regular ward. As the mean time of onset for GI-complications was about 9 days after surgery, a high degree of clinical vigilance for the onset of GI-tract symptoms seems warranted, even in patients who did apparently well immediately after surgery. Early diagnosis and timely therapeutic interventions appear to be the most effective means for improving the poor outcome of GI-complications after CPB. Although GI-complications were associated with prolonged CPB time in this study, the role of CPB for splanchnic injury remains controversial and further research into the pathophysiolgy of gastrointestinal hypoperfusion during cardiac surgery, either on-pump or off-pump, seems justified.
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