Abstract
Objective
Constipation following cardiac surgery is a frequently experienced complication in postoperative management. This study aimed to explore the incidence and risk factors for constipation after cardiac surgery.
Methods
We retrospectively analyzed data from 370 adult cardiac surgeries performed at our institution between January 2019 and December 2020. Postoperative constipation was defined as the absence of defecation for >144 hours after surgery. Participants were classified into a postoperative constipation or nonconstipation group. Multivariate logistic regression was performed to estimate the patient-specific perioperative factors associated with postoperative constipation.
Results
A total of 72 (19.5%) patients developed postoperative constipation. Patients in the postoperative constipation group had higher rates of prolonged intubation (P < .001), higher 30-day mortality (P < .001), and longer intensive care unit stay (P < .001) than those in the nonconstipation group. Gastrointestinal complications were more common in the postoperative constipation group; however, the difference was not statistically significant (P = .087). Multivariate analysis demonstrated that peripheral artery disease (odds ratio [OR], 3.18; 95% CI, 1.23-8.24; P = .017), prior percutaneous coronary intervention (OR, 2.34; 95% CI, 1.12-4.89; P = .024), prolonged intubation (OR, 3.14; 95% CI, 1.35-7.29; P = .008), delayed nutrition (OR, 3.40; 95% CI, 1.13-10.26; P = .030), and vasopressin use (OR, 5.79; 95% CI, 1.38-14.52; P = .012) were independently predictive of postoperative constipation.
Conclusions
In patients undergoing cardiac surgery, 5 predictive risk factors for postoperative constipation were identified. Understanding these predictive factors will aid in direct risk assessments and the development of targeted treatments to prevent postoperative constipation.
Key Words: cardiac surgery, constipation, gastrointestinal complication, intensive care, perioperative management
Postoperative constipation is associated with worse outcomes and identifiable risk factors.
Central Message.
Following cardiac surgery, 19.5% of patients experienced postoperative constipation, which was associated with a significantly longer ICU stay and increased 30-day mortality.
Perspective.
Risk factors for postoperative constipation after cardiac surgery overlap those of more lethal GI complications such as NOMI. Because constipation develops and can be diagnosed earlier, focusing on its occurrence in postoperative management may reduce risk for more serious GI complications.
Constipation is considered a relatively trivial matter in postoperative management after cardiac surgery. Contrasting with other critical problems—such as lethal bleeding and arrhythmia, and gastrointestinal (GI) complications such as GI bleeding, mesenteric ischemia, and pancreatitis—that can cause severe morbidity and mortality,1,2 postoperative constipation (POC) itself is not a fatal disease. Therefore, POC is often overlooked by cardiothoracic surgeons. However, POC is among the most frequent complaints of postoperative patients and is reported to increase the length of hospital stay and health care costs.3,4 Untreated POC can cause more severe GI complications such as stercoral perforation due to fecal impaction, which increases the invasiveness if abdominal surgery is required after cardiotomy. Furthermore, in general intensive care unit (ICU) patients, constipation has been associated with a broader range of clinical outcomes, including higher Sequential Organ Failure Assessment scores, increased incidence of acquired bacterial infections, prolonged ICU stays, and elevated mortality.5, 6, 7 Although POC is not a life-threatening problem, it is not negligible regarding patient satisfaction and the prevention of more invasive complications. The aims of the present study were therefore to reveal the incidence of POC in cardiac surgery, clarify the risk factors for POC, and analyze the relationship between POC and clinical outcomes.
Subjects
This retrospective study reviewed the medical records of patients who underwent adult cardiac surgery between January 2019 and December 2020 at the Asahikawa Medical University Hospital. Patients younger than age 18 years were excluded. Patients who died within 144 hours were excluded owing to the definition of POC (described below).
Methods
Definition of POC
Constipation is sometimes an ambiguous concept and is associated a difficult diagnosis.8 Generally, chronic constipation is diagnosed by subjective assessments, such as the degree of straining, a sense of incomplete evacuation, and difficulty in defecation.9 However, querying bowel movement patterns in an urgent setting is impractical, and evaluating a sense of evacuation in patients who are placed under sedation is impossible. Thus, we adapted the definition based only on objective assessment—the first defecation time—referring to several previous studies on intensive care.10, 11, 12 The first defecation time was defined as the first time that stool volume was recorded. Although the definition of constipation as the absence of bowel movements for either 72 hours or 144 hours remains controversial,10, 11, 12 in this study we defined constipation as the absence of defecation >144 hours postoperatively to target a more severely affected patient group. Patients were then classified into a POC (C group) or postoperative nonconstipation (NC group) group.
Perioperative Management
Following surgery, all patients were admitted to the ICU, and sedation during intubation was routinely administered with propofol upon ICU admission, with dexmedetomidine sometimes administered concomitantly. In cases of prolonged intubation, fentanyl was also used; however, all sedative agents were discontinued at extubation. The postoperative oral analgesic regimen consisted of routine acetaminophen administration at weight-appropriate doses, with additional intravenous acetaminophen and oral tramadol provided as needed based on the patient-reported pain. The patient's first oral fluid intake was permitted under nursing supervision 3 hours after extubation. If the patient passed a swallowing function assessment, oral feeding was initiated on the following day. There was no standardized protocol for laxative administration; thus, initiation was based on patient-reported symptoms and the individual physician's judgment.
Statistical Analysis
Continuous variables were presented as means ± SD, whereas categorical variables were presented as frequencies and percentages. Continuous variables were compared using the Student t test for normal distributions, as verified using the Kolmogorov-Smirnov test. For nonnormally distributed data, the Mann-Whitney rank sum test was used. Categorical variables were compared using the χ2 test, and Fisher exact test was used for small sample sizes (n < 5). All statistical analyses were performed using IBM SPSS Statistics version 28.0.1 (IBM-SPSS Inc).
Ethical Approvals
This study was approved by the ethics committees of our hospital on June 25, 2022 (approval No.: 19,285). Given the retrospective, observational nature of the study design, the Ethics Committee waived the requirement of informed consent.
Results
Incidence of POC
Among 414 patients, after excluding patients younger than age18 years (n = 38) and those who died within 144 hours (n = 6), 370 patients were analyzed. A total of 298 (80.5%) patients defecated within 144 hours after surgery, whereas 72 (19.5%) patients reported POC in this study cohort. Figure 1 shows the first defecation day after surgery; the median first defecation day was 4 days after surgery.
Figure 1.
First defecation day after surgery. The median first defecation day was 4 days after surgery. We defined postoperative constipation (POC) as the absence of defecation >144 hours after surgery, and the incidence of POC was 19.5%. Patients were then classified into a postoperative nonconstipation (NC group) or POC (C group) group. NC, Nonconstipation; C, constipation; POD, postoperative.
Patient Characteristics and Postoperative Factors
A comparison of the preoperative data between the 2 groups is shown in Table 1. There were no significant differences between the 2 groups regarding age, sex, or rates of obesity and diabetes mellitus, which are commonly indicated risk factors for chronic constipation. A history of peripheral artery disease (PAD) and percutaneous coronary intervention (PCI) were more common in the C than NC group. Preoperative acute coronary syndrome and shock status were significantly higher in the C group, together with a higher Japan SCORE, suggesting that the C group contained more high-risk patients than the NC group. This trend was more apparent when considering the operative details: combined and emergent operations were more common in the C group, with longer operative times and more patients requiring an assistive circulatory device (Table 2).
Table 1.
Preoperative status of patients
| Characteristic | Overall (N = 370) | Constipation group (n = 72) | Nonconstipation group (n = 298) | P value |
|---|---|---|---|---|
| Age (y) | 69.3 ± 12.7 | 70.9 ± 10.1 | 68.9 ± 13.3 | .234 |
| >65 | 268 (72.4) | 58 (80.6) | 210 (70.5) | .086 |
| >80 | 58 (15.7) | 12 (16.7) | 46 (15.4) | .797 |
| Male | 219 (59.2) | 43 (59.7) | 176 (59.1) | .918 |
| Height (cm) | 160.3 ± 11.0 | 160.4 ± 8.6 | 160.3 ± 11.5 | .906 |
| Body weight (kg) | 60.7 ± 13.5 | 63.3 ± 14.9 | 60.1 ± 13.1 | .521 |
| BMI | 23.5 ± 4.1 | 24.4 ± 4.6 | 23.3 ± 3.98 | .265 |
| Obesity: BMI >26 | 102 (27.6) | 24 (33.3) | 78 (26.2) | .222 |
| Smoking habit | 162 (43.8) | 34 (47.2) | 128 (43.0) | .512 |
| Diabetes mellitus | 113 (30.5) | 24 (33.3) | 89 (29.9) | .566 |
| Insulin use | 24 (6.5) | 4 (5.6) | 20 (6.7) | .741 |
| Hyperlipidemia | 214 (58.0) | 42 (58.3) | 172 (57.9) | .948 |
| Chronic kidney disease | 122 (33.0) | 28 (38.9) | 94 (31.5) | .234 |
| Hemodialysis | 37 (10.0) | 11 (15.3) | 26 (8.7) | .096 |
| Creatinine (mg/dL) | 1.67 ± 2.19 | 2.09 ± 2.76 | 1.56 ± 2.02 | .136 |
| eGFR (mL/min/1.73 m2) | 55.6 ± 27.2 | 49.1 ± 26.5 | 57.1 ± 27.2 | .024 |
| Hypertension | 277 (74.9) | 55 (76.4) | 222 (74.5) | .740 |
| Active IE | 18 (4.9) | 3 (4.2) | 15 (5.0) | .759 |
| COPD | 38 (10.3) | 11 (15.3) | 27 (9.1) | .119 |
| Steroid use | 13 (3.5) | 3 (4.2) | 10 (3.4) | .737 |
| CHF | 166 (44.9) | 37 (51.4) | 129 (43.3) | .215 |
| Peripheral artery disease | 33 (8.9) | 14 (19.4) | 19 (6.4) | <.001 |
| Prior PCI | 54 (14.6) | 20 (27.8) | 34 (11.4) | <.001 |
| ACS | 32 (8.6) | 13 (18.1) | 19 (6.4) | .002 |
| Shock | 34 (9.2) | 19 (26.4) | 15 (5.0) | <.001 |
| Laxative use | 84 (22.7) | 20 (27.8) | 64 (21.5) | .252 |
| >2 Laxative use | 15 (4.1) | 6 (8.3) | 9 (3.0) | .040 |
| Japan SCORE | 8.8 ± 10.8 | 15.3 ± 15.4 | 7.1 ± 8.6 | <.001 |
Values are presented as n (%) or mean ± SD. BMI, Body mass index; eGFR, estimated glomerular filtration rate; IE, infective endocarditis; COPD, chronic obstructive pulmonary disease; CHF, chronic heart failure; PCI, percutaneous coronary intervention; ACS, acute coronary syndrome.
Table 2.
Intraoperative characteristics
| Variable | Overall (N = 370) | Constipation group (n = 72) | Nonconstipation group (n = 298) | P value |
|---|---|---|---|---|
| Operative procedures | ||||
| CABG | 116 (31.4) | 33 (45.8) | 83 (27.9) | .003 |
| Valve | 193 (52.2) | 27 (37.5) | 166 (55.7) | .006 |
| Aorta | 83 (22.4) | 23 (31.9) | 60 (20.1) | .031 |
| Others | 46 (12.4) | 10 (13.9) | 36 (12.1) | .676 |
| Isolated | 298 (80.5) | 52 (72.2) | 246 (82.6) | .047 |
| Combined | 69 (18.6) | 21 (29.2) | 48 (16.1) | .011 |
| MICS | 52 (21.8) | 0 (0) | 52 (27.4) | < .001 |
| Redo | 34 (9.2) | 5 (6.9) | 29 (9.7) | .463 |
| Emergency | 72 (30.4) | 20 (40.8) | 52 (27.7) | .074 |
| Operative time (min) | 299.8 ± 153.9 | 353.0 ± 270.6 | 287.0 ± 105.7 | < .001 |
| Operative time >5 h | 155 (41.9) | 40 (55.6) | 115 (38.6) | .009 |
| Operative time >6 h | 82 (22.2) | 23 (31.9) | 59 (19.8) | .026 |
| Cardiopulmonary bypass time (min) | 146.6 ± 68.3 | 157.5 ± 73.3 | 144.0 ± 67.0 | .136 |
| Myocardial ischemia time (min) | 94.5 ± 56.8 | 99.1 ± 54.9 | 93.4 ± 57.4 | .440 |
| Minimal rectal temperature (°C) | 32.1 ± 3.6 | 30.9 ± 4.3 | 32.4 ± 3.4 | .002 |
| Rectal temperature <28 °C | 78 (21.1) | 23 (31.9) | 55 (18.5) | .012 |
| Hypothermic circulatory arrest | 74 (20.0) | 20 (27.8) | 54 (18.1) | .066 |
| IABP | 15 (4.1) | 8 (11.1) | 7 (2.3) | .003 |
| ECMO | 9 (2.4) | 5 (6.9) | 4 (1.3) | .016 |
Values are presented as n (%) or mean ± SD. CABG, Coronary artery bypass grafting; MICS, minimally invasive cardiac surgery; IABP, intra-aortic balloon pumping; ECMO, extracorporeal membrane oxygenation.
Postoperative factors are shown in Table 3. The duration of ICU stay was significantly longer (Figure 2, A), and the number of patients requiring prolonged intubation, sedative use, and inotropic administration higher in the C than NC group. There was no difference in the length of hospital stay between the 2 groups, and the 30-day mortality was significantly higher in the C group (Figure 2, B and C).
Table 3.
Postoperative factors
| Variable | Overall (N = 370) | Constipation group (n = 72) | Nonconstipation group (n = 298) | P value |
|---|---|---|---|---|
| ICU stay (d) | 4.8 ± 6.0 | 8.2 ± 8.0 | 4.1 ± 5.1 | <.001 |
| >7 d ICU stay | 62 (16.8) | 32 (44.4) | 30 (10.1) | <.001 |
| >72 h Intubation | 62 (16.8) | 31 (43.1) | 31 (10.4) | <.001 |
| First defecation (POD) | 4.6 ± 2.7 | 9.1 ± 2.9 | 3.6 ± 1.3 | <.001 |
| Postoperative creatinine (mg/dL) | 2.08 ± 2.31 | 2.42 ± 2.22 | 2.00 ± 2.33 | .156 |
| Peak lactate (mg/dL) | 34.9 ± 20.0 | 41.5 ± 25.9 | 33.4 ± 18.1 | .002 |
| Fentanyl use | 70 (18.9) | 23 (31.9) | 47 (15.8) | .002 |
| Fentanyl use period (d) | 0.6 ± 1.4 | 1.3 ± 2.1 | 0.4 ± 1.1 | <.001 |
| Adrenaline use | 0 (0) | 0 (0) | 0 (0) | – |
| Noradrenaline use | 247 (66.8) | 54 (75.0) | 193 (64.8) | .098 |
| Noradrenaline use period (d) | 1.8 ± 1.8 | 2.6 ± 2.4 | 1.6 ± 1.6 | <.001 |
| Noradrenaline use >3 d | 97 (26.2) | 29 (40.3) | 68 (22.8) | .003 |
| Noradrenaline use >4 d | 53 (14.3) | 19 (26.4) | 34 (11.4) | .001 |
| Vasopressin use | 45 (12.2) | 26 (36.1) | 19 (6.4) | <.001 |
| Vasopressin use period (d) | 0.3 ± 1.1 | 1.1 ± 1.8 | 0.2 ± 0.7 | <.001 |
| Vasopressin use >3 d | 20 (5.4) | 11 (15.3) | 9 (3.0) | <.001 |
| 30-d mortality | 19 (5.1) | 11 (15.3) | 8 (2.7) | <.001 |
| Hospital stay POD (d) | 21.0 ± 17.4 | 24.4 ± 16.1 | 20.2 ± 17.7 | .068 |
| Hospital stay POD >30 d | 57 (15.4) | 14 (19.4) | 43 (14.4) | .290 |
| GI complications | 15 (4.1) | 6 (8.3) | 9 (3.0) | .087 |
Values are presented as mean ± SD or n (%). ICU, Intensive care unit; POD, postoperative day.
Figure 2.
Postoperative outcomes. A, The length of intensive care unit (ICU) stay was significantly longer in constipation group (C group). B, The length of hospital stay was slightly longer in the C group, and the difference approached significance. C, The 30-day mortality was significantly higher in the C group. D, Gastrointestinal (GI) complications were more common in the C group, although the difference was not statistically significant. The upper and lower borders of the box represent the upper and lower quartiles, the middle horizontal line represents the median, and the upper and lower whiskers represent the maximum and minimum values of nonoutliers. Extra dots represent outliers.
GI Complications
GI complications were more common in the C group; 9 (3.0%) patients in the NC group and 6 (8.3%) patients in the C group experienced GI complications, although the difference was not statistically significant (P = .087) (Figure 2, D). Details of the GI complications are listed in Table E1. Two cases of nonocclusive mesenteric ischemia were observed in the C group, and both patients died within 30 days after surgery.
Univariate Analysis for POC
Univariate analysis revealed the following parameters as significant risk factors for POC (Table 4): PAD (P < .001), prior PCI (P < .001), laxative therapy (P < .049), operative time (P = .008), peak lactate (P = .003), prolonged intubation (P < .001), delayed nutrition (P < .001), perioperative fentanyl use (P < .001), perioperative noradrenaline use (P = .003), and perioperative vasopressin use (P < .001).
Table 4.
Univariate and multivariate analysis for postoperative constipation
| Variable | Univariate analysis |
Multivariate analysis |
||
|---|---|---|---|---|
| Odds ratio (95% CI) | P value | Odds ratio (95% CI) | P value | |
| Age (y) | 1.01 (0.99-1.04) | .234 | ||
| Male sex | 1.03 (0.61-1.74) | .918 | ||
| Obesity (BMI >26) | 1.41 (0.81-2.45) | .224 | ||
| Diabetes mellitus | 1.17 (0.68-2.03) | .567 | ||
| Chronic hemodialysis | 1.89 (0.88-4.03) | .101 | ||
| Peripheral artery disease | 3.54 (1.68-7.47) | <.001 | 3.18 (1.23-8.24) | .017 |
| Prior PCI | 2.99 (1.60-5.59) | <.001 | 2.34 (1.12-4.89) | .024 |
| Laxative therapy (>2) | 2.92 (1.00-8.49) | .049 | ||
| Operative time | 1.00 (1.00-1.01) | .008 | ||
| Circulatory arrest | 1.74 (0.96-3.15) | .068 | ||
| Peak lactate | 1.02 (1.01-1.03) | .003 | ||
| Prolonged intubation | 6.51 (3.59-11.83) | <.001 | 3.14 (1.35-7.29) | .008 |
| Delayed nutrition | 8.72 (3.50-21.73) | <.001 | 3.40 (1.13-10.26) | .030 |
| Fentanyl (>3 d) | 4.44 (2.14-9.24) | <.001 | ||
| Noradrenaline (>3 d) | 2.28 (1.33-3.93) | .003 | ||
| Vasopressin (>3 d) | 5.79 (2.30-14.58) | <.001 | 4.48 (1.38-14.52) | .012 |
BMI, Body mass index; PCI, percutaneous coronary intervention; GI, gastrointestinal.
Multivariate Analysis for POC
To identify a high-risk cohort for POC, multivariate analysis of the perioperative factors was performed; the results are shown in Table 4. PAD, prior PCI, prolonged intubation, delayed nutrition, and vasopressin use were independent risk factors. As shown in Figure 3, the frequency of POC and postoperative GI complications increased as the number of risk factors increased; in particular, all patients who had 4 of the 5 risk factors experienced POC. None of the patients in the study cohort exhibited all 5 risk factors for POC.
Figure 3.
Number of risk factors and incidence of postoperative constipation and gastrointestinal (GI) complications. The frequency of postoperative constipation (POC) and postoperative GI complications increased as the number of risk factors increased.
Discussion
The crucial findings of the present study were that the incidence of POC after cardiac surgery was 19.5% in this study cohort; peripheral artery disease, prior PCI, prolonged intubation, delayed nutrition, and vasopressin use were independent risk factors for POC; and patients who experienced POC tended to experience other GI complications and exhibited significantly higher 30-day mortality (Figure 4).
Figure 4.
Summary of this study. In this study cohort, the incidence of postoperative constipation (POC) following cardiac surgery was 19.5%. Five predictive risk factors for POC were identified, and the incidence of both POC and postoperative gastrointestinal (GI) complications increased proportionally with the number of risk factors present. As these risk factors overlapped with those associated with more severe GI complications, such as nonocclusive mesenteric ischemia, recognizing and monitoring POC may aid in the early identification of patients at elevated risk for serious GI complications. NC, Nonconstipation; C, constipation; POD, postoperative day; PCI, percutaneous coronary intervention; NOMI, nonocclusive mesenteric ischemia.
Few studies have focused on the incidence of constipation after thoracic surgery. Iyigun and colleagues3 and Rasmussen and colleagues4 reported rates of 39% and 50%, respectively; however, in both studies, the diagnosis of constipation was based on subjective measurements. The enrolled patients were limited to those who could answer the interviews; therefore, the results likely contain a selection bias. The present study included patients who were sedated or ventilated after surgery, which reflects the real-world settings of postoperative cardiac surgery management.
Previous studies on constipation in intensive care revealed that the incidence of constipation ranged from 24% to 34%,10, 11, 12 especially when using the same definition as in the present study; that is, the absence of defecation for >144 hours. Our results are almost equivalent to those of previous studies, and both our study and previous studies commonly point to delayed nutrition as a risk factor for constipation. Patients with delayed nutrition are often in a critically ill condition and may require higher doses of vasoactive drugs or sedatives, which may contribute to constipation through their pharmacological effects. Additionally, delayed initiation of nutrition may interrupt mechanical stimulation of peristaltic activity, potentially leading to constipation.10 However, in critically ill patients, various causes—such as hypoxia and hypotension—prevent the early initiation of enteral nutrition. In patients with hemodynamic instability after cardiac surgery, enteral nutrition transiently reduces mean arterial pressure due to an accompanying increase in splanchnic blood flow.13 Recent guidelines recommend withholding enteral nutrition in hemodynamically unstable patients.14 Therefore, although the importance of early enteral nutrition is well recognized, its administration should be undertaken with caution, considering the patient's overall condition.
In the present study, PAD and prior PCI—both arteriosclerotic diseases—were identified as risk factors for POC. Previous large cohort study also indicated that PAD is a risk factor for GI complications after cardiac surgery.2 Atherosclerotic changes in blood vessels develop through systemic processes rather than local pathophysiological mechanisms,15,16 and calcification in an abdominal branch artery has been associated with lesions in other major arteries; for example, the coronary arteries.15 Takeyoshi and colleagues17 demonstrated that calcification of the main abdominal arteries due to progressive atherosclerosis is associated with an increased risk of mesenteric ischemia after cardiac surgery. Following cardiac surgery, the systemic inflammatory response, exacerbated by cardiopulmonary bypass use, can reduce splanchnic blood flow18; this reduction may occur even when overall circulatory status appears stable.19 On the basis of these findings, it can be hypothesized that patients with advanced atherosclerosis may also have lesions in the abdominal branches and intestinal vessels, rendering them more susceptible to the effects of perioperative blood flow reduction. However, further studies are warranted to confirm this hypothesis.
The risk factors for POC detected in the present study overlapped with those of mesenteric ischemia and nonocclusive mesenteric ischemia (NOMI) after cardiac surgery.1,20, 21, 22, 23 Sato and colleagues20 detected prolonged ventilation and norepinephrine use as risk factors for NOMI, and Lim and colleagues21 reported old age, postoperative vasoactive-inotropic use, and high lactate levels. Deng and colleagues22 reported 14 risk factors for postoperative acute mesenteric ischemia after cardiac surgery in their systematic review and meta-analysis, which included peripheral vascular disease, prolonged ventilation, and inotropic use. Groesdonk and colleagues24 reported that the use of norepinephrine, especially at dosages of 0.1 μg/kg/min or higher, increases the risk of NOMI, and they discussed the possibility that this may cause circulatory failure in the intestinal microvasculature. The overlapping risk factors for POC, mesenteric ischemia, and NOMI suggest that they have a common pathological basis. Thus, by focusing on the presence of these common risk factors, it may be possible to identify high-risk groups for myocardial infarction, NOMI, and POC.
POC is a prodromal symptom of mesenteric ischemia and NOMI, and common risk factors are associated with these complications. In this study, 2 of the patients who were diagnosed with POC experienced NOMI thereafter. Although mesenteric ischemia and NOMI are rare complications of cardiac surgery, their mortality rates are high.1,17,20,21 The diagnosis is difficult, and a definitive diagnosis involves invasive examinations—such as mesenteric angiography and multidetector computed tomography—that are often difficult to perform in critically ill patients. Conversely, POC can be noninvasively diagnosed by only observing defecation patterns, and its diagnosis is made 6 days after surgery when based on the definition adapted in the present study. The median duration between surgery and the diagnosis of NOMI has been reported to be 9 to 14 days1,20; thus, POC can be diagnosed beforehand, leading to simple screening for patients at a high risk of NOMI. Moreover, although monitoring patients’ bowel movement patterns for screening, early intervention for constipation may include implementing a standardized, stepwise increase in laxative administration, as outlined in Enhanced Recovery After Surgery (ERAS) pathway, and combining laxatives with different mechanisms of action.25,26
The risk factors identified here suggest that the etiology of POC is complex, and its management, including prevention, requires a multifaceted strategy. In addition to systemic atherosclerotic changes, the use of vasopressor agents to stabilize patient's perioperative hemodynamics may reduce bowel blood flow and impair motility. Therefore, appropriate perioperative fluid management aimed at preserving intestinal perfusion is important and may also help prevent hard stool formation. Furthermore, as shown in our univariate analysis, where prolonged fentanyl administration was statistically significant, the use of sedatives is associated with POC, and immobilization, including prolonged intubation, is a contributing factor. Thus, the ERAS pathway incorporates early extubation and early mobilization as part of its protocol, providing specific strategies worth considering.25, 26, 27
Similarly, the ERAS pathway recommends initiating POC management early with a combination of stool softeners and stimulant laxatives.25,26 because this approach may address both motility disorders and hard stool formation. In this protocol, beginning on postoperative day 1, docusate 100 mg is administered orally each night together with a bisacodyl 10 mg suppository; if no bowel movement occurs, lactulose 20 g orally is added from postoperative day 2. Docusate is a representative stool softener, whereas lactulose, like polyethylene glycol and magnesium oxide, is an osmotic laxative that also softens stools. Bisacodyl is a stimulant laxative, with senna available as an oral alternative. This regimen may also be supplemented with prokinetic agents; for example, prucalopride, and with probiotics. Available agents vary by institution and country, and in addition to classical agents, newer medications with different mechanisms of action have expanded treatment options; thus, postoperative bowel management protocols should be periodically reviewed and updated.
Patients who developed POC had a significantly longer ICU stay and higher 30-day mortality than those who did not develop POC; although the hospital stay was also longer in the former patients, the difference was not statistically significant. Regarding the preoperative condition of the patients, the C group demonstrated a higher severity and preoperative risk, and a longer operating time. Inevitably, the postoperative intubation duration and inotropic administration were also higher, and the start of nutrition administration tended to be delayed. Such critically ill patients are at higher risk of POC, and the occurrence of POC may subsequently lead to more severe GI complications, requiring careful postoperative management.
Study Limitations
This study had several limitations; first, this was a retrospective analysis of prospectively collected observational data from an institutional database. Owing to the small sample size, nonhomogenized patient backgrounds may have influenced the results and identification of risk factors. Specifically, the proportion of patients with acute coronary syndrome or shock before surgery was higher in the C group than in the NC group, and the proportion of emergency and complex surgeries was also higher in the former group. This suggests that compared with patients in the NC group, those in the C group were more severely ill and underwent more invasive surgery, which may have influenced the outcomes. Regarding the association between POC and severe GI complications, only 2 patients developed NOMI after the occurrence of POC; thus, further case accumulation is needed to clarify this relationship.
Second, the definition of constipation remains controversial.10, 11, 12 Some studies define it as the absence of bowel movements for >72 hours, associating this with the onset of NOMI and postoperative ileus.28,29 Other studies have applied the 72-hour and 144-hour definitions, with the latter associated with poor prognosis in ICU settings.10,12 In our cohort, the median time to first defecation was 4 days, and applying the 72-hour definition would have included 81.9% of patients. Therefore, to better identify a subgroup with greater severity for risk factor analysis, we adopted the 144-hour definition. The definition of constipation should continue to be discussed in the future.
Third, the analysis of confounding factors that could influence POC and other clinical outcomes was insufficient. Clinically relevant details, including intubation duration, sedative administration, and postoperative mobilization; for example, ambulation, were not adequately recorded or analyzed, potentially affecting the results as confounding variables. Furthermore, at the time of this study, no standardized protocols existed for postoperative bowel management or mobilization; these interventions were implemented based on patient-reported symptoms and the preferences of individual physicians, resulting in a lack of standardization. Hence, accurate analysis of these confounding factors could provide additional insight, and further research is warranted. Additionally, the type of therapeutic intervention used postoperatively and after the occurrence of POC has not been investigated, and future studies are required to determine appropriate treatment and prevention methods.
Conclusions
The incidence of POC after cardiac surgery was 19.5% in this study cohort, and 5 factors were identified as predictive risk factors for POC. Understanding these predictive factors will aid in direct risk assessments and the development of targeted treatments to prevent POC.
Conflict of Interest Statement
The authors reported no conflicts of interest.
The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.
Footnotes
Ethical approval: Date: 25 June 2022, Number: 19285.
Informed consent: Given the retrospective, observational nature of the study design, the Ethics Committee waived the requirement of informed consent.
Appendix E1
Table E1.
Details of gastrointestinal complications
| Patient group | Age (y) | Sex | Procedure | 30-d mortality |
|---|---|---|---|---|
| NC group (n = 9) | 74 | M | GI bleeding | |
| 54 | M | IMA pseudoaneurysm bleeding | ||
| 41 | M | Pancreatitis | ||
| 60 | F | C diff colitis | ||
| 77 | F | GI bleeding | ||
| 72 | M | Colon perforation | ||
| 74 | M | GI bleeding | ||
| 82 | M | GI bleeding | ||
| 66 | M | Ileus | ||
| C group (n = 6) | 67 | M | NOMI | (+) |
| 73 | F | Abdominal compartment syndrome | ||
| 75 | M | GI bleeding | ||
| 71 | M | GI bleeding | (+) | |
| 63 | M | Ischemic enteritis, intestinal pneumatosis | ||
| 70 | F | NOMI | (+) |
NC, Nonconstipation; M, male; GI, gastrointestinal; IMA, inferior mesenteric artery; C diff, Clostridium difficile; C, constipation; NOMI, nonocclusive mesenteric ischemia.
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