Constipation in intensive care unit: Incidence and
Antonio Paulo Nassar Jr. MD
⁎, Fernanda Maria Queiroz da Silva MD
Roberto de Cleva PhD
Department of Medicine, Discipline of Medical Emergencies, University of São Paulo, São Paulo-SP CEP 02402-400, Brazil
Department of Gastroenterology, University of São Paulo, São Paulo-SP CEP 02402-400, Brazil
Purpose: Although gastrointestinal motility disorders are common in critically ill patients, constipation
and its implications have received very little attention. We aimed to determine the incidence of
constipation to find risk factors and its implications in critically ill patients
Materials and Methods: During a 6-month period, we enrolled all patients admitted to an intensive
care unit from an universitary hospital who stayed 3 or more days. Patients submitted to bowel surgery
Results: Constipation occurred in 69.9% of the patients. There was no difference between constipated
and not constipated in terms of sex, age, Acute Physiology and Chronic Health Evaluation II, type of
admission (surgical, clinical, or trauma), opiate use, antibiotic therapy, and mechanical ventilation.
Early (b24 hours) enteral nutrition was associated with less constipation, a finding that persisted at
multivariable analysis (Pb.01). Constipation was not associated with greater intensive care unit or
mortality, length of stay, or days free from mechanical ventilation.
Conclusions: Constipation is very common among critically ill patients. Early enteral nutrition is
associated with earlier return of bowel function.
© 2009 Elsevier Inc. All rights reserved.
Gastrointestinal motility disturbances are common in
critically ill patients [1,2]. Abnormalities in gastric emptying
 and diarrhea  are well studied and have a considerable
impact in critically ill patients' prognoses. However,
constipation has received much less attention in clinical
studies. Outside the intensive care unit (ICU) setting,
constipation is a common symptom, affecting 2% to 27%
of the population . It seems that constipation has great
implications in quality of life outside the ICU , but it was
not a symptom reported in ICU patients' surveys [7,8].
There is not a homogeneous definition of constipation
across studies. It has been defined as absence of bowel
movements within 3 ,6,or9 days without bowel
movements and either as need for treatment with laxatives or
enemas according to the attending physician . Conse-
quently, the incidence of constipation in ICU setting is
E-mail address: email@example.com (A.P. Nassar).
0883-9441/$ –see front matter © 2009 Elsevier Inc. All rights reserved.
Journal of Critical Care (2009) 24, 630.e9–630.e12
variable, ranging from 15% to 83% [9-12],probably
according to the sensitivity of the chosen criteria.
There are few studies addressing constipation as a specific
problem. Observational studies have found a correlation
between constipation, organ dysfunction, prolonged length
of stay, and failure to wean from mechanical ventilation,
although results diverge among studies [9,11].
There are many factors that may contribute to constipation
in critically ill patients. Shock causes splanchnic hypoperfu-
sion, which is associated with impaired gastrointestinal
motility. Electrolyte disturbances, mainly hypokalemia and
hypomagnesemia, are also associated with decreased
intestinal motility. Some drugs commonly used in ICU
may also be involved. Opiates, which are the commonest
prescribed analgesics in ICU, inhibit intestinal motility and
have a venodilator property that can decrease venous return
and, maybe, impair perfusion to a great level .
Fecal stasis induces overgrowth of gram-negative bacteria
in the digestive tract. Translocation of bacteria and
endotoxins may lead to infections and enhanced systemic
inflammatory response .
The aim of our study is to determine the incidence of
constipation in a surgical ICU to find risk factors and its
implications in critically ill patients.
2.1. Study subjects
We conducted a survey in a surgical ICU of a university
hospital. Our ICU is a 14-bed unit that receives immediate
postoperative and patients from surgical wards with medical
problems. All patients admitted to the ICU and who stayed
for 3 or more days in ICU were included in the study. We
choose this criterion because the first study that addressed
constipation in ICU setting defined constipation as a “failure
of bowel to function for 3 consecutive days”. Patients
were excluded if they did not stay in ICU for 3 or more days
because of rapid recovery or death. Bowel surgery patients
were also excluded. The study was approved by local ethics
committee. Because all data were collected from patient
records and there was no influence on patients' treatment,
informed consent was waived.
2.2. Study protocol
We collected the following data from all patients: age,
sex, reason for admission (medical, surgical, and type of
surgery, or trauma), Acute Physiology and Chronic Health
Evaluation II (APACHE II) score, antibiotic therapy, opiate
use, early enteral nutrition (before or after 24 hours from ICU
admission), use of renal replacement therapy, days free of
mechanical ventilation at day 28, length of stay in ICU, ICU
mortality, and hospital mortality.
For patients requiring mechanical ventilation, midazolam
and fentanyl were continuously infused in 2 separated
pumps aiming a Ramsay sedation score of 2 to 3  at
discretion of the attending physician. It is practice in this
unit to proceed with a “daily wakening”during nursing
morning changing shifts (7 AM). Enteral nutrition was
initiated in all patients at discretion of the attending
physician. There is no specific protocol to begin enteral
nutrition. It is not common practice in our unit to use
laxatives or fecal emollients, but data regarding these
medications was recorded.
Weaning from mechanical ventilation is initiated when
patients are hemodynamically stable, have an adequate
level of conscience (Glasgow Coma Score N8), a PaO
relation greater than 150 with an FiO
less than 40% and a
positive end-expiratory pressure lower than 8 cm H
an adequate cough reflex , as evaluated by physiother-
All data were prospectively collected daily by 2 trained
researchers (APNJ and FMQS) from patients' charts and
were inserted in an electronic database.
2.3. Statistical analyses
All continuous variables are presented as medians and
interquartile ranges (IQRs) and were compared with Mann-
Whitney test. Categoric variables are presented as percen-
tages and were compared with χ
or Fisher exact test, as
appropriate. The following variables were entered in a
logistic regression analysis to find factors independently
associated with constipation: age, sex, reason for admission
(surgical vs not surgical), opiate use, previous antibiotic use,
and early enteral nutrition. All statistics were 2 tailed, and a
Pb.05 was considered to be significant. All analyses were
performed using SPSS version 10.0 (SPSS, Chicago, Ill).
A total of 371 patients were admitted during the study
period (February to July 2006). Eighty-eight patients were
excluded because of bowel surgery and 177 patients because
of staying less than 3 days. A total of 106 patients fulfilled
study criteria. These patients were predominantly male
(64.2%), 61 (IQR, 50-72) years old, and with an APACHE II
of 18 (IQR, 12-22).
Seventy-six patients (71.7%) were admitted intubated,
with a median of days free from mechanical ventilation of
13.5 (IQR, 0-24). Intensive care unit mortality was of 37.7%
and hospital mortality of 46.2%.
Sixty-three patients (59.5%) were admitted directly from
the surgery. Gastrointestinal surgery was performed in 45
patients (42.5%). Other types of surgery were vascular
(6.6%), head and neck surgery (3.8%), neurosurgery
(2.8%), urologic (1.9%), and plastic (1.9%). Thirty-eight
630.e10 A.P. Nassar Jr. et al.
(35.8%) patients were admitted for medical reasons and 5
(4.7%) for trauma.
A total of 73 (69.9%) patients were considered con-
stipated according to the definition chosen. No patient used
laxatives or fecal emollients during the first 3 days in ICU. At
univariate analysis, early enteral nutrition was negatively
associated with constipation (Table 1). There was a trend
toward constipation among surgical patients when compared
exclusively with medical patients, although it did not reach
statistical significance (47 patients [74.6%] vs 21 patients
[48.5%], P= .07). There were also no differences between
surgical and trauma patients (47 patients [74.6%] vs 5
patients [100%], P= .33) or medical and trauma patients (21
patients [48.5%] vs 5 patients [100%], P= .14). Among
surgical patients, constipation was not more frequent in
gastrointestinal surgery patients than in patients submitted to
other types of surgery (34 patients [75.5%] vs 13 patients
[72.2%], P= .76).
When logistic regression analysis was performed, the
only variable independently associated with constipation
continued to be enteral nutrition (odds ratio, 0.16; 95%
confidence interval, 0.05-0.45; Pb.001).
Constipation was not associated with any complication as
can be seen in Table 2.
Constipation is still a poorly understood complication of
critically ill patients. To the best of our knowledge, there
were only 5 studies that addressed this question [9-13,16].
Two were observational trials that addressed specifically the
impact of constipation in critically ill patients [9,11], 2 were
trials that tested specific therapies to constipation [10,16],
and the last was a trial that intended to find the complications
of enteral nutrition in critically ill patients, and constipation
was one of the least important (15%) . The largest trial
addressing constipation was a randomized trial recently
published that compared lactulose and ethylene glycol with
the specific aim to find which drug could cause an increase in
defecation among patients enrolled . Our study is the
largest observational trial that intended to find risk factors
and implications of constipation on patients' outcomes.
Although there was a variable incidence reported, it
seems it is a very common problem. In a cohort of 44
patients from a clinical study of selective gastrointestinal
decontamination, the mean time from admission to the first
defecation was 6 days. This study showed that patients had
no bowel movement during 56.6% of their ICU stay .
Our study found an incidence of almost 70%, using a
definition previously used of 3 days without a bowel
movement . We have used this definition because it may
be the most sensitive.
Our study was the first to demonstrate that the early
beginning of enteral nutrition is associated with a decreased
incidence of constipation. Experimental and clinical studies
have demonstrated that enteral nutrition better preserves the
gastrointestinal mucosal structure and function . There-
fore, defecation may be seen as a sign of preservation of
gastrointestinal function. Because there is a tendency to face
impaired gastrointestinal motility as a manifestation of
multiple organ dysfunctions, early enteral nutrition may be
seen as a protective factor.
Another interesting finding of our study was that opiate
use was not associated with an increased incidence of
constipation. One possible explanation is that the opiate used
in our unit is fentanyl. Studies that have shown association
between opiates and constipation used morphine [10,11,16].
At least for treatment of cancer pain, fentanyl is associated
with less constipation than morphine [18,19]. This finding
must be prospectively evaluated in critically ill patients
before any conclusion be made.
Antibiotic therapy was not associated with either increase
or decrease in incidence of constipation.
Other clinical trials demonstrated that constipation was
associated with failure to wean from mechanical ventilation
, increased length of stay, higher severity of illness, higher
mean doses of vasopressors, more days on mechanical
ventilation , and increased mortality . We did not
find these associations in our cohort. This may be in part of
some differences among our and the other trials cited. We did
not search for failure to wean from mechanical ventilation.
Although median free days from mechanical ventilation were
Table 1 Baseline patients' characteristics
(n = 73)
(n = 33)
Age 59 (49-72) 64 (51-70.5) .53
Male sex 44 (60.3) 24 (72.7) .31
APACHE II 18 (12-22) 18 (12-21.5) .88
Opiate use 47 (64.4) 19 (57.6) .65
Antibioticotherapy 53 (75.7) 22 (66.7) .70
Mechanical ventilation 53 (72.6) 23 (69.7) .94
Early enteral diet 14 (19.2) 19 (57.6) b.01
All continuous data are presented as medians (IQR), and all
categoric data are presented as numbers (percentages).
Table 2 Implications of constipation in critically ill patients'
(n = 73)
(n = 33)
Renal replacement therapy 17 (23.3) 5 (15.2) .41
Days free of mechanical
ventilation at day 28
11 (0-23.5) 17 (0-25) .54
ICU length of stay (d) 8 (5-16.5) 6 (4-13.5) .35
ICU mortality 29 (39.7) 11 (33.3) .68
Hospital mortality 31 (42.5) 18 (54.5) .25
All continuous data are presented as medians (IQR), and all categoric
data are presented as numbers (percentages).
630.e11Constipation in ICU: Incidence and risk factors
not different between constipated and nonconstipated
patients in our cohort, maybe constipated patients have had
more failure attempts to wean and could have less days on
mechanical ventilation. Mortality attributed to constipation
was increased only in a recent clinical trial addressing the
effect of 2 laxatives in critically ill patient . The authors
found on a logistic regression analysis that not producing
stools when on study medication was independently
associated with in-hospital mortality. This finding, although
interesting, must be interpreted with caution. First, it was not
constipation per se associated with an increased mortality,
but failure to defecate when using study medications
(lactulose and polyethylene glycol). Second, it was found
on a multivariate analysis and was not the primary outcome
of this study. However, it is a tempting hypothesis that
deserves to be studied.
Our study has obvious several limitations. First, it has an
observational design. Therefore, it has all limitations
commonly implied with this kind of study. Most importantly,
no finding here can be interpreted as causal relationship.
Second, many data cited in other studies were not available.
Of note, we cite the use of vasoactive agents.
In conclusion, our study shows that constipation was a
common event in this cohort of critically ill patients.
However, it was not associated with any adverse outcome.
The early beginning of enteral nutrition was associated with
an earlier return of bowel function. More studies are
necessary to definitively assess the course of bowel function
in critically ill patients and when it can affect outcomes.
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