| Abstract |
Coronary artery bypass on a beating heart (off-pump coronary
artery bypass grafting or OPCABG) has become common in the last
ten years in an attempt to decrease the complications associated
with the use of extracorporeal circulation. There is also evidence
that a new technique of OPCABG, which is performed with the use
of bilateral skeletonized internal mammary arteries avoiding any
procedure on the ascending aorta and a sternal closure technique
based on alternative placement of figure of eight and single sternal
wires, can further decrease sternal wound infections.
In the retrospective part of the study, we examined the
frequency, characteristics, and predisposing factors of postoperative
infections, in a large cohort of patients undergoing OPCABG surgery
over a period of 39 months (January 2001 - March 2004) at “Henry
Dunant” Hospital, Athens, Greece. Cases were patients who
developed microbiologically documented nosocomial infection.
Patients who underwent valve surgery combined with coronary
artery bypass surgery were excluded from the study.
Twenty-one of 782 (2.7%) studied patients developed
microbiologically documented nosocomial infection after OPCABG.
Six of 782 studied patients (0,77%) developed sternal wound
infection [4 (0.51%) developed superficial wound infection and 2
(0.26%) mediastinitis], 8 patients (1.02%) developed pneumonia, 7
(0.90%) bacteremia, 4 (0.51%) urinary tract infection (UTI), and 1
(0.13%) developed pressure sore infection. Four patients had
120
infections at two or more different sites. Specifically, 1 patient had
UTI and mediastinitis, 1 UTI and pressure sore infection, 1
pneumonia and bacteremia, and 1 pneumonia, urinary tract
infection, and bacteremia. Thus, there were 26 episodes of
microbiologically documented infections in 21 patients.
The backward stepwise multivariable logistic regression model
revealed that independent risk factors associated with development
of microbiologically documented nosocomial infection were arterial
hypertension, previous vascular surgery, urgent operation,
postoperative atrial fibrillation, number of inotrops used during
operation and after operation, transfusions of fresh frozen plasma
during ICU stay and ICU stay until development of infection. The
nosocomial mortality of the studied patients was 14/782 (1.79%).
There was statistically significant difference in mortality between
patients with microbiologically documented nosocomial infection
(5/21, 23.8%) and the rest of the patients who did not develop
nosocomial infection (9/773, 1.2%), (p<0.001). However, the
statistical analysis showed that independent risk factors for death
were: urgent operation, anaemia (Ht<34%), and low left ventricular
ejection fraction on admission (p<0.001).
In the prospective part of the study, we also evaluated the
frequency, risk factors, characteristics, and mortality of infections in
360 adult patients after off-pump coronary artery bypass grafting
(OPCABG). The prospective cohort study was performed during the
121
period 06/2004-10/2005 at “Henry Dunant” Hospital, Athens,
Greece. Cases were patients who developed nosocomial infections
after OPCABG. Samples of serum for assay of C-reactive protein
(CRP) and procalcitonin were obtained from a subgroup of patients
preoperatively, 24, 48, and 72 hours following cardiac surgery. At
least one sternal wound culture was received from each patient
when he was transferred from ICU to the ward. Additional sternal
wound cultures were received from patients with suspected sternal
wound infection. Various variables were examined as possible risk
factors of nosocomial infections and death after OPCABG.
Out of 360 adult cases undergoing OPCABG surgery, 18
patients (5%) developed postoperative nosocomial infections.
Seven of them (1.9%) developed sternotomy wound infection [one
patient (0.3%) developed mediastinitis, and 6 patients (1.7%)
developed superficial wound infection]. Five patients (1.4%)
developed pneumonia, 4 (1.1%) developed bacteremia, 1 (0.3%)
developed intra-aortic balloon pump (IABP) related infection, and
afterwards (17 days after OPCABG) candidemia (0.3%). One patient
(0.3%) developed pressure sore infection. Three patients had
infections from two different sites. Specifically, except from 1
patient with IABP-related infection and candidemia, 1 patient had
pneumonia and bacteremia, and 1 had superficial wound infection
and bacteremia. Thus, there were 21 episodes of infections in 18
patients.
122
Ninety-five microorganisms were isolated from 80 out of 377
(21.2%) sternal wound cultures (received from 359 patients), while
no microbes were isolated from the rest 297 (78.8%). The isolated
organisms were gram-positive cocci, gram-negative microbes, and
fungi. The most common isolates from sternal wound cultures were
gram-positive cocci [74 of 95 isolates (77.9%)]. Gram-negative
microbes were less common isolated in sternal wound cultures but
had greater positive predictive value in sternal wound infections
(5/18, 27.8%) compared with gram-positive cocci (7/74, 9.5%),
although this difference was not significant (p=0,054, Fischer exact
test).
The mean increase of CRP and procalcitonin levels in the first
two or three days respectively after surgery was significantly higher
(p<0.05) in the group of patients who developed infection
compared to patients without infection. Independent risk factors
(p<0.05) associated with development of infection were history of
major nervous system disorder, history of heart failure
preoperatively, a very urgent operation, transfusions of red blood
cells during ICU stay, and duration of central venous catheter
placement.
The mortality of the studied patients was 4/360 (1.1%).
Specifically, the mortality was 2/18 (11.1%) for patients who
developed infection, and 2/242 (0.6%) for the patients who did not
develop nosocomial infection (p< 0.05). Although infection was
123
statistically associated with the studied outcome (mortality) in the
bivariable analysis, the backward stepwise multivariable logistic
regression model revealed that independent risk factors for death
were: history of major nervous system disorder, and perioperative
use of inotrops.
In conclusion, the frequency of superficial wound infection,
pneumonia, bacteremia, and urinary tract infection in this study is
similar to the results of previous studies. However, the rate of
mediastinitis of the studied population was lower than the rates that
were observed in previous studies. Thus, there is evidence that this
new technique of OPCABG that combines the use of bilateral
skeletonized internal mammary arteries with a sternal closure
technique based on alternative placement of figure of eight and
single sternal wires not only did not increase deep sternal wound
infections but could further decrease them.
In addition, the identification of risk factors for infection after
OPCABG surgery in combination with the appropriate use and
evaluation of the results of diagnostic tests will help clinicians to
identify cases with high probability for infection and afterwards to
put the diagnosis early, especially in cases in which diagnosis is
difficult. Regarding the role of CRP and procalcitonin levels, previous
studies have shown that CRP and procalcitonin are not specific
markers for infection. For example, high concentrations of
procalcitonin were found in patients with three or more criteria for
124
the diagnosis of systemic inflammatory response syndrome,
postoperative pulmonary dysfunction, myocardial infarction and
cardiogenic shock. Our study adds to the literature the finding that
CRP and procalcitonin also increased in patients with postoperative
complications after off-pump coronary artery bypass surgery and
that increase was higher for patients with infection compared to
patients without infection during the first three postoperative days.
|
Search
