Introduction: We hypothesized to demonstrate whether there are significant differences in blood endotoxin (Et) levels after abdominal aortic surgery between endovascular aortic repair (EVAR) and open abdominal surgery. Methods: The patients who underwent the surgical treatment for abdominal aortic aneurysm were divided into two groups according to the procedures: open abdomen surgery (OP) and EVAR (SG). The value of Endotoxin Activity Assay (EAA) was compared between groups. Results: After surgery, Et level was significantly higher in the OP group than in the SG group on postoperative day 3. Neutrophil count was significantly higher in the OP group immediately after treatment, but no significant difference was seen thereafter. There were no differences between the groups in other inflammatory markers. Conclusions: This study indicated that EVAR was less invasive compared to an open abdominal surgery from the standpoint of assessing postoperative endotoxin activity (EA) levels measured by EAA.
Bacterial endotoxin or Endotoxin, a cellular structural component of gram negative organisms, is known to in- crease in the blood when perioperative sepsis or anastomotic insufficiency occurs after an intestinal surgery. This is known to be closely related to postoperative prognosis. However, elevation of plasma endotoxin levels is sometimes reported even when no remarkable infection has been detected [
Previously, open abdominal surgery has been performed as a general approach for the treatment of abdominal aortic aneurysm. However, recent development in endovascular aneurysm repair (EVAR) has rapidly expanded its clinical use, and its advantages such as minimal invasiveness, lower mortality rates, decrease in average ICU stay [
The purpose of this study is to analyze the minimal invasiveness of endovascular aneurysm repair from the viewpoint of blood endotoxin, to examine how this relates to the patient’s postoperative course, and to reveal the clinical significance of quantitative measurement of endotoxin by the EAA method.
Patients with abdominal aortic aneurysm who underwent either open abdominal surgery or endovascular aneu- rysm repair at Juntendo University Hospital were studied. Peripheral blood sample was used, and it was handled according to the Declaration of Helsinki. The study was approved by the Human Ethics Committee of Juntendo University. A written consent was signed by each patient prior to the surgery.
Patients treated for abdominal aortic aneurysm from April to December 2012 were divided into two groups. The first group underwent open abdominal surgery (OP), and the other group underwent endovascular aneurysm re- pair (SG). Cases were omitted if the patient received preoperative steroid treatment, the surgery combined mul- tiple procedures such as open heart surgery, or the patient had inflammatory diseases such as vasculitis. Pre- operative peripheral blood was taken to measure the baseline levels of endotoxin (Et), body temperature, white blood cell count (WBC), CRP, tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6). Among them, WBC and CRP were measured in central laboratory of Juntendo University, and TNF-α, IL-6 were measured by out- sourcing laboratory (SRL Inc, Tokyo). These values were also measured postoperatively until postoperative day 5 to calculate the rate of change. Patient information such as age, gender, BMI, medication, complications, pre- vious surgical history including procedure, device used, operative time, and postoperative course were recorded and compared between the two groups.
Spectral’s Endotoxin Activity Assay (EAA, Toray Medical Co. Ltd., Tokyo) was used for the measurement of whole blood endotoxin. The presence of endotoxin or lipopolysaccharide (LPS), an outer membrane component of gram-negative bacteria, can result in immune complex formation in the presence of a specific anti-LPS anti- body to yield complement fixation. Then, the opsonized zymosan primes neutrophils in the blood to trigger their oxidative burst.
A chemilumine scence assay was performed according to the manufacture’s instruction. Actual measurements were made of light emissions over a total period of 15 min in a tubeluminometer (Auto Lumat LB953, E.G. & G, Berthold, Wildbat, Germany) and quantitative analysis was completed within 2 hours of sample collection. The relative light units (RLU) measured by the instrument was converted by calculation into an endotoxin activity (EA) value.
Each measurement was recorded as average ± standard error. Comparison between the 2 groups was made using Statcel 3 software (OMS publishing Inc, Tokyo). Statistical significance was determined using the Student’s t-test, and P < 0.05 was considered significantly different. The comparison of the peak level of Et with preopera- tive value in each patient was analyzed by the paired t-test.
During the study period, 17 cases of abdominal aortic aneurysms were treated. Open abdominal surgeries (OP group) were performed in 9 of these cases, and endovascular aneurysm repairs (SG group) were performed in 8 cases. Patients with preoperative endotoxin (Et) above the low level cutoff value (0.4) were excluded from the study. The study was performed in 14 remaining cases, 7 cases in each group, which met none of the other ex- clusion criteria.
Preoperative patient background is shown in
. Baseline characteristics.
OP (n = 7) | SG (n = 7) | P Value | |
---|---|---|---|
Age, year | 70.6 ± 8.5 | 71.1 ± 7.3 | 0.89 |
Female (%) | 0 (0) | 3 (42.9) | 0.12 |
BMI, kg/m2 | 23.6 ± 2.7 | 25.7 ± 4.5 | 0.29 |
DM (%) | 1 (14.2) | 1 (14.2) | 1.00 |
HT (%) | 6 (85.7) | 4 (57.1) | 0.24 |
HL (%) | 5 (83.3) | 4 (57.1) | 0.58 |
Smoking history (%) | 6 (85.7) | 4 (57.1) | 0.24 |
Creatinine, mg/dL | 1.63 ± 0.89 | 0.73 ± 0.12 | 0.02 |
*BMI: body mass index, DM: diabetes mellitus, HT: hypertension, HL: hyperlipidemia, creatinine: serum creatinine.
. Preoperative values.
OP (n = 7) | SG (n = 7) | P Value | |
---|---|---|---|
Et | 0.17 ± 0.07 | 0.19 ± 0.06 | 0.47 |
WBC, ×103/µL | 6.4 ± 1.2 | 5.1 ± 1.5 | 0.29 |
Neutrophil, ×103/µL | 4.1 ± 0.8 | 3.1 ± 0.9 | 0.04 |
CRP, mg/dL | 0.36 ± 0.45 | 0.10 ± 0.06 | 0.16 |
TNF-α, pg/mL | 1.91 ± 1.27 | 1.39 ± 0.36 | 0.31 |
IL-6, pg/mL | 3.37 ± 2.99 | 2.71 ± 1.33 | 0.60 |
BT, Celsius degree | 36.4 ± 0.4 | 36.3 ± 0.5 | 0.64 |
*Et: endotoxin, BT: body temperature, WBC: white blood cells, CRP: C-reactive protein TNF-α: tumor necrosis factor-alpha, IL-6: interleukin-6.
. Surgical indices.
OP (n = 7) | SG (n = 7) | P Value | |
---|---|---|---|
Operation time, minutes | 327.4 ± 102.7 | 167.7 ± 100.7 | 0.01 |
Blood transfusion, % | 42.9 | 14.2 | 0.12 |
Aortic Clamp time, minutes | 119.4 ± 35.6 | N/A | N/A |
ICU stay, day | 1.4 ± 0.5 | 1.4 ± 1.1 | 1.00 |
After operation | 13.9 ± 4.5 | 8.0 ± 6.4 | 0.07 |
The peak level of EA in each patient was compared with the preoperative baseline (
WBC, neutrophil count, CRP, TNF-α, IL-6, and body temperature were measured as inflammatory markers (
In this study, perioperative whole blood endotoxin levels were measured sequentially using the EAA method. There have been many reports indicating correlations between blood EA level and clinical outcomes [
Endotoxin activity. The mean endotoxin ac- tivity (EA) value in OP and SG groups are shown as break line and solid line, respectively. The preopera- tive values in two groups were not statistically differ- ent from one another. The values decreased on the day of surgery in both groups. On the third day after sur- gery, the value was significantly higher in OP group compared to that of SG (P = 0.011)
Individual changes in endotoxin activity. The change in endotoxin activity (EA) values in each patient from preoperative baseline to the peak postoperative val- ue is shown. The change in the mean values of the 2 groups (thick line) represented a significantly larger in- crease in the OP group (P = 0.002) compared to that in the SG group (P = 0.035)
[
Previous reports indicate that high levels of postoperative endotoxin lead to prolonged ICU and hospital stay. However, there are few reports which track the change in post operative EA levels for up to five days after treatment. Klein et al. performed the sequential determinations of perioperative EA levels in patients who un- derwent open heart surgeries with cardiopulmonary bypass by using the EAA method, and concluded that high levels of endotoxin increase the risk of infection [
Changes in inflammation markers. Time course changes of other inflammation markers. Although WBC and neutrophil were significantly higher only on the day of sur- gery in OP, as for other markers, a statistical analysis did not show any significant dif- ferences between the groups during the study period (P < 0.05)
Contrastively, in our current study, endotoxin levels did not present significant increase until the first day of surgery in either group, but all cases in the OP group showed an increase until the third day of surgery. The en- dotoxin levels in three of these cases exceeded 0.4, the low level cutoff set by the MEDIC Study [
Intestinal handling is thought to be the reason behind the elevation of postoperative EA levels in the OP group. All cases in the OP group involved infrarenal aortic clamping, and there were no remarkable events in the intes- tinal blood supply from the celiac artery and the superior mesenteric artery. As in other general operative pro- cedures, surgical view was kept clear using devices such as a retractor. It has been previously suggested that in- testinal translocation could increase blood endotoxin [
Meanwhile, there were 3 cases with preoperative endotoxin levels of 0.4 or above which were excluded from the study. Of these cases, preoperative pneumonia and pulmonary metastasis were suspected in one case, and the other two did not display any evidence of infection though Buerger’s disease was present in one of them. Taking into account the MEDIC Study which reports endotoxin levels of 0.4 - 0.6 were seen in approximately 7% of healthy volunteers, there could be a problem of nonspecific elevations in three excluded cases, or there may be some clinical significance other than infection.
Another interesting result from this study was that observed elevations in blood endotoxin were not dependent on WBC count, CRP and inflammatory cytokine levels such as serum TNF-α or IL-6. Previous studies have pointed out that elevated endotoxin stimulates the production of inflammatory markers such as TNF-α, IL-1β, and IL-6 [
This study indicated that endovascular aneurysm repair was less invasive compared to open surgical repair from the aspect of perioperative EA levels. Furthermore, whole blood endotoxin activity levels measured using the EAA method were significantly elevated having no association with other inflammatory markers. This suggests that measurement of endotoxin activity by EAA method may become useful adjuncts to the clinician for the management of postoperative inflammation.
We thank Ms Yuko Kojima (Juntendo University, Graduate school) for her correcting English in this manu- script.