Results:
There were 4536(75.72%) males. Mean age of the study population was
57.50±8.53 years. Most common diagnosis was triple vessel disease
(n=4613, 77%). Mean numbers of grafts inserted were 3 ±0.83. LIMA was
used in 5972 patients (99.7%). Most common grafting strategy was
pedicle left internal mammary artery graft (LIMA) to left anterior
descending artery (LAD) and saphenous vein to other territory. Total
arterial revascularization in the form of LIMA (in situ, pedicle)-RIMA
(skeletonized) or LIMA (in situ, pedicle)-Radial ‘Y’ configuration was
performed in 620 (10.35%) patients. Emergency surgery was performed in
560 (9.34%) patients and coronary endarterectomy performed in 886
(14.8%) patients. Most common grafting strategy for endatrectomy vessel
was direct anastomosis (of LIMA or saphenous vein) followed by grafting
upon on lay patch of saphenous vein. Other demographic and preoperative
variables are shown in Table 1.
Out of 5990 off pump coronary bypass surgeries, total 132 (2.2%)
patients were re-explored. The most common cause of re-exploration was
bleeding (n=110, 83.33%) followed by cardiac tamponade (n=15, 11.36%)
and unspecified (n=5, 3.8%). The most common site of bleeding was from
graft/anastomosis (53.8%), followed by sternum including LIMA bed
(31.1%), others (10.6%, pacing wire site, thymus etc.) and none
(4.54%). Mean time to re-exploration was 9.75±8.65 hours (Median 5.5
hour, range 1-36 hour). Other intraoperative and postoperative variables
are shown in Table 2.
We found that pre-operative low platelet count (p=0.000), emergency
surgery (p=0.008), and number of grafts (p=0.000), were significant risk
factors for re-exploration on univariate as well as multivariable
analysis(F (4,594)=27.72, p=0.000, R2 =0.497) while
age, sex, body surface area, diabetes, hypertension, peripheral vascular
disease, pre-operative hemoglobin, pre-operative prothrombin time,
pre-operative serum creatinine as well as serum bilirubin, pre-operative
ejection fraction, total arterial revascularization, LIMA use and
endarterectomy were not found risk factors for re-exploration after
OPCABG (p>0.05,Table 3,4). Patient who re-explored had
significantly increase morbidity in the form of increase drain output
(p=0.00), number of blood product transfusion (p=0.00), more ICU stay
(p=0.00), more ventilation time (p=0.00), more IABP use
(p<0.001), renal dysfunction (p=0.002), deep sternal wound
infection (p<0.001) and hospital stay (p=0.00).
30- Day mortality in the study population was 1.41%. 30-day mortality
was significantly more in patient who underwent re-exploration (13.63 %
vs 1.14%, p=0.000). The most common cause of the death was sepsis
(66.6%) with multi organ dysfunction followed by low cardiac output
syndrome. On multiple regression analysis (Table 4), preoperative
platelet count, emergency surgery, euroscore II, number of grafts,
preoperative ejection fraction, postoperative serum bilirubin and
creatinine, no of blood products used, re-exploration and time to
re-exploration found to be an independent risk factor for mortality
(F(28,3076)=40.54,R2=0.519, p=0.000 for model fit) while age, sex, body
surface area, previous MI, diabetes, hypertension, chronic obstructive
pulmonary disease, preoperative prothrombin time , preoperative serum
bilirubin, preoperative serum creatinine, total arterial coronary bypass
grafting, presence of atrial fibrillation and performing coronary
endarterectomies were not found statistically significant factors for
mortality.
We analyzed effect of time delay on re-exploration because on multiple
regression analysis B coefficient was highest for time to
re-exploration. On receiver operating curve analysis, we found that the
optimum cut off for time to re-exploration was of 14 hours with
sensitivity 81.3% and specificity of 80% and AUC of 0.798 (figure 1).
As shown in Table 5, while comparing groups of patients who underwent
re-exploration early (time to re-exploration after completion of primary
operation <14 hour as per cut-off) and delayed, later group
had significantly high mortality (30.55% vs 7.29%, p=0.000), higher
drain output (995.54±380.2 vs 1458.16±543.20, p=0.00), higher number of
blood products received (11.14±11.89 vs 23.69±10.09, p=0.000), more
frequently underwent coronary endarterectomy (6 vs12, p=0.000), higher
incidence of tamponade (3 vs 12, p=0.000), higher ventilation time
(13.05± 6.39 vs 41.10±81.08) and high ICU stay (5.03±3.74 vs 8.53±6.03,
p=0.02).