Discussion :
Post-operative hemorrhage requiring re-exploration after cardiac surgery
still remains a troublesome complication with an incidence of 15% in
the early days of cardiac surgery to 2-6% now a days (5, 6, 9, 10,16).
There are many factors for reduction of the incidence of the
re-exploration as well as blood transfusion out of which one of the
factor is performing ‘off – pump CABG’ (OPCABG) for revascularization
(12- 14). However, need for re-exploration was not totally alleviated by
using off pump coronary artery revascularization strategies and there is
still lake of data regarding incidence, risk factors and effect of
timing of re-exploration after OPCABG
The overall incidence of re-exploration in our cohort was 2.2% with
most common site of the bleeding was graft branch/anastomosis (53.8%).
Karthik et al. and choong et al. (9,10) also reported similar findings
using on-pump CABG strategy predominantly . Thus we can conclude that
whether we performed CABG with or without CPB, most common site of the
bleeding is from graft/anastomosis. They also reported incidence of
diffuse ooze of around 25% while the same was 4.5% in our study. We
believe that avoidance of CPB in our cohort is responsible for this
findings highlighting another advantage of OPCABG over on-pump CABG.
We observed that emergency surgery, low platelet count as well as
presence of thrombocytopenia and number of distal anastomosis, were
found to be an independent factor for the re-exploration. Emergency
surgery has been well documented as a cause for re-exploration and
mortality (10,17). One would expect this finding as they had received
either loading doses of anti-aggregation therapy and/or continued use of
dual antiplatelet, letting them more prone for bleeding. The influence
of low preoperative platelet count on post-cardiac surgery bleeding is
also well documented in literature (18,19). Recently, one of the study,
demonstrated that preoperative thrombocytopenia is associated with
increased postoperative blood loos as well as increased risk of severe-
massive bleeding after CABG (19). However, in this study, only 20% of
patients underwent off pump CABG. On would easily assume that presence
of thrombocytopenia will aggravate the effects of CPB on homeostasis and
platelet dysfunction leading to increased risk of bleeding. However,
this finding may not be applicable who are not exposed to deleterious
effects of CPB. Rannuci. M et al showed that the platelet function
linearly associated with platelet count (20). This explains association
of platelet count with bleeding in patients undergoing OPCABG. We also
found that more number of distal anastomosis was independently
associated with re-exploration as documented by many authors ( 10,16).
This association can be explained by the finding that most common site
of bleeding after CABG is from graft/anastomosis. Thus doing more number
of grafts exposes more number of potential bleeding sites and increase
the risk of bleeding.
The reported mortality of the patients undergoing re-exploration has
been high in the range of 5.7 to 15.8% (3-8). In our cohort reported
mortality was 13.6%. Emergency surgery and higher euroscore are well
documented cause of mortality after cardiac surgery (9,17). One would
expect this finding as these patients are generally sicker with unstable
hemodynamics. Thrombocytopenia has been well documented as a risk factor
for mortality in critically ill patient (21), but limited studies are
available for post- cardiac surgery patients, however even these studies
have documented thrombocytopenia as a bad prognostication factor as
shown by us (22,23). We previously showed that hyperbilirubinemia after
cardiac surgery was known to increase mortality (24). Recent report
suggests that once developed, it was associated with increased mortality
irrespective of types of surgery (25).
Many authors have also found that re-exploration itself is an
independent risk factor for mortality (8, 9, 26). We have also seen that
it independently increases the risk of mortality. Time after
re-exploration has recently gained attention due to various authors
reported poor outcome of the patients who underwent re-exploration late
(>12 hour) after cardiac surgery. We also observed similar
findings in our study cohort. However, we have found that the optimum
cut off value for re-exploration was 14 hour with AUC of around 0.8. On
further analysis of these subgroup, we have found that patient who
explored early (time to re-exploration after completion of primary
operation <14 hour) had less mortality rate (7.3% vs
30.55%).Similar finding have been documented by others (9,10). Also
incidence of endarterectomies, cardiac tamponade and drain output was
more in the patients who explored late (>14 hour) as
compared to the patients who explored early. We routinely under
corrected the heparin with protamine in a patient who underwent
endarterectomies. This leads to continuous small amount of bleeding over
the time requiring continuous transfusion of the blood products and
delaying the re-exploration (as it failed to reach defined criteria).
These small amount of blood often clots around heart especially around
right atrium causing cardiac tamponade like feature leading to
re-exploration. So we think that under-correction of heparin after
OPCABG is a double-edged sword and it should be use very judiciously.
Blood transfusion after cardiac surgery has been found to be independent
risk factor for mortality (6, 9, 10, 27) as well as post-operative
infections. Murphy et al had also reported dose dependent relationship
of blood products use with mortality and morbidity (27). We have
observed that in patient who re-explored late receive more blood product
as compared to patient who re-explored early. This probably also
explained higher mortality in a patient who re-explored late.
We have also observed significantly less incidence of re-exploration in
patients who underwent minimally invasive CABG (MIDCABG). MIDCABG as
well as hybrid approach has been associated with less surgical trauma,
less need for blood transfusion, less incidence of surgical site trauma,
shorter hospital stay and faster recovery in carefully selected patients
(28, 29). So one of the approach to decrease incidence of re-exploration
is performing minimally invasive or hybrid surgery in appropriate
patient.