Discussion
In this analysis, KPTx was associated with a 3.5-fold higher occurrence
of any complication following CABG, and even higher after emergency CABG
(OR 3.707, p<0.01). Previous literature has shown that
transplant patients undergoing cardiac procedures may experience higher
complication rates compared to the general
population7,19,20. Each transplant group in this study
carried a significantly higher Elixhauser comorbidity index score
(calculated by preexisting comorbidities) compared to Non-Tx, which may
reflect an increased baseline risk. However, it has also been
demonstrated that transplant recipients have comparable mortality and
long-term survival to non-transplanted
individuals3,20,21. It remains critical to investigate
surgical complications and risk factors in this unique population to
establish preventative measures and comprehensive management protocols.
Emergency surgeries in transplant patients have been associated with
worse surgical outcomes3,6,22,23. Non-elective surgery
has been identified as a risk factor for major postoperative morbidity
and mortality, including decline in renal function3,6.
Emergency abdominal surgery in solid organ transplant is associated with
up to 32.7% morbidity and 17.5% mortality22,
findings significantly higher than the general population. This
association is likely explained by greater case complexity, greater
incidence of complication, or immunosuppressive regimens that predispose
to certain issues, such as infections5,23.
Compared to the non-transplant population, KPTx had the highest
complication following CABG (78.3% vs. 47.8%). Cardiovascular issues
occurred evenly among all groups regardless of transplant status.
However, rates of respiratory complications were significantly higher
among transplant patients, with the highest in KPTx (8.0%). After
excluding renal dysfunction, John et al. demonstrated that most
transplant recipients required ventilatory support after cardiac surgery
(11.4%)3. Pulmonary morbidity after cardiac surgery
is common regardless of transplant status, including pleural effusions,
pneumonia, and atelectasis. Transplant recipients may be at increased
risk for pulmonary issues due to chronic immunosuppression, as well as
changes in pulmonary compliance from pre-transplant fluid overload of
ESRD24.
The incidence of SIRS was increased in all transplant recipients, with
significantly higher rates in PTx (8.0%). Following cardiac surgery,
rates of major infection in the transplant population may be as high as
19%20. Transplant recipients face a unique
post-operative infection burden due to lifelong immunosuppression. These
regimens downregulate inflammatory mediators, impair T-cell activation,
and interfere with critical phases of wound healing25.
Sirolimus may predispose to wound complications, including deep
infections, cellulitis, and fascial dehiscence26.
Likewise, chronic corticosteroid use is associated with a 2 to 5-fold
increase in wound complications rates when compared to those not taking
steroids27. However, we were unable to evaluate the
risk in specific treatment regimens as the NIS database does not provide
this detail.
Acute renal failure was a significant complication in all transplant
groups following CABG. PTx had the highest risk of acute renal failure
(40.7%), followed by KTx (35.7%), and KPTx (26.7%). Cardiopulmonary
bypass itself may pose a risk of kidney injury due to hypoperfusion or
inflammatory reactions inherent to the bypass
mechanism28. Postoperative kidney dysfunction appears
to be significantly more common in transplant patients after cardiac
surgery3. Elevated preoperative serum creatinine (SCr
>2 mg/dL) confers a higher risk and predisposes to
postoperative kidney failure3,6. Transplant recipients
may be at even greater risk from the nephrotoxic maintenance
immunosuppressive regimens which lower baseline GFR. Off-pump surgery
(beating heart surgery) has demonstrated fewer postoperative kidney
complications and may show promise in transplant
patients28. Larger studies are needed to evaluate
whether this approach should be preferred.
Transplant recipients required more blood products than their Non-Tx
counterparts, which may have further impacted their risk of
complication. Perioperative red blood cell (RBC) transfusion increases
the risk of AKI after cardiac surgery 29,30. This may
be the result of impaired oxygen handling by transfused RBCs, or faster
breakdown causing more iron release and oxidative
stress29,30. Additionally, blood transfusions pose a
unique risk in the transplanted population. RBC transfusions increase
HLA sensitization and antibody response which can increase the risk of
future graft failure31. Sensitization can occur after
a single transfusion, and nearly one-third of patients have already
received a transfusion before being added to the transplant
list31. Overly aggressive blood transfusions may
increase the risk of perioperative AKI, future graft rejection, and
render subsequent re-transplantation more difficult from the presence of
reactive antibodies.
Rates of perioperative mortality in transplant patients have ranged from
1.4% to as high as 15.7%3,32. While there was no
in-hospital mortality to analyze PTx and KPTx, the rate of KTx mortality
in this report (3.9%) was similar to that of other
reviews33. Three- and five-year survival rates in
kidney transplants after CABG ranged from 70% and 66%,
respectively6,34, to as high as 85% for 5-year
survival35. Importantly, although KPTx carried the
greatest rate of complication, this did not influence in-hospital
mortality. However, the data is unable to show how long-term survival is
affected as a result.
We identified greater total hospital charge and LOS in transplant
recipients on the univariate analysis. PTx had greatest median total
charge overall ($276,012) and longer LOS following CABG (14 days in PTx
vs. 8 days in Non-Tx). However, in the adjusted outcomes, LOS and total
hospital charge were not increased in transplant recipients, despite
being more likely to suffer a complication. Further analysis of pancreas
transplant recipient surgical costs is needed to reconcile these
conflicting results.
Our findings demonstrated increased risk in both non-transplant and
transplant centers. It is unclear whether transplant centers provide
superior care. Most surgeons believe care is better at transplant
centers and recommend acute surgery be performed at these
facilities36. However, in transplant recipients
undergoing abdominal surgeries, DiBrito et al. found no statistically
significant difference in complication rates at transplant centers vs.
non-transplant centers37,38. Although we found
increased in-hospital mortality in KTx at transplant centers, this was
likely skewed by a greater proportion of deaths at these centers, as the
overall mortality rate was 3.9% (or 106 out of 2678 patients).