Diabetes linked to poorer outcomes after cardiac surgery
Individuals with diabetes who undergo cardiac surgery are at an elevated risk of postoperative hyperglycaemia, infection, and renal outcomes, according to a study from Singapore.
The study population comprised 2,831 adults (mean age 59.4 years, 19.9 percent female) who had undergone elective cardiac surgery between 2008 and 2010, of whom 46.7 percent (n=1,321) had diabetes (history of diabetes, taking antidiabetic medications, pre-operative random plasma glucose level of >200 mg/dL, or HbA1c >6.5 percent).
At baseline, mean HbA1c level of the overall population was 11.3 percent, 75.3 percent had hypertension*, 12.5 percent had renal impairment, and 74.6, 80.4, and 48.6 percent were on beta blockers, statins, and ACE** inhibitors, respectively. Outcomes following cardiac surgery were assessed up to 30 days post-surgery.
Compared with those without diabetes, individuals with diabetes were older (mean age 60.6 vs 58.3 years) and more obese (mean BMI 25.4 vs 24.5 kg/m2), and were more likely to have hypertension (88.5 percent vs 63.8 percent), renal impairment (16.9 percent vs 8.6 percent), and left ventricular ejection fraction <30 percent (11.0 percent vs 6.2 percent; p<0.001 for all).
Following cardiac surgery, more individuals with diabetes developed postoperative hyperglycaemia, defined as a blood glucose level >10 mmol/L during the first 48 hours post-surgery (88.3 percent vs 56.0 percent; p<0.001), and postoperative infection (2.8 percent vs 1.3 percent; p=0.005) than those without diabetes. [Diab Vasc Dis Res 2019;doi:10.1177/1479164119866380]
More individuals with diabetes developed acute kidney injury (AKI) following cardiac surgery than those without diabetes (36.4 percent vs 25.6 percent; p<0.001) and required new initiation of dialysis (4.9 percent vs 2.1 percent; p<0.001). Patients with diabetes were also more likely to require ICU readmission (6.0 percent vs 3.4 percent; p=0.001) and have a longer stay in the hospital (mean 12.5 vs 10.7 days; p<0.001) and in the ICU (mean 52.6 vs 43.1 days; p=0.017).
Multivariate analysis demonstrated that individuals with diabetes had an elevated risk of developing postoperative hyperglycaemia (odds ratio [OR], 6.00, 95 percent confidence interval [CI], 4.893–7.348; p<0.001) and postoperative infection (OR, 1.73, 95 percent CI, 1.003–2.976; p=0.049). They were also at an elevated risk of initiating new dialysis (OR, 1.71, 95 percent CI, 1.086–5.360; p=0.021), developing AKI (OR, 1.36, 95 percent CI, 1.137–1.626; p=0.001), and requiring ICU readmission (OR, 1.70, 95 percent CI, 1.171–2.480; p=0.005).
Among patients with diabetes, the postoperative outcomes were dependent on antidiabetic agents. Compared with those on oral hypoglycaemic agents only, those on insulin were more likely to develop postoperative hypoglycaemia (93.4 percent vs 87.0 percent), AKI (49.0 percent vs 36.3 percent), initiate dialysis (10.2 percent vs 3.7 percent), and have a longer duration of hospitalization (p<0.001 for all). ICU-related mortality was also higher among those on insulin compared with oral antidiabetic agents (3.1 percent vs 0.9 percent; p=0.006). This result could be due to poorer diabetes control and more diabetes-related complications among patients on insulin, said the researchers.
According to the researchers, postoperative hyperglycaemia could weaken immune function and inflammatory responses, potentially worsening infections, and could also contribute to micro- and macrovascular complications, as well as cardiovascular-related mortality.
“The poorer renal outcomes … are likely because patients with diabetes undergoing cardiac surgery have a greater inflammatory and oxidative stress response with significantly higher levels of cortisol, hsCRP, interleukin-6, and oxidative stress markers during the postoperative period, which is in turn associated with renal damage and poorer postoperative renal outcomes,” they added.
All in all, the researchers suggested that patients with diabetes undergoing cardiac surgery receive “special attention” following surgery in order to prevent these negative outcomes.