A 68-year-old retired physician who has coronary artery disease is seen in the preoperative clinic before his scheduled coronary artery bypass graft. He asks about options for pain control, including nerve blocks and neuraxial techniques. According to a recent systematic review and meta-analysis, compared with general anesthesia, the use of thoracic epidurals in cardiac surgery was MOST likely associated with which of the following outcomes?
- □ (A) Shorter time to extubation
- □ (B) Lower mortality
- □ (C) More epidural hematomas
The study authors searched for randomized controlled trials that compared patients who received thoracic epidural analgesia for cardiac surgery and those who did not receive an epidural. The primary outcomes of the meta-analysis were intensive care unit (ICU) length of stay, hospital length of stay, time to extubation, and mortality. Secondary outcomes were pain scores, blood transfusion requirements, and rates of postoperative pulmonary, neurological, and cardiac complications.
A total of 51 randomized controlled trials comparing thoracic epidural analgesia versus no epidural were included in the final analysis (total patients, N = 4,332; epidural patients, n = 2,112; general anesthesia-only patients, n = 2,220). Of these studies, 43 were focused only on patients undergoing coronary artery bypass graft (CABG) procedures, while eight studies included valve replacement surgery and combined CABG and valve surgeries. Baseline patient characteristics such as pooled age, body mass index, and left ventricular ejection fraction were similar between the groups.
Upon performing a meta-analysis of these studies, the authors found a shorter length of ICU stay associated with the use of thoracic epidurals compared with general anesthesia (–6.9 hours; 95% CI, –12.5 to –1.2 hours; n = 879 vs. 885 patients, respectively; 16 studies). They also found a shorter length of hospital stay with thoracic epidural analgesia versus general anesthesia (–0.8 days; 95% CI, –1.1 to –0.4 days; n = 1,105 vs. 1,141 patients, respectively; 20 studies). The authors also found shorter extubation time with thoracic epidurals compared with general anesthesia (–2.9 hours; 95% CI, –3.7 to –2.0; n = 1,459 vs. 1,525 patients, respectively; 32 studies). However, in-hospital mortality was not found to be different between the groups, based on 18 studies.
The meta-analysis also showed important reductions in each of the secondary outcomes, including transfusion requirements, pain scores at rest at 24 hours, delirium, arrhythmias, and pooled pulmonary complications, in patients who received thoracic epidural analgesia. There were no epidural hematomas reported in any of the 51 studies that were included in the analysis (2,112 pooled patients who received thoracic epidurals).
In addition to the meta-analysis, the authors employed a relatively new statistical method called trial sequential analysis (TSA) to analyze the existing studies on thoracic epidural analgesia. TSA is a statistical analysis of meta-analytic data that aims to reduce the rates of false-positive and false-negative results. It can also determine whether an effect size is large enough such that it will not be affected by future studies. In this study, the authors performed a TSA of the primary outcomes and found that the results were consistent with the results of the conventional meta-analysis. The strongest primary finding, where the required information size threshold was met, was the time to extubation. The primary outcomes of ICU length of stay and hospital length of stay did not meet the required information size, but the cumulative z-score crossed the set boundary for benefit. Regarding the association of thoracic epidural analgesia and mortality, the TSA of the existing studies indicated that further randomized studies would be required to determine whether thoracic epidural analgesia is associated with benefit or harm.
In summary, a recent meta-analysis demonstrated that the use of thoracic epidural analgesia in cardiac surgery patients was associated with benefits such as shorter ICU length of stay, shorter hospital length of stay, and shorter time to extubation. No epidural hematomas were reported among more than 2,000 patients who received a thoracic epidural for cardiac surgery. Further studies are needed to conclusively determine the effect of epidural analgesia on mortality in this patient population.