General anesthesia combined with modern volatile anesthetics for use in cardiac surgery correlated with fewer deaths and less postoperative pulmonary and other complications, when compared with total IV anesthesia (TIVA).
That was the finding from a literature review of 68 randomized controlled trials that included 7,104 patients. In noncardiac surgery, however, volatile anesthetics were not linked to lower rates of complications.
The review was conducted by the Pulmonary Engineering Group, a team of researchers from the Department of Anesthesiology and Intensive Care Medicine at the University Hospital Carl Gustav Carus, in Dresden, Germany. “We focus on experimental and clinical trials on organ protection, mainly those related to mechanical ventilation,” said Marcelo Gama de Abreu, MD, PhD, professor of anesthesiology and vice head of anesthesiology and intensive care medicine at the hospital.
“However, prevention of organ failure and preservation of organ function is not limited to mechanical ventilation. It is of paramount importance to notice that the choice of the anesthetic agent may have direct effects on organ function.”
Dr. Gama de Abreu, corresponding author of the literature review (Anesthesiology 2016;124:1230-1245), wondered whether the published evidence supported his impression. Before the present research, “a Bayesian meta-analysis by Landoni and colleagues had demonstrated reduced mortality with volatile anesthetics in patients undergoing cardiac surgery,” he said. “However, postoperative complications and noncardiac surgical patients had not been assessed. This was the motivation for conducting the project.”
For inclusion in the literature review, the studies needed to fulfill five criteria:
- adult patients undergoing general anesthesia for surgery;
- an intervention with a volatile anesthetic, either desflurane (Suprane, Baxter), isoflurane or sevoflurane;
- comparison of volatile anesthetics versus TIVA;
- reporting mortality as the primary outcome, along with postoperative pulmonary or other complications; and
- a randomized controlled trial study design.
The authors used a network meta-analysis model, which allows for indirect comparisons. “For example, treatment A is compared to treatment B (AB), and in another trial treatment A is compared to treatment C (AC),” Dr. Gama de Abreu said. “The model can also rule out associations between treatment B and C (BC), without the necessity of a trial with the comparison BC.”
The model was used to investigate whether desflurane, isoflurane or sevoflurane might be beneficial compared with the other volatile anesthetics or TIVA. “This data was enhanced by three trials, which investigated only volatile anesthetics without a TIVA control group,” Dr. Gama de Abreu said.
Reduced Pulmonary Complications
The investigators figured odds ratios (ORs) using the Peto OR (POR) method, which is considered accurate but may lead to bias when there are large treatment effects or when group sizes are highly divergent. For cardiac surgery, the POR was 0.55 for the association of volatile anesthetics with reduced mortality; the POR was 0.71 for pulmonary complications; and there was a POR 0.74 for other complications. For noncardiac surgery, however, volatile anesthetics did not correlate with any of the three variables, giving a POR of 1.31, 0.67 and 0.70, respectively.
“The reduction of postoperative pulmonary complications in cardiac surgery patients was a new finding,” Dr. Gama de Abreu said. “Up to now, we are not able to explain the underlying mechanism.”
The analysis also found that desflurane, isoflurane and sevoflurane, the volatile anesthetics investigated, demonstrated similar performances regarding organ protection.
As to why there were more favorable outcomes with volatile anesthetics, “we can only speculate that it is due to organ protection,” Dr. Gama de Abreu said. In the heart, these anesthetics possibly provide protection “against the effects of ischemia and reperfusion, but anti-inflammatory effects may also play a role here and in other organs.”
Based on the data, Dr. Gama de Abreu cannot make a general recommendation to use volatile anesthetics in all patients. Still, it appears, provided there is no contraindication, “patients undergoing cardiac surgery benefit from volatile anesthetics during the procedure,” he said. “This result is in accordance to other meta-analyses and the clinical experience.”
Among the limitations of the review and meta-analysis were that most trials were relatively small; publications dating back three decades were included, thus not accounting for advances in postoperative care that may have influenced the results; and the investigators did not account for the use of opioids, which might have provided cardiac protective effects.
Nonetheless, “our study indicates that the choice of the type of anesthesia may influence the outcome of surgery patients,” Dr. Gama de Abreu said. “However, high-quality randomized controlled trials investigating the impact of anesthetic regimens on outcome in noncardiac surgery are urgently needed. Our group is currently setting up such a trial.”