To the Editor:
We read with great interest the article by Klinger et al.1 regarding the effect of intravenous lidocaine on neurologic outcomes after cardiac surgery. We appreciate and congratulate the authors for setting up a clearly structured randomized trial with a large sample size and sharing such useful findings. There are, however, two important points of concern.
First, patients with hypertension are believed to be more susceptible to cerebral hypoperfusion resulting from inappropriate blood pressure and impaired autoregulation of cerebral blood flow while underdoing cardiac surgeries, and cerebral hypoperfusion has been considered an important risk factor contributing to postoperative cognitive dysfunction.2 In this trial, participants with hypertension made up a sizeable proportion (59% in lidocaine group vs. 61.2% in placebo group; P = 0.268) of the overall population, the authors used the common practice of maintaining mean arterial pressure from 50 to 80 mmHg through cardiopulmonary bypass, but it was not mentioned whether there were differences in the mean arterial pressures, the durations of intraoperative hypotension, the durations of cerebral desaturation, or any other data that could suggest cerebral perfusion between the two groups.
Second, some variables that might influence the occurrence of postoperative cognitive dysfunction were not mentioned in the study. Such confounding variables include the occurrences of stroke, cardiovascular or cerebrovascular events after cardiac surgery,3 anesthesia duration, dosage of anesthetic agents, depth of anesthesia,4 and rewarming rate.5
The authors declare no competing interests.