Response to Letter Regarding Article, “Type of Anesthesia and Differences in Clinical Outcome After Intra-Arterial Treatment for Ischemic Stroke”
First, we would like to highlight that our study is not a post hoc analysis of the Multicenter Randomized Clinical Trial of Endovascular treatment for acute ischemic stroke in the Netherlands (MR CLEAN).3,4 As described in our article, the population of our study consists of patients from the so-called pretrial cohort, which concerns all consecutive patients with acute ischemic stroke treated with intra-arterial therapy in 16 stroke centers in The Netherlands before the start of the MR CLEAN trial. Information concerning procedures and treated patients was gathered to assess pretrial experience in centers that were committed to participate in the MR CLEAN trial.
Unfortunately, in this study, we do not have any information on the time from onset of the procedure to the time of reperfusion. As a result, we could not investigate whether general anesthesia (GA) may have ultimately decreased time to reperfusion as a result of improved procedural conditions. However, we do have these important data in a post hoc analysis on GA in the MR CLEAN trial itself. Results were presented at the International Stroke Conference 2015 in Nashville, TX, and will soon be published in print. In short, these results showed only a minor difference (not statistically significant) in time to reperfusion between the groups in the advantage of non-GA.
Campbell and Short1 comment in their letter that they missed an additional analysis whether the difference in time of 20 minutes between both treatment groups accounted for the difference in clinical outcome. In our analysis, we planned to only adjust for prespecified variables (age, stroke severity, occlusion of the internal carotid artery terminus, previous stroke, atrial fibrillation, and diabetes mellitus). However, when adjusting for time to start symptoms to start of intra-arterial therapy in minutes in the multivariable regression analysis, it does not change the direction of the odds ratio for a good clinical outcome for non-GA. Furthermore, we think that timing could be an important part of the anesthetic treatment itself and, in this study, is therefore not a separate variable.
Another important remark in the letter by Campbell and Short1 is the fact that data on physiological parameters and anesthetic drugs are missing. In addition, detailed descriptions of the anesthetic management, including airway and ventilation management, are also missing. We agree that this is vital information, which needs to be studied in future studies to explain the results of our study. However, our study was not designed to investigate the explanatory factors and possible underlying mechanisms that might explain worse outcomes under general anesthesia. Therefore, we did not collect this information, which was also described in our discussion.
In the letter by Klei and Dieleman,2 the authors point out the fact that 7 patients in the GA group (n=70) of our study received GA as a result of their clinical status before the start of the procedure (agitation, respiratory insufficiency, or decreased level of consciousness) and were wondering whether these patients caused confounding by indication. This might have been true; however, when leaving these 7 patients out of the primary analysis, the point estimate remains in the same direction with, as expected because of smaller group size, loss of statistical power (adjusted odds ratio, 1.7; 95% confidence interval, 0.75–3.88).
Furthermore, they state that there may be an important center effect. Although we completely agree that the design of this nonrandomized retrospective study introduces all kinds of important forms of bias (one of them being the center bias), our results are in line with the increasing evidence that a non-GA approach during intra-arterial therapy for acute ischemic stroke is beneficial in comparison with GA.5,6 We therefore think that the ongoing randomized control trial’s randomizing between GA and non-GA are much needed to clarify whether the beneficial effect of non-GA is caused by the anesthetic approach itself or other important confounding factors.
Lucie A. van den Berg, MD
Yvo B.W.E.M. Roos, MD, PhD
Department of Neurology of the Academic Medical Center
Stroke welcomes Letters to the Editor and will publish them, if suitable, as space permits. Letters must reference a Stroke published-ahead-of-print article or an article printed within the past 3 weeks. The maximum length is 750 words including no more than 5 references and 3 authors. Please submit letters typed double-spaced. Letters may be shortened or edited.
- © 2015 American Heart Association, Inc.
- Campbell D,
- Short T.
- van Klei W,
- Dieleman J.
- Fransen PS,
- Beumer D,
- Berkhemer OA,
- van den Berg LA,
- Lingsma H,
- van der Lugt A,
- et al
- McDonald JS,
- Brinjikji W,
- Rabinstein AA,
- Cloft HJ,
- Lanzino G,
- Kallmes DF.