San Francisco—Although general anesthesia and conscious sedation seem to equally affect functional independence at discharge in patients with acute ischemic stroke undergoing endovascular intervention therapy, patients who received general anesthesia experienced significantly greater mortality than their counterparts, researchers have found.

Whether this difference is directly attributable to anesthesia type, however, is unclear, as the duration of intra-arterial therapy and time to revascularization from symptom onset were both significantly longer in patients who received general anesthesia, according to the study.

“Ischemic stroke has an extremely high mortality rate—16%—in patients presenting for first-time stroke,” said Kathryn Rosenblatt, MD, an anesthesiology resident at SUNY Upstate Medical University, in Syracuse, N.Y., who helped conduct the study. “Endovascular clot retrieval helps remove intracranial clot occlusions in ischemic stroke patients. Although the therapy can be performed under moderate conscious sedation or general anesthesia, the effect of general anesthesia on clinical outcomes has remained controversial.”

In previous work, Jumaa and colleagues reported that general anesthesia resulted in favorable clinical and radiographic outcomes compared with local anesthesia (Stroke 2010;41:1180-1184). However, three recent retrospective studies have suggested that general anesthesia might worsen neurologic outcome and increase mortality in these patients (Stroke 2010;41:1175-1179; J Neurointerv Surg 2010;2:67-70; Anesthesiology 2012;116:244-245).

To help identify the relationship between type of anesthesia and outcome, senior investigator Fenghua Li, MD, associate professor of anesthesiology and associate director of neuroanesthesia at SUNY Upstate, and his colleagues studied the records of 109 patients, each of whom underwent endovascular therapy between December 2006 and October 2012. Thirty-five patients received general anesthesia; 74 received conscious sedation.

The two groups were similar with respect to patient characteristics and clinical conditions on admission, according to the researchers. Patients who required intubation on arrival for surgery were more likely to receive general anesthesia, Dr. Li noted. Duration of intra-arterial therapy and time to revascularization from symptom onset were significantly longer in patients who received general anesthesia (2.1±1.1 versus 1.4±0.7 hours, and 7.1±2.2 versus 6.0±2.0 hours, respectively).

Mortality also was significantly higher in patients who received general anesthesia (40% vs. 22%; P<0.05). However, the method of anesthesia did not have a significant effect on patients’ functional independence at discharge, the researchers reported.

A regression analysis demonstrated that two of the significant predictors for mortality in the model were anesthesia type (odds ratio [OR], 2.692; 95% confidence interval [CI], 1.036-6.996; P=0.042) and post-procedure glucose level (OR, 1.014, 95% CI, 1.003-1.024; P=0.011; respectively). “A larger sample size is needed to determine with statistical certainty that the relationship between general anesthesia and mortality is independent of the ability to maintain a patent airway upon admission and the stroke size, location and severity,” Dr. Rosenblatt said.

“This study is very similar to a couple other retrospective studies that showed that general anesthesia did predict worse outcomes,” she added. “We also saw that if you survive the hospitalization, your functional independence level at discharge was no different between general anesthesia and conscious sedation. The reason for this remains unclear, since it would be expected that the longer procedure time and time to revascularization in the general anesthesia group would have resulted in more extensive injury, as every minute after ischemic stroke results in the loss of almost 2 million neurons.”

Hilary P. Grocott, MD, professor of anesthesia and surgery at the University of Manitoba in Winnipeg, Canada, called the research “interesting” but said it suffers the limitations of most retrospective studies. “Unaccounted-for confounders are always a concern with studies with relatively low patient numbers. Specifically, those patients requiring general anesthesia may have had a poorer preoperative neurologic condition that itself may have led to the higher mortality rate,” Dr. Grocott told Anesthesiology News. “Alternatively, general anesthesia may have had an impact on blood pressure, with inadequately treated hypotension resulting in worse neurologic outcome—and subsequent death—in some patients. Although functional outcome in the survivors was not affected by anesthesia, these results warrant further study as to the factors that led to the higher mortality signal with general anesthesia.”

The researchers reported their findings at the 2013 annual meeting of the American Society of Anesthesiologists (abstract 1076).