Anesthesiology News · September 18, 2017
In a selected cohort of patients undergoing total hip arthroplasty, the use of hypotensive epidural anesthesia led to very low rates of transfusion and few cerebral oxygen desaturation events, according to a recent study. When used in healthy patients, this technique could lower intraoperative blood loss without compromising patient safety, the authors reported.
“None of our patients had evidence of new cognitive dysfunction at discharge,” said Sean Garvin, MD, assistant attending anesthesiologist at the Hospital for Special Surgery and clinical assistant professor of anesthesiology at Weill Cornell Medical College, in New York City. “For healthy patients, it’s definitely worthwhile to consider this technique, but more data—particularly in higher-risk patients—would be useful.”
Topic Is Controversial
According to Dr. Garvin, the relationship between cerebral oxygen saturation and blood pressure during hypotensive epidural anesthesia is controversial. Although studies have suggested an increased risk for kidney injury, myocardial injury and mortality in patients with mean arterial pressures less than 55 mm Hg for prolonged periods, a separate analysis showed no association between mean arterial pressures less than 70 mm Hg and stroke (Anesthesiology 2013;119:507-515; Anesth Analg 2016;123:933-939). Moreover, according to Dr. Garvin, there are no data for patients undergoing total hip replacement with hypotensive epidural anesthesia and cerebral oximetry.
Based on research by Sharrock et al, which showed the preservation of cerebral blood flow velocity during hypotensive epidural anesthesia (Anesth Analg 2016;122:226-233), Dr. Garvin and his colleagues hypothesized that cerebral desaturation events would not be associated with hypotensive epidural anesthesia in total hip replacement patients.
Following IRB approval, the researchers enrolled 100 patients undergoing unilateral total hip arthroplasty at the Hospital for Special Surgery. In the operating room, patients received a combined spinal epidural with bupivacaine to induce hypotension, and epinephrine infusions were used to maintain mean arterial pressure between 55 and 65 mm Hg. Patients with preoperative baseline systolic blood pressure greater than 150 mm Hg were excluded from the study.
Cerebral oxygen saturation was recorded with a near-infrared spectroscopy device, and cardiac output was measured noninvasively, said Dr. Garvin, who noted that investigators were blinded to these data.
The study’s primary end point was the incidence of intraoperative cerebral desaturation events, defined as a greater than 20% reduction from baseline and/or cerebral oxygen saturation less than 50%. Secondary end points included postoperative delirium evaluated via the Confusion Assessment Method (CAM) and postoperative cognitive dysfunction evaluated via the Mini-Cog test. Investigators administered these tests at baseline and postoperatively on days 0, 1 and 2.
Low Incidence of Adverse Effects in Low-Risk Patients
As Dr. Garvin reported at the 2017 annual spring meeting of the American Society of Regional Anesthesia and Pain Medicine (abstract 3196), four patients out of 100 experienced a cerebral desaturation event. Of these four patients, Dr. Garvin said, only one had a desaturation lasting longer than 15 seconds.
In terms of postoperative cognitive dysfunction, seven patients were diagnosed with cognitive changes via Mini-Cog. However, two of these patients had abnormal results at baseline, and only one of the seven patients had a cerebral oxygen desaturation event, which normalized on postoperative day 2, Dr. Garvin reported.
Finally, no strokes or delirium were diagnosed, and all patients demonstrated adequate hypotension in terms of the target goal. The average mean arterial pressure was maintained intraoperatively within the 55 to 65 mm Hg goal. Mean arterial pressure during hypotensive epidural anesthesia was not associated with a cerebral desaturation event, said Dr. Garvin, who speculated that preservation of oxygen delivery with epinephrine infusion might explain these results.
According to the researchers, these findings are consistent with earlier studies showing preserved cerebral blood flow velocity and low incidence of cognitive dysfunction and delirium following hypotensive epidural anesthesia. Because this study was limited to lower-risk patients, however, further research is needed to assess the safety of this technique in patients at higher risk for ischemic events.
“There are emerging technologies that enable individual assessment of cerebral autoregulation, which allows for tailored preoperative care,” Dr. Garvin said. “Future study is warranted in higher-risk patients to see if we can balance the benefits of relative hypotension while maintaining oxygen delivery.”
Oscar de Leon-Casasola, MD, professor of anesthesiology at the School of Medicine and Biomedical Sciences, State University of New York at Buffalo, asked whether blood loss was monitored for each patient.
“Estimated blood loss is definitely something that we consider with our patients when we do hypotensive epidural anesthesia, but we’re not losing a lot of blood,” Dr. Garvin said. “The average blood loss is probably about 100 cc to 200 cc for those patients, and transfusion rates are less than 5%. The published literature, on the other hand, is 20% to 30%, and some of the recent literature for ambulatory hip replacements have shown up to 70% of patients getting a transfusion and then going home.”
Dr. Garvin concluded, “In this setting, providers may want to consider this technique in healthy patients to save them a blood transfusion.”