The risk for neurologic injury associated with regional anesthesia is very low, but there are steps that anesthesiologists can take to further reduce that risk, according to anesthesiologists who spoke at the International Symposium of Ultrasound for Regional Anesthesia, Pain Medicine & Perioperative Applications.
“What we do is very safe, but this allows us to spend a lot of time talking about the optimal way to make things even safer,” Kyle Kirkham, MD, FRCPC, staff anesthesiologist at Toronto Western Hospital, University Health Network, and assistant professor, Department of Anesthesia, University of Toronto, Ontario, Canada, said.
The issue of increasing proximity to the nerve without causing injury has been considered the backbone of much research into anesthesia and neurologic injury, but alternative approaches, such as maintaining distance from the nerve but still ensuring sufficient diffusion of anesthetic, should be explored.
“Can we step back and find an approach that doesn’t require the needle to be in contact with the nerve at all?” Dr. Kirkham asked. “The accuracy of ultrasound is such that it can only show you so much. We don’t know the boundaries of the nerve in many cases.”
Some practices relating to current flow and twitch provide clues to avoiding nerve injury, but these guidelines are certainly not foolproof, said Paul McHardy, MD, FRCPC, an anesthesiologist at Sunnybrook Health Sciences Centre, in Toronto.
“We have discovered that a lot of studies have shown you can be touching the nerve and have high current and not get a twitch,” Dr. McHardy said. “At the same time, you can be outside the nerve, have low current and have a twitch. The architectural structure of the nerves behaves differently in terms of risk.”
Using pressure as a measurement is a reliable way to minimize the risk for neurologic injury. “If there are pressures of more than 20 psi [pounds per square inch], then you know you are in a danger zone, and there is a high risk for nerve injury,” Dr. McHardy stated. “If pressure measures less than 15 psi, then you are in a safer zone.”
One animal study (Reg Anesth Pain Med 2004;29:417-423) demonstrated that high injection pressures may suggest intraneural needle placement and result in persistent neurologic deficits, leading the authors to recommend against excessive injection pressure.
Xavier Sala-Blanch, MD, an anesthesiologist and director of the Orthopedic Anesthesia Section, University of Barcelona, in Spain, pointed to retrospective research (Reg Anesth Pain Med2013;38:289-297) that concluded ultrasound guidance can decrease the risk for local anesthetic systemic toxicity, which can be life-threatening, after peripheral nerve blockade. “It is important that we try to reduce the percentage of injury,” Dr. Sala-Blanch said. “Ultrasound helps us to do this.”
Thomas Grau, MD, PhD, MA, professor and chair of the Department of Anesthesiology, Intensive Care Emergency Medicine and Pain Medicine, Klinikum Gutersloh GmbH, in Gutersloh, Germany, said communication with patients preoperatively should take place to ensure that they have consented to the type of anesthesia that is administered and they understand associated risks. “The patient has the right to discuss different modes of anesthesia,” Dr. Grau stated in an interview.