Ultrasound improves anaesthetic accuracy

Using ultrasound to guide the placement of peripheral nerve blocks improves the accuracy of correct anesthetic spread, leading to improved pain control, reduction in nausea and vomiting in patients and decreased negative outcomes like convulsions and cardiac arrest.

Peripheral nerve blocks refer to the injection of local anesthetic onto or near nerves for temporary control of pain. Nerve blocks relieve pain by interrupting how pain signals are sent to the brain.

Published in the July issue of Regional Anesthesia and Pain Medicine, the Sunnybrook study assessed whether 20 participants using ultrasound could accurately identify tissue spread of small volumes of local anesthetic. Recognizing local anesthetic spread as it is injected around a target structure is critically important as it provides both visual confirmation of the correct spread of local anesthetic and also provides the ability to reduce the volume of anesthetic used.

Using a gelatin model, the participants placed a nerve block needle in the model of a nerve block, with raisins acting as target structures. The accuracy of the test was found to be greater than 90 per cent in the users.

"We learned that with ultrasound it is easy to determine that local anesthetic spread is occurring in the correct place during a nerve block," says Dr. Colin McCartney, principal investigator and anesthesiologist at Sunnybrook.

"This is tremendously important as failure to ensure the correct spread can lead to intravenous injection of local anesthetic with convulsions and cardiac arrest in patients."

The study may impact the training of future novice anesthesiologists before they attempt ultrasound-guided regional anesthesia in patients.

"This study may also increase awareness around the fact that ultrasound-guided anesthetic techniques increase safety, in addition to the already demonstrated advantages of reduced nausea and faster discharge from the hospital after surgery," adds McCartney.