Background: Local anaesthetics (LA) are commonly used by surgeons. Our aim was to assess the knowledge of surgery residents (SR) concerning LA use, and to teach them how to calculate the maximum recommended doses of LA with a nomogram (figure) as a way to reduce the risk of LA toxicity and thus improve patient safety.

Methods: We developed a nomogram to calculate maximum doses (mg/kg and ml/kg) of LA (lidocaine, mepivacaine, bupivacaine, chirocane and articaine) based on ideal body weight. We performed a survey based on a questionnaire proposed to SR who use LA regularly. We assessed rate of use, knowledge on maximum doses, clinical signs toxicity and immediate management. Finally, we asked SR to calculate the maximum dose of 2 LA (lidocaine & bupivacaine) using their prior knowledge and using the nomogram. We analyse data using X2, p<0.05 was considered significant. 

Results: 40/40 distributed questionnaires were collected. SR ranked their knowledge on LA with a 3.0±0.7 3[1-5] on a Likert Scale. 34/40 used LA more than once week and 13/40 daily, mainly in the emergency department (23/40); 34/40 did not monitor patients and 6/40 used pulse-oximetry or EKG. 25 used mepivacaine, 6 articaine, 5 bupivacaine, 4 lidocaine but none chirocane. 39/40 knew that a maximum dose existed, however 28/40 didn´t knew it for lidocaine and/or bupivacaine. 30/40 identify metallic taste as a first symptom, however only 18/40 properly new the clinical setting. 2/40 had seen LA intoxication before and 34/40 knew whom to call in case of one. Concerning what they considered the specific treatment 12/40 knew about intralipid®, but: 8 answered oxygen, 6 naloxone and 9 didn´t answer. When asked to calculate the maximum dose for a 70kg patient, 4/80 doses were calculated correctly without nomogram, which increased to 65/80 at the first attempt using the nomogram, p<0.00, RR 0.06 (0,02-0,16).

Conclusions: As anaesthesiologists, it is our duty to educate on medication safety, especially when it is been use in areas outside the operating room and with little to no monitoring. The nomogram we developed improved the LA dose calculation, and is now on every SR´s pocket in our hospital.

Improving safety on the usage of local anaesthetics among surgery residents in a tertiary university hospital