Association Between Smoking and Duration of Regional Anesthesia – A Propensity Score Matching Study

Background Previous studies have shown shorter duration of general anesthesia in smokers but it is unclear in regional anesthesia among smokers. We investigated the association between smoking status and the duration of regional anesthesia. Methods A total of 77 patients with a mean age of 47.3 years who underwent lower extremity orthopaedic surgery under regional anesthesia between January 2021 and June 2022 were enrolled. Sixteen patients were smokers and 57 patients were non-smokers. Propensity score matching was performed to balance patient characteristics. Our primary outcome was the time to onset of motor or sensory blockade and the duration required for full recovery of motor or sensory function. Results The time to sensory loss was 43.4 (SD 35.9) minutes in the smoking group and 39.6 (SD 31.7) minutes in the non-smoking group (p = 0.69), and the time to motor blockade was 37.0 (SD 28.4) minutes in the smoking group and 30.1 (SD 24.1) minutes in the non-smoking group (p = 0.35). The time for recovery of sensory function was 1146.7 (SD 197.8) minutes in the smoking group and 1024.6 (SD 177.9) minutes in the non-smoking group (p = 0.024). The time to recovery of motor function was 978.3 (SD 220.5) minutes in the smoking group and 1090.9 (SD 222.8) minutes in the non-smoking group (p = 0.08). The duration of sensory effect was significantly longer in the smoking group than in the non-smoking group. Conclusions We found no significant association in the onset of regional anesthesia, but the duration of sensory blockade was significantly longer in the smoking group than in the non-smoking group. Hence, attention should be paid to the risks of the insensate limb in smokers due to prolonged sensory blockade as compared to non-smokers, rather than be concerned about delays in the onset of anesthesia.